50 Fun Facts About Planet Earth

Earth is which planet from the Sun?

It is the only astronomical object known to harbor life and the only Solar System world with liquid surface water.

What percentage of Earth's crust is covered by ocean?

The remaining 29.2% is land, mostly in the land hemisphere.

About how many years ago did Earth form?

It formed from gas and dust in the early Solar System, taking perhaps 70 to 100 million years.

Roughly what is Earth's circumference?

It is rounded into an ellipsoid and is the densest planet in the Solar System.

How long does Earth take to rotate once on its axis?

The solar day of 24 hours is slightly longer than this sidereal rotation.

At what distance does the Moon orbit Earth?

That is 1.28 light-seconds; the Moon is roughly a quarter as wide as Earth.

Which Mars-sized object is thought to have struck Earth and formed the Moon?

It had about 10% of Earth's mass; two remnants of it may still sit inside Earth.

Which supercontinent began to break apart about 180 million years ago?

Rodinia broke up around 750 Ma and Pannotia formed at 600–540 Ma before it.

The last ice age, the Last Glacial Period, ended about how many years ago?

Glacial cycles have repeated roughly every 21,000, 41,000 and 100,000 years.

The asteroid impact that ended the non-avian dinosaurs happened how many million years ago?

It largely spared small animals such as insects, mammals, lizards and birds.

Which element makes up the largest share of Earth's mass, at 32.1%?

Oxygen is next at 30.1%; the core itself is 88.8% iron.

What is the name of the boundary between Earth's crust and mantle?

The crust above it is about 6 km thick under the oceans and 30–50 km under continents.

How thick is Earth's crust beneath the oceans?

Under the continents it thickens to 30–50 km.

Earth's outer core is in what state?

It lies above a solid inner core whose radius is about one-fifth of Earth's.

The temperature at Earth's centre may reach up to roughly what?

Pressure there could reach 360 gigapascals, and the heat comes partly from radioactive decay.

Which isotope is NOT one of the three major heat-producing isotopes inside Earth?

Carbon-14 is used for dating, not planetary heating.

How many major tectonic plates does Earth have?

Pacific, North American, Eurasian, African, Antarctic, Indo-Australian and South American.

Which is the fastest-moving tectonic plate, at about 75 mm per year?

The slowest is the South American Plate at about 10.6 mm a year.

At which type of plate boundary do two plates slide past each other laterally?

Convergent boundaries bring plates together and divergent ones pull them apart.

The oldest oceanic crust, in the western part of the largest ocean, is about how old?

Most ocean floor is under 100 Ma old because it is recycled by subduction (Ma = million years, Ga = billion years).

What is the lowest point on Earth's land surface?

It sits at −418 m; the highest point, Everest, is 8,848 m.

How much longer is Earth's diameter at the equator than at the poles?

The rotation bulge is why Chimborazo's summit, not Everest's, is farthest from Earth's centre.

Which volcano's summit is the point on Earth's surface farthest from its centre?

It is in Ecuador, near the equatorial bulge.

How deep is the Mariana Trench below local sea level?

It shortens Earth's average radius by 0.17%.

Approximately when did Earth's magnetic field last reverse?

Reversals come at irregular intervals averaging a few times every million years.

Which process in Earth's core generates the main part of its magnetic field?

It converts the energy of convection in the liquid outer core into magnetic field energy.

Which radiation belts trap high-energy particles inside Earth's magnetosphere?

Particles diverted along field lines into the ionosphere cause auroras.

What is the approximate acceleration due to gravity near Earth's surface?

Local differences in topography and geology produce small gravity anomalies.

How often do the Earth and Moon orbit their common barycentre, relative to the stars?

The synodic month, new moon to new moon, is longer at 29.53 days.

The Sun's diameter is about how many times the Moon's, explaining their matching size in the sky?

It is also about 400 times more distant, which is why total solar eclipses are possible.

At roughly what rate is the Moon receding from Earth?

Tidal interaction also lengthens Earth's day by about 23 microseconds a year.

About how many days were in a year during the Ediacaran period, 620 million years ago?

Each day lasted only about 21.9 hours.

How long does sunlight take to travel from the Sun to Earth?

That is about 150 million km, the distance that defines the astronomical unit.

What is Earth's average orbital speed around the Sun?

Fast enough to cover Earth's own diameter in about seven minutes.

In which arm of the Milky Way is Earth located?

The Solar System orbits about 28,000 light-years from the galactic centre.

What is Earth's axial tilt, approximately?

The tilt, not distance from the Sun, is what causes the seasons.

Earth's axis precesses around a complete circle over roughly how many years?

This precession is why a sidereal year and a tropical year differ.

Around which date does Earth reach perihelion, its closest approach to the Sun?

Aphelion falls around 4 July, so northern summer comes when Earth is farthest away.

What percentage of Earth's atmosphere is nitrogen?

Oxygen is 20.946% and argon 0.934%, with carbon dioxide only a trace.

Three-quarters of the atmosphere's mass lies within which lowest layer?

It reaches about 11 km up and is where weather happens.

Without the greenhouse effect, Earth's average surface temperature would be about what?

The actual average is around +15 °C thanks to water vapour, CO2, methane, nitrous oxide and ozone.

The Kármán line, a working boundary between atmosphere and space, is at what altitude?

The ozone layer that shields the surface from ultraviolet sits far below it, in the stratosphere.

What is the average atmospheric pressure at sea level?

That equals 14.696 psi, with a scale height of about 8.5 km.

About what percentage of Earth's water is saline?

Of the 2.5% that is fresh, about 68.7% is locked in ice caps and glaciers.

What is the mean depth of the world ocean?

The oceans hold an estimated 1.332 billion cubic kilometres of water.

What name is given to the rise in atmospheric oxygen roughly 2,000 million years ago?

Life's photosynthesis altered the atmosphere and made the ozone layer possible.

The hypothesis that the planet was largely ice-covered 1000 to 539 million years ago is called what?

It preceded the Cambrian explosion, when multicellular life grew far more complex.

Humans emerged in Africa about how many years ago?

Our species has since spread to every continent, settling Antarctica only in the 20th century.

What percentage of humanity lives in the Northern Hemisphere?

Partly because 68% of the world's land mass is in the north.

Which is the oldest artificial satellite still in orbit around Earth?

As of 2021 about 4,550 operational satellites and over 16,000 pieces of tracked debris circled the planet.