With Earth Day coming, here’s a quick quiz on our planet

Earth Day began in 1970 and takes place on April 22 every year.

Here are 10 questions to test your knowledge of the planet.

1. A day on Earth is 24 hours but it always hasn’t been that way. Are the days getting longer or shorter?

Answer: Longer. According to NASA, the length of Earth’s day is increasing. When Earth was formed 4.6 billion years ago, its day would have been roughly six hours long. By 620 million years ago, this had increased to 21.9 hours. Today, the average day is 24 hours long, but is increasing by about 1.7 milliseconds every century.

The reason? The moon is slowing down Earth’s rotation through the tides that it helps create.

2. What country has the driest place on Earth?A) U.S.B) Saudi ArabiaC) Chile

Answer C: The driest place in the world — the Atacama Desert in northern Chile — is next to the biggest body of water — the Pacific Ocean. Average annual rainfall in Arica, Chile, is just 0.03 inches. It is believed that Atacama’s Calama city saw no rain for 400 years until a sudden storm in 1972. Unlike most deserts, the Atacama is relatively cold and, in its most arid parts, does not even host cyanobacteria — green photosynthetic microorganisms that live in rocks or under stones.

3. The sun is about 93 million miles from Earth. How long does it take light from the sun to reach Earth?A) About 20 minutesB) About 8 minutesC) About 1 day

Answer B: The light of the Sun takes 8.25 minutes to reach us.

4. If the Sun were as tall as an average door front, about what size would Earth be?A) A nickelB) A tennis ballC) A basketballAnswer A

5. Is the snow-covered continent Antarctica (pictured above) a desert?1) Yes2) No

Answer: Yes. Antarctica is the southernmost continent, located primarily south of the Antarctic Circle (66°S). Antarctica is considered a desert because it receives very little rain or snowfall, and the small amount of snow it does receive builds up over hundreds and thousands of years to form large, thick ice sheets. The continent’s terrain is made up of glaciers, ice shelves and icebergs. The only plants that can survive the extreme cold are lichens, mosses and algae. Antarctica ranks only fifth in size (larger than Europe and Australia) and it is large enough that the entire U.S. could fit within its 5.4 million-square-mile size.

6. Of the eight planets (dwarf planet Pluto not included) in our solar system, where does Earth rank in terms of being the largest?A) ThirdB) FourthC) Fifth

Answer B: The Earth’s diameter (distance straight through the middle) measures 7,917.5 miles, making it the fourth-largest planet in the solar system. Jupiter, the largest planet, is 11 times the size of Earth.

7. What is the upper limit of our atmosphere called?A) StratosphereB) ThermosphereC) Exosphere

Answer C: There are six layers in our atmosphere. The exosphere extends from the top of the thermosphere up to 6,200 miles.

8. What percentage of the Earth is covered by water?A) 71%B) 81%C) 91%

Answer A: About 71% of the Earth’s surface is water-covered, and the oceans hold about 96.5% of all Earth’s water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in you and your dog. Water is never sitting still.

This image above shows blue spheres representing relative amounts of Earth’s water in comparison to the size of the Earth. Each sphere represents volume. They show that in comparison to the volume of the globe, the amount of water on the planet is very small. Oceans account for only a thin film of water on the surface.