Light:The Instrument of Astronomy

Understanding how light works for and against us is crucial when observing the universe. Of course we need light to see, but did you know we use it in other ways? Because light can vary in wavelength and energy we use its assorted state to gather information like temperature, rotation speed, emission and absorption lines (shift in distance), and more. This is done using a method called spectroscopy.


Before getting excited about the numerous wonders of the visible universe, please take the age of light into consideration. When you look up at the night sky to see the stars, every bit of light you observe is not a current representation of how the source looks. What you are looking at is light from the past. A light-year is a unit of distance (not time) used to determine how far light travels in one year which happens to be about 6 trillion miles. If a star is 190,000 light-years away, and you observe it from Earth, you are actually seeing the light it emitted 190,000 years ago. So, it is safe to say that just because we see an object now does not mean it still exists in the present state. Until scientist discover how to travel at the speed of light, everything outside of our galaxy is impossible to reach. According to universetoday.com, the closest star to our sun is Proxima Centauri at 4.24 light-years away.

Keep this rule in mind as we explore other topics throughout the blog.

This video outlines the concept, composition, and nature of light. Phil explains how we see and don't see light.