funfacts.space
Interactive calculators that put the true scale of the universe in your hands. Numbers only, no fluff.
How large does an object appear in the sky? Enter any two of diameter, distance, or angular size, and the calculator solves for the third.
How bright does an object appear? Calculates apparent magnitude for stars and planets, with comparison bars and a sky visualization.
How long does it take light to travel between any two solar system objects? Enter a distance or a time, and the calculator solves for the other.
How much would you weigh on Jupiter? Enter your weight, toggle lbs or kg, and see your weight on every planet, moon, and the Sun.
Real atmospheric readings from NASA's Curiosity rover. Browse the latest week of Martian sols: temperature, pressure, UV, and sunrise and sunset times, with Earth comparisons for context.
Decode the math behind any optics spec. Enter magnification and objective diameter to get exit pupil, light gathering, limiting magnitude, and field of view, plus reference tables for common sizes.
How fast do you need to go to break free from a planet's gravity? Escape velocities for every solar system body, with perspective on what these speeds really mean.
Your age is just a count of laps around the Sun. Enter your birthdate and see how old you'd be on every other planet, and when your next birthday there actually is.
What phase is the Moon in today, on your birthday, or ten years from now? Get illumination, moon age, and countdowns to the next new, quarter, and full moons.
Shrink the Sun to the size of a basketball and watch the rest of the solar system shrink with it: see how big the planets get, and how far away.
Pick a vehicle and a destination. How long would it really take to drive to the Moon, fly to Mars, or coast to Pluto, non-stop, no gas stops, no traffic?
Sunrise, sunset, twilight, and golden hour for any date, anywhere on Earth, plus whether the days are getting longer or shorter right now.
How high is the Sun right now, and is it actually in your eyes? Pick a ZIP code, date, and time, then spin a compass dial to your driving heading and watch the windshield glare risk change live.
A panel's spec sheet says "400W." Pick a location, date, time, tilt, and cloud cover, and watch that sticker number get walked down to a real-world estimate, step by step.
How many communicating civilizations are out there right now? Drag all seven terms yourself and watch the estimate update live.
Every solar and lunar eclipse through 2028 with a live countdown, plus a check of whether the next Blood Moon will actually be visible from where you live.
Einstein's relativity, live: how much your clock actually slows down at relativistic speed or deep in a gravity well, from the ISS to a black hole's edge.
Earth's year is 365.2422 days, not 365. Type in any year and see exactly which rule, divisible by 4, then 100, then 400, decides whether it gets a February 29.
Enter a flight's altitude, latitude, and duration, or pick a space mission, and see how many millisieverts of cosmic radiation you'd absorb, counted in chest X-rays.
Pick two planets (or Pluto, or the Moon) and get the delta-v, travel time, and fuel needed for the cheapest transfer orbit, plus the next launch window when they line up.
Pick any date from 1000 to 3000 and see where every planet, Pluto, and the Moon are, which ones you could spot in the night sky, then press play and watch them move.
The Milky Way is roughly 13 billion years old and contains an estimated 100–400 billion stars. Even if only a tiny fraction host life, the galaxy should be teeming with civilizations, some millions of years ahead of us. So why is the universe silent? Enrico Fermi asked this over lunch in 1950, and we still don't have an answer.
Robin Hanson's Great Filter theory proposes that somewhere between dead chemistry and galaxy-spanning civilizations, there's a nearly impassable barrier. Either the filter lies behind us, meaning abiogenesis (life from non-life) is extraordinarily rare, or it lies ahead of us, waiting for every technological species. The latter is the terrifying possibility: the cosmos is quiet because something destroys advanced life before it can expand.
Perhaps advanced civilizations already know we're here, and have agreed not to interfere. Earth might be a protected reservation, observed from a distance while we develop naturally. It would explain the silence without requiring us to be alone. The disquieting implication: we may have been deemed not yet worthy of contact, or too fragile to survive the knowledge that we are not alone.
The classic mnemonic, the modern 8-planet "Nachos" version for the post-Pluto era, and the actual astrophysics behind why the planets ended up in that order: rocky worlds close to the Sun, gas and ice giants farther out, past the frost line.
Every planet's known moon count, the standout moons around each one, and why they actually matter: from Europa's hidden ocean to Titan's methane lakes to Saturn's ring-shepherding moonlets.
An interactive scale from absolute zero to the Planck temperature: liquid nitrogen, the Sun's surface and core, supernovae, the hottest thing humans have ever made, and how the universe cooled after the Big Bang.
All 24 SI prefixes from quecto to quetta, scientific notation made simple, why a European "billion" is a thousand times bigger than an American one, and the googol. Type in any number to see every way it can be written.
How far away humanity's most distant spacecraft is right now, ticking live. Send a ping at the speed of light and watch it crawl past Neptune and out of the heliosphere, look up any date from 1990 to 2100, and find out what the viral "Voyager runs on 1977 Fortran" meme gets right and wrong.