RE: How Do Scientists Know It's Space Expanding Not Galaxies Moving?
August 10, 2017 at 11:25 am
From the 1987 supernova, we could measure (via spectroscopy) how fast the side of the explosion facing us is coming towards us.
We can also see how fast the thing is expanding side to side. Pretty easy to work out how big it is, very precisely, at any given time, and then by seeing how big it looks from here, it's a simple matter to calculate very precisely how far away it is.
And the more precisely we know how far away stuff is that is relatively close, we can work out other associations and calibrate them to see how far away more and more distant objects are.
We can also see how fast the thing is expanding side to side. Pretty easy to work out how big it is, very precisely, at any given time, and then by seeing how big it looks from here, it's a simple matter to calculate very precisely how far away it is.
And the more precisely we know how far away stuff is that is relatively close, we can work out other associations and calibrate them to see how far away more and more distant objects are.
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