Headings The Earth
and Beyond Universe
Search Questions
gcsescience.com 41 gcsescience.com
The Universe - Big Bang - Red-Shift - Expanding Universe (continued).
Following
on from the previous
page, imagine that the
same object
is now moving
away from you at the same speed.
During the
time it has taken to emit one complete
wave,
the object would have moved
0·1 metres
away from you.
The wavelength has been increased
because the whole wave now takes up
1 + 0·1 metres, or
1·1 metres.
An
increase in the wavelength of light
is called a red- shift.
In reality light travels so very fast
that you can't tell that the wavelength has changed
unless the object emitting the
light is moving extremely
fast.
The amount of time it takes to emit
one light wave is tiny.
No object
on Earth could have moved far enough in this time
to produce a noticeable change in wavelength.
In
summary, light from an object
1. Moving fast towards you -
wavelength decreases - blue-shift.
2. Which is stationary -
wavelength stays the same -
no shift.
3. Moving fast away from you - wavelength increases
- red-shift.
Since the
light from other
galaxies is red-shifted,
these other galaxies must be
moving away from us
very quickly.
The further away the galaxy is, the greater the red-shift
and the greater the speed at which it is moving away from
us.
If all places in the Universe are moving
away from us,
then the Universe must be getting
bigger - it is expanding.
Headings The Earth
and Beyond Universe
Search Questions
gcsescience.com Contents Index Quizzes gcsescience.com
Copyright © 2008 Dr. Colin France. All Rights Reserved.