Earth is unique among the planets of our solar system; its particular conditions have given rise to all sorts of life, including millions of plant and animal species. The planet is incredibly diverse—it has tall mountains and deep valleys, humid forests and arid deserts, warm climates and cold. Its 195 countries are home to over 7.5 billion people.

Key Takeaways: Planet Earth • The third planet from the Sun, Earth has a unique physical and chemical composition that allows it to support a huge range of plant and animal life. • Earth takes about 24 hours to complete one full rotation and about 365 days to complete one full revolution around the Sun. • Earth's highest recorded temperature is 134 degrees Fahrenheit, and its lowest is minus 128.5 degrees Fahrenheit.

Circumference

Measured at the equator, the circumference of the Earth is 24,901.55 miles. However, the Earth is not quite a perfect circle, and if you measure through the poles, the circumference is a bit shorter—24,859.82 miles. The Earth is a bit wider than it is tall, giving it a slight bulge at the equator; this shape is known as an ellipsoid, or, more properly, a geoid. The Earth's diameter at the equator is 7,926.28 miles, and its diameter at the poles is 7,899.80 miles.

Rotation on Axis

It takes the Earth 23 hours, 56 minutes, and 04.09053 seconds to complete a full rotation on its axis. However, it takes an additional four minutes for the Earth to revolve to the same position as the day before, relative to the sun (i.e. 24 hours).

Revolution Around the Sun

The Earth takes 365.2425 days to complete a full revolution around the Sun. A standard calendar year, however, is only 365 days. To correct for the drift, an additional day, known as a leap day, is added to the calendar every four years, thereby ensuring that the calendar year remains in sync with the astronomical year.

Distance to the Sun and Moon

Because the Moon follows an elliptical orbit around the Earth, and because the Earth follows an elliptical orbit around the Sun, the distance between Earth and these two bodies varies over time. The average distance between the Earth and the Moon is 238,857 miles. The average distance between Earth and the Sun is 93,020,000 miles.

Water vs. Land

Earth is 70.8 percent water and 29.2 percent land. Of this water, 96.5 percent is found within the Earth's oceans, and the other 3.5 percent is found within freshwater lakes, glaciers, and polar ice caps.

Chemical Composition

The Earth is composed of 34.6 percent iron, 29.5 percent oxygen, 15.2 percent silicon, 12.7 percent magnesium, 2.4 percent nickel, 1.9 percent sulfur, and 0.05 percent titanium. Earth's mass is about 5.97 x 1024 kilograms.

Atmospheric Content

Earth's atmosphere is composed of 77 percent nitrogen, 21 percent oxygen, and traces of argon, carbon dioxide, and water. The five main layers of the atmosphere, from lowest to highest, are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

Highest Elevation

The highest point on Earth is Mount Everest, a Himalayan peak that reaches 29,035 feet above sea level. The first confirmed ascent of the mountain took place in 1953.

Tallest Mountain From Base to Peak

Earth's tallest mountain as measured from base to peak is Mauna Kea in Hawaii, which measures 33,480 feet. The mountain reaches 13,796 feet above sea level.

Lowest Elevation on Land

Earth's lowest point on land is Israel's Dead Sea, which reaches 1,369 feet below sea level. The sea is known for its high salt content, which allows swimmers to practically float in the water.

Deepest Point in the Ocean

Earth's lowest point in the ocean is a section of the Mariana Trench known as Challenger Deep. It reaches 36,070 feet below sea level. High water pressure in this area makes exploring it very difficult.

Highest Temperature

The highest recorded temperature on Earth is 134 degrees Fahrenheit. It was recorded at Greenland Ranch in Death Valley, California, on July 10, 1913.

Lowest Temperature

The lowest recorded temperature on Earth is minus 128.5 degrees Fahrenheit. It was recorded at Vostok, Antarctica, on July 21, 1983.

Population

As of December 2018, the world population is estimated to be 7,537,000,0000. The most populous countries are China, India, the United States, Indonesia, and Brazil. Annual global population growth as of 2018 is estimated to be about 1.09 percent, which means that the population is increasing by 83 million people per year.

Countries

There are 195 countries in the world including the Holy See (the city-state of the Vatican) and the State of Palestine, both of which are recognized by the United Nations as "non-member observer states." The world's newest country is South Sudan, which was founded in 2011 after breaking away from the Republic of Sudan.