Dark Energy and Dark Matter the same thing?

[babea]

Dr. HongSheng Zhao at the University of St. Andrews School of Physics and Astronomy has developed a model that shows how dark energy and dark matter are more closely linked than previously thought.

Dr Zhao points out, "Both dark matter and dark energy could be two faces of the same coin. "As astronomers gain understanding of the subtle effects of dark energy in galaxies in the future, we will solve the mystery of astronomical dark matter at the same time."

Just a quick explainer. Dark energy was discovered in the late 1990s during a survey of distant supernova. Instead of finding evidence that the mutual gravity of all the objects in the Universe is slowing down its expansion, researchers discovered that its expansion is actually accellerating.

Dark matter was first theorized back in 1933 by Swiss astronomer Fritz Zwicky. He noted that galaxies shouldn't be able to hold themselves together with just the regular matter we can see. There must be some additional, invisible matter surrounding the regular matter that provides the additional gravitational force to hold everything together.

And since their discoveries plenty of additional evidence for both dark energy and dark matter have been seen across the Universe.

In Dr. Zhao's model, dark energy and dark matter the same thing that he calls a "dark fluid".

Incredulous...

Babea q-_-p

 

[Gravity_Ray]

That's rather confusing eh?

If one is repelling, and one is attracting how can they be "the same thing"?

I could live with "two faces of the same coin", but the same thing?

 

[ramparts]

Y'all would be surprised, very crazy speculative but somewhat plausible theories come out all the time. This isn't an aberration or anything very special - until there's some serious evidence in its favor

 

[babea]

IMHO, logically, the reality is that they could be working with each other (in tandem) as DE provides a push and DM provides a pull through gravitational forces.

 

[ramparts]

They act in very different ways and play very different roles. They're similar only insofar as they've both been discovered in the last few decades and as we don't know what they are. They may be related but I think it's more likely they're not - there's no really compelling reason to think that they are.

 

[csmyth3025]

I suppose one could define electrostatic attraction and electrostatic repulsion as "two faces of the same coin".

We observe the effects of "dark matter" acting over distances of tens or hundreds of thousands light years. It acts as if it's a gravitational (attractive) force.

Likewise, we observe the effects of "dark energy" acting over distances of millions or billions of light years. It acts as if it's some kind of (repulsive) force causing space to expand.

In both cases we have no evidence of these effects locally - such as the orbit of our moon or the motion of our planets. We can't measure or duplicate these effects in our laboratories.

I imagine an ancient scientific investigator observing at a great distance two sets of charged metal spheres suspended on strings - one set "pulling away" from each other and one set "pulling towards" each other. I wonder if he would conclude that these two opposite effects must surely be caused by entirely separate mechanisms (forces).

But today we know that this effect is, indeed, both "two faces of the same coin" and, fundamentally, also "the same thing".

Chris

That's rather confusing eh?

If one is repelling, and one is attracting how can they be "the same thing"?

I could live with "two faces of the same coin", but the same thing?

 

[Floridian]

More or less yes, both are made up with no direct evidence, also e=mc(squared)

 

[Floridian]

IMHO, logically, the reality is that they could be working with each other (in tandem) as DE provides a push and DM provides a pull through gravitational forces.

True, but also, invisible unicorns could be reacting against invisible space-llamas.

Also, we could easily make a permanent settlement on Mars.

In fact, Mars is almost as great a natural resource as Earth. For a space-faring civilization Mars might even be a better base of operations in some respects.

A space elevator could extend from Olympus Mons. With 2.4 times less gravity than Earth, this would facilitate space-industrial operations and the construction of deep-space spacecraft that would never need to enter a planets atmosphere. Also Mars is in close proximity to the asteroid belt which is full of water and materials. (I think it has water, not 100% sure). Also Titan has huggggeeeee amounts of natural gas. It is basically a giant sea of liquid natural gas (ok that looks ********).

Mars could be terraformed within 100 years to make it somewhat livable. If we were to use certain green-house gases, melt the ice-caps on Mars, etc. you would start a snowball effect where as the temperature increased more of the (hopefully) frozen ice on mars melted and created an atmosphere. Settlements could be made underground in Mars perhaps vast caverns/aquafers.

Future projects on Mars would be reactivating plate-tectonics, importing water, and increasing the planets spin.

But in the short term, though Mars has far to little atmospheric pressure and gravity to make it super comfortable, humans could survive with just an oxygen mask if atmospheric pressure were increased to something along the lines of 1/3rd Earths.

Within 1000 years Mars could theoretically grow large forests.

Mars is within the habitual zone where liquid water can exist. Though it only gets 40% the sunlight of Earth, this can be supplement with the greenhouse effect.

 

[MeteorWayne]

Floridian, Please stick to the topic. It is not Mars, it is Dark Energy and Dark Matter. There are plenty of other discussions about Mars in Space Business and Technology.

thanx

Moderator Meteor Wayne

 

[Woggles]

Hi Everyone

I was watching the Oasis channel last night. The program was Hubble Canvas. Sorry they do not list by episodes. The program was talking about Dark Matter and Dark Energy. Apparently Hubble was points to one of the darkest area of the universe to observe the galaxies. They were using gravitational lensing, to observe these far off galaxies. What I gather from the show is that they had detected the present of Dark Matter. Using calculations of the weak gravitation lensing effect, they determine the effect of gravity from the observable matter was not of sufficient amount to cause the effect of the lensing. Though calculations they were able to map dark matter. They show a 3d model of the dark matter found in the area observed. Which was pretty cool!!.
Next, Hubble was to focus on looking for supernovas in the early galaxies, to determine the age of the universe. Once I think 5 were found, the scientist determine the expansion was increasing even when calculating the amount of dark matter. As they said something else was affecting the expansion which we know is called dark energy. What I found interesting was that they said dark energy is believed to intertwine with the fabric of space-time itself! I didn’t know this so I thought I share.

I was able to find a newpaper article on the subject. http://www.msnbc.msn.com/id/35085736/ns ... nce-space/

And the 3d map

http://www.msnbc.msn.com/id/16515562/ns ... nce-space/


Paul

 

[Kaymen]

Dark Energy and Dark Matter

I think we already know what this so called "dark energy" is, but just have not recognized it: radiation pressure. Light exerts a small but cumulative force upon anything it interacts with. Think radiometer or solar sail. Therefore, the light from all the galaxies interacting with the light from all these other galaxies would be constantly pushing them apart. On more local scales, gravity would be able to overcome this force and allow them to be drawn together into the local clusters. Figure in the radiation pressure and throw the term "dark energy" into the trash.

"Dark matter" could be nothing more than photons of light or some other radiation in the state of equilibrium between gravity and radiation pressure. Photons of light are affected by gravity in instances of gravitational lensing which would indicate that they have some small amount of mass. Add up all this mass and get rid of the term "dark matter".

Keep in mind that I have no professional background in any of this, just my interpretation of the data thus far. Please feel free to inform me better.

 

[csmyth3025]

Re: Dark Energy and Dark Matter

I think we already know what this so called "dark energy" is, but just have not recognized it: radiation pressure. Light exerts a small but cumulative force upon anything it interacts with. Think radiometer or solar sail. Therefore, the light from all the galaxies interacting with the light from all these other galaxies would be constantly pushing them apart. On more local scales, gravity would be able to overcome this force and allow them to be drawn together into the local clusters. Figure in the radiation pressure and throw the term "dark energy" into the trash.

"Dark matter" could be nothing more than photons of light or some other radiation in the state of equilibrium between gravity and radiation pressure. Photons of light are affected by gravity in instances of gravitational lensing which would indicate that they have some small amount of mass. Add up all this mass and get rid of the term "dark matter".

Keep in mind that I have no professional background in any of this, just my interpretation of the data thus far. Please feel free to inform me better.

I'm also a layman in regard to matters of science, so I'll rely heavily on Wikipedia to try to respond to your post:

Part of the reason that cosmologists entertain the idea of "dark energy" has to do with the "flatness problem" in cosmology. Wikipedia's article on dark energy contains this paragraph:

"...The existence of dark energy, in whatever form, is needed to reconcile the measured geometry of space with the total amount of matter in the universe. Measurements of cosmic microwave background (CMB) anisotropies, most recently by the WMAP spacecraft, indicate that the universe is very close to flat. For the shape of the universe to be flat, the mass/energy density of the universe must be equal to a certain critical density. The total amount of matter in the universe (including baryons and dark matter), as measured by the CMB, accounts for only about 30% of the critical density. This implies the existence of an additional form of energy to account for the remaining 70%.[7] The most recent WMAP observations are consistent with a universe made up of 74% dark energy, 22% dark matter, and 4% ordinary matter.[2]..."

Although this paragraph doesn't specifically say so, I believe that cosmologists have taken into account the amount of observable energy that the universe is believed to contain.

Photons of light are affected by gravity in instances of gravitational lensing which would indicate that they have some small amount of mass. Add up all this mass and get rid of the term "dark matter".

Again, Wikipedia addresses this notion in their article on mass-energy equivalence:

"...Note further that in accordance with Einstein’s Strong Equivalence Principle (SEP), all forms of mass and energy produce a gravitational field in the same way.[9] So all radiated and transmitted energy retains its mass. Not only does the matter comprising Earth create gravity, but the gravitational field itself has mass, and that mass contributes to the field too. This effect is accounted for in ultra-precise laser ranging to the Moon as the Earth orbits the Sun when testing Einstein’s general theory of relativity.[9]..."

and:

"..In relativity, all energy moving along with a body adds up to the total energy, which is exactly proportional to the relativistic mass. Even a single photon, graviton, or neutrino traveling in empty space has a relativistic mass, which is its energy divided by c². But the rest mass of a photon is slightly subtler to define in terms of physical measurements, because a photon is always moving at the speed of light—it is never at rest.

If you run away from a photon in the direction it travels, having it chase you, when the photon catches up to you the photon will be seen as having less energy. The faster you were traveling when it catches you, the less energy it will have. As you approach the speed of light, the photon looks redder and redder, by Doppler shift (the Doppler shift is the relativistic formula), and the energy of a very long-wavelength photon approaches zero. This is why a photon is massless; this means that the rest mass of a photon is zero....."

Based on these two portions of the article, I'm pretty sure that cosmologists have already taken into account the gravitational mass-equivalence of the observable energy in galaxies and galaxy clusters.

I believe that your ideas about radiation pressure and the gravitational effect of energy are essentially correct. I'm also confident that these effects have been recognized for many years and that their contributions to the "missing mass" observed on the scale of galaxies and galaxy clusters and the "missing energy" attributed to the flatness and accelerating expansion of the universe have been considered in the calcuations by which the proposed amounts of dark matter and dark energy have been estimated.

Chris