Lonely Life? – Is Earth the only planet with life in our galaxy?

[Moontanman]

The most likely planet is venus. It has a mass closest to that of earth.

 

Most likely for what?

 

Mercury appears to not only look like the Earth's moon but it also seems to be weighted like it. This mercury may be venus's intended moon. It is not terribly far from capturing it.

 

I'm not sure what you mean by "weighted like it" Mercury is nothing like earth moon, Mercury is much denser than Earth's moon, it's resemblance to Earth's Moon is superficial at best. I would also like to ask what you mean by Mercury being Venus's intended moon, intended by whom? For Venus to capture Mercury would require some very complex interactions that are very improbable...

 

It would seem the mass of venus is slightly less than that of earth.

 

Venus is covered with CO2 and sulfuric acid. This is the environment in which life could spring up.

 

Could you elaborate on this?

 

There has to be some atmosphere on the planet.

 

Yes, the atmospheric pressure on Venus is 90 bar or about 90 times the pressure on the Earth, this atmosphere is comprised mostly of CO2 and Sulphuric acid at a temperature of around 860 degrees fahrenheit.

 

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

 

 

 

I think mars is just not a large enough body of mass to retain an atmosphere. The periodic table sort of dictates these things.

 

Mars no only has an atmosphere it is thought at one time it had much more than it has now. Now it's atmosphere is about 1/1000 bar and contains mostly CO2

 

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

 

Mars lost its magnetosphere 4 billion years ago,^[120] so the solar windinteracts directly with the Martian ionosphere, lowering the atmospheric density by stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars Express have detected ionised atmospheric particles trailing off into space behind Mars,^[120][121]and this atmospheric loss will be studied by the upcoming MAVEN orbiter. Compared to Earth, the atmosphere of Mars is quite rarefied. Atmospheric pressure on the surface today ranges from a low of 30 Pa (0.030 kPa) onOlympus Mons to over 1,155 Pa (1.155 kPa) in Hellas Planitia, with a mean pressure at the surface level of 600 Pa (0.60 kPa).^[122] The highest atmospheric density on Mars is equal to the density found 35 km^[123] above the Earth's surface. The resulting mean surface pressure is only 0.6% of that of the Earth (101.3 kPa). The scale height of the atmosphere is about 10.8 km,^[124] which is higher than Earth's (6 km) because the surface gravity of Mars is only about 38% of Earth's, an effect offset by both the lower temperature and 50% higher average molecular weight of the atmosphere of Mars. The atmosphere of Mars consists of about 95% carbon dioxide, 3% nitrogen, 1.6% argon and contains traces of oxygen and water.^[6] The atmosphere is quite dusty, containing particulates about 1.5 µm in diameter which give the Martian sky a tawny color when seen from the surface.^[125]

[Mr Monkeybat]

Interesting. Even though this goes into the direction of my thesis, I still have some concerns:

How sensitive are our detectors?

Would we really be able to to detect them?

The Wide-field Infrared Survey Explorer (WISE) http://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer has surveyed the entire sky. "WISE was not able to detect Kuiper belt objects, as their temperature is too low.^[17] It was able to detect any objects warmer than 70–100 Kelvins." I presume these habitats are supposed to be quite large. Perhaps uploaded robots could operate at lower temperatures if they use solid lubricants in there hinges like graphite. But even robots need a power source. The minimum size of a fusion reactor according to the late Bussard's optimistic Polywell designs is 100 megawatts not many fission reactors smaller than that either. Admittedly I would have to do more research to calculate at what distance 100 megawatts of infrared is visible. According to http://www.projectrho.com/public_html/rocket/spacewardetect.php the maneuvering thrusters on the space shuttle would be visible in the asteroid belt, most of the maths on his website seems sound.

 

 

Y

If the minerals are somehow the same in any habitable solar system, why should you (as an extraterrestrial) pick them up from another solar system instead of the one you are living in?

The same reason people and animals always migrate to new territory. Because the system you are living in is already settled so all its minerals are already owned by someone. This is of course assuming that interstellar travel is a viable option, I have not ruled out the other answer Jevon's paradox that people mainly just stay stuck on their home worlds maybe reverting to the Iron Age once fossil fuels run out.

 

 

I'm not sure what you mean by lack of evidence that any asteroids have been mined, how many have we really looked at closely? Some odd groves and such have been seen on the few we have looked at closely. I have my doubts about the need to mine asteroids for metals, I suggest that advanced civilizations would use mostly carbon to build their structures not metals. I'm sure metals would be needed but we tend to think of metals as the main ingredient in anything large we build but carbon fibers and nanotubes are superior in almost all ways to metal in building large scale structures, in zero G this advantage would be greatly magnified.

They look like they are covered by natural craters to me. 75% of asteroids are carbon rich, spectrographic observations of asteroids don't seem to indicate they have been selectively depleted of any element including carbon. Small planetoids like the Moon, Ganymede, Callisto etc could be easier to mine that asteroids because a little gravity can make many operations easier. I think these bodies have been observed enough to rule out artificial structures or earth moving on them.

 

 

The power problem is valid, without a power source there can be no ort cloud colonies... I have my doubts that such civilizations would consume all resources before moving on, the resources we are talking about is a great deal more vast than what we are used to dealing with, the idea that a civilization could or would colonise every star system in the galaxy in a few million years is based on the old idea that they would colonise planets, the ort cloud offers a few orders of magnitude more space and resources.

With a Conservative doubling time of 100 years it would only take 10,000 years for the human population equal the weight of the entire galaxy stars and all. It does not mater how vast the absolute size is, the exponential function will gobble it all up. 100 years is very conservative drop some people off on a planet seeded with life and isolated from Earths consumerism they will likely reproduce like the Amish doubling less than every 20 years. 5 doublings every century means your population is multiplied by 32 each century and 1024 every over century, 15 orders of magnitude every millennium. Those Women with a genetic predisposition to maximize their reproduction despite the temptations of consumerism will inevitably become a larger and larger section of humanity in the future by the almost tautological Darwinian fact that those that are better at reproducing become more numerous over time.

 

Obviously it unlikely that we begin digesting stars, we will presumably also be limited by the time it takes to cross interstellar space. Ignoring warp drives in a Von Nueman scenario a Daedalus type probe takes 80 years to come to a halt at the nearest star, give the robots a blind guess of one century to build all the necessary factories and robots to build more probes to send in every direction, and the expansion of Robot kind is expanding at 5 light years every two centuries even if they don't bother leap frogging each over. So then robots reach every corner of the galaxy in about 4 million years. By which time regardless of whether the computers are based on uploaded trans-humanists, evolved algorithms, or engineered software. The Darwinian nature of any self copying system will mean that those robots with copying errors that make them make the most copies and spread them most rapidly will cover the galaxy depleting all available mineral resources. Darwin always wins in the end.

 

 

Edit: that is weird this message came in further up the thread than a post I made earlier leading me to double post.

Edited April 29, 2013 by Mr Monkeybat

[Moontanman]

 

The Wide-field Infrared Survey Explorer (WISE) http://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer has surveyed the entire sky. "WISE was not able to detect Kuiper belt objects, as their temperature is too low.^[17] It was able to detect any objects warmer than 70–100 Kelvins." I presume these habitats are supposed to be quite large. Perhaps uploaded robots could operate at lower temperatures if they use solid lubricants in there hinges like graphite. But even robots need a power source. The minimum size of a fusion reactor according to the late Bussard's optimistic Polywell designs is 100 megawatts not many fission reactors smaller than that either. Admittedly I would have to do more research to calculate at what distance 100 megawatts of infrared is visible. According to http://www.projectrho.com/public_html/rocket/spacewardetect.php the maneuvering thrusters on the space shuttle would be visible in the asteroid belt, most of the maths on his website seems sound.

 

 

 

The same reason people and animals always migrate to new territory. Because the system you are living in is already settled so all its minerals are already owned by someone. This is of course assuming that interstellar travel is a viable option, I have not ruled out the other answer Jevon's paradox that people mainly just stay stuck on their home worlds maybe reverting to the Iron Age once fossil fuels run out.

 

 

 

They look like they are covered by natural craters to me. 75% of asteroids are carbon rich, spectrographic observations of asteroids don't seem to indicate they have been selectively depleted of any element including carbon. Small planetoids like the Moon, Ganymede, Callisto etc could be easier to mine that asteroids because a little gravity can make many operations easier. I think these bodies have been observed enough to rule out artificial structures or earth moving on them.

 

 

 

With a Conservative doubling time of 100 years it would only take 10,000 years for the human population equal the weight of the entire galaxy stars and all. It does not mater how vast the absolute size is, the exponential function will gobble it all up. 100 years is very conservative drop some people off on a planet seeded with life and isolated from Earths consumerism they will likely reproduce like the Amish doubling less than every 20 years. 5 doublings every century means your population is multiplied by 32 each century and 1024 every over century, 15 orders of magnitude every millennium. Those Women with a genetic predisposition to maximize their reproduction despite the temptations of consumerism will inevitably become a larger and larger section of humanity in the future by the almost tautological Darwinian fact that those that are better at reproducing become more numerous over time.

 

Obviously it unlikely that we begin digesting stars, we will presumably also be limited by the time it takes to cross interstellar space. Ignoring warp drives in a Von Nueman scenario a Daedalus type probe takes 80 years to come to a halt at the nearest star, give the robots a blind guess of one century to build all the necessary factories and robots to build more probes to send in every direction, and the expansion of Robot kind is expanding at 5 light years every two centuries even if they don't bother leap frogging each over. So then robots reach every corner of the galaxy in about 4 million years. By which time regardless of whether the computers are based on uploaded trans-humanists, evolved algorithms, or engineered software. The Darwinian nature of any self copying system will mean that those robots with copying errors that make them make the most copies and spread them most rapidly will cover the galaxy depleting all available mineral resources. Darwin always wins in the end.

 

 

Edit: that is weird this message came in further up the thread than a post I made earlier leading me to double post.

 

Your link http://www.projectrho.com/public_html/rocket/spacewardetect.php#id--Why_Not?_Let_me_count_the_ways--What_If_I_Run_Silent_And_Cold?

 

indicates a nuclear powered submarine or space ship using the same power could be detected to a range of 100 times the earth moon distance.

 

The oort cloud is considerably more distant than this theoretical maximum of 128 light seconds, the oort cloud extending to one light year. While i am not sure of all the details a nuclear powered spacecraft somewhere in the oort cloud would be virtually undetectable by any current detectors. I am assuming a distance of between 30 AU and 50,000 AU.

 

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

[Jens]

Thanks for the more detailed info about the detection possibilities!

The same reason people and animals always migrate to new territory. Because the system you are living in is already settled so all its minerals are already owned by someone. This is of course assuming that interstellar travel is a viable option, I have not ruled out the other answer Jevon's paradox that people mainly just stay stuck on their home worlds maybe reverting to the Iron Age once fossil fuels run out.

If you look at it from a less theoretical but a bit more practical level (even though it is still theory of course ): The issue is the energy. Traveling is highly energy expensive. It is difficult to overcome physical borders. (For example the fastest non-military aircrafts we as humans are using today are slower than those 20 years ago and thirty years in the past people predicted that we will fly to the moon for holiday trips by now.) Let's stay within known physics. Let's assume there is no miracle way of converting arbitrary mass fully into energy. So the most powerful energy resources for intelligent species are radition from the various suns (especially if you come close) and nuclear fusion. But taking atoms ("minerals") from somewhere outside the planet you are living is extremely energy consuming and time consuming - especially if you have to leave your solar system. It will never pay off -- especially if you count on clever ways to obtain what you need via chemical material improvements instead of beeing dependend on scare atoms. (and remember that hydrogen needed for nuclear fusion is not scare anyhow.) So any civilization would rather use something else than steel instead of carrying iron from another solar system. Or use more clever doted mixtures instead of beeing dependend on rare earth atoms. Note that I use the term atoms, since obtaining more atoms is the only thing you cannot do with chemistry. Nobody is interested in specific minerals, since you can all build them via chemical means with millions of times less energy than you need for interstellar travel.

 

So I think viable reasons to travel to the next solar system are to live on another planet or to do research but not for atoms (and definitely not for minerals).

Edited May 5, 2013 by Jens

[Moontanman]

Thanks for the more detailed info about the detection possibilities!

If you look at it from a less theoretical but a bit more practical level (even though it is still theory of course ): The issue is the energy. Traveling is highly energy expensive. It is difficult to overcome physical borders. (For example the fastest non-military aircrafts we as humans are using today are slower than those 20 years ago and thirty years in the past people predicted that we will fly to the moon for holiday trips by now.) Let's stay within known physics. Let's assume there is no miracle way of converting arbitrary mass fully into energy. So the most powerful energy resources for intelligent species are radition from the various suns (especially if you come close) and nuclear fusion. But taking atoms ("minerals") from somewhere outside the planet you are living is extremely energy consuming and time consuming - especially if you have to leave your solar system. It will never pay off -- especially if you count on clever ways to obtain what you need via chemical material improvements instead of beeing dependend on scare atoms. (and remember that hydrogen needed for nuclear fusion is not scare anyhow.) So any civilization would rather use something else than steel instead of carrying iron from another solar system. Or use more clever doted mixtures instead of beeing dependend on rare earth atoms. Note that I use the term atoms, since obtaining more atoms is the only thing you cannot do with chemistry. Nobody is interested in specific minerals, since you can all build them via chemical means with millions of times less energy than you need for interstellar travel.

 

So I think viable reasons to travel to the next solar system are to live on another planet or to do research but not for atoms (and definitely not for minerals).

 

I'm not sure why you would be arguing this, I am not suggesting bringing materials back from another solar system body to the Earth and certainly not bringing back anything from another Star System.

 

I was suggesting a nomadic existence starting out with colonies built in orbit around the home star using materials already in orbit around that star.

 

As technology advances and people become accustomed to living in space, and such colonies could be made to mimic a planet quite a bit, like rolling up a valley, an endless suspension bridge, rotating to form artificial gravity inside, some might be megacities others more park like but the end result is a people who live in space.

 

Once you already live in space taking slow orbits to resources that take many years is just a way of life and as you move out following those resources moving to the next star wouldn't be due to all the resources being used up any more than colonizing the new world was due to the Europeans using up all the resources of the Old World.

 

Oort clouds extend so far away from their stars that travel to the next star wouldn't be much further than travel to the last oort cloud object. Such a nomadic existence could spread far and wide but not leave a "scorched earth" behind it.

[Kinkajou]

My professor for a History of Life class (a paleontologist) this last semester is nigh-certain Mars once had life, and that starting life is simple, and maintaining it is the hard part.

 

His hypothesis:

Free oxygen predominantly comes from autotrophs. Other sources, like volcanic outgassing, are minimal, and would be soaked up by rocks straight away.

Mars is COVERED in red beds - red rocks full of iron oxides. We only see banded iron formations and red beds on earth deposited about the same time that autotrophs were oxygenating the atmosphere. And they are one of the most significant indicators of when exactly the Great Oxygenation Event happened.

Nothing short of a massive amount of autotrophs coming about could create the free oxygen levels that are required for red beds on Earth - as none are found beforehand.

 

The question is - if not life - what could have oxygenated Mars to the point where it is COVERED in red rocks? Obviously some sort of crisis happened after the fact to change the atmosphere radically, but before that?

 

I've just heard no other theories for an oxidized Mars that make nearly as much sense as this does. Life doesn't have to be complex to be there, after all. I'm talking something cyanobacteria-like. Something had to make Mars rusty - other theories about water vapor creating it don't make too much sense to me - Earth had oceans long before it had red beds. Plenty of water, yet no sizable amounts of iron oxide until the oxygenation event.

 

I'm not in the least bit saying that Mars had anything more intelligent than an autotrophic bacteria-like organism, but it's the theory that makes the most sense to me. Takes a lot of oxygen to make that much iron oxide.

[Moontanman]

My professor for a History of Life class (a paleontologist) this last semester is nigh-certain Mars once had life, and that starting life is simple, and maintaining it is the hard part.

 

His hypothesis:

Free oxygen predominantly comes from autotrophs. Other sources, like volcanic outgassing, are minimal, and would be soaked up by rocks straight away.

Mars is COVERED in red beds - red rocks full of iron oxides. We only see banded iron formations and red beds on earth deposited about the same time that autotrophs were oxygenating the atmosphere. And they are one of the most significant indicators of when exactly the Great Oxygenation Event happened.

Nothing short of a massive amount of autotrophs coming about could create the free oxygen levels that are required for red beds on Earth - as none are found beforehand.

 

The question is - if not life - what could have oxygenated Mars to the point where it is COVERED in red rocks? Obviously some sort of crisis happened after the fact to change the atmosphere radically, but before that?

 

I've just heard no other theories for an oxidized Mars that make nearly as much sense as this does. Life doesn't have to be complex to be there, after all. I'm talking something cyanobacteria-like. Something had to make Mars rusty - other theories about water vapor creating it don't make too much sense to me - Earth had oceans long before it had red beds. Plenty of water, yet no sizable amounts of iron oxide until the oxygenation event.

 

I'm not in the least bit saying that Mars had anything more intelligent than an autotrophic bacteria-like organism, but it's the theory that makes the most sense to me. Takes a lot of oxygen to make that much iron oxide.

 

Actually the action of hard UV light on ice producing H2O2 is thought to have been significant abiotic source of oxygen on the early earth...

[SamBridge]

Actually the action of hard UV light on ice producing H2O2 is thought to have been significant abiotic source of oxygen on the early earth...

But early Earth was quite hot, at least hotter than now by the time life came around and thus there was very little ice as most continents were also in the center near the equator as well, 2.7 billion years ago. The oceans were hot and highly corrosive to nascent continental rock and the high iron content combined with high ocean temperature sucked up most oxygen in the air naturally produced by Earth, which only left early life to create oxygen air.

Edited May 30, 2013 by SamBridge

[Moontanman]

But early Earth was quite hot, at least hotter than now by the time life came around and thus there was very little ice as most continents were also in the center near the equator as well, 2.7 billion years ago. The oceans were hot and highly corrosive to nascent continental rock and the high iron content combined with high ocean temperature sucked up most oxygen in the air naturally produced by Earth, which only left early life to create oxygen air.

 

 

Snowball Earth is theorized to have caused at least one oxygenation event.

[SamBridge]

Snowball Earth is theorized to have caused at least one oxygenation event.

Well, are we talking about a snowball Earth 2.7 billion years ago? There were some ice age events in the Phanerozoic eon within 543 million years ago as well as some snowballs 580-730 million years ago, but Earth's atmosphere started oxygenating heavily around 2.7 billion years ago, at which point there was not much ice.

Edited May 31, 2013 by SamBridge