## Tuesday, July 17, 2012

### Everything Is Relative

Today’s morning lecture began with a presentation by Craig about special relativity. The general concept of relativity seems simple enough–the way that an event appears depends on where the viewer stands relative to the event–but it became suddenly mind-blowing when Craig revealed that time is in fact relative. Einstein proved that because the speed of light is always constant, sometimes one second is longer than another second. Apparently, it’s also impossible to travel at the speed of light. I wouldn’t have thought of this, but Einstein was obviously a much more creative kid than I was, and as a child he wondered what he would see if he was riding on a light wave. We now know that that can’t happen.

As an object gains speed it becomes more massive on the forward end and thus slows down enough so that the back end of the object starts to catch up, effectively shortening the object. Eventually, there is an equilibrium point, which depends on the mass of the object, where an object is moving so fast that it has too much energy for it to maintain its integrity as that object, so it begins to lose mass. I believe the lesson here is don’t break the speed limit, or you just might self-destruct.

After Craig’s talk, Bill gave a series of demonstrations about the basic principles of magnetism. I recognized most of the demonstrations from my high school physics course, although Bill’s demos were fancier and I felt as though I understood everything much better the second time around. Since Bill is in charge of the demonstration lab, it’s always a lot of fun to see what is on the magic cart for each lecture.

 Bill shows how a horseshoe magnet can move a metal rod without touching it
In addition to the relativity and magnetism lesson, we were graced with another guest speaker, Dr. James Aguirre. Dr. Aguirre also happens to be the leader of my interest group, and this morning he talked about his work as a faculty member at UPenn. He uses radio waves to study the origins of the universe, and gave us a brief history of the universe starting back at the Big Bang. He told us about an exciting project he’s working on called PAPER, which is building large radio telescopes to be placed in South Africa. These telescopes will be used to collect data about far away galaxies that aren’t easily detected with optic telescopes due to interference from the atmosphere. My interest group is building a radio telescope, so it was great to hear more about the applications of these devices.

In the afternoon we worked on potential power sources for our telescope. Ethan and I soldered exposed wire ends to a coaxial cable connector to create four different plugs for our device. Although I took two years of woodshop in middle school, I’ve never worked with solder before and it was a fun new experience, especially since neither of us got burned. Tomorrow we’ll try to hook everything up to the telescope and see how well it works. We’re supposed to have another guest speaker in the morning, and I’m looking forward to meeting yet another person who has chosen to pursue applications of physics as his life’s work.