When I was around 12 or 13, I first got a hold of my stepfather’s physics text book. It was magic. The rules that governed the physical world were right there in the form of equations on a page. I was totally captivated. Newton’s laws of motion, gravity, angular momentum, and the theory of relativity. When I first learned about relativistic time dilation, it was life-changing. I resolved to become an astrophysicist. A lot of changes happened in my life that turned that dream into my current one. But, like all first loves, it never went away.
When I got my first computer, I had hopes of writing a program that would plot the positions of the stars as they were in space (3-D) versus how they appeared in the Earth’s sky (2-D). I achieved a little bit of success getting the vectors worked out from the distance, right ascension, declination and so on. I had no easy way of visualizing it though. Doing 3-D plots in BASIC back in 1990 wasn’t the easiest thing in the world. So that project died.
Then like a ghost, Celestia came to me last night. Wrapped up in her open source glory, I dared not even dream that she could perform what I had so long abandoned all hope of. But she did my friend, she did. (My wife won’t like this imagery :))
Anyhow, Celestia is a totally kickass program for the Mac, PC and Linux that lets you navigate space. You can go into orbit around Phobos and watch the sun rise over the horizon of Mars. You can latch onto the back of the International Space Station and watch the Earth fly by beneath you. You can jump into hyperspace and visit Betelgeuse or Antares. You can watch the Milky Way grow small beneath you as you rocket many megaparsecs to galaxy NGC-4732.
One of my early motivations for wanting to be able to make a program that can do this is to be able to really visualize what a constellation looks like. We look up in the sky and see the Big Dipper, but those stars are really, really, really far apart. From the view of anywhere but Earth, they don’t form a constellation at all. They aren’t even barely neighbors. Celestia lets you see just how jacked up constellations are in real space. I love it.
You can also record movies of your random flights through space and write (and run) scripts that take you on tours of celestial objects. You can watch Saturn from the perspective of the Cassini probe (in real time). Seriously, does it get any cooler?