What conclusions do scientists make from 60 years of the absence of signals from extraterrestrials

The fact that there are no recorded signals from extraterrestrials allows scientists to assess how often they occur. It turns out that our chance of catching at least one over the next 1800 years is only 50 percent.

An array of Allen radio telescopes, which are trying to pick up alien signals. Source: Seth Shostak, SETI Institute

Alien Exploration

Statements by the US military that the US government is hiding alien technology have caused a new wave of controversy about alien life in the world. At first, Seth Shostak, a senior astronomer at the SETI Institute, said that he refused to believe what was told at the Congressional committee. Now other scientists have started asking questions about what it means that people have been trying to find alien signals for several decades, but have not found them.

At first glance, it may seem that the fact that humanity has not caught a single signal from space for 60 years means that there are no aliens at all. However, an article recently published in Acta Astronautica does not really agree with this conclusion.

In it, the authors applied Bayesian data analysis to the very fact that we never received a signal. This type of data processing does not check how it really is, but only evaluates the probability of the veracity of a statement based on certain initial conditions. 

We won’t hear alien signals soon

The scientists used two main assumptions as initial data. The first is that intelligent life can appear in the Universe through biological evolution. We know this from the fact that it exists on Earth. The second is that we have not found it in space for 60 years of observations.

For this, they added a few additional conditions. The first is that our Earth is not unique, but is a typical planet. The second is that when an alien civilization emits signals, it sends them simultaneously in all directions, or in certain random directions. Because if everyone tried to contact, for example, the center of the Galaxy, then we, being at a distance of 26 thousand light-years from it, would definitely not hear anything.

All these assumptions are reasonable enough and do not seem artificial. Therefore, they allowed the authors to get an upper limit on the number of alien signals to be sent into space. With a probability of 95 percent, their number is no more than 5 in one Earth century.

It follows that the probability that we will hear at least one if we listen for 1800 years is only 50 percent. This means that if some civilization does not specifically send a signal to us, then the chances of hearing something are simply scanty. However, it is still necessary to try to catch them.

According to phys.org

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