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askscience
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Thanks for the reply, but my question was probably more basic or dumb than you realized. I meant that if a surface reflects light - and if
light is particles/waves, and there's say 1 million photons that spread like billiard balls, each to a different direction, so they would spread so thin, that there is no coherent image to see. Or is there some physical reason that makes the photons to "stay in shape"?
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askscience
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Sure, you do get down to a limit where you can count the individual photons you're getting - we actually do that in high-energy astronomy where we can detect each x-ray photon individually and measure them one at a time. But if you have a big enough collection area and collect photons for a long enough time, you'll get enough to form an image eventually.
But yeah, if you're giving off maybe 100 W of light, then by the time you're like 50x the distance to the moon, that's like one photon per square metre per second. So you would need a *huge* telescope to really collect enough to make an image.
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askscience
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Are these calculations based on technology we have today, or is this just a general calculation that no matter how much technology we have, the fact would be we'd need a 9 billion kilometer wide telescope? I know you mentioned diffraction-limited optics, not sure if that answers my question and I just don't know enough to know that it does lol
The reason I'm asking is if you think of the televisions from the 90's when I was young, they were big (say, 50" or so and square), but the resolution was terrible (about 480p), now we have smart screens on our phones that are 4-5" and have 2k resolution at nearly 600 ppi.
If say in 100 years the trend keeps going, could this 9 billion kilometer wide telescope possibly be, say, 30-40 meters wide, or again, is your calculations not limited by technology?
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askscience
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[Angular resolution](https://en.wikipedia.org/wiki/Angular_resolution) is limited by the nature of how electromagnetic waves propagate. It varies according to wavelength; my figures are for visible (specifically blue) light, and near-infrared light would require perhaps 25 times the aperture to achieve the same resolution.
You can enhance the resolution of acquired images with modern image processing techniques such as deconvolution of the point spread function, but *CSI:Miami*-level "enhancement" is still science fiction and probably always will be.
That being said, a 40-meter telescope might someday be able to *detect* a brightly-illuminated city on the dark side of a planet 200 light years away, but it would not be able to *visually distinguish* two such cities a few kilometers apart.
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askscience
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There are a couple of problems:
1. The sun is way brighter than the earth. 50 light-years out it will overwhelm the light from earth.
2. The earth spins. Your window to see the earth from a telescope would be very limited.
3. The motion of the earth, in both, its orbit and spin would make the picture very blurry if you were tracking a city.
4. The atmosphere would also add distortion. This is why we have telescopes on top of mountains and in space for looking further away.
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askscience
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The microwaves were emitted by gas from the early universe, though they weren't microwaves yet - they were higher energy photons that got redshifted over time. But this early gas was so thick and dense that it was opaque, so we can't see further back in the universe than that point. The further away things are, the further back in time you're looking. So when you look far enough away, the universe turns opaque, and the "surface" of that wall is what emits the cosmic microwave background
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askscience
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It's because light gets scattered off of ions [(Thomson scattering)](https://en.wikipedia.org/wiki/Thomson_scattering).
Before the cosmic microwave background was emitted the Universe was so hot that all the (hydrogen) atoms were ionized, so there were a lot of free electrons so light could only travel a short distance before being scattered. As the Universe expanded and cooled the electrons joined with protons to form hydrogen [recombination](https://en.wikipedia.org/wiki/Recombination_(cosmology\)) and light was able to travel freely.
[After about one billion years the hydrogen was actually largely ionized again by stars and galaxies, but the density is much much lower due to the expansion of space.]
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askscience
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To add, the telescope would see things that were 50 years old from when it took the picture, but since you can't send the telescope out there in any less than 50 years, you'll never be able to see into the past. If you magically send it out at light speed, then it takes a picture and send it to you, the image will be of the time you sent the telescope out, and you'll get to see it 50 years after that. Or in other words it will be a digital mirror.
Upon some reading, the quasar is only active on the order of millions of years. That might be enough to get life started, but probably not to get some weird civilization of intelligent beings evolved just in time for their sun to disappear.
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askscience
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Engineering?
Chernobyl was based on a stupid reactor type that is not built any more. In addition the operators were actively overriding multiple safety rules and mechanisms - something that won't happen any more because we have an example how that can end. Another accident like Fukushima is not completely impossible if something really bad happens (like one of the most violent earthquakes and tsunamis in recorded history). Chernobyl will stay a unique event.
It is very difficult and problematic to assign numbers to big accidents. They are so rare that there is not enough data to determine it experimentally.
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askscience
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Fukushima is a great example of nuclear safety: the plant had countless safety violations, was hit by a massive earthquake followed by several huge waves of a tsunami, the emergency generators failed.... it was just the worst case scenario, really.
The Japanese have been criticised for hiding the scale of issues, with international reports including things like "it could cause up to 200 deaths from cancer" and similar. There are about 500 disaster related deaths reported so far, but that includes deaths from anything related, including workplace accidents or people who died during the evacuation in a car accident.
In other words, the worst of the worst case nuclear disaster that has happened once in the past decade and was caused by every possible issue is about as a decade of coal mining deaths in America.
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askscience
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The tsunami Wall was originally based on certain historical estimates. As new models for wave runup were made, they twice upgraded the height of the wall to exceed the computer model estimates of the worst tsunami run up.
In 2009 they actually had a new wave model that almost perfectly predicted the 2011 tsunami. It seemed so extreme they had an independent performing a study to confirm it before they upgraded the tsunami wall again. That study was complete the week before the Fukushima accident, there wasn’t any time to act on it.
In my opinion, after the 2009 analysis, they should have implemented or been forced to implement comprehensive compensatory actions to ensure adequate core cooling even if there was a large water run up event. They didn’t consider the possibility that the emergency batteries could be flooded, which greatly complicated the event. Their severe accident guidelines also were not in accordance with industry standards and not maintained, something that the chair of the boiling water reactor emergency procedure committee told me last month was a huge shock to him. He ended up going to japan for 4 months to help them stabilize the plant.
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askscience
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Deaths caused are not the only metric of a nuclear disaster. Do coal accidents render large areas of inhabited urban land unsafe for extended periods? I suppose Centralia is an example of that, but I think the Fukushima exclusion zone is much larger.
[Fukushima exclusion zone](https://blog.safecast.org/2013/12/current-fukushima-exclusion-zone-map/)
Edit: I understand that global warming is a problem that needs to be addressed, and that nuclear power may be an important part of that. But dismissing the Fukushima accident because of the small number of deaths is ignoring the 150,000 people permanently displaced from their homes and the large exclusion zone that won't be lived on again for over 100 years.
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askscience
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Boiling water reactor Mark I and II containment systems are innerted with nitrogen so that they cannot have an explosion inside the containment. And they didn’t. The explosions were due to the containment to being operated over 3 times their design pressure while being overheated, causing leaks. The hydrogen that leaked out is what exploded. But these weren’t containment system explosions.
Post TMI didn’t require passive hydrogen converters. You needed approved hydrogen control systems. For the older bwrs you inerted the containment, and you had to be able to utilize vent/purge of the containment to prevent exceeding the detonation limit. Mark 3 bwrs and the ice condenser PWR plants had to use hydrogen preigniters and recombiners, along with limits on hydrogen generating materials. Large dry PWR containments had no special limits but did require vent and purge capability, as those units should not be building up enough explosive capability to damage the containment.
This is all about the containment though. It doesn’t address hydrogen leaks from the containment.
After Fukushima, foreign plants started requiring passive hydrogen recombiners, but that’s not universal.
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askscience
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This is how I saw it years ago. But it turns out for an autonomous diagnostic AI to be safe and effective, you need to take into account where it is used and how you acquire the "bunch of medical data". Because we focus on bringing specialty diagnostics to primary care it needs to work in primary care - with the staff already there.
​
So that actually required an assistive AI coupled with a robotic camera to help primary care staff that never took images of the eye before take high quality images.
​
Again because of the environment it will be used in, a probability output was not deemed appropriate, so it actually outputs a clinical decision with a referral recommendation.
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askscience
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No issues with primary care docs, because they typically feel uncomfortable making this decion. So they are used to referring these patients to specialists like me - and now they can do it while the patient is with them. That is why I used the term "diagnostic superpowers" for the primary care provider (can be RNPs also).
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There are different views on the training data for machine learning - we focus on high quality data rather than large quantities of data - though we still used over 1 million samples to train the detectors.
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askscience
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Good question. The AI system is not perfect, just as doctors are not perfect - as you can see in the discussion section of the paper. SO this will happen.
There are two real-world scenarios in which this can happen with the autonomous diagnostic AI as currently cleared:
1. more than mild diabetic retinopathy is detected by the AI system, patient is therefore referred by primary care to an eye care specialist such as me, who then concludes the retina is normal - this will happen in about 9% of cases given the 90.7% specificity. Patient hears that everything is OK after all and that they need to be reexamined in 12 months (in the US at least)
2. more than mild diabetic retinopathy is not detected by the AI system, patient is not referred and just happens to be examine by an eye care provider for another reason who discovers diabetic retinopathy. This will happen in about 13% of cases overall, given the 87.2% sensitivity, and we saw this in about 2.6% of cases with the worst disease given the 97.4% sensitivity to vision threatening disease.
edited typo
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askscience
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I'm a FM doc-in-training. AI does not scare me. There is more than enough work to go around. At the end of the day, for me personally it is not about "getting the diagnosis right" but much more about the relationship with my patients and helping them through the various events and stages of their lives.
An AI that takes over the 'hard medicine' part of my work would simply free me to work more on the relationship part, and helping my patients in-between times (you know, the hard stuff like actually changing diet and lifestyle). Hell, I might even be able to do housecalls, wouldn't that be amazing.
An AI -- by definition -- will never take over the vitalist aspects of medical care, for those patients who want it. For the scientific/non-vitalist aspects of medical care, I'll take all the help I can get.
That said, if you're a GP who only does algorithm medicine (as many are) yes, AI might be a concern. Most aren't concerned, but I feel that is because they do not appreciate the scale and capability of the technology at play. (Perhaps more importantly, where the technology will be in a few more years.)
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askscience
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I don't understand why this would or should scare GPs?
First of all it still has to be administered by a GP and doctors (probably rightfully) have a cartel/monopoly on giving medical care and advice, by law. As a result this would only make GPs more productive and additionally able to focus more on the truly difficult cases or the ones requiring a lot of personal attention. Alternatively, it would help them spend more time hearing out patients that have complex problems and giving more personalized care while letting the bulk of ordinary cases be handled by this AI.
Eventually if this was everywhere and made GPs much more efficeint, we would want a few less GPs but this is not a problem as there are way too few GPs at the moment anyway and this shortage is only growing. If this brings down the cost of healthcare, this is good for America and good for the world.
Currently we have no idea what to do when the current population bubble all gets old and we don't have enough young people to take care of them. However if you make the labor of taking care of the elderly more affordable and more efficient, you don't need as many people to do it and thus our societies could continue to function.
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askscience
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> however, the fact that you're there in the first place is the part that would shift.
Oh absolutely. I have no illusions about what my status or clientele will be once AI becomes the dominant prescriber and implementer of medical care.
At the same time, however, AI cannot cover *everyone.* There will always be a large population of technophobes, as well as people who live in areas too rural or poor to support the use of advanced technology. I didn't sign up for the paycheck, so at the end of the day if I'm paid in dollars, bitcoin, or fresh chicken eggs, I'll be perfectly happy.
There is an innate human drive to seek counsel, solace, and healing from a doctor figure. This is at least thousands of years old. Considering the ability of (good) veterinarians to calm animals while working on them, it probably predates us as a species. Computers will never fill that niche, any more than ebooks will ever completely replace real books.
Speaking of books, the market pricing of ebooks is the principle reason I am completely not afraid of AI. If you go on Amazon, the price of a Kindle book is often just a few pennies cheaper than the actual book. You can usually buy the used book for much cheaper. Ebooks should be almost free, but they are not, because of arbitrary fees set by publishing houses.
AI medicine will also have very large fees associated with it. We will be able to provide medical care more effectively and more cheaply than we can right now, but the costs associated with technology-based medical care will be high. Very high. High enough that I'll always have a job and more work than I will ever accomplish.
We're still trying to convince people to use *vaccines* which are a demonstrably safe form of medical care that has been around for a century. If this many people don't trust vaccines, how many more will be hesitant to trust a robot over a family doctor?
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askscience
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OP said this a number of times throughout the AMA so i'll reiterate. This does something that the GP can't, it doesn't make the GP obsolete, it's a tool they use on the patient instead of sending them to a specialist. They couldn't diagnose these conditions in their office in the first place and now they can, so GPs are certainly better off.
It can be argued that it could make specialists obsolete but for now it's a step to free up specialists to deal with, well... more specialized cases.
If an AI could ever entirely replace a medical specialist then it's reasonable to assume that most human activity could be entirely replaced as well so there would probably be more pressing issues at that point.
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askscience
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>While the FDA trial was not designed to compare, here is what is in the paper:
>
>"The results of this study show that the AI system in a primary care setting robustly exceeded the pre-specified primary endpoint goals with a sensitivity of 87.2% (>85%), a specificity of 90.7% (>82.5%), and an imageability rate of 96.1%. Sensitivity is a patient safety criterion, because the AI system’s primary role is to identify those people with diabetes who are likely to have diabetic retinopathy that requires further evaluation by an eye care provider. Previous studies have shown that board-certified ophthalmologists that perform indirect ophthalmoscopy achieve an average sensitivity of 33%,\[27\] 34%,\[28\] or 73%\[9\] compared to the same ETDRS standard."
(quoting myself from another post)
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askscience
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Not sure what you mean by benchmark. In our study we took a sample of 900 people with diabetes. Our paper cites studies of other sets of people with diabetes, showing how ophthalmologists perform (the 33%, 34%, 73% sensitivity) on detecting diabetic retinopathy according to the same reading center standard. Ophthalmologists are highly specialized physicians whose expertise it is to diagnose eye disease including diabetic retinopathy.
There are studies of non-ophthalmologists performing similar tasks, and typically their performance is lower than that of ophthalmologists.
Does that answer your question?
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askscience
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A few years ago I owned a 10 inch reflector telescope. I did some looking around to find the most distant object that an amateur astronomer could hope to see, and found [quasar 3C 273](https://en.wikipedia.org/wiki/3C_273) seemed to be it.
2.4 billion light years out.
Then I did some math to put it in perspective. If you created a model of the universe in which the distance from the Earth to the Sun was 1 inch, then 3C 273, in your model, would be past Neptune in the real world. Think for a minute how insanely *bright* that object must be, to be visible at that distance. (If you brought the quasar to about 34 light years from Earth, it would be about as bright as the sun in our sky. For comparison, our sun is about 8 light *minutes* from us.)
>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.
Someone crunched the numbers on this, I think on Reddit, a little while back. Turns out the size of lens you'd need to be able to do this, would be so massive it would collapse itself into a black hole.
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askscience
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Never found it. It would have looked just like a dim star.
For objects you can't see with the naked eye, there are some techniques for finding them in the telescope. Usually you use "star-hopping" to find it. You first locate some known, visible stars that the object you're looking for is near. Look through your telescope and you can see dimmer stars, then keep referencing your star map, matching up the patterns, and slowly make your way from star to star until you land on the object. This is made trickier by the fact that everything in your telescope is reversed and upside down, so you have to keep that in mind when moving your scope.
Also I had a [Telrad finder](https://agenaastro.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/o/f/ofin-te-tel-1s_6.jpg) on my scope that helped. It has illuminated bullseye rings, the rings are (IIRC) 1, 2, and 4 degrees diameter. So if you know your object is 2 degrees from a star you can see, you set that star on the largest ring and then your object should be in the center.
It's pretty thrilling to spend some time doing this, and have it pay off when you finally check your eyepiece and BOOM, there it is! Takes practice.
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askscience
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That gives me an interesting thought. With the large number of rogue planets we expect to exist, it seems possible there could be some that happen to be close enough to a quasar to get energy from it to support life.
I'm not sure what the wavelengths would be like, or if it might be hostile to life. But the energy might be there and life might be able to evolve.
Weird thought. No nearby planets, no seasons.
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askscience
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I operate a nuclear plant that came online around then.
Here’s the main difference. My unit requires active power to sustain critical safety functions, and we have events that require human action within 2-10 minutes. The plant has a slew of automatic safety systems, but they are dumb systems that trigger on specific signals and have no ability to monitor the overall health of the plant and make intelligent decisions, they are only there to deal with immediate plant stabilization until us operators can take control.
Meanwhile, new plants are walkaway safe for days or weeks, and in certain cases, indefinitely. They require little or no electrical power to perform critical safety functions, and can be made safe using pre built external fire truck hookups.
Please feel free to ask questions.
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askscience
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Depends on the event. For a large break LOCA I’m supposed to have RHR heat exchangers in service within 10 minutes to remove decay heat and maintain containment pressure/temperature within limits.
For a non complicated event you may not need to do anything. Plant scrams and self stabilized.
It’s all very event based. Additionally, while safety analysis assumes no operator actions for 10-30 minutes and only minimal actions after that, operators can perform more effective mitigation actions by being able to diagnose the event. So an example, is if you blow a reactor coolant pump seal, you’ll have a small LOCA, causing a high drywall pressure eccs initiation signal. The operators can diagnose this event and isolate the pump loop and stop the leak, preventing the eccs from initiating. The plant stays safe with no human action, but with human action you have a much less significant transient, no cold water injection of lower quality water, no loss of non vital systems due to load shedding and emergency response sequencer logic.
Boiling water reactors in particular also have 90-120 second time critical actions in the event the reactor does not shutdown when required, which is to prevent significant core damaging oscillations and instability.
I’ve seen 16 scrams, and only 1 required significant operator actions to stabilize the plant. Typically you just watch the plant take care of itself and take the follow up actions.
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askscience
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It’s not really feasible. For non safety control systems, putting digital upgrades in can easily run 15-20 million. Safety related digital systems with logic controls is far far more expensive. Another issue is you need more data from the plant for a control system to make smart decisions. Our last digital upgrade reused most of the old instruments and cabling, if we wanted to get more data to it to make smarter decisions we were looking at large increases in price. Instead we found relationships between various parameters that allowed us to indirectly infer reactor power (rather than directly sending a reactor power signal to our feed water system) and gave us similar functionality.
But the regulatory requirements, data and inputs required, and testing puts these types of upgrades out of reach for economic purposes. Additionally generation 2 reactors are not designed with passive safety features. That means you need pumps to work, valves to operate, which may require human intervention if the automatic controls fail (which they do from time to time). In a plant with passive safety functions, you generally only need one or two things to work and you get hours or days before you have to make major decisions or intervene. In active safety plants, like all generation 2 plants, you can uncover the core and breach the reactor vessel in 45 minutes to 2 hours depending on plant type, so if a valve motor fails you don’t have passive safety backing you up until you can fix it. You need an operator to go out there and manually open it.
Just a quick chat about digital systems, the software quality assurance and digital system integration requirements are very challenging, and even non safety systems can require extensive paperwork and testing. The fear with these systems is that a software flaw is a design flaw, and the error it causes will happen simultaneously in all redundant channels of the system at the same time when it is triggered. The potential for common cause failure frightens the us nuclear regulatory commission and is why many plants stopped doing digital upgrades and instead pay large sums of money to get old 1970s solid state circuit cards refurbished.
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askscience
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They aren’t taboo. They are uneconomical in most places. It costs so much to build nuclear units that it doesn’t make short term sense, even when nuclear is the better long term option, and that’s especially true in merchant markets.
At least in the us, the huge increase in “fracking” and the US becoming a major natgas producer has shifted the market. the expanded use of natgas plants (especially combined cycle plants which are 50-60% cycle efficiency) has driven electricity costs low enough that coal and nuclear struggle in both short and long term cost projections. Additionally there is much less risk to building a natgas unit compared to a nuclear unit. It takes 3-5 years to build a 1 Gw combined cycle natgas plant which can be operated with less than 50 total staff and costs 4 billion usd. A 2 GW nuclear plant may come online in 8-12 years, with significant regulatory hurdles, 16-22 billion usd cost, and 800 staff. So there’s a huge difference there and that’s before you even consider the long term costs of spent fuel management and site disposal. You take on huge liabilities before the unit is even finished building.
Economics have killed nuclear. The taboo has mostly gone away in most of the US. And overseas we are seeing a lot of nuclear expansion.
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askscience
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> 1 Gw combined cycle natgas plant which can be operated with less than 50 total staff [...]. A 2 GW nuclear plant [...] 800 staff.
Wow. I had no idea that staffing requirements were *that* much larger for nukes. What's the rough breakdown between physical/engineering requirements and regulatory requirements here (for staff)?
I'd always assumed staffing requirements for nuclear plants would be somewhat higher, but factor of 8 (for equal power) is way out of the range I would have guessed.
Cheers,
Michael
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askscience
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Well....typically the largest driver for staffing is meeting minimum ops/security staffing, and having sufficient staff for emergency response purposes. Emergency response requirements drives a large amount of minimum staffing. Those positions are used and needed for other stuff though.
It’s really hard to say without going into the nitty gritty details. From a pure legal perspective, you have to maintain the stuff above. Minimum operations staffing is typically 3 senior reactor operators, a shift technical advisor/engineer, at least 3 field operators, 2 rad techs, a chemistry tech, and 1 or 2 maintenance techs. Like that’s bare minimum. Plus you also need a fire brigade staffed (we use field operators for it at my station, but it’s different everywhere).
But you have a ton of required maintenance you have to do, much of which is regulatory driven. You have Engineering, which you need a full time technical staff because you literally can’t change lightbulb designs without a 100 page change package (seriously.....took a colleague of mine almost 2 months to change the approved design for light bulbs in the plant to switch to LEDs). Then you get new regulatory stuff, or INPO/fleet requirements and projects, and it becomes overwhelming.
One big thing that hurts, is the nrc has kind of extended their oversight outside of the reactor system. Example: if you have a turbine control valve fail which causes a reactor scram, the nrc can give you violations for that. Even though the plant is designed to be safe in that condition explicitly, the fact that you failed to do adequate preventative maintenance on a power generation asset which led to a reactor scram is a violation of maintenance rule. You never lost a safety function, never lost operability if any license required system, but it’s still an issue. So you have all this required preventative maintenance you have to do in the power production side of the plant which anywhere else you would just run to failure or until a major scheduled maintenance outage.
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askscience
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Decomposition is an exothermic process. A common problem where large piles of wood chips are stacked (mulch piles, etc). With enough air into the pile and enough decomposing material, fire can and does happen.
decomposing material also releases methane, which in the right environment can be ignited by sparks from a convenient rockfall.
It’s even been discovered that spontaneous fission reactions have take place in pockets of fissile ore that reach critical mass.
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askscience
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Don’t know about op but I can answer for my country. It’s not usually hot here. We usually get a couple of weeks in the summer of good dry weather where we can cut and dry the hay before storing it. A neighbouring farmer had his hay shed catch on fire because of this during rain shortly after bringing all his hay in.
It was funnily enough the rain that essentially caused the whole thing. He had made the hay and usually if it’s sunny you leave the bales out where they can dry in the sun. Unfortunately it was set to rain a few days after he baled the hay so he brought it in early when it was still wet and stacked them tightly in his shed. One or more of them started to essentially rot in the middle where or was wettest and warmest and the bacteria responsible for the rotting gave off enough heat to cause the bake to catch fire
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askscience
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When I was a kid I used to look for snakes in my neighbours garden as his compost heap of cut grass was always warm which reptiles love. One day I stuck my arm into it and nearly burnt my hand. I got inquisitive, took pitchfork, stuck it in to the big pile and lifted it up exposing the middle: it immediately burst into flames. I dropped the fork and it all went out. Walked away whistling, never told anyone.
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askscience
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It can happen in winter also, the outside temp doesn't matter much. I had a compost pile next to my garden that let off lots of steam in the winter when the conditions were right. It never caught fire. In hay barns when damp hay or straw starts to rot, sometimes the hay doesn't burst into flames but smolders until finally going out on its own leaving a black charred hole in the stack of bales or loose mound. Most of the time you just get moldy hay though.
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askscience
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My municipality is heavily forested and many of the neighborhoods are old and built in amongst the trees, rather than modern developments where everything is clear-cut first. As a result we have leaf collection provided by the counties around here in the fall. If you drive past any of the waste transfer sites you can see massive piles of wet leaves smoldering as a result of the same process. Always wigged me out as a kid.
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askscience
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Thank you! Let me ask another question: when two protons crash in an particle accelerator, for example, do they have enough energy to "break" each other apart as if they would collide inside their orbitals would imply the strong interaction doesn't have enough time to repulse them - or would the breaking into quarks be a result of the strong interaction getting so repulsive(as to counteract the protons getting closer and closer) that the energy generated would explain it.
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askscience
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Two protons in colliders don't have orbitals. If they have sufficient energy the protons can get destroyed and you can get a few to tens of new particles (sometimes more than 100 at the LHC). At this energy level you are more looking at collisions between quarks and gluons - that they happen to be in a proton doesn't matter much as the proton binding energy (and all other potential energies) is tiny compared to the energy from the accelerator.
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askscience
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What about the mechanism in which atoms nuclei are shot with protons or neutrons(transmutation for example), the reason protons or neutrons can be removed from the nucleus this way, can be explained by the strong interaction being repulsive at small enough distances? Meaning that the proton shot manages to get so close to the other proton, that the repulsion generated is larger than the binding of the proton being shot at and the nucleus it is bound to.
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askscience
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Nuclear reactions occur at much lower energies than LHC collisions. But both attractive or repulsive interactions can cause nucleons to be knocked out of some target nucleus in a reaction. The repulsion of the NN force at short distances isn’t really directly observable in the case of a reaction between a nucleon and a nucleus of A > 1, because you can’t pinpoint locations of individual nucleons within the nucleus.
For reaction theory calculations, you often have phenomenological optical potentials that describe the interaction of the incoming nucleon with the entire target nucleus. The optical potential is complex, so it allows probability flux to leave the elastic channel, and go into reaction channels.
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askscience
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> The repulsion of the NN Force at short distances isn’t really directly observable in the case of a reaction between a nucleon and a nucleus of A > 1, because you can’t pinpoint locations of individual nucleons within the nucleus.
In that case, would you have a different answer for the first follow-up question I asked?
I also don't think I completely understand your second paragraph, but I guess it's on the realm of quantum mechanics?
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askscience
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/u/mfb- answered the question at HEP energies (TeV), and I'm answering at nuclear physics energies (MeV-GeV).
The two-proton system has no bound states, but it has at least one resonant state that can be populated (the diproton). There is also a reaction channel, where the protons combine to form a deuteron in a weak-mediated reaction. This happens in the sun, but the cross section is too low to observe it in accelerator experiments.
If you collide protons at nuclear physics energies, you'll mostly get elastic scattering (Coulomb and/or nuclear, depending on their relative kinetic energy). You'll also get some resonant diproton production, and deuteron production, both with extremely small probabilities.
At higher energies, you can start to probe the valence quarks within the protons. You can flip one of their spins, and turn a proton into a delta resonance. You can have all kinds of weak reactions, where some number of quarks change flavors, and turn one or both protons into some other heavier hadron.
At extremely high energies, you'll start to smash apart protons, as mentioned above.
>I also don't think I completely understand your second paragraph, but I guess it's on the realm of quantum mechanics?
Yes, everything discussed here is quantum. Classical mechanics can't really describe anything in nuclear or particle physics.
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askscience
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> If you collide protons at nuclear physics energies, you'll mostly get elastic scattering (Coulomb and/or nuclear, depending on their relative kinetic energy).
Correct me if I'm wrong, would this mean that Coulomb scattering would occur in lower kinetic energy levels, whereas nuclear would occur on higher, but yet, nuclear energy levels?
> At extremely high energies, you'll start to smash apart protons, as mentioned above.
What force is responsible for that?
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askscience
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The F-104 does *****NOT***** have small wings. It is a very deceptive looking aircraft.
An F-104 has 200 sq ft of wing area for a 6 ton plane. An F-15 by comparison has 600 sq ft of wing area for an 18 ton plane. A 747-400 has 5600 sq ft of wing area for a 180 ton plane.
So a 747-400 a jumbo jet has smaller wings than the F-104 relative to the weight they carry.
The F-104 is just a full sized jet engine with parts from a 1/3rd scale plane attached to it. If you remove the engine and cockpit there is very little else to the aircraft.
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askscience
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The mass of a plane has very little to do with flight. It's about the lifting coefficient of the plane, and the power to weight ratio. The design of both the F-15, and even a 747 have much larger lifting areas including both body and wings then a Starfighter. The F-104 is basically a jet engine with some control surfaces strapped on compared to any other comparable 1950s through 1970s military aircraft.
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askscience
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The body area isn’t particularly relevant to the performance of an aircraft. The thing that matters for limiting performance is the drag for the body. You could easily make the fuselage volume 10x bigger and if you reduce it’s drag you end up with higher performance. That’s why you’ll never see such a number. The ratio can be arbitrary and change with few consequences like with extended fuselage models.
The wing shape definitely plays a role in efficiency vs performance though. The F-104 had a comically inefficient wing. It was so thin that [the leading edges](https://qph.fs.quoracdn.net/main-qimg-8a68a20f38d41d01a5e46ebc47886fce-c) had the profile of a knife and needed protective covers on the ground.
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askscience
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Wingspace is only half the battle. The thickness of the front compared to the back makes a massive difference.
The planes you mentioned, their wings are proportionally smaller to weight, but they are much thicker. The pressure differences, and of course the drag as well, are considerably better.
A DC-3 has VERY thick wings overall. Which is why it can takeoff in shorter spans than a ww1 fighter even gross weight. The tradeoff being very high drag and slow flying overall. But its practically a helicopter empty takeoff.
The f-104's wings, much like the f-5 or f-20, are razor thin. No angle of attack much at all. Its lifting muscle is pathetic. Probably stalls at 220mph or more gross weight.
Its built for speed and high-G high speed based maneuvers only. Not my cup of tea at all, but i can respect purpose-built aircraft.
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askscience
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A conventional round fuselage, such as the F-104 has, produces negligible lift, but the F-15's body actually does produce useful amounts of lift. The lifting body design is the reason an Israeli F-15 made it home despite having a wing sheared off almost at the root in a midair collision. The pilot didn't realize how much of the wing he'd lost until he landed, and McDonnell-Douglas engineers said it couldn't fly until they saw pictures. After some wind tunnel work, they found that the lifting body design was more effective than they thought.
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askscience
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I was at the Cleveland airshow last weekend and saw a lot of C130s and thought they would be huge. They were obviously larger than the average military plane but when I saw the size of the C5M (Super)galaxy I was blown away. Compared to the size of the C130s parked next to it my mind was blown. I swear you could fit 2-3 C130s inside the Galaxy/Supergalaxy if you folded their wings up.
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askscience
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At an air show years ago, I had a great time walking around an F-16. Standing under the wing, I had to put my ear on my shoulder to fit. After that I went over to an F-15 and had to stretch out my fingers to touch the wing. The F-15 is *huge*.
Someday I hope to do such a walkaround of an F-22. They seem to be of similar size to the F-15, but I've not googled the specs. *Definitely* sexier, though.
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askscience
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C-130: F-150 of the sky. It can go off-roading and haul some stuff for the weekend. C-17:Semi-Truck of the sky. Still pretty flexible in where you can drive it, and you don’t even always need pavement. You can take the whole house with! C-5: freight train of the sky. You can only go certain places because you’re so big, but you can move an entire construction crew, including all their vehicles!
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askscience
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1 and 2 ejects for my relatives respectively. They both went on to pilot F4 phantom II's;
Apparently a difference of night and day; but then again, as germans do, they got them delivered with all these cool useful gadgets, that was not in the contract (might have this a bit wrong/backwards), then paid more money to have them removed; only to have them bought again at a later date and reinstalled at a premium.
​
Apparently they were a technological joke compared to the Turkish F4's, in terms of capabilities; but then again the turks used to steal the german firefighting equipment every-time the germans brought that stuff with them, cause the turks did not really have any.
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askscience
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Even more importantly, in times of war you want to save your pilots at any cost. It's relatively easy to make new planes, but training new pilots takes a lot of preparation and time.
That's basically what led to the demise of the German air force after a few years of WWII - keeping experienced pilots in the field too long and having too many of them killed, losing their experience and ability to teach new pilots better, thus resulting in badly trained rookie pilots entering the field against professionally trained allied pilots.
At the beginning of WWII the German air force had some of the most experienced and best trained personnel worldwide or at least in Europe. IIRC, In the early 40s, when the British and Americans were training their new pilots extensively (up to 100-300 flight hours before entering conflict), the German air force was burning through their experienced pilots on the front lines and throwing in inexperienced pilots at something like 20-30 flight hours.
Keeping that in mind the post-war Starfighter fiasco would have had really bad effects in war times, especially considering that air superiority was necessarily required to deny attacks of superior Soviet mechanised ground forces.
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askscience
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There's lots of different rules... But it's all trade offs. Big thick wings might have more drag but they can carry lots of fuel and stores etc. Large wings can give excellent turn rate but terrible roll rate etc.
The area rule is worth looking into though. Basically if you cut an airplane up like salami, you want the total area of each slice to be the same - even if the shape of each slice is wildly different.
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askscience
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Anderson's Intro to Flight might be the best option for the basics without the prerequisite knowledge.
In reality, fixed-wing aircraft design books (that really address the basics of why they be how they be) are senior-level undergraduate texts because the chain of prerequisites goes roughly like Calculus + Physics > Differential Equations > Fluid Mechanics + Mechanics of Materials > Aerodynamics > Stability and Controls + Vibrations + Aerospace Structures > Flight Mechanics > Design.
Aerospace undergraduate design "capstone" courses really earn the moniker. Sadly, I can also tell you that most fresh graduates with a bachelor's in AE still won't be able to answer many of the "why" questions simply because there are so many considerations.
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askscience
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As discussed elsewhere in the thread, if the F-104 didn't actually have small wings for its size (200 square feet for 6 tons empty / 13 tons MTOW) then the F-102 *definitely* didn't have small wings for its size (660 square feet for 9 tons empty / 11 tons MTOW). In fact, its wings are [larger than that of the ATR-42](https://en.wikipedia.org/wiki/ATR_42#Specifications) while the ATR's MTOW is over 18 tons.
The F-102's troubles were elsewhere.
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askscience
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On a related note, that's why the T-38 supersonic jet trainer, which was designed around this same time period but is still used today to train USAF pilots, seems to have such stubby wings and aerodynamically is a very high wing-loading plane.
It was meant to emulate the flight characteristics of the F-100, F-102, F-105, and other high-speed-optimized interceptors. No fly-by-wire, HUD, or leading-edge extensions like nearly all frontline US fighters now have. Nor does it have automatic flaps like its derivative, the F-5 Tiger II (also known as the "MiG-28" in the movie Top Gun).
For those reasons, though, it is incredibly unforgiving at low speeds and especially low altitudes. Many T-38 pilots have been killed in the landing pattern as a result of pushing bad approaches. You're rolling the dice if you develop a high sink rate and don't execute a stall recovery.
That being said, if you can fly a T-38, you can fly just about any pointy-nose fighter. It's only now that the fleet is now on average 50+ years old and there is an increased need for undergraduate pilots to learn more complex sensor and systems management that the USAF is seeking a replacement.
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askscience
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Nope!
So we're going to pretend the Earth is a perfectly rigid body that can stop on a dime, while the people on top are not attached at all, and also there's no atmosphere. If the Earth suddenly stopped moving, the people would continue to move forwards at their current velocity. Is that fast enough to escape the Earth?
The emphasis here is that you would continue to move *at your current velocity*. If you're not escaping the Earth right now, then your speed is below escape velocity. The Earth stopping won't make you speed up. Think of it this way: if the surface of the Earth was moving close to escape velocity, then the Earth would be basically flying apart.
I'll give you some numbers to get the scale of it anyway. The Earth's equator is about 40,000 km around (that's more or less the original definition of the metre). The Earth rotates about once every 24 hours (it's actually slightly faster than that - a day is 24 hours because that's relative to the Sun and we're moving around the Sun, but 24 hours is close enough for this estimate). 40,000 km/24 hours = about 460 m/s, or 1,700 km/h, or 1,000 mph. It's somewhere between mach 1 and mach 2 at sea level. By contrast, escape velocity is about 11 km/s - that's about 40,000 km/h, or 25,000 mph. And just to orbit in a circle means you have to go at about 8 km/s. The Earth's rotation is fast enough that it *does* matter which direction you launch your rocket - it makes like a 10% difference in speed - but it's still on the level of a supersonic jet rather than an interplanetary rocket.
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askscience
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You doing it wrong the earth is no longer moving.
Escape velocity is affected my the earth's momentum. so you take your weight and the speed we travel while on the earth around the sun to calculate our momentum. Then you need to calculate how far earths gravity would let you travel before it reasserts itself on your momentum.
Also depending what side of the earth you on.
You may just get slammed in to the ground.
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askscience
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Nah it's a coincidence. The rotation speed at the equator happens to be about 5% of escape velocity, which is ~1/20th. We divided the day into 24 chunks because 24 is a nice number with a lot of factors. 1/20th is just sort of close-ish to 1/24th.
Venus has about the same escape velocity as Earth, but is tidally locked and rotates once every 240 days. The rotation speed at the equator of Venus is about 6,000 times lower than its escape velocity.
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askscience
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Ha! Just a coincidence (it's also not precise). The units end up the same, which is helpful, you're going to have a speed when you calculate EV, and circumference/hr is a speed.
And EV is based (in part) on the radius, and circumference is as well, of course, so you've got at least one common variable. But it stops there.
The mass of an object affects EV, so if the planet was denser or lighter, the relationship would be thrown off without the circumference changing. The hour is also arbitrary here.
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askscience
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If the earth stopped rotating, from your point of view you would be launched at close to 1000mph at the equator. A little less the further north or south you were. Provided you weren’t splattered against anything you would gain some altitude and decelerate but would probably not even get close to leaving the atmosphere. Just a pretty long ballistic arc. You would get pretty hot too I imagine.
Edit: I was wrong, at most you would just skip along the ground at high speed but you would not get launched into the air at all.
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askscience
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> you would gain some altitude
You wouldn't. If you're not fast enough to gain altitude now, you wouldn't be fast enough to gain altitude when earth stops spinning. Your trajectory is only influenced by the spinning insofar that the spinning determines your velocity. If earth suddenly stopped without you sticking to the surface, your velocity wouldn't change at all, so your trajectory would also stay the same (except that the ground would now slow you down due to friction, so you'd be even less inclined to gain airtime).
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askscience
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On a much smaller scale, I'm reminded of an accident involving the attack submarine [USS San Francisco](https://en.wikipedia.org/wiki/USS_San_Francisco_(SSN-711)) which struck a seamount while moving at nearly 35 knots.
For those inside the sub, in their own reference frame, they would have felt relatively motionless, like sitting in an office building. When the sub struck the side of an undersea mountain and came to an abrupt stop everyone on that sub was suddenly hurled at the nearest bulkhead at nearly 40 mph.
Everyone on board was injured, though amazingly only one sailor died.
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askscience
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The difference is right now our velocity relative to the earth is zero. If the earth stopped spinning our velocity would remain the same, but our velocity relative to the earth would drastically increase and our momentum would carry us in a straight line tangential to the surface of the earth, which from our perspective would be into the air. Gravity would force that into an arc meaning we would spend some time in the air at least. Realistically yes, the surface is uneven so the friction of the initial drag against the ground might prevent lift off or you may just skip off rag doll style and fly in a long arc.
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askscience
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You're right, of course. They're both analogous to the whole "Earth suddenly stops spinning" scenario.
But at least in a car you can look out the window and see the world rushing by. There's an obvious sense that you're hurtling down the road.
But in a sub it would seem (not completely, but relatively speaking) motionless, kind of how we feel standing in our kitchens or sitting at the desk at work, right up to the sudden stop.
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askscience
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Our momentum is already moving in a straight line tangential to the surface of the Earth. The only thing keeping you on the Earth is that gravity is already curving an arc into your path, and that arc curved greater than the surface of the Earth. Since your velocity and the effect of gravity would not change if the Earth stopped turning, your path through space would be unaffected. The only thing that'd change is the topography under your feet.
If you were on a flat surface such as a lake or salt flat, the only way you'd lift off is if your tangential velocity was greater than escape velocity (about 8km/sec at sea level). Since it's not, you'd smear/tumble along the ground, but otherwise continue on your arc (which due to gravity is a sharper arc than the curvature if the Earth).
The only way you'd gain air is if you were standing on top of a hill or building, or bounced off something.
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askscience
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Our velocity relative to the earth's surface is irrelevant for our trajectory. Our trajectory is determined by our position and velocity relative to earth's center of mass, which does not depend on how fast the earth is spinning. Our velocity relative to the earths CoM is already non-zero, and our trajectory would already describe an arc - except that every point on this arc is *below* the earth's surface. Since we can't just penetrate the surface, our trajectory is instead determined by the surface. But this holds regardless of how fast the surface is moving relative to us.
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askscience
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Or kind of dry while they also go flying through the air, with a continent full of debris chasing them.
So maybe dry, but not so fine?
Edit: Reading some of the other posts made me realize that I should clarify that by “flying through the air” I don’t mean lifting off the surface. More like, if you were on the edge of the ocean you would now be on the edge of a slope where the ocean used to be and thus perhaps only briefly airborne until you met sand/rocks/etc.
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askscience
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Earth spins at about 0.5 km/s, moves around the Sun at about 30 km/s, and moves around the galaxy at about 200 km/s. So you're dominated by the motion around the galaxy there. Of course, velocity is relative, so this isn't the "real" speed of Earth, because there is no such thing as a "real" speed, just speed relative to other things. The Milky Way is moving relative to Andromeda etc too so you can keep on going.
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askscience
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I'm going do a quick and dirty estimate assuming the earth is flat, and that an average male is jumping an average height; 0.5 meters. Given 9.81m/s² gravitational acceleration, we can solve for initial upward velocity, and more importantly, time in the air:
Vert. Velocity = sqrt(max height * g * 2) = 3.13 m/s
Air time = 2 * Vertical Velocity / g = 0.64 seconds
1000 mph is 1467 ft/s, or 447 m/s. In that 0.64 seconds, our jumping person will land about 940 feet or 286 meters from where he jumped up. Given the relatively close proximity, it is safe to say that our assumption regarding the earth being flat is close enough.
When impacting the ground, he'll now be moving sideways at 447 m/s and downward at 3.13 m/s. Clearly, survival is not possible in this scenario. Remember that orbital velocity at sea level is about 7900 m/s, so we're only traveling at 5.7% of the required speed to simply maintain a fixed distance above the ground. Even if someone did jump up and that velocity was instantly attained, the orbit would be elliptical, such that the orbital height will reach zero every single orbit...
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askscience
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I’m really surprised by how many people don’t understand the sheer magnitude of everything on the planet tumbling out of control on the crust at that velocity.
Smash your finger with a hammer at 10km/h. Ouch. Now do that to your whole body a hundred times. While inside your vehicle tumbling for a full minute against a mountain while another mountain of everything you own follows you and falls on top of you as if dropped from a great height.
Meanwhile, large boulders are flung off their mountains at over 1,000 km/hr causing sonic booms across the entire terrain shattering anything fragile or malleable. Then landing into whatever they hit peppering impact craters the size of tall buildings in every direction.
Sand and glass flung hundreds of feet in the air blocking the sun for weeks and turning all water bodies smaller than Lake Michigan into a muddy soup. Plus, it’s raining debris.
All caves collapsing or filling with water.
Meanwhile every single continental fault and mountain range buckles for hundreds of miles or separates causing shelves of continent to slide for hours into the ocean.
The tops of all active and inactive volcanoes are sheared and begin to spew magma high into the air.
But we’ll ok okay, right?
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askscience
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**Edit: NVM, on second thought even if the earth is a sphere it's way too close to flat on our scale (and with gravity) to matter.**
Even with gravity wouldn't a person in the middle of a perfectly flat parking lot still lift up from the ground before curving back down and going splat? I would imagine that kind of momentum would be enough to do that if we applied it to a person right now in the same location.
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askscience
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Thank you! The part I don't understand are the comments further down that you wouldn't gain *any* altitude. Wouldn't the trajectory of your sudden relative momentum be a parabolic arc (like a discus thrower) - and at [up to] 460 m/s? In gravity weak enough that we can gain a few feet of altitude just by jumping while standing still, it's hard to visualize why that trajectory and momentum wouldn't buy us *some* altitude.
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askscience
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there would be no vertical lift as such, but if you were going fast enough, and there was nothing to your east blocking your flight then you would get some apparent lift the further you travelled due to the earths curvature.
Unfortunately you wouldn't be moving fast enough. If your forward speed is enough that your fall rate from gravity is less than the earth's curvature, you are looking at being in orbit. In this case the orbit would see you come back to (exactly) the earths surface and you would almost certainly impact something to the west of your start point! This is also ignoring any air resistance which would slow your orbit to at least some degree and cause your orbit to move to below the earths surface, which will mean impact with the ground even if you don't hit a vertical object on the way.
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askscience
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Depends if the atmosphere stops rotating too. If it stops, then the plane is suddenly going to be moving 1000mph quicker relative to the air (edit: I suppose the opposite is true if you are traveling East to West, you would lose 1000mph of velocity, which means you are now traveling backwards by several hundred mph. So... Bad), which I would imagine is far above what an airliner is designed to handle. If the atmosphere keeps going, then it would be like nothing happened initially, but then it works probably get extremely turbulent very quickly since there are now 1000 mph winds covering most of the globe.
Very far north or south flightpaths would be better, but anywhere close to the equator would be bad.
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askscience
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Two details:
The entire air and water mass would ALSO be going at that speed. So stop the earth? Gratz, you got an ocean going over 1000kph, and its coming for you, if the splat and the air mass at 6 times hurricane speed (and 36 times more energy) didn't get you first.
Btw of all the people, the ones most likely to not die immediately would be esquimos. They'd be going a LOT slower. Plus they'd be going along a very flat surface you can slide in.
A much greater percentage of people in siberia, alaska and so on would survive. Those on the equator, or up to say 30th parallel would be right and truly f...
People on planes could also have a chance... very small one.
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askscience
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If the parking lot was flat, no. You would move in a straight line and be pulled down by gravity (which has a much slower acceleration than the lateral g-force you're experiencing in this moment). If the parking lot was curved to match the earth's curvature, you would in theory lift off slightly, but the scale is so huge that I doubt you'd notice it. Plus you're flying east at 1000mph and you would travel 366 feet in 250 milliseconds but fall 4 feet in that same time. The earth's curvature isn't nearly enough to lift you off the ground at that speed. You'll just skid along the ground until you're smashed by something larger than you.
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askscience
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I get the feeling the plane would just get ripped apart by the turbulence before it could even slow back down to a reasonable speed to land.
If the Earth stopped spinning, you would essentially get 1700km/h winds on the surface the instant it happens. While at higher altitude, the impact might not be immediate (since the air would just get tossed in the same direction as the plane), there is inevitably going to be some nasty aftermath.
Just picture a 1700km/h winds blowing on a mountain. That would create a high pressure front, and huge updraft, which is eventually going to spread and create turbulence in high altitude. When this kind of dramatic event would happens all across the globe, and you're in for a nasty storm.
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askscience
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The Earth's equator rotates faster than the speed of sound. Therefore, of the Earth stops rotating but not the air, shock waves would be launched at the ground air interface. These shockwaves would propagate upwards from the Earth's surface slightly faster than the speed of sound. The air behind the shock waves would be hot and dense. At some height, the shock front would dissipate into a regular sound wave of large amplitude, with a wind following the wave, moving at almost the speed of sound. The air plane would probably be hit by this intense wind coming from below. I would not be surprised if this wind tears off the wings of the plane, but I'm not sure about that.
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askscience
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In case it's unclear, though: if we ignore atmosphere, obstacles, the sun/moon/etc, and other such complications, then whether you would escape would actually [not depend on the angle at which you are "launched"](https://www.quora.com/Why-does-escape-velocity-not-depend-on-the-angle-of-projection). Sent straight up with a smidge more than escape velocity, you just keep going out in a straight line, forever slowing down but at a *decreasing rate* that can never overcome your kinetic energy.
Launched on a tangent, you end up with a curved [hyperbolic path](https://en.wikipedia.org/wiki/Hyperbolic_trajectory) that the planet's gravity is never able to bend back toward itself. But the threshold velocity is still the same.
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askscience
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You'd die there too. All the water in the North and South would be pulled towards the equator since the momentum of the equator would pull the water away. You'd be in the ocean but it would half empty out. This would be fine. Then it would fill in again. That would not be fine. Tsunami after tsunami would obliterate anything on the oceans in the north or south.
Maybe Antarctica, at the pole would be fine. You want to be away from any large mass of water.
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askscience
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Related... if the earth stopped *orbiting*, then people on the lucky side of the planet would be flung skyward at roughly 30 km/s, or three times escape velocity. People on the unlucky side would be turned into a thin paste.
Ignoring the fact that the "lucky" ones would be killed instantly by the g-forces and almost certainly incinerated, I still don't think they'd manage to actually escape earth's gravity, since they would have no sustained thrust, and air resistance is a thing. But I could be wrong!
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askscience
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Probably best case scenario (for a given interpretation of "best") is standing on a roof in like New York, from which you would find yourself suddenly and rapidly projected out over the Atlantic (or is it LA & the Pacific? I can never keep that straight in my head) at a few hundred feet up. Seems like there'd be a tiny chance (if you had enough of your wits about you as you hurtled through the air) that you could get yourself into a diving-ish position and survive contact with the surface of the water.
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askscience
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Thank you for this comprehensive answer!
Follow-up question: Let's pretend the earth is perfectly round and you are like 1mm thick and there are no objects you can crash into (and no other forces involved), so you get thrown sideways at 460 m/s - perpendicular to earth's core, so you'd be moving away from the curvature of earth. What would be your highest altitude following your ballistic curve?
Here's what I mean in paint: https://i.imgur.com/0Rk02hr.png
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askscience
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Did you ever stop to think that the supposed 'leaking o-ring' on Challenger would have had to be perfectly aligned with th LOX tank, then shoot a narrow jet of flame across six-feet of near vacuum slip-stream roaring by at 2,000mph and then magically burn through 3-feet of structural foam and thick stainless steel of just the aft O tank, but the shuttle disintegrated from up at the forward pylon and never achieved 25,000mph escape velocity?
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askscience
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Depends on whether the ocean is considered to be part of "the Earth" or not. Presumably, since there is a distinction between "the Earth" and objects on the surface, a line has to be drawn somewhere. So, if all the water stops too, then you would just zip forward at several hundred mph. And yes, I know that even in this scenario, the boat would be ripped apart from all the sudden extra drag on the hull. It's a silly conversation in general.
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askscience
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Because the start point has a velocity vector in the "zenith" direction (outward direction away from the body being orbited). This forces the orbiting object to ascend to a higher orbital height, while simultaneously decreasing to a lower forward velocity. At the highest orbital height, where the speed has decayed to a minimum, the actual speed is now insufficient to maintain that orbital height, and the orbit decays again back to the minimum height, regaining the forward velocity it had lost at the same time. It is important to note that the maximum altitude is called the "apogee", and the minimum height is call the "perigee". Assuming that the person jumped perfectly straight up, the apogee will occur on the opposite side of Earth from where he was when the jump occurred.
All this, of course, assumes zero drag or other losses of energy!
I highly recommend checking out /r/KerbalSpaceProgram/ for a fun way to get hands-on experience with these concepts.
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askscience
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This right here, the effects of sudden stoppage of spinning, is waaaay more interesting. Equatorial oceans suddenly moving at a 1000mph. People just flying across the street and into a tree, or fence or building...if the building is there. Massive buildings ripped from the foundations, rolling and shredded into short-lived half mile-wide shrapnel storms. I would imagine a lot of top soil just ripped from the ground and, depending on bedrock undulations- sliding to a stop or ramping up in the air hundreds of feet. Even at 45 degrees latitude(between Rome and Paris), you're still going ~500mph.
The northernmost permanent settlement in Nunavut, Canada is at 82 degrees lat- there, you'd be going ~90 mph. Imagine skipping across the ice (or rocks) at 90 mph. Very few, if any survivers, lol.
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askscience
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Yeah I always think of a similar scenario!
What if you take the velocity of a particle in a particle accelerator on earth, the rotational velocity of the earth, the orbital velocity of the earth and solar system and imagine they are all instantaneously aligned so that their tangential velocities all point in the same direction. Then add that to the velocity at which the Andromeda galaxy is approaching us at. Then imagine a solar system in Andromeda with exact same fortuitous alignment of tangential velocities all the way down to the particle in the particle accelerator.
It seems like the two particles should be moving towards each other at several times the speed of light. But are they actually or is there some weird time dilation thing going on where they somehow actually aren't?
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askscience
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The wind would be caused by the atmosphere stopping. Currently our atmosphere is moving along at roughly the same pace we are, which is why you have calm days. The plane is moving relative to that atmosphere, so if the atmosphere itself is moving 1600+kmph, and plane is moving 500kmph relative to it, and the atmosphere stops, it'll be just like if the plane were traveling through 2100+kmph winds.
This is all based off a shaky understanding of the nature of the atmosphere, so take it with a healthy dose of salt. Someone confirm or correct this please?
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askscience
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>If you're not escaping the Earth right now, then your speed is below escape velocity. The Earth stopping won't make you speed up. Think of it this way: if the surface of the Earth was moving close to escape velocity, then the Earth would be basically flying apart.
But the Earth stopping will make you speed up *relative to the Earth*, which is what's important in that context.
The Earth couldn't escape itself because it can't move relative to itself.
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askscience
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If the dirt was allowed to slosh and slow to a stop our bunker would be smashed flat in a horizontal landslide. There’s no amount of reinforcement that can hold back that much dirt goin 1000 mph.
I was going with te “all of the dirt magically stops at once” because otherwise what part of the Earth “stops rotating” if the dirt can still move?
Just the mantle? Just everything more than x feet down?
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askscience
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Basically, a nuclear attack sub ran headlong into an undersea mountain in 2005 because the charts they were using didn't indicate anything was in the way. Other charts did, but that info didn't make it onto the charts they were using. The captain was relieved of command, six others charged with dereliction of duty, and they nearly lost the submarine. It cost around $79m to fix it, even though it was slated to be retired after 2017 anyway. You'd think that there is some type of fancy equipment to help keep a submarine from running into a mountain, but...
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askscience
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People in planes would definitely have the best chance. The entire plane and people and air would continue in the same direction, so the people in the plane wouldn’t even know what happened at first.
If they could stay above the debris until the entire atmosphere had calmed down, maybe they could survive. I’m guessing it would take weeks, but the wind ripping over a mountain range might make enough of an updraft to keep a plane up without fuel. At least once the air is moving sub sonic.
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askscience
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I don't think you would experience any g force in this scenario. G force is experienced due to acceleration, and your speed has not changed, only the speed of the planet below your feet. The way you would die is being smashed to pieces in the ensuing maelstrom of debris, or as the previous commenter described. Or, if you were lying on the ground, I imagine you would almost instantly become a mile-long smear.
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askscience
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The Earth is a ball of rock with groves filled with water.
If that stops spinning, that water suddenly doesn't have a reason to stay where it is, anymore than a person or object on land would.
All bodies of water would do the same thing a tuppaware full of fluid does if you're transporting it in a car (without a lid, you daredevil you!) and have to suddenly slam on the breaks.
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askscience
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Now, if we weren't to ignore the atmosphere, I believe the first thing you'd notice, other than you're now being flung at up to 1,000mph, is that the air would also suddenly be moving at 1,000mph. To put that in perspective, the fastest hurricane ever was clocked at 190mph. Depending on where you were as this happens, debris would likely rip you to shreds before you even hit the ground again. If you were in your home, depending on the criteria for the earth stopping instantly including structures or not, you'd either splat through the wall as if hit it at up to 1,000mph, or the house would fly apart as well accelerated to 1,000mph.
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askscience
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I had thought that the rotational force of the earth also counteracted it's gravitational pull as well. Much like if you are on the edge of a spinning disc, like a Merry-go-round, you are pulled away from the center of the disc. Is this correct? And if so, once everything stopped moving from the momentum of the earth's rotation, would we all be squished? Or at least heavier than we were when the earth was moving?
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askscience
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Since your trajectory would be tangential to the surface, the ground is at least for a moment, moving away from you. The problem is that it's not falling away from you very quickly, so you'd still be on the ground.
Essentially, it's the same thing as an orbit. You need to be going so fast that the ground falls away faster than you fall toward it. At the Earth's surface, that would require going 17,500+ mph. And you'd only be going 1,000 mph. So, you splat.
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