APOD: Dark Matter in a Simulated Universe (2020 Oct 25)

[APOD Robot]

Dark Matter in a Simulated Universe

Explanation: Is our universe haunted? It might look that way on this dark matter map. The gravity of unseen dark matter is the leading explanation for why galaxies rotate so fast, why galaxies orbit clusters so fast, why gravitational lenses so strongly deflect light, and why visible matter is distributed as it is both in the local universe and on the cosmic microwave background. The featured image from the American Museum of Natural History's Hayden Planetarium previous Space Show Dark Universe highlights one example of how pervasive dark matter might haunt our universe. In this frame from a detailed computer simulation, complex filaments of dark matter, shown in black, are strewn about the universe like spider webs, while the relatively rare clumps of familiar baryonic matter are colored orange. These simulations are good statistical matches to astronomical observations. In what is perhaps a scarier turn of events, dark matter -- although quite strange and in an unknown form -- is no longer thought to be the strangest source of gravity in the universe. That honor now falls to dark energy, a more uniform source of repulsive gravity that seems to now dominate the expansion of the entire universe.

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[RocketRon]

If dark energy repels, is it likely to clump or string together, or be spread uniformly (and 'expandingly') throughout the universe ??

[RocketRon]

Or is dark energy merely a manifestation of time running 'backwards' which we are unable to quantify or observe. ?

[Ann]

It would be fun to see a simulation of the combined effects of dark matter and dark energy. Preferably as an animation!

Ann

[PolishBear]

Looks like neurons.

[orin stepanek]

You're going to think I'm nuts; but my opinion is that maybe dark matter is antimatter; and is combining with positive matter and is creating the universe! Instead of anilalating each other; are in fact attracting each other! That would also explain the exansion of the universe! Maybe I am nuts!

[Sa Ji Tario]

Let someone invert the colors and it will look like the neural network

[Chris Peterson]

DarkMatter_KipacAmnh_960.jpg


You're going to think I'm nuts; but my opinion is that maybe dark matter is antimatter; and is combining with positive matter and is creating the universe! Instead of anilalating each other; are in fact attracting each other! That would also explain the exansion of the universe! Maybe I am nuts! :mrgreen:

For a variety of reasons, dark matter as antimatter has been ruled out.

[Chris Peterson]

If dark energy repels, is it likely to clump or string together, or be spread uniformly (and 'expandingly') throughout the universe ??

Dark matter is "stuff", and as such it can clump or be otherwise non-uniform. As best as we know right now, dark energy is a property of spactime, and has no structure.

[richard schumacher]

Dark matter is "stuff", and as such it can clump or be otherwise non-uniform. As best as we know right now, dark energy is a property of spacetime, and has no structure.

Is dark energy necessarily a property of spacetime? If so then there would be no way to accumulate or concentrate it; it would always be uniformly distributed, except where spacetime itself is concentrated. (But then I would wonder what happens near the singularity inside a black hole, where there is a whole lotta spacetime goin' on.)

If it isn't an intrinsic property of spacetime, that would hold open the possibility that it could be accumulated or concentrated, somehow.

[Chris Peterson]

Dark matter is "stuff", and as such it can clump or be otherwise non-uniform. As best as we know right now, dark energy is a property of spacetime, and has no structure.

Is dark energy necessarily a property of spacetime? If so then there would be no way to accumulate or concentrate it; it would always be uniformly distributed, except where spacetime itself is concentrated. (But then I would wonder what happens near the singularity inside a black hole, where there is a whole lotta spacetime goin' on.)

If it isn't an intrinsic property of spacetime, that would hold open the possibility that it could be accumulated or concentrated, somehow.

There is a reason I qualified my comment with "as best as we know right now". We certainly don't know enough about dark energy to say with any certainty what is or is not possible. Only that the evidence we currently have best suggests it as a property of spacetime, and as such not something that could accumulate or have a non-uniform density.

[orin stepanek]

Thanks Chris! I know you are correct, and after reading your reply I found this;
https://www.differencebetween.com/diffe ... ntimatter/
I don't know much about it either!

[Ann]

M94, the galactic beauty with no dark matter? Photo: R Jay Gabany (Blackbird Obs.)

---

I just watched a video by Dr Becky, where she talked about galaxy M94. Maybe possibly maybe M94 lacks dark matter.

Ann

[ta152h0]

Want to explore my brain? just tell me what is the universe expanding into? pass the ice cold one

[Chris Peterson]

Want to explore my brain? just tell me what is the universe expanding into? pass the ice cold one

It isn't expanding into anything.

[Aethereal]

This dark matter theory seems quite artificial to me. Will it end the same way the old aether theory ended?

[Chris Peterson]

This dark matter theory seems quite artificial to me. Will it end the same way the old aether theory ended?

The existence of dark matter is evident through many independent lines of evidence. It is real, beyond reasonable doubt. What is uncertain is its nature. Most likely an elementary particle of some kind, but that leaves several possibilities (although the range of possibilities continues to narrow with new experiments and observations).

[Aethereal]

Thank you Chriss, I thought that the only evidence of the existence of dark matter were its gravitational effects. Was I wrong?

[Chris Peterson]

Thank you Chriss, I thought that the only evidence of the existence of dark matter were its gravitational effects. Was I wrong?

Not entirely. Almost all of the observational evidence for dark matter is related to its gravitational effects. But those observations are of very different things- galaxy rotation curves, the distribution of matter in galaxy clusters, gravitational lensing, and others. But there is also a lot of theoretical support- the anisotropy of the CMB, the density requirements for our best Big Bang theory, galaxy formation processes, and others.

All of these things demonstrate beyond reasonable doubt that dark matter exists, and in sum they largely rule out the only identified alternatives to it actually being matter of some kind, such as modifications to our understanding of gravity itself.

I don't think you'll find many cosmologists who entertain much doubt that dark matter is made up of some kind of non-baryonic particles.