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Did you know? The Light Year...

This month . . . The Light Year. A unit of distance, not time.

A light year is an astronomical measurement of the distance light travels in one year. A staggering 10 trillion kilometres per year.

Because the universe is so vast, astronomers use the Light Year to measure distances between objects. It’s much easier to think of the Andromeda Galaxy, one of our nearest galaxies, as being 2.5 million light years away rather than 21,000,000,000,000,000,000 kilometres, or 21 quintillion kilometres, which becomes rather meaningless.

Other related measurements include:

The Light Second: The distance light travels in one second, 300,000 kilometres per second. Our Moon is about 1¼ light seconds from Earth.

The Light Minute: Light from the Sun, 150 million kilometres away, takes eight minutes to reach Earth. This means we are seeing the Sun as it was eight minutes ago.

The first person to measure the speed of light was Danish astronomer Ole Romer in 1676 by timing the eclipse of Jupiter’s moon Io. Until that time scientists assumed the speed of light was either too fast to measure or infinite.

Light moves so fast it can travel around the Earth 7.5 times in one second. Blink and you would miss it!

And for an amazing piece of trivia … if you wanted to count as fast as a light year, you'd have to count to 186,000 every second!


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