The most mind-blowing space facts
The top 3 according to 41 votes from people: Moon footprints can last millions of years · A year on Neptune lasts 165 Earth years · The Moon drifts about 3.8 cm away from Earth each year. (Updated Sep 21, 2026.)
Real facts about the solar system and the universe, among the most repeated in popular science (NASA and astronomy sites). Vote for the one that surprises you most.
Automatically translated (original in Español). See the original
Top 20
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1
Moon footprints can last millions of years
With no wind or water to erase them, the Apollo 11 footprints (1969) will stay there for an immensely long time.
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2
A year on Neptune lasts 165 Earth years
Since its discovery in 1846 it has completed just one orbit of the Sun, in 2011.
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3
The Moon drifts about 3.8 cm away from Earth each year
Measured with lasers bounced off the mirrors left by the Apollo missions.
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4
Sunlight takes about 8 minutes to reach us
The Sun is about 150 million km away: we see it as it was 8 minutes and 20 seconds ago.
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5
Olympus Mons is the largest known volcano in the solar system
It's on Mars and is about 22 km high, almost three times Everest.
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6
Astronauts grow taller in space
Without gravity the spine stretches and they can gain a few centimetres, which they lose on returning.
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7
A neutron star is incredibly dense
A teaspoon of its matter would weigh billions of tonnes on Earth.
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8
There are more stars in the universe than grains of sand on all Earth's beaches
One of popular science's favourite comparisons, based on estimates of the stars in the observable universe.
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9
Saturn would float in water
Its average density is about 0.69 g/cm³, lower than water's (1 g/cm³).
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10
More than a million Earths would fit inside the Sun
Its diameter is about 109 times Earth's.
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11
Jupiter's Great Red Spot is a storm bigger than Earth
It has been observed for at least 150 years, although it is shrinking.
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12
We always see the same side of the Moon
It takes the same time to spin once as to orbit Earth (tidal locking).
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13
There is no sound in space
Sound needs a medium such as air to travel; in a vacuum nothing can be heard.
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14
The Milky Way has hundreds of billions of stars
Estimates range from 100 to 400 billion.
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15
The Milky Way and Andromeda are heading for a collision
The two galaxies are approaching and could merge in about 4.5 billion years.
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16
The universe is about 13.8 billion years old
That's the age calculated since the Big Bang from the cosmic microwave background.
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17
Mercury isn't the hottest planet: Venus is
Its CO₂ atmosphere causes a runaway greenhouse effect: about 465 °C at the surface.
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18
From sunrise to sunrise, a day on Mercury lasts longer than its year
Sunrise to sunrise takes about 176 Earth days, twice its 88-day year.
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19
Voyager 1 is the most distant human-made object
Launched in 1977, it crossed into interstellar space in 2012 and is still sending data.
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20
The International Space Station circles Earth every 90 minutes
It travels at about 28,000 km/h: its astronauts see around 16 sunrises a day.
Candidates
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21
The Earth is not a perfect sphere
It is flattened at the poles: the equatorial diameter is about 43 km greater than the polar one.
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22
Pluto is smaller than our Moon
It is about 2,377 km in diameter, compared to 3,474 km for the Moon.
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23
Uranus turns on its side
Its axis is tilted about 98 degrees, so it rolls around the Sun almost like a ball.
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24
There are earthquakes on the Moon
The Apollo seismometers recorded "moonquakes," some lasting several minutes.
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25
The Sun has 99.8% of the mass of the solar system
All the planets, moons and asteroids together add up to just the remaining 0.2%.
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26
A day on Mars lasts almost the same as on Earth
The Martian sun lasts 24 hours and 39 minutes.
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27
There is a giant cloud of alcohol in the Milky Way
The Sagittarius B2 cloud, near the center of the galaxy, contains enormous amounts of ethanol.
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28
On Venus a day is longer than a year
Venus takes about 243 Earth days to spin once and 225 to orbit the Sun. And it spins the opposite way to almost every other planet.
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Comments (2)
Faltan cosas como que Urano gira tumbado de lado, o que Plutón es más pequeño que la Luna.
Lo de que en Venus el día dura más que el año me explotó la cabeza.