10 August 2008

Earth and Moon movie

NASA has done something amazing. One of their spacecraft has made a movie of the Moon passing in front of the Earth as it orbits our planet.

The Moon passing in front of AfricaThis was not a simple achievement! To see things from a suitable distance you need to have a camera position many times further away than the Moon.

A hundred and twenty times as far as the Moon would be fine, and this is what NASA has done.

Just think, the Moon circles the Earth once every 28 days, drawing out a circle half a million miles across. From our perspective the Moon glides past the starry constellations of the night sky.

But if we could travel far enough away we'd see the Moon sometimes one side of the Earth, sometimes the other, but never straying very far.

First, sit back and watch the movie. Then come back and read more of this blog post to find out how it was done.

In the year 1610 Galileo saw four points of light changing position night by night when he turned his telecope on the bright planet Jupiter. He realised that these points of light were circling Jupiter. It was final proof that not all celestial bodies orbit the Earth and therefore our planet cannot be the centre of the universe as was supposed by the mediaeval church.

This is exactly how the Moon would be seen to behave from a camera 31 million miles away, and this is what the video shows.

Here's how this amazing video was made. The Deep Impact spacecraft successfully investigated a comet in July 2005, but with its primary mission completed NASA decided it could usefully perform two further tasks. The Deep Impact team realised that they could also use the spacecraft to take images of the Earth and Moon, and they commanded the craft to take a series of images through four different colour filters at 15 minute intervals. Afterwards, the images were combined to make full colour versions and a series of the colour images were put together to make the video.

Learn more about Deep Impact (now renamed EPOXI) and the Earth/Moon video from NASA's website.


  1. Chris,

    Thanks for sharing that.

    Have you seen the site...

    it is kind of out there. They are contending for geocentric universe.
    I'd like to hear your comments on that.

    Barry Steinman

  2. Hi Barry,

    Thanks for raising this, sorry to take so long to reply. There are two comments I can make.

    1 - The moment Galileo recognised that he'd seen moons circling Jupiter, he knew that the idea that every celestial body circled the earth was plain wrong. He already knew this for other reasons, but here was a fact that could be checked by anyone who cared to look through a telescope.

    When those who saw themselves as church leaders said the Earth was the centre of the Universe, they actually meant that everything else revolved around it. Galileo showed this was not so.

    2 - Taking the wider universe of galaxies and galaxy clusters that we know today, anywhere could be regarded as the centre because there is no edge to the universe. On that largest of scales, everything seems to be moving apart and would seem so from any arbitrary point.

    Imagine a two-dimensional universe of dots on the surface of an expanding sphere. As the sphere expands the dots grow further and further apart. But which dot is at the centre? None of them, yet choose any dot you like and it appears to be the centre.

    It's as if our three-dimensional universe is on the skin of an imaginary four-dimensional balloon and the balloon is expanding. The galaxy clusters are like dots on the surface of the balloon. A situation we struggle to imagine!

    Geocentricity is plain wrong, we are going around the sun! You could say it's a Virgo Cluster centric universe, but it really only appears that way. http://geocentricty.com/ has it wrong (my opinion).

    It's wrong in another way too. The Bible was not intended to be an astronomy text, everything in it was written to illuminate the nature of the Almighty and our relationship with him.

    We need to use this wonderful book for its intended purpose and not be side-tracked into arguments about astronomy, or history, or poetry, or geography, or law, or agriculture, or biology or any of the many other things that are found in the Bible. None of them is there for its own sake, but to reveal the heart and nature of the Most High.

    Astronomy shows the magnitude of his creative power, and the smallness of mankind.

    Does that help?




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