Is the big bang an accurate name for the beggining of the universe?

[brianb]

dark matter may be the matter constructed from anti-energy

Anti-energy would necessarily have a negative mass (if it existed) by a straightforward application of Special Relativity. Dark matter has a positive mass; otherwise there would be no need to posutlate its existence.

Anti-atoms tend not to hang around long enough to have experiments performed on them; even the components are short lived as they inevitably meet their matter cohorts and mutually annihilate. But the energy states in a anti-hydrogen atom (comprising an antiproton nucleus and a positron) are exactly the same as the energy states in a hydrogen atom. Emission & absorbtion spectra would be identical.

If we were able to communicate with an alien intelligence, there's no way in principle that we could determine whether they were made of matter or antimatter. Even partity-breaking experiments like the preferred direction of decay particles from supercooled cobalt don't help. The only thing that you can do with such experiments is to communicate to the alien what you mean by "left" and "right". Then, if you should ever chance to meet in person, be very wary indeed of any alien who extends his left hand for the greeting handshake....

[AlexB]

Then, if you should ever chance to meet in person, be very wary indeed of any alien who extends his left hand for the greeting handshake....

Thanks for the info.

Do you know if sub-atomic particles can exist in some configuration without actually becoming an atom?

[themos]

Do you know if sub-atomic particles can exist in some configuration without actually becoming an atom?

Yes, all the time! If you heat up atoms they can't stay together and eventually all their constituents go their own way.

[AlexB]

Yes, all the time! If you heat up atoms they can't stay together and eventually all their constituents go their own way.

Does this infer that they have too much energy to stay as elemental particles en-masse?

[themos]

You can view an atom, in some sense, as a solar system, with captive planets being the constituent sub-atomic particles. At high temperatures, these particles are likely to receive such a violent kick that they get ejected from the system and are not captive anymore.

So, bound systems can only remain bound if they don't absorb enough energy.

[AlexB]

What I'm getting at is, can you have quarks, fermions and electrons floating about in space in a cloud that does not bond into atoms?

[brianb]

What I'm getting at is, can you have quarks, fermions and electrons floating about in space in a cloud that does not bond into atoms?

Only if the temperature is very, very high indeed ... and not for long either, naked quarks are very unstable and decay in a timescale of attoseconds.

[themos]

brianb, is the phase structure of QCD fully known? I thought it was still an open problem..

[brianb]

is the phase structure of QCD fully known? I thought it was still an open problem..

Best ask the people that run Fermilab & the Large Hadron Collider, but without that information they're totally wasting their time looking for events at even higher energies.