The fundamentals of space-time: Part 1 - Andrew Pontzen and Tom Whyntie
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0:07 - 0:10Space: it's where things happen.
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0:10 - 0:13Time: it's when things happen.
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0:13 - 0:14We can measure where things are
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0:14 - 0:16and when things take place,
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0:16 - 0:17but in modern physics,
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0:17 - 0:19we realize when and where
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0:19 - 0:22are actually part of the same question.
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0:22 - 0:25Because when it comes to understanding the universe,
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0:25 - 0:28we need to replace three-dimensional space plus time
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0:28 - 0:30with a single concept:
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0:30 - 0:34four-dimensional space-time.
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0:34 - 0:36We'll explore and explain space-time
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0:36 - 0:38in this series of animations.
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0:38 - 0:39Animations?
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0:39 - 0:40Yeah.
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0:40 - 0:43Well, we're not very animated are we?
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0:43 - 0:47Sure we are! Look, I can go from here to here.
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0:47 - 0:49Whoa! How'd you get from here to there?
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0:49 - 0:50How fast did you go?
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0:50 - 0:52Did you run? Walk?
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0:52 - 0:53Did you even go in a straight line?
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0:53 - 0:57Ah! To answer that, you'll need to make our cartoon physics
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0:57 - 1:00look more like physics physics.
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1:00 - 1:02You'll need more panels.
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1:02 - 1:05More panels, please!
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1:05 - 1:10Okay, in each panel, Andrew's in a slightly different place.
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1:10 - 1:12So I can see each one records
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1:12 - 1:15where Andrew is at a different time.
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1:15 - 1:19That's great. But it would be easier to see
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1:19 - 1:20what's going on if we could cut out
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1:20 - 1:23all the hundreds of panels and stack them up
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1:23 - 1:26like a flip book.
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1:26 - 1:28Right, now let's flip through the book
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1:28 - 1:31so that we can see one panel after another
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1:31 - 1:34getting through 24 in every second.
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1:34 - 1:36See! I told you it was an animation.
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1:36 - 1:39Now you can see me walking along.
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1:39 - 1:42Drawing all those panels and putting them into a flip book
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1:42 - 1:46is just one way of recording the way I'm moving.
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1:46 - 1:50It's how animation, or even movies, work.
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1:50 - 1:52As it turns out, at my walking speed,
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1:52 - 1:56it takes two seconds to get past each fence post,
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1:56 - 1:59and they're spaced four meters apart.
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1:59 - 2:00So we can calculate my velocity --
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2:00 - 2:02how fast I'm moving through space - -
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2:02 - 2:05is two meters per second.
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2:05 - 2:08But I could've worked that out from the panels
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2:08 - 2:11without flipping through them.
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2:11 - 2:12From the edge of the flip book,
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2:12 - 2:15you can see all of the copies of the fence posts
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2:15 - 2:16and all of the copies of Andrew
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2:16 - 2:20and he's in a slightly different place in each one.
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2:20 - 2:23Now we can predict everything that will happen to Andrew
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2:23 - 2:27when we flip through 24 pages every second,
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2:27 - 2:28including his speed of motion,
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2:28 - 2:30just by looking.
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2:30 - 2:33No need to flip through at all.
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2:33 - 2:35The edge of this flip book
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2:35 - 2:38is known as a space-time diagram
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2:38 - 2:40of Andrew's journey through, you guessed it,
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2:40 - 2:42space and time.
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2:42 - 2:45We call the line that represents Andrew's journey
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2:45 - 2:48his world line.
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2:48 - 2:50If i jog instead of walking,
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2:50 - 2:54I might be able to get past a fence post every second.
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2:54 - 2:56He's not very athletic.
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2:56 - 2:59Anyway, when we look at this new flip book from the edge,
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2:59 - 3:02we can do the same analysis as before.
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3:02 - 3:04The world line for Andrew jogging
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3:04 - 3:05is more tilted over
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3:05 - 3:08than the world line for Andrew walking.
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3:08 - 3:11We can tell he's going twice as fast as before
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3:11 - 3:14without flipping the panels.
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3:14 - 3:17But here's the clever bit.
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3:17 - 3:20In physics, it's always good to view things from other perspectives.
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3:20 - 3:22After all, the laws of physics
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3:22 - 3:24should be the same for everyone
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3:24 - 3:26or no one will obey them.
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3:26 - 3:29So let's rethink our cartoon
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3:29 - 3:32and have the camera follow Andrew jogging along
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3:32 - 3:35as the fence posts approach and pass behind him.
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3:35 - 3:38Still viewing it as a flip book of panels,
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3:38 - 3:40we don't need to redraw anything.
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3:40 - 3:43We simply move all of the cutout frames slightly
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3:43 - 3:45until Andrew's tilted world line
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3:45 - 3:48becomes completely vertical.
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3:48 - 3:51To see why, let's flip it.
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3:51 - 3:54Yes, now I'm stationery, just jogging on the spot,
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3:54 - 3:56in the center of the panel.
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3:56 - 3:58On the edge of the flip book,
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3:58 - 4:00my world line was going straight upwards.
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4:00 - 4:03The fence posts are coming past me.
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4:03 - 4:06It's now their world lines that are tilted.
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4:06 - 4:09This rearrangement of the panels is known as a
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4:09 - 4:12Galilean transformation,
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4:12 - 4:16and it lets us analyze physics from someeone else's perspective.
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4:16 - 4:19In this case, mine.
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4:19 - 4:22After all, it's always good to see things from other points of view,
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4:22 - 4:25especially when the viewers are moving
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4:25 - 4:27at different speeds.
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4:27 - 4:31So long as the speeds aren't too high.
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4:31 - 4:33If you're a cosmic ray moving at the speed of light,
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4:33 - 4:38our flip book of your point of view falls apart.
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4:38 - 4:40To stop that from happening,
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4:40 - 4:42we'll have to glue panels together.
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4:42 - 4:45Instead of a stack of separate panels,
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4:45 - 4:48we'll need a solid block of space-time,
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4:48 - 4:51which we'll come to in the next animation.
- Title:
- The fundamentals of space-time: Part 1 - Andrew Pontzen and Tom Whyntie
- Description:
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View full lesson: http://ed.ted.com/lessons/the-fundamentals-of-space-time-part-1-andrew-pontzen-and-tom-whyntie
Space is where things happen. Time is when things happen. And sometimes, in order to really look at the universe, you need to take those two concepts and mash them together. In this first lesson of a three-part series on space-time, hilarious hosts Andrew Pontzen and Tom Whyntie go through the basics of space and time individually, and use a flip book to illustrate how we can begin to look at them together.
Lesson by Andrew Pontzen and Tom Whyntie, animation by Giant Animation Studios.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:06
Helene Batt edited English subtitles for The fundamentals of space-time: Part 1 - Andrew Pontzen and Tom Whyntie | ||
Jessica Ruby approved English subtitles for The fundamentals of space-time: Part 1 - Andrew Pontzen and Tom Whyntie | ||
Jessica Ruby accepted English subtitles for The fundamentals of space-time: Part 1 - Andrew Pontzen and Tom Whyntie | ||
Jessica Ruby edited English subtitles for The fundamentals of space-time: Part 1 - Andrew Pontzen and Tom Whyntie | ||
Jessica Ruby edited English subtitles for The fundamentals of space-time: Part 1 - Andrew Pontzen and Tom Whyntie | ||
Caroline Cristal edited English subtitles for The fundamentals of space-time: Part 1 - Andrew Pontzen and Tom Whyntie | ||
Caroline Cristal edited English subtitles for The fundamentals of space-time: Part 1 - Andrew Pontzen and Tom Whyntie |