numbers2know.org

Type ▲ ▼	Description ▲ ▼	Value	Importance ▲ ▼
	Speed of light	300 000 kilometers per second
	Earth's age	4.6 billion years
	Extinction of the dinosaurs	66 million years ago
	Absolute zero	− 273 degree celsius
	Number of naturally occuring elements	98
	Pi	3.141 59...
	Speed of sound in air	~ 340 meters per second
	Age of the universe	13.8 billion years
	Time it takes light to travel from Sun to Earth	8 minutes
	Earth's axial tilt	23 degree
	Information stored in the human genome	~ 700 megabytes
	Earliest life on earth	3.5 billion years ago
	Radius of the earth	~ 6 400 kilometers
	Wavelength of visible light (blue-red)	400 - 700 nanometers
	Estimated number of stars in the Milky Way	200 - 400 billion
	Height of Mount Everest	8 848 meters
	Euler's number	2.718 28...
	Period of the moon's orbit	29.5 days
	Size of an atom	10-10 meters
	Surface temperature of the Sun	~ 5 500 degree celsius
	Temperature of maximum density for water	4 degree Celsius
	Composition of air (Nitrogen, Oxygen, Argon)	78, 21, 1 per cent
	Depth of the Mariana Trench	11 kilometers
	Distance to the horizon for an observer on sea level	~ 5 kilometers
	Rise of modern humans in africa	100 - 200 thousand years ago
	Typical size of a bacterium	1 - 5 micrometers
	Altitude of the International Space Station (ISS)	~ 400 kilometers
	Circumference of the earth	40 000 kilometers
	Construction of the pyramids at Giza	2600 - 2500 BC
	Escape velocity on earth	11 kilometers per second
	Normal human body temperature	37 degree Celsius
	Number of chromosome pairs in the human genome	23
	Number of planets in the solar system	8
	Sun - Earth distance	150 million kilometers
	Average blood volume of an adult	5 litres
	Chernobyl disaster	1986 AD
	First manned moon landing	1969 AD
	Pulse rate at rest	60 - 100 beats per minute
	Temperature of a candle flame	1 400 degree Celsius
	World population	8 billion people
	Height of Earth's atmosphere	100 kilometers
	Initiation of the Reformation by Martin Luther	1517 AD
	Invention of the printing press	~ 1440 AD
	Typical size of a plant/animal cell	10 - 100 micrometers
	Wavelength of X-rays	~ 1 nanometer
	Number of species on earth	~ 10 million
	Pitch standard	440 herz
	Abundance of Hydrogen in the Milky Way	74 per cent
	Begin of the construction of the Great Wall of China	~ 500 BC
	Diameter of the Milky Way	100 - 180 thousand light years

Close Help

Welcome on numbers2know.org !

This website originated as a tool to learn, collect and sort numbers.
Not just any numbers: It provides a topically broad list thereof – worth to be memorized, not just as part of general knowledge, but as a benchmark to gauge the world we live in.
These numbers can either be explored one after another in a quiz-like fashion, or accessed in an aggregated, tabular form. In addition, there is a simple voting mechanism that allows visitors to up- and downvote records to rate their importance.

The purpose of numbers2know.org is not to provide a comprehensive list to look up numbers, but to encourage and support people memorizing selected numerical values of general interest.

For more background information click here.

Modes

There are several modes controlled by the buttons in the top-right of this website:


There are three major modes: Random: Browse the list randomly. Sequential: Browse the list from highest rated to lowest rated records. List: View the complete list in tabular form.	There are two minor modes: All: The complete list is used (random and sequential mode). Top 30: Only the 30 highest rated records are used (random and sequential mode).

Random/Sequential mode

The control panel for these two modes is displayed below the (single) shown record.
There are four groups of buttons:


Control buttons (left): Next: Load the next record (either random or next lower rated) Back: Load the last 20 viewed records (button may be hidden when there is no history available).	There are up to four option buttons (right), from left to right: Notation: Show an alternative notation of the value (different units etc.). Compare: Show a table of other values to compare with. Note: Show additional notes. Reference: Open an external reference for further reading (Wikipedia).


Importance voting (left): Vote: You may up- or downvote each record (arrows), and withdraw your vote by the centered circle. Gauge the records with respect to their relevance for a general audience. Importance: The shown rating is the difference of total up and down votes. It can be positive (rather important) or negative (rather unimportant).	Test mode (right): Disabled (dark): This is the default behaviour. The values of newly loaded records are immediately shown. Enabled (red): This mode allows to test yourself. Only the description is shown, the value is hidden and can be unveiled by hitting (SPACE).

List mode

This mode lists all records in the database in a condensed tabular form.
It provides only a restricted set of the options available in random/sequential mode:

Type: A pictogram indicating the type of the record (length, time, etc.). Can be ordered.
Description: Description of the record. Click to load the record in sequential mode. Can be ordered.
Value: Value of the record.
Importance: Importance and voting-widget for the record. Can be ordered.
The complete database is split into pages with a fixed number of rows. The pages and number of rows per page can be specified above the table.

Miscellaneous

You may share numbers2know.org via the buttons in the lower-right part of this website.

Additional links on the bottom of the page:

About: Show further information about numbers2know.org (how to contribute, legal info, ...).
Shortcuts: Show tooltip with shortcuts for random and sequential mode.
Help: Show this help window.