00:03Oh, hey, hi! I'm Crazy Chris, and welcome to So Cool Science. Science you can do right at home!
00:10I'm just looking eight minutes into the past, and going over today's science file.
00:16And today's science file says...
00:19Is time travel scientifically possible?
00:24Well, that's a perfectly timed question.
00:27Alright, try this.
00:35You will need a watch with a stopwatch mode.
00:40Quick! Set your watch to stopwatch mode because it's time!
00:46The jokes just keep flying for another interactive science file!
00:52You and I are going to measure how long it takes this baseball to fall.
00:58Here's the difference. I'm going to be jumping off that desk right there.
01:03Here's what you gotta do. When I let go of the ball, you are going to start your stopwatch.
01:10And when the ball hits the ground, you are going to stop your stopwatch.
01:16Here we go!
01:19Three, two, one!
01:23Okay, how much time did you just measure? Did you measure .53 seconds?
01:29Well, I bet you did. In fact, I bet you measured less than .53 seconds.
01:35That is so weird! But here's something that's really going to pop your toaster.
01:40Okay, if I take this flashlight right here and I jump off that same desk over there, we both measure
01:45the light hitting the ground at the same time.
01:51Whoa! So, how come we don't measure the baseball hitting the ground at the same time, but we measure the
01:56light hitting the ground at the same time?
02:00Well, you don't need to go into the future to take a closer look at this.
02:06Your stopwatch doesn't match up with my stopwatch because we both measured the same event from different perspectives.
02:13From my perspective, I'm falling with the ball, so I see the ball for a fraction of a second longer
02:18than you see it.
02:19Although this is not actual time travel, it does demonstrate the big idea of Einstein's theory of relativity.
02:27The theory of relativity has to do with the observation of two or more people measuring time from different perspectives.
02:34So, if people measure time differently from different perspectives, this should also apply to light.
02:39However, the speed of light never changes.
02:42So, Einstein realized the only way for light to stay the same speed from different perspectives is if time changed.
02:51We know the theory of relativity is correct because it does take light time to travel from one place to
02:57another.
02:58This means that time travel is scientifically possible.
03:01Let's say you have 70 million light years away from Earth and had a powerful enough telescope to look back
03:07at Earth,
03:08you would see Earth 70 million years in the past.
03:13So, now you know more about the theory of relativity.
03:15You know, looking at eight minutes in the past is why science is so cool.
03:21You know, looking at all these houses are the same as well.
03:22You know, if you see a lot of the theory of relativity, you will see a lot of the theory
03:24of relativity,
03:24you know, you are going to try and keep the best of relativity.
03:25You know, when you do the theory of relativity, you can pick all of the theory of relativity and what
03:25you do.
03:25As a wave of relativity, you are going to try to change the theory of relativity.
