Cern

[Vile Consort]

Simon, the first anti-matter particle, the positron or anti-electron, was discovered (i.e. observed) in 1932. The evidence for the existence of anti-matter is at least as good as that for the existence of matter on the sub-atomic scale.

The proofs of mathematics, by the way, are 100% perfect. Nobody is going to come along saying they have discovered by careful measurement that 1+1 is in fact slightly different from 2 or an exception to the Intermediate Value Theorem. There may be a question as to how well the mathematics models the real world, of course. That is a different matter.

The mathematics of Special Relativity is really quite simple - first year undergrads can easily understand it. To suggest that Einstein has put together something that is wrong but so difficult to understand that nobody can work out exactly what is wrong with it is just ludicrous.

[David Underdown]

The thought experiments that Einstein used to help him develop the theories of Special and General Relativity are quite easy to understand - and show quite clearly why any other explanation is absurd. The "Uncle Albert" books by Russell Stannard are a good introduction (aimed at teenagers or even younger, but very readable as I recall from my own teenage years)

[Quarky]

All that's needed for light to travel faster in a medium than in vacuo is a refractive index less than unity. The speed of light would tend to infinity as the refractive index approached zero from above. A negative refractive index would presumably mean light came out of the medium before it went in, thus violating the conservation of energy.

Yes you are no doubt exactly correct Vile Consort - as I say it was Martin's idea, not mine.

I don't want to get drawn into scientific arguments, but:

1. for negative refractive index, see http://www.cmth.ph.ic.ac.uk/photonic...JBP_final_.pdf
2. always suspicious of sanctity of mathematical proofs, at least as a means of establishing "truth" - there always seems to be another angle or dimension which supercedes a mathematical theorem. I mean 1+1 = 2 of course, but 1+ i1=?

[MrGongGong]

Sorry Simon, but anti-matter has been produced in the laboratory, albeit with only a few atoms at a time, but enough to prove that it exists.

So that would be 100% more proof than some other beliefs then (Homeopathy, The Resurrection, WMD, UKIP, Father Christmas etc etc )

[Vile Consort]

Yes you are no doubt exactly correct Vile Consort - as I say it was Martin's idea, not mine.

I don't want to get drawn into scientific arguments, but:

1. for negative refractive index, see http://www.cmth.ph.ic.ac.uk/photonic...JBP_final_.pdf
2. always suspicious of sanctity of mathematical proofs, at least as a means of establishing "truth" - there always seems to be another angle or dimension which supercedes a mathematical theorem. I mean 1+1 = 2 of course, but 1+ i1=?

But complex numbers don't supercede the integers. Certainly not in the sense of making theorems about the integers somehow wrong or invalid.

For example, the fact that you can invent a number system in which 2x = 5 has a solution doesn't invalidate the fact that it has no solution among the integers.

[vinteuil]

there always seems to be another angle or dimension which supercedes a mathematical theorem.

But complex numbers don't supercede the integers.

... sheer pedantry, but as this spelling has cropped up twice in this thread - can I point out that it is supersede ? [from sedere, to sit; not cedere, to proceed, to retire]

[Quarky]

Thanks for pointing that out, vinteuil.

Really ought to check my posts more carefully.

[Simon]

I hadn't realised that you were a scientist, Simon. I'd thought of you as more a man of letters. Notwithstanding: it's its proofs, not "it's proofs."

Thank you John. Much obliged. I think if you look through my posts of the past few years, you'll see that I'm aware of such grammatical points. But I can't guarantee not to make typos and absent-minded errors, especially if I post in haste.

[amateur51]

Thank you John. Much obliged. I think if you look through my posts of the past few years, you'll see that I'm aware of such grammatical points. But I can't guarantee not to make typos and absent-minded errors, especially if I post in haste.

Saucer of milk for my friend

[Simon]

It's always good to hear from the scientists on here. I admire those on top of their work - and the fact that it's an area largely foreign to me I think increases my admiration So if you ever think I'm knocking it - I'm not. I work with a superb scientist from time to time - the depth of her knowledge amazes me. But those scientist who say "I can't prove it therefore it doesn't exist" - and there are some - are annoying.

I genuinely didn't know that anti-matter had been produced. What does it look like? is the obvious question.

As regards Einstein's possible error as regards the speed of light, there were some interesting experiments done in the 70s in the USSR with transference, that proved beyond any reasonable doubt that some form of non-physical signal could be passed between humans at a distance. The speed wasn't reliably measured, as even when they tried the distances were so small that it would have been meaningless. But it could - could, I say - have been almost instantaneous - many times faster than the speed of light.

I'm not suggesting that 1=1 can equal anything but 2. I'm simply saying that it's possible to use figures to "prove" different (and conflicting) things. Isn't it?

One final question. If everything that has a finite value can be halved, what is the smallest distance between two objects that they can be apart before that distance cannot be halved because they are touching?

[amateur51]

I'm not suggesting that 1=1 can equal anything but 2. I'm simply saying that it's possible to use figures to "prove" different (and conflicting) things. Isn't it?

By your own example, you have clearly demonstrated it Simon

[Frances_iom]

One final question. If everything that has a finite value can be halved, what is the smallest distance between two objects that they can be apart before that distance cannot be halved because they are touching?

Pauli exclusion principle. This principle states that no two neutrons (or any other fermionic particles) can occupy the same place and quantum state simultaneously so depends on what object you are considering - for real packing denity look up Neutron star - the inner density has been likened to be approximately equivalent to the mass of the entire human population compressed to the size of a sugar cube or 8×10^17 (ie 10 followed by 17 '0's) kg/ per cubic metre (that's 800M tonnes/cubic centimetre)

ETA I assume you are not attempting to play with Zeno's paradox ?

[Vile Consort]

I am not sure enough anti-matter has been produced for anyone to see it with the naked eye. I think if you had a lump of, say, anti-copper it would look just like a lump of copper because light would interact with it in exactly the same way. That, of course, is assuming you can keep it away from any matter.

If you don't keep it away from ordinary matter, then the anti-matter will combine with an equal amount of matter to give a lot of photons - i.e. a massive blast of radiation.

Of course, nobody has managed to produce anything as complicated as a single atom of anti-copper. A few atoms of anti-hydrogen is all we have managed.

[Simon]

Thanks, both of you. Overload of info at the moment!

Please give me a few days...

[Pabmusic]

This is interesting: http://news.sciencemag.org/sciencein...er.html?ref=hp

Tighten a connexion and all the results appear 60 nanoseconds faster.