I Can dark matter explain dark energy?

[quantrex64]

Why do we need the theory of dark energy?
I know the it is claimed that dark-matter has no affect on the electromagnetic spectrum. How do we know the affects attributed to dark-energy aren't affects caused by dark-matter?
Dark-energy is claimed to be causing the universe to expand at an accelerated rate. The larger the distance between a light source and the observer larger the red shift.
This could also be a cause of dark-matter. If dark-matter causes a light spectrum shift. The farther a light source is away from the observer the more dark-matter that light would have to travel through. This could cause the appearance of a accelerating expanding universe.
Am I missing something? Have there been any studies to confirm or disprove this?

 

[PeterDonis]

I know the it is claimed that dark-matter has no affect on the electromagnetic spectrum.

No, that's not what is claimed. What is claimed is that dark matter does not emit or absorb electromagnetic radiation. But dark matter still acts as a source of gravity, which can affect electromagnetic radiation by causing redshifts, lensing, etc., just as ordinary matter does.

Dark-energy is claimed to be causing the universe to expand at an accelerated rate. The larger the distance between a light source and the observer larger the red shift.

No, that's not what "accelerated expansion" means. Any kind of expansion will cause this.

Accelerated expansion means a particular pattern of how the redshift varies with the distance to the light source; this pattern is the opposite of the pattern that would be caused by any kind of ordinary matter or dark matter. Only dark energy can cause this pattern. That's why dark energy is part of cosmologists' best current model of the universe.

(Note, btw, that I corrected "accelerated" in the OP--it was originally a different, and not appropriate, word.)

 

[Drakkith]

Am I missing something? Have there been any studies to confirm or disprove this?

There have been many, many studies on both dark matter and dark energy and none of these studies have shown that the two have any connection to each other. In fact, studies show that dark matter has the opposite effect on expansion that dark energy does. Dark matter, along with regular matter, acts to slow the expansion and would reverse it entirely if the density was high enough.

 

[quantrex64]

How can we be sure of dark matters affects on light when we are not even sure of what it is. I'm not saying dark matter is causing the universe to expand but its affects on light may be causing that appearance.
I know dark matter has an affect on light through gravity. That is still not a direct affect.
If there is no other way to measure they expansion but through red shift. How can it be ruled out?

 

[PeterDonis]

How can we be sure of dark matters affects on light when we are not even sure of what it is.

Because we know enough about it to know its effect on light--which is just what I described in my previous post.

Actually, even that somewhat misstates it. The term "dark matter" is defined as "stuff that doesn't participate in any other interactions except gravity, but acts just like ordinary matter as a source of gravity". And that, all by itself, is enough to know how "dark matter" affects light.

I'm not saying dark matter is causing the universe to expand but its affects on light may be causing that appearance.

Neither dark matter, nor dark energy, nor ordinary matter or energy causes the universe "to expand". The universe is expanding because it started out expanding in the Big Bang.

The issue, as I've already said, is accelerated expansion, and we already know that nothing that acts like ordinary matter as a source of gravity can cause accelerated expansion.

Also, as I've already noted, it's impossible for dark matter, or ordinary matter, or anything else except dark energy, to cause the appearance of accelerated expansion. See further comments below.

If there is no other way to measure they expansion but through red shift.

The data that tells us that the universe is expanding, and that that expansion is accelerating, is not just redshift data. There are three main pieces of data that we get from the distant objects we observe: their redshift, their apparent brightness, and their angular size. The last two are used to estimate the distance to the object. Different models of the universe predict different relationships between these quantities, so it's the relationships between them in the actual data that tell us which model is right. The model that best matches the relationships we actually observe is, as I've said, the model with accelerating expansion (more precisely, with accelerating expansion since a few billion years ago, and decelerating expansion before that), and dark energy is required to explain the accelerated expansion.

 

[quantrex64]

Thank you for that explanation. There is one other explanation for the elimination of dark energy.
It is beginning to look like this is a flat universe which stretches into infinity. If this turns out to be true we maybe just in a part of the universe which is expanding. Waves of matter with troughs and peaks. Expanding into to parts which are contracting.
Even with the background microwave radiation we can only see out so far. There maybe a contracting wave moving towards us and we wouldn't know it. Granted it wouldn't be a worry for us even if we seen it coming tomorrow.
I know astrophysicists don't like the idea of infinity to explain things. It is kind of a cop out. I understand that never the less a possibility.

 

[PeterDonis]

There is one other explanation for the elimination of dark energy.

At this point you are just speculating (and your speculation appears very uninformed; you really should take some time to learn the details of what our current best cosmological model actually says). PF rules prohibit personal speculations.

I know astrophysicists don't like the idea of infinity to explain things.

I don't know where you are getting that from. Our current best cosmological model says the universe is spatially flat and spatially infinite.

Thread closed.