Quantum Gravity

How does gravity work?
Answered by Dr. Astro Teller and Dr. Michio Kaku

• ### Dr. Michio Kaku

1. Dr. Astro Teller Director of New Projects, Google

TRANSCRIPT:

People don't fully understand gravity and I think that is actually pretty wonderful.  There is a lot of math around how gravity works, and I'm obviously not a physicist, but there are basic things that we do know about gravity.  Gravity is defined by matter -- that is kind of cool; and, in fact, space is defined by matter. So if you have no stuff, there is no concept of there being a place without the stuff; and that stuff, not only defines the space, but it defines the shape of the space. That concept is, in fact, very related to gravity.  Larger massed things pull us harder than smaller massed things; things that are far away pull us less hard than things that are close to us.

One of my favorite things about gravity is that if you are outside a big body and it is pulling you toward it, the shape of that body doesn't matter. The body has a “center of mass,” and we can pretend that the center is a little point, pulling us toward it. But if I took that big body and I just ripped off a hunk of this planet and stuck it over here, as long as I did that in a clever way so that the center of mass is in the same place, it would pull you in identically the same way.  I love things like that about the universe.

2. Dr. Michio Kaku Theoretical Physicist and Author

TRANSCRIPT:

Shakespeare once said that the world is a stage and we are actors and actresses making our entrances and exits. That picture was adopted by Newton. Newton said, "Yes, the universe is a stage. Space and time are a stage, and we are actors and actresses making our entrances." Then Einstein comes along and says," Not so fast. If the stage is curved and you were to walk along the curved stage, you would feel a force -- a force, which tugs on you left and right." That's gravity. Gravity is nothing but the effect of the curvature of the stage of life.

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• ## How is G-force calculated?

### Answered by Discovery Channel

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