# Tag Info

1

I've been playing around with a concept for this for a while now. I call it Paradox Shadow. One-way FTL would be a subset of this, and I think you're correct that it should work without causing time travel. FTL violates causality due to relativistic time dilation. In other words - FTL would be fine if everything in the universe was at rest to everything ...

2

In special relativity particles that move faster than the speed of light are commonly called Tachyons and there is some research about the properties of such particles. Nevertheless, most physicists regards them as unphysical, because their proper time is imaginary.

2

No, because of the large scale. Doing things like this only seems instantaneous. The speed of a push on this object is actually the speed of sound in the object.

1

It will maintain its speed. It's the same as every other object. Also, making it reach the speed of light will take infinite energy. If you actually calculate out the amount of energy to go slower, you get a complex number.

0

What if you had a proton travelling at .99999c towards a heavy object? Would it have to keep accelerating or would the acceleration of the proton slow down to zero and only it's mass would increase? It would keep accelerating, but there's a problem. See what Einstein said in the second paragraph about the speed of light being spatially variable: The ...

0

Good question. Although the speed of gravity is approx. 3x10^8 meters per second, the acceleration at the Earth's surface is as you describe ~9.8m/s^2. If you choose the Earth as the heavy mass your proton in question is approaching, and forgo magnetic influence, then you would realize that the increase in acceleration is negligible as compared to the ...

0

In order for that proton to reach the speed of light, it would need an infinite amount of energy. Perhaps if the proton reached the center of a black hole, converging with the singularity, it would cease to accelerate, but it would not travel neither faster or at the speed of light.

1

You should look at it like an asymptote. Yes the proton would accelerate but it would probably accelerate to .999991c or more likely less due to the massive energy required to accelerate something so fast already. Therefore you could always keep accelerating your particle but it would never cross the Light-Barrier.

0

To have particles that move faster than light requires violations of Lorentz invariance. So, to investigate the effects of this, one first needs to build a model in which Lorentz invariance is not an exact symmetry that is consistent with the known physics. This has been done here. Vacuum Cherenkov radiation is then indeed a predicted effect if charged ...

-3

If light(to be taken here) travels @ a velocity >c, you won't be able to see or apprehend it. So, you need an observer having a relative velocity =

0

See,the philosophy of relativity is that all the observers will agree with the natural phenomena, or what is happening; like, if one observer sees two particles to collide or a lightning causing damage then all the observers will agree with the collision and lightning causing damage. But there will be disagreement in positioning and timing (and in interval) ...

0

Special Relativity is based on two assumptions: any reference frame (viewpoint) is valid and light moves at the same speed in all reference frames. In the first picture picture, light is trapped between two mirrors. If the distance is 300,000m then it takes 2 seconds to go up and down. As you can see, when the mirrors moves (with the light) it makes a ...

0

What matters in principle is not if information can travel faster than c, rather if this leads to causality violations. As pointed out in this article, the Scharnhorst effect is the only known effect where light is expected to travel faster than c. However, in that case you cannot use this to create a causality paradox.

2

The local speed of light is always $c$. Local in this sense could mean that for each observer there exists a neigborhood of that observer such that, if we call $v_c$ the "observed speed of light", $|v_c - c| < a$ where $a$ is arbitrarily small. However $v_c$ is a slightly nebulous concept as beyond the inertial frames in special relativity, there ...

4

This is yet another instance of taking the ubiquitous balloon analogy too far. See, while it's a wonderful way to express the expansion of the universe, there are some misconceptions that arise from it: We live in a universe of finite size (we don't know, but we think not) and non-zero curvature (according to WMAP, we don't, or at least we think we don't) ...

0

If you mean by "our universe" the matter in spacetime we are able to reach and observe then you are right. The universe will become more and more finite for us unless someone will invent a "warp drive" or "wormhole" (currently the probability for it is very low). According to research you have ca. 100bn years time before all others galaxies will be gone ...

2

Galaxies are not moving away from us, it is the space between us and the galaxies (and everything, in general) that is continually expanding. This is allowed to happen faster than the speed of light, because no object actually crosses the light speed barrier in the process. So consequentially, the universe has no size constraint like the one you've stated.

0

The short answer is: in ultra-deep gravity wells one has to bring relativistic considerations into the picture. The result of this is that an 'event horizon' forms in ultra-deep gravity wells such that an observer looking from a distance into the gravity well can only look till a finite depth. In loose terms, that specific finite depth corresponds to the ...

0

Without invoking relativity, let's look at energy. The force of gravity between two objects goes as $$F= \frac{GMm}{r^2}$$ Which implies that the force is weaker when you are far away and stronger when you get closer. potential energy is the integral of force, and we know the sum of potential and kinetic energy is constant. Putting potential energy =0 at ...

2

You make two wrong assumptions in your question, namely that if an object is accelerating the velocity would keep increasing ad infinitum without limit, and that the acceleration due to gravity on earth is always $9.8 m/s^2$ these are both not the case. First of. The theory of relativity doesn't allow for objects that have mass to go faster than the speed ...

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