# QuestionGalactic Velocity in the Outer Rim

#### StevieJoseph

A while ago I saw a documentary that explained that the velocity of the objects orbiting the center of the galaxy which are positioned on the outer rim of the galaxy, match the velocity of the objects orbiting the center of the galaxy which are positioned on the inner rim of the galaxy.

I'd like to make sure that this is correct, that this is what they were talking about? Or have I misunderstood?

David-J-Franks

#### Atlan0001

A while ago I saw a documentary that explained that the velocity of the objects orbiting the center of the galaxy which are positioned on the outer rim of the galaxy, match the velocity of the objects orbiting the center of the galaxy which are positioned on the inner rim of the galaxy.

I'd like to make sure that this is correct, that this is what they were talking about? Or have I misunderstood?
To give it a living perspective, to interpret it as I believe you have interpreted it, it might mean they on the outer rim don't know they are on the outer rim, or that they have further to go around and have to travel faster to get around, than those on the inner rim. The outer rim entities think, rightly, that they are side by side close by, shaking hands, so to speak, with the inner rim entities. That there is no difference between inner and outer rims. They, on the outer rim, would then have a space and time warped -- in that sense, contracted -- relativity to those on the inner rim. There is certainly a lot of confusion and theory going on in minds as to how an why physics are as they are on the outer rim of galaxies.

#### Helio

A while ago I saw a documentary that explained that the velocity of the objects orbiting the center of the galaxy which are positioned on the outer rim of the galaxy, match the velocity of the objects orbiting the center of the galaxy which are positioned on the inner rim of the galaxy.

I'd like to make sure that this is correct, that this is what they were talking about? Or have I misunderstood?
I doubt they are quite the same velocity, but they certainly could be close.

It was Vera Rubin who discovered essentially this same thing for the larger Andromeda galaxy. This was the first strong evidence that galaxies have more matter than just visible matter, hence dark matter became more evident. So, it's reasonable that this is true for our galaxy as well.

Of course, don't confuse orbital velocity with angular velocity. The orbital period will be vastly different for those farther away from the center, so it won't look like a solid disk that is rotating.

StevieJoseph

#### Curiosity killed the cat

The velocity of the planets in our solar system behave as predicted, with the velocity of each planet decreasing in line with its greater distance from the sun. The closer to the sun a planet is, the faster its orbital velocity will be. This is not so with the velocity of the stars orbiting the centre of mass of spiral galaxies. The outermost and innermost stars in spiral galaxies orbit the galactic centre at the same velocity, with in some cases the outermost stars having slightly higher velocities. So... Yes, you have understood what has been detected.

As for the cause of this seemingly anomalous phenomenon... Unfortunately its yet another known unknown..

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