Starship Asterisk*

Time Lapse of a Total Lunar Eclipse

Explanation: Why would a bright full Moon suddenly become dark? Because it entered the shadow of the Earth. Almost two weeks ago this exact event happened as the Moon underwent a total lunar eclipse. That eclipse, visible from the half of the Earth then facing the Moon, was captured in numerous spectacular photographs and is depicted in the above time lapse video covering about an hour. The above video, recorded from Mt. Lemmon Sky Center in Arizona, USA, keeps the Earth shadow centered and shows the Moon moving through it from west to east. The temporarily good alignment between Earth, Moon, and Sun will show itself again tomorrow -- precisely half a moon-th (month) later -- when part of the Earth will pass through part of the new Moon's shadow.

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Could a person from back in the days before the shape of the Earth was discovered have worked it out by watching lunar eclipses? Is there any historical evidence that anyone did?

BDanielMayfield wrote:Could a person from back in the days before the shape of the Earth was discovered have worked it out by watching lunar eclipses? Is there any historical evidence that anyone did?

It depends when you consider that the shape of the Earth was discovered. Aristarchus considered the Earth to be a sphere, nearly 300 years BCE.
http://en.wikipedia.org/wiki/Aristarchu ... ar_eclipse

Yup. Tomorrow marks the end of another moonth. I don't know about anyone else, but I've always got too much moonth left, at the end of my money.

I don't think it would take an eclipse to come up with the idea that the planet is round. Just looking at the phases of the moon is enough to determine that the moon is round and it's not a huge leap in logic to figure that the Earth might be another thing like the moon and the sun. Big round things. But it's really hard to put yourself into the shoes of an ancient person. I don't know how to they perceived things.

Nitpicker wrote:

BDanielMayfield wrote:Could a person from back in the days before the shape of the Earth was discovered have worked it out by watching lunar eclipses? Is there any historical evidence that anyone did?

It depends when you consider that the shape of the Earth was discovered. Aristarchus considered the Earth to be a sphere, nearly 300 years BCE.
http://en.wikipedia.org/wiki/Aristarchu ... ar_eclipse

http://en.wikipedia.org/wiki/Spherical_Earth wrote: Aristotle (384–322 BC) was Plato's prize student and "the mind of the school".[18] Aristotle observed "there are stars seen in Egypt and [...] Cyprus which are not seen in the northerly regions." Since this could only happen on a curved surface, he too believed Earth was a sphere "of no great size, for otherwise the effect of so slight a change of place would not be quickly apparent." (De caelo, 298a2–10)
Aristotle provided physical and observational arguments supporting the idea of a spherical Earth:

1. Every portion of the Earth tends toward the center until by compression and convergence they form a sphere. (De caelo, 297a9–21)
   Travelers going south see southern constellations rise higher above the horizon; and
   The shadow of Earth on the Moon during a lunar eclipse is round. (De caelo, 297b31–298a10).

A good summary here:
http://en.wikipedia.org/wiki/Spherical_Earth

especially:
http://en.wikipedia.org/wiki/Spherical_ ... cal_Greece

Edit: too late again!

Oh, interesting, instead of tracking the Moon, he tracked the Earth's shadow. Terrific...

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I, too, like the fact that you can decude the shape of the Earth by observing the shadow of the Earth on the Moon during an eclipse. After all, if the Earth was flat, its shape on the Moon should usually be (very) flattened. Lunar eclipses, then, should be all but non-existent.

Ann

That was a really nice video. I like when they mix it up and put videos on there.

My time lapse video would have showed cloud covers rolling in aroung 8 pm and not receeding till 10 am the next day!!! GRRRRR

This is an interesting video, and it looks like the sky was much clearer in Arizona than it was here on the northern California coast! Still, I'm glad I observed this eclipse in person and in real time, even through clouds and some fog. There's a certain majesty to watching the Moon move through Earth's shadow. You gain a visceral sense that we're sitting on a planet, casting a huge shadow and being orbited by a moon. It totally makes sense that the ancient Greeks would have deduced that the Earth is a spheroid.

<Preemptive response to potential quibble> Yes, I know, the Earth and Moon are both orbiting our mutual center of gravity. But the center of gravity of the Earth-Moon system is inside the Earth, so, to a first approximation, the Moon orbits the Earth. </prtpq>

Possibly worth noting that, over the course of the three and a half hours depicted in the time-lapse video (which includes ~75 minutes of totality), the camera appears to track the Earth's shadow westward at the solar rate of 15.00 degrees/hour (or arcmin/min, or arcsec/sec), whilst the moon moves westward at the lunar rate of ~14.49 degrees/hour, and the stars move westward at the sidereal rate of ~15.04 degrees/hour.

So, in the video, with North up and East to the left, the moon appears to move to the left (eastward) a lot faster than the stars appear to move to the right (westward).