Janna Levin

And he said, well, I bet something must be wrong then with space and time. So this is an enormous leap. He's willing to give up the absolute character of space and time in favor of keeping the speed of light constant.

I'll tell you, it took me, I think, a long time to... I can't say this is how he got there exactly. It's not as though I studied the historical accounts or his description of his internal states. This is more... having learned the subject, how I try to tell people how to get there in a few short steps.

I'll tell you, it took me, I think, a long time to... I can't say this is how he got there exactly. It's not as though I studied the historical accounts or his description of his internal states. This is more... having learned the subject, how I try to tell people how to get there in a few short steps.

I'll tell you, it took me, I think, a long time to... I can't say this is how he got there exactly. It's not as though I studied the historical accounts or his description of his internal states. This is more... having learned the subject, how I try to tell people how to get there in a few short steps.

One is to start with the equivalence principle, which he called the happiest thought of his life. And the equivalence principle comes pretty early on in his thinking. And it starts with something like this. Like right now, I think I'm feeling gravity because I'm sitting in this chair and I feel the pressure of the chair and it's stopping me from falling. And

One is to start with the equivalence principle, which he called the happiest thought of his life. And the equivalence principle comes pretty early on in his thinking. And it starts with something like this. Like right now, I think I'm feeling gravity because I'm sitting in this chair and I feel the pressure of the chair and it's stopping me from falling. And

One is to start with the equivalence principle, which he called the happiest thought of his life. And the equivalence principle comes pretty early on in his thinking. And it starts with something like this. Like right now, I think I'm feeling gravity because I'm sitting in this chair and I feel the pressure of the chair and it's stopping me from falling. And

I lie down in a bed and I feel heavy on the bed and I think of that as gravity. Einstein has a beautiful ability to remove all of these extraneous factors, including atoms. So let's imagine instead that you're in an elevator and you feel heavy on your feet because the floor of the elevator is resisting your fall. But I want to remove the elevator.

I lie down in a bed and I feel heavy on the bed and I think of that as gravity. Einstein has a beautiful ability to remove all of these extraneous factors, including atoms. So let's imagine instead that you're in an elevator and you feel heavy on your feet because the floor of the elevator is resisting your fall. But I want to remove the elevator.

I lie down in a bed and I feel heavy on the bed and I think of that as gravity. Einstein has a beautiful ability to remove all of these extraneous factors, including atoms. So let's imagine instead that you're in an elevator and you feel heavy on your feet because the floor of the elevator is resisting your fall. But I want to remove the elevator.

What does the elevator have to do with fundamental properties of gravity? So I cut the cable. Now I'm falling, but the elevator is falling at the same rate as me. So now I'm floating in the elevator. And if this happened to me, if I woke up in this state of falling or floating in the elevator, I might not know if I was in empty space, just floating, or if I was falling around the earth.

What does the elevator have to do with fundamental properties of gravity? So I cut the cable. Now I'm falling, but the elevator is falling at the same rate as me. So now I'm floating in the elevator. And if this happened to me, if I woke up in this state of falling or floating in the elevator, I might not know if I was in empty space, just floating, or if I was falling around the earth.

What does the elevator have to do with fundamental properties of gravity? So I cut the cable. Now I'm falling, but the elevator is falling at the same rate as me. So now I'm floating in the elevator. And if this happened to me, if I woke up in this state of falling or floating in the elevator, I might not know if I was in empty space, just floating, or if I was falling around the earth.

They're equivalent situations. I would not be able to tell the difference. Actually, when I get rid of the elevator in this way by cutting the cable, I'm actually experiencing weightlessness. And that weightlessness is the purest experience of gravity. And so this idea of falling is actually fundamental. It's how we talk about it all the time. The earth is in a free fall around the sun.

They're equivalent situations. I would not be able to tell the difference. Actually, when I get rid of the elevator in this way by cutting the cable, I'm actually experiencing weightlessness. And that weightlessness is the purest experience of gravity. And so this idea of falling is actually fundamental. It's how we talk about it all the time. The earth is in a free fall around the sun.

They're equivalent situations. I would not be able to tell the difference. Actually, when I get rid of the elevator in this way by cutting the cable, I'm actually experiencing weightlessness. And that weightlessness is the purest experience of gravity. And so this idea of falling is actually fundamental. It's how we talk about it all the time. The earth is in a free fall around the sun.

It's actually falling. It's not firing engines, right? It's just falling all the time, but it's just cruising so fast.

It's actually falling. It's not firing engines, right? It's just falling all the time, but it's just cruising so fast.

It's actually falling. It's not firing engines, right? It's just falling all the time, but it's just cruising so fast.

To be falling. That is the purest experience of gravity. The experience of gravity, unfettered, uninterrupted by atoms, is weightlessness. That observation, no, it has an unhappy ending, the elevator story, because of atoms again. That's the fault of the atoms in your body interacting electromagnetically with the crust of the earth or the bottom of the building or whatever it is.