If you want the most virgin, cleanest pictures of our universe, the best thing to do is to leave Earth. Here on our planet you can find a whole bunch of all kinds of effects that interfere with our rendering capabilities. Light pollution limit our range of vision; the atmosphere hurts our resolution and our ability to see clearly; clouds and weather prevent us from collecting light; The sun and earth themselves block a huge portion of our field of view from anywhere on earth.
Yet observatories like Hubble, Chandra, Fermi, Spitzer, and others have demonstrated how efficient space telescopes can be. The views and data they returned to Earth taught us much more than similar observations from Earth could teach. Why not place a telescope on the moon then? Believe it or not, this is a terrible idea. She has only one positive point. And that's why.
Telescope on the Moon: Is It Bad?
The moon, at first glance, may seem like an ideal place to place a telescope. It has virtually no atmosphere, eliminating any fear of light pollution. It is located far from Earth, which should significantly reduce interference from any signals produced by humans. Extra-long nights also mean you can observe the same target continuously for 14 days without interruption. And since you have solid ground, you don't need gyroscopes or hover wheels. It would seem that everything is cool.
But when you start thinking about how the Moon revolves around the Earth, the entire Moon-Earth system that revolves around the Sun, you begin to understand some of the problems that this whole idea inevitably faces.
First, if you place your telescope on the moon, which side will you choose: near or far? Each of them has its own disadvantages.
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If you place your telescope on the near (Earth-facing) side of the Moon, you will always see the Earth. This means you can send and receive signals, control your telescope, and download data with virtually no delay, with the only limitation being the speed of light. But it also follows that interference from the Earth, such as broadcast signals, will always be a problem that you have to deal with.
On the other hand, if you are on the far side of the moon, you are fairly effective at protecting yourself from everything that comes from the earth, but you also have no direct data path or maintaining a communication signal. We'll have to install an additional mechanism, an orbiter, or conduct communications to the near side to operate the telescope.
In any case, you will have many problems that you will have to struggle with and which are usually not found in the abyss of interplanetary space. The two largest:
Moonquakes. Do you think it is the Moon that rules the tides on Earth? The tidal forces that the Earth exerts on the Moon are 20 times stronger than the tidal forces that the Moon exerts on the Earth. There are enough of them to provoke rather sickly moonquakes on the satellite.
Temperature difference. Due to the tidal blocking of the Moon by the Earth and its extremely slow rotation, it bathes in sunlight almost constantly for 14 days, and then plunges into total darkness for 14 days. Daytime temperatures can reach over 100 degrees Celsius, and at night the moon cools down to -173 degrees.
While a space telescope can control its temperature through active or passive cooling (or a combination of both), the telescope must cool below the temperature of the wavelengths it is trying to observe, or noise will obscure the intended signal. This would be a huge disadvantage for ultraviolet, optical or infrared astronomy, if any of them were tried to develop on the Moon.
Designing a telescope that can withstand these extreme temperatures and still work is a daunting task. Unsurprisingly, the only telescope on the moon we have is the near-side ultraviolet telescope of the traveler, which operates at wavelengths at which Earth's atmosphere absorbs almost all of the light.
For most applications, going into space would be a better option than the Moon. The lunar surface, judged by the extreme temperatures and difficulties of communicating with the Earth, offers more disadvantages than having a surface on which to build or do anything else.
But there is one very specific application that the Moon offers: radio telescopes. Earth is an incredibly "radio-loud" source, for natural and human reasons. Even in space, signals emanating from the Earth permeate the entire solar system. But the Moon provides tremendous immunity to Earth's radio signals: the far side of the satellite literally uses the entire lunar body as a shield.
Cosmologist Joe Silk wrote the following earlier this year:
We could detect signals for inflation, the first stages of the Big Bang, and the formation of the first stars in the universe with the lunar radio telescope. While there is hope of doing this on Earth or in space, the lunar far surface offers more sensitivity because it is shielded from Earth by a shield than any other option.
Nowadays, when any spacecraft goes beyond the Moon, as viewed from Earth, it hits a radio blackout. The fact that radio waves cannot pass through the moon means that no signals can be sent there or received during this period of time. Orbiting satellites, any distant stations or rovers, and even Apollo astronauts are losing their ability to communicate with Earth.
But this also means that they are protected from all kinds of polluting radio signals that are generated on Earth. GPS communications, microwaves, radar, cellular and Wi-Fi signals, and even digital cameras are among the many terrestrial sources contaminating radio observatories. But on the far side of the moon, all sources of interference are 100% blocked. This is the cleanest radio astronomy environment imaginable.
Dr. Gillion Scudder also notes that this idea has its drawbacks. Data transfer requires something like an orbital device that can communicate with both the Earth and the telescope. A telescope or array of radio telescopes must be built and deployed on the Moon and linked together if it speaks of an array (and this option is preferable). Alternatively, cables could be run to the near side for data transmission to Earth.
And the biggest issue will be cost. Transporting material to the moon, landing on the lunar surface, deploying and much more is a colossal job. Even the most modest proposal, the Lunar Array for Radio Cosmology (LARC), consists of over a hundred simple design antennas spread over a two-kilometer range. The project will cost $ 1 billion and will be the most expensive radio array in Earth's history if built.
Virtually any sensible astronomical proposal implies that space is much better than the lunar surface for telescope placement. Temperature drops occur at all points on the moon. Only radio astronomers could gain the advantage of placing a telescope on the far side of the moon, but that opportunity would cost a pretty penny.
Until we find a way to cut costs or come up with something better, it is highly unlikely that we will ever see a lunar telescope that outperforms other options. The universe is not going anywhere, it is waiting for us to reveal its secrets.
Ilya Khel