The odds of winning the lottery are astronomical, but compared to seeing a UFO their actually pretty good. I have seen several objects whisking through the air that I couldn't identify. The UFOs I'm referring to are the ones with carbon-based life-forms on board. When one considers the complexity of the events that need to occur in order for complex, multicelluar life to propagate on another planet it becomes unlikely that intelligent life exists elsewhere in the galaxy. However, if intelligent, extraterrestrial life-forms do exist, then the same set of physical laws that apply to us would also apply to them. The basic laws of physics remain constant throughout the universe.
These alien life-forms would come from a watery planet. Their biological characteristics and the materials they use and consume will be similar to those found here on Earth. These life-forms will not be mystical, or ghost like in appearance. They will not walk on water, nor will they have unknown, limitless powers. They will not be “Transformers,” constructed of metal skeletons, integrated circuits and have petroleum based fluids for blood. No, they will be carbon-based, biological organisms. They may have some different attributes, but they will consume organic materials, breathe some form of air and excrete waste.
Because of the vast distances that separate Earth from other star systems the only way for an intelligent, extraterrestrial life-form to have reached Earth is with a spaceship capable of traversing across the galaxy at the speed of light. Otherwise distance becomes too great a barrier to breach. This is no small feat considering many of our own physicists believe it is not possible for an object with mass to accelerate to the speed of light.
Many of us have heard stories of UFOs suddenly appearing and then disappearing in a flash. I find those stories a little far-fetched because of a little thing called g-force. Primarily, g-force is the effects of acceleration on the human body (Usually shown as, 1g, 2g, etc). One doesn't just arrive and then whisk away in a split second without suffering some profound biological setbacks; like your head and body suddenly becoming part of your space chair. Acceleration and deceleration must be gradual.
The speed of light is 671 million MPH. The human body can endure an acceleration comfort level of 1g over a prolonged period. At that rate it would take 347 days to get a spaceship up to light speed and an additional 347 days to decelerate. At the speed of light the damage caused by space debris, micrometeorites and space-dust would be catastrophic to the spaceship. It would need to be made of an indestructible material or have some special type of shielding. Imagine a pebble hitting your windshield at 40 MPH. Now, imagine the damage that same pebble would do if it hit your windshield at the speed of light.
In addition to traveling at the speed of light there would be numerous other problems to overcome as well. They would have health and psychological issues to consider as well as long periods without gravity. They would also need a renewable fuel source and the storage capacity to hold enough supplies for a very long, long voyage. These are just a few of the problems they would need to resolve. The journey to Earth from the nearest star system would be approximately 9-10 years, round-trip.
The closest star system is Alpha Centauri; a 3 star system. Below are the star systems closest to our own solar system with the distance in light years* listed beside them:
· Alpha Centauri, 4.3
· Barnard's Star, 6.0
· Sirius, 8.7
· Epsilon Eridani, 10.8
· Tau Ceti, 11.8
· Gliese 581, 20.3
Of these above star systems Gliese 581 is the one that astronomers feel offers the best chance of having a planet capable of supporting complex, multicelluar life. At the speed of light it would take more than 40.6 years, round-trip, to complete the journey. It may not be possible for an intelligent, biological organism to endure deep space for that long. Therefore, the best hope, in terms of distance, is the Alpha Centauri, or Barnard’s Star system. Should intelligent life exist there they could reach Earth in a mere 4-7 years, Earth time.
If by chance intelligent life found a way to prosper on another planet, then we must consider other things. Is this alien society's technology advanced enough to build spaceships capable of traveling at the speed of light? Does their culture support space exploration? Life is only the beginning. Intelligent life flying around the galaxy in Star-ships is an entirely different matter.
In conclusion: It becomes unlikely that intelligent life exists elsewhere in the galaxy when one considers all the variables required for life too prosper on another planet. After considering numerous factors and given the vast distance between star systems and Earth, I believe it is unlikely that intelligent, extraterrestrial life has ever visited our planet. Proponents, who believe intelligent, alien life-forms have visited Earth, will continue to argue its validity. They will point their fingers at various, government agency's worldwide and shout, “Cover up." In the end, their conclusions will be purely speculative. To date no hard evidence exists that supports their premise. This is not to say that life, intelligent or otherwise, does not exist elsewhere in the galaxy. Intelligent life may very well be flourishing on other planets, but distance and time barriers may forever keep us separated. If by chance an alien species has passed our way they must have noticed all the neon signs, pollution spewing smokestacks and oil spills. I imagine Earth looked like a giant spitball twirling in space. They probably looked at each other and said, "Hey, that looks like a good place to take a dump, pull over."
*A light year is the distance light travels in one year. (671million x 24 x 365 = distance in miles light travels in one year)