"Magnified" lunar eclipse? I don't think so

The BBC last week ran a story on Saturday's partial lunar eclipse. I have no objections to the BBC coverage lunar eclipses, but I do have problems with non-science writers covering them.

Just a bit of background, for viewers in Asia and the Americas this lunar eclipse would have appeared while the Moon was near the horizon. The Moon is bigger near the horizon right? Kinda.

The article of the title was "Lunar eclipse 'magnified' in US". A pathetic attempt at trying to make it seem more interesting. The article went on to say:

A partial lunar eclipse taking place on 26 June will appear magnified in the US by an effect known as the "moon illusion". [...] According to Nasa, low-hanging Moons look "unnaturally large when they beam through trees, buildings and other foreground objects". The reason for this is not understood.

NASA huh, well you could have just asked your local amateur astronomer and got an answer. The reason for the effect is NOT unknown.

The Moon, or the Sun for that matter (please don't look directly at the Sun), do look larger when they're near the horizon compared to high in the sky. However you can take a simple measurement to show they're the same size regardless of where they are in the sky, about half a degree across.

The effect is an optical illusion created by our brains. Our brains use other objects to estimate the size of things. Trees and houses, things you'd see on the horizon are pretty big. The Moon looks like it's close to them and about the same size or bigger, so hmmm the Moon must be big too. When the Moon is off by itself high up in the sky we have nothing else to compare it to.

Effect not unknown.

1 comment

Comment from: Nicole [Visitor]

Grin. Guess the only thing that was missing was: 'The man in the moon blew up the big balloon'.... or something along those lines :)

29th June 2010 @ 14:51

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