# Tagged Questions

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2answers
96 views

### Superluminal particles with causality

What kind of CLASSICAL theories would allow to true (non-apparent) superluminal particles (beyond speed of light, BSOL) agreeing with causality to exist? I mean, are causal superluminal classical ...
0answers
56 views

### Quantum entanglement and speed of light $c$

On the topic of quantum entanglement, Wikipedia states: Repeated experiments have verified that this works even when the measurements are performed more quickly than light could travel between the ...
3answers
77 views

### Mass in special relativity

I have just got a query about how this equation works if its right. We have Newtonian Physics saying $F=ma$, According to the 'Mass in special relativity' the mass changes according to m= ...
1answer
76 views

### Why is this thought experiment flawed: A vast lever rotating faster than the speed of light [duplicate]

If there were a vast lever floating in free space, a rigid body with length greater than the width of a galaxy, made of a hypothetical material that could endure unlimited internal stress, and this ...
7answers
920 views

### Rotate a long bar in space and get close to (or even beyond) the speed of light $c$

Imagine a bar spinning like a helicopter propeller, At $\omega$ rad/s because the extremes of the bar goes at speed $$V = \omega * r$$ then we can reach near $c$ (speed of light) applying some ...
0answers
25 views

### Why is it theoretically impossible to travel back through time? [duplicate]

I know scientist have basically proved the fact that time travel to the future is possible, but persay if on wanted to travel back 30 years, why exactly would this be rendered impossible if we can go ...
3answers
140 views

### Can space expand with unlimited speed?

At the beginning, right after the Big Bang, the universe was the size of a coin. One millionth of a second after the universe was the size of the Solar System (acording to ...
1answer
82 views

### Could the shadow move with faster-than-light speed? [duplicate]

If I make a huge laser with a figure for shadow in front of the laser, and I shine it on to the moon, will I see the light from the laser AND the shadow moving the same speed? (I read somewhere the ...
0answers
84 views

### Status of experimental searches for tachyons?

Now that the dust has settled on the 2011 superluminal neutrino debacle at OPERA, I'm interested in understanding the current status of experimental searches for neutrinos. Although the OPERA claim ...
1answer
445 views

### Neutrinos vs. Photons: Who wins the race across the galaxy?

Inspired by the wording of this answer, a thought occurred to me. If a photon and a neutrino were to race along a significant stretch of our actual galaxy, which would win the race? Now, neutrinos ...
3answers
536 views

### How can neutrinos “beat light”?

Article in the CERN newsletter "symmetry breaking" has the following statement: "Neutrinos are often the first particles to bring news of events in space to Earth, beating even light.". What does this ...
3answers
102 views

### Stuff can't go at the speed of light - in relation to what? [duplicate]

We all know that stuff can't go faster than the speed of light - it's length becomes negative and all kinds of weird stuff happens. However, this is in relation to what? If two objects, each moving ...
2answers
139 views

### Quantum tunneling is faster than light travel?

Quantum tunneling is faster than light travel ? My reasoning is that the particle cannot be detected inside the tunnel so if it travels from A to B it must be instantly going from A to B , hence ...
3answers
312 views

### Can something travel faster than light if it has always been travelling faster than light?

I know there are zillions of questions about faster than light travel, but please hear me out. According to special relativity, it is impossible to accelerate something to the speed of light. However, ...
3answers
388 views

### Does entanglement not immediately contradict the theory of special relativity?

Does entanglement not immediately contradict the theory of special relativity? Why are people still so convinced nothing can travel faster than light when we are perfectly aware of something that ...
1answer
307 views

### EPR-type experiments and faster-than-light communication using interference effects as signaling mechanism

I understand that faster-than-light communication is impossible when making single measurements, because the outcome of each measurement is random. However, shouldn't measurement on one side collapse ...
3answers
154 views

### Is there absolute proof that an object cannot exceed the speed of light?

Have any known experiments ruled out travelling faster than the speed of light? Or is this just a widely accepted theory?
3answers
2k views

### Why is the universe so big?

The Universe is approximately 13.7 billion years old. But yet it is 80 billion light years across. Isn't this a contradiction?
2answers
158 views

### Has anyone ever measured the one way speed of light perpendicular to the Earth at the Earth's surface?

1 - Has anyone ever measured the one way speed of photons traveling perpendicular to the Earth at the Earth's surface? 2 - Given our current understanding of Physics is there any way both the upward ...
2answers
152 views

### Can a dot of light travel faster than the speed of light? [duplicate]

Say I have a laser. If I spin the laser so that the beam sweeps in an arc along a very distant object, could that dot travel faster than the speed of light? In Diagram form:
5answers
420 views

### Special Relativity Second Postulate

That the speed of light is constant for all inertial frames is the second postulate of special relativity but this does not means that nothing can travel faster than light. so is it possible the ...
3answers
505 views

### Special Relativity and $E = mc^2$

I read somewhere that $E=mc^2$ shows that if something was to travel faster than the speed of light then they would have infinite mass and would have used infinite energy. How does the equation show ...
1answer
115 views

### Exploiting the Heisenberg Uncertainty Principle as a means to communicate

It seems as though I've come across a rather unusual conclusion that could either simply be a misinterpretation or a contradictory discovery. I seem to have found a way to utilize the Heisenberg ...
3answers
415 views

### How can a quasar be 29 billion light-years away from Earth if Big Bang happened only 13.8 billion years ago?

I was reading through the Wikipedia article on Quasars and came across the fact that the most distant Quasar is 29 Billion Light years. This is what the article exactly says The highest redshift ...
2answers
237 views

### What if a faster-than-light particle is found?

What will be the consequence (severe ones) on laws of physics if a particle that travels faster than light is discovered? I am looking for a more general answer so that a high school student would be ...
0answers
72 views

### Impulse travelling faster than light

There have been conducted many experiments in which light impulses traveled faster than light like the one in Princeton in 2000. This phenomenon has something to do with quantum entanglement. Does ...
1answer
166 views

### Size of the Observable Universe [duplicate]

I wanted to know what the observable universe is so I was thinking and I thought, it must be age of the universe times 2. Well I was wrong. I found on one website that it is 46B LY across in each ...
1answer
63 views

### What is the age of universe? [closed]

As we know at the time of big bang as mentioned by the scientist the universe expanded faster than the speed of light. So does it mean that at that time all the particles present travelled in the time ...
1answer
44 views

### How the effect travel's? [duplicate]

Let us assume that we placed lot's of ball touching each other in a hollow cylindrical tube, now if we push one ball at the end the ball at the other end move's instantly. So how do the information ...
1answer
221 views

### Relationship between Alcubierre drive space-time evolution and speed of gravity

The top rated answer to this question about the Alcubierre drive asserts, "spacetime can dynamically evolve in a way which apparently violates special relativity," but according to the Wikipedia ...
4answers
751 views

### Double light speed

Let's say we have 2 participles facing each other and traveling at speed of light Let's say I'm sitting on #1 participle so in my point of view #2 participle's speed is c+c=2c, double light speed? ...
1answer
127 views

### Faster than the speed of light and future travel [closed]

I had read somewhere that if a person attains twice the speed of light, he can actually reach the future. But since the world belongs to one time and space, how will it change for one particular ...
0answers
43 views

### Is the speed of light the ultimate speed limit? [duplicate]

As we all know nothing can go faster than the speed of light as mentioned by most of our pioneer's in physics. But as I was listening to one of the statements of Sir. Stephen Hawkins he stated that at ...
1answer
227 views

### Superluminal expansion of the early universe how is this possible?

Is this a postulate? I get the expansion of the universe, the addition of discrete bits of space time between me and a distant galaxy, until very distant parts of the universe are moving relative to ...
3answers
353 views

### How does faster than light travel violate causality?

Let's say I have two planets that are one hundred thousand lightyears away from each other. I and my immortal friend on the other planet want to communicate, with a strong laser and a tachyon ...
4answers
451 views

### Thought experiment regarding an object approaching a mirror

Here's a thought experiment I came up with in class today when my mind drifted (I however highly doubt I'm the first to think about this since it is pretty rudimentary) : Let's say superman ...
1answer
114 views

### Universal expansion faster than the speed of light

If the universe is expanding faster than the speed of light, and force carrier particles move at the speed of light, wouldn't this cause infinite universal expansion? Since no forces would be acting ...
2answers
705 views

### Faster-than-light communication using Alcubierre warp drive metric around a single qubit?

The Alcubierre warp drive metric has been criticized on the points of requiring a large amount of exotic matter with negative energy, and conditions deadly for human travellers inside the bubble. What ...
2answers
304 views

### Does quantum mechanics allow faster than light (FTL) travel?

Let's suppose I initially have a particle with a nice and narrow wave function[1] (I will leave these unnormed): $$e^{-\frac{x^2}{a}}$$ where $a$ is some small number (to make it narrow). Let's also ...
12answers
2k views

### Is it possible for information to be transmitted faster than light by using a rigid pole?

Is it possible for information (like 1 and 0s) to be transmitted faster than light? For instance, take a rigid pole of several AU in length. Now say you have a person on each end, and one of them ...
2answers
686 views

### Is the “How to break the speed of light” minute physics video wrong?

I am referring to this video, on YouTube, by minutephysics, which has quite a lot of views. In the video it states that if you flick your wrist while pointing a laser that reaches the moon, that the ...
3answers
1k views

### Harold White's work on the Alcubierre warp drive

I've read a bit on Harold White's recent work. (A paper on Nasa's site) I haven't been able to find any comments by people claiming to know anything about the physics involved. Is this really serious? ...
1answer
87 views

### Extended Rigid Bodies in Special Relativity

I was reading Landau & Lifhsitz's Classical Field Theory and I noticed that they mention that an extended rigid body isn't "relativistically correct". For example, if you consider a rigid rod ...
4answers
676 views

### In superluminal phase velocities, what is it that is traveling faster than light?

I understand that information cannot be transmitted at a velocity greater than speed of light. I think of this in terms of the radio broadcast: the station sends out carrier frequencies $\omega_c$ but ...
0answers
30 views

### Relatively faster than light [duplicate]

Possible Duplicate: Travelling faster than the speed of light If one spaceship travels in one direction at 3/4 of the speed of light and another spaceship travels in the opposition ...
3answers
91 views

### If neutrinos travel faster than light, how much lead time would we have over detecting supernovas?

In light of the recent story that neutrinos travel faster than photons, I realize the news about this is sensationalistic and many tests still remain, but let's ASSUME neutrinos are eventually proven ...
4answers
2k views

### Einstein's special relativity beyond the speed of light

Could someone with access to this paper which claims to have new transformations between frames with relative motion faster than light which are supposedly consistent with special-relativity, say what ...
0answers
200 views

### Could someone transmit a signal with equally-tuned Casimir plates across the quantum field?

It seems, one could exploit the Casimir effect to send messages across arbitrarily-large distances with carefully-tuned Casimir plates. Obviously, relativity would preclude FTL information transfer, ...
1answer
168 views

### Will acceleration rate of expansion of space become faster than speed of light?

From watching cosmology lectures, it seems that the space between galaxies is expanding at an accelerating rate, my question is since it is the space that is (acceleratingly expanding), the special ...
0answers
37 views

### Far stellar object going away from us faster than light [duplicate]

Possible Duplicate: What does Brian Greene mean when he claims we wont be able to observe light from distant stars due to the universe’s expansion? Since the galaxies are fleeing us faster ...
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