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Plat
2005-Mar-26, 09:15 PM
Would it be just a terrestrial planet with a similar amount of water and oxygen as Earth? and of course similar distance from the sun or would it have to really resemble Earth?

The former one I dont think would be all that rare but the latter one would really really be rare, exceedingly rare.

Plat
2005-Mar-26, 09:28 PM
What is the current consensus on Earth-like planets now?

Abundant? common? alot? some? fraction? rare?

j0seph
2005-Mar-26, 11:28 PM
Originally posted by Plat@Mar 26 2005, 09:28 PM
What is the current consensus on Earth-like planets now?

Abundant? common? alot? some? fraction? rare?
We really do not have enough information about the rest of the universe.. or even the galaxy for that matter to determine just how many "earth-like" planets there actually are, but I would probly say they are fairly rare.


An earth like planet could share any number of similar characteristics as earth, but personally I think as long as it has an atmosphere that can support human life and a substantial amount of water, in my eyes that is earth like.

bossman20081
2005-Mar-27, 12:27 AM
Originally posted by Plat@Mar 26 2005, 05:45 PM
Would it be just a terrestrial planet with a similar amount of water and oxygen as Earth? and of course similar distance from the sun or would it have to really resemble Earth?

The former one I dont think would be all that rare but the latter one would really really be rare, exceedingly rare.
Similar atmosphere, a lot water (liquid), similar distance from the sun, similar gravity, similar star size, etc., but it all really relates to the first two, in my opinion.


What is the current consensus on Earth-like planets now?

It depends on if your opimistic or pessimistic, really. We only have one sample in the universe, and that's Earth, which is no where near enough to give an accurate estimate. I think that the universe is so large that the odds of Earth's conditions repeating are about, oh say, 1:trillion, which is my opinion. Even though its compared to a trillion, that's still great odds in the grand scheme of things.

Nereid
2005-Mar-27, 12:31 AM
What is the current consensus on Earth-like planets now?
As you pointed out in your first post in the first post in this thread, the definition of 'Earth-like planet' is quite important, in order to answer this question.

If we say 'condensed object, mass of ~0.5 to 2x that of the Earth, orbiting a star'; then the best way to answer would be to ask 'in what circumstances could we detect such a planet, using present techniques?'

Unfortunately, apart from planets around pulsars, we couldn't detect any Earth-like planets, period.

The next best way to answer might be to ask 'how frequently would Earth-like planets form around single stars, according to current theories of solar system formation?'

The answer here is that such theories do not constrain the formation of Earth-like planets with any significant degree of certainty.

Plat
2005-Mar-28, 01:16 AM
I would guess about 5 billion Earth-like planets existing at the same time.

Plat
2005-Mar-28, 02:29 AM
Also, evidence is mountaining up that Mars could have been an Earth-like planet and many scientists believe Venus had water. Plus as our technology gets better the exo-planet findings increase substantially, it seems like we find an exo-planet twice a week.

j0seph
2005-Mar-28, 02:40 AM
Originally posted by Plat@Mar 28 2005, 02:29 AM
it seems like we find an exo-planet twice a week.
Is it really that often?

Plat
2005-Mar-28, 04:03 AM
Naw, I was just exaggerating but my point is now that we know what to look for, how to look for them, with our technology that will improve in the future you can bet that we will find exo-planets at least once a week in the future, probably like 2010 and on.

astromark
2005-Mar-28, 07:18 AM
B) I know this has been done befor, but its worth a mention at this point. For life as we know it to evolve and thrive as it does here there are quiet a few things that need to be just right..., or so very near as to be the same as found here. The distance from its star. The energy output of that star. The nesassary shielding from radiation. The presance of water, (may not be vital )and the oxygen available. The size of the planet. ( so the gravity is about right )Stabilaty. it would be no good if you were constantly bombed by asteroids. And theres bound to be plenty I have missed, like a biosphear capable of suporting life, and so on. . . .


We as yet have not found one planet other than this one that fits this tall order.
Why is that?. . .Becouse we cant see all that well, yet.


Planets the size of Earth might be quiet comon. There might even be tens of thousands in this Galaxy alone. Its a probabilaty question. We are here, so there for they "are"there. It works for me. Time will answer this question sooner than you can shake a stick at,. . . . A very large telescope array in space. On the Moon.

bossman20081
2005-Mar-28, 03:57 PM
Originally posted by astromark@Mar 28 2005, 03:48 AM
B) I know this has been done befor, but its worth a mention at this point. For life as we know it to evolve and thrive as it does here there are quiet a few things that need to be just right..., or so very near as to be the same as found here. The distance from its star. The energy output of that star. The nesassary shielding from radiation. The presance of water, (may not be vital )and the oxygen available. The size of the planet. ( so the gravity is about right )Stabilaty. it would be no good if you were constantly bombed by asteroids. And theres bound to be plenty I have missed, like a biosphear capable of suporting life, and so on. . . .


We as yet have not found one planet other than this one that fits this tall order.
Why is that?. . .Becouse we cant see all that well, yet.


Planets the size of Earth might be quiet comon. There might even be tens of thousands in this Galaxy alone. Its a probabilaty question. We are here, so there for they "are"there. It works for me. Time will answer this question sooner than you can shake a stick at,. . . . A very large telescope array in space. On the Moon.
Im curious, life on earth is very adaptable, why couldn't life evolve to the conditions of no oxygen, water, ozone, etc.?

BTW There is life on earth that doesn't have to have oxygen, they are called anaerobes, and were probably one the the earliest life, as the primorial atmosphere of earth did not contain oxygen (well, minute amounts of it).

Ola D.
2005-Mar-28, 04:10 PM
Originally posted by bossman20081@Mar 28 2005, 03:57 PM
BTW There is life on earth that doesn't have to have oxygen, they are called anaerobes, and were probably one the the earliest life, as the primorial atmosphere of earth did not contain oxygen.
True, which is common among bacteria and yeast.

GOURDHEAD
2005-Mar-28, 04:18 PM
My guess is that stellar systems in the MW of 0.1 to 2 times the age of the solar system will have one or more rocky planets within 0.9 to 3 earth masses orbiting within the goldilocks zone [commensurate with the stellar type] with large amounts of water and oxygen capable of being released into their atmospheres as O2 by any anerobes that happen to have evolved there. There is strong observational evidence of the existence of the required chemical elements being afloat in the interstellar medium and the universality of the laws of physics for these conditions to exist. Donning my big bang hat (rare for me), I'm not sure how soon after the big bang that enough rocky planet elements accumulated in the ISM to form rocky planets, but recent detection of considerable percentage of metallicities more than ten billions of years ago causes me to feel safe in making the above guess.

John L
2005-Mar-28, 05:41 PM
An Earth-like planet would have between .5 and 1.3 G gravity. It would be in the habitably zone where sufficient solar radiation is recieved to support liquid water. It would have an atmosphere with no highly toxic gases and an air pressure between .5 and 2 times Earths. Its atmosphere would not have to contain oxygen, but oxygen must be present in some form on the planet so that it could be released by life. The planet must have water in some form that could be reached and utilized. It would not be overly radioactive or constantly bombarded by meteorites. It could be either in its own orbit, or it could be the moon of a much larger world (my personal preference as it would be darn romantic to site in a car and watch a ringed gas giant crest the horizon :D ).

j0seph
2005-Mar-28, 06:21 PM
Originally posted by John L@Mar 28 2005, 05:41 PM
It would have an atmosphere with no highly toxic gases and an air pressure between .5 and 2 times Earths.
I think thats a bit too restricting, because who knows... that toxic gas to us could be the water to another lifeform, heavy air pressure wouldnt matter, because if a life form is going to evolve in an atmosphere its going to adapt to the high pressure and depend on it.

I think that we need to use symbolism in defining an earth like planet...

for example, as long as it is has an atmosphere, similar geological makup, and has water (because thats what makes up 75% of the earth's suface), the pressure factors wouldnt matter, the makup of the atmosphere wouldnt matter, just as long as it is capable of supporting a "known" form of life


perhaps we need to devise a scale for earth-likeness to compare planets to... because I doubt having one standard would fit all "earth-similar" planets.

astromark
2005-Mar-28, 08:39 PM
:rolleyes: I will not quote myself. . .but we are saying the same thing.
If its a Earth like planet or just a planet that could saport life that has the opertunity to evolve into some thing of interest to us. I havent seen yet the disenting voice that proclams we are alone. We may be useing slightly difering rules, but we do all seem to agree, thats amazing. Congratulations,

John L
2005-Mar-28, 09:31 PM
I look at an Earth-like planet as being one that can eventually be terraformed and colonized by humans. No offense to the other life forms in the universe, but I'm a predatory mammal and fully intend my species to settle every habitable inch of real estate in the universe. Luckily we have a few hundred million years more on Earth to figure out the whole interstellar and intergalactic travel thing before the Sun cahnges enough to make life here a bit difficult, but even if we don't figure out FTL travel we can still colonize this entire galaxy. Even sublight we could have people throughout the galaxy in one million years. There is nothing in physics that can stop us. Therefore, my definition of an Earth-like planet is skewed toward human habitability, either immediate or through moderate terraforming.

j0seph
2005-Mar-28, 11:30 PM
Very interesting point of view, although true :)


That raises another question... If we were to find an earth-like planet would we be in our rights to inhabit it? we could introduce any number of biological hazards for the native life which could be fatal (if live is present)... though I do not believe that we would pass up the oppertunity to colonize such a planet....

Plat
2005-Mar-29, 03:25 AM
Didnt some ancient plants also create much of the Earth's oxygen?

Spacemad
2005-Mar-29, 07:09 AM
Originally posted by j0seph@Mar 28 2005, 11:30 PM

That raises another question... If we were to find an earth-like planet would we be in our rights to inhabit it? we could introduce any number of biological hazards for the native life which could be fatal (if live is present)... though I do not believe that we would pass up the oppertunity to colonize such a planet....

That's certainly a very interesting question, Joseph!!! What right have we to go & destroy another life form's world to make it inhabitable for us?

Perhaps if our world were in extreme danger of being destroyed by some "natural" form, (an asteroid on collision course that our technology at the time might not be able to destroy or "push" out of the way, some instability in the Sun that would cause it to flare up & cause excessive heating/radiation damage & make the Earth uninhabitable for life "as we know it"), then I would be in favour of settling an "Earth-like" planet that had its own indigenous lifeforms.

Might a world with Earth-like conditions not already support life - at the very least vegetable & bacterial - I know of no other way a planet could otherwise have free oxygen?

GOURDHEAD
2005-Mar-29, 02:05 PM
perhaps we need to devise a scale for earth-likeness to compare planets to... because I doubt having one standard would fit all "earth-similar" planets. Perhaps our focus should be on "life initiating" and "life supporting" rather than Earthlike. For example, even if Europa, Ganymede, or Callisto have not initiated life on their own, they could support Earthlike organisms provided we supply enough energy assuming gravitational flexing has not done so already.

Planets or moons that have initiated life on their own but have not developed a "sentient species", are fair game for us to develop provided we can survive their microbes. Perhaps we can negotiate for space on the surface of those with homegrown sentients. The "Venuses" and "Marses" of the MW may be our best bet for colonization since their microbes should be fewer with which to contend.

John L
2005-Mar-29, 05:57 PM
Originally posted by Spacemad@Mar 29 2005, 01:09 AM
What right have we to go & destroy another life form's world to make it inhabitable for us?
First of all, the worlds we would focus on first are those that are closest to our needs. That means we probably won't be destroy the environment on worlds in favor of one suitable to us. That will eventually happen though, and for the Darwinians in the crowd that is all the right we need. Survival of the fitest. If we can take the worlds we will.

imported_Ziggy
2005-Mar-29, 08:19 PM
My defination of an Earth-like planet is probably a type of planet that's VERY rare. To me, an Earth-like planet is one that has a breathable atmosphere to humans, large amounts of liquid water on the surface, substantial complex life living on it, and a tolerable gravity well (i.e., you don't get squashed or float up, up, and away). Yup, mine's a real pearl :rolleyes: .

Ola D.
2005-Mar-29, 08:39 PM
Originally posted by John L@Mar 29 2005, 05:57 PM
for the Darwinians in the crowd that is all the right we need. Survival of the fitest. If we can take the worlds we will.
If I'm a Darwinian, I would actually save the Earth-like planet as a proof for evolution. Possibly its species will develop just as the Earth ones did, or more specifically were predicted that they did.

John L
2005-Mar-29, 10:59 PM
Ola, There are hundreds of billions of stars in this galaxy alone that could possibly play host to good Earth-like candidates. I see no problem saving several good Earth-like worlds for the purely scientific purpose of watching them develop their own life and seeing it evolve over the millenia - as long is it can never compete with us, of course. You'd want to automate that as much as possible as no scientist would be alive at the end of the project who was around a few billion years before when it started, but it would be a nice experiment. As for the rest of the worlds I say put them to our use.

Plat
2005-Mar-30, 01:54 AM
If we dont need them then why take them? the only way we would have to do that in my opinion is if this Earth is going to get hammered with an asteroid or something, completely destroyed.

j0seph
2005-Mar-30, 08:17 AM
A new place to live and the pride that we have claimed another world - Thats why.

If we found a habitable world not too far away, there is absolutly NO way we can resist colonizing it, it is our nature as humans... and like John L, I'm all for it!, Although I just hope we dont trash it... ;)

I think that before we even touch the surface of the new-found planet, that we better have a plan for building self sufficient, low impact structures... this means no sky scapers or victorian style architecture... because the least enviromental impact we have, the better.

eburacum45
2005-Mar-30, 03:29 PM
There will be many types of terrestrial planets out there, I am certain;

but the fraction of those worlds which would be shirtsleeve environments for humans would probably be very small, and the number of those worlds which would have edible food plants or animals would probably be much smaller.

Terrestrial worlds could include hot greenhouse worlds like Venus;
wet greenhouse worlds;
dry Mars-like worlds;
wet lifeless worlds like Mars was before it lost its atmosphere;
lifeless worlds with nitrogen/CO2 atmospheres like the early Earth;
planets like the Earth three billion years ago with anaerobic life in the seas only;
Banded iron regime planets like the Earth one billion years ago, with photosynthetic organisms which produce oxygen (but are not tolerant of O2, so periodically poison themselves and die back- forming discrete bands in the stratigraphic record);
Earth-like worlds with extensive deserts above the boiling point of water by day, freezing by night;
planets entirely covered in shallow oceans;
planets locked in permanent or persistent ice ages;
salt covered worlds which are losing their hydrosphere;
waterworlds with oceans hundreds of kilometers deep. with high pressure ice mantles and abiotic oxygen/nitrous oxide atmospheres;
large dry high gravity Venus-like planets up to ten times the mass of Earth with very thick hot atmospheres;
cooler massive terrestrials further from the central star with oceans beneath a thick, hydrogen and water vapour atmosphere;
carbon planets with carbonic acid seas;
dry carbon planets with oily hydrocarbon lakes;
Chlorine rich worlds, fluorine rich worlds, worlds poisoned by chromium, arsenic, lead...
planets covered in radioactive dust or its decay products from nearby supernovae...

any more?

John L
2005-Mar-30, 04:48 PM
Originally posted by eburacum45@Mar 30 2005, 09:29 AM
There will be many types of terrestrial planets out there, I am certain;

but the fraction of those worlds which would be shirtsleeve environments for humans would probably be very small, and the number of those worlds which would have edible food plants or animals would probably be much smaller.
You left out an important category that could drastically increase the odds of finding a suitable habitable world - the large moons of gas giants. We've found through our current planet hunts that gas giants nearer to the star than Jupiter are not uncommon. Of course, the Hot Jupiters right up at the star would be untenable, but a gas giant in a habitable zone orbit may host two or more large moons that each could be habitable. Some may even be the size of Earth or larger. It think moons like these will be the first outposts of humanity outside the solar system.

bossman20081
2005-Mar-30, 05:17 PM
Originally posted by j0seph@Mar 30 2005, 04:47 AM
A new place to live and the pride that we have claimed another world - Thats why.

If we found a habitable world not too far away, there is absolutly NO way we can resist colonizing it, it is our nature as humans... and like John L, I'm all for it!, Although I just hope we dont trash it... ;)

I think that before we even touch the surface of the new-found planet, that we better have a plan for building self sufficient, low impact structures... this means no sky scapers or victorian style architecture... because the least enviromental impact we have, the better.
I don't know about that, I'm all for advancement of our own species, but if it involves destroying any species, I must decline. You see, what if an alien species destroyed the early life of earth just for them to settle here? It's like when Europe settled North America, they thought that the Native Americans were primitives, therefore it doesn't matter if they live or die. Or how about the Holocaust?

Then, what if we settle on a planet claimed by an alien species? It's always a possibility, and I sure wouldn't go through an intergalactic war for a planet. (though, we have fought for much less)

Just a couple things to think about before just thinking we have the right to settle any planet we want.

Spacemad
2005-Mar-30, 07:59 PM
I think that before we even touch the surface of the new-found planet, that we better have a plan for building self sufficient, low impact structures... this means no sky scapers or victorian style architecture... because the least enviromental impact we have, the better.

I don't know about that, I'm all for advancement of our own species, but if it involves destroying any species, I must decline. You see, what if an alien species destroyed the early life of earth just for them to settle here? It's like when Europe settled North America, they thought that the Native Americans were primitives, therefore it doesn't matter if they live or die. Or how about the Holocaust?

Then, what if we settle on a planet claimed by an alien species? It's always a possibility, and I sure wouldn't go through an intergalactic war for a planet. (though, we have fought for much less)

Just a couple things to think about before just thinking we have the right to settle any planet we want.[/QUOTE]


I don't know about that, I'm all for advancement of our own species, but if it involves destroying any species, I must decline.

I'm in complete agreement with you there, Bossman, we should do our utmost to avoid destroying other species of life on other worlds, if it already exists.

If some alien specie had colonised our world many millions of years ago, where would we be today???? If they had modified the world for their own comfort, as many propose here, might our species never come about??? Who knows? :unsure:

Before we go gallivanting around the universe terraforming planets lets take a l-o-n-g hard look at what might be the possible repercussions!!! (then act accordingly!)

John L
2005-Mar-30, 08:00 PM
The human species will go extinct if we don't move out of this solar system. When our Sun blows in a few billion years all life in this solar system goes with it. If this is the only location with humans then that's it. The same goes if we only move to a few other solar systems. Our entire history has been the expansion of our species at the cost of the other dominant predators. Remember that you and I are predators. The big cats, wolves, bears, and their like have all dwindled because we became the dominant predator. The same is true in the galaxy as a whole. If we are the dominant predator then we will displace other species. If we are not the domonant predator then we are destined to be displaced. That's nature.

And furthermore, the non-predatory species we have chosen to consume have been nurtured and are successful through that relationship. All other animals, those deemed unimportant as a source of food, work, or companionship have dwindled. The same will occur on every world we move to. But don't worry. Unless something really major is discovered soon that can get us moving out into the galaxy then none of us will have to make the decisions about which world to colonize, which species to domesticate, and which to erradicate.

antoniseb
2005-Mar-30, 09:11 PM
Originally posted by John L@Mar 30 2005, 08:00 PM
The human species will go extinct if we don't move out of this solar system.
I think that when we start spreading out, we will mostly be moving to K & M dwarf stars, as that is what is mostly available, and also those stars are will stay in the main sequence much longer than the sun. I suspect that we will rarely find ourselves on habitable planets in such places without a lot of terraforming. The need to kill off or subjugate other species won't be there.

Spacemad
2005-Mar-30, 09:22 PM
Originally posted by antoniseb+Mar 30 2005, 09:11 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (antoniseb &#064; Mar 30 2005, 09:11 PM)</td></tr><tr><td id='QUOTE'><!--QuoteBegin-John L@Mar 30 2005, 08:00 PM
The human species will go extinct if we don&#39;t move out of this solar system.
I think that when we start spreading out, we will mostly be moving to K & M dwarf stars, as that is what is mostly available, and also those stars are will stay in the main sequence much longer than the sun. I suspect that we will rarely find ourselves on habitable planets in such places without a lot of terraforming. The need to kill off or subjugate other species won&#39;t be there.[/b][/quote]


I suspect that we will rarely find ourselves on habitable planets in such places without a lot of terraforming. The need to kill off or subjugate other species won&#39;t be there.

I hope you are right, Anton&#33;

Plat
2005-Mar-31, 02:01 AM
Originally posted by eburacum45@Mar 30 2005, 10:29 AM
There will be many types of terrestrial planets out there, I am certain;

but the fraction of those worlds which would be shirtsleeve environments for humans would probably be very small, and the number of those worlds which would have edible food plants or animals would probably be much smaller.

Terrestrial worlds could include hot greenhouse worlds like Venus;
wet greenhouse worlds;
dry Mars-like worlds;
wet lifeless worlds like Mars was before it lost its atmosphere;
lifeless worlds with nitrogen/CO2 atmospheres like the early Earth;
planets like the Earth three billion years ago with anaerobic life in the seas only;
Banded iron regime planets like the Earth one billion years ago, with photosynthetic organisms which produce oxygen (but are not tolerant of O2, so periodically poison themselves and die back- forming discrete bands in the stratigraphic record);
Earth-like worlds with extensive deserts above the boiling point of water by day, freezing by night;
planets entirely covered in shallow oceans;
planets locked in permanent or persistent ice ages;
salt covered worlds which are losing their hydrosphere;
waterworlds with oceans hundreds of kilometers deep. with high pressure ice mantles and abiotic oxygen/nitrous oxide atmospheres;
large dry high gravity Venus-like planets up to ten times the mass of Earth with very thick hot atmospheres;
cooler massive terrestrials further from the central star with oceans beneath a thick, hydrogen and water vapour atmosphere;
carbon planets with carbonic acid seas;
dry carbon planets with oily hydrocarbon lakes;
Chlorine rich worlds, fluorine rich worlds, worlds poisoned by chromium, arsenic, lead...
planets covered in radioactive dust or its decay products from nearby supernovae...

any more?
Of course "we" wont be able to survive a second on those planets but thats because we are suited for just this planet (because we evolved under the conditions of this planet) but life might evolve on those other planets...

Nereid
2005-Mar-31, 07:46 AM
The human species will go extinct if we don&#39;t move out of this solar system. When our Sun blows in a few billion years all life in this solar system goes with it. If this is the only location with humans then that&#39;s it. The same goes if we only move to a few other solar systems. Our entire history has been the expansion of our species at the cost of the other dominant predators.
I&#39;m getting giddy&#33; The Sun won&#39;t go red giant for another ~4 billion years; that&#39;s longer - by far - than the time all the &#39;dominant predators&#39; have been around. About the only thing you can say for sure is that no &#39;predator species&#39; on Earth today will be around in 400 million years, let alone 4 billion.

In any case, if you have some concern over robustness, then why not &#39;download&#39;? Homo sap.&#39;s ability to recreate personalities &#39;in silicon&#39; (or, more accurately, &#39;in software&#39;) is likely only a century away, a millenium at most. By around the same time, we will have found ways to make &#39;environmentally friendly&#39; von Neumann factories, and we can all board - in software - some dozen (thousand?) boulders on their leisurely way out into the Milky Way. B)

wstevenbrown
2005-Mar-31, 02:59 PM
Yup.

Silicon avatars make
The non-relativistic trip
With their frozen descendants
In a generation ship

How do they know their parents?
How will they know their past
When they find themselves decanted
In a garden, ripe at last?

When we become the mentors,
Unfolding all of mystery
Will our children understand
They&#39;re recreating history?


Sorry, All. I occasionally forget this is a private vice&#33; :D Steve

j0seph
2005-Mar-31, 06:40 PM
Originally posted by bossman20081+Mar 30 2005, 05:17 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (bossman20081 &#064; Mar 30 2005, 05:17 PM)</td></tr><tr><td id='QUOTE'><!--QuoteBegin-j0seph@Mar 30 2005, 04:47 AM
A new place to live and* the pride that we have claimed another world - Thats why.

If we found a habitable world not too far away, there is absolutly NO way we can resist colonizing it, it is our nature as humans... and like John L, I&#39;m all for it&#33;, Although I just hope we dont trash it...* ;)

I think that before we even touch the surface of the new-found planet, that we better have a plan for building self sufficient, low impact structures... this means no sky scapers or victorian style architecture... because the least enviromental impact we have, the better.
I don&#39;t know about that, I&#39;m all for advancement of our own species, but if it involves destroying any species, I must decline. You see, what if an alien species destroyed the early life of earth just for them to settle here? It&#39;s like when Europe settled North America, they thought that the Native Americans were primitives, therefore it doesn&#39;t matter if they live or die. Or how about the Holocaust?

Then, what if we settle on a planet claimed by an alien species? It&#39;s always a possibility, and I sure wouldn&#39;t go through an intergalactic war for a planet. (though, we have fought for much less)

Just a couple things to think about before just thinking we have the right to settle any planet we want.[/b][/quote]
What I was trying to say was... if we were to find a planet suitable for our needs, we should try to make the smallest enviromental impact as possible.

"but if it involves destroying any species, I must decline." - absolutly not. That would be the worst thing we could ever do in my eyes.... Killing off an entire species.... no.....thats why I was offering the idea of low-impact, self-sufficient structures.... maybe a bubble-like structure that would stand several meters off the ground, allow no gases to escape into the atmosphere... possibly even solar powered. This way the Native life-form woud not care.. unless of course they were intelligent enough to tell us no, in that case it is obviously their planet and we have no right to take it in the first place

John L
2005-Mar-31, 08:43 PM
99.9% of all the species that have existed in the history of the Earth are extinct. It&#39;s part of the natural order that habits change, new competitors for resources emerge, and species go extinct. Don&#39;t feel bad if you are the engine of that extinct because you are part of nature, too. To feel that we are somehow above nature is pure arrogance.

astromark
2005-Mar-31, 08:54 PM
Noble thoughts, I comend your logic, but we all know this wont be what actually happens. Out track record is discrasefull. "When morality and money cross swords, its the money that wins". Untill we address this issue we are doomed to go down the same road as before. As a spiecies we have learnt very little from history. I see a recant news item regarding Carbon Dioxide, Up 20% since 1985.,and what are we doing... Opec is increasing the patrolium output, thats going to help, Not.
China and India are just becomming gaints of consuption. I can see tension, these are going to be interesting times. Lets go to Titan. Build that Super Dome, and move in.

John L
2005-Mar-31, 09:27 PM
Since the realization that the increase in CO2 could mean problems with the climate we&#39;ve been working on alternative sources of fuel. It&#39;s the US that&#39;s spending BILLIONS on things like hydrogen fuels cells, cleaner fission, fusion, advanced solar, wind, etc, that will finally end our dependence on oil. The technology that make cars like the Toyota Prius Hybrid possible was first researched by scientists and universities in the US, and its our partnerships with universities and research teams around the globe that will finally wean us from oil. The next big problem will be how to produce all of that hydrogen without burning coal and oil. Maybe fusion will be the final answer, and that&#39;s finally actually close.

antoniseb
2005-Mar-31, 10:48 PM
Originally posted by John L@Mar 31 2005, 09:27 PM
Maybe fusion will be the final answer, and that&#39;s finally actually close.
Maybe it will. I was guessing that the large solar plants in the deserts cracking water and piping Hydrogen to the rest of the world made sense. To me it sounds easier to build and maintain than fusion, but once we have the technology for fusion down, maybe it&#39;ll be better.

bossman20081
2005-Mar-31, 11:05 PM
Originally posted by j0seph+Mar 31 2005, 03:10 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (j0seph @ Mar 31 2005, 03:10 PM)</td></tr><tr><td id='QUOTE'>
Originally posted by bossman20081@Mar 30 2005, 05:17 PM
<!--QuoteBegin-j0seph@Mar 30 2005, 04:47 AM
A new place to live and* the pride that we have claimed another world - Thats why.

If we found a habitable world not too far away, there is absolutly NO way we can resist colonizing it, it is our nature as humans... and like John L, I&#39;m all for it&#33;, Although I just hope we dont trash it...* ;)

I think that before we even touch the surface of the new-found planet, that we better have a plan for building self sufficient, low impact structures... this means no sky scapers or victorian style architecture... because the least enviromental impact we have, the better.
I don&#39;t know about that, I&#39;m all for advancement of our own species, but if it involves destroying any species, I must decline. You see, what if an alien species destroyed the early life of earth just for them to settle here? It&#39;s like when Europe settled North America, they thought that the Native Americans were primitives, therefore it doesn&#39;t matter if they live or die. Or how about the Holocaust?

Then, what if we settle on a planet claimed by an alien species? It&#39;s always a possibility, and I sure wouldn&#39;t go through an intergalactic war for a planet. (though, we have fought for much less)

Just a couple things to think about before just thinking we have the right to settle any planet we want.
What I was trying to say was... if we were to find a planet suitable for our needs, we should try to make the smallest enviromental impact as possible.

"but if it involves destroying any species, I must decline." - absolutly not. That would be the worst thing we could ever do in my eyes.... Killing off an entire species.... no.....thats why I was offering the idea of low-impact, self-sufficient structures.... maybe a bubble-like structure that would stand several meters off the ground, allow no gases to escape into the atmosphere... possibly even solar powered. This way the Native life-form woud not care.. unless of course they were intelligent enough to tell us no, in that case it is obviously their planet and we have no right to take it in the first place [/b][/quote]
Whoah, how did that happen? Sorry, somehow I skipped you last paragraph. Anyway, I was going to put those points across anyway.


The human species will go extinct if we don&#39;t move out of this solar system. When our Sun blows in a few billion years all life in this solar system goes with it. If this is the only location with humans then that&#39;s it. The same goes if we only move to a few other solar systems. Our entire history has been the expansion of our species at the cost of the other dominant predators. Remember that you and I are predators. The big cats, wolves, bears, and their like have all dwindled because we became the dominant predator. The same is true in the galaxy as a whole. If we are the dominant predator then we will displace other species. If we are not the domonant predator then we are destined to be displaced. That&#39;s nature.

And furthermore, the non-predatory species we have chosen to consume have been nurtured and are successful through that relationship. All other animals, those deemed unimportant as a source of food, work, or companionship have dwindled. The same will occur on every world we move to. But don&#39;t worry. Unless something really major is discovered soon that can get us moving out into the galaxy then none of us will have to make the decisions about which world to colonize, which species to domesticate, and which to erradicate.

I didn&#39;t know we were going to be talking that for in advance. Granted, we would have to move, but if we could make migrations on the planetary scale, then I would imagine that engineering skills would have to be very impressive, so impressive that at least 6 billion people could survive several decades in space. So, instead of migrating, why couldn&#39;t we just make the change permanent? We wouldn&#39;t have to really depend on any planet (we&#39;d perhaps mine asteroids as they would be easier). If we are talking this far in advance, we wouldn&#39;t need a planet.

Nereid
2005-Mar-31, 11:16 PM
If we are talking this far in advance, we wouldn&#39;t need a planet.
Download your personality + experiences into software; encode that into relict neutrino oscillations*, and you&#39;ll be immortal&#33;

*OK, we can&#39;t even detect these yet, let alone know how to encode info onto them - whether through oscillations or anyhow else - but then 100 years ago we didn&#39;t even know about neutrinos&#33; and 1,000 years ago, we didn&#39;t know what powered the Sun&#33;&#33; and 10,000 years ago, we didn&#39;t know that the Earth was round, the Sun &#39;just&#39; a star&#33;&#33;&#33; and 100,000 years ago, we ... [you get the picture]

Darrrius
2005-Apr-01, 08:24 AM
I dont think anyone has mentioned plate tectonics, something that would be 1st on my list if you&#39;re talking about Earthlike planets. That and of course loads and loads of water&#33;

j0seph
2005-Apr-02, 05:06 AM
Waht exactly do you mean by plate tectonics?... as in similar activity and size?

astromark
2005-Apr-02, 10:11 AM
I might have missed some thing here?. . It would not be the first time. :unsure:
Why do you think contanental plate techtonics have played such a pivatal role in the evolutionary path of man?
I dont see how exposure to poisonouse gasses ozing from volcanic vents has made this a better place. Exposure to massive sysmic upheaval is not good for our land based dwellings, or us.
Stabilaty, moderate climate, abundance of H2O, I understand. Please explain?

GOURDHEAD
2005-Apr-02, 11:57 AM
Why do you think contanental plate techtonics have played such a pivatal role in the evolutionary path of man? It&#39;s the great recycler. When it stops, erosion of the high places will make this a water world starved of essential life supporting minerals.

eburacum45
2005-Apr-02, 12:40 PM
Circulation of carbon in plate tectonics is a major factor in the dynamic equilibrium that maintains our atmosphere; otherwise carbon could become locked up in rocks, and our biosphere would not have a constant throughput of carbon dioxide to produce biomass and maintain the oxygen in the atmosphere.

Despite the current panic over carbon dioxide, it is essential for photosynthesis and the production of oxygen; without a supply of CO2, our oxygen atmosphere would disappear in a few million years.
Now it may be that carbon circulation and oxygen production could occur on a planet without tectonics, but the environmental conditions would be very different to Earth&#39;s.

This worldbuilder&#39;s guide gives some idea of problems a world without tectonics might face;
http://www.trisen.com/sol/static/wg/i-three2.html

note- much of this guide is speculative and some of it may be dated, but it is certainly thought provoking.

Darrrius
2005-Apr-02, 02:19 PM
Originally posted by eburacum45@Apr 2 2005, 12:40 PM
Circulation of carbon in plate tectonics is a major factor in the dynamic equilibrium that maintains our atmosphere; otherwise carbon could become locked up in rocks, and our biosphere would not have a constant throughput of carbon dioxide to produce biomass and maintain the oxygen in the atmosphere.

Despite the current panic over carbon dioxide, it is essential for photosynthesis and the production of oxygen; without a supply of CO2, our oxygen atmosphere would disappear in a few million years.
Now it may be that carbon circulation and oxygen production could occur on a planet without tectonics, but the environmental conditions would be very different to Earth&#39;s.

This worldbuilder&#39;s guide gives some idea of problems a world without tectonics might face;
http://www.trisen.com/sol/static/wg/i-three2.html

note- much of this guide is speculative and some of it may be dated, but it is certainly thought provoking.
Thanks... sorry I should have elaborated...

Darrrius
2005-Apr-03, 09:41 PM
heres another good link as to the important role plate tectonics have played in Earths history.

http://www.eas.slu.edu/People/DJCrossley/u...th/chapter9.htm (http://www.eas.slu.edu/People/DJCrossley/uniquearth/chapter9.htm)

Yisrael Asper
2005-Apr-14, 03:05 PM
Before we can declare a Planet Earth-like we have to decide on what a planet is. Below is my Petition I have posted on this site elsewhere. I will in exchange try to come up with one for an Earth-like Planet.

My Definition of a Planet and a Moon of an object
Petition to astro2006@cbttravel.cz
Sign on to the below Petition to the IAU, the International Astronomical Union or help make a consensus to modify this one. There will be a conference in Prague by the IAU in 2006. Email me at yisraelasper@hotmail.com to find yourself included or removed below through my editing this message.

To whom this may concern
Below are the proposed definitions of a planet and a moon of an object based
both on what the IAU has been saying in addition to the public&#39;s usage. Pluto would still be counted as a planet for historical reasons and the public would still feel that it is not completely arbitrary in still having Pluto recognized as a planet since it was considered so under the assumption that it was the Planet X which was good scientific theory for it&#39;s day.

The definition of a moon below at present is not accepted as any, even strangely shaped world is considered a moon as long as it orbits a planet but it has led to too much of a discrepancy between what people think of as a moon and what is scientifically at present defined as a moon. Over time definitions for astronomical objects have changed and it is really a matter of language with people also being used to surprising scientific differences from what they would call the definition otherwise but it is time to try to make the definition of a moon of an object to be more in accordance with what people picture at this time.

Thank you
Yisrael Asper
yisraelasper@comcast.net
yisraelasper@hotmail.com
yisraelasper@yahoo.com
yisraelasper@msn.com

Definition for a planet and a moon
__________________________________________________ _____________
Definition of a Planet
Pluto and objects with true masses below the limiting mass for
thermonuclear fusion of deuterium that orbit stars or stellar remnants are
"planets" provided they have orbital inclinations at least roughly enough on
their planetary planes so that they do not have orbits that cross the orbits of other planets or belts of material with orbital inclinations that follow the same standard as planets. The minimum mass/size required for an object to be considered a planet should be the amount needed to have gravity round the object towards its common center.

Definition of a moon of an object
Any object orbiting planets bordering the Asteroid Belt of our Solar System
and outward until the border of the outer Solar System of ours&#39; belt and any
object that would be considered a planet if what it orbits is treated as a
star or stellar remnant is a moon of an object with the exception that
whatever characteristic of a planet is lacking in the object treated as a
star or stellar remnant can lack in the moon.

John L
2005-Apr-14, 07:54 PM
Yisraelasper,

I agree that we do need a good definition of a planet, but I don&#39;t think it matters for this discussion. I think the arguement is what are the criteria specifically of an Earth-like world. In my opinion that relates to the ability of the world to support Earth organisms.

Yisrael Asper
2005-Apr-14, 08:12 PM
You would be right but the problem is that the International Astronomical Union determines what is a planet or a moon of an object. We need to put our input.

j0seph
2005-Apr-16, 05:13 PM
Lets work out a scale of Earth-likeness... shall we?

EL = Earth-like

EL1: Must at least have a comparible size to *our* earth.
EL2: Must have both Comparable size and similar mass.
EL3: Must have either comparable size or mass, as well as atleast a 25% similar core material makup.
EL4: Come on, I need some help :)


We can keep debating what our opinions are or we can do something about it and make a fairly uniform scale, there are plenty of inteligent and capable people here, we can do it.

jhwegener
2005-Apr-16, 08:54 PM
Here some ideas of what perhaps is important for an earth like planet to support not only primitive organisms, but someone like us and related.
Water in some quantity on the surface. Variable landscapes and altitudes vertically.
Tilt of axis(whitout that no seasons as we know it. But distribution and even location of continents, relative to each other and to poles may have been important for the way organisms evolved here, and will or will not evolve elsewhere. And I do not see that the list have to stop there. There is a lot of factors which may have been important or even necessary for developing the diverse life on earth. Perhaps some of the factors we now regards very important is not, perhaps something we look upon as "details" are crucial. I could give some arguments for both, and especially the later. But of course I do not know. I guess no human being really does.
A "scale of earth likeness" do not necessarily give any clues to probability of "intelligent" or "complex" life.

j0seph
2005-Apr-16, 09:40 PM
Originally posted by jhwegener@Apr 16 2005, 08:54 PM
A "scale of earth likeness" do not necessarily give any clues to probability of "intelligent" or "complex" life.
Correct, but it would answer a lot of questions and fits the topic title of the Thread, and it&#39;s just a suggestion ;)

eburacum45
2005-Apr-17, 06:40 PM
A planet might have exactly the same composition as the Earth but have no life whatsoever; such a planet would have a nitrogen /watervapour/CO2 atmosphere and be entirely inhospitable to life.
Four considerations occur to me;

the mass and composition of the planet, thickness of crust, ratio of land to water, depth and composition of atmosphere;
the distance from the star and luminosity of that star;
the age of the planet (over time the planet will lose volatile elements- rapidly in the case of hydrogen, less rapidly in the case of oxygen and nitrogen- tectonics and magnetic field will also disappear after a few billion years depending on the mass and composition);
the presence or absence of a biosphere, and the precise details of that biosphere.

so terrestrial planets will be very variable, n my opinion; we have three classes now- (Earth, Martian, Venus-like) I expect that we will discover many, many more.

jhwegener
2005-Apr-17, 10:41 PM
Perhaps some of the earth like bodies do not have any "mother star" (sun), but will be very like ours in other respects. (by one definition such a body will not be a "planet", but I think it should be included. Who says cirkling around a star is the only, or common way?)
Earths "tilt" of axis, and its moon may also matter. One may suspect that some factors for life may still be unknown to us. And one may think life on earth and eventually other "living planets" could disappear for reasons we still regard as relatively unimportant. How much do we really know about this planet and its life?

Spacemad
2005-Apr-18, 08:04 AM
jhwegener:.


Perhaps some of the earth like bodies do not have any "mother star" (sun), but will be very like ours in other respects.

Unless a planet has a star which it orbits it would be of no use to us. We depend on the star&#39;s heat to make the planet inhabitable. It may have a mass & gravity similar to that of Earth&#39;s but it would not have an atmosphere, at least not in a gaseous state.

Nyrath
2005-Apr-18, 05:48 PM
http://www.astrobio.net/news/modules.php?o...rticle&sid=1519 (http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1519)
http://www.astrobio.net/news/modules.php?o...rticle&sid=1526 (http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1526)

Her HabCat database is available on my website here:
http://www.projectrho.com/smap06.html

Yisrael Asper
2005-Apr-18, 09:55 PM
Originally posted by jhwegener@Apr 17 2005, 10:41 PM
Perhaps some of the earth like bodies do not have any "mother star" (sun), but will be very like ours in other respects. (by one definition such a body will not be a "planet", but I think it should be included. Who says cirkling around a star is the only, or common way?)
Earths "tilt" of axis, and its moon may also matter. One may suspect that some factors for life may still be unknown to us. And one may think life on earth and eventually other "living planets" could disappear for reasons we still regard as relatively unimportant. How much do we really know about this planet and its life?
It seems too late to have it included as the IAU has already declared in its working definition of a planet which it pledges to uphold as long as it can that a planet not revolving about the sun is not a planet or is it too late? If you want to get it changed then you have to let your voice be heard. I have modified my petition&#39;s words to make it more clear. We can make a Universe Today Forum Consensus Petition if we wish.


Here is the Petition:

Definition of a Planet and a Moon of an object
Petition to astro2006@cbttravel.cz

To whom this may concern
Below is a proposed definition of a planet and also a proposed definition of
a moon of an object based both on what the IAU has been saying in addition
to the public&#39;s usage. Pluto would still be counted as a planet for
historical reasons and the public would still feel that it is not completely
arbitrary in still having Pluto recognized as a planet since it was
considered so under the assumption that it was the Planet X which was good
scientific theory for it&#39;s day.

The definition of a moon below at present is not accepted as any, even
strangely shaped world is considered a moon as long as it orbits a planet
but it has led to too much of a discrepancy between what people think of as
a moon and what is scientifically at present defined as a moon. Over time
definitions for astronomical objects have changed and it is really a matter
of language with people also being used to surprising scientific differences
from what they would call definitions for words otherwise but it is time to
try to make the definition of a moon of an object to be more in accordance
with what people picture.

Thank you
Yisrael Asper
yisraelasper@comcast.net
yisraelasper@hotmail.com
yisraelasper@yahoo.com
yisraelasper@msn.com

Definition for a planet and a moon
__________________________________________________ _____________
Definition of a Planet
Pluto and objects with true masses below the limiting mass for thermonuclear
fusion of deuterium that orbit stars or stellar remnants are "planets"
provided they do not have orbits that cross the orbits of other planets or
belts of material with orbits that follow the same standard as planets. The
minimum mass/size required for an object to be considered a planet should be
the amount needed to have gravity round the object.

Definition of a moon of an object
Any object orbiting planets that either border the Asteroid Belt of our
Solar System or are between the Asteroid Belt and the Solar System&#39;s outer
belt the TransNeptunian Belt and any object that while not a planet would be
considered a planet if what it orbits is treated as a star or stellar
remnant is a moon of that object with the exception that whatever
characteristic of a planet is lacking in the object treated as a star or
stellar remnant can lack in its moon.