Our Place in Space: The Far Side of the Moon

Hello, friends!  Welcome to Our Place in Space: A to Z!  For this year’s A to Z Challenge, I’ll be taking you on a partly imaginative and highly optimistic tour of humanity’s future in outer space.  If you don’t know what the A to Z Challenge is, click here to learn more.  In today’s post, F is for…

THE FAR SIDE OF THE MOON

The James Webb Space Telescope has been getting a lot of press lately.  It’s the biggest and best telescope we humans have ever put into space.  But today, we’re going to imagine an even bigger and (potentially) an even better telescope.  We’re not going to put this telescope in space, though.  We’re going to build it on the surface of the Moon.

The far side of the Moon is the perfect location to build a radio telescope.  We’ve certainly built radio telescopes here on Earth, but those Earth-based radio telescopes keep running into the same two problems.  First, Earth’s atmosphere (especially the ionosphere) blocks certain cosmic radio wave frequencies from reaching us here on the ground.  And second, there’s a whole lot of terrestrial radio chatter happening here on the ground.  That chatter can interfere with any radio signals that do make it through from outer space.

But on the far side of the Moon, those problems don’t exist.  There’s no atmosphere, and certainly no ionosphere.  And since this is the far side of the Moon we’re talking about—i.e., the side of the Moon that always faces away from the Earth—all that terrestrial radio noise is gone.  The Moon itself would block those signals from ever interfering with our radio telescope.

The telescope itself would be absolutely enormous.  It would be built inside of a crater, with a dish approximately one kilometer wide.  NASA has already approved funding to research this idea; please note, they have not approved funding to build it yet!  Only to research the idea, to see if it’s actually feasible using current technology.  If it turns out that it is feasible, though, building a radio telescope on the far side of the Moon might end up being part of NASA’s new Artemis Program.

What would we do with our new lunar telescope?  Well for one thing, we could “look back in time” to see what the ancient universe was like.  Specifically, we could study a period of time known as the “cosmic Dark Ages.”  This would have been a time after the Big Bang but before the formation of the first stars—literally, the cosmic Dark Ages, like I said.  The hydrogen gas permeating the universe in that era would have emitted some amount of electromagnetic radiation, which we can still detect today in certain radio wave frequencies (or we could detect it, if Earth’s stupid atmosphere would stop getting in the way!).

In addition to looking for these naturally-occurring radio signals, our lunar radio telescope could also watch for radio signals that do not appear to be natural in origin.  Radio transmissions from aliens, in other words.

Searching for aliens would definitely not be the main reason to build a radio telescope on the Moon.  The stuff I said about the cosmic Dark Ages—that’s the main reason to do this.  The aliens thing would just be a side benefit.

For this “Our Place in Space” series, I’ve mostly focused on projects that I think could happen in the distant future.  But this lunar radio telescope project is something that probably needs to happen sooner rather than later.  The far side of the Moon is the perfect location for a radio telescope right now, but as humans start spreading out across the Solar System, things may change.  The far side of the Moon may get a whole lot noisier, in terms of radio chatter.

So in the distant future, rather than building a radio telescope on the Moon, we might prefer to build our radio telescopes farther out.  Places like Pluto, Orcus, Eris, or Quaoar—all those little dwarf planets beyond the orbit of Neptune—may end up being super useful for future radio astronomers.

Want to Learn More?

Check out this article from NASA’s Jet Propulsion Laboratory: “Lunar Crater Radio Telescope: Illuminating the Cosmic Dark Ages.”

Also, here’s an article from Universe Today: “The Moon is the Perfect Spot for SETI.”