“How big is the Earth, Dad?”
Big numbers are hard for a young boy to get his head around. I’m going to have to use some sort of comparison.
“Remember when we looked at the full Moon? The Earth is about four times bigger than the Moon.”
“But the Moon looks small.”
“That’s because it’s far away. If you were standing on the Moon and looked at the Earth, it would look about four times bigger than the Moon when you look at it from here.”
“OK.”
I’m not really sure my explanation has been successful.
Still, for future purposes, I think it’s just as well to note the basic facts.
Basic facts about Earth
The Earth isn’t completely round. It’s an oblate spheroid, similar to a slightly squashed ball. As Earth spins, it bulges out slightly at the equator due to centrifugal force. Imagine yourself on a roundabout in the park and it’s spinning really fast. An invisible force wants to push you off the roundabout.
That’s the same force that makes the Earth bulge.
The Earth’s diameter at the Equator is 12,756 kilometres (7,926 miles). But the diameter from the North to South Poles – known as the Polar diameter – is 12,714 kilometres (7,900 miles). If you’re not sure what a is, think of a straight line from the surface of Earth that travels through the centre of Earth and reaches the surface on the other side.
If you traveled along the Equator around the world, you would go on a journey of 40,030 kilometres (24,873 miles).
The total area of Earth is approximately 510.1 million square kilometres (196.95 million square miles). Oceans, seas, lakes and rivers cover about 71 percent of the Earth’s surface, which is about 360 million square kilometers (139 millions square kilometres).
The Earth weighs about 5,974,000,000,000,000,000,000,000 kilograms (13,170,000,000,000,000,000,000,000 pounds).
The Earth is losing weight. Although the Earth gains about 40,000 tonnes of cosmic debris in the form of dust and meteorites every year, about 95,000 tonnes of hydrogen and 1600 tonnes of helium rise out of the atmosphere into space.
