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Author Topic: How fast are the celestial bodies moving apart?  (Read 2283 times)

Offline Joe L. Ogan

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How fast are the celestial bodies moving apart?
« on: 20/11/2009 16:57:29 »
It is recognized that the celestial bodies are accelerating their speed in moving apart.  How fast are they moving apart now?  Joe L. Ogan


 

Offline Soul Surfer

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How fast are the celestial bodies moving apart?
« Reply #1 on: 20/11/2009 23:17:56 »
It is not possible to anwer this question as posed because the actual speed of recession and any acceleration of this depend on the actual sepasration of the bodies that are moving apart.  The current most probable value for this is about 70 kilometres per second per megaparsec (about 3 million light years)  one mega parsec is the slightly more than the distance to the andromeda galaxy and other moderately close local group galaxies.  As the general random velocities of galaxies are in the hundereds of kilometres per second the expansion does not show up clearly until you are considerably further away than the local large galaxy clusters in Virgo and into say one hundred megaparsecs.  The observed accelerations are only a relatively small deviation from the original linear law.
 

Offline Joe L. Ogan

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How fast are the celestial bodies moving apart?
« Reply #2 on: 21/11/2009 00:51:40 »
Are you sure that the further away the celestial bodies are, the faster they are moving apart?  Or does it just seem that way?  What is the speed of the farthest two planets?  What is the speed of the two closest planets?  I am not searching for an exact answer, just a generalized answer.  Thanks for your help.  Joe L. Ogan 
 

Offline raptorguy

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How fast are the celestial bodies moving apart?
« Reply #3 on: 21/11/2009 02:09:14 »
It is recognized that the celestial bodies are accelerating their speed in moving apart.  How fast are they moving apart now?  Joe L. Ogan

Soul surfer provides a good explanation based on your question.  Your question, however, is not consistent with your follow up. Your premise of acceleration doesn't hold for celestial objects smaller than galaxy clusters. If you put a hundred mice on a rubber sheet and let them run around...some would be closer to eachother even as you stretched the sheet.   You could measure the expansion of the sheet but not provide a generalized figure for the expansion between any two mice.

Planets are stable in orbit around the Sun. Their orbital speed/ acceleration is due to orbital mechanics. I don't think any acceleration or slowing of the orbital speed of Mercury, for example, has anything of signifigance to do with the position of Venus (or vica versa).
« Last Edit: 21/11/2009 02:28:04 by raptorguy »
 

Offline litespeed

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How fast are the celestial bodies moving apart?
« Reply #4 on: 21/11/2009 17:43:45 »
SS

I suspect speed of recession from us can be calculated by Red Shift. I think I will look for a table of galaxies listed in order of red shift.  Then try to find speed calculator. Any thoughts?
 

Offline Joe L. Ogan

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How fast are the celestial bodies moving apart?
« Reply #5 on: 21/11/2009 18:29:27 »
Yes, I understand what you are saying.  I was not consistant. Thanks for poijnting it out to me.  Joe L. Ogan
It is recognized that the celestial bodies are accelerating their speed in moving apart.  How fast are they moving apart now?  Joe L. Ogan

Soul surfer provides a good explanation based on your question.  Your question, however, is not consistent with your follow up. Your premise of acceleration doesn't hold for celestial objects smaller than galaxy clusters. If you put a hundred mice on a rubber sheet and let them run around...some would be closer to eachother even as you stretched the sheet.   You could measure the expansion of the sheet but not provide a generalized figure for the expansion between any two mice.

Planets are stable in orbit around the Sun. Their orbital speed/ acceleration is due to orbital mechanics. I don't think any acceleration or slowing of the orbital speed of Mercury, for example, has anything of signifigance to do with the position of Venus (or vica versa).

 

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How fast are the celestial bodies moving apart?
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