I can’t seem to be able to phrase my question in any simpler way.
Basically, the question refers to Einstein’s theory of relativity, and to an example used to illustrate one of its principles in the text “[Short Words to Explain Relativity](https://www.muppetlabs.com/~breadbox/txt/al.html)”.
I tried to paste the relevant fragment in its entirety, but the bot flagged it as speculative. So here’s a trimmed version I hope will pass the tests:
>We have Bert and Dana. Take a bus, and put Bert on the bus. The bus goes down the road. Dana, she sits here, on the side of the road. He’s in the bus and she’s on her ass. And now take a rock off of the moon, and let it fall at them. It hits the air and cuts in two. The two bits burn, and then land just as Bert and Dana are side by side. One hits the dirt up the road a ways, and one hits down the road a ways. **Dana sees each rock at the same time, but Bert sees one rock and then sees the next rock**.
(continued on the site)
The basic idea is that depending on the point of reference (stationary Dana vs. mobile Bert), the two rocks hit the ground either at the same time or one after the other.
I cannot for the love of me imagine how that would work. Call me naive, but something touching the ground at the same time should look the same to all observers, whether they’re moving or not. So, although I feel stupid asking you to explain something written “in words of four letters or less”, can anybody dumb it down even further?
​
In: 143
The comments here don’t seem to be doing a really great job at simplifying this. All this appears to be is a modified version of the “two lightning bolts on a train” thought experiment.
In short, Einstein realized that time is not a universal constant. Each person has their own clock and we do not observe the passage of time between each other the same way. A consequence of this is that we do not agree on the simultaneous nature of events.
If you’re standing motionless in the middle of a train platform and two bolts of lightning strike on either side of you then you might say that both strikes of lightning happened at the exact same time. To the person aboard a moving train they would say that one bolt of lightning – the bolt in the direction they’re moving towards – struck *before* the bolt on the other side of the platform – in the direction they’re moving away from. Even after you factor in the travel time of light both observers would still not agree whether each bolt of lightning struck at the same time or at different times. For one person two events happened at the same time whereas they happened at two completely different times for another.
If that seems odd think about relatively in a more familiar concept. If I’m standing on a train platform and there is a cat sitting next to me then from my perspective the cat is not moving – the distance between us never changes. For the person aboard the train the cat *is* moving – the distance between them *does* change. This misalignment between our spatial perspectives – is the cat moving or is it not moving – happens with time too. We don’t agree on whether the cat is moving or not, just like we don’t agree on whether the bolts of lightning struck at the same time or not. The only difference is that the latter doesn’t become noticeable until we’re moving at extreme speeds so it doesn’t seem intuitive for our every day experiences.
Latest Answers