
Is lightspeed really a limit? Solving super-luminal Special Relativity - ValG
http://www.theregister.co.uk/2012/10/10/ftl_special_relativity_mathematics/
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reasonattlm
If you can engineer transmission of information faster than the speed of
light, you can violate causality. On a small scale, that means acausal
computing in which results can be generated before inputs, thus allowing for
infinite processing power per unit time. On the large scale, outright paradox
in the form of event chains that prevent their origination. These outcomes
would be problematic to account for in our understanding of physics, to say
the least, and seem like a better argument than others for assuming that FTL
and all things that would enable it (e.g. sufficient amounts of negative mass)
cannot exist.

It remains an interesting challenge to prove that more rigorously, of course.

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jbattle
Isn't this just an argument against inconvenience? I.e. "If this were true, it
would make other math, etc very difficult".

The same argument could have been waged against the heliocentric model.
Occam's razor is not a natural law after all.

~~~
zheng
Except that the heliocentric model greatly simplified calculations. Take a
look at Ptolemy's (and others) many epicycle model for something super complex
and still not very accurate.

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fmoralesc
This only shows (it seems) that relativitic physics (meaning physics where
some form of relativity holds, not necessarily einstenian special relativity)
can be accomodated for the possibility of speeds faster than _c_ , not that
this possibility actually holds.

So the question still stands; only the argument that lightspeed is a limit
because it is incompatible with relativistic physics should be abandoned
(stated like this, it seems a fairly weak argument anyway).

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jlebrech
I never really understood why the speed of light was the limit. If you double
your speed, you just halve the time it takes you to get there. Now if you have
reached the speed of light, doubling the speed will never make you go back in
time, it will just halve the time it takes you yet again. So now one lightyear
at the speed of light will take 6 months at twice the speed of light. The
energy requirement for going faster than light is another matter.

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bcgraham
If you were actually going the speed of light, all travel becomes
instantaneous from your reference frame.

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y0ghur7_xxx
Why is 299.792.458 m/s instantaneous from your reference frame? Like the OP, I
don't understand.

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felipemnoa
Within your own frame of reference time slows down the faster you move. This
is why from your own frame of reference light seems to always be moving at c
no matter how close to c you get. Once you get to c time will be frozen. So if
you travel for an entire year at c to you it will look like it was
instantaneous, it wasn't, you could say you were "unconscious" the entire
time. Somebody from a different frame of reference will notice you traveling
at the speed of light and will notice that you are frozen in time.

~~~
capnrefsmmat
Careful. Within your own frame of reference, time always progresses at a
normal rate. When you are traveling near the speed of light, distances
contract; at the speed of light, all distances in the direction of travel
would be zero.

On the other hand, someone stationary watching you travel near the speed of
light would say that your clock slows down more the faster you move, but
lengths stay the same.

~~~
felipemnoa
>>Careful. Within your own frame of reference, time always progresses at a
normal rate.

You are correct. I don't think I said otherwise. I guess I should have been
clearer, time slows down in the frame of reference traveling at c when looking
at it from a different frame of reference. I'm sure we are saying the same
thing.

>>at the speed of light, all distances in the direction of travel would be
zero.

Yeah, but a person observing you in a different frame of reference won't see
that. The fact that distances are zero is just another way of saying that time
has slowed down in your frame of reference. Is just two faces of the same
coin.

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capnrefsmmat
> The fact that distances are zero is just another way of saying that time has
> slowed down in your frame of reference. Is just two faces of the same coin.

Indeed. You can see this sort of effect in, say, the muon decay demo in my
relativity simulator:

<http://www.refsmmat.com/jsphys/relativity/relativity.html>

The muon decay lifetime observations can be explained equally well in terms of
time dilation or length contraction.

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augustl
I recommend reading this reddit comment for a great explanation of why "faster
than light" doesn't make any sense:

[http://www.reddit.com/r/askscience/comments/fjwkh/why_exactl...](http://www.reddit.com/r/askscience/comments/fjwkh/why_exactly_can_nothing_go_faster_than_the_speed/c1gh4x7)

Essentially, it makes no sense because "faster than light" translates to
"faster than as fast as you can possibly travel".

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ars
That's a tautology and explains nothing whatsoever.

All you've done is explained a word by simply repeating it.

The reddit comment doesn't explain anything either - as the very first comment
under it says.

If you want an actual accessible explanation see my comment:
<http://news.ycombinator.com/item?id=4637451>

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ars
It should be noted that this is a mathematical paper, and may have no basis in
reality.

Just because you can calculate something, doesn't mean it actually exists.
(Although the fact that it does sometimes exist is one of the true wonders of
the world.)

This is also true of the Alcubierre drive that was in the news a little while
ago: It's a mathematical solution, but my have no basis in reality.

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nfg
Previously: <http://news.ycombinator.com/item?id=4630460>

~~~
ValG
my b, didn't see it.

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jpxxx
Yes. Next?

