Since the invention of radio (more than 100 years ago), man has been broadcasting into space in the hope that aliens will learn about our existence. So why has nobody responded?
Look at the photo below. The galaxy on it is a reconstruction of the Milky Way, whose diameter is 118,000 light years (or, as later studies show, even more). And the blue dot is how far our radio signals have gone (its diameter is about 200 light years). And, if we consider that in the Universe – billions of galaxies like ours, then the search for extraterrestrial life is unlikely to end soon.
For the first time, a focused radio signal into space, known as the Arecibo message, was sent in 1974. But all the other radio programs for more than 100 years go beyond Earth.
Many of them are distorted by the ionosphere. And at a distance of 100 light years, they are so weakened that they are almost impossible to detect. Therefore, even if outside of this radius there are aliens, they most likely will not be able to catch our signals.
The same can be true in another direction. Maybe somewhere in the 100 light years from us there is an alien civilization, which, as it turned out, developed radio technology at the same time as we do – and their signals are so weak that we cannot detect them.
Source: Science Alert