How did scientists calculated mass in a way to introduce the concept of dark matter?

Discussion in 'Physics & Math' started by ash64449, Apr 26, 2013.

  1. ash64449 Registered Senior Member

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    Well,Take a galaxy for example. Find out the orbital velocities of all the stars revolving a common center of the galaxy. Well,we can calculate mass with the help of this.But what was the other way they used to calculate the mass which lead to disagreement between them and introduced the concept of dark matter?
     
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  3. ash64449 Registered Senior Member

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    why is there no reply to this thread???
     
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  5. LaurieAG Registered Senior Member

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    Hi ash64449,

    The Compton Wavelength represents rest mass while the reduced Compton wavelength represents relative mass. If you compare relative mass with rest mass you have a discrepancy that is a percentage of the ratio 2*Pi:1 or 6.3:1 depending on how representative your sample is.

    http://en.wikipedia.org/wiki/Compton_wavelength

     
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  7. Pete It's not rocket surgery Registered Senior Member

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    The other way (simplified enough for me to understand) is to look at the galaxy and see how much light-emitting matter there is.
     
  8. ash64449 Registered Senior Member

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    what is the relationship between them? How can we know the total mass by looking how much light emiting matter is there?
     
  9. eram Sciengineer Valued Senior Member

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    well, we know how much mass most stars ought to have.
     
  10. ash64449 Registered Senior Member

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    pete,i think answer to this was given by first poster... Compton wavelength.. Which is planck constant divided by rest mass times speed of light.
     
  11. ash64449 Registered Senior Member

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    well,most appropriate may be compton wavelength..
     
  12. ash64449 Registered Senior Member

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    so scientists used this method?
     

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