Content of the Universe
the post had a figure with the percentages of normal matter, neutrinos, dark matter, dark energy, with the above caption and this text:
Can any body expalin this terms i.e dark energy, dark matter, normaaml matter and neutrions????
Energy is conserved with normal matter as either thermal or kinetic energy (thermodynamics). Neutrinos are involved in reactions where energy is conserved in the kinetic energy of the ejected neutrino (with near zero mass).
Dark matter is a hidden force of gravity to explain an unexplained motion of stars or galaxies.
Dark energy is a known problem for the conservation of energy.
Dark matter keeping galaxies together. Dark energy makes the universe expand. Neutrinos are products of processes in stars. Normal matter is everything you see, touch, and you are made of.
Dark matter does not hold galaxies together; dark matter is claimed to explain anomalous galaxy rotation.
I Here is a news story from a few years ago about an analysis of rotation curves in M31.
from the story:
While conventional models with Dark Matter are able to reproduce the rotational velocities of the inner portions of the galaxy, they have not explained this outer feature and instead predict that it should slowly fall off.
When a magnetic field with this value is added into the modeling equations, the team found that it greatly improved the fit of models to the observed rotation curve, matching the increase in rotational velocity.
This description must lead to this conclusion:
When cosmologist consider magnetic fields in their model the results are better than when those fields are ignored.
Electric and magnetic fields are not visible matter but they affect charged matter; stars are charged with a known electric field. These fields are dark.
M31 has a trillion stars and the galaxy model does not accurately predict all those individual stars. The rotational curve involves individual stars.
Instead of conceding we cannot predict all the individual stars in such a galaxy, we claim dark matter is the cause of the observed deviation.
For dark matter to explain the rotation curve deviation, one must define the distribution of so many kilograms of mass for this dark matter among those trillion stars. I believe that exercise has not been done for M31. We do not have the data to describe the mass and position of every individual star in that galaxy.
Dark matter is an intermediate proposal, until we truly can describe individual stars in a galaxy, not the final solution
link about M31
Yes, that's what I ment! It seems to surround single galaxies. A huge blob with some normal matter ( a galaxy) "sqeezed" in the middle. What makes those megastructures is another story.
dark matter is proposed because the model fails; When the model can match all the stars then no dark matter is needed in m31; alternately we accept the model is 99.99% to be close enough and again we don't need dark matter there.
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