APOD: Sonified: The Matter of the Bullet... (2020 Dec 16)

[APOD Robot]

Sonified: The Matter of the Bullet Cluster

Explanation: What's the matter with the Bullet Cluster? This massive cluster of galaxies (1E 0657-558) creates gravitational lens distortions of background galaxies in a way that has been interpreted as strong evidence for the leading theory: that dark matter exists within. Different analyses, though, indicate that a less popular alternative -- modifying gravity-- could explain cluster dynamics without dark matter, and provide a more likely progenitor scenario as well. Currently, the two scientific hypotheses are competing to explain the observations: it's invisible matter versus amended gravity. The duel is dramatic as a clear Bullet-proof example of dark matter would shatter the simplicity of modified gravity theories. The featured sonified image is a Hubble/Chandra/Magellan composite with red depicting the X-rays emitted by hot gas, and blue depicting the suggested separated dark matter distribution. The sonification assigns low tones to dark matter, mid-range frequencies to visible light, and high tones to X-rays. The battle over the matter in the Bullet cluster is likely to continue as more observations, computer simulations, and analyses are completed.

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[jks]

Hi,

I think that there are two threads for today's entry (2020 Dec 16). Also, in today's very nice APOD, the "Discuss" link points to yesterday's thread.

jks

[orin stepanek]

O.K. first I heard of the Modified gravity theory! Interesting video!

[RJN]

Hi,

I think that there are two threads for today's entry (2020 Dec 16). Also, in today's very nice APOD, the "Discuss" link points to yesterday's thread.

jks

Yes, thank you, this linking problem has now been fixed. We apologize for the oversight.

[Chris Peterson]

O.K. first I heard of the Modified gravity theory! :?: Interesting video! 8-)

Not very much support for the MOND theories. They are very limited in where they work compared with dark matter. The latter explains all our observations, as well as fitting in with our best Big Bang theory. Really, the only problem with dark matter remains in answering the question of just what the heck it actually is!

[orin stepanek]

O.K. first I heard of the Modified gravity theory! Interesting video!

Not very much support for the MOND theories. They are very limited in where they work compared with dark matter. The latter explains all our observations, as well as fitting in with out best Big Bang theory. Really, the only problem with dark matter remains in answering the question of just what the heck it actually is!

Yes! I'll stick with the dark matter theory!

[De58te]

So the two contenders are invisible matter verses gravity as we've never seen before. Just wondering if anybody has suggested white holes interacting with pixie dust leaking out of hyperspace strings?

[johnnydeep]

So the two contenders are invisible matter verses gravity as we've never seen before. Just wondering if anybody has suggested white holes interacting with pixie dust leaking out of hyperspace strings?

You lost some credibility at "pixie dust"

[Chris Peterson]

So the two contenders are invisible matter verses gravity as we've never seen before. Just wondering if anybody has suggested white holes interacting with pixie dust leaking out of hyperspace strings?

The last I heard, that theory had been modified with the addition of unicorn farts.

[heehaw]

There is a THIRD contender - exotic topology. Exotic topology ONLY exists in four-dimensional spacetimes. Ever wonder why there are only 3 space dimensions? It would be so much easier to park cars if there were a fourth space dimension! https://henry.pha.jhu.edu/exotic.pdf

[neufer]

Click to play embedded YouTube video.

<<Scalar–tensor–vector gravity theory, also known as MOdified Gravity (MOG), is based on an action principle and postulates the existence of a vector field, while elevating the three constants of the theory to scalar fields. In the weak-field approximation, MOG produces a Yukawa-like modification of the gravitational force due to a point source. Intuitively, this result can be described as follows: far from a source gravity is stronger than the Newtonian prediction, but at shorter distances, it is counteracted by a repulsive fifth force due to the vector field.

MOG has been used successfully to explain galaxy rotation curves, the mass profiles of galaxy clusters, gravitational lensing in the Bullet Cluster, and cosmological observations without the need for dark matter. On a smaller scale, in the Solar System, STVG predicts no observable deviation from general relativity. The theory may also offer an explanation for the origin of inertia.>>

[sym666]

Better than most of the music you can hear nowadays.

[bystander]

So the two contenders are invisible matter verses gravity as we've never seen before. Just wondering if anybody has suggested white holes interacting with pixie dust leaking out of hyperspace strings?

You lost some credibility at "pixie dust"

The last I heard, that theory had been modified with the addition of unicorn farts.

Doesn't matter!