There's a really good chance that you're not as nerdy as I am. I'm neither bemoaning the fact nor bragging (is nerdiness even braggable; is braggable even a word?). I'm just stating a probabilistic [Exhibit A] fact. Two nights ago I played a strategy game that featured cards called "King's Court", "Duchy", "Nobles", and "Steward" [Exhibit B]. Yesterday as I watched Moneyball, some of my favorite moments were the glimpses of the equations used to evaluate players' values [Exhibit C].
And now I'm blogging about thoughts I've picked up while reading Einstein and science fiction [Exhibit D].
The speed of light is finite, but faster than you
The former isn't obvious; the latter is routinely discarded in sci-fi
Since you're probably less nerdy than I [see Exhibits A-D above], you may not have ever thought about the speed of light. No one would blame you for this, unless you studied physics. But it's time to start thinking about it.
Because I don't know enough about relativity to actually explain it to you, I'm just going to give you a few cool things to think about. At least, I think they're cool. And as we've determined, that might not mean anything.
1. The basis of every cool sci-fi thing: the speed of light is constant
Everything else I'll say hinges on this-- light travels at a fixed, finite speed. This doesn't quite line up with our experience. It travels so fast that we sort of assume it's instantaneously everywhere. But no, when you turn on a flashlight, that light actually has to travel to the far end of the room.
2. No events are truly simultaneous
To say that two things happen at exactly the same time, what do we mean? We might imagine syncing up wristwatches or something, but the actual meaning of this must mean that an observer would 'see' (i.e. receive the light particles of) Event A and Event B without any passage of time in between. But because light has a finite, constant speed-- it matters where the observer is standing!
Consider this example from baseball: a runner tags up from third on an attempted sacrifice fly to left field. Now, suppose there are two observers: the centerfielder next to the left fielder, and the umpire next to third base. When the ball hits the glove, the light has only a tiny distance to travel to reach the CF's eyes; but when the runner's foot leaves the bag, there is a much longer distance for the light to traverse. So he sees the catch with virtually no delay, but a slight lag occurs before he sees the runner leave the bag. Thus, if he sees the two events as truly 'simultaneous', then the umpire-- with the opposite vantage point-- would fairly call out the runner for leaving early!
[Two points: I realize there would be "virtually no delay" for all events in a baseball park, but over incredibly large distances, this sort of delay for light would be extremely relevant. You might think there could still be simultaneity if you just plopped the observer at a place equidistant from the two events; but if you just altered the speed the observer is moving, the whole concept would fall apart again.]
3. Looking into the past
If you read the bracketed note above-- and I totally understand if you didn't-- you know that this only creates interesting scenarios if we have super long distances for light to travel across. And nowhere on our planet do we have a distance long enough for this fact to really play out. But if you've looked up lately, you might have noticed this thing we call "outer space".
Over the vast reaches of space, light's finite speed becomes incredibly interesting (to me). The most interesting thing, maybe, is that when we look up at the night sky, we're looking into the past.
In our baseball example, the point was that the umpire might see the runner leaving third just after it happens, but (if the baseball field were enormous) he might not see the ball hit the left fielder's glove until a few seconds after it happens. This is because the light takes a little time to travel the distance to where he's standing.
Well, space actually is enormous, so we don't have to imagine a pretend baseball game anymore. We can consider actual facts! The brightest star in our sky is Sirius. Its distance from Earth is 8.6 lightyears. What this means is that it takes light 8.6 years to travel from Sirius to us (or vice versa). So, if something crazy happens to Sirius (e.g. it explodes), we will see the event eight and a half years later! To put it another way, when you spot Sirius in the night sky, you are seeing Sirius from 8.6 years ago! What's up, Past-Sirius?
That's all my brain can handle right now
Kudos to you if you made it this far through my nerdy ramblings
There are so many other cool (to me) consequences of relativity. If objects were to travel at speeds close to the speed of light, so many crazy things would happen, including a slowing down of the passage of time for that object! Maybe I can ramble about these things another time. Now I need to go stare at a TV for a while.
What's your nerdiest pastime?
Any, um, cool physics thoughts?
Jon
