Things You Thought You Knew – Your Zodiac is Wrong

**Neil deGrasse Tyson** (0:00)
Hello, StarTalkians. Coming up, we've got another Things You Thought You Knew episode. This time, Chuck and I riff on Einsteinian time dilation, the mysterious gravity assist that space probes get, and the North Star. Spoiler alert, it's not all it's cracked up to be. Coming up on StarTalk.
Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.
I still lose sleep over this fact. Okay. I still lose sleep over it. And I want you to lose sleep too.

**SPEAKER_3** (0:47)
I don't want to be the only one staring at the ceiling at night.

**Chuck Nice** (0:50)
I'm going to tell you, a lot of things already beat you to that.

**SPEAKER_3** (0:55)
Oh, sure.

**Chuck Nice** (0:56)
I mean, the asteroid strike that could happen or the global warming or...

**Neil deGrasse Tyson** (1:01)
So here it is. You may remember or you may have heard that Einstein's relativity, more specifically, you learn this in special theory of relativity, where the faster you move, the slower time ticks for you, as others view it.

**Chuck Nice** (1:23)
Relative to the observer.

**Neil deGrasse Tyson** (1:25)
Relative to the observer, correct. You don't know anything's happening.
Your clock still ticks as far, you still got your heart beat, all of this. This is not a physiological thing. There's an actual property of the fabric of space and time under those conditions.

**Chuck Nice** (1:43)
Wow.

**Neil deGrasse Tyson** (1:44)
Okay.

**Chuck Nice** (1:45)
That is fascinating.

**Neil deGrasse Tyson** (1:46)
It is. It's completely fascinating. It's completely. So I watch you fly by, and the faster you go, the slower time ticks for you. Okay.

**Chuck Nice** (1:56)
But my time stays the same.

**Neil deGrasse Tyson** (1:59)
To you.

**Chuck Nice** (1:59)
To me.

**Neil deGrasse Tyson** (2:00)
To you. So not only does speed do this, also the strength of a gravitational field will have the same effect on you. The stronger the gravitational field is, the slower time ticks for you.
And that wasn't formulated until his general theory of relativity 10 years later. That took a lot more math and deeper insights into the universe.

**Chuck Nice** (2:22)
So once again, it makes sense because you're dealing with the fabric of space-time.

**Neil deGrasse Tyson** (2:26)
It's the fabric of space-time.

**Chuck Nice** (2:27)
Correct.

**Neil deGrasse Tyson** (2:28)
But initially, when formulated, you're thinking it's just because you're moving, but it's actually way deeper than that. And that's why that one, by the way, his original special theory of relativity was not called that.
The title of the research paper was On the Electrodynamics of Moving Bodies.

**Chuck Nice** (2:42)
What?

**Neil deGrasse Tyson** (2:43)
OK, that was the title. We would later call it the special theory of relativity because it was a special case of what would later then be called the general theory of relativity. OK, so the geosynchronous satellites are like middle orbit.
That is far enough away from Earth's source of gravity for them to have a different, a measurably different space time condition.

**Chuck Nice** (3:06)
Oh.

**Neil deGrasse Tyson** (3:07)
So that their clocks tick faster than our clocks on Earth's surface because they are farther away.
And so, remember I said the more intense, the gravitational, the slower time tick. So they're farther away. Their time ticks faster relative to us.

**Chuck Nice** (3:26)
Wow.

**Neil deGrasse Tyson** (3:27)
But we get precise timings from geosynchronous satellites.
So how does this work? We pre-correct the time signal from the GPS satellites to compensate for Einstein's general theory of relativity, so that by the time the time reaches us, it's been properly corrected and it matters to us and our space-time continuum, not the one that's in Middle Earth orbit.

**Chuck Nice** (3:55)
Oh my goodness.

**Neil deGrasse Tyson** (3:58)
So GPS couldn't work as accurately as it does.

**Chuck Nice** (4:01)
However, wait a minute, I'm sorry, just for me. You would have to have a standard in order to precorrect something.

**Neil deGrasse Tyson** (4:11)
You know the rate at which its time is speeding up, because you can calculate what the gravitational field is up there.

**Chuck Nice** (4:19)
There you go. There you go. Okay. Okay.

**Neil deGrasse Tyson** (4:21)
And once you calculate that, then you do and you say, oh my gosh, the formula works, Einstein was right.

**Chuck Nice** (4:29)
All right.

**Neil deGrasse Tyson** (4:29)
This is not just something on a few high theory, by the way, hypothesize that may or may not be true. It is true.

**Chuck Nice** (4:37)
I just want to be there when that phrase is uttered. Oh my God, Einstein was right.