CMB and Big Bang Evidence...

First they thought that they were picking up signals from nearby New York City...

Summary.

The 2 main pieces of evidence to support the Big Bang Theory are:

2: The universe is filled with a microwave wavelength background radiation. This is a cooled and red shifted remnant of the energy released by the big bang.

1: The light from distant Galaxies is red shifted. The further away a galaxy is, the bigger its red shift. This means all Galaxies are moving away from each other at high speeds, and must have started expanding from the same point..

Both bits of evidence show that the universe has been expanding and cooling for 13.6 billion years. We have NO IDEA what the universe was like before it expanded, or why it expanded.

"According to Red Shift, the entire universe seems to be "expanding"... it must have been smaller a long time ago.

Edwin Hubble, 1929

"Perhaps, long enough ago, the entire universe expanded rapidly from a very compressed state..."

Georges Lemaître, 1931

"I refuse to accept that the universe was formed in a huge "big bang" - where did all the energy go?"

Fred Hoyle, 1949

"My maths shows that EVERYTHING must have been at the same spot before expanding rapidly. All we need to do now is find the missing energy"

Stephen Hawking, 1964

The Big Bang: The Evidence - Part 2.

In the beginning, there was "nothing"... which then "exploded"... [not really - that is a silly way of saying it]

What evidence is there that supports this idea?

Bit of Evidence #1: Red Shift...

• As we saw last lesson, all galaxies are moving away from one another... we know this as lines in their spectra are shifted to the red end (light is being stretched as they move away).

• This means that at an earlier time, they must have been closer together...

• At some point in time, they must have all been at the same point (a "singularity") before moving apart.

Where is the energy from the "Big Bang"?

BUT... shouldn't an event that huge release a LOT of energy, which we should be able to detect?

For decades after Hubble's observations, people found it hard to agree with the idea of a "big bang".

Robert Wilson (left) and Arno Penzias (right), pictures in front of their radio telescope in New Jersey, USA,1964

Using this telescope, they accidentally picked up a very faint signal which they could not explain. Their experimental process went a bit like this...

Enter these 2 Physicists...

BUT the faint signal was everywhere - they found this out by pointing the telescope in different directions at different times of the year, and by cutting the power to NYC.

Confused, they then checked their telescope. It was full of Pigeon poop...

After this, they gave up and went ahead and published their findings anyway...

Then other Astronomers noticed what they had discovered - evidence of a LOT of energy released by the "Big Bang".

Over billions of years, the universe had cooled and expanded, red-shifting this energy to a temperature of -270 degrees centigrade... 3 degrees higher than absolute zero.

Penzias and Wilson won the Nobel Prize for their discovery - and it was an accident

This was then cleaned out and they had the pigeons shot...

But the noise still remained.