Absence of Aliens??

[susiebk]

http://dsc.discovery.com/news/2008/04/21/extra-terrestrial-life.html

ET Likely Doesn't Exist, Finds Math Model

Irene Klotz, Discovery News
 
April 21, 2008 -- Earth-like planets have relatively short windows of opportunity for life to evolve, making it highly doubtful intelligent beings exist elsewhere in the universe, according to newly published research based on a mathematical probability model.

Given the amount of time it has taken for human beings to evolve on Earth and the fact that the planet will no longer be habitable in a billion years or so when the sun brightens, Andrew Watson, with the United Kingdom's University of East Anglia in Norwich, says we are probably alone.

Earthlings overcame horrendous odds -- Watson pegs it at less than 0.01 percent over 4 billion years -- to achieve life. The harsh reality is that we don't have much time left.

No need to cash out your 401K or anything like that, but intelligent life appeared relatively late on the scene. Scientists believe the first life forms emerged four billion years ago. Humans have walked the planet for only the last 100,000 years or so.

"If we had evolved early … then even with a sample of one, we'd suspect that evolution from simple to complex and intelligent life was quite likely to occur. By contrast, we now believe that we evolved late in the habitable period," Watson said.

Earth's days are numbered. In another billion years or so, the sun will grow hotter and brighter, toasting our blue world beyond recognition.

"Earth's biosphere is now in its old age," Watson said.

"This has implications for our understanding of the likelihood of complex life and intelligence arising on any given planet," he added. "It suggests that our evolution is rather unlikely -- in fact, the timing of events is consistent with it being very rare indeed."

Watson pieced together his mathematical model by examining four critical stages that needed to occur in a particular order for intelligent life to arise on Earth. He then factored in how long a planet like Earth is suitable for habitation.

The steps include the emergence of single-celled bacteria, complex cells, specialized cells allowing for complex life forms and finally intelligent life with an established language.

"Complex life is separated from the simplest life forms by several very unlikely steps and therefore will be much less common. Intelligence is one step further, so it is much less common still," Watson said.

Based on the model, Watson said each stage of evolution had at most a 10 percent chance of occurring, and each development could manifest only after each proceeding step. Further, the evolutionary stepping-stones are spaced evenly throughout Earth's history, Watson added.

Unfortunately, by the time intelligent life reared, Earth was in its twilight years. Watson believes the same conditions would hold true on other habitable planets as well. His research is published Astrobiology magazine.

[brokeplex]

The odds are even steeper if you consider that terran sized planets probably naturally have an atmosphere that is Venusian in its density. A choked greenhouse world may be the norm for terran sized planets orbiting G stars.

It is only because the Earth has an abnormally large satellite that the atmosphere has been "thinned" over time. The tidal forces of the moon may also have contributed to the evolution of life and self aware intelligence, by creating a regularly changing environment conducive to evolution.

Life will probably be found in other stellar systems in world smaller than the Earth, perhaps mid sized moons orbiting gas giants.

[David In Indy]

Have you ever wondered if perhaps some of these UFO are actually us rather than aliens from other planets? What if at some point in time we figure out time travel? Maybe some of those UFOs are actually people from right here on earth travelling back in time to OUR time.

They even made a movie about this. One of the Star Trek movies was about the USS Enterprise going back in time to capture some humpback whales and take the animals back into the future with them.

[David In Indy]

Good points about the moon.  It would be sad, at least for me, if we were the only intelligent life in the universe.  I think it is one of those things that is hard to disprove since we can't possibly investigate or even know about every habitable planet.  Odds only go so far.  I am holding out hope!   

I am too!

If we exist, then why not others too?

Every time I look up at the starry sky I think about it. All those millions and MILLIONS of stars up there, most of them we cannot even see. Many of those stars probably have a solar system attached to them. It seems to me the chances are quite high at least some of those planets would have life on them. Even intelligent life in some cases.  During our history, there have been so many things we thought we knew, only to prove ourselves wrong later on in time. I think these mathematical calculations will probably be reworked someday and found to be incorrect.

Also, I think space goes on forever. There is no big brick wall out there with the words "The end of the universe" painted on a sign. And even if there was a big brick wall, or some sort of "end", what is on the other side? If the universe is sphere shaped as some suggest, what is on the outside of the sphere? And if space extends outwards forever, we cannot even begin to understand how many stars and planets actually exist. New stars and planets are created all the time. The light we see from most of those stars was emitted thousands of years ago and is just now reaching us. Most of us have problems comprehending this because we have difficulty understanding the concept of eternity and endlessness. But this doesn't mean it doesn't exist, it just means that human beings have not evolved enough to wrap our minds about something so vast, huge and endless.

[injest]

I think it is arrogant to think we are unique in the Universe

[brokeplex]

Have you ever wondered if perhaps some of these UFO are actually us rather than aliens from other planets? What if at some point in time we figure out time travel? Maybe some of those UFOs are actually people from right here on earth travelling back in time to OUR time.

They even made a movie about this. One of the Star Trek movies was about the USS Enterprise going back in time to capture some humpback whales and take the animals back into the future with them.

intersting point, and the Star Trek franchise made two time travel movies  Star Trek 4 ( the whales film) and Star Trek 8 ( where Enterprise E goes back to the mid 21st century to fight the BORG)

perhaps a more logical alternative along that line is the "multiverse" usage of alternate time lines. each time line has an infinite number of variants. the "alien" visitors are then visitors from another timeline.

[brokeplex]

I think it is arrogant to think we are unique in the Universe

in the absence of knowledge that we are not alone, we should perhaps say that we may be alone.

I suspect that in a galaxy with as many stars as ours, tens of thousands of light years across, it is unlikely that we are the only intelligent life forms. the question is, how do we communicate with much less visit these hypothetical life forms? without warp drive or the equivalent, the travel times between most stars is very, very long. and even messages at the speed of light may take hundreds or thousands of years to transit if the other intelligence is located in a stellar system that far away.

[delalluvia]

Didn't I just read a net news story that Stephen Hawkings now thinks there probably is low-level life on other planets?