Dumb question about the big bang

Originally posted by C Hess
I love this place. I do. Thank you for clarifying these things.

Just one question. If you have a "fountain" of particles shooting out from a fixed location, wouldn't the effect be the same as during the initial big bang, a rapid expansion outwards from that infitesimally small point? Wouldn't that make it possible for one (particles or anti-particles) to c ...[text shortened]... parently younger galaxies appear where they should be older, and vice versa. I didn't know that.

The difficulty with your first sentence is that that doesn't adequately describe the early universe. Space started to expand, any matter content was dragged along, this is different from a fountain of particles spraying out into a space that already exists. In the early universe most particle cosmologists believe that there was a period of extremely rapid expansion called inflation during which most of the matter was produced. For some reason not understood more matter than anti-matter existed and that difference accounts for the matter in the universe now.

If you want a very old or eternal universe with slow creation then weak CP violation could conceivably account for the matter/anti-matter imbalance. I doubt that a workable model could be constructed though. Measurements of Type Ia supernovae indicate that the expansion of the universe is accelerating which would seem to present problems for any theory based around continuous creation.

The closest that could be managed is a universe that alternates between inflationary "big rip" phases followed by slow expansion. Such a theory would have to account for why the inflationary phases stop and start. Dark energy could conceivably provide a mechanism, but since no one knows what it is it's not even just a theory.

Originally posted by DeepThought
I don't know enough about observational astronomy to say this with any high degree of infallibility. However, by looking at the spectroscopic properties of stars one can tell their metalicity, metals in astronomy are all elements heavier than helium, so carbon and oxygen are metals to an astronomer. There are three populations of stars population I whi ...[text shortened]... find highly likely, then it will have been done on statisically significant numbers of galaxies.

Okay, thank you for your input.

Originally posted by DeepThought
...the sun is a population I star [...] Population I stars are hypothetical, no one has ever observed them

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Originally posted by C Hess
Is it possible that the universe is infinately large, and that new matter is constantly being produced from one or more points and expanding outwards, continuously producing new galaxies and such? Like a fountain constantly feeding new particles into the universe? So that "the big bang" is a continuous process?

What you're describing is a kind of a mix between the steady state theory (from Fred Hoyle and is gang. Coincidentally it was Fred Hoyle who coined the term the Big Bang in a dismissive way. Lemaitre who was a priest and the originator of the Big Bang idea called the Primeval Atom) and the eternal inflation scenarios (or models if you prefer).

Basically the steady state model says that matter is continuously being created in space so that it keeps the density of the whole Universe constant.

Eternal inflation models posit that everywhere in the Universe big bangs are always occurring and that new universes are continuously being created.

Originally posted by C Hess
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I think it's back to front as well. Astronomical categories are based on what can be observed, not the theories about their properties. That way, if the theory changes they don't need to rewrite the entire star catalogue. It's probably based on how many there are, population I having the most members currently.

Originally posted by DeepThought
I think it's back to front as well. Astronomical categories are based on what can be observed, not the theories about their properties. That way, if the theory changes they don't need to rewrite the entire star catalogue. It's probably based on how many there are, population I having the most members currently.

I think he was questioning your statement that the sun is a population I star but Population I stars are hypothetical, a self-contradicting statement.

Originally posted by sonhouse
I think he was questioning your statement that the sun is a population I star but Population I stars are hypothetical, a self-contradicting statement.

I see, that was a typo. It should have read: "Population III stars are hypothetical.". It doesn't seem to matter how carefully I proof-read what I type in there's always an error somewhere in every post I make.

Originally posted by DeepThought
I see, that was a typo. It should have read: "Population III stars are hypothetical.". It doesn't seem to matter how carefully I proof-read what I type in there's always an error somewhere in every post I make.

Don't feel like the Lone Ranger🙂

What are the theoretical properties of a type III star anyway?

Originally posted by sonhouse
Don't feel like the Lone Ranger🙂

What are the theoretical properties of a type III star anyway?

The basic difference between stellar populations is the metalicity. The population III stars were formed when there was nothing in the universe but hydrogen and helium. They were the first stars so they burnt using the proton proton chain only while on the main sequence. One notion is that they could be very massive. For population I stars there's a theoretical limit of about 140 solar masses. Stars larger than about 3 solar masses burn using the CNO cycle which is more efficient, if the initial mass exceeds around 140 solar masses their solar wind is powerful enough to blow off their outer layers, so the mass comes down to 140. I think that this is believed not to be the case for population III stars, or if there is an upper mass limit it is higher. Because some of them were so massive they had very short life times, of the order of a million years, and seeded the universe with metals for the population II stars. It's possible that population III red dwarfs are still around, but no one's seen one as far as I know. The oldest star known is SM0313 (but see the introduction to the Wikipedia article [1]) and it is population II, not III, despite having an age of 13.6 billion years.

[1] http://en.wikipedia.org/wiki/SMSS_J031300.36-670839.3