Speed of light

Evil Phil

I've heard that the speed of light has been broken, at CERN or somewhere. Any thruth in this? Does anybody have a link?

][cEMAN**

Not unless they've done it in the last few weeks because we've discussed this before.

I tried to argue that somewhere they had in a lab acually experienced quarks instantly jumping back through time, but I had no evidence and as such was shot down rideculed.....my wife left me - my kids had no respect for their father...and worst of all...I lost my monthly subscription to Playhouse. Life's a byitch man ;p

bonkey

I'm not sure if its what Evil Phil is referring to, but there were some experiments recently which showed that under certain conditions, it appeared that light travelled through a certain medium af FTL velocities.

What in fact happened was explanable through the difference in the terminology. Individual photons were never travelling at FTL speeds, but for some bizarre reason, the wave propagation could do some magic.

I recall Slashdot talking about this some time ago, and there being much heated discussion about it.

Interestingly, the same technique has allowed light to be slowed to a crawl - effectively stopped. Again, the individual photons are not stopped, but the wave propagation is messed with, so in effect you get a standing wave of light, but with the individual photons within it still travelling at light speed.

I'll see if I can find you some info.

Iceman - sorry about your Playhouse subscription But I still think you were wrong (or dreaming of Miss August).

jc

Evil Phil

No I was talking about quarks jumping back in time. I've heard a few people talking about it and it sounded kind of improbable, but I wasn't sure.

bonkey

Oh - okay.

The problem I have with this is that even if it is possible for a particle to travel FTL, it should not jump back in time (according to our current models at any rate), but rather it should travel through time backwards. This is the biggest problem I have with all of the discussions on this so far.

There are a number of issues with "travelling through time" in this way, even if it is theoretically possible.

Consider a video of a dot moving across an oscilliscope, where the edges of the display have been blanked out. You have no way of knowing whether the video is playing in forward of reverse. In fact, the only way of determining this would be to remove the blanking at the edges of the display and to look for teh telltale signs of a line starting and ending (the luminosity will be different, allowing you to determine each end).

For a quark travelling "back through time", the same would apply. The only method we would have of determining that it is moving back through time would be to observe it reacting with something. However, seeing as we observe time in one direction, we would see the reaction, and then see the quark speeding away from it.

Perhaps this is what happened. Perhaps an experiment was performed where a quark was shown in the results which should not have been there, and it has been postulated that it was travelling FTL and therefore back through time.

At the end of the day, it should be impossible to *deliberately* test this stuff in a lab. How can we accelerate a quark to FTL velocities? (How can a quark, which has mass, travel at FTL velocities, for that matter). Imagine that we could accelerate it for a second. How can we test this theory?

From what I can see, we could only test this by observing the quark react with something, and *then* get fired from our "quark gun". If this was the case, dont you think it would be far more highly publicised? I mean, quantum tunelling was covered by pretty much every major scientific magazine as soon as it was postulated (based on observation) complete with possible explanations of what was happening. I would imagine that FTL and "time-travelling" quarks would get similar coverage....

Having done some quick goole searches, I've found a few references. All of them (so far) are pointing towards what I was saying - that it appears that FTL is happening, but not with what is known as the "wave-front" which (at the end of the day) is what relativity puts the restriction on. So far, I haevnt found anything really readable.

Oh - for reference, they are all discussing photonic FTL, as opposed to quark-based. To me, this makes far more sense, as photons do not have mass, where quarks do.

jc

BoneCollector

Just an observation open to debate of course!?

If FTL was possible and we where to travel from one galaxy to the other FTL and you reach your destination. Assuming that FTL would send you traveling backward through time, then from the observers point of view, would you not instantly arrave at your destination?

WhiteWashMan

Originally posted by BoneCollector
Just an observation open to debate of course!?

If FTL was possible and we where to travel from one galaxy to the other FTL and you reach your destination. Assuming that FTL would send you traveling backward through time, then from the observers point of view, would you not instantly arrave at your destination?

no.
anyway, how would you know? theyre in another galaxy

phoenix2181

yea but Everytime i'm on the m50 driving home & I hit 88mph in the Delorean, I travel thru time were there are no signposts (check the dundrum end) & people don't know what lanes they should be in......come to think about it that still happens today.......oh the horror...the horror

BoneCollector

Oh Gawd!
I ask a speculative question and all i get are irrelaventcies
OK! then the Moon or the nearest star!? which ever suits your taste to make it easier. :rolleyes:

Raskolnikov

Ok i am a little confused here, has it actually been proven that you in fact pass the speed of light or is it something that is theoretically true.

Lennoxschips

The current theoretical methods for going faster than light involve taking shortcuts (including the now famous "Warp Theory").

As we all know if Mr. A travels at 50mph, and Mr. B travels at 50mph, but Mr. B takes a shortcut, it doesn't mean that Mr. B is faster, he just got there in a shorter amount of time. Which is handy if you want to go somewhere far away. But scientists will of course go public and call these shortcut methods "faster than light" as this increases their chances of getting a nice research grant.

phoenix2181

yea but thats the folding of space, which would take hugh amounts of energy to attempt you would need something as powerfull as a black hole to harness, surpassing the speed of light would be easier then that maybe using antimatter, but at the moment we have only made just a few molacules no were near the amount needed (see cern feb 2000)

Lennoxschips

I diddnae say it had been done!

bonkey

Originally posted by BoneCollector
If FTL was possible and we where to travel from one galaxy to the other FTL and you reach your destination. Assuming that FTL would send you traveling backward through time, then from the observers point of view, would you not instantly arrave at your destination?

Sort of....

Were the supposition true that FTL == timetravel, then we must think about how it appears. What the theory actually speculates is that someone travelling FTL from A to B will appear (to an outside observer) to be travelling from B to A at a STL (slower than light) speed. In otherwards, to the traveller, they know that they are travelling at (c + X) from A to B, but to the outisde observer, they appear to be travelling at (c - X) from B to A. Goddit?

OK...

So, yes, they would apparently "instantly appear" at their destination, BUT would then immediately speed away from it (their *approach* at FTL velocities, being viewed "in reverse"). Now, they would only appear from nowhere if they dropped to STL velocities. Otherwise, you would have seen them passing by, and they wouldnt appear. In order for them to appear, they have to have gone from FTL (so their approach is in the observer's future) to STL (so that their "stay" is also in the future). In this case, they appear, and then appear to split giving you the approach in reverse, and the stay (in normal time).


If you consider time as a line, then you can view "normal" travel as going from left to right. FTL is then going from right to left.

A particle which always travels STL will always travel from left to right. A particle which always travels at FTL will always travel right to left. A particle which oscillates between STL and FTL will alternate between moving left and right. At no time, can a particle "jump" its position on the line.

So, if you're still with this, then consider what the "quark jumping through time" is doing. Sure, you can see a quark "appear" out of nowhere, as it transitions from FTL to STL. However, for this to happen, you would actually see a quark appear out of nowhere, and immediately split into two quarks, each travelling in opposite directions.

Yes, it sounds odd, but this is what the theory implies. Thus, I find it difficult to understand how someone can see a particle "jump" in time. It doesnt fit with our model of how things work.

jc

bonkey

Originally posted by phoenix2181
yea but thats the folding of space, which would take hugh amounts of energy to attempt you would need something as powerfull as a black hole to harness, surpassing the speed of light would be easier then that maybe using antimatter, but at the moment we have only made just a few molacules no were near the amount needed (see cern feb 2000)

Phoenix...

if our current models are in any way correct, you *cannot* accelerate mass past the speed of light. FTL *may* occur at a quantum level, but even then there is sketchy evidence at best.

Therefore your supposition that this apparent impossibility would be somehow easier than other approaches is a bit odd.

Also, I thought that it was antimatter particles, not molecules

jc

phoenix2181

correct me if I'm wrong but haven't they recently able to slow down the speed of light to about 40mph, so in theory I could get into my car and travel at 50mph and so I would be traveling faster then the speed of light. I'm not a scientist so I don't know how they did it (I would be a rich man if I knew), but as we all know that the laws of physics are always being bent or amended with new theories and technology.

bonkey

Originally posted by phoenix2181
correct me if I'm wrong but haven't they recently able to slow down the speed of light to about 40mph, so in theory I could get into my car and travel at 50mph and so I would be traveling faster then the speed of light.

Not quite.

As I mentioned at the top, this was an experiment where the wave propagation could be accelerated or slowed, but that the individual photons themselves never changed velocity.

The "speed of light" is an inaccurate term anyway. When we talk of c being the absolute velocity, we refer to the speed of an individual photon, or (if you prefer) the propagation of light in a vacuum. This value does not change, not matter what you do.

Take a simple analogy. Lets say (for arguments sake) that the Lockheed SR71 Blackbird is the fastest airplane ever manufactured. I can run faster than an SR71 when it is taxi-ing at 1mph. Does this mean that I can travel faster than the fastest plane? Not really, unless youre a bigger pedant than me

jc

phoenix2181

but at that moment/second in time you are faster then the blackbird travelling a 1mph if your running;)

Raskolnikov

This is a little off-topic but i was wondering if you passed sound through an extremely dense medium could you get it to exceed the speed of light since the denser the medium sound it passed through the greater it's speed is.

I don't suppose anyone knows if there is an equation that relates the speed of sound in a a dense medium?

nesf

Ahm, from a practical aspect no. The average speed of sound in copper/brass or iron is in the 10^3 region (m/s), this is still far slower than the speed of light.

Plus the speed of sound isn't so much related to density as it is to sheer and bulk modulei. (can't remember which, even tho i'm doing an open project on it! :rolleyes: )

Raskolnikov

I'm thinking something like an ultradense medium like a black hole.

bonkey

An ultradense medium like a black hole would be pretty useless for this purpose.

Ignore the practicalities of actually using one, there's a larger probem.

A black hole is believed to consist of an ultra-dense point, which exerts an attractive force sufficient to trap light out to a certain distance. This distance gives rise to the even horizon.

Thus, in all cases, the ultra-dense part of a black hole is infintessimal. If you use traditional or quantuum theories, you typically get a one-dimensional point, whereas under string theory you typically have something at about planck length in size.

Regardless, in all models, the black hole is too "short" to propagate a sound wave.

So, even were it possible to control a black hole, and somehow manage to fire a soundwave at it, the actual ultra-dense part of the black hole is too small to actually be able to carry the wave, and thus the problem could never arise

So - no - sound in a black hole could not travel faster than light!

jc

Raskolnikov

Aw crap my future dreams of opening up a black hole somewhere and firing sound waves through it are foiled, maybe i'll just stick with my original idea of placing a giant laser on the Moon and use it to hold the world to ransom for a sum of 1 million Dollars, Bwahahahahaha!