I don't understand Cosmology! (hell, bible, God, verse, Articles)

[Halcyon]

I watched a documentary last night that confused the hell out of me.

It started off explaining that we can only see a small portion of the universe because we exist within an observational bubble, that is, we can't see any objects further than 15 billion light years away because the universe is only 15 billion years old.
Ok, that makes sense.

Then it went on to explain how this guy had invented a program to "weigh" the universe by counting all the galaxies we can see. And it turned out that there was not enough matter in the universe for the universe to actually exist, so they made up dark matter to account for the discrepancy.

What I don't understand is how anyone can count and/or estimate the number of galaxies in the universe if we are limited by our observational bubble?
And, since we are limited in our observations and so may only be seeing a tiny fraction of the total matter in the greater universe, isn't it presumptous to invent dark matter to account for the missing matter when the matter may not be missing at all, just beyond our field of vision?

Can anyone explain this to me please?

[Mr Spinkles]

It's not the amount of matter per se that's important, but the matter density.

There is a big discrepancy between the density of observed matter in the universe and the rate of cosmic expansion--the extra energy required to account for the rapid expansion is unknown and it is called "Dark Energy".

There is also a big discrepancy between the amount (read: density) of observed matter in galaxies and the rotation of galaxies. The extra matter required to account for the rotation of galaxies is not known and is called "Dark Matter". There are other discrepancies that give evidence for Dark Matter, too. The prime candidates for Dark Matter are so-called Weakly-Interacting Massive Particles, or WIMPS, that have been predicted theoretically but have yet to be observed. They are like ghosts--they just pass through everything nearly all of the time, so to detect them you have to build large underground detectors, then wait for a tiny flash of light.

In total, the energy of the universe is estimated to be 30% Dark Matter (remember matter is a form of energy), and something like 65% Dark Energy. That means only 5% of the energy in the universe is in a form we have studied (light, protons, neutrons, electrons, etc.)!

[Sunstone]

Don't listen to Mr. Spinkles, Halcyon! He's a physics student and he'll only mislead you! Read the Bible for answers! It's the only way!

[Halcyon]

Originally Posted by Mr Spinkles

It's not the amount of matter per se that's important, but the matter density.

There is a big discrepancy between the density of observed matter in the universe and the rate of cosmic expansion--the extra energy required to account for the rapid expansion is unknown and it is called "Dark Energy".

There is also a big discrepancy between the amount (read: density) of observed matter in galaxies and the rotation of galaxies. The extra matter required to account for the rotation of galaxies is not known and is called "Dark Matter". There are other discrepancies that give evidence for Dark Matter, too. The prime candidates for Dark Matter are so-called Weakly-Interacting Massive Particles, or WIMPS, that have been predicted theoretically but have yet to be observed. They are like ghosts--they just pass through everything nearly all of the time, so to detect them you have to build large underground detectors, then wait for a tiny flash of light.

In total, the energy of the universe is estimated to be 30% Dark Matter (remember matter is a form of energy), and something like 65% Dark Energy. That means only 5% of the energy in the universe is in a form we have studied (light, protons, neutrons, electrons, etc.)!

Ok, that helps a lot, thanks Spinks. I still have loads of questions though.

From what you say, it sounds like dark matter isn't actually matter as I typically think of it, as in neutons, protons and electrons, but is some form of subatomic particle, right?
Is it believed to actually be dark, as in does it absorb instead of reflect light? Or does the name not reflect the particles in that sense?

Are WIMPS affected by gravity?

If the universe is expanding due to the effects of dark energy, wouldn't the energy have the same effect on the atoms of our bodies, shouldn't we be expanding too?

The documentary talked about the universe either being flat or curved, and that dark matter/energy allows for the universe to be flat, whereas visible energy alone wouldn't be enough even to hold it flat. What's it talking about? What role does matter have in shaping spacetime in this manner?
I mean, I know that matter curves spacetime, but what would happen to spacetime if there were no matter present?

Sorry if these are stupid questions, I'm rubbish with physics.

[Halcyon]

Originally Posted by Sunstone

Don't listen to Mr. Spinkles, Halcyon! He's a physics student and he'll only mislead you! Read the Bible for answers! It's the only way!

Ah, I see you've been watching too much GOD TV again Phil. I believe beer helps when in such a predicament.

[Don Penguinoini]

Sunstone... Sicne the earht is in teh middle i tell you!

[Somkid]

Originally Posted by Sunstone

Don't listen to Mr. Spinkles, Halcyon! He's a physics student and he'll only mislead you! Read the Bible for answers! It's the only way!

You funny

[Kungfuzed]

This dark energy theory sounds a bit metaphysical to me. Could it be that the laws of gravity work different at greater distances? Next thing you know they'll be comming up with a light energy that supports life and that everyone can see. Oh wait...