Re: The speed of light : Sat Nov 19, 2011 12:40 am  

Stand-Offish wrote:

A better understanding of the Universe and what makes things tick.

It's usually clocks , sometimes bombs , with clocks on them

Re: The speed of light : Sat Nov 19, 2011 12:49 am  

Cronus wrote:

As far as I know, they scrutinised the experiment repeatedly in minute, intimate detail for a helluva long time, before publishing the results (together with reams of data) with an open request for the global scientific community to disprove them. So far, no-one has.

They aren't declaring "look everyone, we've achieved faster than light speeds", they're saying, "erm, our results are suggesting the theoretically impossible has taken place and we can't see how or why, and we're struggling to disprove it, can anyone help?"

As for the quote, I remember writing on the door of my university loo: "Vodka corrupts; Absolut Vodka corrupts absolutely".

Yes I know they checked their results. I have watched the documentaries on this. Which doesn't discount making a continual mistake.
And yes they are saying we have achieved faster than light speeds.
Or perhaps they are saying ' we are achieving faster than light speeds ... unless someone knows different'.
In which case, they are not that confident are they?

My understanding is that over vast distances of space, measurements would suggest they are wrong. Since light from stellar cataclysms has reached Earth before the associated neutrinos.

Mind you, their findings are supported by some work that happened in the USA some years ago.

Re: The speed of light : Sat Nov 19, 2011 12:49 pm  

Scooter Nik wrote:

I know there's a flaw in this but I'm REALLY struggling with it.

Maybe the rest of this bottle of wine will help. Best I can do is that as you're both fair minded gentlemen, ten seconds will pass equally on both ships, so both fire at exactly the same time (relative to each ship), and as both are doing the same speed, and have accelerated at the same rate, then to an external observer, both ships would fire and explode at exactly the same time, as both on-ship times will be identical to the external observer?

The flaw is that FTL travel violates causality. A specific cause under specific conditions ought to have a specific effect. Not only that, but the cause has to come before the effect. Science and repeatability are entirely based on causality, and since special relativity does such strange things to time everyday concepts like "before" and "after" don't really make sense any more. But a cause still has to come before an effect, and an effect still has to come after a cause.

Say it's midnight,and I'm flashing a torch sending signals to my secret Mars base. My guys up there will get my message in about ten minutes or so. If I wanted to send an object at the same time, and it went just slower than the speed of light, that might get to Mars about fifteen minutes from now.

Dally's on his spaceship, and he's flying by when I send the object to Mars. He's going at sublight speed but damn quick. He watches the object all the way. From his frame of reference it takes maybe twelve minutes. From mine, and the guy on Mars, it takes fifteen. But to Dally, his frame of reference doesn't matter with respect to the light. It sets off at midnight and it gets there at 00:10. It says that on my watch, it says it on Dally's and it says it on the cooker in the Mars Base Alpha kitchenette.

Now say that somebody's left the gas on in that kitchenette. It blows up at 00:05. It's that time on Mars, and it's that time here. For Dally, what time his watch says when this happens depends entirely on how fast he's travelling and in what direction. It's possible that for him the explosion and me sending the object happen at the same time, even though they happened five minutes apart. It's possible that the explosion happens before I send the object, even though from the perspective of me and Mars it happens five minutes after.

Just like I had an instantaneous gun, say we have instantaneous communications for our faster than light super advanced spaceships. Mars sends a message to Dally. Dally sends a message to me. I send a package to Mars. Mars Base Alpha has blown up by the time any of this happens. Paradox. I think.

Re: The speed of light : Sat Nov 19, 2011 9:10 pm  

I understand all that, I think the flaw in the original post was that the weapon was instantaneous, hence violating the speed of light limit and so making either the original statement invalid. Either C is a constant and measurable maximum speed, or it's not. The battle scenario assumes that >C speed is possible, and so surely the relatavistic speeds are irrelevant to what is happening outside the ships.

If the ships are travelling faster than light, then each ship won't see that the other has fired, as the light from the weapon will be left behind by FTL travel, and so the idea falls to bits.

I've just remembered I read a novel that dealt with the impossibilities of space warfare fairly recently, damned if i can remember what it was though, but the bottom like was that the only way to hit a ship travelling at speeds close to those of light was to blanket every inch of space that the opposing ship could turn into, an impossible condition as the ship that was firing would actually have no idea where the other ship was, as it could have turned or slowed and accelerated any number of times before they were even 'seen'. I do love 'hard SF' even though it makes my brain bleed.

Re: The speed of light : Sun Nov 20, 2011 3:33 pm  

I understand all that, I think the flaw in the original post was that the weapon was instantaneous, hence violating the speed of light limit and so making either the original statement invalid. Either C is a constant and measurable maximum speed, or it's not. The battle scenario assumes that >C speed is possible, and so surely the relatavistic speeds are irrelevant to what is happening outside the ships.

But isn't it that that's in doubt here? If greater than c is possible then upper limits on speed, at least according to current understanding, become irrelevant, and would tend towards instantaneous at the kind of distances me or Dally can keep a steady aim at.

I'm sure there's some notion of instantaneous over great distances in quantum theory too. But I don't get any of that. At all.

I've just remembered I read a novel that dealt with the impossibilities of space warfare fairly recently, damned if i can remember what it was though, but the bottom like was that the only way to hit a ship travelling at speeds close to those of light was to blanket every inch of space that the opposing ship could turn into, an impossible condition as the ship that was firing would actually have no idea where the other ship was, as it could have turned or slowed and accelerated any number of times before they were even 'seen'. I do love 'hard SF' even though it makes my brain bleed.

The Forever War? Ages since I've read it so not sure myself, but wars across interstellar distances and time dilation are the main plot elements. Excellent book, with sequels that aren't sequels which I haven't read yet.

Re: The speed of light : Mon Nov 21, 2011 1:47 am  

Cronus wrote:

As far as I know, they scrutinised the experiment repeatedly in minute, intimate detail for a helluva long time, before publishing the results (together with reams of data) with an open request for the global scientific community to disprove them. So far, no-one has.

Not really. To "disprove them" suggests you accept they appear to have "proved" something. Not even they suggest that. Basically they have put their findings out for peer review, and for other scientists to have a go and test them.

And there has been something of an avalanche of scientists putting forward reasons why the basic premise ("the neutrinos travelled faster than light") is not true.

Also, such is the area of controversy with the experiment, that of the scientists running it, 15 of them actually refused to sign the published document. That's people from within the tent peeing out.

Re: The speed of light : Mon Nov 21, 2011 2:51 pm  

Yes it must be a bit of a dilemma for the scientists involved.
On the one hand, to be associated with this discovery if true would be great.
On the other to dive headlong in and be shown to be a fool if it was found to be unscientific and missing what proved to be a fundamental error would not be great.
After all it is almost inconceivable that a particle can go faster than light, even though light has particle-wave duality.

What gets me is that they are basing these experiments on what is after all a distance that is peanuts compared to the distance light can travel in one second.
It takes, even by my crude calculations, 0.0024 seconds for light to travel 450 miles at 186,000 miles per second.
And they are saying that the neutrinos get there 0.00000006 seconds faster.
Now is any transmitting device, any receiving device, even when coupled up to eliminate lag capable of giving accurate results to these specs? Not reproducible ones, but absolutely accurate ones?
It's asking a lot.
This is more, to my way of thinking, a verification of the of the limit of speed than anything else, within experimental error.
These guys are no mugs, so you presume they know what they are doing.

Re: The speed of light : Mon Nov 21, 2011 4:23 pm  

Ferocious Aardvark wrote:

Not really. To "disprove them" suggests you accept they appear to have "proved" something. Not even they suggest that. Basically they have put their findings out for peer review, and for other scientists to have a go and test them.

Grovelling apologies for use of the word 'disprove'.

Ferocious Aardvark wrote:

And there has been something of an avalanche of scientists putting forward reasons why the basic premise ("the neutrinos travelled faster than light") is not true.

Have any of those reasons been proven? Everyone, including the original team, has been trying to explain the results or find a flaw with the experiment and the data since the news was released. As far as I'm aware the results still stand and have even been repeated under tightened conditions (20 events over 10 days, using pulse bunches only 1-2 nanoseconds long arriving 60 nanoseconds early), although of course years of further tests and scrutiny lie ahead.

Ferocious Aardvark wrote:

Also, such is the area of controversy with the experiment, that of the scientists running it, 15 of them actually refused to sign the published document. That's people from within the tent peeing out.

That's 15 out of around 200 scientists. 4 of whom have now signed the more recent paper. Admittedly, 4 others have now not signed, still leaving 15 names absent. These people know far more about it than the whole of RLFans combined, many times over and while we can discuss it as laymen, they're operating on a level we probably can't even truly perceive.

It would be a fantastic discovery but quite rightly doubt remains even in the face of strong data. As one scientist at OPERA said, "People are exhausted. Everyone should be convinced that the result is real, and they are not."

Re: The speed of light : Mon Nov 21, 2011 4:50 pm  

Cronus wrote:

... These people know far more about it than the whole of RLFans combined, many times over and while we can discuss it as laymen, they're operating on a level we probably can't even truly perceive.
..

Don't drag yourself down so much! I suggest that the perfectly valid possible explanations, such as a dimensional detour by the neutrinos, ought to be addressed and responded to by the team for starters. There are very eminent and very reasonable theories about what is happening and it would be odd if the team put their fingers in their collective ears instead of applying their massive brains to such possible explanations.

And whilst I have a healthy respect for such geeks, there are lots of geeks and boffins outside the team. One of which was Einstein. Are they cleverer than him? And I don't actually see anybody - as in nobody at all - siding with the team. One chap who seems to know a lot about it is Prof Jim al Khalili (of BBC fame) and he says if it is proved right then he will eat his shorts on public TV. From a boffin, that's a pretty startling vote of no-confidence!

Anyway, leaving aside fancy talk of extra dimensions and leaps out of the Universe, the sad and unglamorous fact is that some experimental error is most likely at the bottom of it, as per Occam. One chap with perhaps a fondness for Occam's razor has now published his own findings on the experiment:

Ronald A. J. van Elburg, an who is an AI researcher at the University of Groningen in the Netherlands, suggested that the Opera group had failed to make a relativistic correction for the motions of the GPS satellites used in timing the neutrino beams. The resulting error, he said, amounted to 64 nanoseconds, almost exactly the universe-shaking discrepancy the Opera researchers were hoping to explain.

Now I don't profess he's right, necessarily or this makes the team necessarily wrong. But they got some explaining to do once they get their collective braincells round that one. It sounds a whole lot more likely than the entire laws of physics being disproved.

Mind you what always comes out when you are digging around these subjects is any number of useless but neat factoids. Such as, if you have an average size thumbnail, approx. 100 billion neutrinos whiz through it every second of your life.

Re: The speed of light : Mon Nov 21, 2011 5:34 pm  

Ferocious Aardvark wrote:

Now I don't profess he's right, necessarily or this makes the team necessarily wrong. But they got some explaining to do once they get their collective braincells round that one.

I don't think that survives Occam either tbh. AFAIK the root of what he says is that they didn't account for all the frame of reference errors from the relative motion of the satellites and the earth. But GPS itself does that. The whole system is based on time signals, and microsecond-scale errors mean inaccuracies of multiple hundreds of feet. I'm not sure what kind of scale a timing error of 60ns would entail, but I'm guessing distances larger than that required for military grade uses of GPS.

It may be that there are some other fundamental issues with the GPS time signals, but it's the standard that international atomic time (TAI) is built on and we have a whole host of interesting problems if that's the case.

Also, I'd be astonished if GPS was their only time source.