Image
#1
Astronomer Edwin Hubble, 1889-1953, in whose honor
NASA’s finest space telescope is named.
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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.
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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….
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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.
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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.
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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.
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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.
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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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