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marcus

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**Cosmo calculator--recession speed tutorial**

This thread could be a tutorial/discussion using Morgan's online calculator that calculates recession speeds, if you give it the redshift.

If you try out the calculator and have questions, or are surprised by anything, please ask. No telling what you get for answers

maybe some that conflict :surprised: but by asking you at least start the process of getting clear about redshift and recession speed.

Lots of stuff is observed to have redshift 2 or more, some quasars we observe have redshift over 6, and the CMB has redshift 1100.

With Morgan's calculator you can enter a redshift, like 2 or 6, and find out the present distance to that thing, and how fast it is receding---how fast the distance to it is growing (assuming it is stationary in the space around it wrt CMB).

http://faculty.cns.uni.edu/~morgan/ajjar/Cosmology/cosmos.html [Broken]

You've heard that Dark Energy is 73% and the combined total for matter including ordinary and dark matter is 27% and you probably have seen the figure for the Hubble parameter that is commonly used, which is 71 km/second per Megaparsec. MORGAN BELIEVES YOU SHOULD WORK A LITTLE SO TO USE THE CALCULATOR YOU HAVE TO TYPE IN 0.27 and 0.73 and 71

Morgan makes you type in values of Omega matter density (.27) and Lambda dark energy density (.73) yourself. And the current best figure for the Hubble parameter 71. THEN YOU TYPE IN THE REDSHIFT, like say 6 for a distant quasar. So what you've typed in from top to bottom:

.27

.73

71

6

Then press "calculate" it will tell you the recession speeds. And how long ago it was that the quasar was radiating the light that we are now getting from it.

And how far away it used to be when the light left it on its way to us, and how far away the quasar is at the present time.

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