About Space Facts
Space can seem impossibly huge, but a few key ideas help make sense of it. Distances are enormous, light takes time to travel, gravity shapes everything from moons to galaxies, and even the emptiest regions still contain particles and radiation.
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Looking Far Away Means Looking Back in Time
Light does not travel instantly.
Learn MoreAstronauts Are Still Under Earth's Gravity
The International Space Station is not beyond Earth's gravity.
Learn MoreSpace Is Not Completely Empty
Even deep space contains matter and radiation.
Learn MoreOrdinary Sound Cannot Travel Through Empty Space
Sound waves need matter to carry vibrations.
Learn MoreBlack Holes Do Not Suck Everything in the Universe Toward Them
At a distance, a black hole's gravity behaves like the gravity of any object with the same mass.
Learn MoreWater Is Common in the Solar System
Earth is not the only place with water.
Learn MoreMost Stars Are Not Like the Sun
Red dwarfs are the most common type of star in the Milky Way.
Learn MoreA Tiny Patch of Sky Can Hold Thousands of Galaxies
Deep-field images reveal how crowded the distant universe is.
Learn MoreApollo Footprints Can Last an Extremely Long Time
The Moon has almost no atmosphere or liquid water to erase tracks.
Learn MoreYou Are Made of Ancient Star Material
Many elements in living things formed inside stars or stellar explosions.
Learn MoreLooking Far Away Means Looking Back in Time
Sunlight takes about eight minutes to reach Earth. Light from the nearest star system beyond the Sun takes more than four years. When telescopes observe galaxies billions of light-years away, they see those galaxies as they existed billions of years in the past.
Astronauts Are Still Under Earth's Gravity
Gravity at the station's altitude is still strong. Astronauts float because the station and everything inside it are continuously falling around Earth. Their sideways orbital speed keeps them from hitting the ground.
Space Is Not Completely Empty
The density can be incredibly low, but atoms, dust grains, energetic particles, magnetic fields, photons, neutrinos, and other forms of energy travel through space. The vacuum between stars is far emptier than anything naturally found on Earth.
Ordinary Sound Cannot Travel Through Empty Space
In a near vacuum, there are too few particles to transmit ordinary sound from one spacecraft to another. Astronauts communicate by radio, which uses electromagnetic waves that can travel through a vacuum.
Black Holes Do Not Suck Everything in the Universe Toward Them
If the Sun were magically replaced by a black hole of the same mass, Earth would continue orbiting at roughly the same distance. The danger becomes extreme only when an object gets very close to the black hole.
Water Is Common in the Solar System
Water ice exists on the Moon, Mars, comets, asteroids, and many outer Solar System moons. Europa and Enceladus probably contain global or regional subsurface oceans, and Ganymede may contain enormous amounts of water beneath layers of ice.
Most Stars Are Not Like the Sun
Red dwarfs are smaller, cooler, and dimmer than the Sun. They burn fuel so slowly that some could remain active for trillions of years, far longer than the current age of the universe.
A Tiny Patch of Sky Can Hold Thousands of Galaxies
Webb and Hubble can stare at small areas of sky and detect thousands of galaxies. Each galaxy can contain billions of stars, showing how enormous the observable universe really is.
Apollo Footprints Can Last an Extremely Long Time
Micrometeorite impacts slowly disturb lunar soil, but there is no ordinary wind or rain. Human bootprints, rover tracks, and equipment from Apollo missions can remain recognizable for very long periods.
You Are Made of Ancient Star Material
Hydrogen is extremely old, but carbon, oxygen, calcium, iron, and many heavier elements were produced by earlier generations of stars and violent cosmic events. The material that became Earth was already enriched by this long stellar history.