that doesn't involve a magnetic field,

不涉及磁場的。

out between the galaxies

銀河系之間

where really there's no detectable magnetic field at all?

真的沒有可探測的磁場嗎？

Everything is moving.

一切都在移動。

There's nothing to say this point is still

沒有什麼可以說這一點仍然是

and this is the reference point we're gonna use

這就是我們要使用的參考點

and everything moves according to that point.

而一切都根據這個點來移動。

We're moving around the sun

我們在圍繞太陽運動

at about 66,000 miles an hour right now.

現在的時速約為66,000英里。

The sun is moving around the galaxy,

太陽在圍繞銀河系運動。

around the core of the galaxy,

圍繞銀河系的核心。

at about half a million miles an hour.

在大約50萬英里的時速下。

We are actually falling gravitationally into the center

我們實際上是在重力作用下落入中心。

of a cluster of galaxies

的一個星系團

at about a million and a half miles an hour.

以大約每小時一百五十萬英里的速度。

And that's just when we say relative to what?

而這只是當我們說相對於什麼？

Relative to the sun.

相對於太陽而言。

Relative to this group of galaxies.

相對於這組星系而言。

There is no absolute standard of reference in the universe.

宇宙中不存在絕對的參考標準。

(upbeat music)

(歡快的音樂)

Let's talk first about compasses,

我們先來談談指南針的問題。

and then maybe talk a bit more about the idea

然後也許再談一談這個想法

of how we locate ourselves in space in general.

在一般情況下，我們如何在空間中定位自己。

A compass is something that responds to a magnetic field.

指南針是對磁場有反應的東西。

So the reason a compass always points north

是以，羅盤之所以總是指向北方

is that it's responding to the magnetic field of the earth.

是，它對地球的磁場做出了反應。

Our planet has this wonderful core of molten metal.

我們的星球有這個奇妙的熔融金屬核心。

That metal moves around inside the earth

金屬在地球內部移動

and it generates a magnetic field that has two poles,

它產生的磁場有兩極。

a north pole and a south pole.

一個北極和一個南極。

So when you make a compass,

所以當你做一個羅盤的時候。

you make it out of something metal

你用金屬的東西來做

that can respond to that magnetic field,

能對該磁場作出反應。

and it points to the magnetic pole of the earth,

而且它指向地球的磁極。

which is very close to our North Pole.

這與我們的北極非常接近。

So, a magnetic field directs compasses.

所以，磁場會引導羅盤。

Obviously, if you go away from the earth,

很明顯，如果你離開了地球。

far away from our planet,

遠離我們的星球。

it's no longer gonna able to feel our magnetic field.

它不再能感受到我們的磁場。

So a compass will not point to the North Pole of the earth

所以羅盤不會指向地球的北極

if say, you're out by Saturn.

如果說，你被土星淘汰了。

Saturn and Jupiter are separate planets

土星和木星是獨立的行星

and they have magnetic fields of their own.

而且它們有自己的磁場。

So certainly if you were actually close to Jupiter,

所以當然，如果你真的接近木星。

Jupiter has a magnetic field,

木星有一個磁場。

much stronger than the Earth's magnetic field,

比地球的磁場強得多。

your compass would definitely point

你的羅盤一定會指向

to the North Pole of Jupiter

到木星的北極

if you were actually around Jupiter now.

如果你現在真的在木星周圍。

But what if you get farther out?

但如果你走得更遠呢？

What if you'd actually go farther from there?

如果你真的從那裡走得更遠呢？

Is there any magnetic field out in space itself?

在太空中是否有任何磁場？

Well, actually it turns out that there are,

好吧，事實上，事實證明，有的。

that our galaxy does have a magnetic field

我們的銀河系確實有一個磁場

as a whole too.

作為一個整體也是如此。

This magnetic field might be hard to detect.

這種磁場可能很難被發現。

You might need a very, very sensitive compass,

你可能需要一個非常、非常敏感的指南針。

but if say you had it,

但如果說你有了它。

you would actually see that our galaxy

你實際上會看到，我們的星系

does have sort of a magnetic north and south pole,

確實有一種南北極的磁性。

and that magnetic field permeates our whole galaxy.

而這個磁場貫穿了我們整個銀河系。

So, with compasses, you could actually at least find out

是以，有了羅盤，你實際上至少可以發現

where the north and south pole of another planet is,

另一個星球的南北兩極在哪裡。

the north and south pole of a star.

恆星的南北兩極。

A star has a magnetic field too.

一顆恆星也有一個磁場。

Even the north and south pole of a galaxy.

甚至一個星系的南北兩極。

So, if you were trying to navigate with a compass in space,

所以，如果你想在太空中用指南針導航。

just remember that compass is going to respond

請記住，羅盤會有反應

to the strongest and closest magnetic field.

到最強和最接近的磁場。

It will point north,

它將指向北方。

north to the pole of the planet.

北方到地球的極點。

North to the pole of star.

北方到星星的極點。

Even to the north and south magnetic poles of our galaxy.

甚至到我們銀河系的南北磁極。

But what you're reading is a magnetic field.

但你所讀的是一個磁場。

That's what a compass does.

這就是指南針的作用。

And that's pretty much all I can tell you.

這就是我可以告訴你的幾乎所有情況。

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