Searching for radio waves to detect aliens

American scientists say they are not looking for messages from aliens and how to decode them, but are only focusing on finding radio transmitters that indicate the possibility of alien existence.

SETI's ATA telescope hunts for radio frequencies from aliens. Photo: SETI

According to Live Science, Edward Snowden, who is world famous for revealing secrets of the US National Security Agency, believes that humans cannot understand alien messages because they are encrypted.

However, scientists at the SETI Institute, which specializes in searching for extraterrestrial life, reject the above argument, saying that searches for extraterrestrial civilizations do not focus on decoding understandable signals.

"We're not looking for messages, but signals that someone has a transmitter," Seth Shostak, director of the SETI Institute's Center for Advanced Research in Space, said on September 23.

Snowden was mainly talking about encryption, but according to Shostak, data encryption is just a side-effect. All searches for alien signals to date have used radio waves.

In theory, this is the easiest and cheapest way to send signals far into space. SETI uses powerful radio telescopes to look for narrowband signals, or signals focused on a single frequency. Many natural objects can emit radio noise, but only radio transmitters can emit narrowband signals, according to the latest theory.

So if a signal of this type is detected, it must have been sent from a radio transmitter created by someone, even if the message contained within is encrypted and unreadable.

Snowden mentioned the hypothesis that humans could "eavesdrop" on signals from alien communication devices, but it is also incomprehensible because they would be "invisible" among the countless radio signals of the universe.

However, Shostak rejects this claim. According to him, any broadcast signal will have narrow-band components that humans can detect.

The problem right now is that technology can't detect signals at such great distances, says Doug Vakoch, a SETI researcher in charge of communicating with aliens.

“Even our radio and television signals beamed out into space cannot be detected from another star system closest to us,” Vakoch said.

In the next few hundred years, technology may develop to increase the range of signal reception. In other words, Snowden's conjecture about encryption only makes sense if the problem of receiving signals from a distance is solved. Besides, encryption is not the biggest challenge when it comes to "eavesdropping".

“If a civilization wanted to hide its presence, it wouldn’t need to worry about encryption,” Vakoch said. “With the way telecommunications technology has evolved, we’ve lost so much signal out into space. Now, using fiber optic cables or satellites can help reduce this signal loss.”

So if another civilization wanted to find out, they would have picked up signals from Earth and sent their signals thousands or even millions of years ago. If they didn’t, we simply couldn’t hear each other because of the vastness of space and time. Our best hope for finding alien life so far is to try to find their intentional messages.

If aliens were intentionally sending us a message, they would have to find a way for us to understand it, it couldn't be coded so hard that we would receive it but not be able to read it.

Signals from Earth

The same goes for the other way around. In 1974, scientists sent the “Arecibo message” from the Arecibo radio telescope in Puerto Rico into space. It was a three-minute, 1,679-bit broadcast consisting of 73 lines of 23 characters each, representing the numbers 1-10, the atomic numbers of several elements important to life on Earth, information about DNA, the human form, a diagram of the solar system, and an image of the telescope.

The only two prime numbers that multiply to 1,679 are 73 and 23. If aliens could pick up the radio waves, they would have to know math, Vakoch said. They may not understand the full message, but they might recognize the symmetrical patterns in the reconstructed images that would help them realize they had arranged them correctly.

“We wanted to create a kind of anti-cipher, a message that could be easily decoded,” Vakoch said. The packet was sent back and forth multiple times, to make sure that no part of the information was lost along the way.

In addition to radio waves, SETI is also conducting experiments to search for extraterrestrial life using other radiations such as visible light or infrared. However, infrared waves do not travel as far as radio waves and are more expensive.

In theory, it is also possible to determine whether a planet has life by scanning its entire outer atmosphere. This method is not yet possible due to technological limitations. If a planet has life, its atmosphere will contain unnatural gases. For example, on Earth, humans released CFCs (refrigerants) into the atmosphere for decades before realizing the damage they did to the ozone layer and trying to cut them down, or fossil fuel use releases too much CO2 into the atmosphere. Even high CO2 concentrations alone do not confirm that a planet has life, as on Venus.

It is also possible to detect life by looking at the infrared radiation emitted by a planet. If there is a civilization, it is likely that the infrared radiation from that planet will be higher than normal. However, current human technology does not allow us to determine the infrared radiation of a planet. We can only determine the infrared radiation emitted by a star.

There is another argument against Snowden’s argument. A study published in 2013 estimated that about 22 percent of stars have planets at the right distance for life to appear, like Earth. Life could be anywhere in the universe, and humans always have the chance to stumble upon other civilizations.

According to VnExpress