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Edwin Hubble 

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Image #1

Astronomer Edwin Hubble, 1889-1953, in whose honor NASA’s finest space telescope is named.
   Edwin Hubble  

Plot of Distance Versus Velocity
Image #2

Hubble made a plot like this. For many distant objects, he measured their distance, which determines how high up they are plotted, and their velocity, determines how far to the right they are plotted.
Image #3

Supernovae at the same distance are all on the same horizontal line, but could have different velocities and therefore be plotted at different points on that line….

Velocities of Supernovae
Supernovae at the same distance

Image #4

 …but in our universe, all the supernovae at the same distance are actually moving away from Earth at the same velocity – so they are all plotted at the same point.

Image #5

Hubble also showed that for objects moving away from us,  their velocities are proportional to their distance from us – this is Hubble’s Law.
Hubble's Law
Hubble's Laaw
Image #6

Imagine that all vehicles leaving Seattle's Space Needle obey Hubble’s Law: V=Hd. Now imagine time running backwards. Two hours ago, every vehicle would have been at the Space Needle. Since all galaxies in our universe obey Hubble’s Law, they must all have been in the same place at one time – that time is the Big Bang.

Image #7

Galaxies are not actually moving through space, all with the proper velocities. Rather it is space itself which is expanding and carrying along all it contains.
This example illustrates a tape stretching in only 1 dimension, but our space is expanding in all 3 dimensions at the same time and at the same rate.

Image #8

The most precise modern measurements, made with the Hubble Space Telescope, show that space is expanding faster and faster – space is accelerating.




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