What’s wrong with this picture?

I snagged this image from a National Weather Service page explaining spring and neap tides. Can you see anything wrong with it?

earth moon

The tidal bulge, maybe? The direction of orbit?

Nope. What’s wrong with this image is the same thing that is wrong with many, many images that we are all shown of the Earth and Moon: the physical distance between the two is utterly wrong. It’s compressed beyond all recognition. If the Moon were really this close to the Earth, high tide wouldn’t be visible just on the ocean. It would be visible on land, too, because the gravitational pull of the Moon would be insanely strong.

It’s not that various government agencies and textbook illustrators want to lead us astray. It’s that they want to keep the size of their illustrations reasonable, therefore they must compress the distance. But we humans are visual creatures, so even when we learn in that same textbook that the Moon is 356,400 km from the Earth (at its closest), we don’t really internalize that. It’s just a number. What we do internalize is the accompanying illustration.

The result? A huge majority of the population, including highly educated people, who have a completely unrealistic idea of how far the Moon is from the Earth. Check out this video, in which an interviewer asks people on the street to show him how far the Moon is from Earth:

Here’s a better way of visualizing the distance (because pure numbers just aren’t memorable): look at the diameter of the Earth. Now imagine that times 30. That’s how far away the Moon is. (Actually, it ranges from 28 to 32 times the diameter, but 30 is a nice neat average.)

The same principle applies to illustrations of our solar system. The actual distances are almost impossible to convey in a textbook or standard image (not without a 17-page foldout, at least), so the distances are compressed and once again people are left with a totally inaccurate impression. If you want to see an image of our solar system, drawn to scale both in planetary size and distance, check out this web site and scroll to the right. But scroll slowly at first, or you’ll miss the first few planets.


About Fletcher DeLancey

Socialist heathen and Mac-using author of the Chronicles of Alsea, who enjoys pondering science, politics, well-honed satire (though sarcastic humor can work, too) and all things geeky.
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3 Responses to What’s wrong with this picture?

  1. Lilaine says:

    Fantastic !
    I’m going to explore the solar system, now, just putting a weight on the Enter Key with the mouse pointer on the step by step scrolling.
    See you next year !!! 😀

  2. JR says:

    Did you know there’s a 1:1,000,000,000 scale model solar system in Alton Baker Park in Eugene, OR? You have to take the bike path all the way out to the Beltline (four miles or so) in order to reach Pluto.

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