# Image Credits

Hello! My name is J------ and I am a high school junior in Maryland. I am currently enrolled in a Trigonometry class. My teacher has asked us to write a paper on how trigonometry affects my life and careers. I have spent hours researching this and I have found that trigonometry has affected astronomy as well as many other professions but once I read over the information it does not ever tell me how. The websites and such simply tell me formulas which are complicated and I don't understand their meanings and uses. So my question to you is, how is astronomy influenced or impacted by trigonometry? Is it greatly used and if so to find what? I would greatly appreciate it if you would reply to my question quickly. Thank you very much in advance for your reply and time.

Probably the biggest impact that trigonometry has had in Astronomy is in the finding of distances to nearby stars through the method of parallax. As you know, the Earth orbits around the Sun once a year. This means that at six month intervals the Earth is looking at a star from the two corners of an isosceles triangle (where the point is at the star). We can observe how far the star appears to move against the background galaxies in that time and find the angle of the triangle from that. With the angle and the length of the base (the diameter of the Earth's orbit) we can find the height of the triangle - or the distance to the star. See the image below.

The movement of the star against the background as we orbit the Sun is called its parallax. In fact you've probably observed parallax when you travel in the car. You might notice that the nearby bushes (or other objects) along the road appear to move with respect to more far away things as you travel along the road. You can also observe the parallax of your thumb if you hold it at arm's length and look at it with alternating eyes shut. Again, it should appear to move with respect to the background. If you knew the distance between your eyes and could measure the angle your thumb appeared to move by you could find out the length of your arm by doing this.

#### Karen Masters

Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.

Website:  http://icg.port.ac.uk/~mastersk/

## Our Reddit AMAs

AMA = Ask Me (Us) Anything