Is lightspeed really a limit?

We don’t (yet) have any way to test this, but University of Adelaide applied mathematicians are suggesting that an extended version of Einstein’s Theory of Special Relativity also holds true for velocities beyond lightspeed. One of the main predictions of Special Relativity is that the speed of light is treated as an absolute …

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Limits.

“'If you really don’t believe that faster-than-light is possible, then humans will be limited forever,' he said".

Humans might be limited anyway; after all, faster-than-light speeds might be impossible regardless of human beliefs.

Re: Limits - "Humans might be limited anyway".

True, but there's a big difference between 'might be' and 'will be', so it's worth suspending disbelief at least for a time.

I find it interesting and encouraging that something may come out of a false experimental result, simply because people were no longer quite so certain of the impossibility of FTL travel.

Re: Limits.

Of course there will be something that travels faster than light.

It's just that it has not been invented yet. Give it a couple of months and you'll see.

Re: Limits.

Yep, first it was the foot, then the horse, the train, the car, the aeroplane, the space rocket.

Humans keep going faster and faster, communication was shouting, smoke signals, lights, bean cans, telephone, wireless radio, fibre optics etc etc.

Someone will,invent it.

Re: Limits.

A shadow can travel (or be perceived to at any rate) faster than light. Not terribly functional mind.

Re: Limits.

A shadow does not "travel" in any sense a reasonable intelligence would accept. Neither does an equation, an idea or a train of thought.

Also, humans limited forever, no-go theorems, N is not NP, Gödel, the age of failed dreams (when we still watched the original Star Trek)

Re: Limits.

Still don't see these scientists point. Einstein was happy for you to go faster than light. You just had to exist as a faster than light particle first. You cannot accelerate things faster than light, because this requires infinite (or greater than infinite) energy.

The opposite applies to objects traveling faster than light AFAIK, you need infinite energy to slow them down.

That's where photons come in, you can't speed them up or slow then down. They always travel at "lightspeed".

Which leaves us with the final comment on the article. Faster than light might be possible, but unless the paper shows it's possible with energy less than infinite, it's all pointless. :(

@Destroy All Monsters - "humans limited forever"

Bugger that!

If true, what's the point in carrying on? We might just as well use genetic engineering to cut our fertility down to a level that allows the human species to gracefully fade away, if we accept that there is no use for our intelligence.

I'll cling on to hope, thanks.

Re: Limits.

Why not suggest going below absolute zero as well (Hint : below absolute zero doesn't mean anything )

Re: Limits.

"A shadow can travel (or be perceived to at any rate) faster than light. Not terribly functional mind."

As can the spot of light from a rotating laser at sufficient radius - but it's not the same as FTL

Re: Limits.

They always travel at "lightspeed" for the medium through which they are travelling. Speed of light in a vacuum and all that.

Re: Limits.

So several downvoters appear to believe that < absolute zero is a perfectly reasonable concept ?

Science education is appalling !

Absolute zero IS one of the limits - certainly in this universe

Re: Limits.

I don't think you were downvoted because people believe that there can be temperatures below absolute zero, but because you were drawing a comparison with a value which BY DEFINITION can only be zero or positive, whereas the limit of lightspeed exists because of a practicality relating to mass. There is no upper limit on temperature, by the way, so the analogy with speed fails there; of course you cannot have a speed below zero.

Re: Limits.

> I'll cling on to hope, thanks.

Do not hope to do impossible things. Hope to do feasible things. Anything else is religion in a terribly bad way.

This is the Slow Zone. Better accept it.

Re: Limits.

I know it's by definition but it's amazing how many, otherwise intelligent well-educate people, think that it's just something that will be overcome as we learn more.

Incidently there may be a potentially max. temp. around 1E32K where physics breaks down so that all predictions fail.

Re: Limits.

I think you'll find the financial system is proof things existing below absolute zero.

Re: Limits.

http://en.wikipedia.org/wiki/Negative_temperature

Re: Limits.@Destroy All Monsters

"Do not hope to do impossible things. Hope to do feasible things"

Aim low to ensure disappointment, then?

In seventy years we went from the Wright flyer limping a few yards through the air, to reaching the Moon, but you're suggesting that in essence we know it all now, and should stop anything other than unambitious incremental improvement.

I hope my descendants have more to look forward to than a lighter, more easily emptied vacuum cleaner.

Re: Limits.

"http://en.wikipedia.org/wiki/Negative_temperature"

Now that you've found it try reading it and understanding what it actually means - here's a snipette :-

"by contrast a system with a truly negative temperature in absolute terms on the kelvin scale is hotter than any system with a positive temperature. If a negative-temperature system and a positive-temperature system come in contact, heat will flow from the negative- to the positive-temperature system."

Re: Limits.

Rubbish, Chemist! Your poopy-head facts are just a temporary hindrance to my sci-fi fueled optimism!

First the speed of light will be broken, and your "absolute" zero will be shown up as positively balmy - Einstein said everything was relative after all, and he had a fine moustache. Then we'll move on to sub-planck length transistors and proving both P and not-P simultaneously.

The human race is unstoppable! So stick that in your sciency-wiency-pipe, divide it by zero and smoke it.

Re: Limits.

And I quote : "(Hint : below absolute zero doesn't mean anything )".

@Chemist

Funny, I understood what that wiki article is saying, and, ironically, this is because of my training as a chemist.

I think maybe a better comparison would be to say the temperature of an object cannot fall below absolute zero by passing though zero, principally because Heisenberg's uncertainty principle prevents anything from ever being at absolute zero.

To get to a temperature below absolute zero, a system has to have an upper bounded temperature, i.e. be a properly closed system with a finite number of states, when energy is pumped into such a system at the maximum temperature which is an asymptote, an inversion occurs, and the temperature becomes the minimum temperature of teh system, which is the negative of the abosulte maximum. This doesn't apply to everyday classical objects, but only to specific things, such as the energy states in the atoms comprising a laser, and similar quantum objects.

The speed of light is a similar system, as an object approaces the speed of light, its mass approaches infinity. it is not possible to be at the speed of light, as the mass, and therefore energy would be infinite, but it may be possible to be beyond the speed of light, in which case the object in question would have to have negative mass/energy. In fact theoretical particles travelling at beyond the speed of light would have a lower limit for their speed of c and negative mass. We are essentially cut off from such theoretical particles, since they cannot slow down beyond the speed of light, and we cannot speed up past that point; the problem being the point in time at which the velocity is at c.

Re: Limits.

@Chemist. I find this interesting:

http://www.wired.co.uk/news/archive/2012-09/20/warp-drives

"The drive works by using a wave to compress the spacetime in front of the spaceship while expanding the spacetime behind it. The ship itself would float in a "bubble" of normal spacetime that would float along the wave of compressed spacetime, like the way a surfer rides a break. The ship, inside the warp bubble, would apppear to be going faster than the speed of light relative to objects outside the bubble."

Now I'm no mathematician or physicist, but this seems to broadly concur with the Adelaide prof mentioned here?

Re: Limits.

@Androgynous Cupboard

I do appreciate a well-reasoned argument. How about you provide one

Re: @Chemist

"but it may be possible to be beyond the speed of light, in which case the object in question would have to have negative mass/energy."

I point this out below somewhere although earlier in the day.

Re: Limits.

"The drive works by using a wave to compress the spacetime"

Sorry this has nothing to do with it. The so-called warp drive even if it eventually proves feasible allows a ship moving less than c to travel large distances quickly by altering spacetime using exotic matter and a great deal of energy.

Re: Limits.

The limit question in Special Relativity is intrinsically more nuanced and interesting. Einstein assumed continuous increase in acceleration. Quantum physics gives us discreet increases. The equations still work if V > c and you assume the i is an indicator of (for lack of a better term) a phase shift. Which is what these mathematicians explored.

Would I ever want to be the test monkey in an experimental device based on these assumptions? Hell no! But it can be fun to talk about, even though Al's musings based on practicality are probably spot on.

Re: @Destroy All Monsters - "humans limited forever"

"If true, what's the point in carrying on? We might just as well use genetic engineering to cut our fertility down to a level that allows the human species to gracefully fade away, if we accept that there is no use for our intelligence."

I think he probably meant faster than light travel was a no-go, not that there's no use for intelligence. There's more to life than clinging to some green-skinned space babe fantasy, mate. What that might be I don't know, but ...

Re: Limits.

@Tom7 that could also be the ideal argument for entropy :)

Re: Limits.

"This is the Slow Zone. Better accept it."

My mind bobbles :-)

Re: Limits.@Destroy All Monsters

When you put it like this, it saddens me greatly that this boom time of innovation came to an end nearly 40 Years ago now. Weren't we not meant to be colonizing Mars and live in floating houses (i.e. The Jetsons). And what about our flying Cars? If the Internet is the best thing to come out of our Epoch. Then may we be forgiven.

Re: Limits.

Actually, shadows do travel at the speed of light.

Re: @Chemist

What ?

maybe you're a chemist (?), but you ain't no physicist !!

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Re: @Chemist

Well I am really a chemist (retired) but I've spent a lot of my time writing scientific software, protein modelling and utilising quantum mechanics. All these things have required rather a good knowledge of physics..

Your evidence ?? and indeed provenance as you only joined today so we've not had the benefit of your wisdom before.

Re: @Chemist

I'm happy to believe you have a fine understanding of both physics and chemistry. Almost certainly better than mine. I've felt no need to down-vote you.

However when you make assertions along the lines of "science education is rubbish" you are kind of required to get your facts right thereafter.

You used as an example the fact that absolute zero is an absolute, and lower temperatures "have no meaning". I provided you with evidence that it does. Your response was to critcise me and assume I hadn't understood what I read. As it happens I believe I had understood it, and it told me your prior assertion was incorrect - negative temperatues do have meaning, albeit that meaning is rather esoteric by "normal" standards and is certainly not what the layman might consider "obvious".

High horses require high standards of their riders...

Not a boffin, just cold.

Re: @Chemist

I was actually replying to a comment by outinoregan who suggested that I didn't without giving any evidence.

As for the negative temperature as you say that's rather esoteric and not directly related to my point. I apologise if I assumed that you had no understanding of the area but on these forums many people know enough to search/quote from the web but have no real knowledge of the subject.

My comment about "science education being rubbish" was due to several comments recently in the media where several pronouncements were made along the lines of "of course everything is possible" when clearly the history of the world, let alone science shows that there are almost certainly limits in certain directions.

Re: @Chemist

Fair enough.

I confess I too despair of the standard of some reporting of science, and even more of what seems like a general malaise towards the subject as a whole. Although to be honest probability and risk are possibly an even bigger issue (from a maths graduate who does the lottery now and again - so who am I to talk!)

I don't know a great about the subject to be honest, but I do know what absolute zero is (cold :-)

I hope somebody works out how to go faster than light, preferably without requiring more energy than exists in the universe, but I don't expect to see it for anything larger than a electron in what remains of my lifetime, if even that.

As for everything being possible, well, we only have theories to support our scientific view of the world. Theories are far easier to prove wrong than correct. Point here is that some of the key theories we're talking about are proving incredibly robust. A certain amount of cynicism is always warranted, in both directions.

But as you say - there are limits - and we should always aim to make decisions based upon the best available evidence, not superstition, hope (see above) or too much star trek.

Re: Limits. @ relpy

I dont think that falls into the 'laymans' language...

i,e, what is the closest 'black body' in the solar system???

:) hint, it is something that reflects NO light.. all the planets do.. :)

Re: Limits.

"That's where photons come in, you can't speed them up or slow then down. They always travel at 'lightspeed'."

While it's true that photons travel at light speed. It is not true that they only travel at "c." Light is slowed down all the time. For example, refraction is the slowing of photons. Scientists have also devised all sorts of neat ways of slowing down photons to a walking speed.

Re: Limits.

Einstein never said nothing can move faster than light. Teslar specifically stated that neutrons seem to exhibit faster then the speed of light speeds at high energy levels, nothing in e=mc2 prevents it from doing so. So please let's stick to the mathematical and physical facts, not assumptions that fit our current theories. "The scientists of today think deeply instead of clearly. One must be sane to think clearly, but one can think deeply and be quite insane." N. Teslar. Rember the sound barrier? Scientists actually argued it wasn't possible to break that barrier, light speed is no in the same league, but you can see how delusional mainstream science can be. "The scientists who appeared to have found in September that certain subatomic particles can travel faster than light have ruled out one potential source of error in their measurements after completing a second, fine-tuned version of their experiment.

Their results, posted on the ArXiv preprint server on Friday morning and submitted for peer review in the Journal of High Energy Physics, confirmed earlier measurements that neutrinos, sent through the ground from Cern near Geneva to the Gran Sasso lab in Italy 450 miles (720km) away seemed to travel faster than light."

Re: @Chemist

I stopped reading when I saw the word 'asymptote' because it triggered a bad flashback. I'm feeling better now, thanks.

The speed of light is most obviously the ratio of time quantum to space quantum. Time and space are being created continuously (oops, I mean one quantum after the other, and quickly). With that in mind, you the readership might want to reconsider what is meant by 'at rest' and 'energy'.

Re: Limits.

Two different things: Absolute zero is not a thing, it is a lack of a thing, in this case, energy (the same goes for darkness.) FTL is something that would require more energy; infinite maybe, but it is derived from something, not nothing.

Re: Limits. @ relpy

Reflects *NO* Light.

Wouldn't want to be too hard on that.

find the right requency and I think it might.

Big and shiny not withstanding.

(icon because that's what it is)

(and okay, it reflects no light I grant you, to any measurable value of none).

Re: Limits.

Why is it that everyone conveniently forgets about things like time dilation and length contraction when they start speaking about speed limits? Is it that difficult to remember that as you go faster the distance traveled is shorter and the time it takes becomes longer? I know, it's a pisser, the faster you go the slower it seems and there's nothing to stop you from breaking the speed of light other than the fact that you couldn't tell because the only way to measure the speed is with something in an external reference frame and the signals travel at, wait for it, the speed of light.

Re: @Destroy All Monsters - "humans limited forever"

Even with relativity intact, you can get anywhere you like as fast as you want, (well, not counting pesky problems like getting bombarded with highly energetic particles caused by their relative blue-shift and the like). You just can't come back without massive time dilation. (See for example http://en.wikipedia.org/wiki/Twin_Paradox).

So, kindof hard to run a Galactic empire, but, hey maybe that's for the best.

Re: Limits.

The faster you go, the slower it seems, to AN EXTERNAL OBSERVER, to you, you just go faster. Yes, and things get thinner relative to you, and external time speeds up, and in the other reference frame, you get heavier . And visible light turns to X-rays, I like how people forget that. Absent some serious field tech, the main problem is the stuff you are flying through, oh and going home, you don't get to do that.

Re: @Destroy All Monsters - "humans limited forever"

"you can get anywhere you like as fast as you want"

Assuming you have a means of generating the vast amount of energy required. - otherwise I agree

Re: Limits.

You forgot. While you keep going "faster", the universe continues to speed up too! Thus, you get to your destination not quicker, but slower.

For example, moving to Planet Zog 2 light years away, you speed up at 2x the speed of light, expecting to get there in 1 year. Nope, you experience 1 year (you actually did go faster) but when you get there, you missed the welcome party, it was 1 year ago, because 2 years still passed on Zog. :P

Re: Limits.

Light is not slowed down. You either make it take a less direct route (gravity etc) or destroy it (absorption?) and re emit it. It's the time between being absorbed and re-emitted by electrons (IIRC) that takes the time, not the travel of the light wave.

Gravity does actually slow light down. But that's probably not a correct description. Gravity slows the universe down, so from our reference frame, I guess it's the same. :P

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