- #1
Ranku
- 410
- 18
Is there any astronomical indication that gravitational force between dark matter might be weaker than between visible matter?
Since dark matter is characterized entirely by its gravitational effects, those effects are, by definition, the same as for regular matter.Ranku said:Is there any astronomical indication that gravitational force between dark matter might be weaker than between visible matter?
The question does not make sense within GR. It follows from the equivalence principle that gravity must work the same way regardless of the source.MikeeMiracle said:Unless the question was between dark matter and itself and between regular matter and itself. Am I correct in stating that regular matter will attrack itself stronger than Dark Matter will attract itself or is it the same do we believe?
Ranku said:Is there any astronomical indication that gravitational force between dark matter might be weaker than between visible matter?
MikeeMiracle said:If bigger / heavier particles attrack each other stronger than smaller / lighter particles
Vanadium 50 said:How could you even tell? All we know gravitationally is the product GM. If G is weaker ... the inferred M is bigger. Or vice versa.
It's not the size of the individual particles that make up the mass that counts, it is the total mass. If you start with two static clouds of equal mass and size, one made up of smaller particles and the other, larger ones, they would collapse at the same rate. The cloud made of larger particles would have fewer particles spaced further apart than the cloud with the smaller particles in order for the clouds to have the same total mass and distance between particles also plays a role in the strength of gravitational attraction.MikeeMiracle said:If bigger / heavier particles attrack each other stronger than smaller / lighter particles, and DM is a heavy particle then it should collapse / attrack itself faster than baryonic matter. That's where I was going with the question, can we tell the likely size of DM particles by their rate of collapse / attraction? Although thinking about it, we don't really have a good enough picture of them to be able to answer the question I don't think.
This assumes collisionless particles. In reality, normal matter is not collisionless but heats up and radiates away energy. This is why normal matter coalesces into stars, planets, etc, while dark matter forms more loosely bound halos.Janus said:If you start with two static clouds of equal mass and size, one made up of smaller particles and the other, larger ones, they would collapse at the same rate.
Dark matter gravitational force is a hypothetical force that is believed to be responsible for the gravitational pull of dark matter, a type of matter that does not emit or absorb light and is therefore invisible to traditional telescopes. It is thought to make up about 85% of the total matter in the universe.
Dark matter gravitational force is different from regular gravity in that it is believed to be much stronger and able to act over much larger distances. It is also thought to be the dominant force in the universe, while regular gravity is just one of the four fundamental forces.
The main evidence for dark matter gravitational force comes from observations of the rotation of galaxies. The observed rotational speeds of stars in galaxies are much higher than what would be expected based on the visible matter in the galaxy. This suggests the presence of an invisible force, like dark matter gravitational force, that is holding the galaxy together.
Dark matter gravitational force is thought to play a major role in the expansion of the universe. It is believed to counteract the effects of dark energy, another mysterious force that is causing the universe to expand at an accelerating rate. Without dark matter gravitational force, the universe would not be able to hold itself together and would expand at a much faster rate.
At this time, there is no known way to harness dark matter gravitational force for practical use. It is still a largely unknown and mysterious force, and scientists are still working to understand its properties and behavior. However, further research and understanding of dark matter gravitational force could potentially lead to new advancements in our understanding of the universe and perhaps even new technologies in the future.