How many atoms are there in the universe?
The standard answer is 10^80 atoms in the observable universe, and unusually for a number this large it is a calculation from well-measured cosmology rather than a guess. Ordinary matter is only about 5% of the universe's energy density; dark matter and dark energy make up the rest and are not made of atoms. About 90% of the atoms by number are hydrogen. The figure applies strictly to the observable universe — beyond the horizon there may be arbitrarily more.
How the figure is arrived at
Three published numbers multiplied together. The observable universe is a sphere of radius 4.4 × 10^26 m, giving a volume of 3.6 × 10^80 m³. The critical density is about 8.6 × 10^-27 kg/m³, of which baryonic matter is 4.9%, so 4.2 × 10^-28 kg/m³. Multiply for a total baryonic mass of 1.5 × 10^53 kg and divide by the mass of a hydrogen atom, 1.67 × 10^-27 kg: about 9 × 10^79, or 10^80 to the nearest power of ten.
How confident it is
- Low estimate
- 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000
- High estimate
- 10,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000
- Spread
- 10000.0× between the bounds
Other space and the universe counts
- How many stars are there in the universe? about 200 billion trillion
- How many stars are there in the Milky Way? between 100 billion and 400 billion
- How many galaxies are there? hundreds of billions — possibly 2 trillion
- How many satellites are in orbit? about 12,000 active satellites
- How many moons are there in the solar system? about 900 confirmed, and the number keeps moving
- How many planets are there in the galaxy? at least 100 billion — probably more planets than stars
- How many stars can you see with the naked eye? about 9,000 over the whole sky; roughly 2,500 at once
- How many constellations are there? exactly 88
- How much space junk is there? about 40,000 tracked objects, and over 130 million fragments too small to track
- How many asteroids are there? about 1.4 million catalogued
Common questions
- How many atoms are there in the universe?
- about 10^80
- How is that estimated?
- Three published numbers multiplied together. The observable universe is a sphere of radius 4.4 × 10^26 m, giving a volume of 3.6 × 10^80 m³. The critical density is about 8.6 × 10^-27 kg/m³, of which baryonic matter is 4.9%, so 4.2 × 10^-28 kg/m³. Multiply for a total baryonic mass of 1.5 × 10^53 kg and divide by the mass of a hydrogen atom, 1.67 × 10^-27 kg: about 9 × 10^79, or 10^80 to the nearest power of ten.
Related pages
- How many stars are there in the universe? about 200 billion trillion
- How many stars are there in the Milky Way? between 100 billion and 400 billion
- How many galaxies are there? hundreds of billions — possibly 2 trillion
- How many satellites are in orbit? about 12,000 active satellites
- How many moons are there in the solar system? about 900 confirmed, and the number keeps moving
- How many planets are there in the galaxy? at least 100 billion — probably more planets than stars
- How many stars can you see with the naked eye? about 9,000 over the whole sky; roughly 2,500 at once
- How many constellations are there? exactly 88
- How many people are there in the world? Living things and the natural world
- How many countries are there in the world? Things people built
- How many bones are in the human body? The human body
- How many grains of sand are there on Earth? Living things and the natural world
- How many ants are there in the world? Living things and the natural world
- How many trees are there in the world? Living things and the natural world
Sources
- Calculated on this page — At One Place