BIG BANG
BIG BANG
Cosmology: The study of the cosmos aka the structure and function of the larger universe.
BIG BANG
BIG BANG
From the beginning of astronomy through the early 20th century the universe is thought to be static/balanced. Stars may come and go, the surface of the earth changes slowly, but things are generally thought to be in balance. Universe is thought to be infinitely old; it always has been and always will be.
BIG BANG
*NOTE: Science and scientific knowledge is based on observation. When observation does not agree with established knowledge, it must be further studied and reexamined; albeit slowly, cautiously.
BIG BANG
In 1912 Vesto Slipher observed 25 galaxies to all be receding away from us. Many other observations over the years confirmed this and it was proposed for the first time that the universe is expanding, not static. Much of the scientific community didn’t like it, but the evidence could not be explained any other way.
BIG BANG
Sir Edwin Hubble made detailed observations of many galaxies and found that the further away a galaxy was, the faster it was moving away. He discovered this by their RedShift.
This is accepted as conclusive evidence of an expanding universe.
BIG BANG
BIG BANG
More importantly, this implies for the first time that the galaxies are not actually moving away, but that the space that contains the galaxies is expanding.
BIG BANG
This new theory had an unsettling consequence; if the universe is getting bigger today it must have been smaller in the past. If you go back far enough how small would it be?
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It is proposed that the universe began as a very small, very dense “egg” or “primordial atom” with everything packed into a space that has no volume at all; a mathematical point.
BIG BANG
In trying to discredit such a ridiculous theory, astronomer Fred Hoyle mockingly coined the term “Big Bang”. The name stuck despite the theory gaining universal acceptance.
BIG BANG
BIG BANG
For any theory to gain acceptance it must make accurate predictions. Big Bang Theory made several bold predictions…
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Prediction #1: MBR
Calculations based on the Big Bang Theory predict that the earliest (farthest) light we should be able to see would be red-shifted to the microwave range.
In 1964 faint microwave radiation was discovered coming from everywhere at once with no identifiable source. This is known as the “Cosmic Microwave Background”.
BIG BANG
BIG BANG
Prediction #2: H & He
Calculations based on the Big Bang Theory predict that the ratio of Hydrogen to other elements should be very specific.
As we have gotten better at identifying the amounts of elements throughout the Universe we find these exact ratios.
BIG BANG
Prediction #3: Matter Distribution
Calculations based on the Big Bang Theory predict that matter should be distributed throughout the universe in a particular way.
As we have become increasingly accurate in our mapping of the universe, we see this very distribution.
NOTE: All of these were predicted by the Big Bang theory before they were discovered independently.
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A common misconception is that the Big Bang was an explosion in space. All of space-time and matter was created in the Big Bang. Space (empty space) was actually created by the Big Bang.
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In the Big Bang model, from any point in the universe it will appear as though the entire universe is moving away from that point.
BIG BANG
Based on observation, Hubble derived this relationship known today as HUBBLE’S LAW:
v = H0d
v = velocity of a receding galaxy
d = distance of this receding galaxy (Mpc)
Ho = Hubble constant (70 km/s/Mpc)
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Example:
A distant galaxy has an observed velocity of 2x105 km/s.
How far away is it?
v = H0d
d = v/H0
d = (2x105 km/s)/70 km/s/Mpc
2816 Mpc
[8.64x108 ly]
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The Hubble Law gives us the age of the universe.
The most distant object have a velocity just below the speed of light. This velocity yields a distance of 13.8 billion light years. Therefor the universe is 13.8 billion years old.