A theory about travelling faster than light ...

[Gilles]

So we agree we can never travel faster then light,

But we can't even approach the speed of light, we can't even get closer to it, for it will allways be c, relative to us.

The point of the relativety theory is that we don't talk about absolute speed, but a speed relative to the observer. Where an observer can't see you go faster then 300 000 km per second, you, with that speed, haven't nearly reached the speed of light, and are still able to accelerate.

With that, your mass increases, and so does the mass of your fuel. Without breakings (consider vacuum), you will still be able to use the fuel, to gain speed.

The only thing we have to be carefull of is that our mass doesn't get so high that we start atracting rocks and stuff, unless we use those as fuel to accelerate. The point is finding a balance between not destroying too much of the universe by travelling through it, and travelling.

Offcourse, I'm not talking about tomorrow here...

[jinydu]

With that, your mass increases, and so does the mass of your fuel. Without breakings (consider vacuum), you will still be able to use the fuel, to gain speed.

As you pointed out, in relativity, we talk about relative speeds, not absolute speeds. Has your mass (and that of your fuel) really increased? In your frame of reference, no. In that other observer's frame of reference (in which you are moving at a very high speed) yes.

[Batman3]

An obervable tachyon would have to have negative, imaginary mass since the square root in the denominator of the mass eq'n would be imaginary. So the rest mass would have to compensate. So if a tachyon collided with an real particle and stopped, it would disappear while the real rest mass particle would acquire imaginary energy and disappear too,unless ts rest mass was imaginary and hence invisible.
For us, though, to get from <c to >c , we could not go through v=c but around it into the imaginary dimension and back. With complex values for velocity and position. A complex number is the sum of a real number and an imaginary number. An imaginary number is the product of a real number and the square root of -1.

[PWrong]

I've been learning relativity in physics for a couple of weeks, and I had a problem with a particular question on length contraction.

A particle is moving towards a planet at 0.98 c. The planet measures the distance between them to be 45 km. What is the distance as measured by the particle?

The answer was 45 km / gamma = 8.95 km. It seems pretty obvious.
But think about this question.

A planet is moving towards a particle at 0.98 c. The particle measures the distance between them to be 8.95 km. What is the distance as measured by the planet?

It's the same question, reversed. The problem is completely symmetric (except the sizes of the observers, but you could have a similar problem with two same-sized objects). So is the answer 45km, or 1.782 km?

I asked the guy who marked it. He understood what I was saying, but he couldn't explain why I was wrong. Can anyone here explain it?

[jinydu]

Hmm, good question... I guess you could try asking a physics expert about that one.

By the way, why haven't you replied in the "extra time derivatives" thread, PWrong?

[moonlord]

If the universe was 4d then it would be possible to go from A to B in a time less than d/c without necessary going faster than the light, assuming the 3d is curved ('A Brief History of Time', ch. 10). Or am I wrong? thanks in advance.

[houserichichi]

The key portion of Hawking's writing is "assuming the 3D is curved." If space is not curved then a straight line would be the fastest way.

("straight" meaning the every day Euclidean version of the word)

[bo198214]

A particle is moving towards a planet at 0.98 c. The planet measures the distance between them to be 45 km. What is the distance as measured by the particle?

I am not at all an expert regarding relativity. But as far as I know the length contraction concerns lengths between points not moving against each other. I.e. constant distances in system A seen from B or constant distances in B seen from A.
If you have changing distances the question is *when* do you measure the distance, you know there is no absolute time either.

Simultaneousness depends on the observer and so your problem becomes unsymmetric, depending on which observer should see the measurement of the lengths at the same time. You can place for example the observer still to A, or still to B, or with same relative velocity to A and B. And in the last case A and B would measure the same distance to each other, when the observer sees their measurements at the same time.

[moonlord]

The key portion of Hawking's writing is "assuming the 3D is curved." If space is not curved then a straight line would be the fastest way.

("straight" meaning the every day Euclidean version of the word)

i totally agree on this, i just thought it has been proven that the spacetime cannot be plane (i.e. having positive curvature if there will be a big crunch or a negative one if not). maybe you can enlighten me on this. thanks.

[faranya]

Now, the question is: Do you even want to travel at the speed of light? If it works like moving at the speed of sound, I wouldn't. If you travel beyond the speed of sound you can no longer hear because you outrun the sound waves. Now, if you could travel at the speed of light, even if you don't go faster than it, you wouldn't be able to see would you? Anyone have any thoughts on this?

[thigle]

correct me if i am wrong, but isn't it true that what relativity theory states is not that nothing can travel faster than light, but that the lightspeed limit cannot be crossed ? i.e. that nothing can accelerate over c if it is moving at v<c, nor can anything pass the c limit from "above": whatever is already faster than light, cannot drop under c.

so, to travel beyond lightspeed, it is not a question of accelerating over c, it is rather a matter of re-attunement to primordial ever-present 'pre-bigBang' state that is underlying space-time dynamics: the ever-present origin, plenum of zero-point energy and infinite inFormation. substrate of space-time dynamics is the self-referential Spin-process - driving quantum mechanics, consciousness and space-time.

to get beyond relativity, it is necessary to understand relativity of relativity.

this is what mahayanists see when confronting reality of relativity:

Form is empty (of projections over its existence).
but Emptiness itself is empty.
So (after all), Form is Form
and Emptiness is Emptiness.

[jinydu]

Your first paragraph makes sense to scientists, so I can comment on it:

http://scienceworld.wolfram.com/physics/Tachyon.html

Unfortunately, the rest of your post doesn't.

[bo198214]

Now, if you could travel at the speed of light, even if you don't go faster than it, you wouldn't be able to see would you?

At least you wouldnt see whats behind you.
But ... thats really possible *waiting for some lowering jaws, then continues*
Particles can move faster than light ... when not in vacuum but in a medium.
Dont ask me how relativity works in a medium.
But its experimentally proven that particles can move faster than light in a medium, they draw a superluminal shockwave like supersonic planes or ships on water (if they are charged).
For the nonbelievers a hint.

@jinydu
Unfortunately your comment does not verify or falsify the statement of thigle because tachyons are for non-relativistic theories, as I read there.

[thigle]

Fortunately, people other than self-proclaimed scientists visit these forums. not all people are looking through 'scientist-first human-second' scheme, and not all people are limited by their languague-formalisms.

back to supraluminal action, what about gamma rays ? how do they fit the picture ? aren't they supposed to be running faster than light too?

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i am not a scientist, just a hobbyist trying to clarify his nebulas of interest.

[bo198214]

what about gamma rays ? ... aren't they supposed to be running faster than light too?

Not that I would know of, just usual electromagnetic radiation :?

[houserichichi]

Gamma rays are nothing more than high energy photons which necessarily travel at the speed of light.

Sorry for being so blunt - I didn't know what else to write.

[thigle]

very nice. accurate bluntness is healthy.

[papernuke]

that wouldnt work because if the boat was expanded to the size of the universe, first of all it would crash into everything and get badly damaged or destroyed, second, if it was enlarged, then, how would you make it smaller and so that you go to your intened destination in normal size? because if you shrunk it, it would go to the middle of where it started, which would leave you in the same place where you started