The Big Bang Theory
This is the theory that the universe expanded from a single point.
There are two main sources of evidence for the big bang theory. The first is Cosmic Background Microwave Radiation. This is low energy radiation that can be observed in every inch of space. It is energy left over from the Big Bang. The picture below shows the low level energy in green and blue. Can you work out what the red line is?
There are two main sources of evidence for the big bang theory. The first is Cosmic Background Microwave Radiation. This is low energy radiation that can be observed in every inch of space. It is energy left over from the Big Bang. The picture below shows the low level energy in green and blue. Can you work out what the red line is?
Another piece of evidence is the redshift of stars. This is explained well in the video below.
If an object is moving while giving off a wave, like a race car giving off a sound wave, or a star giving off a light wave, the wavelength of the light will appear different to the person observing it. If the object is moving away, the wavelength becomes longer, the sound becomes lower and the light becomes 'redder'. This is redshift. If the object is moving towards us, the wavelength becomes shorter, the sound becomes higher and the light becomes bluer. this is blueshift. Scientists have measured the wavelength of light that is coming out of stars and galaxies. They have noticed that it is redshifted which means that the galaxies are moving away from us. Not only that but the galaxies that are further away are more redshifted meaning they are moving faster. This corresponds to an explosion starting at a single point. The graph on the right shows the velocity of recession, the speed an object is moving away from us, against the distance it is away from us. Hubble's law shows that they are directly proportional. This means that we can calculate the rate of expansion of the universe! |