By David Ward
It does not have to be completely dark to see three beautiful planets up there in the summer evening sky. From right to left, they are Jupiter (really bright), Mars (kind of bright) and Saturn (not so bright). The three are pretty much in a straight line and that line defines the plane of our solar system. All the planets revolve around the sun in a flat circle, and on a balmy summer evening you can see that circle stretching across the sky.
Do you ever feel cheated that we only have one moon? Jupiter, by the way, has 67 that we know of and probably a lot more. You do not have to feel bad about it any more because astronomers have discovered that we actually have two! The second one is not exactly a moon they are calling it a “quasi-moon.”
Only about the size of a football field, it shadows the earth in its orbit around the sun, never straying more than 100 earth moon distances us. The word is the earth’s gravitational field captured it about a century ago and it is likely to be hanging around with us for centuries more.
Summer is a great time to gaze in wonder at the Milky Way, our home galaxy in the vast cosmos. When it gets really dark, which is kind of late this time of year, look for a hazy light stretching from north to south across the sky. The Greek philosopher Aristotle thought that glow was caused by the vapors of stars burning in our upper atmosphere. He sure got that one wrong! The upper atmosphere is not even 100 miles up. The billions of stars that make the glow from the Milky Way are 36,000,000,000,000,000 miles or even further away!
Why no calls?
Recently an undergraduate student at Cornell University came up with a new answer to an old question. Why hasn’t E.T. called us already? This quandary, known as the Fermi paradox, has perplexed astronomers for decades. If there are alien civilizations out there why have we not gotten even so much as a text message from them?
The new line of reasoning goes something like this: The first radio transmission powerful enough to leave the earth was Adolf Hitler speaking at the 1936 Olympic Games in Berlin. That was not really a great way to introduce the human race to potential intelligent aliens eavesdropping on us. That broadcast and countless others sent since that time have been traveling away from the earth at the speed of light.
Now, 80 years later, they have traveled 80 light years away from home in a bubble 160 light years across. One light year equals 6,000,000,000,000 miles. In that bubble are an estimated 8,531 stars and 2,326 discovered exoplanets and probably many more undiscovered ones. That sounds like a lot of planets, but even so the chances of one of them being earth-like and having intelligent beings on it is vanishingly slim.
By 750 years from now that bubble of radio and television broadcasts will be 1,500 light years across and contain 22,000,000 stars and who knows how many planets. Out of that number, maybe somebody will hear us and give us a call to say hello. Of course, it will take another 750 years for the call to get back to us so we really cannot expect to hear from E.T. for another 1,500 years.
I have my own answer as to why E.T. has not called yet. I know this kind of puts a damper on all those fun science fiction movies we like to watch and it could be considered a huge waste of space, but I do not think there is anyone out there to pick up. If there is, they are so far away that we will not hear from them for tens of thousands of years and by that time we probably will not be around so it really will not matter much anyway.
Earth is such a special place and our existence here is a result of such highly improbable circumstances and absolutely amazing coincidences that it is unlikely to be more than a handful of planets like ours in all the hundreds of billions of stars in our galaxy.
In early July the earth will reach that point in its orbit known as aphelion, our furthest distance from the sun. We will also be traveling at the slowest speed for the year, which gives us plenty of time to relax and enjoy these beautiful days and nights of early summer.
