chances of aliens out there

Before the admins come in and yell scifi or pseudoscience, im not saying that aliens visited earth i am argueing that there are many many other planets in our galaxy let alone the universe that are habitable like earth.

Look at our prerequisites for life.

Thje first is water, supposedly when the earth formed there was very little, but after a number of comets hitting us there was enough ice and water. Now apparently early on in the universe there were tons of comets colliding into tons of planets.

The next prerequisite is oxygen or breathable air (this is assuming they are oxygen breathing and not methane breathing (one advantage being they dont smoke XD) or CO2 like plants), and since comets hit the planet assuming the planet is close enough to a star, the water would evaporate and there would be oxygen.

The second being i suppose methane gas and an atmosphere and apparently i n the beginning of our planet there wer elots of volcanos which is a standard for most planets, look at those giant volcanoes on amrs for example.

So we have the oxygen, water, and atmosphere. and now there are the prerequisites for life. All that is needed are for the basic enzymes to form (which if u are familiar with thatexperiment by scientists to recreate the beginning of the world you will see it only took a few months to get a number of familiar enzymes)

And dont forget an iron core which is also a very very common element even in asteroids.

So really, all that is necessary for life supporting planets is to be close to the star, have volcanos, and get hit by comets. And all of those were in large supply when our planet was formed.

so when you think about it, we cannot be the only habitable planet in the galaxy because it is not that difficult for a habitable planet to be created.

I am not proposing aliens have visited earth, i am not even proposing sentiant alien beings, i am proposing that there are a large number of planets that are very habitable.

 

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And many here will concur with you as I do. I come from the Andromeda galaxy you see so I know that you are correct!

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You're thinking of life-forms as they exist on earth- believing oxygen, water etc are the only required elements for life. Try conceiving of a different kind of life.

 

That was what i was thinking. But to be honest, we have not visited another planet inhabited by life so we really dont have some very good parameters about where soemthing can or cant live.

Like 50 years ago we thought that no organisms could live in temperatures above 120 plus degrees because their enzymes would break down, but than they found bacteria in geysers in yellowstone that thrived in 150+ degree environments.

So until we find organisms that expand our parameters to what you propose we have to settle for looking for planets that have similar charecteristics of earth.

 

Formula's for life existing elsewhere are usually pretty screwed. I still haven't seen the formula for The universe suddenly appearing from nothing as energy, for energy deciding mysteriously to formulate into matter and for that matter to mysteriously decide to create life. I'm pretty sure the changes for those events are beyond astronomical, that they would make life occurring in more than one place in the universe even more astronomical.

 

Define life please.

 

jpappl i think it is pretty easily to tell the difference between a pebble and a bacteria.

it can eat, it can screw/clone, and it can die.

Theres my redneck's definition of life.

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Life being sentience, the capability to observe. Something which a rock doesn't do or can ever be. (* unless it's refined into materials, turned into a computer and programmed to simulate life)

 

when a computer becomes depressed and commits suicide is the day i believe that it is alive.

 

Yes. Well I was responding to Stryder who is claiming that the chances of life developing on other planets is extremely unlikely.

But thanks for your interpretation.

I think we will find life is much more commonplace, but not what we would consider intelligent life.

I am pretty sure they found it on mars in the 70's, decided not to tell us.

I think that life is spread throughout the universe and there could be species millions of years more advanced then us.

So there may be some nanoprobe in our airspace right now and we wouldn't even know it.

 

Well that definition will drastically reduce the number of planets with life.

However, with the sheer numbers involved that still IMO will leave a crapload of planets that will have life. What that would look like who knows.

 

Fraggle,

The obstacles to being visited is the greatest reason to exclude being visited. What we now know, leaves it a near impossibility.

So we are left with some magic of course. Magical aliens.

We would have to assume that if we are or have been visited, they have somehow found a way around the laws. Different dimensions etc could also be a possibility.

I don't claim to know the answer to this.

Recently, there have been proposals of ways to send nano sized probes near the speed of light. Whether that ever becomes a reality is unknown. But if we are where we are technologically. Where will we be in 500 years. Considering the last 200.

There are a lot of obstacles in the way of that as well. But if we make it that far on our current course. Then it could get interesting.

 

Remarks similar to the following appear in almost every thread dealing with the possibility of life elsewhere in the universe.

Such views are due to lots of SciFi knowledge & very little (if any) knowledge of biochemistry. The chemistry of life must allow for a large number of very complex molecules. Silicon, which also has a valence of 4, allows for a large number of complex molecules. However, silicon compounds are insoluble in most liquids & few (if any) are gaseous or liquid.

Consider the requirements of cells, which are the basic building blocks of living organisms. Each has a semipermeable membrane maintaining the integrity of the basic structure while allowing for the interchange of chemical compounds with the surrounding environment. No set of silicon compounds is suitable for the construction of these basic building blocks. Silicon compounds tend to be far more stable than comparable carbon compounds, making processes like photosynthesis, digestion, & growth of a living organism difficult if not impossible.

An advanced technological culture might be able to create life forms (or something similar) based on a different biochemistry than that existing on Earth. Such life forms would never evolve without an intelligent designer & fabricator.

BTW: Evolution & some basic laws of physics put limitations on life forms. Examples.

• Huge SciFi insects are not possible due to their method of obtaining oxygen. Large creatures require a circulatory system based on a liquid like blood, which implies the need for lungs & a heart or something similar.
  
  
• There are reasons why various mythological creatures like centaurs & flying horses are almost certain not to evolve. Especially the latter.
  
  
• Elephants & other very large land dwelling animals must have legs which are thick & short in comparison with animals like deer.

 

Let's say "yes" for a moment.
There are "alien" life forms out there. Alien to what? To our life form. But it's not alien to universe.
So what? How are we going to make sure? We can not go or send a robot out there, not yet. Obviously they are not sending anything to here, unless if we are not imagining our top scientists, artists or TV personalities are actually working for, absorbed by an alien life form. Such as DNA, what!
We can not go there, they can not come here, because space is expanding faster than the speed of light, and nothing we know is allowed to travel faster than photon. If anything, any knowledge, any civilization can ever break this rule, it should also be so advanced in this universe; either us or "aliens".
We could not solve many of our problems as humanity, but we surely understood that everything in nature is consist of different interrelated mechanisms in different levels. In order to control these technologies, one must have spent some spare time in his/her evolution history and develop some disciplines.
The existence is not improbable, yet first contact is unlikely.

 

“
You're thinking of life-forms as they exist on earth- believing oxygen, water etc are the only required elements for life. Try conceiving of a different kind of life.
”

Exactly. Also, the elements Oxygen, Iron, and Carbon are stable, and quite prevalent in the Earth's crust, so there's no reason to assume they would not be equally as prevalent in a rocky planet orbiting another 2nd generation star, similar to our Sun.

While some life forms here on Earth have copper based blood, and there's nothing to stop this being expressed more widely on another planet, there are solid reasons why apex predators do not have copper based blood, and that, again, is down to chemistry, and iron based blood is better at doing it's job.

Comments like the quote from Soulstar show a bit of a B-Movie attitude. We need SciFa, not SciFi!

 

http://en.wikipedia.org/wiki/The_Great_Filter

>>The Great Filter is an implication of the failure to observe any extraterrestrial life, despite considerable effort (the Fermi paradox). One possible explanation is that there is something, the Great Filter, which acts to reduce the great number of potential sites to the tiny number of intelligent species actually observed (currently just one: ours). It might work either by one or more barriers to the evolution of intelligent life, or a high probability of self-destruction. The main counter-intuitive conclusion of this observation is that the easier it was for life to evolve to our stage, the bleaker our future chances probably are.<<

 

There is the possibility that there are other universes too. It is likely that there is life in at least two of them.