We might find little green men. Radio waves or strange chemicals in the planet's atmosphere could be what we find. Something no one has thought of yet?
Scientists have pondered what life beyond Earth might look like, how humans might be able to identify it from afar, and whether communication between the two worlds might be possible.
Developing classification systems to fill with aliens has been included in that thinking. The Kardashev scale was proposed by the Soviet astronomer in 1964 and is used to evaluate alien civilizations.
There are 13 ways to hunt intelligent aliens.
What is the Kardashev scale?
The Kardashev scale is used to classify extraterrestrial civilizations. There are three categories based on how much energy a civilization uses.
Kardashev describes type I as atechnological level close to the level attained on the Earth, type II as a civilization capable of harness the energy of its own star, and type III as a civilization in possession of energy on the scale of its own galaxy.
The cut-offs for the energy involved weren't arbitrary. Kardashev used things that were easy to see, according to an astronomer at the European Southern Observatory who has built on his work. I'm almost tempted to say it's a publicity stunt, he uses comparisons to make it easier for people to understand.
Kardashev's scale is included in a 1964 paper called "Transmission of information by extraterrestrial civilizations." The paper was originally published in Russian, but it was translated into English the same year.
The scale caught people's imaginations, but "Transmission of information by extraterrestrial civilizations" focuses on calculating how powerful a light signal from any point of the universe would need to be for radio scientists to detect it. This is the cut-off for the energy use of a type II civilization.
Who was Kardashev?
Kardashev was a Soviet and Russian astronomer. Frank Drake, Giuseppe Cocconi and Philip Morrison were all SETI leaders who published their famous equations three years before Kardashev's paper.
Kardashev developed a technique called very-long-baseline interferometry, which uses a global network of radio dishes as one radio telescope the size of Earth. The first ever black hole image was published in the year 2019.
Adding space-based telescopes to the Earth-based network would increase its observing power even more. He advocated for the Russian mission RadioAstron to do this type of work.
Humans are on the Kardashev scale.
Humans are a type I civilization on the Kardashev scale if they only work within the basic categories. Humans rank as a 0.7 because they have not harnessed the full energy of Earth.
The Kardashev scale relates to SETI.
Throughout the decades, scientists and science-fiction writers alike have praised and criticized the system.
One benefit of Kardashev's scale is that it focuses on detectability by humans, rather than technological advancement, which can be hard to observe.
It has been dubbed overly simplistic, both in considering only one characteristic and in its few, broad categories. Carl Sagan argued that Kardashev's categories represented too much of a jump in energy consumption and that they should be divided into smaller categories.
The Kardashev scale's focus on infinite growth as a measure of progress has become difficult to swallow. The dominance of SETI was the root of it. He said that bigger is better for radio astronomy. For them, more power meant a more advanced civilization. As humans have begun to experience the global chaos caused by our tapping of fossil fuels, the risks of idealizing constant energy-hunger have become clear.
Kardashev's paper speaks to the continuing tension of the search for life beyond Earth: is it more valuable to look for biosignatures, changes to a planet that only life at some scale from microbes to manatees can cause, or for technosignatures, signals like radio waves. "There is an ongoing argument which is more important," he said.
Kardashev's work acknowledges the biosignature side as well and suggests that each search can inform the other. He wrote that the discovery of even the very simplest organisms on Mars would greatly increase the probability that there are many type II civilizations. Radio astronomy searches could be a decisive part of resolving the problem.
The Kardashev scale has a legacy.
The true heart of the paper was a broader statement about SETI. He estimated the technical feasibility of interstellar communications. The classification that he came up with is not much more than a small part of the paper.
The paper's conclusion states that even if the calculations don't hold up, the potential reality of interstellar communications should.
Kardashev wrote that the estimates arrived at here are no more than a tentative nature. "But all of them are aware that the possibility of establishing contacts with other civilizations by means of present-day radio physics capabilities is realistic."
One researcher wrote that Kardashev's scale was meant to represent a practical guideline for what could be expected in the course of SETI searches, not a profound theoretical insight into the nature of extraterrestrial intelligence.
The scale is an important facet of SETI work, even as scientists question Kardashev's ideas. His name will not be changed.
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