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Dark Matter

Thursday, October 15, 2020

I never believed in "Dark Matter". Like that 10% of the matter in the universe is in stars, and 90% is not seen

Well, if the other 90% is not visible, how do you know it is there? I just didn't believe one could know.

Then I read that galaxies are spinning too quickly, like there is more of a gravitational force pulling them together than expected, which allows them to spin faster.

But how do you know the galaxies are spinning too quickly, they don't change much in even 100 years. Then I read up. Hydrogen burning in stars emits light a very specific frequency. A galaxy rotating with some stars moving towards you, and some away will have a doppler shift in this precise frequency. Sort of like a train when blowing its horn goes past you, you hear the drop in frequency from higher to lower. So the spread out of this frequency tells you how fast the galaxy is spinning.

They are spinning too fast, so there is some "dark matter" helping pull them together, allowing them to spin faster.

Pretty cool if you have a background in physics, ... and I do.
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Member Comments About This Blog Post
    A perfect creation. emoticon
    38 days ago
  • WILDKAT781
    very interesting. I understand the basics, but not the nitty gritty
    38 days ago
  • -JAMES-
    It's "important" because its a question of if the universe will collapse back on itself, or keep expanding forever.

    But there are more "pressing" matters. In about 7 billion years ( 7,000,000,000 ) our sun will run out of fuel.
    40 days ago
    Waaaaay beyond my pay grade!
    40 days ago
  • -JAMES-
    Its like when you are on a playground merry-go-round and feel yourself flung to the outside. You need to pull towards the middle to stay on. If the merry-go-round goes faster you need to pull harder.

    In this case the pull is coming from gravity. If the galaxy (or merry-go-round) is spinning faster than expected, the force to the middle must be more than expected too. Dark matter provides the unexpected force.
    40 days ago
  • BJAEGER307
    Interesting, way above my head, but interesting the same.
    40 days ago
    Interesting. I am going to show this to my DH. He always is interested in physics.

    40 days ago
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