Earth at Aphelion

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Earth at Aphelion

First, an important notice: Today’s program has a lot of numbers. So grab your phone or pencil and get ready — there might be a quiz.

The reason for the numbers is Earth’s location in its orbit. Today, we’re farthest from the Sun for the entire year — 94 and a half million miles. That’s one and a half million miles farther than average.

The distance changes because Earth’s orbit is an ellipse — like a circle that’s been stretched out. So during the year, the distance to the Sun varies. We’re closest in January, and farthest in July.

The average distance from the center of Earth to the center of the Sun is known as an A-U — an astronomical unit. It’s a basic yardstick for measuring distances within the solar system and in other star systems.

But using the Earth-Sun distance to define the astronomical unit has some problems. For one thing, the distance changes, and not just because of Earth’s lopsided orbit. So in 2012, astronomers adopted a precise, constant value for the A-U. Are those phones or pencils ready? The A-U is now defined as 149 billion, 597 million, 870 thousand, 700 meters. That’s 92 million, 955 thousand, 807.273 miles.

Now, about that quiz: Lined up end to end, how many large pepperoni pizzas could fit between Earth and the Sun? A-plus to everyone who figured it out, because we haven’t — but we are hungry for pizza.

Script by Damond Benningfield

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