The speed of light is a topic we have studied for years. It has been proven that the speed of light travels at about 186,000 miles per second. It is thought that Aristotle was the first scientist to bring up the topic of the  speed of light, where he says the light from the sun must take some time to get to the Earth, because of its extreme distance away. Shortly after, Galileo stated that light must travel faster than sound. Even little things on a day to day basis take time for our eyes to process. For example, when we glance at the clock, we aren’t seeing the clock in that exact moment, but instead a fraction of a second in the past.

  Galileo Galilei

One of the next big things brought up in science is the fact that when you are looking at stars in the night sky, you are actually looking into the past. We know light travels extremely fast, but it is not fast enough for us to see the light from the stars that quickly. In order for the light to get from the Sun to Earth, it takes about eight minutes. Therefore, any star further than that would obviously take much longer. One star, Alpha Centauri, takes about 4 light years to reach the Earth, so whenever we see that star, we are seeing what it looked like four years ago. Some stars even take years for us to see their light. When you really think about this, it makes you really think because this means we are never really seeing the present light of the stars. The telescopes that we use to see the stars are actually having us look at the past. For example, one astronomer, Richard Ellis used the Hubble Telescope to travel to the time of the Big Bang. Ellis searched for the stars called the First Light, which were the stars that formed when gas filled the Universe and collapsed, causing the formation of these stars. Finding these stars can be challenging because they are about 10 million light-years away. Along with the Hubble Telescope, Ellis used a magnifying glass because the light of the stars was so faint. He was able to see stars about 2-3 million light years away. This was the group of stars that Ellis and his team saw through the telescope and magnifying glass.

Another thing that surprises a lot of people is the fact that we can actually see stars that have been dead for several years. This is because the light of the stars takes such a long time to reach Earth. Therefore, a star that has a 5 year light year time period but has died 2 years ago can still be visible to us humans on Earth.

http://galileoandeinstein.physics.virginia.edu/lectures/spedlite.html

http://science.nasa.gov/science-news/science-at-nasa/2002/08feb_gravlens/