For generations humans have wondered and fantasized about whether there is other intelligent life in the universe. There are now two major projects underway to try to find an answer. More than 50 years ago a group of scientists began a project that became known as the Search for Extraterrestrial Intelligence (SETI), which listens for signals from space. More recently (in 2009) NASA launched the Kepler satellite to look for planets in a small sector of our galaxy. Both of these projects speculated that there should be intelligent life out there someplace just because of the vast numbers involved in the universe. Astronomers estimate that our galaxy, the Milky Way, contains hundreds of billions of stars-some estimate up to 400 billion. And they estimate that there are billions of galaxies-some estimates run from 10 billion to almost 200 billion. So if the average galaxy-and they consider our galaxy average-contains 100 billion stars, that would mean that there may be 1 billion trillion stars. And that’s just the observable universe. It could be even larger.
What we are interested in is planets that may have life on them like Earth. So far the Kepler satellite has found over 2000 planets in a very small sample of our galaxy using relatively crude techniques. And of those planets they found about two dozen so far that may be habitable. That is, they occupy what is referred to as “Goldilocks zones” of their stars where liquid water and perhaps “life as we think we know it” could exist. Dr. Frank Drake, one of the founders of SETI, developed an equation to estimate the number of habitable planets. It consists of seven factors-some astronomical (like the fraction of stars with planets) and some speculative (like the fraction of habitable planets that have intelligent life). Using this equation astronomers have estimated that there could be between 10 to 40 billion habitable planets in our galaxy alone.
That sounds like an awful lot! So let’s try a simplistic sanity test. If we just consider our galaxy, which is 120,000 light-years across, for now we can forget about all the other billions of galaxies that are too far away to consider ever contacting. So let’s do the numbers. Starting with 400 billion stars in the Milky Way, astronomers have estimated that one of every five Sun-like stars in the Milky Way might have a habitable planet. Suppose we were a lot more pessimistic. If only one in 1000 (0.1%) stars have planets similar to Earth (that is rocky, not gaseous, not too big, not too small, not too close or too far from their star) that would give us 400 million candidate planets to start. Now suppose only one in 1000 of those planets supports life. That would narrow it down to 400,000 planets. If only one in 1000 of those planets have intelligent life, that would leave 400 planets comparable to Earth. Now that’s not billions, but it would sure be interesting if there really are hundreds of other planets with intelligent life like earth (hopefully more intelligent) in our galaxy alone. By the way, all of these analyses are focused on Earth-like conditions that support carbon-based life forms – like humans. What makes us think that this is the only possible form for intelligent life??
Now it can get really interesting if we think about how advanced this other intelligent life could be. Scientists claim the universe was formed 13 to 14 billion years ago and that the earth was formed about 4 billion years ago. But modern humans only evolved about 100,000 years ago and it is only in the last 50 years that we have developed the technologies to explore and begin to understand the universe. Even if we assume that the evolution of life on earth is typical, chances are that there are some planets that evolved earlier. If they are only 10% older than Earth, that would give them an extra 400,000 years to develop intelligent life and advanced technologies. That’s almost 100 times the entire history of civilization on earth! So even if only a small fraction of those hundreds of earthlike planets are older than the Earth, there could be many that are far more advanced than we are.
So if there are hundreds, if not billions, of earthlike planets with intelligent life-some more advanced than us-why haven’t we found evidence of them, or haven’t they found us? Time and distance are significant obstacles. Astronomers have estimated the nearest habitable planet maybe 10 to 12 light years away, while most are hundreds, even thousands of light years away. A light year is approximately 6 trillion miles. Scientists do not believe that objects with any significant mass can travel anywhere near the speed of light. But suppose an advanced civilization had the ability to travel in space at 1/10 the speed of light– which would be approximately 70 million miles an hour (which is almost 3000 times faster than our spaceships today!). Then it would take over 100 years to travel from what we think maybe the nearest habitable planet and thousands of years from most of the other planets. So if space travel is not practical why have we not heard from them or they heard from us, since radio signals travel at the speed of light. In the case of earth, it has only been about 50 years or so when we started generating enough radio signal energy (television, radar, etc.) to be detectable from space. But now with the emergence cable and satellite communications we are actually becoming less detectable. This could also be true of other advanced planets. So the SETI project may be doomed to failure. It is also possible that older habitable planets may have lost their civilization-either from natural or civilization causes. After all, humans have almost destroyed Earth a couple times and many believe we are still doing it.
Another problem is that everything is a long time ago! Most of what we see of the universe happened millions and even hundreds of millions of years ago because of the vast distances that light has to travel. Even in our own galaxy, most of the stars we see are thousands of light years away. So, many of the stars we see (and any planets that they may have) could be dying or dead by now. Of course, new stars and planets could be forming during this time as well.
SO WHAT MIGHT THIS ALL MEAN?
• There may be and may have been many planets with intelligent life.
• Many of these planets with intelligent life may be or may have been more advanced than that on Earth.
• Earth’s civilization may never be able to travel to planets that have intelligent life.
• Other planets that have intelligent life – even more advanced than Earth’s – may never be able to travel to Earth – or any other planet with intelligent life.
• Other planets with intelligent life may have already died – along with their civilizations.
• The universe that we see is not the universe that currently exists.
• Earth’s civilization may be destined to live alone in the universe.
• The laws of nature may not be what we believe them to be.
• Somebody/something may really be in charge of it all – and have a plan!!!
All Rights Reserved © 2016 Henry P. Mitchell