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As someone who can appreciate physics, but doesn't really know much: What are the implications of this?

by jotato 10y ago

JoeAltmaier 10y ago
"Nothing in the standard cosmological model predicts this, and it is almost impossible to imagine how that model could be modified to explain it, without discarding the dark matter hypothesis completely." Read more at: http://phys.org/news/2016-09-spiral-irregular-galaxies-current-dark.html#jCp http://phys.org/news/2016-09-spiral-irregular-galaxies-curre...
sampo 10y ago
Galaxies don't seem to obey gravity in their rotation. Take images of a galaxy, estimate the number and mass of the stars based on their brightness. Make a computer simulation using this and the known laws of gravity. In the simulation the galaxy will rotate way differently than in the observations. This happens with every galaxy, so we just don't know why galaxies rotate the way they do. There are two major theories: 1. Maybe our estimation of the mass distribution in a galaxy is wrong. We only estimate the mass based on the light of the stars we can see. So people have invented dark matter. We can add unseen matter in a certain distribution into the galaxy, until we get it to rotate, under our known laws of gravity, the way we observe it rotating. https://en.wikipedia.org/wiki/Dark_matter https://en.wikipedia.org/wiki/Dark_matter 2. Maybe our laws of gravity are wrong. Maybe the gravitational interaction works differently over very long distances than it works inside our solar system. After all, we have directly measured gravity only over distances inside our solar system. https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics Generally physicists feel that the mathematical form of the gravitational interaction is too precious to meddle with. It is easier to postulate unseen, unknown, extra mass to all galaxies, than to alter the equations of gravity. So dark matter is the more generally accepted theory. This study is purely observational. The authors observe that the deviation in the rotation of visible mass, compared to out laws of gravity, follows a nice curve with almost no scatter. This gives slightly more support to the theories of modified gravitation laws, because the deviations seem to follow a smooth pattern. But if we postulate some mechanism which distributes the dark matter just right, to follow the observations, also the dark matter theories would conform to these observations. So this is a small step in one of the big unsoveld problem in physics.
- jotato 10y ago
  Thanks!

As someone who can appreciate physics, but doesn't really know much: What are the implications of this?

by jotato 10y ago

As someone who can appreciate physics, but doesn't really know much: What are the implications of this?

"Nothing in the standard cosmological model predicts this, and it is almost impossible to imagine how that model could be modified to explain it, without discarding the dark matter hypothesis completely." Read more at: http://phys.org/news/2016-09-spiral-irregular-galaxies-current-dark.html#jCp http://phys.org/news/2016-09-spiral-irregular-galaxies-curre...

sampo 10y ago

Galaxies don't seem to obey gravity in their rotation. Take images of a galaxy, estimate the number and mass of the stars based on their brightness. Make a computer simulation using this and the known laws of gravity. In the simulation the galaxy will rotate way differently than in the observations. This happens with every galaxy, so we just don't know why galaxies rotate the way they do. There are two major theories: 1. Maybe our estimation of the mass distribution in a galaxy is wrong. We only estimate the mass based on the light of the stars we can see. So people have invented dark matter. We can add unseen matter in a certain distribution into the galaxy, until we get it to rotate, under our known laws of gravity, the way we observe it rotating. https://en.wikipedia.org/wiki/Dark_matter https://en.wikipedia.org/wiki/Dark_matter 2. Maybe our laws of gravity are wrong. Maybe the gravitational interaction works differently over very long distances than it works inside our solar system. After all, we have directly measured gravity only over distances inside our solar system. https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics Generally physicists feel that the mathematical form of the gravitational interaction is too precious to meddle with. It is easier to postulate unseen, unknown, extra mass to all galaxies, than to alter the equations of gravity. So dark matter is the more generally accepted theory. This study is purely observational. The authors observe that the deviation in the rotation of visible mass, compared to out laws of gravity, follows a nice curve with almost no scatter. This gives slightly more support to the theories of modified gravitation laws, because the deviations seem to follow a smooth pattern. But if we postulate some mechanism which distributes the dark matter just right, to follow the observations, also the dark matter theories would conform to these observations. So this is a small step in one of the big unsoveld problem in physics.

jotato 10y ago
Thanks!