# Gravity

## A force of attraction between things that have mass and how it relates to weight.

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Practice Gravity

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Space Poop

### Space Poop

Credit: Lindsey Turner
Source: http://www.flickr.com/photos/theogeo/3159051622/

Everyone knows what a toilet is for and how to use it—on Earth. But what if you’re in space where everything is weightless? Did you ever think about the problems involved in pooping in space?

#### The Back Story

• On Earth, everything falls down because of gravity. Earth’s gravity pulls all objects—including poop—toward the center of the planet.
• When you sit on a toilet and “deposit” waste, gravity pulls it down into the toilet bowl. No problem.
• But what if you were sitting on a toilet in the weightlessness of the International Space Station (ISS)? Imagine what would happen to the poop then.
• Credit: Erik Fitzpatrick
Source: https://www.flickr.com/photos/22244945@N00/3715390097

Toilets built for space look nothing like the toilets built for earth [Figure2]

• Canadian astronaut Chris Hadfield discusses this problem in the video below. He also explains how space toilets work to solve the problem.

#### Can You Apply It?

1. Why does the International Space Station (ISS) orbit Earth?
2. Why doesn’t gravity pull the ISS and its occupants down to Earth?
3. Astronauts aboard the ISS are subject to gravity, yet they are weightless. They literally float around in the space station (and so would their poop if it wasn’t sucked into the toilets on board.) How can astronauts be weightless while experiencing Earth’s gravity?
4. How is riding a roller coaster like orbiting Earth on the ISS?

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