It's light Jim, but not as we know it...

[d000hg]

I was beginning to doubt my memory about everything travelling at c in space-time according to relativity, so looked it up (I'm still not confident with the rest of my answer however)

I'm not convinced that argument is other than a different thought-construct, another way to view things. Same as Feynman diagrams... they are not literally saying anti-particles travel backwards in time but it is a nice way to think about things.

[TimberWolf]

I'm not convinced that argument is other than a different thought-construct, another way to view things. Same as Feynman diagrams... they are not literally saying anti-particles travel backwards in time but it is a nice way to think about things.

Absolutely, they are philosophical interpretations [of experiment] codified into mathematics, with the assumption being that nature is consistent, as is mathematics and hence can be taken further by mathematics or by other logical means and tested and used. Nature isn't really like that and may not even be consistent outside of our experiences of it. The 4th time dimension and its intimate link with the 3 space dimensions was a logical consequence of a universal speed c, a postulate of Special Relativity.

[d000hg]

Ah, but relativity allows you to travel further in your own time than under Newton. Though a side-effect is that everyone ages differently around you when you move relative to them. So in one sense you could traverse the universe within your own life-time (which would be impossible under Newton), but in another realer sense by the time you got there and slowed back down a lot of time would have passed in this new 'inertial frame'. So going less than the speed of light by some small fraction isn't a restriction. Going faster than light...who knows what that's all about.

It doesn't really make sense, not to the person doing the travelling anyway, because in their perception travelling at the speed of light is to travel instantaneously. At least so my previous thought-train would claim... still not quite sure about that.

[TimberWolf]

It doesn't really make sense, not to the person doing the travelling anyway, because in their perception travelling at the speed of light is to travel instantaneously. At least so my previous thought-train would claim... still not quite sure about that.

It doesn't make sense at the speed of light, for a massive objects, and this isn't allowed by SR. But at any speed less than light, the laws of physics are the same as at rest, including for watches. Recall there's no such thing as a speed of an object, its not an intrinsic attribute of an object, it's a speed with respect to something. A person travelling at 0.999999c relative to something might be going 0 according to something else, etc, etc. and a wristwatch works exactly the same at all speeds. As do all wristwatches, all tick locally at the same rate. The posh word for this wristwatch time is 'proper time', and it's also an invariant though not much used in SR. It's everyone else's watches that go at a different speeds.

For the traveller who reaches a destination (traversing a 'proper distance') in less time than light would have taken to travel that same proper distance, SR says the distance has contracted.

[TimberWolf]

For the traveller who reaches a destination (traversing a 'proper distance') in less time than light would have taken to travel that same proper distance, SR says the distance has contracted.

Actually I should add, that description above was from the perspective of our traveller: his watch ticks at a normal rate to him, but the distance to his destination is contracted and he sees destination clocks moving more quickly. They are ageing faster than him.

For observers though, the distance he's travelling is not contracted and the travellers watch is moving more slowly.

A third perspective more favoured in modern SR terms, is the invariant 4D space-time interval. In this view the 4D interval is agreed by everyone.

[TimberWolf]

Some comments are starting to appear in newsgroup sci.physics.research now. It's is a moderated group and used to have some quite clued-up (and relatively famous) people posting.

fast neutrinos? - sci.physics.research | Google Groups

I like the comments so far, one freely mixes feet and kilometres, a foot and nanosecond. Those Yanks...

[NotAllThere]

Maybe there's a small lump of neutronium buried under the alp, since strong gravity fields exert a relativistic effect... but IIRC, that'd make the neutrinos arrive later than expected... wouldn't it?

A fragment of cosmic string could shorten the actual distance. A tiny bit of space where there's fewer than 2 Pi radians in a circle.

[d000hg]

Actually I should add, that description above was from the perspective of our traveller: his watch ticks at a normal rate to him, but the distance to his destination is contracted and he sees destination clocks moving more quickly. They are ageing faster than him.

If you travel to a far star and back at .999c in my perspective, you travel at .999c for X time. For you it takes less than X time (as you say I age in your eyes) therefore you perceive to cover the distance faster than c.
So you could travel to another galaxy in a week, in your frame of reference, without breaking any laws - that's the crux of my point.

[d000hg]

They really need to drill a tunnel and send a laser, and see what happens.

[TimberWolf]

They really need to drill a tunnel and send a laser, and see what happens.

The most sensible suggestion I've seen so far relates to a question on whether they could use a neutrino detector much closer to the source, i.e. at CERN, and see if the anomaly still exists. I thought this was what the guy who was hosting the seminar asked at the end at question time, but I may have misheard. Anyway the guy representing the work nodded as if to say, yes we could do that. I don't know whether CERN has one though, they aren't small. I think I must have misheard, because they would have done it before publishing.