Wow! Signal: Extraterrestrial

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Has anyone ever actually proven the assumption that life can only exist on planets similar to earth? Even on our own planet there are species that thrive in extremes of cold and heat and where there's little light, oxygen or water and other supposedly vital substances and conditions. The only absolute necessity is energy and even planets with no sunlight could supply geothermal energy.


Of course this isn't something you can go ahead and write a mathematical proof of, but certain assumptions are made. At extremely low temperatures, chemical reactions of almost all types cannot happen. One thing we do know is that without chemical reactions, there is no life, so you can set a lowest temperature cut off point depending on what kind of reactions you think life needs. The general opinion is that life needs quite complex reactions using water, so the temperature needs to be at least above 0.01C. -220C is such a low temperature I'm not sure any chemical reaction would happen at all.

You get a similar thing with high temperatures. When the temperature gets high, chaos reigns. Life represents some kind of order. Too much heat and order is lost. Any temperature above 100C becomes very difficult for life to survive in already. This is why somewhere like Venus (400C or something) is not considered possible for life to exist.

All in all, it is pretty safe to assume the following are requirements for life:

-Reasonable temperature - Probably 0 up to 100 C or for the really extreme among you maybe -100 up to 200 C (though you would only expect microbes at such low temperatures.
-Low gravity (always good to not be being crushed)
-Low pressure (again, good not to be squashed)
-A source of energy
-Shielding from radiation (life doesn't work if radiation is randomly smashing bonds up everywhere)
-Time (for life to evolve in)
-Carbon or silicon (basically the only atoms that allow complex chemistry)
-Lack of toxic compounds
-Reasonable weather (see Venus)
-Liquid water (slightly questionable requirement, but all life on Earth uses it)

The requirements for life are actually pretty specific. The only reason people expect life to be around in other places is from the sheer number of stars, not because making life is easy or statistically likely.
Hi,

Actually in chernobyl nuclear plant the radiation is being eaten by algae and moss to make energy rather than usual food source. And then cockroach they can survive extreme radiation. Not to mention in ocean there is multicellular life such as Jellyfish and few more which live in pressures which would kill a human being in a second.

Next, toxic compound would not be a concern at all actually, near hydrothermal vents a lot of poisonous gases are emitted and snails survive.
Next, the hydrothermal vents produce a lot of heat and pressure yet snail adapts by having a metal shell. Source of Energy is easy but look near marianna trench were the temperatures reach -75 and pressure exceeds 513000 LBS. This places don't have too much energy but they make it via the water rocks. and such.
:| I was going to respond the same thing about the 'required' conditions life needed. I mean - we haven't landed a human on another planet at all much less conquered at least our solar system, so the only knowledge is of life on Earth. It'd be pretty ignorant to say that life only can exist in certain conditions without many facts to support the statement.
I just want to make it clear what I mean by radiation, pressure and toxic compounds, by throwing a few examples out.

Radiation: Being too close to a gamma rays burst or other extreme radiation event - It's far less likely for there to be life in and around the centre (<- yeah that's how you spell it lol) of our galaxy for mainly this reason. Big stars around there live and die fast and throw out enough radiation to sterilize planets of all but the deepest ocean life and to completely change the chemistry of the atmosphere and surface, not to mention that nasty Sagittarius A* throwing out all kinds of nastiness at times.

Pressure: Think of the pressures in the internals of planets like Jupiter.

Toxins: Again, I would point to Venus. Sulfuric acid is highly toxic to life.

Life is order and control over complex reactions. Anything that introduces random chaos in large doses is going to be bad for the chances of life occurring. Keep in mind that for complex life to occur, it's expected extremely long periods of relative stability are required in order for evolution to take place. Almost every time a scientist mentions the possibility of life somewhere outside of Earth, they tend to mean extremely low odds of micro-organisms surviving there.

Also, Darwin's theory of evolution, although based on a single case study, is based upon sound and universal science and is expected to hold for extrasolar worlds. It would appear to require *at least* hundreds of millions of years to create anything intelligent. This is the kind of life we have to talk about if you want them to be smart enough to create 2.2 gigawatt radio transmissions. You have to ask if a planet is located well enough for this to happen. We are tucked away from most of the nastiness of the Milky Way. Is that planet?
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Keep in mind Earth was very violent when life first appeared here.

Oh yea, and center* :3
Mats, your right in many aspects.

anyway, maybe an advanced alien civilization could have recently colonized the planet and have been broadcasting signals as a signal to galaxy or some kind to shower their arrival there and to tell the galaxy using their traditional methods or maybe they have been testing weapons.
Life is order and control over complex reactions. Anything that introduces random chaos in large doses is going to be bad for the chances of life occurring.

I tend to have opposing views in that I feel that life can only be spontaneously generated in highly chaotic circumstances.

Like Lumkin hints at, it is early life that eventually terraformed Earth and made it into what we consider habitable today, early earth is supposed to have been highly "toxic" though some form of life found it quite homely. Sulphur used to be more readily available in early Earth and many bacteria even today utilize sulphur instead of oxygen in their metabolic functions...

Granted, high levels of radiation is deadly to just about all life, but moderate levels can be a mutagenic agent that can spur evolution.

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Mabry we should reconsider our definition of life. All of the posts above assume earth-like life: warm/cold blooded animals that breath oxygen and are carbon-based.

Considering how large out universe is, and how diverse life on earth is, I would say that there could be life anywhere. It is unpredictable the forms life can take. We must assume there has to be life out there that is absolutely nothing like us, just based on how big the universe is.

A grand example of this is a fish that lives in the frozen oceans of the Antarctic, yet thrives (no blood).

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warm/cold blooded animals that breath oxygen and are carbon-based.


There are some assumptions about life that must hold true. One of these it that is must utilize complex chemistry. I mean, life basically is complex chemistry. You could almost define life as 'naturally occurring complex chemistry.' Given this, finding non-carbon or non-silicon based life seems impossible, as these are the only two elements that allow for chemistry of such complexity.

many bacteria even today utilize sulphur instead of oxygen in their metabolic functions.


As far as I know, there is no living thing on Earth that can continue to live without oxygen.

I tend to have opposing views in that I feel that life can only be spontaneously generated in highly chaotic circumstances.


Is this just something you 'feel' or do you have some proper reasons to think this? I'm not criticizing what you said, but just interested what the proper reasons are, if you have any?

Obligate anaerobic bacteria - bacteria which actually find even low concentrations of oxygen to be toxic. - also the reason that we pour hydrogen peroxide on wounds.


As far as the chaos thing, there are theories, but nothing proven either way (since nobody was there to record it). I just don't see the "spark of life" being caused by stagnation. - most complex chemical reactions require a catalyst, some element or energy source that needs to be introduced in order for a reaction to begin, but once the reaction has started it can sometimes continue by itself after the catalyst has been removed (like setting a twig on fire, it originally requires application of heat, but can continue burning by it's own energy after you remove the lighter).

http://en.wikipedia.org/wiki/Abiogenesis - this page has a lot of theories, some of them about how early earth's atmosphere was more likely to foster spontaneous generation than today's. It seems that no one theory has stuck at this point.

http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment - if you want to follow up on an interesting experiment.

http://www.usnews.com/news/articles/2013/05/24/life-discovered-in-earths-coldest-environment-yet extremophiles are interesting.

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Very interesting post @newbieg. Thanks for the info! : )

I read through a very interesting biochemistry book a couple of years ago that proposed a theory of early life that really got me hooked. The general premise was that life evolved from rocks. Obviously, I can't go into the detail he did in the book in the post, however, the key proposal was that the earliest life would have been rocks.

Yes that's right.

Rocks.

He proposed a method whereby certain rocks could obtain a method of memory and adaptation to the environment, on an extremely basic level. The author was quite an experienced and influential biochemist and to be honest, his arguments were extremely plausible.
Very interesting post @newbieg. Thanks for the info! : )

I read through a very interesting biochemistry book a couple of years ago that proposed a theory of early life that really got me hooked. The general premise was that life evolved from rocks. Obviously, I can't go into the detail he did in the book in the post, however, the key proposal was that the earliest life would have been rocks.

Yes that's right.

Rocks.

He proposed a method whereby certain rocks could obtain a method of memory and adaptation to the environment, on an extremely basic level. The author was quite an experienced and influential biochemist and to be honest, his arguments were extremely plausible.

Are you sure the theory wasn't that life evolved inside of rocks? Do you remember the name of the book or the author?
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closed account (G30oGNh0)
I'm not well versed in Biology, Chemistry or Physics, so I can't really have an opinion on the subject, but I will say this.

Human beings can only comprehend it's senses. Reality is the compilation of all your senses working together to create an image of said universe. Just because we have only experienced life on Earth isn't to say life cannot exist anywhere else, nothing is to say different parts of the universe utilizes different rules of Physics, Biology or Chemistry. After all, no matter what information is given to us by the universe, the final point of this information is yourself, your own consciousness, you see, what you want to see. Information is lost, warped and corrupted by the human mind, we can, and will only understand, what we are able to understand.

Throughout history scientists have had a theory which worked then, but as time continues the theory couldn't of been further from the truth as new idea's and observations came to light. Knowledge on Earth is still very, very young.

Just because man has been to the moon, doesn't mean man has conquered the universe. Life on Earth is a mere fetus compared to the universe itself, all it takes is for a planet somewhere to be a billion years older than our own, which is nothing on the universal scale.

In my ideal universe, nothing is fact, nothing is solid like stone, the universe is water, ever changing to it's container.

Edit:

Before people start bashing me, this is all purely philosophical.
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@htirwin - Found the book: http://www.bookdepository.co.uk/book/9780688069711?redirected=true&gclid=CKyPucTpgrwCFSbHtAodUzgAtA

nothing is to say different parts of the universe utilizes different rules of Physics, Biology or Chemistry


Since whereever we have looked in the universe, it looks roughly the same, it seems that the laws of physics actually are the same everywhere. Even a tiny change to constants like the coupling constant, pi or electron mass would change everything drastically. This is not what we see.

Throughout history scientists have had a theory which worked then, but as time continues the theory couldn't of been further from the truth as new idea's and observations came to light.


This is also simply not true. Stuff like Newton's theory of gravity is not incorrect science, but only a special case. As we have got better at science, we are learning the more general cases.
closed account (G30oGNh0)
Since whereever we have looked in the universe


How does one look in the universe? We cannot see the universe from the outside, even Newton said this, he said we can only figure it out by being 'inside the box' how it all works in reality, only God can know.

Stuff like Newton's theory of gravity is not incorrect science, but only a special case.


If your special case is that time is slower through different area's of space affected by gravity, then yes, however Newton's theory is still very young, compared to how early humans perceived the world. A few hundred years is a very, very short time scale...People thought gravity is a force, now some are claiming it could be a particle. People said the world was flat, people say it's round. People thought we could never get up into space, we got to the moon at least, see my point? Perspectives are always changing..
People thought gravity is a force, now some are claiming it could be a particle.


Gravity is still considered a force and forever will be. Force exchange is mediated through particles. These two points are not contradictory; each is necessary for the other. It's not just some are claiming it could be a particle, but that a particle (the graviton) mediates interactions between the gravitational field and others. This is accepted theory.

People said the world was flat, people say it's round.


It is an urban myth that the world is was once thought to be flat.

People thought we could never get up into space, we got to the moon at least, see my point? Perspectives are always changing..


You must be careful when you look to the past to try and predict the future. We are now so far in the science that some limits have been reached and other limits are known. These limits are known to be limits mathematically. There is a huge difference between saying I don't think we can get to the moon and saying here is a mathematical proof of why that is impossible.


How does one look in the universe? We cannot see the universe from the outside, even Newton said this, he said we can only figure it out by being 'inside the box' how it all works in reality, only God can know.


This is not necessarily true. A deeper study of quantum mechanics may well throw up answer to not only how it all works in reality, but also why it works like that.
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closed account (G30oGNh0)
You are a clever guy Mats, you seem to certainly know you stuff but again I cannot have an opinion as I don't have any expertise in the required fields of science, I'm just relaying thoughts I have had about this subject, I am not claiming to be right. You have helped me understand a few things. The Graviton being one of them, maybe you can help me understand why particles are able to know when they are being watched to change it's properties?

I still don't think you are understanding the points I have been trying to make. You're being too factual, too rigid, recalling information which has been said to you from certain groups of people who believe it to be true. Don't take me for a tinfoil hat wearing, living in my moms basement stereotype, I just find too many similarities between science and religion, makes me hard to believe either. (Though I got further in Science than religion, I got to the second page of the Bible, I did try.) I think the universe has more in store than Science will be able to understand, more than the human mind will be able to understand. I believe nothing is as it seems.

Whether scientific theory does pan out and is one day able to explain this whole subject of reality and why we are here and how it all came to be and why alien species can't exist, the universe was one giant mistake and it all happened out of imperfections, I guess the human race has nothing else to live for, it's figured it all out. The universe would be no where near as exciting.

Then again will we ever get that far? Science was only ever created for military purposes, which ( I hope ) you were already aware of. We will end up killing ourselves before we ever get to reach such an answer.

No wonder aliens don't come down, they must be laughing at us from afar.

On a side note:

Another thing that has gotten to me about Science is it's expenditure. The amount of money ( I hate the word, I should say 'resources'. Money is printed, resources are used and rarely recycled ) are spent on endeavors I'm sure millions of the homeless and starving of our fellow brother, sisters and children of this world would call pointless.

$25.4 billion dollars ( $145 billion in 2008 ) was spent sending man to the moon. Was it worth it? Maybe...Would it not be worth more to see every person given a good life here on Earth? As most won't live to see the day we can can finally settle a new Earth.
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You have helped me understand a few things. The Graviton being one of them


Cool. :)

still don't think you are understanding the points I have been trying to make. You're being too factual, too rigid, recalling information which has been said to you from certain groups of people who believe it to be true.
I just find too many similarities between science and religion


Being factual is basically what separates science from religion. Plus, stuff that has come up in this topic so far is not really unknown science. We know a lot of things that dark matter and dark energy can't be.
and why alien species can't exist

I'm not sure where you heard this? But I think if you asked almost any scientist, they would say alien species almost definitely exist.
Science was only ever created for military purposes, which ( I hope ) you were already aware of.

I'm also not sure why you think this? Modern day science basically starts with Isaac Newton. He discovered a great deal of maths and science because he was curious about the world, not with military intent.
closed account (G30oGNh0)
Being factual is basically what separates science from religion.


I am right in saying both parties think they have a solid understanding? Fact is what? For religion it is words on paper, science fact is proof written on paper with a bit of maths to wrap it all up, but be aware proof is not a synonym for true.


As for the alien thing I used a strong word, I heard it was just highly highly improbable due to the maths for everything being right for life to exist. Even then it won't be the highly advanced life form, maybe just bacteria or micro organisms of some sort, nothing to warp space time and travel through wormholes etc etc.
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