[QUOTE=Flatlander;275420]For those in the UK only, I believe:
[URL]http://www.bbc.co.uk/iplayer/episode/b016bys2/Faster_Than_the_Speed_of_Light/[/URL]

Favourite bit:
The barman says, "Sorry we don't serve neutrinos".
A neutrino walks into a pub.[/QUOTE]

This is not my favorite physics joke. It's both logically and physically inconsistent.

Logically:

For causality to be violated, and the bartender to know that the neutrino is going to arrive before it actually enters the bar, something has to travel faster than the neutrino. It's not relevant that the neutrino travels faster than light.

Physically:

It assumes that superluminal particles imply violation of causality. In fact, this need not be the case, and it's hard to see how it could even possibly be the case.

Most people have heard of tachyons, hypothetical faster-than-light particles. If you work out the form of the wave packet which is permitted by QED to travel faster than the speed of light, it turns out that the packet must be maximally non-local, i.e., a plane wave that fills all of space. Then the velocity will be superluminal, but of course no information is being transferred because the wave is already everywhere. Any attempt to build a superposition state of tachyon fields that is localized leads to a group velocity for the packet less than the speed of light. In neither case is causality (or locality) violated.

I knew you were going to say that.

Fair enough, but I don't think it was meant to be accurate in any way!

The program talks about FLT, causality etc.
'What if FLT for neutrinos was just the thin end of the wedge' etc.

[QUOTE=sichase;275432]This is not my favorite physics joke. [/QUOTE]

What is?

[QUOTE=wblipp;275445]What is?[/QUOTE]

I can't say I have a favorite physics joke.

But here are a few quotes that I have oft quoted because they amuse me:

Physics is not a religion. If it were, we'd have a much easier time raising money. - Leon Lederman

The question seems to be of such a character that if I should come to life after my death and some mathematician were to tell me that it had been definitely settled, I think I would immediately drop dead again."
- Harry Vandiver [speaking about the infinitude of Wilson primes]

"It is not a simple life to be a single cell, although I have no right to say so, having been a single cell so long ago myself that I have no memory at all of that stage of my life." - Lewis Thomas

Compact electric car produced.
 

[url]http://www.bbc.co.uk/news/science-environment-15637867[/url]

[url=http://www.csmonitor.com/Science/2011/1108/Massive-asteroid-2005-YU55-hurtles-past-Earth-VIDEO]Massive asteroid 2005 YU55 hurtles past Earth[/url]

Apparently passed slightly closer than the moon's orbital distance.

[QUOTE=ewmayer;277837][url=http://www.csmonitor.com/Science/2011/1108/Massive-asteroid-2005-YU55-hurtles-past-Earth-VIDEO]Massive asteroid 2005 YU55 hurtles past Earth[/url]

Apparently passed slightly closer than the moon's orbital distance.[/QUOTE]

Key point about this approach is that it was predicted well in advance
(2005 YU55 was already a multi-opposition object before this latest
close approach) and the uncertainty region at time of closest approach
was small and did not include the earth. The next known approaches of
an object this big will be in 2028 and 2029.

Gareth

A neutrino walks into a bar ...
 

The latest experiment indicates that muon neutrinos are still boldly going where no particle has been known to go before.

[url]http://www.bbc.co.uk/news/science-environment-15791236[/url]

... but the barman is Pavel Alekseyevich Cherenkov!!
 

... or Oliver Heaviside, if you prefer.

[QUOTE=xilman;279058]The latest experiment indicates that muon neutrinos are still boldly going where no particle has been known to go before.

[URL]http://www.bbc.co.uk/news/science-environment-15791236[/URL][/QUOTE]Now, it turns out that last month another team deduced that the OPERA team's neutrinos could not be FTL -- [I]because they weren't emitting the neutrino analog of Cherenkov radiation. (Of course!)[/I]

[URL]http://arxiv.org/abs/1110.3763v2[/URL]

[URL]http://www.reuters.com/article/2011/11/20/us-science-neutrinos-idUSTRE7AJ0ZX20111120[/URL]

[QUOTE=cheesehead;279457]... or Oliver Heaviside, if you prefer.

Now, it turns out that last month another team deduced that the OPERA team's neutrinos could not be FTL -- [I]because they weren't emitting the neutrino analog of Cherenkov radiation. (Of course!)[/I]

[URL]http://arxiv.org/abs/1110.3763v2[/URL]

[URL]http://www.reuters.com/article/2011/11/20/us-science-neutrinos-idUSTRE7AJ0ZX20111120[/URL][/QUOTE]I'm not convinced, given my limited understanding of the Čerenkov effect.

AIUI, a particle capable of interacting with a medium travelling faster than the local maximum speed of travel in that medium will emit Čerenkov radiation because it loses energy through scattering within the medium. So something with an appreciable interaction with an elastic medium travelling faster than sound will emit phonons; a particle which interacts through the electromagnetic interaction will emit photons, and so on

Either of my previously posited explanations appear immume to the Čerenkov explanation. That doesn't, of course, mean that either is correct and there is, indeed, a powerful argument against one of them.


Paul

Shakespeare walks into the pub
 

You're bard.

Who ordered that?

Fermi