Dark Matter & Its Effects on Regular Matter

In summary, dark matter's extremely low density in the solar system makes it difficult for it to have a significant effect on regular matter, despite being present everywhere. The solar system's relatively high density compared to the surrounding region of the galaxy also contributes to the lower likelihood of dark matter affecting the orbits of planets.
  • #1
MNyberg1020
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If dark matter really does exist everywhere, and is constantly passing through our bodies, why doesn't this extremely dense matter affect regular matter? How are the atoms of our body not pulled by dark matter's gradational field? Also, if dark matter is thought to exist because stars in galaxies are moving too fast to be held in orbit by regular matter alone, why doesn't our solar system demonstrate those same properties if dark matter is everywhere? Why do the velocities of our planets drop the farther they are from the sun? Shouldn't our planets be affected by dark matter too?
 
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  • #2
MNyberg1020 said:
why doesn't our solar system demonstrate those same properties if dark matter is everywhere? Why do the velocities of our planets drop the farther they are from the sun? Shouldn't our planets be affected by dark matter too?

I've done the crude analysis in the past somewhere on this forum, but I don't feel like digging up the post... The point is, if you do the calculation, you find out that the total mass of dark matter within our solar system should be ~10^19kg, roughly uniformly distributed between the sun and the outer edges of the Kuiper belt. Now, 10^19kg is around the mass of a medium sized object in the asteroid belt. So, to begin with, the gravitational perturbation from such an object is tiny, but then considering that it is smeared out over dozens of AU makes the effect much more difficult to detect.
 
  • #3
MNyberg1020 said:
If dark matter really does exist everywhere, and is constantly passing through our bodies, why doesn't this extremely dense matter affect regular matter? How are the atoms of our body not pulled by dark matter's gradational field? Also, if dark matter is thought to exist because stars in galaxies are moving too fast to be held in orbit by regular matter alone, why doesn't our solar system demonstrate those same properties if dark matter is everywhere? Why do the velocities of our planets drop the farther they are from the sun? Shouldn't our planets be affected by dark matter too?

If you were to take the mass of the Sun, planets, etc of the solar system and divide it into the volume of the solar system, the average density you got would be much much greater than if you were to take the mass of all the star systems in a large local section of the galaxy and divide it into the volume of that section. In other words, the Solar system is a dense pocket compared to the local region of the galaxy.

Now consider that the vast majority of visible mass of the galaxy is constrained to a disk and dark matter is spread out in a spherical volume enclosing that disk. So even though there is ~5 times as much dark matter than visible matter in the galaxy, it is not dense, but rather spread out over a much larger volume and very thinly. So as Nabeshin has already said, you would expect to find very little dark matter within the Solar system.
 

1. What is dark matter?

Dark matter is a type of matter that cannot be seen or detected by any form of electromagnetic radiation. It is believed to make up about 85% of the total matter in the universe and its existence is inferred by its gravitational effects on visible matter.

2. How does dark matter affect regular matter?

Dark matter has a gravitational pull on regular matter, causing it to clump together and form large structures such as galaxies and galaxy clusters. It also helps to keep galaxies from flying apart due to their high speeds of rotation.

3. Can dark matter be detected?

Currently, there is no direct way to detect dark matter as it does not interact with light. However, scientists are able to indirectly detect its presence through its gravitational effects on regular matter and by studying the motion of stars and galaxies.

4. What are the properties of dark matter?

The properties of dark matter are still largely unknown as it has not been directly detected. It is believed to be non-baryonic, meaning it is not made up of the same particles as regular matter. It is also thought to have a very weak interaction with regular matter.

5. How does dark matter contribute to the formation of the universe?

Dark matter played a crucial role in the formation and evolution of the universe. Its gravitational effects helped to pull regular matter together, leading to the formation of galaxies and galaxy clusters. Without dark matter, the universe would look very different and it is still a major topic of study for scientists trying to understand the origins of the universe.

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