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Drift velocity (explained to me as how fast the electrons are moving) is really slow. My book says the electrons move at around 10 mm/ s.
If electrons move so slowly how do circuits work so fast? If you make a basic circuit with just a light bulb, the bulb lights up almost immediately after you connect the wire to the ... |
How can it be shown without using the little group formalism?
Let's have the Wigner's classification for the irreducible represetation of the Poincare group. For the massless case the eigenvalues of two Casimir operators of the group, the squares of Pauli-Lubanski operator and momentum operator, $\hat {W}_{\alpha}W^{\a... |
I know matter and antimatter annihilation release a lot of gamma rays which are considered ionizing radiation if I am not mistaken. But what if the explosion happened on the surface of the earth, would the the material taken into the fireball cause fallout afterwards ?
My question in another form, what causes fallout ?... |
This is a question based on concepts of two dimensional motion . Here's how the question is:
A plank A is floating in air, gravity has no effect on it (See its coordinates in the figure attached). At $t=0$ plank starts moving along the x-axis with an acceleration of $1.5 \ \mathrm{m/s^2}$. At the same instant a projec... |
How can I determine the needed initial velocity to make a 2d wind resistance free projectile (in computer simulation) reach maximum height at a certain x distance away, with launch position and target position on uneven ground?
|
If I have a projectile shot in a vacuum-box that has no gravity or wind resistance inside it (lets say the box is 1000 units tall and 1000 units wide), with the only rule being that the projectile bounces off the sides of the box how do I solve for the angles that will hit any target inside the box from a projectile la... |
I've often seen the Casimir effect cited as a source of negative energy/exotic matter with regards to ideas like the Alcubierre drive. The articles then go on to note that the energy required by the Alcubierre drive is orders of magnitude more than that produced in theory by the Casimir effect.
Fair enough. What I have... |
So there has been talk in the news of a star named Methuselah that is "older than the universe". Moreover, this star happens to belong to our very own Milky Way.
The article mentions that Methuselah is consistent with universe age estimates if we consider the margin of error, but this would seem to imply (statisticall... |
Is there a way to let water pour out of bottle without letting air inside? i understand that air needs to enter the bottle to ensure water flow, but i do not want to the water to be exposed to air. Can this be achieved without any sophisticated equipment?
|
Peskin and Schroeder say that the Ward Identity of QED proves that non-transverse photon polarizations can be consistently ignored, but I'm confused about the details.
Setup
One starts by considering some process with an external photon whose momentum is chosen to be $k^\mu=(k,0,0,k)$ and let the two transverse polariz... |
I have just read one paper ( Phys. Rev. E 54, R5885 (1996) ) where it was mentioned that the broken-sublattice-symmetry (BSS) phase was stable in the whole low-temperature region. The BSS phase at very low temperatures can be described by $p_{1,A}=1$, $p_{2,A}=p_{3,A}=0$, $p_{1,B}=0$, $p_{2,B}=p_{3,B}=1/2$, where $p_{... |
Electrons have spin 1/2, and as they are charged, they also have an associated magnetic moment, which can be measured by an electron beam splitting up in an inhomogeneous magnetic field or through the interaction of the electrons's magnetic moment with an external magnetic field in spectroscopic measurements.
On the o... |
Displacement correlation functions in question are within harmonic approximation and are derived for example in: A. Maradudin, Dynamical properties of solids 1, 1 (1974). Maradudin says about the displacement time correlation functions that: "The physical interpretation of these correlation functions is simple only in ... |
I know Lorentz force don't do any work. but I want to know whether any type of magnetic field do a work or not.
|
I just watched "Man of Steel", and I'm wondering if my logic is correct.
Let's assume Superman is 80 kg. The energy required to take off from the rest to reach the speed of sound in air (if I neglect the drag) is:
$E_k = 0.5mv^2$ = $0.5\cdot80\cdot340^2$ = $4\times10^6 \ J$.
Also add the potential energy at height $h$,... |
For example:
$Xe^{+}+e^{-} \rightarrow Xe + \mbox{energy}$
Assuming that the electron has a kinetic energy $\neq 0$.
Is the released energy a photon or heat?
|
As we know a solenoid is considered as a electromagnet(magnet) if there's a current flowing through it. if a soft iron core is placed inside the solenoid, the former get magnetised. Consider the solenoid as a hollow bar magnet, and the magnetised soft iron core inside as a bar magnet. The poles of the magnets next to e... |
I have some questions with string theory:
Why is it that there is exactly 4 large spacetime dimensions while the rest remain small?
It is a nonlocal QFT. How could that fit in GR?
|
My daughter and I found a box of old transparencies (clear plastic sheets) and something struck me as odd: even though each transparency is clear, the whole stack of transparencies looks whitish - why is that?
|
I'm just starting to learn physics and I have a question (that is probably stupid.)
I learned that energy levels that the bound electron can have are discrete. I also learned that when an electron transitions from one level to another, a photon with a specific wavelength (energy) is created and released into the wild.
... |
On the top of the fourth page from here, the author trivially derives the components of angular velocity, expressed via Euler angles of the system. I fail to understand how the components of angular velocity were derived. May you please enlighten me!
|
Well, I do not believe that Earth is flat, but I met some conspirationistas believing that all physics we learn in school is twisted, all the Earth's pictures from space are photoshopped by NASA, etc, etc.
So those guys wanted to put a satellite into orbit, take some pics, and see for themselves.
Of course, a satelli... |
I was going through the Wikipedia page for Accretion disks, and I couldn't comprehend what the meaning of this is:
"If matter is to fall inwards it must lose not only gravitational energy but also lose angular momentum."
What does that mean? Also, why are these accretion disks planar? I learned that the reason is con... |
Even at the core of the sun, the temperature of $\sim 10^7$ K only results in $kT\sim1$ keV, which is about a thousand times less than the electrical potential energy of $\sim1$ MeV needed in order to bring two hydrogen nuclei to within the ~1 fm range of the strong nuclear force. Therefore nuclear fusion reactions can... |
My understanding of relativity isn't very sophisticated, but it seems to me that relative to a photon moving at the speed of light, we are moving at the speed of light. Is this the case?
|
Can one understand Newton's law of gravitation using the holographic principle (or does such reasoning just amount to dimensional analysis)?
Following an argument similar to one given by Erik Verlinde, consider a mass $M$ inside a spherical volume of space of radius $R$.
The holographic principle says that the mass $M$... |
If you drop a really heavy ball the ball's gravitational potential energy will turn into kinetic energy.
If you place the same ball in the pool, the ball will still fall. A lot of kinetic energy will turn into thermal energy because of friction, but the gravitational potential energy will still be converted.
Similarly,... |
If you have a sphere covered in electrons, and you connected a copper wire to it, what would happen?
The copper wire's other end is not connected to anything and assume that the copper wire is neutral.
Normally, if the copper is connected to a positive terminal, a wave would be created and it would pushed towards the p... |
There are many "gravity hills" throughout the world
http://en.wikipedia.org/wiki/Gravity_hill
I just visited one here yesterday in Burkittsville, Maryland: http://www.roadsideamerica.com/tip/600 There I put my car in neutral, and my car rolled uphill. I also spilled water on the ground, and the water traveled uphill.
... |
Why is electron spin quantized? I've seen the derivation for the Hydrogen atom's energy levels, but my professor jumped to electrons having spin 1/2 or -1/2 as experimental. Why do electrons obey the same quantization rules for angular momentum as the Hydrogen atom does? Why must the two states be one apart?
|
I learned last semester that a Faraday cage shields people (among other things) from getting electrically shock, say, from a tesla coil. This was well demonstrated in lecture so I believe it.
The person was in a Faraday cage made from chicken wire (i.e. it was full of holes) so why did the Faraday cage "shield" the p... |
That is, the quanta are in bound states where there are least upper bounds and greatest lower bounds to their energy states but there are at least a countably infinite many energy levels they can assume? I'm particularly interested in examples of entangled systems with this property. Any physical examples that can be c... |
Are earthquakes getting less frequent across the centuries? I know that more seismic stations have register more earthquakes in the last century, but that doesn't imply there were more. I am interested on the geophysical side of it.
The logic is that things settle down, so there is less stuff to shuttle. Add to it that... |
In P. Di Francesco, P. Mathieu, D. Snchal they fix the generators of the conformal group acting on a scalar field by somewhat arbitrarily defining
$$\Phi'(x)=\Phi(x)-i\omega_a G_a\Phi(x)$$
and by arbitrary I mean the sign. The "full" transformation would then be given by the exponentiation
$$\Phi'(x)=e^{-i\omega_a G_... |
I've seen the rings from powder diffraction images, and I read that each line is made up of a lot of dots, I was wondering if these dots are reciprocal lattice points of the structure. And if we weren't looking at a powder but just a 2D hexagonal lattice, then the xrd pattern would simply be its reciprocal lattice?
|
Considering that all frames are equivalent, isn't it up to the observer to say "The earth turns around the sun" or "The sun turns around the earth"? Isn't this more or less like arguing about which meridian should be considered the null-meridian, or whether time should be counted according to years before/after Jesus C... |
It seems there is a term called "center of gravity of a band" in solid state physics or chemistry which I'm confused about. Could anyone give a formal definition of the term or point to some reference that have a clear explanation of it's meaning?
|
I was just reading about quantum entanglement and the example was the Double-Slit Quantum Eraser Experiment. Then this was used as a basis for saying that particles might be half a universe apart and still be just as connected.
So I was just wondering if entanglement experiments have been done to show that this is rea... |
I am preparing for my quals and stumbled across the following problem, and although it only requires undergraduate-level physics, I feel I can't piece everything together.
"A rocket of mass $m_0$ is propelled by a giant monochromatic laser mounted on the back of the rocket. The laser emits a beam with a power of $P_0$ ... |
There has been a long discussion between me and Anna V on if the products of the annihilation will really cause a fireball to form and we haven't settled it yet.
Our point here is that gamma rays from the annihilation are too energetic to be absorbed by the atmosphere in a short time or a little space to actually creat... |
In physics text books, it has only stated that Earth cooled down and so, water vapour condense and other life form develop and et cetera. But, why did Earth cooled down in the first place? What caused it to cool down?
In addition, when the Earth cooled down, did the water vapour condense to possible 'raw' magma/lava a... |
In particle physics, where does the term 'neutral current' originate? An example would be an electron exchanging a Z boson with another electron. I understand that the Z boson itself is neutral, but surely 'current' refers to electron and its associated amplitude in this case?
|
I did an experiment on pendulum motion and in the method it says use the following equation to measure the velocity of the pendulum:
$$v=\frac{W}{t}$$
where $W$ is the width of the pendulum bob and t is the time.
Why is this? Is it correct?
Edit: the time is for the bob to cross the photogate.
|
Two person, $A$ and $B$, each holding one end of a long solid rod.
Now person $A$ pushes the rod on one end.
Question:
Is it correct that the information that the rod has been pushed will travel to the other end at the speed of light whereas the actual 'push' will travel at the speed of sound in the rod?
i.e. If the... |
How much speed is maintained in a 90 degree turn? Is there an equation for this? I was recently driving and took a 90 degree turn while coasting at 25 mph and it did not seem like I lost very much speed. Which made me wonder what the equation was for this, does it depend on the momentum of the object?
|
I have to do an experiment to find out the radius of curvature of a lens using the Newtons ring method given that you know the wavelength of the monochromatic light used in the experiment.
What the question is that why we are using the Newtons ring when we have a spherometer available which expects the answer that the ... |
Strain or stress can be caused by different sources. I categorized theses sources as mechanical, thermal and electrical loads and formulated the total stress as follows:
$$
\epsilon_{total} = \epsilon_{mechanical} + \epsilon_{thermal} + \epsilon_{electrical}
$$
I know that the thermo-mechanical stress-strain relationsh... |
Some say we live in the golden age of the universe because there exits countless number of stars that shines in the dark universe. As the supply of gas for star formation is steadily being exhausted, it is estimated that star formation will cease in 100 trillion years.
Question: Will there be a day that the universe be... |
Reflection and transmission (Fresnel equation) of polarized light are treated in many optics or electromagnetism books.
If $E_s$ and $E_p$ is incident electric field with s-polarization and p-polarization, respectively, reflected electric field would be $E'_s = r_s E_s$ or $E'_p = r_p E_p$, where $r$ is reflection coef... |
Like in the title. With E-ELT we are pushing the limit of what we can build on the ground. With JWST we are pushing the limit of what can we launch into space.
So instead, why don't we launch tools and materials to build a telescope and polish its mirror in orbit? This has several benefits. The environment is vacuum a... |
We can see diffraction of light if we allow light to pass through a slit, but why doesn't diffraction occur if we obstruct light using some other object, say a block? Why are shadows formed? Why doesn't light diffract around the obstruction as it does around the slit?
|
I have a friend who has just show me his medical prescription for hyperopia (farsightedness) correction and he needs glasses with 4,25 diopters for that, which seemed to be weird for me because I had learned, from the mirror equation, that the maximum correction possible for hyperopia is 4 diopters:
$$
\frac{1}{f} = \f... |
Just a simple question. Why is it, that when a material becomes superconducting, and by that gets zero resistivity, the electrons don't hit impurities in the material?
For the material to have zero resistivity, that means that the electrons can just flow without any disturbance at all?
Is it because of the Cooper pair ... |
Why is the cosmological scale factor (expansion rate of the universe) not simply the time $t$, i.e. the age of the universe?
|
My question boils down to this. If the Universe was contracting the stars closer to the center would move faster to the middle than stars that were further away from the center.
That would also produce a red doppler shift. So why is it that the red shift is always linked to expansion? Human optimism?
Thanks,
And... |
Shown below in the diagram are two conducting material connected to a battery source and vacuum OR air is in between them. There will be charges developed on their surfaces. I am interested in finding out the pattern of electric field lines.
Suggest the method to arrive at the equation for the field lines or some soft... |
Actually I have some troubles to understand what this principle is all about, so I want to use the simple pendulum in order to get the idea. Since I have read a few passages that dealt with this concept, I would ask anybody who wants to help me, that he tries to answer my questions instead of rather talking about this ... |
By high energy gamma rays I mean 10+ MeV to 100 MeV. Is there a way to calculate it ?
Also, at these high energies, do heavier elements like Lead for example still have the advantage over lighter ones like Aluminum ?
|
The NY Times article on Firewalls today has the following paragraph:
Quantum field theory is how the world works [quoting a physicist]. It had a major triumph just a year ago, when the Higgs boson, a subatomic particle responsible for the mass of other subatomic particles, was discovered after a 40-year search, at the... |
I've recently restored my interest on theoretical physics (I have a master degree in Electrical Engineering) and began my study with first volume of the Physics Course by Landau and Lifshitz. This is a very good and interesting book, and it just blows my mind (both in a positive and negative ways) - you spend really a ... |
There have been several Phys.SE questions on the topic of zero modes. Such as, e.g.,
zero-modes (What are zero modes?, Can massive fermions have zero modes?),
majorana-zero-modes (Majorana zero mode in quantum field theory),
path-integral-with-zero-energy-modes (Path integral with zero energy modes), etc.
Here I wo... |
How can one go from the 3D compressible Navier-Stokes equations to the simpler Euler equations, Bernoulli's equation and other fluid dynamic equations?
|
I don't know how to explain the issues at hand in a way that nonphysicists are certain to understand. Can anyone point me to some resource (book, video, it doesn't really matter) that will help me?
|
In "String Theory and M-Theory" by K. Becker, M. Becker and J.H. Schwarz, page 222, they give a brief introduction about the (space-filling) Orientifold Plane $O9$ as an object needs to be add in the theory to make the it consistence (or at least, that what I thought). However, I still don't really get their arguments.... |
How can an object that's not accelerating cause another stationary object to move in a collision? This website: http://www.physicsclassroom.com/Class/momentum/U4l2a.cfm, says that a "rightward moving" 7-ball experiences a leftward force when it hits an 8-ball, and the 8-ball experiences a rightward force, but where is ... |
Topological entanglement entropy (http://arxiv.org/pdf/cond-mat/0510613.pdf, http://arxiv.org/abs/hep-th/0510092) is usually calculated for surfaces with boundary. How would it look like for compact surfaces and when these are punctured?
|
Leon Crux invented the concept of interlocking archimedes spirals that eventually led to the scroll compressor but intended it to be used as a rotary steam engine. However technological limitations of his day prevented the rotary steam engine from being built. Has one ever been built? What type of efficiency would one ... |
Ultraviolet light can cause electrons from Hydrogen gas to jump from a lower energy orbit to a higher energy orbit. What causes the electrons to return from the higher energy orbit to the lower energy orbit by releasing photons? Would it be possible to maintain the electrons in the higher energy orbit? How? Would placi... |
$W$ bosons decay into an electron and electron-neutrino
or into a muon and muon-neutrino. The $W$ lifetime is about $3 \cdot 10^{-25}\ \rm s$. That means the decay occurs close to the collision point, not in a detector.
The energy of the resulting electron or muon can be measured
quite accurately, but for the neutrino ... |
I was just reading a book - Mirror Symmetry by Clay Mathematics Institute, and on Page 402 of the book, the writer says that energy momentum tensor is defined classically by $$\delta S = -\frac{1}{4 \pi} \int \sqrt{h} d^2 x \delta h^{\mu\nu}T_{\mu\nu}$$ and quantum mechanically by $$\delta_h \langle O\rangle = \left\la... |
I know the products of the annihilation, but I don't know how much energy each particle has or gets. For example I know that 1876 MeV is released for each annihilation. Now, this energy is distributed among a number of pions, so how much energy does each pion get ?
Also, this energy is distributed between kinetic and r... |
In strong nonequilirium, the statistical operator describing the system depends on an infinite number of variables (BBGKY-hierarchy), contains information about all the previous states starting from an initial condition $\rho(t_0) = \rho_{rel}(t_0)$
$$
\rho(t) = \frac{1}{1-t_0}\int\limits_{t_0}^t \exp^{i(t_1-t)L}\rho_{... |
I was watching this video on YouTube of a high school student explaining perception in different dimensions, basically stuff he learned from reading the book Flatand.
At one point in the video, he says that as 3-dimensional beings, we can't really see our 3-dimensional world in the 3-dimensional way it actually is, bec... |
Zurek 2001 is a review article on decoherence in quantum mechanics. Equation 5.36 on p. 24 gives an estimate of the decoherence time, which I'll paraphrase as follows:
$ \frac{t_D}{t_R} = \left(\frac{\lambda_T}{x-x'}\right)^2 $ .
My attempt to interpret the meaning of the variables is:
$t_D$ is the decoherence time
$t_... |
Consider the formula for the total time-derivative of a physical value in Poisson's formalism:
$$\tag{1}
\frac{dA}{dt} = -\{H, A\}_{P.B.} + \frac{\partial A}{\partial t},
$$
where $\{A, B\}_{P.B.}$ is Poisson's bracket, and $H$ is the Hamiltonian.
By using quantum mechanics, the equation can be rewritten in the form
$$... |
A while ago, there was some news about micro-scale graphene-based supercapacitors and these devices can charge and discharge a hundred to a thousand times faster than standard batteries.
Question:
Which properties of graphene enables it to charge and discharge hundreds of times faster than standard batteries? Is it bec... |
I want to know how equation 2.11 (page 9) follows from 2.10 (page 8) in this paper.
The two references mentioned just before 2.11 also seem to skip this crucial step. Unless I am missing something obvious everywhere!
It would be great if someone can help with this!
|
At first, I used to think that only circular polarized light has non-zero helicity, linear polarized light has zero helicity, because the linear polarization can be seperated as the superposition of right and left circular polarization which have equal helicity but opposite in sign.
From some articles, I realized I was... |
In compound microscope, we take such an objective lens which has small focal length. While in astronomical telescope, we take such an objective lens which has large focal length.
Why don't we use same objective lens in both? The function of both the devices is to enlarge an object at infinity.
|
In the book String Theory and M-Theory by K. Becker, M. Becker and J.H. Schwarz:
Why is the potential for moduli given by eq (10.168):
$$\tag{10.168 }V(T,K) ~=~ \frac1{4\mathcal{V}^3} \Big( \int_{CY_4} F \wedge \star F - \frac16 \chi T_{M2} \Big)?$$
Maybe the answer of this question is trivial, but I cannot see how $... |
Nonlinear field theories contain a large number of localized solutions.
I have found this text in a article. What I don't understand is "what is localized?". Is it refer defining position of a particle or a wave?
Can someone give me an elaboration with example?
|
First, I apologize for being a mathematician and having no scientific background in physics. The following questions on color came up in a discussion at lunch and I would be very happy to get some answers or corrections of my understanding.
The first question is, what a color the human eye can see is in the first plac... |
Is the following a possible scenario? If not, why not?
Assume there is a supermassive black hole $Z$ isolated in inter-galactic space.
Nearby and stationary relative to $Z$ is observer $A$.
A number of light years away spaceship $X$ is travelling at, say, $0.25c$ directly towards the black hole and (eventually) $X$ fal... |
For the observation of solar or galactic gamma rays, one should ideally be above the atmosphere. Quoting the Wikipedia article on Gamma-ray astronomy:
Most gamma rays coming from space are absorbed by the Earth's atmosphere, so gamma-ray astronomy could not develop until it was possible to get detectors above all or ... |
Chirality can be interpreted as a property of Lorentz group - Lorentz transformation of field through representation $(s, 0)$ or representation $(0, s)$. For the massless particles one says, that chirality and helicity are the same (helicity values are a chirality values multiplied by $ \hbar $). So it means, that chir... |
In eternal inflation, how can bubble universes collide if the space between them is exponentially stretching and moving them further and further away?
|
I know that air pressure and temperature are inversely proportional.
Now I saw in a book that "Atmospheric pressure decreases as we go higher and higher."
But at greater heights the temperature becomes low, and so the air pressure would be high.
But it is given atmospheric pressure decreases with altitude. I understan... |
What follows is a long self-made example to deal with my conceptual issues of visualizing curved spacetime.
Imagine an observer floating somewhere in space.
He feels no strain on his body, indicating he is free-falling and is thus moving along a geodesic.
He is a magician and has the power to conjure up glowing sticks... |
From Wikipedia: The work done by a constant force of magnitude F on a point that moves a displacement d in the direction of the force is the product:
$$W = Fd.$$
If I lift some object from a ground, the force to be put in above equation is the gravitational force $mg$.
But while I am moving the object upwards, against... |
Wick rotation to thermal of QFT in Minkowski space to thermal QFT, which is after this transformation analogue to statistical mechanics, does only describe equilibrium statistical mechanics. On page 227 of this paper it is said, that for dynamical questions beyond the equilibrium properties, the time coordinate has to ... |
I have a rather fundamental question about the Buckingham $\pi$ theorem. They introduce it in my book about fluid mechanics as follows (I state the description of the theorem here, because I noticed in my search on the Internet that there are many different forms of this theorem) :
if we have a physical relation betwee... |
I'm not so technical and not very good with physics, but have some idea based on observation and I believe it is doable.
As everyone know also this subject was repeated many times in here,
Sending stuff to space is very expensive. But what if there is an easy way to do that only if we would think out side the box.
So... |
I'm not sure if this is the appropriate forum for my question as I actually am studying this as part of electrical engineering and I don't actually study physics. Nonetheless, I shall ask and if need be, move my question to another venue.
My question is with regard to how complex permittivity is defined. According to... |
When analysing powder diffraction patterns, the broadening of peaks can be used to estimate crystal sizes. Smaller crystal size gives larger broadening according to the Scherrer equation:
$$ \beta = {{K\cdot\lambda}\over{D\cdot\cos \theta}}.$$
What is the physical origin of this effect?
Edit:
Added homework tag as this... |
There are some things I encountered, studying the Bernouilly equation, that I don't understand. I was studying in the following book: http://www.unimasr.net/ums/upload/files/2012/Sep/UniMasr.com_919e27ecea47b46d74dd7e268097b653.pdf. At page 72-73 they derive the Bernouilli equation for the first time, from energy cons... |
In his The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics (p. 373) Susskind states that
the entropy of a string is [...] proportional to its length. Imagine moving along the string as it turns and twists. Each turn and twist is a few bits of information.
(The context doesn... |
I was reading this paper by West, in which it is argued that:
Eleven dimensional supergravity can be described by a non-linear realisation based on the group $E\left(11\right)$
From which they conjecture that $ E\left(11\right) $ can be related to M-theory, too. This seems rather weird to me, given that ... |
There is 'End-Centered' Orthorhombic lattice . Why this type is not in 'Cubic' lattice ? On which basis did Bravais propose his theory ?
|
Humans are born and they die. When we are born, is energy created? Or is it just some amount of energy that our mother gives us? Doesnt she take this energy from the surroundings? If so, then when we die, where does this energy go? It can not be destroyed.....
Just as an example to make this clear, if there is a fat ma... |
I see there are many questions with this title, but this one is different, so please give it due thought:
Is time travel possible? If so, Can we go both forwards and backwards in time?
Paradox:
I am studying for a very competitive exam, wherein I must put in a LOT of effort to hope for any success. Now, I am lazy. And ... |
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