TEDxUCLA 2017: Gravity

Space travel is human travel


About Dana

Ph.D., Mechanical Engineering, Stanford University, 2006 M.S., Mechanical Engineering, Stanford University, 2002 B.S., Mechanical Engineering, Georgia Institute of Technology, 1999 Dana Carpenter is an Assistant Professor of Mechanical Engineering at the University of Colorado Denver. His research focuses on the effects of mechanical forces, exercise, diseases, and implanted devices on the human skeleton.


When I was a kid, I was just completely enraptured with the idea of space travel. I loved Star Wars. I loved all the cool starships travelling from one planet to another. Loved it. It made me wish that someday I could travel to places that were new and exciting and maybe sometimes even a little scary.

I loved the idea of astronauts floating around in their spaceships, able to see entire continents at once. There was just something inside me that wanted to explore and to be amazed. It’s who I am.

When I was 13, I got to go to Space Camp. As you could probably imagine, I was thrilled. I learned a ton about the realities of space travel, the history of humans in space, and what it’s like to live without gravity.

Now I’m all grown up. I still love Star Wars. And I’m still fascinated by the idea of space travel.

I’m a college professor, and my research focuses on understanding the mechanical effects of things like medical implants, diseases, and exercise on the human skeleton. I have a lab filled with students working on all kinds of wonderful things, and one thing that I’m really personally interested in is understanding what happens to the human body when we live without gravity.

What I’ve come to realize is that ever since we launched the first rocket into space we’ve been struggling with the problem of gravity. To get to space, you have to escape from gravity. And once you’re there you have to deal with life without gravity.

What if, instead of fighting with gravity we embraced it? What if we could pack it up in our suitcase and take it with us on our trip?

From the moment we’re born, our lives and our bodies are shaped by gravity. It affects how our blood is pumped through our bodies. It guides our bones to grow into complex shapes. Through millions of years of evolution, gravity has molded the human body into what it is today. It permeates us down to the level of individual cells. It’s part of who we are. And you can’t ignore who you are.

If we could just bring gravity with us when we go into space, it would solve all kinds of problems that happen in the human body. For example, in space you get taller. Well hey, I’m 5’8″ on my tiptoes. Where do I sign up?

But maybe it’s not such a good thing. People get taller in space because they’re intervertebral discs, the little cushions between each of the bones in your spinal column, expand when the force of gravity is removed and you get taller.

The downside is back pain. Over half of the astronauts on the International Space Station report problems with back pain. We think the pain is caused by a combination of the expanding discs and a loss of muscle tissue that supports the spine.

If you want your muscles to get strong, you work out, right? Well the muscles that you use to stand up and walk around get exercise all day long as you move around the world under the force of gravity. Escape from gravity and all of a sudden those muscles aren’t getting exercised very much anymore. They get smaller and they get weaker.

Astronauts lose bone is space, too. Lots of it. Our bones are like our muscles: you have to use them if you want them to stay strong. And if you don’t use them, they start to go away, especially in weight-bearing locations like the hips. They get more fragile and easier to break. The last thing you want to do is make it all the way to Mars and then break a hip stepping off the lander.

And there are all kinds of other changes that happen in the body. Some of them might be a little more unexpected. For example, when astronauts go to space, their eyeballs change shape. John Phillips, an astronaut with 20/20 vision, came back from the space station with 20/100 vision. That means that when he left he could see perfectly, and when he got home he was nearsighted.

About 80 percent of crew members on the Space Station experience altered vision. We think this change is due to a redistribution of fluid in the body. Since gravity is not pushing it down anymore, more fluid winds up in the head, pushes on the backs of your eyeballs, and changes their shape.

The root of the problem here is that our machine technology, our ability to build spacecraft that can travel enormous distances, has outpaced our medical technology. So what can we do about all these problems?

Well the way I see it, we have two options. The first option is what I call the medical or biological strategy. NASA’s Human Research Program is developing an entire battery of countermeasures for this: better exercise equipment, nutritional supplements, even osteoporosis drugs seem to be doing a good job of reducing the changes that happen in the skeleton and the muscles. For the problem with the changing eye shape, one suggestion has been a small implantable device that would drain the excess fluid from the head down to the body.

In science fiction movies, a lot of times you see people put into some kind of suspended animation. Maybe we’ll get there someday. But to do that, we’re going to have to understand all of these different underlying biological mechanisms and figure out ways to put them all on hold. Essentially what I’m saying is there are a hundred different problems, and we can do our best to try to address them with 100 different solutions.

The second option is to solve all those problems with one solution: replace gravity. If we can just replace gravity or at least simulate it effectively enough, we could cure all those problems at once. But how do we do it?

In films like 2001: A Space Odyssey and more recently The Martian, there are spaceships that revolve and spin around to simulate the effects of gravity. We don’t have a ship like that. Not yet. But with the rise of commercial space travel — SpaceX, Virgin Galactic, Boeing, and other companies — maybe a ship like that’s not too far away.

It could work. It would pull on every cell in your body, just like gravity. I think right now it’s our best bet. But maybe, just maybe there’s another solution just outside our grasp.

Understanding physics to the point where we can recreate the force of gravity and put it to good use. Physicists can explain the theory of how gravity works, but what we need is a practical understanding of how to package it up and take it with us.

So far we have the power to observe gravity but we can’t control it. Think about lightning. For thousands of years, people saw lightning bolts shooting out of the sky and they were amazed, and I’m sure sometimes they were terrified. They could observe electricity, but they couldn’t control it.

Just think of the massive impact it had on our world once we figured out how to control electricity and use it to our advantage. We need to do the same thing with gravity.

Well the good news is we can make it to Mars and back with the current medical strategy. For a trip to the surface of Mars and back you’re looking at a trip that would be one-and-a-half, maybe two years long. We’re going to be asking people to deal with changes that will alter their bodies permanently, but people will still do it.

How about this: if you would still like to go on a trip to Mars after everything I’ve told you, give a little applause. (applause) We’re going to need a bigger ship!


But if we’re going to go further, deeper into the solar system or beyond, we are going to have to change our way of thinking. What if we embraced our limitations instead of trying to escape from them? We need to work with gravity to make the science fiction fantasy of space travel a reality.

We don’t have to accept the idea that escaping gravity is the only way. To be one of the main reasons for human space travel in the first place is to learn more about who we are. To learn who we are, we have to be who we are. We are human beings, and we need gravity.

When we go into space we bring air with us, we bring water with us, we bring food with us. Let’s bring gravity with us, too. Thank you.