Dark matter

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In the energy of the universe, dark matter makes up about 25%, a quarter of the universe.

Antimatter doesn't seem to exist in the current universe.


If we look at the solar system, all the planets revolve around the sun. But it's velocity is fixed by the distance from the sun. It goes down, like one over square root of the distance. Each planet is moving at a pretty high speed around the sun. As we go farther and father away from the source of gravity. Because the gravity gets weaker by inverse square root, its reverse revolution velocity should become slower. So that's what we see in this situation. In the solar system.


But if we look at the scale of the galaxy, and this is our own galaxy. Our solar system is away from the center by 28,000 light years away. It doesn't seem to be the case. Our solar system is moving actually very fast, much faster than the entire source of gravity coming from the stars combined would support us. So something else beyond the stars exists in our own galaxy. That is pulling us inside the Milky Way Galaxy. So if we actually tried to measure this as a function of distance from the center of the galaxy, this is our solar system.We're moving at a speed of about 220 kilometers per second. But if even if you go to farther and farther away outskirts of our Milky Way Galaxy, the rotation speed doesn't seem to go down at all. And that's strange, right?


From Newton is that if the, the center of the gravity and the source of the gravity is centralized in some way. Then as you go farther and farther away from the source of gravity, we should be slowing down. But clearly things are not slowing down towards the outskirts of the galaxy, so there must be a lot more mass. That would actually keep coming in as you go farther and farther out and that's what we call the dark matter of intergalactic halo.


So even when we go to the places of the galaxy where we don't see any star at all. Then rotation speed doesn't seem to go down, so that's where we have good evidence on the existence of dark matter.

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