# The Universe By Numbers

 Exponential or Scientific Notation: It is easier to write very large numbers such as 100,000,000 as 108 (“1” followed by 8 “0”s). Similarly very small numbers are written using negative exponents, e.g. 0.0000001 is 10-7 (the “1” is seven places to the right of the decimal point). Bear in mind though that 109 is ten times the size of 108, and 1018 is ten billion times larger.

Some of the numbers, both small and large, that are bandied around in modern physics are very difficult to grasp. Below is a table listing - from the infinitesimally small to the incomprehensibly large - some of the numbers which are relevant to the subject matter.

Obviously, the units used affects these numbers (e.g. meters, kilometers, miles, light years, etc), but I have tried to use consistent metric units throughout: meters for distance, seconds for time, meters/second for speed, degrees Kelvin for temperature, kilograms for mass, kilograms/meter3 for density, Joules for energy, Coulombs for electrical charge, kilopascals for pressure.

 The Scale of the Universe: Cary Huang has created an excellent interactive graphical representation of the scale of the universe, from strings to the edge of the observable universe.
The different types of measurements are also color-coded for convenience:

 0.0000000000000000000000000000000000000000000054 5.4 × 10-44 Planck Time (in seconds), the shortest meaningful interval of time, and the earliest time the known universe can be measured from. 0.000000000000000000000000000000000001616 1.616 × 10-35 Planck Length (in meters), the size of a hypothetical string. Lengths smaller than this are considered not make any physical sense in our current understanding of physics. 0.000000000000000000000000000000911 9.11 × 10-31 Approximate mass (in kilograms) of a stationary electron. 0.000000000000000000000000001 1 × 10-27 Approximate density (in kg/meter3) of the universe as a whole. 0.000000000000000000000000001673 1.673 × 10-27 Approximate mass (in kilograms) of a proton. 0.000000000000000000000000001675 1.675 × 10-27 Approximate mass (in kilograms) of a neutron. 0.000000000000000000000000005 5 × 10-27 Estimated critical density (in kg/meter3) of the universe, to allow a steady state between expansion and contraction (about 5 × 10-30 g/cm3). 0.00000000000000000000002 2 × 10-23 Effective radius (in meters) of a neutrino particle. 0.0000000000000000001602 1.602 × 10-19 Elementary charge (in Coulombs), i.e. the negative charge of a single electron, or the positive charge of a single proton. 0.00000000000000000052 5.2 × 10-19 Approximate energy (in Joules) of photons in visible light. 0.000000000000000001 1 × 10-18 Upper limit (in meters) on the size of the quark particles that make up protons and neutrons. 0.000000000000000001 1 × 10-18 Smallest object observable and measurable by current science. 0.00000000000000001 1 × 10-17 Approximate density (in kg/meter3) of the best vacuum achievable in a laboratory. 0.000000000000002818 2.818 × 10-15 Effective radius (in meters) of an electron according to classical theory. 0.00000000000001 1 × 10-14 Range (in meters) of the weak nuclear force within the nucleus. 0.00000000000008187 8.187 × 10-14 Rest mass-energy (in Joules) of an electron. 0.000000000001 1 × 10-12 Approximate mass (in kilograms) of the average human cell. 0.000000000005 5 × 10-12 Longest wavelength (in meters) of gamma rays. 0.000000000025 2.5 × 10-11 Radius (in meters) of a hydrogen atom. 0.0000000005972 5.972 × 10-10 Rest mass-energy (in Joules) of an alpha particle. 0.0000004 4 × 10-7 Approximate wavelength (in meters) of violet light, the shortest in the visible spectrum. 0.0000007 7 × 10-7 Approximate wavelength (in meters) of red light, the long in the visible spectrum. 0.007297 7.297 × 10-3 The fine-structure constant, α, measuring the electromagnetic interaction between elementary particles. 0.74 7.4 × 10-1 Proportion of all matter in the universe composed of hydrogen. 0 0 × 100 Temperature (in ° Kelvin) of absolute zero, the lowest possible temperature (equivalent to -273.15° Celsius). 1.48 1.48 × 100 Density (in kg/meter3) of Earth’s atmosphere at sea level. 2.725 2.725 × 100 Temperature (in ° Kelvin) of cosmic microwave background radiation. 3.14 3.14 × 100 Pi, the ratio of a circle's circumference to its diameter (more accurately 3.14159265358979323846...) 9.8 9.8 × 100 Strength of the gravitational field (in meters/second/second) at the Earth's surface. 92 9.2 × 101 Number of naturally occurring elements. 100 1 × 102 Wavelength (in meters) of the lowest shortwave radio frequency. 101 1.01 × 102 Standard atmospheric pressure (in kilopascals) for Earth at sea level. 331 3.31 × 102 Speed (in meters/second) of sound in air at sea level and 0°C. 464 4.64 × 102 Speed (in meters/second) of the Earth's rotation at the equator. 1,000 1 × 103 Density (in kg/meter3) of liquid water at 4°C. 1,366 1.366 × 103 Total solar radiation (in Joules) received from the Sun by one square meter of the Earth's surface per second. 5,780 5.78 × 103 Temperature (in ° Kelvin) of the surface of the Sun. 29,800 2.98 × 104 Speed (in meters/second) of the Earth in orbit around the Sun. 145,000 1.45 × 105 Ratio of the size of an atom of hydrogen to its nucleus (the ration of other more complex atoms is less). 150,000 1.5 × 105 Density (in kg/meter3) of the core of the Sun. 200,000 2 × 105 Speed (in meters/second) of the Solar System in orbit around the Milky Way galaxy. 552,000 5.52 × 105 Speed of the Milky Way galaxy, relative to the cosmic microwave background radiation. 3,474,000 3.474 × 106 Diameter (in meters) of the Moon. 12,756,000 1.2756 × 107 Equatorial diameter (in meters) of the Earth. 15,600,000 1.56 × 107 Temperature (in ° Kelvin) at the core of the Sun. 299,792,458 2.998 × 108 Speed (in meters/second) of light (or any electromagnetic radiation) in a vacuum. 384,000,000 3.84 × 108 Orbital distance (in meters) of the Moon from the Earth. 1,000,000,000 1 × 109 Approximate density (in kg/meter3) of white dwarf, or dead, stars. 1,390,000,000 1.39 × 109 Diameter (in meters) of the Sun (1.39 million kilometers). 10,000,000,000 1 × 1010 Temperature (in ° Kelvin) in a supernova explosion. 80,000,000,000 8 × 1010 Rough estimate of the number of stars in the Milky Way galaxy (estimates vary up to 4 × 1011). 150,000,000,000 1.5 × 1011 Mean distance (in meters) between the Earth and the Sun (150 million kilometers, or 1 Astronomical Unit). 380,000,000,000 3.8 × 1011 Pressure (in kilopascals) inside the core of the Earth. 900,000,000,000 9 × 1011 Estimated optical diameter (in meters) of Betelgeuse, a red supergiant star. 3,000,000,000,000 3 × 1012 Estimated optical diameter (in meters) of VY Canis Majoris, a red hypergiant and the largest known star (about 2,000 times the size of our Sun). 10,000,000,000,000 1 × 1013 Approximate diameter (in meters) of the Solar System (10 billion kilometers). 20,000,000,000,000 2 × 1013 Approximate density (in kg/meter3) of the universe at the electroweak epoch, about 10–12 seconds after the Big Bang. 90,000,000,000,000 9 × 1013 Theoretical total mass-energy (in Joules) of one gram of matter. 100,000,000,000,000 1 × 1014 Estimated number of cells in the human body (9 out of every 10 being bacteria cells). 9,460,000,000,000,000 9.46 × 1015 Distance (in meters) traveled by light in one year (1 light year or 9.46 trillion kilometers). 25,000,000,000,000,000 2.5 × 1016 Pressure (in kilopascals) inside the core of the Sun. 40,000,000,000,000,000 4 × 1016 Distance (in meters) to Proxima Centauri, the nearest star after the Sun (about 4.23 light years). 141,000,000,000,000,000 1.41 × 1017 Half-life (in seconds) of uranium (4.468 billion years). 200,000,000,000,000,000 2 × 1017 Density (in kg/meter3) of atomic nuclei and neutron stars. 432,000,000,000,000,000 4.32 × 1017 Estimated age (in seconds) of the universe, assuming 13.7 billion years since the Big Bang. 1,000,000,000,000,000,000,000 1 × 1021 Approximate diameter (in meters) of galactic disk of Milky Way galaxy (100,000 light years). 70,000,000,000,000,000,000,000 7 × 1022 Rough estimate of the number of stars in the observable universe (estimates vary from 1022 to 1024). 22,300,000,000,000,000,000,000 2.23 × 1022 Distance (in meters) to the Andromeda Galaxy, the nearest galaxy to our own (2.36 million light years). 2,000,000,000,000,000,000,000,000 2 × 1024 Diameter (in meters) of the Virgo Supercluster, the cluster of galaxies which includes our own Local Group of galaxies (about 200 million light years). 6,000,000,000,000,000,000,000,000 6 × 1024 Mass (in kilograms) of the Earth. 386,000,000,000,000,000,000,000,000 3.86 × 1026 Total energy output (in Joules) of the Sun each second. 880,000,000,000,000,000,000,000,000 8.8 × 1026 Approximate diameter (in meters) of the visible universe (93 billion light years). 1,000,000,000,000,000,000,000,000,000 1 × 1027 Temperature (in ° Kelvin) of the universe 10-35 seconds after the Big Bang, at the start of the inflationary epoch. 2,000,000,000,000,000,000,000,000,000,000 2 × 1030 Mass (in kilograms) of the Sun (1 solar mass). 40,000,000,000,000,000,000,000,000,000,000 4 × 1031 Mass (in kilograms) of Betelgeuse, a red supergiant star (about 20 solar masses). 141,700,000,000,000,000,000,000,000,000,000 1.417 × 1032 Planck Temperature, the temperature (in ° Kelvin) of the universe at 1 Planck Time after the Big Bang. 10,000,000,000,000,000,000,000,000,000,000,000,000,000 1 × 1040 Approximate ratio of the strength of the electromagnetic to the gravitational force between sub-atomic particles. 36,000,000,000,000,000,000,000,000,000,000,000,000,000 3.6 × 1040 Mass (in kilograms) of OJ287, the largest measured supermassive black hole. 687,000,000,000,000,000,000,000,000,000,000,000,000,000 6.87 × 1041 Gravitational binding energy (in Joules) of the Sun. 120,000,000,000,000,000,000,000,000,000,000,000,000,000,000 1.2 × 1044 Estimated energy (in Joules) released in a supernova explosion. 30,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 3 × 1052 Estimated mass (in kilograms) of the observable universe. 4,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 4 × 1069 Estimated total mass-energy (in Joules) of the observable universe. 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 1 × 1080 Estimate the total number of fundamental particles in the observable universe (other estimates go up to 1085). 5,100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 5.1 × 1096 Planck density, the density (in kg/meter3) of the universe at one unit of Planck time after the Big Bang.