What time is it on Voyager 1? 🤔

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0:00- What's the farthest manmade object from Earth?

0:02It's a space probe called Voyager 1

0:05launched by NASA in 1977.

0:07It's zooming away at 17 kilometers per second

0:10and is now more than 25 billion kilometers away.

0:13But what's weird is that the clock on Voyager 1

0:15reads a different time than ours.

0:18That's thanks to something our friend Albert Einstein

0:20figured out.

0:21His theory of special relativity

0:22showed that time passes slower for clocks

0:24when they're moving.

0:25It sounds crazy, but scientists have demonstrated this

0:28effect over and over.

0:29We actually have to account for how time passes differently

0:32on GPS satellites orbiting the Earth

0:34in order to track our location accurately.

0:36Okay, so Voyager 1's been traveling

0:38for a little over 48 years

0:40at around 17 kilometers per second.

0:42According to Einstein's equations for special relativity,

0:45Voyager's clock has lost about two

0:48and a half seconds since it launched,

0:49but Einstein gave us another mind bending lesson

0:52to consider, his theory of general relativity.

0:54In addition to time being stretched for moving objects,

0:57time is also warped by gravity.

0:59When you're close to a massive object like a planet

1:01or a black hole, your clock will tick a tiny bit slower

1:05than if you're far away from it.

1:06Our GPS satellites have to account for this effect too.

1:09And since Voyager 1 is now more than 25 billion kilometers

1:12from Earth, it obviously feels the gravitational pull

1:14of our planet much less than we do.

1:16That difference from Earth's gravity means Voyager's clock

1:18will actually tick about a second

1:20faster than an Earth clock.

1:21And if you combine both of these time dilation effects,

1:24Voyager's clock should be about a second

1:26and a half behind ours.

1:27But it gets even weirder

1:29because Earth is moving really fast too.

1:31In fact, the Earth's velocity

1:32around the sun is even faster than Voyager

1:35zooming through space.

1:36Plus, we're much closer to the giant heavy sun

1:38than Voyager is.

1:39So our clock is slowed even further by its gravity.

1:42If you do all these calculations relative

1:43to a point at the center of our solar system,

1:45factoring in the speed of Voyager,

1:47the differences in gravity

1:48and the speed of spaceship Earth,

1:50the clock on Voyager is actually somewhere

1:52around 20 seconds ahead of ours on Earth.

1:55Woo. So what time is it really on Voyager 1?

1:59Well, it could be the future or the past.

2:01Just depends on where you sit.

2:03Follow me for more cool science videos.

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What time is it on Voyager 1? 🤔

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