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Odd facts

42 numbers that are true and hard to believe, each with a named source and a year. Grouped by topic. Every fact has its own page with the source and a little context, and a link to the test it goes with.

Space10

  1. Where did the iron in your blood come from?Every atom of iron in your blood was made inside stars that died before the Sun existed. Stars like the Sun cannot make iron at all.
  2. Is a day on Venus longer than its year?A day on Venus is longer than its year. Venus takes 243 Earth days to rotate once but only 225 to orbit the Sun.
  3. How much mass does the Sun lose every second?Every second, the Sun converts about 4 million tonnes of its own mass into energy through nuclear fusion.
  4. Are there more stars than grains of sand on Earth?There are more stars in the observable universe (about 10²² to 10²⁴) than grains of sand on all of Earth's beaches (about 10¹⁸).
  5. How much would a teaspoon of neutron star weigh?A teaspoon of neutron star material would weigh around a billion tonnes.
  6. How old is the sunlight you see?Light from the Sun takes 8 minutes 20 seconds to reach Earth. You have never seen the Sun as it is right now.
  7. How far away is Voyager 1?Voyager 1, launched in 1977, is now about 25.7 billion km from Earth and still sending data. On 18 November 2026 it passes one full light-day away.
  8. How long would it take to cross the Milky Way?Crossing the Milky Way at the speed of light would take about 100,000 years.
  9. How big is the Milky Way compared to the Sun?If the Sun were shrunk to the size of a white blood cell, the Milky Way would be roughly the size of Earth.
  10. How fast is the Milky Way moving?The Milky Way is moving at about 2 million km/h (roughly 600 km/s) relative to the cosmic microwave background.

Time2

  1. Was Cleopatra closer to the Moon landing or the pyramids?Cleopatra (born 69 BC) lived about 450 years closer in time to the Moon landing than to the completion of the Great Pyramid of Giza (c. 2560 BC).
  2. How long have humans existed, on a 24-hour Earth clock?If Earth's 4.54 billion years were compressed into 24 hours, Homo sapiens (about 300,000 years old) would show up in the last 6 seconds.

Biology13

  1. Are sharks older than trees?Sharks are older than trees. Shark-like fish appear about 450 million years ago; the first trees (Archaeopteris) about 385 million years ago.
  2. How many cells does your body replace each day?Your body replaces roughly 330 billion cells a day, about 1% of the total, most of them blood and gut cells. Some, like the neurons of the cortex, are never replaced.
  3. How big is a blue whale's heart?A blue whale's heart weighs around 180 kg, about the size of a bumper car. On deep dives it slows to as few as 2 beats a minute, rising to 25 to 37 at the surface.
  4. How fast does a mantis shrimp strike?The peacock mantis shrimp strikes at about 23 m/s. The collapsing cavitation bubble it leaves behind flashes with light and briefly reaches thousands of degrees.
  5. Are humans more closely related to fungi than to plants?You are more closely related to a mushroom than a mushroom is to a plant. Animals and fungi share a common ancestor (Opisthokonta) that split from plants earlier.
  6. Can the human eye see a single photon?The human eye can register a single photon. In a 2016 experiment, people detected single photons slightly better than chance.
  7. How much DNA is in one human cell?All 3 billion base pairs of DNA in a human cell, about 2 metres of it, fit into a nucleus roughly 6 micrometres across.
  8. What is the oldest living tree?The oldest known living tree is Old Tjikko, a Norway spruce in Sweden whose root system has been dated to about 9,550 years. The trunk you see is much younger; the roots keep sprouting new ones.
  9. Are there more bacteria than human cells in your body?Your body has roughly as many bacterial cells as human cells, about 38 trillion to 30 trillion. The old '10 to 1' figure was an estimate that nobody had checked for 40 years.
  10. How many breaths do you take in a lifetime?At 12 to 20 breaths a minute, an adult takes roughly 20,000 breaths a day and around 600 million in a lifetime.
  11. How many hearts does an octopus have?An octopus has three hearts and blue, copper-based blood. About two-thirds of its neurons are in its arms, which can act semi-independently.
  12. How long is all the DNA in your body?Each of your nucleated cells holds about 2 metres of DNA. Uncoiled and laid end to end, it would stretch roughly 10 billion km, from the Sun to Pluto and most of the way back.
  13. How much information does speech carry per second?Human speech conveys about 39 bits of information per second in every language studied. Fast-spoken languages pack less into each syllable.

Math3

  1. Are there more chess games than atoms in the universe?There are more possible chess games (Shannon's estimate: about 10¹²⁰) than atoms in the observable universe (about 10⁸⁰).
  2. How many ways can a deck of cards be shuffled?A shuffled deck of 52 cards has about 8 × 10⁶⁷ possible orderings. The Big Bang was about 4 × 10¹⁷ seconds ago.
  3. Why is squaring the circle impossible?Pi is transcendental: it is not the root of any polynomial with rational coefficients. That is why 'squaring the circle' with compass and straightedge is impossible.

History7

  1. Is Oxford University older than the Aztec Empire?Oxford University is older than the Aztec Empire. Teaching at Oxford is documented from 1096; the Aztec Triple Alliance was formed in 1428.
  2. Were mammoths still alive when the pyramids were built?Woolly mammoths were still alive when the Great Pyramid was built. The last population, on Wrangel Island, died out about 4,000 years ago, some 500 years after the pyramid was finished.
  3. Can you see the Great Wall of China from space?The Great Wall of China cannot be seen from space with the naked eye. It is only 5 to 8 metres wide and roughly the colour of the land around it.
  4. How old was Stonehenge when Rome was founded?Stonehenge's stone circle (about 2500 BC) was already some 1,750 years old when Rome was founded, in 753 BC by tradition. The stones were ancient before the Romans existed.
  5. Does honey ever go off?Honey does not spoil. Sealed jars of honey thousands of years old have been found in Egyptian tombs and reported still edible.
  6. How many times was writing invented?Writing was invented independently at least three or four times: in Mesopotamia and Egypt (c. 3300 BC), China (c. 1250 BC) and Mesoamerica (by c. 600 BC).
  7. How much trash does an American produce a day?The average American generates about 4.9 pounds (2.2 kg) of trash a day, over 800 kg a year.

Physics7

  1. Could all of humanity fit in a sugar cube?Atoms are mostly empty. Squeeze every human on Earth to the density of an atomic nucleus and all 8 billion of us would fit in about 2 cubic centimetres, the size of a sugar cube.
  2. Is the Eiffel Tower taller in summer?The Eiffel Tower is up to 15 cm taller in summer than in winter, because its iron expands in the heat.
  3. Is the Pacific bigger than all the land on Earth?The Pacific Ocean (about 165 million km²) is larger than all of Earth's land put together (about 149 million km²).
  4. How long does light take to escape the Sun?Energy released in the Sun's core takes tens of thousands of years to random-walk to the surface, then 8 minutes to reach Earth.
  5. How many atoms are in a grain of sand?A single grain of sand contains around 10¹⁹ atoms, more than the number of grains on a large beach.
  6. Why does ice float?Water is one of very few substances that is less dense as a solid than as a liquid. If ice sank, lakes and seas would freeze from the bottom up.
  7. How fast do gravitational waves travel?Gravitational waves travel at the speed of light. In 2017 a neutron-star merger was seen in both gravity and light, and the two signals arrived within 2 seconds of each other after 130 million years.

Prefer them shuffled? The odd facts feed shows the same 42 in random order with a filter by topic.