Summary:
- The study of the Universe is called cosmology.
- Cosmologists study the structure and changes in the present Universe.
- The Universe contains all of the star systems, galaxies, gas, and dust, plus all the matter and energy that exists now.
- Plus all that existed in the past, and all that will exist in the future.
- The idea of a Universe has changed through human history.
- Edwin Hubble determined that there was much more to space than our own galaxy.
- Today, we know that the Universe contains about a hundred billion galaxies.