16. April 2026

50 Interesting facts about space and astronauts.

The cosmos is a realm of infinite wonder, and the humans who dare to explore it are just as extraordinary. From the physics-defying nature of the universe to the quirky realities of life in orbit, here are 50 captivating facts about space and the brave individuals who journey there.

1. You can't burp in space. The liquids and gases in your stomach don't separate due to the lack of gravity, so attempting to burp would result in a "wet burp."
2. A day on Venus is longer than a year on Venus. It takes 243 Earth days for Venus to rotate once on its axis, but only 225 Earth days to orbit the Sun.
3. Astronauts can grow up to 3% taller. Without gravity compressing the spine, astronauts' bodies expand, making them temporarily taller in microgravity.
4. The Sun's core is incredibly dense. A cubic meter of material from the Sun's core would weigh over 150,000 kg on Earth—more than a blue whale.
5. Footprints on the Moon will last for millions of years. With no atmosphere or wind, the historic footprints left by the Apollo astronauts will remain for eons.
6. A year on Mercury is just 88 days. It is the fastest planet in our solar system to orbit the Sun.
7. Space is completely silent. Sound waves need a medium (like air or water) to travel through, and space is a vacuum.
8. The hottest planet is not the closest to the Sun. Venus is hotter than Mercury due to its thick, carbon-dioxide-rich atmosphere that creates a runaway greenhouse effect.
9. Astronauts drink recycled urine. On the International Space Station (ISS), water is so precious that sweat and urine are filtered and purified to be made drinkable again.
10. There is a giant water cloud in space. A massive cloud of water vapor containing 140 trillion times the mass of water in Earth's oceans floats around a quasar 12 billion light-years away.
11. You can't cry properly in space. Tears don't fall; they just form into little liquid balls that stick to your eyes.
12. The Milky Way is on a collision course. In about 4 billion years, our galaxy will collide with the Andromeda Galaxy.
13. Astronauts describe space as smelling like welding fumes or burnt metal. The scent likely clings to their suits after spacewalks.
14. One million Earths could fit inside the Sun. The Sun is absolutely massive.
15. A "jiffy" is an actual unit of time. In astrophysics and quantum mechanics, a jiffy is the time it takes for light to travel one fermi (the size of a nucleon), which is about 3 × 10⁻²⁴ seconds.
16. The International Space Station is the most expensive object ever built. Its estimated cost is over $150 billion.
17. There may be a planet made of diamonds. The exoplanet 55 Cancri e is believed to be one-third pure diamond.
18. Astronauts must learn Russian. All crew members on the ISS are required to know English and Russian to operate the complex systems.
19. The footprints on the Moon are not the only human artifacts there. There are also American flags, scientific equipment, and even bags of astronaut poop left behind.
20. Space is not that far away. The official boundary of space, the Kármán line, is only 100 km (62 miles) above sea level.
21. The coldest place in the universe is not in deep space. It was created in a lab on Earth, where scientists cooled atoms to just a fraction above absolute zero.
22. Astronauts' hearts become more spherical in space. The heart doesn't have to work as hard to pump blood upward, so it changes shape.
23. There is water ice on Mercury. Despite being the closest planet to the Sun, craters at its poles are permanently shadowed and contain ice.
24. You would not explode without a spacesuit. While you would swell and lose consciousness in about 15 seconds, your skin is elastic enough to hold you together for a short time.
25. The largest volcano in the solar system is on Mars. Olympus Mons is about 22 km (13.6 miles) high—nearly three times the height of Mount Everest.
26. Astronauts use velcro to keep their food from floating away. Every item must be secured.
27. There are more stars in the universe than grains of sand on all of Earth's beaches.
28. The "overview effect" is a cognitive shift. Many astronauts report feeling a profound sense of unity and protectiveness for Earth after seeing it from space.
29. Saturn would float in water. It is the least dense planet in our solar system; its average density is less than that of water.
30. Astronauts have snuck sandwiches into space. In 1965, astronaut John Young smuggled a corned beef sandwich aboard Gemini 3, and the crumbs nearly caused an electrical disaster.
31. There is a planet where it rains glass sideways. On exoplanet HD 189733b, winds of over 7,000 km/h blow molten glass sideways.
32. The ISS travels at 28,000 km/h (17,500 mph). It orbits Earth about 16 times a day.
33. Black holes are not empty vacuums. They are incredibly dense objects with gravity so strong that light cannot escape.
34. Astronauts' fingernails often fall off after spacewalks. The gloves are so rigid that they can cause hand injuries known as "fingernail delamination."
35. One teaspoon of a neutron star would weigh about 6 billion tons.
36. The first animal in orbit was a dog named Laika. She was launched by the Soviet Union in 1957 aboard Sputnik 2.
37. You can see the Great Wall of China from space... but it's very difficult. Contrary to popular myth, it is not easily visible with the naked eye from low Earth orbit.
38. Time passes slower in strong gravity. According to Einstein's theory of relativity, time moves slower for someone standing on Earth than for someone floating in deep space.
39. Astronauts have to strap themselves to a wall to sleep. Otherwise, they would float around and bump into things.
40. Venus rotates backward. Most planets spin counterclockwise, but Venus spins clockwise (retrograde rotation).
41. The universe is beige. Astronomers combined the light from over 200,000 galaxies and found that the average color of the universe is a light beige they named "Cosmic Latte."
42. There may be more than three dimensions. String theory suggests there could be up to 11 dimensions that we cannot perceive.
43. An astronaut's sense of taste changes in space. Fluids shift to their head, causing congestion similar to a cold, which dulls their taste buds; this is why spicy food is popular.
44. Jupiter has a massive ocean. Beneath its clouds lies an ocean of liquid metallic hydrogen over 40,000 km deep.
45. The first word spoken on the Moon was "Houston." Buzz Aldrin said it immediately after landing: "Houston, Tranquility Base here."
46. There are rogue planets that wander alone in space. They are not bound to any star system and simply drift through the galaxy.
47. Astronauts lose their calluses. The skin on their feet softens and peels off because they don't walk on them in microgravity.
48. The largest known structure in the universe is the Hercules-Corona Borealis Great Wall. It is a galactic supercluster that is about 10 billion light-years across.
49. SpaceX has made reusable rockets commonplace. This has drastically reduced the cost of accessing space in the 2020s.
50. We have only explored about 5% of the universe. The remaining 95% is made up of dark matter and dark energy, which remain complete mysteries to science.