Transcription
up until the 20th century.
Mhm. Mhm.
Everything that physics discovered about the universe that applied everywhere as far as we knew, right? They were called laws. Newton's laws of motion. Newton's laws of gravity.
Right.
Law is something that you don't break.
Okay.
It is a law.
That's right.
Thou shalt not go faster than light.
Thou shalt not. Those were the original tablets, if you're wondering.
No, that's the the other one that broke.
That's the one that broke off. I COME DOWN WITH THESE 15 10 11 to 15 with the speed of light.
So, beginning of the 20th century, we stopped calling them laws.
Okay. Why is that? It was a humble recognition that the experiments you do that establish the laws might not have been conducted in every possible extreme to test the law that you're establishing.
Mhm. That makes sense.
Okay.
Right.
Let me give a really stupid example. All right. I can make a law that if I drop something, it'll fall at a particular rate. I'll call that my gravity law.
Well, that kind of is the case.
Yeah. Yeah, it is. It is. It is. I'm not. However, if I go to a mountaintop, it'll fall slightly slower if I have very careful measurements. My gravity law is different at the top of a mountain.
So, I have to adjust it somehow. And then I learned, oh my gosh, my gravity law depends on how far away you are from the center of the earth.
Center of the earth. Okay.
Okay.
Cuz that's what it's falling into.
Oh, that's what it's falling into. But you have to, this is new understanding of what's going on, right? But if no one ever ascended a mountain, this law would work for everybody at all times at sea level, right?
Okay.
Yeah.
But so now let me give a more realistic example. Isaac Newton has his laws of motion, laws of gravity. They apply everywhere. The moon going around Earth, Earth going around the sun, Jupiter's satellites going around Jupiter. It's not just here's what the sun does with planets. It's what anything does that's got mass, right? If it's got mass, you can have gravity. You got this, right?
So, oh my gosh, this is amazing. But then Uranus gets discovered.
Mhm.
It's not following Newton's laws of gravity. Have we found the limits of this law? It only applies maybe to our solar system. Maybe other star systems it's different. Or maybe beyond a certain distance, the universe is somehow interfering with it. We didn't know, right? And we had Newton's boys on his side saying, "Not is so badass. We are sure the law still works. There must be some other planet tugging on it that you haven't put into your equations, right? Let's look for it." You have to invert the equation to find the thing that would be making the force of gravity. An inversion problem. Took some highle math in the day. Sure enough, they said, "Look here." Bada bing, there it is. Newton's law still helped.
Still help.
Now we keep going. How about these stars that orbit each other? Do we know their masses? Not quite yet. We have to learn more about what stars are. We get their masses. Whoa. They're following Newton's laws.
Wow. Right.
Stars. That's beyond our solar system. So, we were good with Newton's laws until we had to understand what Mercury was doing. Mercury, its orbit around the sun was not following Newton's laws.
We said we've been down that road before, right?
But there's a planet, right, inside the sun.
No, no.
There's another planet in the sun.
NO, MERCURY. THE NEXT BEST THING. There's a planet so close to the sun, we can't see it. It's lost in the glare, but clearly it's there.
Clearly, it's there.
Okay, because that would account for the fact that Mercury's path is not exactly following Newton's laws, right? Turns out, can't explain it with Newton's laws. We're in the presence of severe force of gravity, the sun. Obviously, Earth is near the sun. we're orbiting it. But these effects don't show up until you're really close. And Mercury is really close to the sun and a whole other understanding of physics needed to be invoked. Einstein's general theory of relativity.
Enter Einstein.
Enter Einstein, which accounts for very high sources of gravity, very high speeds. So you you invoke Einstein. Mercury is bang on exactly as it should be behaving. Do we throw out Newton?
YES.
NO. NO. NEWTON.
Get out Newton, you dumbass.
Get out of here.
Newton got us to that doorstep.
Right. Took us as far as we could go.
And according to Newton's laws of motion, if I'm going 2/3 the speed of light, Mhm. and you're going 2/3 the speed of light and we pass each other, how fast are we going relative to each other?
Half the speed of light. No. No. One. one in Newtonian way it would be one and a third. So two3 adding them.
Because I'm going fast, you're going fast, but we're passing.
Yeah. A simpler way to do it is I'm going the speed of light, you're going the speed of light, you're passing twice the speed of light. Okay.
That's it.
No, it doesn't work that way.
No.
Okay. Because the speed of light.
Can't do it, right?
The speed of light sets a limit unknown to Newton. Unknown, right? That there should be any such limit at all because he never dealt with anything going faster than running horses or just planets in orbit around their stars.
Okay.
They're not going fast enough to manifest that failure of Newton's laws.
Okay, you take.
Interesting. Einstein.
I love the way you put this.
Special. Well, no, it it's like people who work out and they say work out to fail. Like in other words, you push the weight as far as you can until you just can't lift it anymore and that's the point of failure. You can lift that. You could, but you get to a point where yeah, this doesn't work anymore.
You've tested the limits of the limits of your muscle. So now you're in a new world now.
Are you going to get there or you not? You maybe you need a different regimen, right?
To get there.
Exactly.
That's very cool. Einstein's general theory of relativity and special theory of relativity combined accommodated the extremes where Newton's laws had never explored. This was a humble recognition that that which we used to call a law had limits.
Yes.
You can't call things laws going forward, right?
Because the next thing might also have limits, right?
So, let's be humble about this. And so Einstein's theories of relativity are called his theory of relativity. So out of a point of historical perspective, we still call them Newton's laws.
Okay.
Just that's an historical artifact.
Like an homage.
An homage. Yes. Yes. But entering the 20th century where these laws of 19th century classical physics fell at their limits, we said we're not going to make that mistake again.
Okay. So here's what's important. If you take Einstein's relativity, plug in low speeds and low gravity, they become Newton's laws. So Einstein's laws did not replace Newton.
They extended them.
That's pretty wild.
That's how science works. Newton's laws don't all of a sudden not work. They're not supplanted or erased in the realm in which they had been experimentally tested and verified. That's still true.
So they still work.
The Apollo program, we went to the moon on Newton's laws. There was no Einstein in any of those equations.
Right?
Come the 1920s, we are recording this in 2026. We are in the centennial decade of the discovery of quantum physics. In the day, we called it quantum mechanics. That extends classical mechanics into the realm of particles and nuclei and the like.
Okay. Still call it quantum theory even though every experiment ever suggested by it has verified its predictions.
Oh, okay.
It is as much a law as we have ever measured anything to be.
We still call it quantum theory.
Because at some point there's a failure.
We haven't gotten there. We haven't gotten there yet.
But we know at some point.
We don't know.
Well, we don't know. We can allow for it.
Allow for that possibility. People think a theory scientifically is just some idea you happen to have that's not yet verified. Yes. Nothing could be farther from the truth. Yeah. In in in physics.
Because they think it's a murder mystery. Just like I have a theory.
Okay. So when people say I have a theory, right?
You know what my reply is?
What?
I say Einstein had a theory. You have a hypothesis.
Right? And guess what? You don't even have that cuz that's a cuz that's an educated guess.
Okay. You know what you got? You got an idea. A thought.
You have a thought.
That's what you have. A thought. So the difference is a theory as we now use the term and have been using it for 100 years now.
Okay.
Is an organizing understanding of how the universe works in some realm or another. It not only organizes it. It says we understand this that that and the other because of this idea. And not only that, this idea is so fertile. I can make predictions on it. You can go test it and those predictions will show up and be correct.
That makes sense. And especially because it eliminates the perception that a theory is a thought or an idea like oh. That's why I whenever I get the occasion I say you don't have a theory. Einstein had a theory. You have an hypothesis, right?
You You hypothesize.
Something, right?
You It's not Nothing works yet. It hasn't been tested yet.
Okay. Right.
I have a hypothesis. Can we test it? Yeah. Here's an idea. Test it. We test it. Did it? Yeah. Okay. That's good. Hold on to that.
Right.
Is there more testing? Is there more understanding that this will give us as this builds? You achieve the level of a theory.
Gotcha. Yeah. Okay. So we have quantum field theory, theory of relativity. We have the theory of evolution, right?
Nothing makes sense in biology without evolution by natural selection.
And by natural selection, we mean God decided to like I'm going to select you and I'm going to select you and I'm going to select you and.
That's divine selection.
That's divine selection. Okay. So evolutionary theory for example would say if you understand that mammals came later in the tree of life, uh, you know, we didn't really become interesting mammals till after the dinosaurs, the big dinosaurs left the scene. I think there were some early mammals, but if you go back millions of years before the dinosaurs and there's a sedimentary layer with dinosaur fossils, evolutionary theory predicts you will not find mammals in that layer. If you find a layer that has dinosaurs and rabbits, that's a problem for the theory of evolution.
It's also a hoax.
So, you have to ask, is it a hoax?
Because evolution has been so thoroughly tested, right?
Is it a hoax? Is there some uplifting of the surface which happens in continental drift? So, check for that, right? You want because it's been so successful. Your first thought is, "No, let me throw the whole thing out the window because of this one data point" because it's been so successful. That would put a theory to the test.
Right.
Now, Copernicus had a theory, the heliocentric theory, that the sun is in the middle of the known universe, not the Earth. He came up with this. It was like, whoa, brilliant Copernicus. He's right. Sun is in the middle of things, right? But his orbits were perfect circles. He's religious like everybody else. If God made the universe, what's the most perfect shape? Circle. So, he made the universe. Give give the boy circles. And it didn't match the paths of the planets in the sky. How could this be a correct theory if it's getting that wrong? So, here's what happens.
The Lord works in mysterious ways.
That's that's one answer. Another one is maybe I have to adjust my theory. Maybe the basics are correct, but I got to make an adjustment on the edges. What is that adjustment? We would learn 70 years later they're not perfect circles. They're slightly squashed circles. Ellipses.
Once you put an ellipses, it's bang on. Just because you find something that tickles the edge of a theory, right? That alone does not mean you're going to throw the theory out. If the theory has a lot of supportive experimental evidence, take the Big Bang. I cannot begin to list for you the supportive evidence for the Big Bang. Even though it makes no sense that the whole universe was once smaller than a marble. What's What's my saying?
The universe is under no obligation to make sense to you.
Thank you.
Right.
Thank you.
And I have a response to that. F you universe. You're going to make sense to me whether you like it or not.
That's right. I want to make you make sense. Don't make me make you make sense to me. So, so right now they're measurements of the Hubble constant that don't agree with each other.
Okay.
The Hubble constant is like the expansion rate of the universe. What's up with that, right? Headlines all over the place. We have to revisit the big bang, the big bang this. We have to Okay, excuse me. No, this is like an edge effect. If we have to redo the big bang, it's going to take more than that. This is one thing. Let's keep exploring it because so much else works. If you have another idea that can explain the Hubble constant, you have to explain all this other stuff, too.
Right.
And that's hard. Be my guest. But just don't turn around and say, "I found this one thing that conflicts. Therefore, all of it's wrong."
All of it's wrong.
That's called the baby with the bath water.
Exactly.
Exactly. In Copernicus, the baby was right there. The sun was in the middle. You're not throwing that out.
Right.
Cuz it explains so many other things. Yeah.
Okay. Yeah.
All right. So theories are powerful ideas that have been experimentally verified and we ought to be calling them laws, but we don't because we're humble and we're going to say one day we might find a deeper idea in which this theory is embedded that gives us a deeper understanding of how the universe works.
Right? But whatever that new theory is that supplants it, it doesn't push it to the side because there it's experimentally verified. It will enclose it as a special case of the deeper understanding of nature.
Nice. to say, and this was spoken in the halls of Congress, we should teach evolution as the theory that it is and make sure that we can also teach biblical creation because evolution is just a theory. That is a profound misunderstanding of what theories are and how and why they work. As our understanding grows deeper, so does the nesting doll of the prior understandings and how they manifest in the world that we explore.
Pretty cool, man. I love it.
That's it, Chuck.
That's it.
We good on that?
Yeah, we are. Uh takeaway, all your theories are wrong.
Cuz they're hypothesis.
Hypothesis. You don't have one.
This has been another Star Talk explainer. Chuck, always good to have you here. Love your feedback. Neil deGrasse Tyson, your personal astrophysicist. Do keep looking up.