Name: 【TED-Ed】The fundamentals of space-time: Part 2 - Andrew Pontzen and Tom Whyntie
Uploaded: 2015-02-01T04:21:38.000Z
Duration: 4 min 50 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Light: it's the fastest thing in the universe,

which takes a flipbook of animation panels,

In this lesson, we'll add the single experimental fact

that whenever anyone measures just how fast light moves,

it's world line always has to appear at the same angle.

while I stand still and shine the laser at Tom.

First, we'll need to construct the space-time diagram.

the different panels showing the different moments in time

of the laser light at its correct fixed angle,

But that space-time diagram represents Andrew's perspective.

how to get Tom's perspective moving all the panels

along a bit until his world line is completely vertical.

But look carefully at the light world line.

I'd measure light traveling faster than Andrew would.

says that everyone measures light to have a fixed speed.

In the 1900s, a clever chap named Albert Einstein

while still getting the speed of light right.

First, we need to glue together the separate panels

What you do is stretch your block of space-time

but at right angles to the light world line,

so this does represent the world from his point of view,

the light world line has never changed its angle,

The fence posts aren't spaced a meter apart anymore,

But that's not fair. Why don't I get to look thin?

I thought physics was supposed to be the same

Now that we know better about space-time,

Oh but to you, I appear Lorentz contracted.

Subtitles ListPlay Video

【TED-Ed】The fundamentals of space-time: Part 2 - Andrew Pontzen and Tom Whyntie

perspective

time

trick

world