Antimatter's role in the architecture of the universe

[Chalnoth]

OK, but they state, "The second mission will improve on these measurements and will also search for complex antimatter nuclei (anti-Helium, anti-Carbon, etc)." It seems there IS some expectation of finding anti-matter nuclei. In addition, there is also the statement "Essentially, during the big bang there were equal amounts of matter and antimatter," althought they also state, "Now we can't see any significant amounts of antimatter." It seems there is some expectation of finding some amount, not necessarily signficant, of antimatter. Or is it just a hope or fanciful wish?

I don't think they have any realistic expectation of finding these things. If they do, they don't know much about cosmology (which wouldn't be a terrible surprise, if they're all high-energy people). But it's always good to test these things to death, as we never know when something unexpected is going to crop up.

 

[Astronuc]

I don't think they have any realistic expectation of finding these things. If they do, they don't know much about cosmology (which wouldn't be a terrible surprise, if they're all high-energy people). But it's always good to test these things to death, as we never know when something unexpected is going to crop up.

Even so - from "Shuttle experiment tries to detect antimatter"
http://web.mit.edu/newsoffice/1998/ams-0603.html

Professor Ting hopes to detect heavy antimatter nuclei of anticarbon or antihelium. An antimatter nucleus could signal the presence of a far-off antimatter galaxy because, unlike positrons and antiprotons, these heavy antiparticles are too massive to have resulted from interstellar particle collisions. An antihelium nucleus would prove that some antimatter survived the Big Bang. An anticarbon nucleus could mean that antistars exist, because carbon and heavier elements are created only in stars.

Now it maybe that particle physicists don't know much about cosmology - but some are certainly looking for evidence of the existence of antimatter in galactic quantities (I expect a star of anti-matter doesn't exist in isolation in a matter galaxy).

I expect that many of the AMS team are HEP and not necessarily astrophysicists.

 

[Chalnoth]

Even so - from "Shuttle experiment tries to detect antimatter"
http://web.mit.edu/newsoffice/1998/ams-0603.html

Now it maybe that particle physicists don't know much about cosmology - but some are certainly looking for evidence of the existence of antimatter in galactic quantities (I expect a star of anti-matter doesn't exist in isolation in a matter galaxy).

One thing you've got to realize is that physicists look for things they don't expect to find all the time.

 

[Carid]

Three pages of bright and vigorous debate about antimatter and the fact that cosmologists, astrophysicists and high energy physicists may not be singing from the same hymnbook. And all because I couldn't finish reading a popular science rag at the airport. Sweet!

 

[Chalnoth]

Three pages of bright and vigorous debate about antimatter and the fact that cosmologists, astrophysicists and high energy physicists may not be singing from the same hymnbook. And all because I couldn't finish reading a popular science rag at the airport. Sweet!

Er, well, scientists in general tend to disagree on all sorts of things. But if you press most any physicist who knows anything about the relevant fields (there are always a few fringe exceptions), I can guarantee that you'll find nearly all of them agreeing here that actual detection of a significant number of helium and heavier anti-matter particles is extremely unlikely.

 

[Vanadium 50]

Of course "extremely unlikely" and "observationally excluded" are two different things. Usually it works out as expected, but every once in a while you spot a coelacanth. One of the most recent astrophysical surprises was planets orbiting pulsars.

Anyway, AMS-02 will settle things one way or the other. It's been given the green light for STS-134, whenever that will happen.

 

[Chalnoth]

Of course "extremely unlikely" and "observationally excluded" are two different things.

They're not different at all from where I'm standing. Experimental results are never perfect. There are always errors. And thus 'observationally excluded' always breaks down to 'extremely unlikely'.

Usually it works out as expected, but every once in a while you spot a coelacanth. One of the most recent astrophysical surprises was planets orbiting pulsars.

This would be more than a little bit different than spotting a coelacanth.