life on other planets

[jephthah]

suppose there were another planet similar to earth in composition, temperature, and atmosphere.

(and given the bazillions of stars in the universe, the probability is quite high that, somewhere, there must be)

so, considering another earth-like planet with H2O, carbon, and oxygen... over a couple billion years ... what kind of life would evolve? why wouldn't it make sense that many of the life forms that would result, would be similiar to life forms that either once existed on earth in the past, or currently exist on earth today?

you know, mammal-like creatures like cows or mastadons. or reptile-like creatures like dinosaurs or crocodiles. or at least, your basic fish variants and plant life.

and the things that were different, they wouldn't necessarily be radically different from creatures that could conceivably be found on earth. like a pig-dog. or a lizard-bird. or something.

just a thought.

[GrimJack]

The reason that there would be no similarity is that each and every step was randomized right down to the whether or not the DNA would be left handed or right handed. Even given right-handed DNA with the same 4 components - there have been at least 4 'great' extinctions after which everything changed.

Just consider what was discovered in the Burgess Shale - many of those creatures no longer exist (see attached reconstruction pic). The largest living thing on earth is a fungus under a forest in Minnesota - what if fungi became the dominant life form? What is vibrating crystals were the dominant life form? Life on Earth is one long series of accidents that could never in the life of the universe be duplicated.

[NicAx64]

Life on Earth is one long series of accidents that could never in the life of the universe be duplicated.

I agree with this too. But you can't say probability is equals to zero.
so what is the distance to the next harmonic that we can find life.

[GrimJack]

Something to note:

researchers have confirmed the existence of 19,599 protein-coding genes in the human genome and identified another 2,188 DNA segments that are predicted to be protein-coding genes.
In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. The Human Genome Project has estimated that humans have between 20,000 and 25,000 genes.

Let's pretend that all genes are only 100 bases long and that there are 'only' 20,000 genes. It is estimated that only 1% of human genes contribute to the differences between people. This leaves us with 200 genes composed of 100 bases each and half of those are just duplicated so we are down to 100 genes with 100 bases which is the same as 100[TEX]^{100}[/TEX](my head hurts is 100[TEX]^{100}[/TEX] = 10[TEX]^{101}[/TEX] or 10[TEX]^{102}[/TEX]?). There are 31,556,926 seconds/year (use a sidereal year here) so 3 years are about 10[TEX]^8[/TEX] seconds so if on gene were changed each second it would take approximately 10[TEX]^{93}[/TEX] or 10[TEX]^{94}[/TEX] years to randomly duplicate a human. That is 10 followed by 93 zeros; the current estimates of the age of the universe is 1.4 X 10[TEX]^{9}[/TEX] years.

The myriad is 10[TEX]4[/TEX], or 10,000. By continuing with "one myriad," "two myriad," etc., Archimedes gets up to "one myriad myriads," which is 108, or a hundred million. He calls the numbers 10, 10[TEX]^2[/TEX], 10[TEX]^3[/TEX], 10[TEX]^4[/TEX], 10[TEX]^5[/TEX], 10[TEX]^6[/TEX], 10[TEX]^7[/TEX], and 10[TEX]^8[/TEX] the "first arithmon." The "second arithmon" takes him up to 10[TEX]^{16}[/TEX], and so on. For example, 10[TEX]^{26}[/TEX] would be the hundredth of the third arithmon, as 10[TEX]^{26}[/TEX] = 100 x 10[TEX]^{8+8+8}[/TEX]. After a myriad-myriad arithmons, he runs out of numbers again and calls this the end of the "first period." Adding more "periods," he finally stops at the fantastic number 10[tex]^{80,000,000,000,000,000}[/tex], which is a one followed by 80 quadrillion zeros. Archimedes calls it the "myriakis-myriostas periodu myriakis-myriston arithmon myriai myriades."

But I digress.

[Nick Evan]

like a pig-dog. or a lizard-bird. or something.

Or manbearpig

[jephthah]

hmmm. well, the OP is perfect example of why engineers don't make good biology students.

[Nick Evan]

hmmm. well, the OP is perfect example of why engineers don't make good biology students.

Erm.. You're the OP. Am I missing something are are you being a 'bong' again?

[jephthah]

:P

[Salem]

> suppose there were another planet similar to earth in composition, temperature, and atmosphere.
The atmosphere of primordial earth was not one you could live in.
There was no free oxygen, and a bunch of other stuff which would not help either.

Nor does life have to restrict itself to the surface.
http://en.wikipedia.org/wiki/Hydrothermal_vent
Of which the current favourite outside of earth seems to be
http://en.wikipedia.org/wiki/Europa_(moon)

Technological civilisations may indeed be rare, possibly even unique within say a single galaxy. One of the big hurdles being the maths needed to understand how radio works isn't that far removed from that needed to work out how nuclear fission works.
"Hey, we can talk to the universe - poof, and there was silence once more".

But my guess is microbial life is endemic.
http://en.wikipedia.org/wiki/Extremophile
Basic life can get a foothold in all sorts of places.
Liquid water + a bag of chemicals + an energy source (not necessarily a star) + time, and you're on your way.

[GrimJack]

When you visit Yellowstone Park (in the US, I am sure there are similar places elsewhere in the world(?)), you see these really, really hot springs that have a rainbow of colors leading from the source - those colors are the different varieties of extremophile that live at different temperatures and mineral saturations.

When these organisms were found living in harsh environments that would kill any other organism, scientists began trying to understand how they were able to survive. The proteins inside extremophiles each adapted to the habitat where the extremophile lived. It was discovered that each type of extremophile had enzymes that were resistant to extreme heat, saline, acids, high/low Ph, and high barometric pressure.
Since extremophiles use proteins in different ways than other microorganisms do, scientists are working on adding a sixth kingdom in the classification of life just for the extremophiles. This classification will be called archea and it will include all prokaryotic and eukaryotic extremophiles.

But I digressed.

We keep finding different forms of communication as we study the life forms we grew up with: elephants use sounds below our hearing to communicate, alligators use sounds above our hearing; Orcas are known to create sound sculptures that behave as discrete unitary (soliton) 'things' that are used to herd fish towards waiting hunters.

I guess the point I am, haphazardly, working towards is - would we even be able to 1) recognize intelligence; 2) communicate with it if it is so far out of our realm of experience that we have nothing in common. Think of the difficulties involved with just communicating with Helen Keller and we were 100% related.

The giant fungus I mentioned earlier - how could we discover whether or not it is intelligent? How would it discover if we were? Until recently, we thought that mushrooms were the organism when they are just the sexual organs of a much larger organism.

[jephthah]

okay, so i wasn't really trying to talk about advanced civilisations or human-like intelligent creatures, or any sort of SETI contact.

just merely in a general sense, why wouldn't life on an "earth-like" planet naturally evolve into creatures more or less "similar to" the life forms that have evolved here?

i vaguely understand the complexities of DNA, but there are so many potential combinations that just wouldnt work out on earth for a variety of reasons, evolution would guide the developing forms (in most part) to be suited for life on land or in water.

and yes i know that there are some bizarre lifeforms around oceanic vents sucking up sulfuric acid and whatnot, but we can just ignore the outliers -- like balloony-floating energy packets, or vibrating silicon crystals, or even giant fungi living under minnesota -- and think about the vast majority of land and ocean dwelling creatures.

because if the atmosphere was ~20% oxygen, and the surface contained 70% water with an average temperature around 20C give or take... then creatures that thrive on oxygen would exist, and most likely wander around the land masses drinking water and either laying eggs or weaning pups or whatever.

i still imagine that it wouldnt be all that radically different from what we have on earth. perhaps they would have "relatively" different thing, like maybe "manbearpigs" or "snuffaluffaguses" or bizarre flying insect/reptile combinations with skill saw blades on their heads maybe... but in a zoological sense, nothing ridiculously different than the wide variety of flora and fauna we have here on earth.

.

[Ezzaral]

Until recently, we thought that mushrooms were the organism when they are just the sexual organs of a much larger organism.

Eww, I stepped on a couple in my yard yesterday - I didn't know I was tromping on something's privates :icon_eek:

[GrimJack]

Sorry, I thought you wanted a thoughtful discussion.

[ithelp]

suppose there were another planet similar to earth in composition, temperature, and atmosphere.

(and given the bazillions of stars in the universe, the probability is quite high that, somewhere, there must be)

so, considering another earth-like planet with H2O, carbon, and oxygen... over a couple billion years ... what kind of life would evolve? why wouldn't it make sense that many of the life forms that would result, would be similiar to life forms that either once existed on earth in the past, or currently exist on earth today?

you know, mammal-like creatures like cows or mastadons. or reptile-like creatures like dinosaurs or crocodiles. or at least, your basic fish variants and plant life.

and the things that were different, they wouldn't necessarily be radically different from creatures that could conceivably be found on earth. like a pig-dog. or a lizard-bird. or something.

just a thought.

First of all you do not need water and oxygen for life , as long ADP and ATP type of complex molecule can be constructed , life can exist , I heard solar system planets except earth are thickly populated with aliens , but you need to know where to look for them , may be they are living underground in mars :-)

[sneekula]

I am thinking of the old time machine story, where people rather than pigs were raised for food.

[Ene Uran]

Imagine a planet where all the beings live by unbiased rules and pay their fair taxes.

[jlm699]

just merely in a general sense, why wouldn't life on an "earth-like" planet naturally evolve into creatures more or less "similar to" the life forms that have evolved here?

I guess the real question is: why would it?

Evolution is a very slow process, and even still multiple organisms can come from a common predecessor. Really evolution is all about the tiny mutations. Some mutations can work well for one animal but not for another of the same species. Each "strain" can go along and become an entirely new species depending on whether their mutations help them find mates and extend their progeny.

The fact remains however, that mutations are entirely random and there's no set rule for what adaptation will allow for the survival of one race of a species over the other. So maybe on another planet reptilian creatures would develop six legs instead of four to traverse a rockier terrain than Earth's, or arachnid-like creatures would no longer be arachnids and would only have two legs and would walk upright because they would be able to run crazy fast.

I agree with you that they would be "similar" in the fact that, yes they would most likely have "legs", "arms", a "head", etc. But there's plenty of ways that those features could be mutated and twisted so as to not appear like anything you've ever seen on Earth. So really, it's hard (for me) to imagine another planet with a habitable atmosphere that would develop lifeforms the same as ours.

My thoughts are further exacerbated by the fact that even the planet could have different concentrations of elements that would absolutely affect the way that life evolves and adapts.

[vegaseat]

If carbon would be all bound in solid insoluble rock, there wouldn't be any life.

[jephthah]

yah huh.

there would still be Pet Rocks.

you betcha.

[GrimJack]

If carbon would be all bound in solid insoluble rock, there wouldn't be any life.

There would not be any carbon-based life - maybe it would be silica-based.

[sneekula]

There would not be any carbon-based life - maybe it would be silica-based.

Wow, imagine the silicon units are breathing out silicon dioxide (sand)!

[jephthah]

like the carbon based units breathe out carbon?

[MosaicFuneral]

There would not be any carbon-based life - maybe it would be silica-based.

Like this Spongebob episode? As we can see, Spongebob and Patrick are ahead of their time, in many fields of science.

Wow, imagine the silicon units are breathing out silicon dioxide (sand)!

Why not Silicon dibromide?

[vegaseat]

Like this Spongebob episode? As we can see, Spongebob and Patrick are ahead of their time, in many fields of science.

Why not Silicon dibromide?

You mean silicon tetrabromide. Pretty corrosive stuff!

[Salem]

> Pretty corrosive stuff!
So is free oxygen, of which there is plenty about in the atmosphere, and which is toxic to some simpler lifeforms on Earth.

[jephthah]

oceanic vent dwelling bacteria breathe sulfuric hydroxide.