OT: Lost in the Galaxy? No wonder.

[narf poit chez BOOM]

I found it interesting.

[dogscoff]

Renegade 13 said:
There simply isn't enough baryonic ("normal") matter to account for all the gravitational effects we observe
....
Scientists now predict that "normal" baryonic matter, of which you and I are all made, composes merely 4 or 5% of the universe.

But if, as the original post says, there's twice as much baryonic matter in galaxies as previously thught, then you don't need as much dark matter to make all the gravitational calculations add up. Make that 4%-10% of the universe made up of baryonic matter.

[Renegade 13]

dogscoff said:

But if, as the original post says, there's twice as much baryonic matter in galaxies as previously thught, then you don't need as much dark matter to make all the gravitational calculations add up. Make that 4%-10% of the universe made up of baryonic matter.

Good point!

Narf: I'm glad you found it interesting

[EvilGenius4ABetterTomorro]

So, I was just thinking; Dark Matter must be invisible because if there is so much of it, why doesn't it interfere with our observation of other stellar objects like other galaxies. You don't hear someone say "I was watching Mars last nite when suddently an orb of dark matter blocked my view"

Dark Matter, Anti-Matter,and little lambs eat ivy.

[Renegade 13]

EvilGenius4ABetterTomorro said:
So, I was just thinking; Dark Matter must be invisible because if there is so much of it, why doesn't it interfere with our observation of other stellar objects like other galaxies. You don't hear someone say "I was watching Mars last nite when suddently an orb of dark matter blocked my view"

Dark Matter, Anti-Matter,and little lambs eat ivy.

Possibilities for dark matter: It interacts very little or not at all with normal matter. Or it is composed more of particles than large "blobs" of matter like an asteroid or planet or star. Neutrino's for example are hugely abundant, but very hard to detect, and also make up a portion of dark matter. If there's more particles like the neutrino out there, they possibly wouldn't be easily detected but could make up a large part of dark matter.

Anti-matter is another subject, but I'll save that for another time

[narf poit chez BOOM]

Look up 'Anti-Protons'. Basically, protons with a negative charge. Apparently, if you smash a proton and an anti-proton, there's a 100% energy release, or really close to it.

[Renegade 13]

Anti-particles also have a different spin (I think), due to certain factors that are beyond my comprehension.

[Karibu]

EvilGenius4ABetterTomorro said:
So, I was just thinking; Dark Matter must be invisible because if there is so much of it, why doesn't it interfere with our observation of other stellar objects like other galaxies. You don't hear someone say "I was watching Mars last nite when suddently an orb of dark matter blocked my view"

Dark Matter, Anti-Matter,and little lambs eat ivy.

There's also this assumption, that dark matter in the galaxy is spread on far wider area than normal matter. Scientists call it the "dark matter halo" of galaxy. For example, the diameter of our galaxy is considered to be about 100 000 light years. The diameter of dark matter in our galaxy is assumpted to be around million light years. Which is effectively 10 times more than visible matter in our galaxy. Perhaps you know more of this, Renegade?

[Wolfman77]

Renegade 13 said:
Anti-particles also have a different spin (I think), due to certain factors that are beyond my comprehension.

Anti-particles have the same spin, but opposite charge. I'm not sure what all the details are about spin. It's a rather confusing subjuect to me at times. This helps a bit though.

http://en.wikipedia.org/wiki/Image:Particle_chart.jpg

I think Baryons, which are made up of 3 quarks have odd spins like 1/2 or 3/2 and so on. They make up normal matter like protons and neutrons.

Mesons have 2 quarks and have even spin like 0 or 1. Some mesons can be their own anti-particle. Here is a quick site.
http://www2.slac.stanford.edu/vvc/theory/hadrons.html

Mesons also don't obey the "Pauli exclusion principle" which I think mostly says 2 particles can't occupy the same state. Thats part of what keeps electrons, which are Baryons, separated in their electron configurations. Here's more on that
http://education.jlab.org/qa/electron_config.html

I think I read somewhere that mesons, since they don't obey the Pauli exclusion principle, don't interact with most matter, and were hard to detect because of this. If dark matter is made up of these particles then it would be hard to find.

Black holes, now thats a whole other suject...

Anyway, I'm sure there is more I didn't say but my fingers are getting sore from typing for now. Hope some of you find this interesting.

[Renegade 13]

Karibu said:
There's also this assumption, that dark matter in the galaxy is spread on far wider area than normal matter. Scientists call it the "dark matter halo" of galaxy. For example, the diameter of our galaxy is considered to be about 100 000 light years. The diameter of dark matter in our galaxy is assumpted to be around million light years. Which is effectively 10 times more than visible matter in our galaxy. Perhaps you know more of this, Renegade?

Nope, I don't really know more than that. Just that they call the hypothetical dark matter halo objects MACHO's (Massive Compact Halo Objects).

Oh, I just remembered something more. Some candidates for dark matter:

SIMP's (Strongly Interacting Massive Particles): They interact with normal matter strongly, but still are thought by some to form at least a part of dark matter. Hypothetical Particel! Not proven to exist yet. SIMP Link (not much info)

WIMP's (Weakly Interacting Massive Particles): Another hypothetical particle that only interacts with normal matter through the weak nuclear force and gravity. Since they (theoretically) don't interact through electromagnetism or the strong nuclear force, they can't be seen directly, or interact with atomic nuclei. NOTE: Most of the above paraphrased from Wikipedia. WIMP Info Link

Neither of the above have been proven to exist yet, to the best of my knowledge.

Don't you just love particle physics?

Anti-particles have the same spin, but opposite charge.

Thanks for correcting me Wolfman