The Expanding Universe
The Universe is composed of matter and energy. All of the matter in the Universe now has been in the Universe since it formed. There is evidence to support that scientists are able to estimate the age of the Universe in two ways:
1. By looking for the oldest stars:
- Nebula (gas and dust) exist in space and are remnants from the formation of the universe.
- Stars undergo a life cycle based on the composition of the gases within them. As stars age the amount of hydrogen in the star changes, therefore changing the color and brightness of the star.
- Astronomers determined the Universe is expanding based on the color of light emitted from galaxies and stars.
- As the Universe expands and galaxies move apart, the wave-length of light emitted from those galaxies is stretched. This shifts the light toward the red end of the spectrum and is called “red-shift”. The more distance or faint a galaxy the more rapidly it is moving away from Earth.