Space Exploration

Frequently Asked Questions

Have a question about space exploration? You are in good company. Below you will find answers to the questions we hear most often from curious visitors, covering everything from the basics of how spaceflight works, to the technology behind missions to Mars, the science of black holes, and what it takes for humans to live and work aboard the International Space Station. Click any question to reveal its answer, and click it again to hide the answer. The plus icon means the answer is hidden; the minus icon means it is currently visible.

If you have a question we have not covered here, head over to our Feedback page and let us know. We are always expanding this list based on what our community is curious about.

What is space exploration and why does it matter?

Space exploration is the use of astronomy and space technology to investigate outer space, both with uncrewed robotic probes and with human spaceflight. It matters because it drives advances in science, engineering, communications, medicine, and materials, and it deepens our understanding of where Earth fits in the wider universe.

When did human space exploration officially begin?

The Space Age began on October 4, 1957, when the Soviet Union launched Sputnik 1, the first artificial satellite. Human spaceflight followed on April 12, 1961, when Soviet cosmonaut Yuri Gagarin became the first person to orbit Earth aboard Vostok 1. The United States landed the first humans on the Moon with Apollo 11 in July 1969.

What is the International Space Station and who operates it?

The International Space Station (ISS) is a modular research laboratory in low Earth orbit, roughly 250 miles above the planet. It is a joint project of five space agencies: NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada). The ISS has been continuously occupied by rotating crews for more than two decades.

Why does my weight change on other planets?

Your mass stays the same wherever you go, but your weight is the force of gravity acting on that mass. Each planet has a different gravitational pull based on its mass and radius, so the same person weighs about 38% of their Earth weight on Mars and roughly 2.5 times their Earth weight on Jupiter. Try our Weight Calculator to see your Mars weight.

How long does it take to travel to Mars?

A one-way trip to Mars currently takes about 6 to 9 months, depending on the launch window and the relative positions of Earth and Mars in their orbits. Mission planners use a Hohmann transfer orbit to launch when the two planets are aligned efficiently, an event that happens roughly every 26 months.

What is a black hole, and can it really trap light?

A black hole is a region of spacetime where gravity is so strong that nothing, not even light, can escape once it crosses the boundary called the event horizon. Black holes form when massive stars collapse at the end of their lives. The first direct image of a black hole's shadow, at the center of galaxy M87, was released by the Event Horizon Telescope team in 2019.

What are exoplanets, and how do scientists find them?

Exoplanets are planets orbiting stars other than our Sun. Astronomers most often detect them with the transit method, watching for tiny dips in a star's brightness as a planet passes in front of it, and the radial velocity method, measuring the small wobble a planet causes in its host star. More than 5,000 exoplanets have been confirmed to date.

How do astronauts experience life in microgravity?

In orbit, astronauts and their spacecraft are in continuous freefall around Earth, which produces the sensation of weightlessness called microgravity. Daily tasks like eating, sleeping, and exercising all require special equipment. Crews must work out about two hours every day on resistance and cardio machines to slow the bone and muscle loss that microgravity causes.

What is the difference between a meteor, a meteoroid, and a meteorite?

A meteoroid is a small chunk of rock or metal traveling through space. When that object enters Earth's atmosphere and burns up as a streak of light, the visible event is called a meteor (or "shooting star"). If any piece survives the trip and lands on the ground, the surviving fragment is a meteorite.

What role do private companies like SpaceX play in modern space travel?

Private companies have shifted much of the routine launch and cargo business away from government agencies. SpaceX, Blue Origin, Rocket Lab, and others now deliver satellites, supply the ISS, and fly astronauts under contract with NASA. Reusable rockets, pioneered by SpaceX with the Falcon 9, have driven launch costs down dramatically and opened space to a much wider range of customers.

Will humans ever live permanently on the Moon or Mars?

Both NASA's Artemis program and several private initiatives aim to establish a long-term human presence on the Moon within this decade, with Mars as a longer-term goal. Permanent settlement faces serious challenges, including radiation exposure, life support, food production, and the psychological effects of isolation, but research on the ISS and on Earth-based analog sites is steadily working through them.

How do telescopes like Hubble and James Webb actually work?

Both telescopes orbit far above Earth's atmosphere, which would otherwise blur and absorb much of the incoming light. Hubble, launched in 1990, observes mainly in visible and ultraviolet light using a 2.4-meter mirror. James Webb, launched in December 2021, uses a much larger 6.5-meter segmented mirror and observes in the infrared, which lets it see through dust clouds and look at very distant, very early galaxies.