It may not be obvious, but what you are seeing is actually the past. What the? Who the? How the?
I know, it sounds incredibly weird. How can what we are currently seeing be the past, when it's clearly the present? Ok, I don't even understand what that means.
We all know that light travels around 300,000,000m/s in vacuum right? That is very fast, I mean, REALLY FAST! Anyway, when light travels through a non-opaque medium like air, it slows down. It's not very hard to understand why that happens.
Supposed that you are a light particle, a photon! Let's assume the empty LRT station be the vacuum of space. Don't you think it is easy to run around the station?
Now, imagine it is rush hour, and suddenly, the whole place is filled with smelly and fat people. Each person is like a molecule in the non-opaque matter which I mentioned above. I mean, there are so many people, it's so hard to move around, so you slow down. Likewise, light travels slower in a denser medium.
Well, anyway, back to the matter at hand. Why did I say that what ever you are currently looking at is the past? Like I said, light need to travel to your eye before you can actually see.
Assuming the distance between your eyes and the monitor of the screen is 30cm. Speed of light=300,000,000m/s. If you work it out using the Speed=Distance/Time formula, you'll find that time=1 nanosecond.
So, what you are seeing on the screen now happened 1 nanosecond ago! But 1 nanosecond is so tiny, you won't be able to notice it. Cool right?
Oh, this will be even cooler if you could see a delayed reflection of yourself on the mirror. Let's say you are standing in front of a mirror, then you move your arm. 1 second later, you'll notice that your image moves his arm. To actually see this delay, you'll have to be standing 300000km away from the mirror.
Light, isn't it cool?
