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LifeProTips
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You can also try a liquid treatment I usually don't recommend bait stations where you are seeing roaches. Bait is to draw them out, a liquid treatment will kill on contact and keep them out. There are plenty of products safe for animals look for one that is a synthetic derivative of a flower (I can't for the life of me remember the name of it). But the toxicity is less then that of salt in mice testing, and most liquid treatments dry in 15 mins.
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LifeProTips
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As far as home remedies go there are the electric zapper things, and I've heard of lavender spray as well as citronella, but in the industry they set up what is called a vapor barrier. They are very expensive however and need reapplication every month so I cant reccomend it. Using repelents and making sure that your house is sealed will help. The true way to get rid of mosquitos is to drain standing water in the area, so maybe you could petion your local goverment to do somthing about it. With mosquitos being airbourne it is hard to find somthing that will actually kill them without cutting of thier reproduction cycle by draining standing water. Hope that is helpful.
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LifeProTips
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Thank you for responding! I googled a couple of photos, and I'm fairly certain they are German roaches, not American. They are small, and not as dark. I will pm you a pic the next time I see one!
There are definitely American roaches out there, too, but I always thought they were palmetto bugs. I'm not so worried about those getting inside, even though they do creep me out.
I will try out the alpine as a precaution. The thought of them infesting my house just terrifies me.
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LifeProTips
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Love the site. About 2 years ago I purchased some termicide to get rid of my ant problem. It used to be that I had to scrub the entire house down because 1 tiny crumb and the colony invades. One time I had baked an apple pie and left it on the counter to cool while I quickly ran to the grocery store. I came home to a completely blacked out pie. It was so disgustingly disturbing. Anyways I googled solutions and came across the site. After just a few weeks of using the stuff on the perimeter of the house and no more ants. I can actually now leave food out on the countertop without worrying about ants.
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LifeProTips
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American Roaches do not typically infest, so it should not be of much concern, most likely a lost little baby, but it can be an indicator that there is something about your house like the humidity or temp. or other enviromental factors that may attract german roaches. For the most part it isnt something to worry too much on but I would still do a barrier treatment on the exterior just to be sure.
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LifeProTips
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I'm a female living in Wisconsin. I get asked a lot why I'm not drinking. Now I'm getting past childbearing years, people assume I'm an alcoholic and judge them for drinking (nope, and nope), or the DD (maybe, but not too often). I just don't take chances with driving under the influence and/or I just don't feel like it. I actually like water because I can drink as much as I need to quench my thirst and only have to deal with a full bladder.
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LifeProTips
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I'm Irish and I don't drink.
People make a *big* deal about it sometimes. Went on holidays to Japan with 3 others friends and a lovely local American offered to buy us all drinks.
Cue "I don't drink" "Me neither" "Nope" "Sorry".
When he asked why, we mentioned that was why we could afford to travel to Japan. We save so much money. It's not the only reason but it's a big one.
Americans seem to make a big deal over it, while most others are just surprised. Had an Uber driver in Atlanta go speechless. He spent about a minute trying to make a sentence before just saying "I need to tell my friends".
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LifeProTips
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I’m not quite 30 but dealing with the same situation. Just so you know you aren’t alone! People say some of the most inappropriate and awkward things to me about my personal habits trying to deduce the reason for my infertility or lack of children. I now plan on asking if they would like to set up a webcam in my bedroom to determine what I’m doing wrong. It’s painful to have to explain it all the time so I’m planning on making them feel as uncomfortable as I do when these questions come up.
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LifeProTips
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I dunno about that.
Depending on the extras, the salesman might stand to make as much money off 2k in extras as they would make on a 30k base car. If you are getting a good price, the salesman might only make 300 off the sale...throwing in some overpriced high margin extras could quickly inflate their total commission.
I think the key to OP's technique is convincing the sales people that you are an easy sale. Essentially you are saying "Look, you're not going to make a lot of money off me, but if you are willing to accept that, I'll come in, sign the papers, and be out of your hair." You aren't someone who they are going to have to take on test drives, spend time explaining features to, etc... If they can earn a 250 commission off you in 45 minutes of work (plus an email response), they are better off than maybe earning 300 on a walk-in who spends 2-3 hours.
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LifeProTips
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I was in the dealership for 30 mins, I went on the Bmw website chose which model, colour etc and went into the dealership. He said the glass was £800 and the climate control instead of ac was £999 or close, I said 30k was my limit so I’d have to look elsewhere if they couldn’t drop those. Maybe over at Audi I’d get the same specs but cheaper. He went and was back 3 mins later with it all rubber stamped. I had a budget I needed to stick to, so I did. I’m sure the guy made his 10% or whatever they get. Still not bad for half hour. I did have to wait 3 months for the car to be built though.
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LifeProTips
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$300 on a sale? Pfft I wish. In the age of the internet, a salesman is lucky to sell a car over invoice. Salesmen make their money on Gross, aka profit over invoice. Nowadays you can go online and find a very close estimate of the invoice price for just about any new car. Therefore, Internet departments at dealerships have to price their cars bottom dollar online cause that's what everyone else is doing. By not doing so, they're not competitive.
Therefore, the salesman almost always takes a "mini" aka minimum commission deal. It usually runs in the neighborhood of $100-150.
Where the salesman make their money is quantity. Usually there's a monthly sales goal. Sell 10 cars and get a bonus of $500. 15 is $1000, 20 is $2000...
As a salesman, I didn't give a fuck how much gross I made on the deal. I was getting $100 for it either way. Internet department dun gave that shit away before my customer even stepped through the door anyways. I twisted my manager's balls on my customer's behalf if I knew it would get me the deal.
The dealership makes their money in the finance office. They sell warranties, service plans and sell people on higher interest rates.
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LifeProTips
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I still don't think you're refuting what I'm saying. To further delve into my previous example:
I am 25, I have been working since 18. I have two jobs, and I average about 55 hours a week. Last year the wife and I made about $40k combined. Due to going on deployment, our income will be closer to double that much this year. Even if I stayed on back-to-back deployments for the next 5 years, we wouldn't reliably be able to amount even $15k in savings without spending it immediately upon amassing it.
We currently rent in the hood, south of a large metro city, and we have to move out because we have had neighbors shot, neighbor children killed, and shots fired within 30ft of our house. We have one 2007 van that will need repairs soon. Our debt is small right now, but it is growing.
I have a life, I want my kids to have a life, and money isn't that important. People shouldn't wait until they're 40 to buy something they want.
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LifeProTips
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Dude what the hell. 55 hrs / wk to earn a portion of 40k? 40k combined income doubled but still no room for saving? These numbers don't say "saving is impossible". They say something is wrong with your job or spending.
Also, yeah you should have a life. And your kids should have a life. But you cant afford that right now man. Money is important if you want those things. Find a change or location or job or something. Something ain't right here.
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LifeProTips
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I make a lot more money on deployment, but I can only go on so many and keep my family happy. If I told my wife that I was volunteering for another back-to-back 1 year deployment after this one, she would most likely leave me.
My comment isn't really about military life, moreso that while on deployment I make good money, but even if I stayed away from home for many years doinf it I couldn't save the kind of money being talked about. When I get back home, I'm going to take my wife and kids on a vacation somewhere, because a deployed dad is just as hard on then as it is for me. Money isn't as important as living your life.
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LifeProTips
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also people need to remember that the client dictates what we can pay, what they want, etc. There were times I would send over outstanding candidates to a client and they would reject them every time. There are times where the client has no clue what they want. Another time a client I placed SEVERAL candidates with decided that didnt' want to pay more than 35k/yr for a Computer Sci grad. I told them QuikTrip started out their cashiers at more than that, which of course they didn't like and I never heard from again, but good f'n riddance.
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LifeProTips
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I'm an electrical field engineer with 15+ years experience. I once got contacted by a very apologetic recruiter who was searching for anFSE for a client that did not understand how much money you have to pay for a fresh faced FSE, let alone one that could do the work they wanted right out the gate. She asked what my price to consider jumping to a new position was, and I told her minimum $85k base before incentives. She took my input to the client, but warned me it was probably a nonstarter.
Her client wanted to pay around $40k tops, but wanted to stay in the $36k range. I was the third candidate with all the check marks they wanted who gave them a price tag of $80k or more, and they just wouldn't play ball. I felt bad for the poor recruiter. That client sounded like a pain.
My resume is stacked with household name, large reputation companies, the kind that tells a recruiter from a mile off that I have a higher price tag. These days my minimum to jump ship is 6 figures and the recruiters that call me are usually ready to play ball with clients that scale accordingly.
I still think back on that poor lady though. I doubt she managed to reconcile that placement and it sounded like a hot fill.
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LifeProTips
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Venues that force beginning bands to sell tickets are con artists at best and downright criminals at worst. I've had the opinion that the practice should be illegal for a long time. It robs young musicians of their money and confidence and those who keep up that practice are the scum of the earth. better LPT: If you see a band selling their own tickets HELP THEM REALIZE THEY ARE BEING ROBBED BLIND!!!
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LifeProTips
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I couldn't agree more. I manage a bar/music venue in my city and am in a band (along with everyone employed here) and that was the first thing we axed when I got the job. No ticket sales and never charging a band for playing a show with a dead turnout. From the door we take the cost of paying our door security (in my state if you are charging a cover you have to have a licensed security guard at the door collecting) which is usually $40-$80 depending on how long the sets are. The rest of the money collected goes to the bands. The main problem we run into is that if it's dead and don't clear that than we eat the cost but the bands don't get any money. They are never charged to play a show, ever, nor should they be. We print all the flyers ourselves and put alot of unpaid hours into promotion to help but sometimes it just doesn't work out and few things suck more than telling touring bands that you're sorry but there isn't any money. We usually buy a two pizzas for the bands, one with toppings and one vegan, and try to give them a place to stay for the night.
A lot of the money bands are making on the road are from merch sales. Buying a shirt from a band costs you $10-$20 but that gets them to the next city, food in their stomach or most importantly hope that they aren't wasting their time and money chasing their dream. Running a venue is way harder than most people could ever know but it doesn't compare to being a touring unknown band.
A message to bands: Never, ever, ever pay a single dollar out of your pocket to play your music. You might not make a ton of money but you damn well shouldn't ever have to pay money.
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LifeProTips
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there's a hierarchy for this kinda thing:
Band -> producer -> venue manager/operator
​
Now, what the producer is **supposed** to do is research and group together like-bands that have a decent following and put them together under an event.
This includes:
* Listening to demos
* googling the bands and trying to search up their fan base and see what their following is
* calculating the turnout liability of each band submitting and letting them know whether they are willing to take the risk or not.
From there, the producer's job is to advertise and push ads, fliers and what have you **locally** (not on their barely known, barely visited Facebook page only followed by other bands and their families/friends) to the areas where the bands are from and where the venue is popular so that when the event comes, a decent turn-out is had and money made.
​
If they do so successfully, they take a **small** percentage cut after the venue is paid for personal profit (it's a job, not a career) and the rest is divvied to the bands. If they don't and there's zero turnout, they apologize to the bands, the bands get SOME kind of compensation, the producer covers cost of the venue and they don't do so poorly next time.
​
What **is** happening nowadays is the "producer" just groups together oftentimes unknown, young bands, sets the venue date up on a dead night (usually Monday through Thursday) and promptly pushes all of their work off on them (fliers, tickets, ads, outreach etc.), promising to pay them a dollar or two for every ticket sold. (tickets are $10 usually too) and then the difference is given to the "producer" Sometimes as well, they'll contractually lock the band into a set number of tickets and hold them liable for money lost if they don't sell them all. (that particular practice is super scummy)
​
so what ends up happening is that these young musicians go to their friends and family because they haven't developed a following or haven't practiced their stuff enough and sell to them. Getting all this cash that they then fork over to the "producer" in exchange for 1/10 of the profit. The "producer" happily takes all of this cash and makes sure to diligently post their little Facebook flier so they can claim they were "reaching out to their base of followers" (which is really just other local bands usually being nice and following) and don't do anything outside of that. These people usually have ties to their venue because they keep the venue nice and paid up because the young musicians are paying everything.
​
In the end, the young musicians run out of friends/family willing to come because it's damned expensive. The musicians can't get the tickets sold because all they've been doing is playing to the same people over and over. Their return for the tickets is crap so they can't get new gear, maintain old gear, record demos, nothing and eventually they burn out and give up thinking it's their fault instead of the fucking con artist's as the producer will often site bullshit like:
* If you can't sell tickets, you're just not ready to play
* The venue and producer are super busy and can't take the time to advertise every event/band (literally the god damned job of the producer)
* Exposure is invaluable (this one makes me particularly angry as young musicians can not pay for gear, food, gas and demos with fucking exposure)
* I've been in this business for n years so this is just how it works
It is the musicians' job to do MUSIC. It is in. the. god. damned. name. of. the. occupation. NOT to produce their show, it is criminally destructive and a morally bankrupt practice that just takes advantage of otherwise talented youth.
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LifeProTips
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Hey I got a question for y'all, instead of playing a club or something, eh... well say you lived in a place with alot of open space, and no noise ordinances, and all you gotta do is tell people who might be interested where the show is. I mean... I dunno I'm thinking out loud. Can somebody help me with this? (also I'm not currently in a band, but it would be useful to know for the future if thats a good idea or not)
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LifeProTips
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Idk where you are but I've been to a ton of basement/house/farm/warehouse shows. If you can get a couple generators or string along a bunch of extension cords going than a show can be literally anywhere. For basement and house shows the cops have shown up but usually it's just a "shut it down" situation. If you have a place for bands to play then usually finding bands to play there is easier than you might think.
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LifeProTips
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When it comes up in a court of law your system's log files will be subpoenaed to verify the audit trail of actions taken on and around that date. If you are being honest then the meta data and system logs will corroborate your story. Unless you are doing kernel level hacking to obfuscate what was done, any edits will show in the system log, and if you are hacking your kernel then the investigating techs will likely find evidence of it. Screenshots are very viable as evidence.
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LifeProTips
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Angry ? No, people must suffer again for strong stoic men to be crafted again.
Little hitler? I see 2 connections there for you are hitler. Yeah makes sense, but critical thinking i do not expect here
Pissy? Opposite, i am having fun.
Keep taking that blue pill while your culture and traditions are being destroyed, while the avg man is but 1% of what his ancestors were, this is reality, consume and die like the worthless man you are to your own folk.
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LifeProTips
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It did as a kid, I would feel stupid and embarrassed. Nowadays I just own it. I know I’m weird and I embrace it. My husband loves me and all my quirks so anyone else’s opinion doesn’t really matter. I’m enjoying life to the fullest, sorry I express it loudly. I’ve seen the post about how pot isn’t a drug, but I smoke it for my medical condition so now it’s just laughable to me.
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LifeProTips
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Highly doubtful. Unless you are some huge asshole and I don’t sense that. Mine is a lot older than me, he is beyond that immature stuff. Not every older guy is like him though. Your guy is out there and he’s trying to get to you as fast as he can. Just gotta be patient and enjoy life on your own. It is true that you have to love yourself first.
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LifeProTips
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I was diagnosed a few months ago (27 years old). There are pros and cons. When your brain has enough dopamine to feel “normal” (on medication) I am very chill. I’ll sit down and read, clean do the dishes, or I’ll sit and just watch a movie ( actually watch a movie). When I am not on my meds, I don’t have enough dopamine. So I am more talkative, jokey, and sometimes rude (not to mention I can hardly get basic chores done, I’ll just ignore everything until it’s too much and then spend a day or two cleaning) if I understand right it’s because dopamine is the brains way of motivating and rewarding you for good behaviour. So on my meds, I have the chemical motivation necessary to accomplish basic tasks and not be a jack ass. Off my meds I am silly and more fun because my brain is always seeking a higher level of stimulation than what ever is present. This is why I can hardly do chores, because the part of my brain that should motivate me to get basic mundane stuff done doesn’t work as well. Hence adhd and why meds help. I go from “haha I am gonna say a silly thing! Chores are stupid” to “I could read I guess, oh wait, dishes need to be done.”
Also reading, I couldn’t read. Well I could read, But I couldn’t sustain focus and it would take me a few weeks to read a novel. On my meds I can read a book in a day and a bit if I really power through.
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LifeProTips
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Still, don’t be too hard on yourself. It will all work out. He and I talked a lot before we even met. It was an online relationship for over a year so that gave us a chance to fall in love with each other’s souls truly.
Our relationship is extremely weird and so odd and not everyone can find it the same way. Personality first. If you can make me laugh you’re halfway there. Hot guys are great and lots of fun, but they usually have too big egos. That’s a rare one I’d say to find one with both.
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LifeProTips
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How did national socialists create bad times for germany? It is quite evident that germany was the best place to live pre-war as a germanic person. Sadly england and france pushed for war. ( read up on the justification of the sudetenland,danzig and memel and the countless peace offers by germany, not even talking about the hypocracy of the british and french). What caused bad times for germany was the loss of the war. In your mind not one ideology would be able of creating good times as all have fallen to another country or system at one time.
Allthough i am sure you have done a lot of research, looked at it objectively and have read both the codex fascimo and mein kampf, together with the justifications of war right?
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LifeProTips
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I think it’s a generational thing—people simply weren’t really diagnosed with disorders as frequently when I was younger.
I was also very high functioning—for me, hypomania translates over to extreme drive (I graduated high school a year early, had two jobs, etc.). My parents told me to “get over” the depressive episodes, so it wasn’t until I was on my own and those started showing up physically (extreme fatigue, stomach ulcers, and etc.) that my PCP thought it might be more than a physical problem and regular hormonal ups and downs and I went to see a therapist, then a psychiatrist. It took two years after my first therapy session to get a diagnosis because I wasn’t connecting the two together (I thought the manic side of bipolar disorder was supposed to be “crazy”).
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LifeProTips
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Don't let that stop you.
I had a co-worker a decade ago or so who was a right bitter fuck, commuting TWO HOURS one-way (country roads) for less than $10/hr, and would complain the whole time...
* "So find a new job?" - "There's no jobs where I live"
* "So find a new place to live?" - "I **LIKE** where I live!"
It's like... DUDE.. you're literally wasting 17% of your life commuting, plus the cost of gas, wear and tear... something's gotta give!
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LifeProTips
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Yeah, my company hires a lot of foreigners (it's a lot of language based job, and you just can't find that many people who speak the languages you need willing to do the job in one English speaking country), so they use pretty decent relocation packages to attract people even for the low level shit wage jobs.
Seriously, if you speak any language besides English and you're willing to move, have a look at language based jobs abroad. They are definitely looking if you're willing.
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LifeProTips
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Well it’s fairly easy to get a years working holiday visa here if you want to try it out. Minimum wage is $16.50 an hour (I think) so as long as you are out of the big cities you can live comfortably on a pretty normal job.
For a more permanent approach, depending what your skill set is you can be granted a working visa for 1, 2 or 3 years and then go from there. We have certain desired trades or careers that help you get an easier path into the country.
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LifeProTips
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If you can, do it. My parents offered to pay my way after I graduated college to relocate to another city. I was too scared and I didn't want to burden them either. That decision probably cost me a hundreds of thousands of dollars once you factor in 401k investment.
Just by happenstance I moved to a bigger city and landed a good job in my field. Sad part is I'm 40 and only really started investing. I've been at my job a few years and I'm interviewing for a promotion next week. *crossing fingers*. The sad part is I could have been at this point in my career 12 years ago.
There's nothing saying that you have to stay where you move. It's common for people to move away get some experience that puts them above the rest that lands them a job in their home area.
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LifeProTips
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Yeah. Ours only go up to 5. Most places that go up to 10 consider 9 and 10 to both be acceptable, but you'll get a lower score for a 9 than a 10. I believe the Safeway stores consider 9 and 10 passing for instance.
However, most places that consider the top two scores acceptable also require the stores to get more passing scores. My company shoots for an 80, which means for every 4 or below we get (0%), we need 4 surveys with a score of 5 (100%) to be passing (80%). Back when a 4 or 5 counted, a 5 counted as 100%, a 4 counted as 80%, and everything else counted as 0%, and we needed to get a 90%. Even 4's, which counted, dragged us below passing, just not as much as everything else.
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LifeProTips
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It's a stupid retail thing.
My understanding is that the thinking is that when someone has a bad experience they tell everyone about it. Some of the people they tell will tell other people about it. But, they will only tell other people about their good experience if it's exceptional. So by saying only the 5's count, they're finding the exceptional experiences, supposedly.
They're not wrong. What was the last decent experience you had when it came to something customer service related? Not knock-your-socks-off amazing, but the experience was exactly what you were expecting when you went into the place. Did you tell anyone about it? What was the last terrible experience you had somewhere, and how many people did you tell? When was the last time that everything that the staff could control went right, but there was still a bad experience? Did you complain to your friends and family about the store, or did you tell them how great the staff at the store was, if you told the story at all?
That said, I guarantee you, the people saying that not everyone that says they were highly satisfied on our surveys is doing more than taking the survey to get the free coupon. They aren't sharing their experiences with other people. Don't get me wrong, some of them do, and I can even tell you which of my customers are going out and telling everyone about me, but most of them don't.
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LifeProTips
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My comment was only meant for people who had good experiences but thought that rating 4 stars instead of 5 stars would still be a good rating.
I don't know what happened at your fast food restaurant. I do know that it wouldn't happen at my store. The most we would do is make sure the cashier didn't mention the survey to you if we thought you might not give us a good rating. We're slower than a fast food restaurant and unless you came in extremely frequently, we wouldn't even recognize you to tell the cashier to not mention the survey the next few times.
I'm not saying you're wrong about what happened. But not every place has to be sneaky and underhanded to get good surveys or prevent bad ones.
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LifeProTips
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I mentioned in [another comment](https://old.reddit.com/r/LifeProTips/comments/9jyuzo/lpt_if_you_had_a_good_experience_at_some_business/e6vk7n9/) what I believe the purpose is. I'm not someone behind one of the survey companies, just a retail employee who relies on my name being mentioned in positive surveys to affect my annual review and chances for promotion, so it's just a guess.
The links were merely to show that it's something that surveys do. It's not just one company doing surveys that considers top box an appropriate metric, it's all of them. As an employee, I find top box to be an inane method of figuring out if employees are doing their jobs well or not, and I'm the top positive survey getter in my store's district. Most of the failing scores we get are outside of our control. Either the customer's expectations are wrong, or the company isn't providing us with what we need to succeed (not enough payroll, not enough product, etc).
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LifeProTips
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Just come out of a it support roll that your stats are based around customers satisfaction. Literally told that 5 stars is for when you meet the customers expectations and then go above and beyond helping them. Pain in the ass as it ultimately cost me my job due to not getting the 4 stars into 5 stars.
We would get ratings like *4 stars* - x staff member was clear and precise when helping. Excellent support.
I would be screaming why give 4 stars out of 5 then if it was excellent. God.
But yes that’s why less then 5 is a fail as all those ratings are CS roles where normally the business would expect you to go above and beyond for customers.
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LifeProTips
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But to these places asking you to rate them, 4 stars is the same as 1 or 2 stars. It is dumb and I hated working for places like this, but that's how they function.
If you wanna give someone a 4 Star rating, you may be better off not leaving a rating at all, because you're 4 Star rating can cost them a bonus or even their job.
Note that I'm talking about those cards they leave on the table at a restaurant - not Yelp, Google, etc.
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LifeProTips
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Much later and blah blah, but I tell everyone I personally know about the awesome experience I had with Dylan at( that specific Government Employee Insurance COmpany). I even stopped the call and asked to speak to his supervisor, and after that to his supers super.
I was going through the (ir)regular jump through every hoop by the dmv. DMV was so segmented it was a nightmare getting the info I needed, but the aforementioned company ( at least the representative) was so helpful I didn’t mind too much.
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LifeProTips
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Right. When you have exceptional service you tell people about it.
One of my customers came in a few weeks ago with her teenage son doing some back to school shopping for him (I work in the print center of an office supply store). She comes up to my counter so she can introduce me to him, or him to me. I looked at the kid, 17-years-old or so, and asked him "Does your mom really talk about me enough that she can say 'this is bestem' and you know who I am?" And he tells me that she tells absolutely everyone whenever they need anything that they might be able to get from my store, or any printing at all, that they should come in and see me. I know customers that will follow me if I get transferred to a store 30 minutes away (I have customers that have done that). I expect those customers to give me 5's on surveys. I do big jobs for them, I do them right, I do them quicker than expected, and I steer them in the right direction and help them problem solve before we even get the jobs.
But when all I do is make a half a dozen copies of a 5 page pamphlet, and 2 minutes later while ringing them up I tell them to take the survey and mention that "bestem was amazing" (or awesome or wonderful or whatever positive adjective I choose)... honestly, those people ought to be rating 3's or 4's. In both cases I'm just doing my job, but in the second case I'm not doing anything the customer even finds exceptional. It's just my register patter that gets the surveys.
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askscience
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Question is basically the title plus a little extra. So I've learned in school that if we use a telescope to observe something that's 1 lightyear away, then what we observe is not the thing as it is today but rather how it was 1 year ago. So the farther away the object of observation is, the older the image we observe of it.
 
If this is true, and please correct me if I'm wrong, then given that the universe is 13.8 billion years old and infinitely wide (because it's constantly expanding right?) then what happens if we theoretically try to observe something that's 13.9 billion lightyears away or farther?
 
Since the universe didn't exist before 13.8 billion years ago, there isn't any light that anyone or anything can pick up and observe right? Or is it that we can only possibly see as far as the universe is currently wide, in which case is it really infinite or is it sort of asymptotically infinite? Is it even theoretically possible to build a telescope that could peer across such astronomical distances?
 
And tangentially related this is something that's been on my mind for a while and I'm hoping someone can answer it. Say you teleported to some observatory 200 lightyears away and were able to use a telescope to look back at Earth. Say you could also zoom in enough to see cities. Would you then see the world as it was in the 1800s? Or is this idea itself, barring the obvious outlandish conditions, science fiction?
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askscience
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[Nature Digital Medicine published our study last week, and it is open access](https://www.nature.com/articles/s41746-018-0040-6). This publication had some delay after the [FDA approved the AI-system, called IDx-DR, on April 11 of this year](https://www.fda.gov/newsevents/newsroom/pressannouncements/ucm604357.htm).
After the approval, many physicians, scientists, and patients had questions about the safety of the AI system, its design, the design of the clinical trial, the trial results, as well as what the results mean for people with diabetes, for the healthcare system, and the future of AI in healthcare. Now, we are finally able to discuss these questions, and I thought a reddit AMA is the most appropriate place to do so. While this is a true AMA, I want to focus on the paper and the study. Questions about cost, pricing, market strategy, investing, and the like I consider to not be about the science, and are also under the highest regulatory scrutiny, so those will have to wait until a later AMA.
I am a retinal specialist - a physician who specialized in ophthalmology and then did a fellowship in vitreoretinal surgery - who treats patients with retinal diseases and teaches medical students, residents, and fellows. I am also a machine learning and image analysis expert, with a MS in Computer Science focused on Artificial Intelligence, and a PhD in image analysis - Jan Koenderink was one of my advisors. 1989-1990 I was postdoc in Tokyo, Japan, at the RIKEN neural networks research lab. I was one of the original contributors of ImageJ, a widely used open source image analysis app. I have published over 250 peer reviewed journal papers (h-index 53) on AI, image analysis, and retina, am past Editor of the journals IEEE TMI and IOVS, and editor of Nature Scientific Reports, and have 17 patents and 5 patent applications in this area. I am the Watzke Professor of Ophthalmology and Visual Sciences, Electrical and Computer Engineering and Biomedical Engineering at the University of Iowa, and I am proud to say that my former graduate students are successful in AI all over the world. [More info on me on my faculty page](https://medicine.uiowa.edu/eye/abramoff).
I also am Founder and President of [IDx](https://www.eyediagnosis.net/), the company that sponsored the study we will be discussing and that markets the AI system, and thus have a conflict of interest. FDA and other regulatory agencies - depending on where you are located - regulate what I can and cannot say about the AI system performance, and I will indicate when that is the case. [More info on the AI system, called labelling, here](https://docs.wixstatic.com/ugd/ea14f7_410f793af1504f46a9bf76d20a3b4d02.pdf).
I'll be in and out for a good part of the day, AMA!
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askscience
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So the "visual spectrum" for humans is 700-400 ish nm light. I know certain insects see in the ultraviolet band as well. I would assume some animals see somewhat lower into the infrared. My question is, what makes that narrow portion of thr em spectrum optimal? Is it optimal? Or did it evolve because other life interacted with that band and so early photoreceptors evolved to sense it? Would it be conceivable that some alien species sees in microwaves, for instance and has named small slices of that the way we name colors? So for them our visual spectrum would be lumped in with the "infra red" or "radio" bands?
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askscience
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As infalling gravitational singularities orbit each other faster and faster around a certain point, they produce waves that we've measured: [https://www.youtube.com/watch?v=TWqhUANNFXw](https://www.youtube.com/watch?v=TWqhUANNFXw)
I was wondering what sort of geodesic they form in the microseconds before merger...as the event horizons draw nearer and pull space-time between them...is it a sort of torus, or elongated sphere? What would happen to certain particles, or even photons, trapped between them moving in an insanely fast figure 8; would they be accelerated out in escape velocities just before the merge? Does that generate a sort of 'radio blast' that would follow millions of years after we detected the gravity wave due to redshift?
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askscience
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Speaking from a certain level of layman intuition, I can picture how a single charged particle spiraling around in a cyclotron can emit EM waves [like this](https://imgur.com/3Hc21Lx.gif). What I'm having trouble understanding is the consistency between this wave model, and the discrete nature of photons, specifically in the case of cyclotron radiation.
As I understand it, you could detect individual discrete photon energy packets arriving at a detector at various times from a spiraling (accelerating) charge in a cyclotron. Does this discrete particle aspect indicate that there are instances in time when the accelerating charge is not producing a photon? Or else it seems like it would have to be emitting an infinite amount of photons (and energy) at every moment in time to mirror the continuous nature of the wave-like behavior in the gif?
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askscience
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Actually a Parks and Rec episode got me thinking. The super fit character Chris catches the flu, and claims that due to his low body fat and lean muscle his symptoms are worse than they might be in an average person.
So would physical size have any effect on the likelihood of catching something like the flu or a cold, and have any bearing on either duration or severity? And would there be a difference if the person were obese and sedentary or muscular and fit?
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askscience
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Modern humans have been around for at least 40,000 years (some sources say 300,000), yet the first somewhat advanced civilizations came into existence around 3000 BC. If the humans living 40,000 years ago were just as intelligent as we are now, then why did it take humans at least over 30,000 years to organize societies like the Mesopotamian civilization where they used alphabet, built sophisticated buildings, roads and weaponry. It's kind of strange don't you think?
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askscience
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I understand that the Transit method is the best current way to find exoplanets, but I was just thinking about how a planet like Jupiter takes 12 earth years for one Jupiter year, would that mean that we'd probably be completely unaware of the largest planet in the solar system (and gas giant with the shortest year) even if we've been examining it's star closely for a whole decade?
Following on from that, could that mean that we've got an extremely skewed perception of the makeup extra-solar systems? Maybe systems more like the solar system are common with large planets on the outskirts but we can't really see that with the transit method?
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askscience
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A friend told me the following math problem:
Imagine you are walking to the bus stop. Your current position has a value of 1, the bus stop has a value of 0, and the distance between the two can be represented by a decimal. Before you reach the bus stop you must first reach half way to the bus stop (0.5), and then you must reach half way between that point and the bus stop (0.25), and then you must reach half way between that point and the bus stop (0.125) and so on and so on, I think you get the picture. If you must first pass an infinite number of places before reaching the bus stop, mathematically how do you actually reach it?
​
If you continue this process infinitely, simple math would suggest that you will never reach the bus stop, but we know that we can reach it in a real world example. Is this because as numbers get very small they must approach a finite value?
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askscience
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Hidden variables may not be impossible, but if they require a field that guides particles deterministically, shouldn't we be able to measure our movement through that field (the same way we should have been able to measure our movement through the luminiferous aether, if it existed)? Wouldn't that provide an absolute reference frame? I don't see how pilot wave theory can be made compatible with special relativity. Am I missing something?
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askscience
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As per Physics...The amount of matter and antimatter produced or released after the big bang must be equal, then why is it so rare, and also how do scientists make it in the Large Haldron Collider?
Is it possible that there is a whole another anti-universe or something?Why does it release tremendous amounts of energy when it comes into contact with matter?
and one last thing...If anti-matter can give us tremendous amounts of energy, then matter also should be able to give the same tremendous amounts of energy when it contacts anti-matter in, say, an anti-matter planet or something, right? then that way if we find out a Place made out of anti-matter, then that'd be a great exchange for the aliens living there, and for us to give our normal matter and get some anti-matter, right?
Fuel for us, fuel for them and we weigh not based on the item, but based on the mass. Or is it that matter out of a Diamond would release more energy when contacted with anti-matter than a banana peel? **Just Curious**.
I hope all of it makes sense.
Edit: Now it might make a little more sense(Punctuation xD)
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askscience
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Genetic engineering is now cheap, relatively simple, and pretty reliable - at least when done in a lab setting. Using a tool called CRISPR, researchers can access DNA in live cells, target specific strings of the DNA code to slice out, turn gene expression up or down, or even swap in new DNA. This means we can, theoretically, reverse genetic conditions, modify cell behaviors, and perhaps program the cells to better fight against disease.
If you want an overview on CRISPR and how it works, my university created this animated explainer: [https://youtu.be/iXgU--ugLqY](https://www.youtube.com/watch?v=iXgU--ugLqY)
My lab is using CRISPR to better understand how the genome controls the functions of human immune cells, in health and disease. We hope to use this research to inform future cell-based therapies to fight cancer, infectious disease, and autoimmunity.
If you're deeply interested in CRISPR, you may have heard of our recent work - we discovered a way to make CRISPR more efficient and flexible in re-writing long DNA sequences in human immune cells, without the use of viruses. There are currently FDA approved gene engineered T cell therapies for certain types of cancer. These cells have been generated by using modified viruses to deliver genes into haphazard sites in the T cell genomes. Improved non-viral CRISPR delivery allows us, effectively, to paste long new stretches of DNA sequences into specific sites in the genome, without having to rely viruses that are costly and laborious to employ. We are working to develop non-viral CRISPR-based genome targeting into broadly useful platforms to make better, faster, cheaper engineered T cells for the next generation of immunotherapies.
You can read my university's story about it here: [http://tiny.ucsf.edu/OccPKL](http://tiny.ucsf.edu/OccPKL)
I'm here to talk about all things CRISPR, genetic engineering, immunology, or any other part of my work. I'll start around 2:30pm PT (5:30 PM ET, 22:30 UT), AMA!
EDIT: Hi everyone, I’m logged in and eager to start answering your questions!
EDIT 2: I appreciate all the questions, I enjoyed answering them. I’m signing off now, but am looking forward to seeing how the conversation evolves here. Thanks and goodnight.
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askscience
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A Tale of Two Chlorines
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Can someone please explain why I had a sturdy plastic bucket literally explode into fragments when I mixed 2 different brands of pool chlorine together? I've never seen something explode like that when exposed to open air.
So what I would normally do is mix the chlorine with pool water and then pour everything into the pool, no problem.
One day we switched chlorine brands, so I poured the last little bit of the original chlorine into the bucket (there might have been a little water in the bucket to begin with) and topped up with the new chlorine. I noticed vapor coming off the mixture almost immediately as I started mixing. The reaction started bubbling and boiling and within about 10 seconds, the mixture started putting out a thick yellow cloud. This was when I knew I had to GTFO, mainly to avoid breathing in any of the noxious fumes. I can't quite remember if I was going to call someone or to get water to dilute the mixture.
I turned around and started walking and as I turned a corner about 5 meters away from where the bucket was left standing, I heard an incredibly loud bang and saw pieces of the red bucket fly past me and land in the pool and on the lawn over 10 meters away. There was literally nothing left at ground zero other than a few white stains from the powder. It was a really powerful explosion.
​
This happened quite some years ago when I used to look after the pool at home, so the details may be a bit sketchy. I've always thought about that incident, what if I hadn't moved away? I could have been permanently blinded, or developed some kind of respiratory issue, possibly even hearing damage?
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P.S. the brands were HTH and Clarity in that order (i think)
There was no outside contamination that I know of.
​
Edit: Thanks for the replies and explanations so far. I'm glad I'm not the only one surprised/confused by this. Just a couple things, This *was* a long time ago like I said, so it might not have bubbled for 10 seconds, the gas might have been green instead of yellow, etc. All I know for sure is that it was loud, it started raining red plastic bits, there was definitely no lid on the bucket and that there were 2 brands of chlorine in a bucket.
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askscience
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Its said that the age of the universe is roughly 13.8 billion years old but since all mass has an effect on space time how do we know if thats the true age? Like from the perspective of someone next to a black hole the universe would be younger and someone in intergalactic space older right? Do scientists take this into account when they estimate ages of space objects? And if time doesnt run at exactly the same speed in any two parts of the universe is there any way to know the exact age of anything far away?
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askscience
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I did some work on this back in grad school, outside of stem though. The theory back in the 1990s was that even a limited nuclear war could cause a nuclear winter. I think the problem is how people define "nuclear winter" It is actually a temporary dramatic shift in world climate that will eventually subside, after several years.
https://www.jstor.org/stable/424481
I would love to hear thought from anyone in the field. I have not come across anything to really dispute the above.
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askscience
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While this is slightly off topic, there is evidence that the entire concept of "Nuclear Winter" was a facet in the Soviet propaganda campaign to take advantage of the peace movement in the west. Not that there wasn't a possibility of a cooling event from a large amount of dust thrown into the atmosphere, but that even in the largest nuclear exchange, you are likely orders of magnitude below the energy that would be necessary to cause a large change in atmospheric dust levels.
Leading credence to this was the disappearance of one of the initiators of the theory in 1985, Vladimir Alexandrov. Granted, some of his research went on to aid in our modern understanding of global climate changes.
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askscience
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A lot of it was substantiated by a defected Soviet intelligence officer named Sergei Tretyakov in the 2000s in his book *Comrade J: The Untold Secrets of Russia's Master Spy in America After the End of the Cold War*. TIME magazine was running [articles alluding to](https://web.archive.org/web/20070930040755/http://www.time.com/time/magazine/printout/0,8816,960025,00.html) such things back in the 1980s.
The Sagan stuff was part of the supposed influence that the Soviets had over the, at the time nascent peace movement in the late 1940s and 1950s, from which Sagan came out. From my reading of these events, the idea was to cause a rift between the scientific community and the burgeoning national labs which were focused on nuclear weapons development and required a large deal of cooperation with the physics community to keep the research going.
I came across a lot of this information when I was studying nuclear proliferation and other issues in college. I've thought more about it now, as it shows that there was a historical precedence to the alleged events surrounding the 2016 election.
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askscience
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I did in a separate reply.
There is a lot of circumstantial evidence. However, there is enough to at least see it as a more likely possibility than an actual nuclear winter scenario.
The DoD released a [paper on the subject](http://www.dtic.mil/dtic/tr/fulltext/u2/a200062.pdf) in 1987. A key takeaway in the summery was:
>The nuclear winter hypothesis has attracted increased attention in the scientific community over the past five years. The research has advanced to the state that, in spite of remaining uncertainties, there is a consensus of plausibility for the hypothesis and for the impact such an effect would have on the earth's environment. The validity of this "nonissue" has increased to the point that the emotional aspects of the horrors of a nuclear war are now given additional credence by scientific research. The dilemma of the issue is that the "guidance" offered by scientific information has many interpretations on how best to keep the world safe from nuclear war.
Further, the paper talks about the propaganda value of idea becoming more important than the idea itself; effectively that that discussing the horrors of nuclear war was a method of deterrence and that the more open western media allowed for that to have a greater impact on the populations there than in the Soviet sphere.
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askscience
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The nuclear winter idea in the West clearly originated separate from any serious Soviet influence (it has its own intellectual trajectory), and the work that has been done on it since then has been largely independent of Soviet theories and data (the originators of the theory were appropriately wary of relying on anything coming out the USSR).
Did the Soviets use it as a facet of their propaganda? Sure. They also used Civil Rights as part of their propaganda as well, but that doesn't undermine the reality of it. Both the USA and USSR promoted theories or arguments that promoted their overall diplomatic/ideological goals during the Cold War, often through clandestine sources. One should not confuse promotion with creation, or let it by itself "taint" the underlying work.
You should be aware that the "nuclear winter is Soviet propaganda" argument is itself a holdover of propaganda from people who were resisting the argument that nuclear winter implied that the desired arms build-ups in the 1980s were suicidal. (So you're engaging with another form of propaganda in repeating it, ironically.)
There have been many nuclear winter studies over the last 30 years, by many different groups, using many different models, and many different assumptions. They get different results, like all scientific modeling of complex phenomena. Some suggest nuclear winter effects are likely, some indicate they are not. It may be that everybody involved has some political stake in the results (it's hard not to), but the idea that it's some kind of cheap conspiracy is about as plausible as the similar ideas propagated by climate change denialists. The initial TTAPS work was rather crude compared to the full climate simulations that people (both pro and con) are using today. Science marches on, though the scale of the problem is large enough that total certainty is likely to remain elusive for a long time yet.
For a very good history of nuclear winter by a serious historian of science, see Lawrence Badash, _A Nuclear Winter's Tale_. Please also be aware that former Soviet intelligence agents _love_ to inflate their role in things, and all such accounts need to be read with a grain of salt.
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askscience
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I don't think that's quite true. At the height of the cold war they had tens of thousands of missiles, each carrying multiple warheads. There was a lot more than now. They wouldn't have all reached their targets at the same time instead they would be falling and reinforcing the effects of the warheads detonated earlier. Thus inputting more energy into the dust and ash clouds forming.
It probably would not have frozen Earth solid as claimed by some but global cooling would have been on a level where only the tropical and subtropical locations would have been warm enough to grow crops. And considering how much radiation there would be floating all around I doubt a lot of plant life would survive.
All in all even if they were using the scenario to make more people less willing to use nuclear weapons that is a good thing.
If they were telling people a possible side-effect of the world going to nuclear war. People got scared and wanted the chance of war to be less. That is a good thing.
​
Also all of the things that Tretyakov said are claims by him only. There is no collaboration with any trusted sourced. Considering he worked in the SVR decades after the things he claimed happened I doubt he actually would have gain access to such documents in the first place.
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askscience
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Bearing in mind: there will be nobody to put out the fires! Any fire that exists will die on its own accord, or simply rage and feed into other fires, and there will still be huge landscapes awash in flames, and even when the fires eventually go out, there will be smoke rising from the hot embers for who knows how long. Think of how long the 9/11 WTC site was emitting noxious smoke from beneath the collapsed buildings.
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askscience
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Assume all the major metro areas and industrial centers got nuked.
1. At least a third of the population has just died. Probably about half of the young adult population, conservatively. Populations will decline further in the short term before they can start to recover.
2. The infrastructure and logistics support to distribute food and supplies is probably completely inoperable. You're suck surviving on things that can be produced locally for a long while.
3. The power is probably out. It will probably stay that way because the people that know how to run a large power grid were probably based in a city.
4. Most highly specialized knowledge in general is probably lost within a generation or so, as those types of activities are concentrated in urban areas, and require huge amounts of time to learn (on equipment that was just vaporized), which can't be spared because trying to survive is a full time job.
Worst case scenario, you basically have to redo the entire industrialization process, with the benefit of a few modern tools and some general knowledge about how it turns out.
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askscience
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Take a look at Tsar Bomba, 50mt yield. And that wasn't even enough to cause even local atmospheric pollution or any other sort of long lasting effects that don't include radiation. I would venture a guess that it would take orders of magnitudes more than even 50mt. You're realistically looking at several thousands, if not tens of thousands of megatons in yield to accomplish nuclear winter. I would even venture to guess that there isn't enough nuclear weaponry to accomplish it.
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askscience
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It's been pretty much universally agreed upon in the nuclear community that the intersection of the power curve you're talking about is right around 50mt.
They had originally planned to make it 100mt, but up one calculating it, realized they are wasting a lot of the energy.
https://en.wikipedia.org/wiki/Nuclear_weapon_yield
To date, we've tested almost 51,000mt worth of nuclear devices.
I really think "nuclear winter" is a product of science fiction novels and movies. I don't even think detonating every nuclear device on the planet currently and simultaneously would do the trick either.
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askscience
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> Also the limit of 50mt is the yield above which all you do is send more air into space
It's actually more about the weight to yield ratio and the altitude at which the device will detonate.
All nuclear explosions are spherical and generated above the target. No matter what your yield is, you will always have a spherical detonation that is sending X coefficent downwards (towards target) and Y coefficent upwards (away from target).
For sake of easy math, lets assume it's a 50/50 split. I know it's not, but that's not important to explaining the theory.
Now, there's an ideal altitude at which will take the 50% of that energy traveling outwards and *down towards the target* and distribute it to maximum effect on the target.
Bombs with a yield greater than 50mt require a detonation altitude which is inefficient for damaging targets on the ground. (IE; you have to detonate a 100mt bomb so high that it will achieve the same destruction as a 50mt bomb detonated at a lower altitude)
They will both have the same damage on the target, the only difference being it's much more efficient and cost savings to build a 50mt bomb to do the same thing as a 100mt bomb.
> is send more air into space
That hurts my head just reading. Air doesn't get "sent into space" energy is just directed upwards into the atmosphere where there's no targets and it gets dispersed. This is something that happens with all nuclear devices because of the spherical explosion. It all stays inside the atmosphere.
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askscience
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Well yes, the angle of destructive force will get more acute as the radius increases.
But the shockwave does send a lot of air into space, still inside the upper atmosphere, but I’m considering space to be the point at which the shockwave becomes irrelevant due to the rarity of the air.
Obviously the thermal pulse does too. But I’m getting at the same point as you... most of the energy in the downward and all of the energy in the upward region of the sphere is wasted. The only portion of the blast that is applying its energy usefully is a small ring of the emitted pulse/blast, aiming at the regions where destruction is only moderate. This would obviously get thinner with greater yield as this critical target region got further way
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askscience
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> air into space
dude, you really need to stop saying this. that is not at all what happens. no air "goes into space" that is not possible.
Take a balloon, inflate it half way and seal it. Grab the inflated part of the baloon and start squeezing it. Notice how you just move a pocket of air around *inside the balloon*? That's what happens with a nuclear detonation. It just gets moved around within the atmosphere.
Remember, we're talking about an explosion occurring a mile or less above the surface.
The explosion does not "push air into space" that is still around 65 miles above where the explosion took place.
Please stop saying that. It really makes you sound uneducated.
> Well yes, the angle of destructive force will get more acute as the radius increases.
Exactly. Which should explain to you exactly why it's better to use a 50mt yield that can achieve the same effect as a 100mt yield. There's no reason to build and detonate a 100mt bomb, when a 50mt bomb (does the exact same thing)
I think that's the misconception here. You think that the 100mt bomb *does less damage* than the 50mt bomb, but it's actually *the same damage* which makes the 50mt bomb a more efficient option.
> I’m considering space to be the point at which the shockwave becomes irrelevant due to the rarity of the air.
The shockwave dissipates well before it reaches even halfway to the upper atmosphere. Remember, the upper limit of the atmosphere is still some 60 miles or so ABOVE the explosion.
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askscience
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Yes. They absorb visible light and re-emit the energy as infrared light, which is absorbed by greenhouse gasses. Lightly-colored surfaces, on the other hand, reflect more of the incoming visible light back into space, so that energy doesn't have to find its way through the greenhouse gasses (as they are transparent to visible light).
For this reason, the melting of sea ice creates a feedback loop. Sea water absorbs a great deal of incident light, especially compared to ice. As the ice melts, the Earth absorbs more of the energy from the Sun, which warms the Earth, causing more ice to melt, causing more absorption of energy from the Sun, etc. This is not the only feedback process involved in the climate (some are positive feedback loops while others are negative), but it is an important one. A negative feedback loop that works the same way is that a warmer Earth leads to more water evaporation, which leads to more cloud formation, which leads to more incoming sunlight being reflected away, thus cooling the Earth back down. How strong each of these various feedback loops is is one large source of uncertainty in modelling the future of climate change. (I want to be clear, though, that uncertainty in modelling the future is not the same as uncertainty in what is causing climate change - carbon dioxide originating from human activity is responsible for increased global average temperatures in the last several decades.)
We can see this effect in other planets as well. [Venus reflects an incredible 77% of all the light incident upon it](https://i.redd.it/ugexjlyu2oj11.jpg) (compared to Earth's 30%). Venus actually absorbs less energy from the Sun than Earth does, even though it's closer to the Sun! Yet Venus is hot enough that the first several probes sent there melted. Why? Venus has a thick atmosphere, dozens of times as dense as Earth's, and it's almost all carbon dioxide, so that Venus is extremely inefficient at re-radiating the energy it receives from the Sun. The greenhouse effect is strong enough to turn the 23% of sunlight that isn't reflected by the clouds into a hell-scape.
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askscience
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So, the groups U (n) are called unitary groups. They act on the set of matrices n×n who have their inverse equivalent to their conjugate transpose via matrix multiplication. This is a subgroup of the general linear group so it would act on the same vector space. The group SU (n) is the subgroup of the unitary group whose elements all have determinate 1. So, they are effectively act as linear transformations on a vector space of dimension n.
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askscience
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The vector space it acts on isn't anything other than a space. So, the thing that makes these groups special and useful in physics is that they're Lie Groups and thus are continous in some sense. So, they're generally used to talk about spin and stuff that has continous symmetry, so the best way to think about the vector space the group lives in is the space the particle is experiencing symmetry in. I might be taking for granted that I come from a math background where the use of these things in physics makes sense because I know what they're doing independent of the real world. I apologize if so, I am just hoping I can help a little.
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askscience
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Yeah I know the math behind what SU(3) is, and I was enquiring about the physical context. I appreciate the effort though!
To give an example of what I am asking about. When we consider rotations of the coordinate system, we (physicists) often look at an infinitesimal rotation. Then we notice that there is a "basis" of 3 different way to do this infinitesimal rotation. These obey a specific algebra, and then we identify the rotations with the group SO(3).
But here we had a coordinate system, or a wavefunction on which we could apply a linear transformation. SU(3) is also transformations, but what kinds of objects does it transform, in the context of gauge in the strong interaction?
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askscience
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Basically, yes, it's the wave function. Of course if you do particle physics you should really do quantum field theory and one usually doesn't talk about wave functions, but still operators (now fields) acting on a Hilbert space. The Hilbert space is the vector space you're mentioning, and it is defined by all relevant quantum numbers. So not only space and time coordinates, but also quantum numbers under internal symmetry operations such as electric charge, isospin etc.
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askscience
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Sort of, yes. The space for the strong interactions is called color. The space for the electromagnetic interaction is charge. The space for the the unified electroweak force is is a product space of electroweak isospin (the SU(2) part) and the electroweak hypercharge (the U(1) part) . In general it is the associated charge. https://en.m.wikipedia.org/wiki/Charge_(physics)
The actual colors are arbitrary labels that can’t be fixed unless a symmetry is broken, and even then, only under convention (we call electrons negative charges, arbitrarily)
For the strong force, the colors are not observable— there’s no way to create a fixed source of “Red” charge, so calling them red, green, and blue is an entirely fictitious way of keeping track without enumerating them.
Anti-red is not an additive complement to red, though. Rather, it is the dual representation. The consequence is that there is a sub space of the color-anticolor product space that is invariant under the group transformation — this state corresponds to a neutral combination of color/anti color particles. It’s not red-antired, blue-antiblue, or green-antigreen. It’s a superposition of all of these— a color singlet state. https://en.wikipedia.org/wiki/Gluon#Color_singlet_states
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askscience
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Neither you nor he are factually inaccurate. Starches are not sugars even though they are entirely made of them. Animals are made entirely of elemental compounds, yet they are not classified as such.
/u/yugo_1 is wrong because nobody before your reply commented that starches are counted as sugars. While you are wrong because your question implies that they are. Even the link you posted is careful to talk about sugars, before talking about polysaccharides. They are associated but not the same.
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askscience
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I'm sorry for lack of clarity.
I was trying to say that your characterization doesn't seem accurate.
You told Scbios that they were wrong, because they implied that starches are sugars - I was trying to point out that, at least to me, they did more than just imply it; they specifically said so.
And in that light it doesn't seem strange that yugo_1 would comment on it.
Perhaps I am misunderstanding something.
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askscience
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It depends on what you mean by "amount" and "carbs" 😉
By weight the amount of carbohydrates doesn't change significantly. But the amount of carbohydrate substances increase, since the chemical meaning of the word amount is the number of molecules in this example. And since the starch is long chains of monosaccharides that gets divided into several shorter sugars, the amount increases.
And the use of "carbs" is a bit ambiguous... It's originally a short form of carbohydrates, but is often used as an everyday term for energy content, since carbohydrates are our main source of energy. The amount, by weight, of carbohydrates doesn't change as the longer carbohydrates break down to shorter ones. But if a form of carbohydrate that the human digestive system normally can't digest, for example cellulose, were to be broken down into starch or sugars, which our bodies can make use of, the amount of usable energy could increase.
I don't really know if the latter happens, but it is theoretically possible.
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askscience
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No need to be sorry, I make perfect sense in my own head but it doesn't always come out that way. ; ) Thanks for actually clarifying!
There is nothing factually inaccurate about it though and they aren't saying that starches *are* sugars so much as the sugars within them haven't become *not sugar*. If I place an iron chain in a bucket of water, seal it, and wait for it to rust away, has the iron content of the bucket changed? I'd say that no it has not changed. The amount in solution has changed, but the total amount of iron within the bucket has stayed relatively flat (of course that isn't 100% accurate, but it's close enough for all practical purposes).
In the end it is kind of a Ship of Theseus type of situation I suppose, or it's equally possible I'm misunderstanding something instead.
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askscience
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Agreed. Calling starch "sugar" when discussing the different nutrients in a banana is going to confuse a layman. The point is you will get a higher glycemic response from eating a very ripe banana. Overall, though, unless you have an issue with diabetes, I don't see a huge difference from eating a slightly green banana and a yellow one. Just eat whichever you feel tastes better. If the tastiness of a ripe banana convinces you to eat one every day, that's a good thing. It has lot of potassium, some vitamins, and fiber, and it's much better for you compared to purple drink.
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askscience
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Yes to all of these. In hearing people clanging is words that have similar sounds. In sign language it is signs that have similar movements. They also can have word salad where they just sign a bunch of signs that don’t go together such as “dog day person money”. They have no meaning, just random signs. Deaf person’s signing can be “slurred” especially after things like waking up from anesthesia. Wernicke’s and broca’s area are a language center in the brain, not just a spoken language so yes sign language can be affected by those as well. Another phenomenon is that people who are schizophrenic sometimes will not cross one side of their body. For example some signs move from one side of the body to the other and they will make the movement all on one side of their body. They will never cross the midline. If there is a terminology for this, it’s escaped my mind right now. Deaf people also do have auditory hallucinations (hear voices) as well. This is because auditory hallucinations are from an internal stimuli (in their brain) and not an external stimuli (an actual noise).
Source: am a working sign language interpreter and have a certification in mental health interpreting
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askscience
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So interesting! I figured clanging would still occur, but I was trying to think what that would look like, so thank you for your input. I was assuming it could either be words that look the same on paper that might get signed, but signing words that use similar movements makes much more sense.
If you could elaborate more on people who are deaf having auditory hallucinations I would love to know more.
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askscience
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yes...also occurs in stroke affected patients...they will completely ignore their affected side...to the point of turning their head and looking the opposite way all the time.
..Nurses have to place all items of use i.e.bedside locker, table etc over to the affected side to re-orientate them.They will use a mirror too to help.
I have also seen a meal been eaten completely in half....definite line...and only half the plate of food actually eaten...like the other side simply doesnt exist.
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askscience
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No, like hearing sounds when you're not actually hearing it. I grew up wearing hearing aids but stopped when I developed tinnitus (ironic that you brought that up) but when I see a police car or ambulance go by me, I almost can hear the sirens but I know it's my brain telling me I should be hearing the sirens as they go by and it's being simulated in my head.
The same can be true for me when I read lyrics and I almost can "visualize" the sounds, such as the song being sung, in my head and more.
I have tinnitus whenever I have high blood pressure and it's way different from auditory hallucinations. Tinnitus is like a sound being "repetitive" and drawn out in a monotonous tone, at least for me.
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askscience
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It is called 'Neglect' and as someone else wrote below, it can happen after a stroke.
https://www.psychologytoday.com/us/blog/brain-babble/201208/hemispatial-neglect-one-sided-world
Dr Lisa Geneva, an American scientist who taught Neuroanatomy at Harvard, wrote a (fiction) book from the perspective of someone with this condition. It's called 'Left Neglected'. She wrote 'Still Alice', too, which was really good and got made into a film (the book was written from the perspective of a professor diagnosed with Alzheimer's disease).
If you're interested, it might be worth taking a look! Hope this helps.
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askscience
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I have experience with deafness. One of the things I've learned about deafness, and that you non-deafies should know, is that there is a disconnect between hearing and comprehending what you hear. For my hearing friends, they may not be aware of the processing time to understand the words being said, because you understand sounds better, and you're just so much more skilled at it, it's almost instantaneous. For all practical purposes, words come out of someone's mouth, and go into your ears as words.
However when listening to speech, deafies on the other hand, have to consciously and constantly interpret sounds to words. Just noise comes from people's mouths, and there is extra processing time as we try extrapolating the meaning of this bit of sound, and matching up every other bit of sound to the shapes their mouth is making. Sometimes it's easier than others. Familiar people we usually understand better.
So one day I'm going down the grand canyon. I get a little ways down, and btw I brought no food or water and it's July. So after a while, probably from the exercise in lots of direct sunlight, plus dehydration, I start hearing things. It was very dim at first, like background noise. But as I continued I finally noticed it, and it sounds like voices. I try to pay attention to these voices but nope I couldn't tell what they were saying at all. Shouldn't you be able to understand voices in your own head? I puzzled on that question the rest of my time in the grand canyon (all day long).
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askscience
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That’s really interesting and I’ve never really thought about it. Yes, voices can be heard by people who were born Deaf. In fact, all of the people I have worked with that had auditory hallucinations were born Deaf, but that’s not to say it’s always that way. All I know, is they are able to understand that it is a voice and they are able to tell me what the voices are saying to them. The hallucinations are internal but if they have never heard spoken language, I’m not sure how they are able to identify the words being said. Except that most Deaf people have some experiences with speech therapy so they have familiarity with how words are supposed to sound. Ive always thought it must be really scary for a Deaf person to have auditory hallucinations even more so than it would be for a hearing person. Hearing people can hear other sounds as well and a coping skill typically used is other sounds to try and drown out the voices. Deaf people have no way of doing that and the only sounds they can hear (if they are profoundly Deaf), are the voices.
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askscience
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>Deaf people also do have auditory hallucinations (hear voices) as well. This is because auditory hallucinations are from an internal stimuli (in their brain) and not an external stimuli (an actual noise).
It seems that this is not the case for all deaf people - especially given the fact that if you were born deaf, you never developed the neural connections to experience sound. Anyone who is not fully deaf or had hearing earlier, though, could have true auditory hallucinations. [Here's](https://mosaicscience.com/story/can-deaf-people-hear-voices/) one article I found which is summarizing some research. Relevant excerpt:
> “Deaf people who had never heard did not experience true auditory hallucinations,” says Joanna. For this group, communication came via the mind’s eye: visual hallucinations of moving lips, or disembodied hands and arms making sign language movements.
I decided to comment to clear this up because some people might get the impression from your comment that people who were born deaf and have never ever heard anything could still hear but only via hallucinations, and this is not the case.
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askscience
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If they're profoundly deaf from birth then no. OP's comment was not fully clear - auditory hallucinations are only possible in deaf people that have heard before. Lots of deaf people actually just have really, really weak hearing, like how a lot of blind people can still sense some light or shapes. So even if you are deaf from birth, in that your hearing is practically useless, it's possible to still be able to hear really loud noises. You'd have to be 100% deaf from birth to have no chance of audio hallucinations.
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askscience
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That cannot be right though. According to the equivalence principle, all charges should fall at the same rate independently of their charge.
This is actually a rather subtle question, because we have to consider observers that are not inertial with respect to one another. In the rest frame of the charge free falling, there obviously is no radiation emitted. On the other hand, we can think of an observer "at rest" with respect to the source of the gravitational field, say for instance an observer standing on the ground on Earth, is recording the charge accelerate as it falls, and therefore should record radiation emitted which objectively carries energy. That means that the energy transported by the radiation is actually created by the (non inertial) change of referential. And that also implies that energy is not locally conserved when doing referential changes in the presence of a gravitational field, energy in this context is only conserved globally.
Honestly none of this is easy conceptually, not to mention actually doing the calculation. I think the initial answer sort of brushed off a valid question. It is irrelevant whether gravitons exists or not, the question still stands, there is a mathematical formalism to perform the calculation, and even worse, the same question applies without invoking gravitons, just about the acceleration of a charged mass.
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askscience
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This is a shockingly unsettled question in the literature. I was looking into it recently and there are 4 cases to consider:
Free falling charge and free falling observer: no radiation, everyone agrees, just due to the EP
Supported charge and free falling observer: radiation, everyone agrees, due to EP
Supported charge and supported observer: no radiation, everyone agrees, but the technical account is that the charge *is* radiating, but only into an area behind the observer's Rindler horizon
Free falling charge and supported observer: unclear. The classic Rohrlich paper/wikipedia/various SE posts all say yes, it does radiate, see also https://arxiv.org/abs/gr-qc/0006037
but other papers say no, eg:
https://arxiv.org/abs/gr-qc/9405050
https://arxiv.org/abs/physics/0506049
https://arxiv.org/abs/physics/9910019
https://arxiv.org/abs/1509.08757
Personally, I don't understand how it can be yes. The EP says free fall is not a state of proper acceleration, so there can't be radiation, and this has to be an observer independent fact.
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askscience
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You can actually see further than 13.8 billion light years because the universe is expanding. Light travels at the speed of light, which is one light year per year. So the furthest distance that light can travel in the history of the universe is 13.8 billion light years. But in 13.8 billion years, the universe has expanded a lot. The object that the light came from can be more than 13.8 billion light years away. So we can see objects that are now further than 13.8 billion light years away. Taking this into account, the furthest object you can possibly see is about about 50 billion light years away.
In practice though, the universe was opaque in very early times, so when we look at very large distances we just see a uniform "wall". This is the cosmic microwave background. Note that you don't need an exceptionally good telescope to see that far - the limiting factor in telescopes is more about brightness than resolution, and this background is fairly bright.
And yes, if you were sitting at a star 200 light years away, you could see Earth as it was 200 years ago, although you'd need a very very good telescope to get enough resolution.
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askscience
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Think of it like this: Hold a ball at arm's length away from you and take a picture of it. Hold that picture at the same distance. That picture is the light waves coming towards us.
Now pull the picture to your face and roll the ball away from you. You're seeing an image of the ball where it was at first - But we can agree that the ball is now further away from us, right? So we're looking at an object "father than the speed of light."
... or, that's my understanding of it. If I'm wrong, feel free to correct me.
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askscience
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Its kinda like stretching an elastic band.. Put 2 dots, and have a snail crawl from 1 to the other.. If you stretch the elastic in the right way, you can make the snail much quicker from point a to point b then what it normally would.
Yes, light can only go the speed of light in this universe, but if the universe itself is growing, the relative speed of the light will be faster then intuitively possible, much like the snail on the elastic band.
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askscience
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The universe appears to be infinite. The Big Bang wasn't an explosion where everything started in one place and started moving away from each other at some speed. Instead, it was an early state of the universe where everything was very dense and uniform, but the universe was still infinite in size. Then everything expanded in all directions at the same time, with everything getting further away from everything else, and the universe got less and less dense over time.
It may be helpful to think of the expansion of the universe as "everything getting less dense" rather than "the universe getting bigger", because it's hard to imagine an infinite universe "getting bigger".
But yeah, things can be any distance away at all. We just can't see them unless they're close enough for their light to reach us.
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askscience
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In nutshell:
The universe's "expanding" basically means that more and more space appears between any two points, bringing them farther away. This "more space" appear slowly, but constantly. The longer the distance, there is more space appearing, bringing them farther away, "stretching out" the universe.
Now imagine a star which was at 1 billion light years away from us (don't forget: a light year is a distance: the distance which a photon cover during one Earth-year). The photon left the star and started to travel to us. If the universe wouldn't expand then it would arrive at our eyes 1 billion years later. However, the universe is expanding: at each time unit, the photon has to travel a little more as more and more space appearing between us and the photon. At distance big enough between us and the distant object this effect creates more than 1 light year worth of space between us and the photon trying to reach us: this means that this photon can never reach us. This basically creates an event horizon: a "bubble" where no outside information can ever reach us.
So, nothing travels faster than the speed of light, yet object is getting away from us faster than the speed of light. The most distant object what we saw (the light basically emitted not a long after the Big bang itself) is very, very, very far away from us now, as more and more space is appearing between us and this light emitting object.
This is how possible that the photon was emitted 13.8 billion years ago, yet the object which emitted it is now 50 billion light years away from us.
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askscience
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You'd need a very good telescope indeed--and a very large one.
At 200 lightyears, being able to resolve objects spaced even a meter apart would require a resolution of about 1.09×10^(-13) arcseconds. Using diffraction-limited optics, your superscope will need a primary mirror at least 91.7 million kilometers across. Or 9.17 *billion* kilometers across, if you want one-centimeter resolution. Ten kilometer resolution, enough to see cities, would only require a 9,170 kilometer mirror.
Still, you should go ahead and spring for the heavy-duty tripod though.
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askscience
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The universe is expanding at a constant speed (67km per 1m parsecs), it's the observer who percieves it as faster than light because the farthest objects seem to be moving away faster. They are not, but it seems that way to us.
Imagine firemen holding a blanket and every fireman backing away at the same pace. To each fireman it would seem his speed to be relative to his neighbor's speed. To someone in the middle, everyone would be moving away at the same speed. But if you were to place a small ball on the blanket between the observer and the firemen the ball would appear to be moving away slower than the firemen, even though the blanket ensures that the speed is constant. Special relativity tells us that nothing can move faster than light, but general relativity tells us that since the blanket is stretching it doesn't matter what the speed of light is.
And I just made a simple concept seem even more complicated. Sorry.
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askscience
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Let's say that there was a massive telescope that would let you zoom at a 1800's town and it's people - how is it possible that you would see people walking and doing their chores, considering that a person reflects a limited amount of photons and each goes in a different direction - which at a massive distance means that they are spreading to different regions of the universe?
In fact, shouldn't that be a factor also when looking at big objects billions of light-years away? Even with a couple of lenses side by side.
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askscience
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The universe is indeed expanding faster than the speed of light.
The light from the most distant objects we can see has only been traveling for about 14 billion years (lookback distance) but we figure the most distant objects we can see are actually about 45 billion light years away (comoving distance), because all the space in between has been expanding in the meantime. Since the universe is expanding everywhere all at once, a large portion of what we can see is already receding faster than light. At some point in time, we will never receive light from those objects ever again.
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askscience
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It's counter-intuitive, but the definition of "brightness" that matters here does not actually go down with distance. The amount of flux you get *per square degree of view* is constant, excluding stuff like dust in the way etc. That's way a wall doesn't get hugely bright when you place your eyes against it.
So yeah, the *total* flux you get from an object decreases as 1/distance^(2). But if it's a resolved object, that emission is spread out of some number of square degrees of sky. If the object is 2x closer, then you get 4x as much flux, but it's also spread out over 4x as much of the sky, so the actual brightness in terms of flux per square degree of sky is constant. And that definition of brightness is actually the natural one that we use to say how bright something is - for the reason I stated above, that using the total flux means that a wall gets "brighter" if you are closer to it, which isn't the case.
However, this is only for the peak brightness you can get with a telescope. The brightness you see through a telescope depends on the magnification, provided you want your image to be in focus. There is a peak brightness you can see at a certain level of magnification, and the bigger the telescope, the higher magnification you can get at this peak brightness. So you do want to have a big telescope, to make sure you can get enough magnification without making the image really dim, but also to make sure you have enough resolution to actually see anything. Of course you can just take a really long image if it's too dim, although you won't see much detail if you're trying to photograph individual people.
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