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← Time travel: light speed results cast fresh doubts

Time travel: light speed results cast fresh doubts - Comments

Anonymous's Avatar Comment 1 by Anonymous

Comment Removed by Moderator

Tue, 26 Jul 2011 11:30:33 UTC | #854199

keyfeatures's Avatar Comment 2 by keyfeatures

I've been wondering if photons are potential time travellers. This puts that theory to bed but throws the focus on other questions. Was the limit of c set by the way universal space-time came into existence (i.e. did the initial wave / fluctation set this limit?), or is it an automatic limit that the universe had to abide by and could not 'create' beyond?

Tue, 26 Jul 2011 11:33:20 UTC | #854201

anonymous.shyster's Avatar Comment 3 by anonymous.shyster

Anonymous...he always gets in first, but his posts are always removed.
Poor sod.

Tue, 26 Jul 2011 12:16:38 UTC | #854213

JumpinJackFlash's Avatar Comment 4 by JumpinJackFlash

That was actually my comment. It was a joke advertisement for a DeLorean for sale, owing to the redundancy of time travel if this story is accurate, but it seems to have been misinterpreted as an actual advert. I am not Anonymous. At least not here.

Tue, 26 Jul 2011 12:23:14 UTC | #854216

mmurray's Avatar Comment 5 by mmurray

Comment 4 by JumpinJackFlash :

That was actually my comment. It was a joke advertisement for a DeLorean for sale, owing to the redundancy of time travel if this story is accurate, but it seems to have been misinterpreted as an actual advert. I am not Anonymous. At least not here.

It was funny but you're right it must have been confused for spam.

There is no anonymous. When posts are deleted they seemed to be assigned to anonymous.

Michael

Tue, 26 Jul 2011 12:27:40 UTC | #854217

JumpinJackFlash's Avatar Comment 6 by JumpinJackFlash

No worries! I am not Legion, I do forgive and I do forget so no harm done.

Tue, 26 Jul 2011 12:28:38 UTC | #854218

aquilacane's Avatar Comment 7 by aquilacane

LOL, time travel. What imaginations. Next they'll say there is a sky daddy who created everything.

Time travel by other means, however, is not entirely ruled out.

It should be. Waste of energy... as there is no actual time to waste.

Tue, 26 Jul 2011 13:04:26 UTC | #854226

chulinn's Avatar Comment 8 by chulinn

This time travel is a very tricky thing. In school I learned that the faster a body moves, the slower time passes. You might remember the twins, one staying on earth, the other one travelling through space at a very high speed. Once the travelling twin returns he looks younger than the other who remained on earth.

So if you imaginge higher and higher speeds, time passes more and more slowly. With photons travelling at the speed of light, time does not pass et all! So I believe photons cannot travel in time either way. Which means, if a photon is at location X (say earth) at time t0, it will arrive at location Y (say the moon) also at time t0! No time at all has passed for the photon. But what if at location Y there is a mirror, and the photon travels back to location X? It must arrive on earth again at t0, i.e. instantaneously. Quite some paradoxon. I am puzzled.

Tue, 26 Jul 2011 13:10:11 UTC | #854228

jac12358's Avatar Comment 9 by jac12358

Fascinating. See how science is done? It is sobering to see how actual results could disappoint hopeful theories. I suppose this is made easier because there is no huge industry or political or religious movement with interests tied to superluminal speeds, and so it is only the poor scientists themselves whose dreams of building time machines are thwarted.

I like where it says "an event's effect cannot precede its cause" because I am pretty tangled up with causality in my debates on free will (yes, pun intended). The way I see it, neither light nor any other form of electromagnetic energy - say, a pulse along a neuron - can precede that which caused it. The trick is, in free will, one might say the firing neuron has not preceded anything, but rather "willfully acted" with complete disregard for causal precedents. And that is what I find unconvincing. I wish this area of study were easier or more often performed.

Tue, 26 Jul 2011 13:15:53 UTC | #854230

keyfeatures's Avatar Comment 10 by keyfeatures

Of course we are all travelling through time and new time is created all the time. It would be a lot harder not to.

After all, the size of the universe represents the time (this cycle of) the universe has existed. We couldn't travel into future time because it hasn't been created yet.

Same goes for photons I guess.

Tue, 26 Jul 2011 13:18:25 UTC | #854232

thebaldgit's Avatar Comment 11 by thebaldgit

I would doubt that this would stop any proposed form of time travel as it has been thought for quite a while that time travel would only be viable not by travelling faster than light speed but the bending of spacetime with such things as wormholes.

Tue, 26 Jul 2011 13:24:17 UTC | #854233

keyfeatures's Avatar Comment 12 by keyfeatures

comment 11 by thebaldgit

But there must be a good reason why spacetime itself can't travel down a wormhole. Humans are spacetime.

Tue, 26 Jul 2011 13:47:33 UTC | #854242

Daniel Williams's Avatar Comment 13 by Daniel Williams

Hmmmm…. it’s a shame that time travel might not be possible. Being able to travel back in time could solve all our travel problems.

Correct me if I’m wrong here but:

If we were able to travel back in time we wouldn’t have to travel the massive distances to other star systems. With an ever contracting universe if we were able to travel far back enough eventually where ever we would ever want to go would only be centimeters away. All we would then have to do is travel the relatively short distance and wait. Possibly in a long term hibernating state. And wake up at the appropriate time.

Tue, 26 Jul 2011 14:39:30 UTC | #854258

SomersetJohn's Avatar Comment 14 by SomersetJohn

Comment 8 by chulinn :

Which means, if a photon is at location X (say earth) at time t0, it will arrive at location Y (say the moon) also at time t0! No time at all has passed for the photon. But what if at location Y there is a mirror, and the photon travels back to location X? It must arrive on earth again at t0, i.e. instantaneously. Quite some paradoxon. I am puzzled.

I would guess that travel through the atmosphere (slower than vaccuum speed), space (not a true vaccuum), the mirror, (twice, once in once out assuming it's a silvered glass mirror rather than a polished metal mirror), would eliminate the paradox.

Tue, 26 Jul 2011 14:40:27 UTC | #854260

Daniel Williams's Avatar Comment 15 by Daniel Williams

sorry double post

Tue, 26 Jul 2011 14:44:30 UTC | #854263

kantastisk's Avatar Comment 16 by kantastisk

...moving information around at faster-than-light speeds is impossible.

I'm no physicist but doesn't the very name of Quantum Theory go against this? I thought it well established that many events in nature are instantaneous and therefore necessarily faster than the speed of light. What about Quantum entanglement?

http://en.m.wikipedia.org/wiki/Quantum_entanglement

Tue, 26 Jul 2011 15:03:38 UTC | #854271

Daniel Williams's Avatar Comment 17 by Daniel Williams

Or does this only relate to forward travel??

Tue, 26 Jul 2011 15:21:20 UTC | #854276

KenChimp's Avatar Comment 18 by KenChimp

Comment 16 by kantastisk :

...moving information around at faster-than-light speeds is impossible.

I'm no physicist but doesn't the very name of Quantum Theory go against this? I thought it well established that many events in nature are instantaneous and therefore necessarily faster than the speed of light. What about Quantum entanglement?

http://en.m.wikipedia.org/wiki/Quantum_entanglement

Quantum entanglement is an interesting phenomenon, but isn't a loophole for faster than light propagation of information, and by the exact same reasoning that invalidates the deBroglie-Bohm theorem of non-local "hidden" deterministic variables. Both violate Einstein's Theory of Special Relativity.

Tue, 26 Jul 2011 16:08:00 UTC | #854292

B33b13br0x's Avatar Comment 19 by B33b13br0x

I have a time machine at home that travels at 1x normal speed into the future.

It's basically a cardboard box with "Time Machine" painted on it.

Tue, 26 Jul 2011 16:42:09 UTC | #854312

Dhamma's Avatar Comment 20 by Dhamma

I've been told I run faster than the speed of light. Well, I can't really remember that, but I've felt younger ever since.

Tue, 26 Jul 2011 17:24:42 UTC | #854336

BloodywombatTSI's Avatar Comment 21 by BloodywombatTSI

So, I'm a little confused. Does this mean that time does not slow down at faster velocities? Does this invalidate the results of past experiments with atomic clocks, and the fact that GPS technology is based on the very notion of time dilation at higher velocities? Or is this different? Because that is time travel is it not?

Obviously, time travel by other means was not ruled out, I assume they mean something like, by orbiting a strong gravitational force such as a black hole or something, but I'm wondering specifically about time travel related to high velocity.

Tue, 26 Jul 2011 18:19:30 UTC | #854360

prettygoodformonkeys's Avatar Comment 22 by prettygoodformonkeys

I, too, have a time travel machine. It's called 'me', and it travels at exactly a 1:1 ratio with local spacetime.

Tue, 26 Jul 2011 18:21:34 UTC | #854361

-TheCodeCrack-'s Avatar Comment 23 by -TheCodeCrack-

God can do anything, including time-travel (he is all powerful). Strange though that he never goes back in time and fixes his mistakes?

The answer? He works in mysterious ways....

Problem solved.

Tue, 26 Jul 2011 18:33:06 UTC | #854366

B33b13br0x's Avatar Comment 24 by B33b13br0x

@21 no it means that while you may be able to make a photon travel faster through a given medium than it normally would, the speed of light in a vacuum (~3.0*10 ^ 8 m/s) is the hard cap on how fast a photon may travel.

Time dilation at high speeds or under high gravity is still something that happens.

The time travel they're referring would be an effect of faster-than-light travel which would allow a particle traveling faster than ~3.0*10 ^ 8 m/s to arrive at its destination prior to leaving its source.

As the old joke goes, the day before tachyons [that is a particle that travels faster than light] are discovered, there will be a message from the discoverers in the newspapers that reads"tachyons have been discovered tomorrow"

Tue, 26 Jul 2011 20:31:04 UTC | #854404

BloodywombatTSI's Avatar Comment 25 by BloodywombatTSI

So you're saying that it means that they confirmed backward time travel is impossible (which was the prevailing theory as I understand it), at least by means of faster than light travel, correct? Also, thank you for answering my question.

Tue, 26 Jul 2011 20:45:03 UTC | #854408

asyouwere's Avatar Comment 26 by asyouwere

I'm just guessing, but wouldn't a ship of some sort, tricked out with a Higgs Field neutralizing generator, be able to slip along at faster-than-photon velocity? Would we then have to come up with new maths to calculate (or define) velocity?

Tue, 26 Jul 2011 21:48:07 UTC | #854427

Alex, adv. diab.'s Avatar Comment 27 by Alex, adv. diab.

Hello everyone,

BloodywombatTSI, another solid state physics experiment way oversold using a catchy headline. That being said, of course they can't disprove anything, that's not how science works. They have merely put an upper limit on ye thyme-trevelynge phowton, within their experimental accuracy.

kantastisk,

In the quantum version of special relativity, all kinds of strange faster than light things happen at the level of quantum fluctuations, but, o wonder, as soon as one starts looking at physical observables, these apparent superluminal effects all cancel. That's a nice, but not all that surprising theory result. Now, if you go to the quantum version of general relativity... you get a nobel price.

Daniel Williams,

sounds reasonable... if you like it hot :)

chulinn,

That's a nice thought experiment, if only to illustrate the breakdown of some of the visualizations we make for ourselves. Yes, the photon goes back to the same place, and the proper time of the photon is still the same as before, namely 0. This may sound strange, but it is actually not in contradiction with anything. No causality of any kind is violated. It is just very odd to imagine being a massless particle in a relativistic universe ;)

Tue, 26 Jul 2011 22:32:31 UTC | #854442

kantastisk's Avatar Comment 28 by kantastisk

Comment 18 by KenChimp :

Quantum entanglement is an interesting phenomenon, but isn't a loophole for faster than light propagation of information, and by the exact same reasoning that invalidates the deBroglie-Bohm theorem of non-local "hidden" deterministic variables. Both violate Einstein's Theory of Special Relativity.

This is way out of my league... I just don't understand why quantum entanglement couldn't be seen as instantaneous propagation of information.

Tue, 26 Jul 2011 23:17:57 UTC | #854462

BloodywombatTSI's Avatar Comment 29 by BloodywombatTSI

Comment 27 by Alex, adv. diab. :

Hello everyone,

BloodywombatTSI, another solid state physics experiment way oversold using a catchy headline. That being said, of course they can't disprove anything, that's not how science works. They have merely put an upper limit on ye thyme-trevelynge phowton, within their experimental accuracy.

Just to clarify, I did not use the word "disprove", I used the word "confirm", which is different according to the dictionary definition of the word I'm familiar with, at least the one I intended. I just looked it up to make sure. I chose carefully my word usage for that very reason. Here is the link to my source below:

http://www.merriam-webster.com/dictionary/confirm

I just meant that the theory that backward time travel is impossible, which as I said, was the prevailing theory as I understand it, was strengthened or made more valid with the experimental data mentioned in the article. I purposely avoided the word "prove" or "disprove" as I realize that word is a slippery slope in science, so I decided to use a word I believe I've heard scientists use in this regard. Thank you for responding further to my question though.

Tue, 26 Jul 2011 23:29:24 UTC | #854466

Zeuglodon's Avatar Comment 30 by Zeuglodon

It just occurred to me that you could use near-lightspeed travel, in theory, to investigate evolution. One of the problems of evolution is that much of it is so slow to observe directly, at least when considering animals or plants that live longer than humans.

You could, hypothetically, build a really fast spaceship, speed off into the future by travelling so that (say) five centuries or six pass by in a matter of seconds, come back and see how, for example, a population of horses has evolved in the meantime.

First, you take a sample of genetic code from a representative sample of the horses, and make a note of it before you go into the ship. You leave instructions to keep the horses breeding and alive for the future.

Then, you speed off for however long you want, come back, find the population again, and then take a second genetic sample and compare the two. You could also note their body shapes and sizes, or other phenotypic characteristics, and compare that with historical records made by Earth-based scientific collaborators.

Of course, the whole thing supposes nothing goes wrong in the meantime, like a catastrophe or a war or neglect by the land-bound scientists, but it was such a nice thought experiment.

P.S. I'm new to the site; is there a welcome page where new users introduce themselves?

Tue, 26 Jul 2011 23:44:10 UTC | #854468