What’s on the other side of the moon?
The moon always faces the Earth with the same side, so that we never really see the other side of it.
Although it’s sometimes called the dark side of the moon, it’s not literally dark – it receives light from the sun. We just don’t see that side of the moon very often.
What is there, on the far side?
Over time people have imagined all kinds of mysterious things happening on the other side of the moon, from Nazi moon bases to aliens. In reality, though, it’s not all that different from the side of the moon that’s facing us.
The first image of the far side of the moon was taken in 1959, by the Soviet space probe Luna 3.
[show image 1]
A much clearer photo was taken in 1972, during the Apollo 16 moon mission.
[show image 2]
Compared to the more familiar side of the moon, the far side has more craters, but otherwise it looks very similar. No big mysteries there!
We can actually see parts of the back of the moon from Earth, due to a process called libration. Although it doesn’t fully rotate in relation to the Earth, the moon does wiggle a bit, and we can peek around it a little bit. This is easiest to see when you compare images of multiple full moons.
[Show animation of moon libration]
Some scientists have shown a particular interest in going to the far side of the moon.
Even though it might look just like the near side, there is one important feature of the far side of the moon: From there, you can get a very clear and undisturbed radio signal from outer space.
Radio signals from outer space? That’s right, but don’t worry - we’re not talking about aliens!
Radio waves are a type of electromagnetic radiation that doesn’t just come from your stereo, but also occurs naturally.
Cosmologists can learn a lot about the history of the early universe by using radio telescopes that pick up cosmic background radiation. This radiation contains information from the very early formation of the universe, from just after the Big Bang.
These signals are quite difficult to detect, and it’s not made any easier by being on Earth.
The ionosphere region of the Earth’s atmosphere interferes with measurements of cosmic background radiation, and so do the signals that come from satellites and FM radio stations.
These signals are all impossible to avoid when you’re on Earth, but they would be far less of a problem if it was possible to put a radio telescope on the far side of the moon, and that is exactly what cosmologists are now planning to so!
It’s a long-term project, but within the next few decades the proverbial dark side of the moon might turn out to be enlightening after all.
CITATIONS
Adapted from an original blog post I previously wrote for The Finch and Pea: http://thefinchandpea.com/2014/04/01/the-dark-side-of-the-moon/
Images and animation:
Image 1: http://www.planetary.org/multimedia/space-images/earth/20130429_luna3.html (NB This image is copyrighted and requires permission before use)
Image 2: http://en.wikipedia.org/wiki/File:Back_side_of_the_Moon_AS16-3021.jpg
Moon libration animation: https://www.youtube.com/watch?v=3f_21N3wcX8
Sources:
http://www.planetary.org/blogs/guest-blogs/bill-dunford/20130429-dark-no-more-exploring-the.html
http://apod.nasa.gov/apod/ap070103.html
http://www.newscientist.com/article/mg21428713.300-far-side-of-the-moon-offers-quiet-place-for-telescopes.html#.VBBLLGOwSp6
DESCRIPTION
The far side or dark side of the moon looks a lot like the side that’s facing Earth, but is a great place to put a telescope to study the early universe..
TAGS
moon, far side of the moon, space, astronomy, cosmology, libration, radio telescope, radio signals, radio waves, electromagnetic radiation
