How does Dark Matter and Dark Energy work?

• 15 Replies
• 10816 Views

0 Members and 1 Guest are viewing this topic.

neone

• First timers
• 4
How does Dark Matter and Dark Energy work?
« on: 28/03/2015 07:35:33 »

I recently found this forum and I'm in serious need of debunking some recent brainstorms around dark matter, dark energy and the expansion of the universe.
Just to mention I'm not a scientist, just some wanderer through this very fascinating field at the moment.

If I'm not mistaken there is this strange relationship between dark matter and ordinary matter (through gravity?). Is this correct?
There is also this tension between dark matter and dark energy, one holding things together and the other trying to rip things apart. Hence the big rip and big crunch theory?
Has anyone more info of the evolution in time of those two forces? Does this maybe have anything to do with the m-theory?
In one of my brainstorms I was thinking of the big bang as 100% energy, that gradually evolved into 0 energy and towards 100% dark energy, towards a big rip, one of the scenarios.
Another one of my brainstorms, a bit more off I admit, was wandering around the evolution of  ordinary energy and matter towards dark matter and dark energy. I even tend to call it an other dimension, perhaps quantifiable in a way for the first time - not directly but more in relation towards matter and energy? Again I saw in a way the evolution of 100% energy towards more dark matter and energy.

Another more visual approach/brainstorm is the representation of the behavior of the force field of atoms, compared to another visual image, the expansion of the universe. I experience some trouble letting this one go, although this is probably comparing an apple with a pear to say the least.

(ps this is just a brainstorm, please don't take this too seriously  [])

Edit: Changed the title to a question.
« Last Edit: 28/03/2015 21:48:07 by evan_au »

~CB

• Guest
Re: in need of some debunking ;-)
« Reply #1 on: 28/03/2015 08:20:23 »
Hello, welcome to the forum! Being a new member myself to this forum as well as the world of physics... I believe I'm not qualified enough to answer your question yet. But, don't worry, within 24 hours you'll find brilliant minds of this forum answering it for you. They always do! But, till then I have this webpage ('https://www.learner.org/courses/physics/unit/text.html?unit=10&secNum=0')[Apologies! I gave you the wrong url before. I gave you the one for dark energy instead of dark matter.] that might answer it for you, if not, it'll at-least give you some pretty top notch knowledge.
« Last Edit: 28/03/2015 08:32:40 by Jasper Hayden »

neone

• First timers
• 4
Re: in need of some debunking ;-)
« Reply #2 on: 28/03/2015 08:58:09 »
Thanks Jasper,

I'm new to this too and I have to say it's a very fascinating field raising more questions then answers.
Realizing we might only know around 5% of the universe really triggered a massive amount of questions, some of these questions I hope will be debunked trough this forum.

My apologies if some questions are perhaps ridiculous, again, I'm not a scientist myself, it's my curiosity that drove me here  []

~CB

• Guest
Re: in need of some debunking ;-)
« Reply #3 on: 28/03/2015 09:51:53 »
No worries! And yes, I know what you are talking about... These fields, physics and cosmology really are fascinating. I have nothing against chemistry or biology and these are all related to each other one way or another. But, I never found myself hovering about on the chemistry or biology forum branches or just study branches to be general. They just don't spark that passionate curiosity in me; Now I don't mean any disrespect... Your questions might be foolish but who Am I to judge?; And yes, I agree with on 'You are certain to stack up more questions than answers whilst studying this field', It's this reason that got me to study this field. I sometimes scratch my head for hours thinking about the universe although it was only a month ago that I found this man saying 'Learning, instead of thinking over trivia would make you wiser'. Only then I learnt I was just wasting all that time going nowhere with the question that I know aren't going to be answered soon. My main objective, when I started learning physics and philosophy was to understand my purpose here or atleast contribute in some breakthrough invention/theory. But now, it's more curiosity and fascination that keeps me going; I sometimes wish that humans would start thinking in an intelligent manner rather than just doing all that useless and unproductive things they do all the time. Most of us are just giving birth to feeble minded who do nothing but waste resources. Call me pathetic but I really hate people who don't intellectually contribute and yet just live and die taking share in the resources. But then there's times when I'm not hating them as much, that's when I'm thinking that we actually know nothing of universe. Their could be a mechanism for restoring resources or energy somewhere in the space which we might soon hit upon. Their are endless possibilities, what we can do is just guess and invent. I have already given up on finding our purpose... What I feel is, we are just these animals with consciousness in some game, and the game maker is just having fun killing us or watching us do stupid stuff... That we will live and die, forgotten and this will go on while that game maker just plays us. I mean there are lots of galaxies... So I have this thought that each galaxy is controlled by one gamer and he is just developing us. Oh well, like I said... There are endless possibilities, why should I waste my time guessing.
I'm glad we talked, I really had to get it all out.

~CB

• Guest
Re: in need of some debunking ;-)
« Reply #4 on: 28/03/2015 09:57:49 »
By the way, did the webpage partially or completely answered the question(s) you had?

neone

• First timers
• 4
Re: in need of some debunking ;-)
« Reply #5 on: 28/03/2015 12:09:55 »
Hey Jasper,

I think I know what you are talking about. Please correct me if I'm wrong.
I'm more into visual arts and just brainstorming for a bit trough this. Nothing more, just out of curiosity and fascination with growing respect towards science in a way, even seeing some similarities between a scientist and an artist or designer.

At the end of every day Socrates wins knowing to know nothing. And trough every docu I see or book I read trying to understand things a bit more raises more questions then answers. Pretty amazing really in a way. the webpage you entered confirmed one thing: this evolution towards more questions then answers :-)

I also think I know what you mean with your wish at times. For instance when you think about climate change you would expect people to be more careful with the CO2 they spread out, taking more care towards the environment etc. Digging into science even for just a little bit only strengthens this feeling.
But realizing we know nothing calms me down too in a way. Every brainstorm of mine ends up with more fascination.

Like you said, maybe there is a mechanism for restoring resources or energy somewhere in the space which we might soon hit upon, who knows ...

PmbPhy

• Neilep Level Member
• 2784
Re: How does Dark Matter and Dark Energy work?
« Reply #6 on: 29/03/2015 04:48:54 »
Dark energy works by acting gravitationally as if it was gravitationally repulsive. This can be accomplished by either the use of negative pressure or a positive gravitational constant.

Dark matter is just another name for matter which can't be seen, i.e. it doesn't interact by the electromagnetic interaction (i.e. by light). We know of its existence by its gravitational properties. We observe this from a detailed study of the light coming from galaxies. We measure the light from different parts of the galaxies and by the redshift and blueshift of light we can determine the speed of the matter which is illuminated. From this we get what is called a rotation curve. It was discovered that the rotation curves cannot be explained by the matter which can be seen and it was deduced that there must be matter which was dark. It was also suggested that Newton's laws were flawed but that was studied and rejected for good reasons.

PhysBang

• Hero Member
• 590
Re: How does Dark Matter and Dark Energy work?
« Reply #7 on: 29/03/2015 15:22:42 »
To be clear, "dark energy" was named this because the term "dark matter" was already a popular term. Nobody has established that there is a connection between the two other than that they are both factors in dynamics at the cosmological scale.

PmbPhy

• Neilep Level Member
• 2784
Re: How does Dark Matter and Dark Energy work?
« Reply #8 on: 29/03/2015 16:23:59 »
To be clear, "dark energy" was named this because the term "dark matter" was already a popular term. Nobody has established that there is a connection between the two other than that they are both factors in dynamics at the cosmological scale.
It is assumed that dark matter acts gravitationally the same as normal matter. We just can't detect it in any part of the EM spectrum. Dark energy, on the other hand, is not matter in the normal sense and shouldn't be thought of as such. Another name for dark energy is in fact quintessence or cosmological constant. Which name it takes depends on the mechanism it turns out to be caused by.

http://en.wikipedia.org/wiki/Dark_energy

acsinuk

• Sr. Member
• 237
Re: How does Dark Matter and Dark Energy work?
« Reply #9 on: 29/03/2015 18:51:11 »
What about the electrical forces in space?? Dark energy is making the universe expand, the opposite effect to gravity. If the stars were electrically repelling each other with a force of 23 times than that of gravity then we have the correct balance and we don't have to imagine anything
A.C.Stevens

PmbPhy

• Neilep Level Member
• 2784
Re: How does Dark Matter and Dark Energy work?
« Reply #10 on: 29/03/2015 19:00:49 »
Quote from: acsinuk
What about the electrical forces in space??
What about them? We see no evidence of this in nature. All of our observations tell us that everything in the universe is electrically neutral.

Quote from: acsinuk
Dark energy is making the universe expand, the opposite effect to gravity. If the stars were electrically repelling each other with a force of 23 times than that of gravity then we have the correct balance and we don't have to imagine anything
Sure you do. You have to imagine a great deal in fact. In the first place you're confused about what's accelerating apart. You seem to think that its the stars which are accelerating away from all the other stars. That is NOT the case. It's the galaxies that are accelerating apart. The galaxy nearest to us is 50 kpc away and would take light over 150,000 years to get here from there. If the charge on that galaxy was so large to have an effect on this one then that galaxy would have disintegrated before it gravitationally collapsed. Not to mention the same thing here. We detect no electric field here which means your hypothesis is wrong.

acsinuk

• Sr. Member
• 237
Re: How does Dark Matter and Dark Energy work?
« Reply #11 on: 30/03/2015 17:29:51 »
The evidence is the WMAP results and their explanation of an invisible force is just semantics I suppose, and I agree the galaxies are being pushed apart by an invisible force.  The only invisible force I know of that weighs nothing is electrical.

BTW have you looked at the magnet-flipper vortex experiment yet; which shows clearly that a magnetic field will spin ions.  If this happens on a galactic scale then we have the answer as to their bar spiral forms and note the magnetic hub at the central [black hole] of galaxy will; for a minimum angular momentum requirement need to control the position of the stars so that they do no interfere with each others orbits which I think would answer your second point.
A.C.Stevens

neone

• First timers
• 4
Re: How does Dark Matter and Dark Energy work?
« Reply #12 on: 01/04/2015 15:21:13 »
thanks for the feedback all.
much appreciated!

PmbPhy

• Neilep Level Member
• 2784
Re: How does Dark Matter and Dark Energy work?
« Reply #13 on: 01/04/2015 16:20:48 »
From Gravitation and Spacetime - Third Edition by Hans C. Ohanian and Remo Ruffini, page 389
Quote
We will see that the expansion of the universe today is dominated by this cosmological term, also called "dark energy."

I.e cosmological term, also called "dark energy" clear as a bell!

Personally, if it was me, I'd call the source of the cosmological constant "dark energy." However that is what the authors wrote and that is what it means when its said that "sometimes the cosmological constant itself is called dark energy" (or something like that)

The reason the cosmological constant itself is called "dark energy" is because in the absence of matter it behaves like a non-zero energy density. I.e. as usual, let the cosmological constant be $$\Lambda$$

$$T^{\mu\nu}_{vac} = \frac{\Lambda c^2}{8\pi G}$$

Also when, Tuv = 0, the linearized Einstein field equations for a static Newtonian potential $$\Phi$$ yields

$$\nabla^2 \Phi = -\Lambda$$

Compared with Newton's equation

$$\nabla^2 \Phi = -\Lambda$$

The cosmological term then corresponds to a uniform effective mass density of

$$\rho_{eff} = -\frac{\Lambda}{4\pi G}$$

Which means the potential evolves as if the mass density is negative and thus the gravitational repulsion.
« Last Edit: 02/04/2015 15:36:05 by PmbPhy »

PhysBang

• Hero Member
• 590
Re: How does Dark Matter and Dark Energy work?
« Reply #14 on: 02/04/2015 14:41:00 »
I'll just stand by my claim that the names for different hypotheses about the origin of an effect are not simply different names for the effect.

I hope that isn't too controversial for the mods here.

The cosmological constant, proper, is a constant of the equation that links spacetime geometry to mass-energy density. One can put this constant on the geometry side of the equation or the mass-energy side of the equation, or one can put two constants.

One can have an energy field that permeates the vacuum. One can have a a scalar field that permeates spacetime. One can have dark matter behave in some strange way that repulses other matter and energy at large scales (though I believe this has been ruled out).

All of these are "dark energy", in that they could be the source of the cosmological acceleration of expansion. Sometimes, people are sloppy and use the terms of these ideas or even the ideas themselves interchangeably. If we love in a particularly nasty universe, there might be more than one type of dark energy at work at the same time.

yor_on

• Naked Science Forum GOD!
• 12188
• (Ah, yes:) *a table is always good to hide under*
Re: How does Dark Matter and Dark Energy work?
« Reply #15 on: 05/04/2015 22:15:32 »
Heh
Liked that sentence Physbang, not sure if it was a intended pun, but it came out quite nicely any which way.
"BOMB DISPOSAL EXPERT. If you see me running, try to keep up."