 In this video, we're going to look at the Big Bang Theory and the evidence to support it. The Big Bang Theory states that the universe began with a colossal explosion about 13,700 billion years ago and has been expanding ever since. There are two pieces of evidence for the Big Bang – cosmic microwave background radiation and redshift, disconnect a TV from any cable connection, tune it to a channel with no station in your area. Not picking up any signal, you will see a fuzzy picture that we commonly call static or snow. The technical term for this static is white noise. Now imagine attaching a TV to an antenna large enough to pick out even the weakest signals from all that noise. To further enhance your ability to pick up weak signals, you would need to eliminate all background sources of noise. So, imagine systematically identifying and then eliminating all possible sources of noise. In the early 1960s, Arno Penzias and Robert Wilson did just that. They weren't using their TV, they used a microwave receiver attached to a large horn-shaped antenna. They were working for Bell Labs, who wanted to use the microwave receivers they had developed for long-distance communication. To pick up the weak celestial signals, Penzias and Wilson worked to eliminate all the noise originating from their antenna and receiver. The last stubborn little bit of noise wouldn't go away no matter what they tried. They even crawled into the antenna, chased away the pigeons and removed a nest and pigeon poo, but it didn't work. The noise was still there. As the earth turned, their antenna pointed to different parts of the solar system. If the source of these mysterious microwaves was in the solar system, the strength of this noise should vary as the earth turned on its axes. It didn't. This suggested that the noise did not originate in the solar system. So where was it coming from? The earth continued its annual journey around the sun. If the microwaves originated from a distinct location in our galaxy or perhaps another galaxy, then the noise level should increase when the earth was on the same side of the sun as the source of the microwaves. The noise level didn't change as the earth orbited the sun. Penzias and Wilson were confused. Around the same time, Robert Dickey was investigating something called the Big Bang Theory. He thought that if this theory for the origin of the universe was correct, the whole universe should still have some microwaves present. Then Dickey heard about Penzias and Wilson's experiments. The microwaves turned out to be what was left after 10 to 20 billion years of the expansion of space, being the remains of the heat of the Big Bang. These microwaves are called Cosmic Microwave Background Radiation or CMBR. So what about the other evidence for the Big Bang? Redshift. Redshift shows how the light from distant stars is shifted to the red end of the spectrum as the wavelength increases. The further away the star, the greater the redshift, which means the more distant a galaxy is, the faster it is moving away from us. This suggests that the universe is not static as was once thought, but is in fact expanding. For more on the Redshift, watch this video. So there you have it, that's exactly what the Big Bang Theory states and the evidence for it.