Laboratory in Orbit: ISS Quiz

The ISS is essentially a "falling" object that never hits the ground. It travels at 17,500 mph. As gravity pulls it down, the Earth curves away beneath it at the same rate. This state of constant falling is called an orbit.

False. The ISS is an international partnership between five space agencies: NASA (USA), Roscosmos (Russia), ESA (Europe), JAXA (Japan), and CSA (Canada). Over 15 different countries contributed modules and parts.

"Microgravity" is the correct term. Gravity is actually still very strong at the ISS altitude (about 90% of Earth's surface gravity), but because the station and the astronauts are falling together, they feel weightless.

Because it travels so fast (5 miles per second), the ISS completes a full trip around the Earth in about an hour and a half. This means the crew sees 16 sunrises and sunsets in a single 24-hour day.

The ISS is mainly a research lab. Scientists study biology, physics, and medicine in microgravity. While a few tourists have visited, its main goal is science and preparing for deep space travel.

In microgravity, if you push a wall (action), the wall pushes you back with equal force (reaction). Astronauts use "handholds" to push and pull themselves around because their feet cannot provide traction on the floor.

True. If you include the massive solar arrays, the ISS is about 357 feet long. It is the largest human-made object currently in space and can even be seen from Earth with the naked eye.

The solar arrays convert sunlight into electricity. Since there is no weather or atmosphere in space to block the sun, these arrays are highly efficient, though they must be rotated to face the sun at all times.

Exercise is required to stop bone and muscle loss. The station also features a complex Water Recovery System. While there is no artificial gravity yet, communication with family helps keep the crew mentally healthy.

Cargo ships (like SpaceX Dragon or Russian Progress) must carefully match the speed and position of the ISS to dock. This is a delicate physics maneuver where two fast-moving objects become one.

False. The inside of the ISS is filled with a mixture of oxygen and nitrogen, just like Earth's atmosphere. Sound waves travel through this air easily. In fact, the station is quite noisy due to the many life-support fans.

The Cupola is the most popular spot on the station. Its windows face Earth, allowing astronauts to take photos, monitor arrivals of spacecraft, and see the planet's weather patterns from 250 miles up.

EVA stands for Extravehicular Activity. Astronauts wear pressurized suits that provide oxygen and protection from extreme temperatures (ranging from -250°F to +250°F) while they work in the vacuum of space.

Gyroscopes spin to maintain the station's orientation without using fuel. Small thrusters are used to "boost" the station's altitude because it occasionally drags against the very top of the atmosphere and slows down.

Without gravity to keep them in a bed, astronauts sleep in vertical bags attached to the wall. This keeps them from drifting into sensitive equipment or air vents during the night.

True. Since Expedition 1 in November 2000, there has never been a moment without humans living on the station. This makes it the longest-running human presence in space.

In microgravity, the brain gets confused because the inner ear doesn't feel a "down" pull. Astronauts use the station's lights (placed on the "ceiling") and labels on the walls to help stay oriented.

Returning to Earth involves "reentry." Friction between the fast-moving capsule and the air creates temperatures of 3,000°F. The heat shield is designed to burn away slowly, keeping the inside of the capsule cool.

The ISS is a "frictionless" environment. If you throw a ball, it will keep going in a straight line until it hits a wall. This makes it the perfect classroom to see $F=ma$ and other physics laws in action.

Built by Canada, this robotic arm is the "utility tool" of the ISS. It moves large modules into place and can "catch" visiting cargo ships that aren't able to dock on their own.