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Conditions for life on planets


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#1 W13

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Posted 11 January 2017 - 05:01 PM

We're searching the galaxy for signs of life. If an exoplanet is in the habitable zone, we try to detect its atmosphere and other characteristics to satisfy the criteria for life. There's one planet where conditions have been perfect for life for billions of years: Earth. So how come life has only evolved once? What I mean is: why does all life on Earth have the same LUCA? Why is there a tree of life? Why not a forest of life? At the cellular level, why is life so undifferentiated?

 

If something happens in this universe once (such as inception of life), is it bound to happen again (and again) due to the universe being so vast with so many planets?

 

Are conditions not ideal now for new life to begin on Earth? If so, conditions were perfect at one point - so why did life only originate once?

 

If life did originate several times, and we do indeed live in a forest of life, why are living things so similar that their origin is indistinguishable? Is this the only combination (amino acids, lipid bilayer, DNA, etc) that works?

 

And finally: how does this affect our search for life on other planets?


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#2 Pkpete

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Posted 11 January 2017 - 05:57 PM

It's an interesting question, because we have a very narrow view of what is considered life. That bias can have a considerable impact on such a search.


Edited by Pkpete, 11 January 2017 - 06:01 PM.

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#3 Matchu

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Posted 11 January 2017 - 05:59 PM

why does all life on Earth have the same LUCA? Why is there a tree of life? Why not a forest of life? At the cellular level, why is life so undifferentiated?


Because it was really successful from an evolutionary standpoint. All complex organisms, from humans to trees to insects, use the same genetic code as the 'blueprint' for enzyme and protein production. We use it in different ways, sure, but we all have that blueprint. At some point long, long ago our LUCA evolved a primitive version of it, possibly just RNA, and dominated its environment. It's quite possible there was a 'forest' of basic organisms, but none of them had the sticking power of our ancestor.

It's also perfeectly possible for new life to arise, evolution is an ongoing process. But it would not only have to compete with its environment, but also other life forms. Our ancestors likely had the advantage of only really having to deal with the environment.

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#4 Yoto32

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Posted 11 January 2017 - 06:19 PM

I think it's highly unlikely that life hasn't evolved independently on other planets. Considering how unfathomably huge the universe is, it just doesn't seem statistically possible that we're the ONLY life in the universe.

 

Now, what would alien life look like, and would we ever be able to contact them is another question entirely.


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#5 Evf

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Posted 12 January 2017 - 01:34 AM

Maybe the aliens are scared of our memes and don't want to associate with us?


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#6 The duck

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Posted 12 January 2017 - 04:32 AM

Maybe the aliens are scared of our memes and don't want to associate with us?

If aliens would exist I'm certain they would make some nice reality shows monitoring the behaviour of certain groups of people!


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#7 Southampton9

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Posted 12 January 2017 - 08:28 AM

I think we might find basic states of things like potential materials that could be transferred as a water source or the like. The strategic positioning of the earth with Mars recieving a lot of the clutter from the asteroid belt and Jupiter acting like a vaccum and the temperature positioning of the earth I'd find it very difficult to see it happening elsewhere though other natural means.


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#8 Murdoc

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Posted 12 January 2017 - 03:36 PM

Why do we assume extraterrestrial life can only form in the same kind of conditions we did? Sure, perhaps it's the easiest way to approach the question of "is anything else out there?", but I believe that's the reason we are yet to find 'proof'. What if other beings just exist in ways/states we cannot comprehend? Maybe that's why we never have or even never will. It's like sticking your head into a pond at the end of the road and expecting to see, I don't know, a giraffe swimming around.
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#9 W13

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Posted 13 January 2017 - 07:26 PM

Life as we know it may exist: replicating individual collections of complexity who can interact with each other and the environment. 

 

But the probability of intelligent life is so unfathomably little, it's like finding an alien named Greg. I mean, just to reach the point of aliens having names requires so many other infinitely low probability events. I think it's the same for intelligent life: it's so far down the alley of low probability events that it may not exist in the universe. 

 

We are often naive in our thinking about life's trajectory and progression. There are a gajillion species on Earth and how many are "intelligent"? Out of all the humans, how many (after how long) developed to a point of being called "intelligent"? Also I'd argue you'd find "life" able to randomly/accidentally shoot radio signals into space before you find actual intelligent life that can think for themselves.


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#10 Matchu

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Posted 13 January 2017 - 08:55 PM

But the probability of intelligent life is so unfathomably little


No it's not. It's almost certain. The Milky Way galaxy has a lot of stars, lowest estimate 100 billion, maybe as many as 400 billion. Latest research also says planets are very, very common to find around stars.

So, let's say there's 200billion stars, of which 75% have planets. If every one of those solar systems only has one planet, that's 150 billion planets. We know from our own solar system, and studies of others, that the multiple planets is perfectly possible. But let's be conservative and use that figure. What you're saying is basically life occured once, out of 150,000,000,000 chances, which just sounds ridiculous.

All of that is based on our own galaxy. In the 'observable universe' (which isn't even the whole universe, it's just the bit we can see), we think there's about 200 billion galaxies. Now they come in all sizes, some larger than ours, some smaller. But let's say they're the same for this purpose.

The Earth has roughly 8,700,000 different species, give or take 1,300,000. The number of planets in the tiny slice of the Universe we can see, using our conservative, low ball methods is 30,000,000,000,000,000,000,000. They're not even remotely close.

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#11 Murdoc

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Posted 14 January 2017 - 03:50 PM

What do people think about whether or not we should make contact with aliens? Disaster movies and video games aside, I agree with the likes of Hawking that this would be a bad idea if human history is anything to go by. Both in terms of our treatment of each other and those other animals we share Earth with. If another infinitely more advanced civilisation randomly decided to we could we wiped out just like that.

Perhaps we're the cosmic equivalent of ants. No one pays attention to us because we're that insignificant in their eyes.
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#12 The duck

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Posted 14 January 2017 - 04:01 PM

Did we ever find resources in space that we're currently harvesting on a regular basis? I know we're pumping so much money into the NASA and such but I'm interested in the (real) returns so far (as in, amount of kg of gold returned for instance).


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#13 Kevinn

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Posted 14 January 2017 - 04:10 PM

Life as we know it evolved based on the environment of Earth. Why can't live elsewhere except those that evolved based on those environments?

 

We've seen microorganisms evolve at the bottom reaches of the ocean living on methane gas. So why not other planets with different atmospheres?


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#14 Pkpete

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Posted 14 January 2017 - 04:13 PM

Did we ever find resources in space that we're currently harvesting on a regular basis? I know we're pumping so much money into the NASA and such but I'm interested in the (real) returns so far (as in, amount of kg of gold returned for instance).

 

Private companies have actually discussed mineral extraction from asteroids. As expensive as the process may be, it seems like it could be very profitable. Part of me wonders if this is the endgame of Elon Musk's program, as it would be massively more profitable than merely atmospheric tourism for the super wealthy. Check this out: 

 

https://en.wikipedia...tential_targets

 

Keep in mind that as time goes on, improvements to technology would inevitably make the process far more cost effective.


Edited by Pkpete, 14 January 2017 - 04:15 PM.

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#15 W13

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Posted Yesterday, 09:09 AM

Did we ever find resources in space that we're currently harvesting on a regular basis? I know we're pumping so much money into the NASA and such but I'm interested in the (real) returns so far (as in, amount of kg of gold returned for instance).

 

The returns from NASA are priceless. They aren't always direct, such as a mined asteroid, but they're there. Loads of technologies developed by NASA have found themselves into everyday lives. Also things like GPS, farming imaging, weather forecasting, and deforestation/pollution measurement wouldn't even be possible without the contributions of NASA into the scientific community. And don't forget the countless experiments being conducted on the ISS from every field of science. You can read some of the benefits here: https://www.nasa.gov...e/benefits.html     

 

 

See Also: https://en.wikipedia...edirect_Mission  <-- not sure why they don't bring the asteroid boulder into Earth orbit instead and park it next to the ISS. Then, astronauts can go out, drill it, take samples for study on the ISS itself or to be taken down to Earth.


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#16 Yoto32

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Posted Yesterday, 11:14 AM

What do people think about whether or not we should make contact with aliens? Disaster movies and video games aside, I agree with the likes of Hawking that this would be a bad idea if human history is anything to go by. Both in terms of our treatment of each other and those other animals we share Earth with. If another infinitely more advanced civilisation randomly decided to we could we wiped out just like that.

Perhaps we're the cosmic equivalent of ants. No one pays attention to us because we're that insignificant in their eyes.

I like to think that maybe we're the advanced species, the first life to master space travel. Dangerous thinking perhaps, most definitely arrogant, but it does explain why nobody else has contacted us. I assume that most advanced civilizations aren't able to get off their home planet, or if they do, can't get past their immediate solar system. Space is so large, maybe life needs to develop on two different planets for different intelligent species to cross each other.


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#17 Murdoc

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Posted Yesterday, 01:38 PM

 

What do people think about whether or not we should make contact with aliens? Disaster movies and video games aside, I agree with the likes of Hawking that this would be a bad idea if human history is anything to go by. Both in terms of our treatment of each other and those other animals we share Earth with. If another infinitely more advanced civilisation randomly decided to we could we wiped out just like that.

Perhaps we're the cosmic equivalent of ants. No one pays attention to us because we're that insignificant in their eyes.

I like to think that maybe we're the advanced species, the first life to master space travel. Dangerous thinking perhaps, most definitely arrogant, but it does explain why nobody else has contacted us. I assume that most advanced civilizations aren't able to get off their home planet, or if they do, can't get past their immediate solar system. Space is so large, maybe life needs to develop on two different planets for different intelligent species to cross each other.

 

You've reminded me of this: http://i.imgur.com/hINj1xf.png :lol:


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#18 Yoto32

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Posted Yesterday, 02:25 PM

 

I like to think that maybe we're the advanced species, the first life to master space travel. Dangerous thinking perhaps, most definitely arrogant, but it does explain why nobody else has contacted us. I assume that most advanced civilizations aren't able to get off their home planet, or if they do, can't get past their immediate solar system. Space is so large, maybe life needs to develop on two different planets for different intelligent species to cross each other.

You've reminded me of this: http://i.imgur.com/hINj1xf.png :lol:

 

And that reminds me of this story, and that sub in general.


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#19 W13

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Posted Today, 04:20 AM

 

What do people think about whether or not we should make contact with aliens? Disaster movies and video games aside, I agree with the likes of Hawking that this would be a bad idea if human history is anything to go by. Both in terms of our treatment of each other and those other animals we share Earth with. If another infinitely more advanced civilisation randomly decided to we could we wiped out just like that.

Perhaps we're the cosmic equivalent of ants. No one pays attention to us because we're that insignificant in their eyes.

I like to think that maybe we're the advanced species, the first life to master space travel. Dangerous thinking perhaps, most definitely arrogant, but it does explain why nobody else has contacted us. I assume that most advanced civilizations aren't able to get off their home planet, or if they do, can't get past their immediate solar system. Space is so large, maybe life needs to develop on two different planets for different intelligent species to cross each other.

 

 

I hear you. And you may be right, but let me throw this cat into the bag:

 

Earth is 4.5 billion years old. Life started 3.5 billion years ago. The first apes appeared just 50 million years ago. We went from ape to hominid at about 6 million years ago. And we went from chest-beating, rock-hurling, mud-hutters to space travel in barely 10,000 years.  

 

Let's assume it takes 4.5 billion years on a goldilocks exoplanet with life to reach space travel, like it did on Earth. (Bombshell) The universe is 13.8 billion years old with the first planets being formed around 13 billion years ago. (Head-explosion hand gesture).

 

So, let's say that 13 .. (err.. screw it, let's give it another 1 billion years) ... 12 billion years ago, thousands of life-supporting planets formed. Now we add 4.5 billion years to get life to space-travel: 12 - 4.5 = 7.5 billion years ago, thousands of aliens started venturing out into space.

 

Let's come back to Earth for a second. Ok, we've just barely started venturing out to space. We're just dipping our toes in still. In the next 500 years, our technology will be so advanced, nobody on Earth can even guess at it with any accuracy. But I can tell you that at the trajectory it is going, in the next 500 years, we would be fairly space-faring with communities all over the solar system and with technologies similar to today's sci-fi. (I may be falling way short due to lack of imagination, but Elon Musk is already planning million-person cities on Mars ffs).

 

Back to the thousands of alien planets. It is 7.5 billion years ago from today plus 1000 years and they're experimenting with faster-than-light travel. Now give that civilization an extra billion years to become as advanced as gods and wipe each other out in an epic intergalactic war where they hurl black-holes at each other and turn each other's planets into neutron stars. That is STILL 6.5 billion years ago. Earth does not even exist yet! Trillions of new planets formed during that time and life on those planets has already had a headstart compared to us.

 

Also, don't forget: the universe is expanding. Back 7.5 billion years ago, the universe was way closer together. So, that would've allowed aliens to interact with each other much easier. They wouldn't even need exotic faster-than-light travel to reach each other. They'd be able to use normal rocket technology and be able to reach like 50 nearby star systems within a few months time. Can you imagine how all this collaboration and sharing of technologies would've helped accelerate their advancement?

 

Now, with the light from all those billions of years reaching our telescopes today, the universe SHOULD be swarming with detectable signs of life - but it isn't. There's only one explanation: life hasn't spawned on any planet other than our own.

 

It's more impossible that there's no detectable signs of life despite there being trillions of planets with life, than Earth being the only place in the universe with life. You can't have a gajillion planets - all with stupider life than us. It's impossible. This is why I'm skeptical that there's any life in the universe besides on Earth.   If you have a gajillion slot machines, you'd expect millions of them to hit the jackpot. But looks like there's only one slot machine, and it did hit the jackpot.


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#20 Matchu

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Posted Today, 06:53 AM

<snip>


You're talking about the Fermi Paradox, "where is everybody?". That leads onto the 'Great Filter', the idea that getting to human levels of intelligence and technology is relatively common, but getting beyond that is not. So the species splits the atom, but then blow themselves up in nuclear war. Or they use up all their resources before discovering space travel. Or they discover space travel, but not FTL. No one can quite agree where such a filter would fall, some think the filter is behind humanity, and we're one of the first to breach it.

I also think there's a certain cynicism to how we view these theoretical aliens. If you're capable of Universe wide travelling, or even galaxy wide, you're not going to have the same notions as we humans do now. Traditional wars on Earth were fought over wants and needs, "you have this land / resource I want, I'm going to take it from you". When you can fly across the stars, there's little reason to fight because everything's available to you. Oil? Hop over to the next solar system. Short on food? There's a lovely flora planet 300 LY away, let's go. Same reason I disagree with Hawking, I wouldn't travel to Australia to stand on ants, no species is going to fly 1 million LYs to destroy a race so insignificant they haven't got off the first planet properly yet.
 

Back 7.5 billion years ago, the universe was way closer together. So, that would've allowed aliens to interact with each other much easier. They wouldn't even need exotic faster-than-light travel to reach each other.

No, they would. When people say the Universe was "nearer", it's still vastly bigger than anything achievable by Earth standards. Even if you go back to within hundreds of thousands of years of the Big Bang (before stars had even formed), the Universe is still huge. Don't forget also that the expansion of the Universe is the expansion of space, not the galaxies or stars (at least at the moment, but that's another topic). So travelling across a galaxy a billion years ago would take the same time as today.

e:

See Also: https://en.wikipedia...edirect_Mission <-- not sure why they don't bring the asteroid boulder into Earth orbit instead and park it next to the ISS. Then, astronauts can go out, drill it, take samples for study on the ISS itself or to be taken down to Earth.

ISS isn't in a stable orbit.

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