Much has been published about the search for “intelligent life”. We’ve been scanning the heavens for radio signals that might have been sent by another civilization or from another planet, although we haven’t found anything yet. We’ve also been broadcasting our own radio signals hoping that somoeone or something in the universe is also listening. We’ve actually been broadcasting our existence for some one hundred years now in the form of television and radio broadcasts. In January of 1903, Gugliemi Marconi transmitted a signal from Massachusetts to Great Britain, and in 1909, Marconi and Karl Braun were awarded the Nobel Prize in physics for their work in wireless radio transmissions. Radio and television broadcasts have been eminiating from Earth on a regular basis for decades, anbd the signals that have been created here are now on their way to other parts of the universe. Since those signals are relatively simple, it should be easy for an advanced alien civilization to receive and decode them. So why have we never received a reply? Where is everyone?
One of the reasons we haven’t heard from anyone is that the universe is a big place; a very, very big place, and it takes a long time for a radio signal to be sent or received. Let me try to put it in perspective.
Throughout the universe, the laws of physics appear to be uniform. Gravity, dark energy, electromagnetism, and light appear to work the same as they do here on Earth. Einstein’s cosmic speed limit of 186,000 miles per second applies not only to light but to radio waves sent from Earth as well as radio waves sent from other places in the universe. While the speed of light is fast, it pales in comparison to the immense distances encountered in the universe.
The Earth orbits our Sun at a distance of some 93 million miles. Several other planets also orbit the Sun, and together they comprise our solar system. Our solar system is located in one of the arms of a spiral galaxy we call the Milky Way. The Milky Way galaxy is a group of over 400 billion planets and stars. It is over 120 thousand light years wide. The Milky Way is so large that our solar system has only made 16 round trips around the center of the galaxy since the universe was formed some 13.7 billion years ago.
The galaxy closest to us where we might find life is M31 in the constellation Andromeda, a galaxy with over one trillion stars. Close is a relative term, however, since Andromeda is some two million light years from Earth. The light we see from Andromeda has taken over two million years to get here, so we’re seeing it today as it was two million years ago. A radio signal from Andromeda would have to have been sent over two million years ago to allow us to receive it today. It will take our radio signals two million years to reach Andromeda. Since we’ve only been broadcasting for about 100 years, it will be a long time before anyone there might receive them.
Suppose we wanted to travel to Andromeda. Using our current propulsion technology, a space shuttle that left Earth would take about 75 billion years to reach Andromeda. If we were able to travel at the speed of light (which is impossible given Special Relativity), it would still take 2.5 million years to get there. And as galaxies go, Andromeda is our next door neighbor.
In spite of these obstacles, we should not stop looking. It could be that other civilizations are much more advanced and may have other communications technologies that are superior to ours. Some of those civilizations could have been around much longer than the human race, and may have been searching for other life forms millions of years before the human race appeared on the Earth.
Another possibility is that they don’t want to disclose their existence for a variety of reasons.
There’s another possibility, however. I’m convinced that if an advanced civilization ever looked at us, they’d consider us a barbaric and backward society and not worth the effort. These potential visitors would only have to review our history of wars, genocide, and violence to determine that there’s no intelligent life down here. They’d probably decide to let natural selection takes its course.