How do we know that there isnt life on the planets that we know of already? We assume that Water and Air must be present but couldnt it be possible that life exists in a different dimension than our own or are just invisible to what we can view with our limited view of things?

Because none of the known planets fulfill the requirements of life as we know it.

One shouldn't think that the terrestrial life is the only possible form of life (unless proven so), but anything else is pure speculation for now.

__________________
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

How do we know? Simple, we don't. We haven't found any evidence of life, but then we've just barely begun looking. Ask again in a thousand years or so, when we've more thoroughly explored our solar system.

__________________
"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
"The Mayan symbol for "book" looks a lot like a triple hamburger, but I've never seen them claiming it as proof the Mayans had Big Macs." - KaiYeves
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

We don't know that there isn't any life on the worlds we know of - IIRC the evidence for or against is still somewhat ambiguous for Mars. but as Noclevername said, we haven't really been able to look properly yet.

life finds a way. we have been surpised everywere on our planet, fish in freezing cold waters devolping anti freeze in there blood. insects that can survive in space. light made in a living creature. flying around the world and back without insturments. we live in an amazing world filled with wonders. that survive in the harshed condtions.



the chance that life could survive i think is thier. but if it is there no ones for sure.

I just realized I should have posted this in Life in Space, my mistake

I totally agree, thats why it seems almost impossible that some form of life wouldnt be present on all planets?

What you're forgetting is that the life that napolean finds so amazingly varied and adaptable all evolved on our own already habitable world. Sure, you can find microbes that can survive in liquid that is essentially hot battery acid, but I'm not sure that those microbes would be there today if they hadn't evolved from life that was originally adapted to much more habitable conditions.

My bold.
If that is the case (I have no opinion one way or the other), how could we possible know about it?

As far as life in this dimension, air (such as oxygen and nitrogen) is not a requirement, but all life, as we know it, does require water, at least in some part of its life cycle. This means that it is still possible that there is life elsewhere in this solar system, such as on Mars or on Jupiter's moon Callisto.

__________________
At night the stars put on a show for free (Carole King)

One Earth, One Sky - IYA 2009
All moderation in purple

Yeah, but many of the more complex hardy organisms have evolved from organisms that lived a much more hospitable environment. And even the more hospitable environments in our Solar System beyond the Earth are far more inhospitable to life than even the most harsh places on the Earth.

One has bear in mind that most of the time people have been overtly optimistic (only a few decades ago a simple plant life on Mars was considered a pessimistic view). On the other hand, I don't think the "rare Earth" hypothesis is true (as you said, life finds its way if it is given a chance). And I agree with the proponents of the hypothesis that microbial life should be common granted that abiogenesis is a relatively simple process.

__________________
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

Would you like to know about planets in OUR solar system? or a different "dimension" you have me a bit lost.

"We" haven't been anywhere yet.

We've sent a few simple probe robots with limited capabilities to the other planets, but haven't been to any other planet yet.

Nothin's run by any of the cameras so far but that's not saying much....

Ahem - Jupiter´s moon Europa is the one with the liquid water.

No, it is thought that Ganymede and Callisto also have subsurface oceans, though Europa is thought to have better conditions for possible life. From here:

http://en.wikipedia.org/wiki/Callist...e_in_the_ocean

Like with Europa and Ganymede, the idea has been brought up that extraterrestrial microbial life may exist in the salty ocean under the Callistoan surface.[18] However the conditions for life appear to be less favourable on Callisto than on Europa. The principal reasons are: the lack of contact with rocky material and lower heat flux from the interior of Callisto.[18] Scientist Torrence Johnson said the following about comparing the odds of life on Callisto with the odds on other Galilean moons:[41]

“ The basic ingredients for life -- what we call 'pre-biotic chemistry' -- are abundant in many solar system objects, such as comets, asteroids and icy moons. Biologists believe liquid water and energy are then needed to actually support life, so it's exciting to find another place where we might have liquid water. But, energy is another matter, and currently, Callisto's ocean is only being heated by radioactive elements, whereas Europa has tidal energy as well, from its greater proximity to Jupiter. ”

Based on the considerations mentioned above and on other scientific observations, it is thought that of all of Jupiter's Galilean moons, Europa has the greatest chance of supporting microbial life.

__________________
I say there is an invisible elf in my backyard. How do you prove that I am wrong?

Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

Assume that exists invisible life in different dimension.

Well, what is easier to get evidence about?

• Life like our own.
• Invisible life in different dimension.

All should be clear now, why we search for life like our own. We search for second Earth - ultimate Holy Grail of astrobiology - because we know, at least theroetically, how we would spot our own world from distance and detect biosignatures.

But of course any planet with any unstable atmosphere with components that cannot coexist for long (geologically speaking) would be very interesting.

__________________
Sanity is overrated.
Butterfly.

Exactly. The evidence seems to suggest that:

1. The stuff to make life is ubiquitous, even existing in interstellar clouds.
2. The basic chemistry of life is pretty easy, with nucleotides self-assembling in test tubes.

. . . but,

3. Getting an actual, self-sustaining reaction (that is, life) going is very, very difficult.

Keep in mind, no scientist has ever managed to create actual life in a test tube. If it was really so easy to do, as some people seem to think it is, so easy that life existed on Europa and Mars and on a substantial percentage of the extrasolar planets we've found, then I think we'd be able to do it in a test tube and study it and narrow the parameters a bit. But we can't (yet) because it isn't easy.

Life doesn't just spring up wherever the building blocks are available. If it did, then we'd see it everywhere. I'm not exactly sure what it takes to get life started. I suspect it takes gentle running water, silicate crystals (basically, clay), and an inland sea full of nutrients. Regardless, life is rare and special, though I look forward to the day when we find it apart from Earth.

The good news is that:

4. once life gets started, it is apparently pretty tenacious. This is why you can find Earth-based life living in battery acid. But you apparently can't start life out in battery acid.

That's my humble opinion.

In a strange, twisted sort of way, the "life should be everywhere" train of thought is the same as that used by creationists. There's a funny video on youtube of a creationist using a jar of peanut butter to disprove evolution. "If evolution is true," he says, "then why isn't life evolving inside this jar of peanut butter?" The jar of peanut butter is just like Europa, or certain extrasolar planets. True, Earth-based life would be more than happy in a jar or on Europa, but that doesn't mean it can get started there. There are still a few things in the Universe that are truly miraculous, and getting life started is one of them.

I'm not sure about that. It could be life is easy to get going, but it takes a long time (and so doesn't reproduce in the lab). It may be we have just not found the right conditions yet. You might be right, but I'm keeping an open mind.

As far as why isn't life springing up everywhere now, I suspect that once life is established, that it prevents the creation of new life forms from pre-biotic materials - for example, the current bacteria just eat up the "inland sea full of nutrients".

There is also some ideas that in fact life might have originated not in gentle conditions, but in the more extreme, chemical and energy rich areas that today would be considered extreme (your hot battery acid).
One article
Second article
Third article

__________________
At night the stars put on a show for free (Carole King)

One Earth, One Sky - IYA 2009
All moderation in purple

Well, that's as may be, but remember that (From http://www.nineplanets.org/callisto.html)

This suggests that, if there is any liquid water on Callisto, it is either (a) in very small pools; or (b) buried so deep under the ice that 4 billion years of meteoritic bombardment has not succeeded in causing any crustal movement. We know about the Europan ocean because of the effect it has on the surface.

Thus, not only is Europa a better candidate for ET life, but, assuming the existence of ET life on both moons, we are more likely to find it on Europa than Callisto. Ganymede appears to be somewhere in between, but perhaps a little more like Callisto than Europa.

__________________
The quarrelsome oarsmen were rowing,
The great violinist was bowing;
But how is the sage
To tell, from the page:
Was it pigs or seeds that were sowing?

Well, actually it may not be so hard, but who would fund the project? There doesn't seem to be much point, apart from demonstrating that it can be done.

The biggest challenges that I see are (a) becoming sufficiently certain of the prevailaing conditions in which life first arose on Earth (while we have a good idea of the conditions in a global sense, it is conceivable that life arose within a specific microclimate for which we currently have no data); and (b) demonstrating conclusively that what you end up with is novel life and not contamination in the lab. If you're going to make a soup out of amino acids, nucleotides, sugars, fatty acids, phospholipids and so on, you can't exactly autoclave it without altering its chemistry. And such a mixture would be a very rich microbial growth medium.

__________________
The quarrelsome oarsmen were rowing,
The great violinist was bowing;
But how is the sage
To tell, from the page:
Was it pigs or seeds that were sowing?

Viruses have already been made in labs. It will only be a few years before simple free living cells are made artificially. It will be very interesting to see just how simple a cell can be and still function as a living organism. It could give us many hints about what early life on earth was like.

Obviously life in our own dimension would be the most probable but I would say that it is possible that there are dimensions that we cannot see with our limited spectrum. Quantum theorists pretty much agree that existence may share multiple dimensions? As for life on Planets that we can see, it seems to me that life adapts out of its surroundings and that all life seems to consume another organism or animal to survive? Even energy and gasses consume one another right? Ex Black Hole It would seem as well that every planet has the possibility of that same consumption? My personal opinion is that life is a force that is all around the universe but with varied forms of interaction? Plants are alive but you wouldnt know it to look at one.

While some versions of string theory postulate many dimensions, we will only ever be able to see four (three of space + one of time). The additional dimensions are postulated to be "rolled up" so tightly that they exist in scales smaller than the Planck length (10^-35 m or thereabouts) and thus will never be accessible to our investigation.

If there are other dimensions that have a significant size, we would very likely be aware of them already.

I'm not sure what you mean here. While the sensitivity of our eyes is limited, we have insruments that can observe phenomena from radio waves all the away up to gamma rays. That's pretty much the whole EM spectrum.

That'll be String Theorists. But they don't agree on how many. They do agree, however, that if there are extra dimensions, there must be some mechanism that prevents us from seeing them.

Life adapts to its surroundings.

Well, yeah. Except plants. And photosynthetic bacteria. And cyanobacteria. And certain types of extremophiles (chemotrophs) that live around black smokers. But apart from that, all life consumes other life.

Er, no. Not really.

Eh?

Erm, that's a bit of an extrapolation. On what do you base this proposal?

Er, well, yes I would. If a plant is green it's alive. If it's brown then it's either dead or dormant. Look at the same plant once a week for a year and then try and tell me "Plants are alive but you wouldnt know it to look at one".

__________________
The quarrelsome oarsmen were rowing,
The great violinist was bowing;
But how is the sage
To tell, from the page:
Was it pigs or seeds that were sowing?

(bold mine)

>Nitpick< ...might be only a few years... >Nitpick<

__________________
"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
"The Mayan symbol for "book" looks a lot like a triple hamburger, but I've never seen them claiming it as proof the Mayans had Big Macs." - KaiYeves
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

This is one of these things where a lot hinges on the definition of life. For example some people claim life has already been created in the lab with synthetic viruses, but most people don't see viruses as being alive and so don't count that. I think we will soon see a variety of simple synthetic life forms that won't meet everyone's definition of being alive and there will be a (probably fairly short) period of time before everyone is satisfied. So the period of time before synthetic life is developed will depend a lot on how you define life and what you would regard as cheating when you make it. Some people will accept a franken cell with an artificial genome as synthetic life while that won't be good enough for others.

But you are certainly right that I shouldn't have said it will only be a few years, there is no way I can know that. I should have said it will probably only be a few years.

All Matter is made up of atoms whether its a rock, plant or a human. The only thing that sets the two apart is our cognitive sense of our surroundings, and that may exist for plants etc.. as well? Of course theres no proof but there must be some force of energy that enables our brains to realize our environment. Recent Coma experiments show that an electrical stimulation of the brain can jump start a vegetative state.

I was maunly eluding to String Theory, I stand corrected) As for the spectrum Im simply saying that our vision is based on isible light from OUR Sun right? Which is roughly 5500K , what if another planets light was a different temperature & spectrum? Or would our instruments pick it up? Or perhaps there could be another reason we can only see whats in our dimension?

Of course, we don't just have telescopes that can detect visible light which we can see, we have radio telescopes, x-ray telescopes, UV telescopes, infrared telescopes, gamma ray telescopes, we pretty much can detect electromagnetic waves of any frequency.

The peak wavelength of light emmitted by a star is determined by its temperature, which is fairly easy to have a handle on. Stars pretty much cannot emit light beyond ultraviolet as a peak wavelength, but either way no matter what kind of light a star emits we can pick it up if the signal is strong enough.

That's a bit of a word salad. I kinda think you're throwing around the term dimension without fully realising its meaning

__________________
"Bessie Braddock to Churchill "Winston, your drunk!"
Churchill: "Bessie, you're ugly, and tomorrow morning I shall be sober""
the solar system

I'm kind of glad I'm not the only one confused by that post. I thought I might be losing it.

__________________
The quarrelsome oarsmen were rowing,
The great violinist was bowing;
But how is the sage
To tell, from the page:
Was it pigs or seeds that were sowing?

Some certain people like believing in invisible life in another dimension without evidence.

__________________
My Astrophotography Gallery
Solar System Imaging Simulator

Yes, like Van Rijn's back yard!

__________________
The quarrelsome oarsmen were rowing,
The great violinist was bowing;
But how is the sage
To tell, from the page:
Was it pigs or seeds that were sowing?

Dimension= measureable factor. Time, length, etc. Coliver, you may be looking for a word like universe, space, plane of existence, etc. A dimension is not a place, it's how you measure parts of a place.

__________________
"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
"The Mayan symbol for "book" looks a lot like a triple hamburger, but I've never seen them claiming it as proof the Mayans had Big Macs." - KaiYeves
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

They could be Elves couldnt they

Yes, perhaps Plane of Existence would be a better description. Im just suggesting that we may not know Alien life even if we saw it?