Dark energy

[The Sauce]

Is it possible that dark energy is simply all of the energy that dark matter absorbs which, since it is dark and absorbs all light, is close to all of the energy created in the universe?

 

[Gibsons]

Dark matter isn't thought to absorb light. I guess "dark" might be a misnomer.

 

[SphinxnihpS]

Is it possible that dark energy is simply all of the energy that dark matter absorbs which, since it is dark and absorbs all light, is close to all of the energy created in the universe?

Based on the currently accepted expansion rate of the universe and currently accepted mass of the universe, scientists know that the equation does not explain the fantastic rate at which the universe is expanding, nor can they explain why this rate is accelerating. This is why they came up with the term Dark Energy. It is the unknown force responsible for the difference between how fast the universe is expanding and how fast it should be expanding.

Dark matter has no known interaction with normal matter or energy except gravitationally. You can not see or touch it, but it is there. There may be some dark matter in or around you right now.

 

[disappoint]

Based on the currently accepted expansion rate of the universe and currently accepted mass of the universe, scientists know that the equation does not explain the fantastic rate at which the universe is expanding, nor can they explain why this rate is accelerating. This is why they came up with the term Dark Energy. It is the unknown force responsible for the difference between how fast the universe is expanding and how fast it should be expanding.

Dark matter has no known interaction with normal matter or energy except gravitationally. You can not see or touch it, but it is there. There may be some dark matter in or around you right now.

I agree with everything you wrote except the bolded part. Dark matter around you is unlikely. Ever heard of a gravity wave observatory? You yourself said dark matter interacts with normal matter/energy gravitationally.
So far we have yet to pick up anything from gravity wave observatories.

 

[SphinxnihpS]

I agree with everything you wrote except the bolded part. Dark matter around you is unlikely. Ever heard of a gravity wave observatory? You yourself said dark matter interacts with normal matter/energy gravitationally.
So far we have yet to pick up anything from gravity wave observatories.

This says nothing about the proximity of Dark Matter.

 

[disappoint]

This says nothing about the proximity of Dark Matter.

Well if dark matter interacts with normal matter/energy gravitationally then why have the gravity wave observatories on Earth not observed any gravity waves as of yet here on Earth?

 

[SphinxnihpS]

Well if dark matter interacts with normal matter/energy gravitationally then why have the gravity wave observatories on Earth not observed any gravity waves as of yet here on Earth?

The Earth has mass. A few other things around here have mass. Is the gravitational wave detector picking up those? No. The reason why is because those things would not produce gravitational waves. Gravitational waves we can detect are produced by BIG BIG BIG things, like supernovas and binary stars in highly elliptical orbits. Huge masses of dark matter just floating around would not be detected. A tiny bit of the stuff floating around you would not be detected, and yes, that is possible, despite the fact that most of the observed dark matter in the universe seems to surround galaxies.

 

[disappoint]

The Earth has mass. A few other things around here have mass. Is the gravity wave detector picking up those?

It's designed to ignore terrestrial gravity waves or it would yield false positives.

 

[Lemon law]

As far as I am concerned, dark matter is merely a name for something we do not understand, rather anything that explains anything.

And much like the older phony concept of either being needed to transmit waves in a vacuum, some test may be devised to prove the stuff flat out does not exist.

 

[SphinxnihpS]

It's designed to ignore terrestrial gravity waves or it would yield false positives.

Read further down my post. You are absolutely wrong to quibble with me over the FACT that dark matter can and may exist in the same space you occupy.

 

[SphinxnihpS]

As far as I am concerned, dark matter is merely a name for something we do not understand, rather anything that explains anything.

And much like the older phony concept of either being needed to transmit waves in a vacuum, some test may be devised to prove the stuff flat out does not exist.

False. It was a name given to a predicted "something" to account for why galaxies were more massive than expected. Matter because it has mass, and dark because it has no reaction with any known electro-magnetic radiation. So we do understand it, just not fully (just like pretty much everything else).

False. A test has already been devised to prove that "something" exists. We just happen to call it matter because it interacts gravitationally with regular matter. We postulated it exists based on universal expansion rates. The test (proof) was rather an accident, but gravitational lensing proves beyond doubt that dark matter is there.

Unlike figuring out the Earth is not flat, the universe in not helio-centric, etc. any further discoveries regarding dark matter are almost certain not to negate anything we do know, just as removing all the air from space and finding out waves can propagate across empty space did not disprove that waves require either to travel. We simply call that either space-time now.

 

[disappoint]

False. A test has already been devised to prove that "something" exists. We just happen to call it matter because it interacts gravitationally with regular matter. We postulated it exists based on universal expansion rates. The test (proof) was rather an accident, but gravitational lensing proves beyond doubt that dark matter is there.

Gravitational lensing only proves that the universe is warped in that vicinity, not that the cause is some mysterious matter that can't be seen. It's possible there may be no matter there at all and that spacetime is just not always uniform in the absense of matter.

 

[disappoint]

Read further down my post. You are absolutely wrong to quibble with me over the FACT that dark matter can and may exist in the same space you occupy.

"Can" and "may" is very different from "does", so you're stating that it's a fact that is possible but not known to be so. Eerily similar to my post where I said it was unlikely to be so, not impossible. Are you saying it is likely to be in the same space you occupy?

 

[beginner99]

As far as I am concerned, dark matter is merely a name for something we do not understand, rather anything that explains anything.

partially agree. It's just an invention for something we do not know what it is and if it exists but it is required to exist else alot of the current physics would just be wrong.

One though I had, how can you know the mass of a black hole? Could'nt black holes account fro this missing mass? maybe it's a stupid idea, not an expert but seems reasonable with my basic knowledge.
I mean you can estimate weight of stars and galaxies by their size (=everything mostly hydrogen).

 

[Pheran]

As far as I am concerned, dark matter is merely a name for something we do not understand, rather anything that explains anything.

And much like the older phony concept of either being needed to transmit waves in a vacuum, some test may be devised to prove the stuff flat out does not exist.

I'm with Lemon law on this one. As far as I'm concerned dark matter/energy are inventions to compensate for the fact that we still have an insufficient understanding of the physical laws involved (rather like the goofy "celestial spheres" that attempted to explain planetary motion in the geocentric solar system model).

 

[eddyg17]

I do not know about dark energy, but I have watched enough "The Universe" shows in the History Channel to kinda know what "dark matter" refers to.

From what we can observe through our various kinds of telescopes and instruments, the universe is missing most of its mass. This is a big no-no for all physicists. They have also noted that there is some places in the universe where space is curved as if a star or a planet was present.

So, there are two options.

a) There is something there that we cant yet observe.

b) Space time is not continuous and we still cant account for the missing mass.

Option a is the most logical solution, and the name dark matter came about. Think of this like the periodic table of elements, those elements at the end with weird Latin names.

 

[SphinxnihpS]

"Can" and "may" is very different from "does", so you're stating that it's a fact that is possible but not known to be so. Eerily similar to my post where I said it was unlikely to be so, not impossible. Are you saying it is likely to be in the same space you occupy?

You said, "I agree with everything you said, except the bolded part." The bolded part of what you quoted me saying was, "There may be some dark matter in or around you right now." Essentially you said, 'I disagree; it is not possible for dark matter to be in or around you right now.'

Backtrack all you want. That is what you said at the time. I have shown this to be false.

Gravitational lensing only proves that the universe is warped in that vicinity, not that the cause is some mysterious matter that can't be seen. It's possible there may be no matter there at all and that spacetime is just not always uniform in the absense of matter.

You seem to be having trouble getting over the convention, because you keep coming back to this point.

The only things we know that warps spacetime is mass/energy. That's why we call it dark matter. It's dark because we can't see it, and matter because it otherwise acts as such (warps spacetime).

 

[alyarb]

it violates conservation of energy to state that spacetime has its own gravitational topography in the absence of matter.

 

[SphinxnihpS]

I'm with Lemon law on this one. As far as I'm concerned dark matter/energy are inventions to compensate for the fact that we still have an insufficient understanding of the physical laws involved (rather like the goofy "celestial spheres" that attempted to explain planetary motion in the geocentric solar system model).

Yep. Just like everything in sub-atomic physics. But we keep building on our knowledge, and at this point, very little is ever shown to be flat out wrong. We may understand more about the stuff we call dark matter some day, but probably little if anything we think we know about it today will be proven false.

 

[GaryJohnson]

Gravitational lensing only proves that the universe is warped in that vicinity, not that the cause is some mysterious matter that can't be seen. It's possible there may be no matter there at all and that spacetime is just not always uniform in the absense of matter.

A good definition of Dark Matter might be: the cause of the non uniformity of space-time in the absence of normal matter. Wiki says that "dark matter is matter", but if it doesn't have anything in common with normal matter other than gravity then it really isn't matter is it?

It's a bit like calling a "circle" a "rounded cube" - a circle isn't a cube.

 

[silverpig]

1. OP: No, dark matter does not interact with EM radiation. Also, dark energy has an (apparently) constant density throughout the universe, while dark matter clumps up gravitationally.

2. Gravitational wave observatories like LIGO won't detect dark matter. They look for strong waves from supernovae and the rapidly orbiting binary systems like SphinxnihpS says.

3. Dark matter isn't just made up BS. It can be measured. We know it's location, the total mass, its effects, just not what it is. We don't fully understand all of the inner workings of the sun, but we know it's gonna rise in the morning, that it's hot, and that it gives us light.

4. You can measure the mass of a black hole using kinematics. This is how they measure the mass of stars and planets too, not by knowing their size.

5. Gravitational wave detectors don't pick anything up right now because they have to be extremely sensitive. They measure contractions of the length of the arms of the apparatus, something which can change by many more orders of magnitude by background vibrations.

6. Yes, there most likely is dark matter in and around your body right now. It is fairly smoothly distributed within galaxies. As we are in a galaxy, we are traveling through the Milky Way's dark matter halo as we speak.

 

[silverpig]

A good definition of Dark Matter might be: the cause of the non uniformity of space-time in the absence of normal matter. Wiki says that "dark matter is matter", but if it doesn't have anything in common with normal matter other than gravity then it really isn't matter is it?

It's a bit like calling a "circle" a "rounded cube" - a circle isn't a cube.

Neutrinos are matter and interact very much like dark matter does. The two are not so dissimilar.

 

[SphinxnihpS]

partially agree. It's just an invention for something we do not know what it is and if it exists but it is required to exist else alot of the current physics would just be wrong.

One though I had, how can you know the mass of a black hole? Could'nt black holes account fro this missing mass? maybe it's a stupid idea, not an expert but seems reasonable with my basic knowledge.
I mean you can estimate weight of stars and galaxies by their size (=everything mostly hydrogen).

We only know the size, mass, and distance of anything beyond our solar system through indirect and VERY IMPRECISE means. Black hole masses are estimated through their interactions with other objects, the size of the galaxy surrounding them, and relativistic jets. We have positively located only one type of black hole, the super massive black hole. We have never positively detected a solar black hole, but we do have candidates that are highly likely black holes. We will never directly observe a black hole, as they do not emit radiation (Someone say Hawking, I dare you!).

PS We don't estimate the mass of a star by its size. We estimate the size of a star by its mass and color. We estimate its distance by red shift, and we estimate its mass by comparison. We have math on our side, so we know things like the upper and lower bound for mass, but everything in between is very imprecise and reliant on other imprecise estimates. Those gee neato videos and slide shows you see showing how this star in bigger than this other one and so forth are largely conjecture.

Even though we don't know much, we do know that the mass missing from the universe could never be accounted for with black holes. We have close enough estimates for this.

 

[SphinxnihpS]

Neutrinos are matter and interact very much like dark matter does. The two are not so dissimilar.

The current theory is that dark matter is most likely very similar indeed; unknown massive nuclei particles. Most of the mass of what we term the normal matter of the universe is nutrinos anyway. We don't know much about them either, but they are normal.

 

[silverpig]

We only know the size, mass, and distance of anything beyond our solar system through indirect and VERY IMPRECISE means. Black hole masses are estimated through their interactions with other objects, the size of the galaxy surrounding them, and relativistic jets. We have positively located only one type of black hole, the super massive black hole. We have never positively detected a solar black hole, but we do have candidates that are highly likely black holes. We will never directly observe a black hole, as they do not emit radiation (Someone say Hawking, I dare you!).

PS We don't estimate the mass of a star by its size. We estimate the size of a star by its mass and color. We estimate its distance by red shift, and we estimate its mass by comparison. We have math on our side, so we know things like the upper and lower bound for mass, but everything in between is very imprecise and reliant on other imprecise estimates. Those gee neato videos and slide shows you see showing how this star in bigger than this other one and so forth are largely conjecture.

Even though we don't know much, we do know that the mass missing from the universe could never be accounted for with black holes. We have close enough estimates for this.

There are quite a few stars whose distance is measured quite accurately by parallax but those are the few hundred nearest stars. Beyond that accuracy does go down, but the bounds aren't so bad.