The Hunt For Dark Matter

Let me start by saying that I'm no Ph. D. I have some aptitude with math but not anywhere close to people who are studying the science close up.

Anyhoo, dark matter - everybody's looking for it. Is there any literature that suggests that dark matter/dark energy is space-time itself?

Originally posted by sasquatch672
Let me start by saying that I'm no Ph. D. I have some aptitude with math but not anywhere close to people who are studying the science close up.

Anyhoo, dark matter - everybody's looking for it. Is there any literature that suggests that dark matter/dark energy is space-time itself?

Actually there are quite few physicists actively looking for dark matter/energy.

And no, it is not "space-time itself", although I'm not sure what you mean by that. How do you define whether something is "space-time itself"?

Originally posted by sasquatch672
Anyhoo, dark matter - everybody's looking for it. Is there any literature that suggests that dark matter/dark energy is space-time itself?

Dark matter is known about because its gravity has a measurable effect on galaxies and galaxy clusters. The dark matter is clearly not uniformly distributed throughout the universe.

Has dark matter and dark energy anything in common? Or is it different things altogether?

As I see it (but I can very well be wrong on this) dark matter is everything with mass you don't see, like ordinary matter with protons and neutrons and electrons and stuff, but cold and dark. And exotic matter made up of particles that we don't know much about, like funny combinations of quarks or something made up from something unknown.

Whereas dark energy is something completely different, like strange fields of some strange energy, with some strange properties, that interact with normal space and matter in a strange way that distorts our understanding of cosmos in large.

So should we discuss dark matter and dark energy in the same debate?

Originally posted by FabianFnas
As I see it (but I can very well be wrong on this) dark matter is everything with mass you don't see, like ordinary matter with protons and neutrons and electrons and stuff, but cold and dark. And exotic matter made up of particles that we don't know much about, like funny combinations of quarks or something made up from something unknown.

Dark matter isn't just matter that we don't see, its matter that we don't understand. For example, we generally can't see planets in other galaxies, but we can nevertheless estimate how many should be there, and what mass they are, and thus they are not dark matter.
Basically we look at a galaxy, work out how much matter we think it should have based on observation and our knowledge of galaxies, then, the difference between that, and the observed gravitational attraction of that galaxy must be contributed by something as yet unknown. That unknown is the 'dark matter'.

Whereas dark energy is something completely different, like strange fields of some strange energy, with some strange properties, that interact with normal space and matter in a strange way that distorts our understanding of cosmos in large.
The concept of dark energy is the same as that of dark matter ie we have reason to think there is more energy out there, but we haven't identified what it is or where it is.

So should we discuss dark matter and dark energy in the same debate?
I don't see why not. The actual phenomena may be totally unrelated, but they still fall under the heading 'not yet fully understood large scale physics'.

Originally posted by twhitehead
Dark matter is known about because its gravity has a measurable effect on galaxies and galaxy clusters. The dark matter is clearly not uniformly distributed throughout the universe.

Isn't it that dark matter is known to the extent that positing just so much of it reconciles some calculations with some observations?

Originally posted by JS357
Isn't it that dark matter is known to the extent that positing just so much of it reconciles some calculations with some observations?

That's how I've always understood it. You could call it unicorn farts, if you were so inclined.

Originally posted by twhitehead
Dark matter is known about because its gravity has a measurable effect on galaxies and galaxy clusters. The dark matter is clearly not uniformly distributed throughout the universe.

You wouldn't expect dark matter to be uniformly distributed, would you? Light matter isn't...

I suppose what I'm on about is the possibility that early astrophysicists were correct when they theorized the ether. Space isn't empty. What we can't seeia the broth of the universe.

Just a crackpot uninformed idea.

Originally posted by JS357
Isn't it that dark matter is known to the extent that positing just so much of it reconciles some calculations with some observations?

Dark matter is any matter that we think is there due to some observation, but for which we have no current explanation.

We can for example detect black holes at the center of galaxies by tracking the motions of stars in the region. We can work out their masses without ever seeing them. But we know what a black hole is, so they do not come under the heading 'dark matter'.
However, when we track the motions of stars throughout a galaxy, it appear there is some mass spread out throughout the galaxy, that is not accounted for by known phenomena. This then is called 'dark matter'.

Originally posted by sasquatch672
You wouldn't expect dark matter to be uniformly distributed, would you? Light matter isn't...

I suppose what I'm on about is the possibility that early astrophysicists were correct when they theorized the ether. Space isn't empty. What we can't seeia the broth of the universe.

Just a crackpot uninformed idea.

My point was that space-time presumably is uniformly distributed. Or maybe it isn't. Gravity curves space-time, so maybe space-time is more compact around galaxies and thus contributes more mass.
But I think you would need to do more calculations to see if this makes any sense - and I am certainly not up for the task.

Originally posted by twhitehead
Dark matter is any matter that we think is there due to some observation, but for which we have no current explanation.

We can for example detect black holes at the center of galaxies by tracking the motions of stars in the region. We can work out their masses without ever seeing them. But we know what a black hole is, so they do not come under the hea ...[text shortened]... out the galaxy, that is not accounted for by known phenomena. This then is called 'dark matter'.

What about a background density of intergalactic neutrons? One in every cubic centimetre would certainly be measurable in their gravitational interaction, but not in electromagnetic interaction. Hence invisible = dark, but still act gravitationally, meaning dark matter.

Or is dark matter only exotic/strange matter of unknown non-fermionic kind?

Originally posted by twhitehead
Dark matter isn't just matter that we don't see, its matter that we don't understand. For example, we generally can't see planets in other galaxies, but we can nevertheless estimate how many should be there, and what mass they are, and thus they are [b]not dark matter.
Basically we look at a galaxy, work out how much matter we think it should have ba ...[text shortened]... unrelated, but they still fall under the heading 'not yet fully understood large scale physics'.[/b]

"Dark matter isn't just matter that we don't see, its matter that we don't understand."

I tend to believe most dark matter is black holes. There are probably more of them than people realize. I'm sure there are many at the center of every galaxy. We understand them to an extent although we will never understand everything about them.

Originally posted by FabianFnas
What about a background density of intergalactic neutrons? One in every cubic centimetre would certainly be measurable in their gravitational interaction, but not in electromagnetic interaction. Hence invisible = dark, but still act gravitationally, meaning dark matter.

Or is dark matter only exotic/strange matter of unknown non-fermionic kind?

If we know there is a background density of neutrons, then we factor it into our equations and we know what it is, and hence not dark matter.
If we do not know of such a background density, but it does exist, then it is dark matter.
'dark matter' refers to the fact that we do not yet know what it is.

Did you possibly mean 'neutrinos'? I believe neutrons would interact in a detectable way.

Originally posted by Metal Brain
I tend to believe most dark matter is black holes. There are probably more of them than people realize. I'm sure there are many at the center of every galaxy. We understand them to an extent although we will never understand everything about them.

We can work out the amount of mass present at the center of a galaxy and its location from the motion of stars near the center. Such mass is already attributed to black holes.
http://en.wikipedia.org/wiki/Supermassive_black_hole

There may be black holes distributed throughout the galaxy that are not being taken into account, but I do not think it is a significant contribution to dark matter.

'Dark matter' is distributed throughout galaxies and extends beyond the visible parts of galaxies. It doesn't behave like stars, so it is unlikely that it is black holes.

Originally posted by twhitehead
If we know there is a background density of neutrons, then we factor it into our equations and we know what it is, and hence not dark matter.
If we do not know of such a background density, but it does exist, then it is dark matter.
'dark matter' refers to the fact that we do not yet know what it is.

Did you possibly mean 'neutrinos'? I believe neutrons would interact in a detectable way.

No, I meant neutrons, of some reason. Just a neutral particle that doesn't give radiation of themselves. Some of them but a relatively big mass means something in gravitational effect.

But then we also have neutrinos. Small mass times many of them means considerable gravitational effect.

So a 'definition' of dark matter is "some particle of a kind we don't know has a gravitational measurable effect"? So when it becomes known of what particle the dark matter consists, then it is not dark matter anymore?

This is very interesting, very exciting indeed. But sometimes I hear scientists try to over-explain things by mention dark matter or dark energy, when there is infact a simpler, but yet unknown explanation.