1. The theory of the universe

2. Expanding of our universe In the 1920s, astronomers had the technology to see more Celestial bodies with advance telescope. Celestial bodies is a term for object in the sky. Later on Edwin Hubble was the first astronomer to see other galaxies not including the milky way. Milky way is a galaxy and earth is only a tiny planet that is part of it. He also found out that other galaxies is emitting a red shift light. Meaning it constantly moving away from us. Like a balloon being blown up, the galaxies and stars on it. The space between the galaxies expands.

3. Cosmic Background Radiation Cosmic Background Radiation is a map of the early universe. Arno Penzias and Robert Wilson, two astronomers was monitoring the microwave radiation in space. They kept getting signal interference. And they believed this signal interference is cosmic background radiation and is the radiation left over from the Big Bang. NASA also help by launching a satellite so it can map out the cosmic background radiation. The data received were then gathered by the Cosmic Background Explorer. The Wilkinson Microwave Anisotropy Probe was launched in 2001, gathering more precise data, which showed the dense region of the early universe and the less dense region.

4. Red shift Red Shift is a light wave that is stretched because the object is far away. Which makes a red light. Similar to sound waves. The other galaxies is giving off electromagnetic radiation and visible light is one part of it. The radiation is carried like a wave. A spectroscope is an instrument that let the viewer see the spectral lines that the object is giving off. And the other galaxies were giving off red light. As the space between earth and distant galaxies increases and the galaxies are moving away, the light wave that was given by the distant galaxies are now stretched and lengthened which is cause by the universe expanding. Astronomers call this the cosmological red shift.

5. Big bang theory Because of our universe constantly expanding like a balloon, there has to be a start of inflation. At start which was approximately 13.7 billion years ago, the universe was very small. And in a very short time it expanded however they do not know what started it. The physicist Georges Lemaitre was the first one to describe the Big Bang Theory.