Ask an astronomer: What was Einstein’s most mind-blowing discovery?

Do space and time really exist? NASA astronomer Michelle Thaller looks at the implications of Einstein's famous equation E=mc2.

MICHELLE THALLER: If you were to convert my hand into pure energy using Einstein's equation you could have nuclear Armageddon on a global scale. There is so much mass in here that if you were to convert me into pure energy I could blow up the planet.

There are very few people in the world where I just simply say their name and you immediately can picture them, probably many different images of them, and one of them certainly is Einstein. I just say that word and all of a sudden you're thinking about crazy white hair and the mustache, somebody who is brilliant, you know, those wonderful unknowing eyes with lots of smile lines around them. Everybody knows who Einstein is and people understand that he was a very famous scientist, but I think that people often don't grasp the true depth and the profound nature of the things that Einstein introduced to us.

I also spend a lot of time debunking, in some ways, the myth of Albert Einstein. A lot of people seem to think that he was somebody that worked outside of traditional academics, he wasn't part of the academic establishment, he came up with all this brilliant stuff all by himself. Well, that wasn't true either. Einstein was a professor, he actually taught a lot at the University of Bern and also in Berlin and then eventually came to Princeton. He was very much a product of the time and the science that was going on. There were brilliant people at this time. Science was changing in so many different ways and for a lot of things Einstein found himself kind of in the right place at the right time to see two different things going on and say ah-ha, those things actually go together. And to me that really was some of the real brilliance of Einstein, was that he became a bridge between many, many different subject matters.

It amazes me that he was one of the people when he was doing his doctoral dissertation, who figured out the size and speed of molecules in the air all around you. People didn't realize at the time, when Einstein was a younger student in college, that air was made of molecules, little things that are constantly bouncing off each other and bouncing off of you and that's what we think of as air. And it became known that there was a tremendous number of these. To give you an idea, in about a square foot of air, if I had about a square foot of air of volume in front of me, how many molecules are in a square foot of air? The answer is approximately 10 to the 23, which means a one with 23 zeros after that. That's such a big number we don't have a name for it. And all of those molecules are bouncing off you at hundreds of miles an hour. Can you imagine when they realized that's what air really was? Einstein was a major figure in that and then there was so many other things he did.

But I think if I were to ask you, what is Einstein really known for? The thing that would pop into your head, even if you don't know what it means, is the equation E=mc2. So, this is something that I have to say takes my breath away in the implications of this. It is absolutely incredible. What it means is that energy, pure energy, is really the same thing as matter, as mass. When we talk about matter—I'm made of matter, I'm made of atoms and molecules, I'm a solid thing—what you're really talking about in many ways is the fact that I have mass. I have something that you can measure the gravity of. I'm a solid, substantive thing. And you think about energy—so maybe an example of pure energy could be a beam of light. A beam of light has no mass at all, there's no substance to it, it doesn't have a volume, it's just pure energy. E=mc2 is the bridge, and this is what Einstein was so brilliant at, bridging two very different parts of the universe all at once: the world of matter and the world of pure energy. 'C' in this equation represents the speed of light and the speed of light is a huge number. To give it to you just in some units you might be able to understand, the speed of light is 186,000 miles per second. So, that's how fast light travels through space, through empty space it would go about 186,000 miles every second. And that's a big number already and to square something means you multiply it by itself, so two times two equals four—you're squaring two. Four times four equals 16, you square that. Now think about squaring 186,000 and that's in the units of miles per second. That's a big number.

And so, think about the equation: M means mass, the amount of gravitational oomph we have, and E is energy. What that means literally is that what you are is some super intense almost kind of coagulated form of energy. If you were to convert just a little bit of my mass into pure energy you would have a tremendous amount of energy. And let me give you an example of how much that's true. The thing that in our experience can actually convert mass into energy is a nuclear bomb. A nuclear bomb these days we have very powerful ones called hydrogen bombs. In the case of the bomb that were first used on the city of Hiroshima in Japan, the amount of matter that was converted into pure energy, that killed 100,000 people and leveled a city, that was the equivalent to about a third of the mass of a dime. So, think about a dime coin, cut it in three; that's about how much mass blew up the entire city of Hiroshima. So, you can think about the fact that in my hand, if you were to convert my hand into pure energy using Einstein's equation, you could have nuclear Armageddon on a global scale. There is so much mass in here that if you were to convert me into pure energy I could blow up the planet. That's an amazing thing to think of, is that what you are is this somehow changed modified form of energy.

And by the way, you can go the other way too—you can actually turn energy into mass. And this is what we do in the particle accelerators all around the earth. I had the wonderful opportunity, and this was like being a kid in a candy store, I've actually gone to tour CERN, which is the largest particle collider in the world. It's in Switzerland and France. And CERN actually has this, I believe the circumference of the circle is about 26 kilometers—it is in Europe, you use kilometers—and it slams tiny particles together at very, very close to the speed of light. And in some cases they slam those particles into bigger, heavier atoms like gold nuclei or lead nuclei, but for a tiny amount of time, less than a trillionth of a second, they actually create conditions very, very close to what it was like a little bit after the Big Bang when the temperature of the universe was measured in trillions of degrees. And that is so much energy that it creates particles, it creates mass just from the pure energy of that collision. And that's how we discover new particles. Have you ever wondered why does the particle collider discover new particles? You get to bigger and bigger energies, you collide things faster and harder together and the more energy you can build up the more massive a thing you can make. So, you can find more massive particles the higher energy you juice this collider up to. And now, of course, we want to actually design the next generation of colliders; some of the things we're hoping to find are maybe things like a particle of dark matter. We now know the universe is made of this mysterious substance called dark matter but we have no idea what particle is associated with it. It may be that that particle is massive enough we haven't been able to build it yet.

One of the incredible things about these particle accelerators is that they use Einstein's equation backwards, they turn energy into mass. And once you get to a high enough energy, the universe can make anything it wants that has that amount of energy in its mass. So, that's the way we have found more and more exotic particles, the Higgs boson, different sorts of quarks and building blocks of atoms, all by getting to these higher and higher energies.

Okay, but here's the thing that really sort of keeps me up at night about the equation. Pure energy, like a photon, is very, very different from you and I. And one of the ways that it's very different is that it travels at the speed of light. A photon does not exist standing still, ever, in any part of the universe. A photon is always traveling at the speed of light; that's sort of the definition of its existence. And one of the amazing laws that Einstein found was that when you travel close to the speed of light, as you approach that speed time, according to your measurements of it, your sense of time slows down more and more. If you're going half the speed of light your time slows down quite noticeably. If you're going at the speed of light, time ceases to exist. To a photon, to the light, the light that's bouncing off my face right now, the reason you can see me is the light interacting with me and coming to your eyes, that light does not experience time and it did not experience the distance between the camera and my face. To a beam of light, the universe is a single point of space and time. It's almost as if to a beam of light the universe never expanded. All points of space and time collapse into one thing—and yet here we are as matter interacting with light; we have time, we have space, we are moving through time and space. I am made of pure energy and in a way I'm made of things that don't experience space and time in a very basic sense. And then something happens and all of a sudden there is gravity, there is time, there is matter, there is mass.

What actually is that transition? What makes something massless, timeless, no idea that there's a separation in space between objects? That blows my mind. How am I simultaneously energy and matter at the same time? And I think that once we really understand this we're going to be in for some very difficult truths to accept. It may be that there is no space or time as we know it, really. Everything that we know of as space and time is some kind of a projection, some kind of a way of viewing this single thing, this singularity that is the universe. If that's true, all points of space and time exist at once. What about my past and my future are all there, according to a beam of light. If we really understand this we may actually be sort of knocking at the door of what reality is and right now I have to say we have no idea what the nature of reality itself is. Maybe this will help us get a clue.

  • NASA astronomer and science communicator Michelle Thaller explains that the real brilliance of Albert Einstein is that he was able to bridge ideas that appeared to others to be in different realms.
  • The thing Einstein is most famous for is the equation E=mc2. Thaller explains why that equation is so mind-blowing: Pure energy and matter are the same thing. That means, as humans, we are both made of matter and of pure energy, and as pure energy, we would not experience space or time.
  • "I think that, once we really understand this, we're going to be in for some very difficult truths to accept," says Thaller. "It may be that there is no space or time as we know it, really."

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