17 HW Calculating Speed of Light

Using Romer’s value for the maximum delay and a rough estimate of the diameter of Earth’s orbit, he was able to calculate the speed of light using the basic physics equation that says velocity equals distance over time. And he came pretty close!

Huygens

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Today we know that the speed of light is roughly 300 million meters per second - so the calculation was a little off.

That’s because they didn't have a precise value for the width of Earth’s orbit, and because the maximum delay Romer calculated was a few minutes too long.

But hey, it’s not bad for a _ astronomer who wasn’t even trying to discover the speed of light. 

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17th-century

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We know that light travels through a vacuum at a specific speed. And we even know what that speed is. In fact, we also know that the speed of light is not just any number. It’s the fastest anything can travel in the universe - the universal speed limit.

 

(Note: Sign shows the speed of light in miles per second)

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300,000,000 m/s

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In the 1670s, the Danish astronomer Ole Rømer had been commissioned to create a chart sailors could use to determine their _. That is, how far east or west they were - while they were at sea.

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longitude

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Romer knew that the difference between Earth and Jupiter’s closest approach and their farthest approach had to equal the diameter of Earth’s orbit.

So, over the course of about half a year - as Earth moved from one side of its orbit to the other - he measured a maximum delay of _ minutes.

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