 |
|
Cruddy
|
|
It depends on how you define rare and common...
...seeing as the universe mostly consists of nothing, I'd say it was very rare, compared to the amount of bugger all.
|
|
| |
|
|
|
Odin
|
 |
Biology Nerd at Minnesota State University Moorhead
Sep 2000
time: 23:37
|
|
quote:
Originally posted by Last Conformist
Well, only if the chances of life arising on a planet are high enough. From our present knowledge it seems unlikely, but it's for all we know possible that the origin of terrestrial life was a freak occurence, with a probability of say one in 10^80 (10^80 happens to be the approximate number of electrons in the observable universe).
quote:
Thirdly, Given that human life on this planet is reletivly young, and even life on this planet is fairly recent, many probes may well have passed and missed us.
|
I don't know if terran life can be said to be "fairly recent"; it's been around for closer to 4 billion years, which is an appreciable amount of time even on a galactic time scale. During that time, for instance, the average metallicity has risen enough to affect planet formation. |
Life is NOT a freak occurance. It can start anywhere with a source of liquid water, energy (lighting, UV light, heat from hydrothermal vents), and organics. The question is whether higher (complex multicellular) life will evolve. I think that can't happen on a Europa-like world, a biosphere needs photosynthesis if it wants to get to get anywhere.
|
|
| |
|
|
|
Darkstar
|
 |
Huntsville, AL, USA
May 1999
time: 23:37
|
|
quote:
Originally posted by Boris Godunov
The fringes, such as our arm, are where you're going to have to look, because the interior is to irradiated to support life-bearing planets. |
See, that's just the wrong answer. We are delicate about those matters, but anything that actually evolved there wouldn't be.
Now, if we just want to find mammalian life, then we know *precisely* what to look for... earth like worlds with one or more large satellites that receive a certain amount of radiation, and has undergone several large killing incidences so as to create an environ to allow mammals to become the dominate life form.
Of course, the desire to find "mammalian" life is probably more out of some teenage Star Trek fantasy then genuine interest in finding real intelligent life, but heh, I suppose that's the only hope until "holo-decks" are invented and installed in some people's houses.
|
|
| |
|
|
|
Darkstar
|
|
Huntsville, AL, USA
May 1999
time: 23:37
|
|
quote:
Originally posted by Odin
Life is NOT a freak occurance. It can start anywhere with a source of liquid water, energy (lighting, UV light, heat from hydrothermal vents), and organics. The question is whether higher (complex multicellular) life will evolve. I think that can't happen on a Europa-like world, a biosphere needs photosynthesis if it wants to get to get anywhere. |
See now, you've made two bad assumptions.
#1) Water required. We don't know that. We just know that on EARTH, water is the medium of life. But there are so many other suitable mediums. Water, being H2O, just is very common, and if we presume all life is water based, then we are already narrowing our search to just near liquid water conditions. Follow the water, and you should eventually find life is the presumption. This works okay for us, so long as we are speaking about a very limited economics to use to search for life, but it isn't very realistic in terms of where life could be harboured, grow and evolve, and perhaps became intelligent enough for us to communicate with.
#2) You presume life requires sunlight. Very bad. Current science now presumes that all life began deep in the ocean, where no light was found. Down at the tectonic plate boundaries... living off the heat and chemicals down there. It is now thought that life spread from there to what we think of as the normal life-ecosystems here at the surface. Why is it thought that way? Because early conditions on earth was like at the smokers, not like here. Earliest evirons. Life merely requires a source of energy. There's plenty of multi-cellular beings living down there. And so long as the energy-economy allows for better utilization of the energy source (or their harverters), then you get diversity (that's evolution). So, for Europa, all it needs is a steady energy source. Why does Europa have a liquid world ocean? Because of gravitational flexes caused by Jupiter in Europa's rocky core, generating pressure and heat. So, as long as things remain the same around Jupiter for Europa (on planteray scale), it will continue to flex, and give off energy.
|
|
| |
|
|
|
Urban Ranger
|
|
Apolyton Duke of Off-Topic
|
|
quote:
Originally posted by Darkstar
#1) Water required. We don't know that. We just know that on EARTH, water is the medium of life. But there are so many other suitable mediums. Water, being H2O, just is very common, and if we presume all life is water based, then we are already narrowing our search to just near liquid water conditions. Follow the water, and you should eventually find life is the presumption. This works okay for us, so long as we are speaking about a very limited economics to use to search for life, but it isn't very realistic in terms of where life could be harboured, grow and evolve, and perhaps became intelligent enough for us to communicate with. |
While that's true, water is the best medium there is, as far as we know.
- It stays at liquid form for a very broad temperature range
- It is very efficient in carrying heat
- It is an excellent solvent
- Ice flows on water
- Water absorbs a broad range of harmful radiation
I probably forgot a few 
|
|
| |
|
|
|
Odin
|
|
Biology Nerd at Minnesota State University Moorhead
Sep 2000
time: 23:37
|
|
quote:
Originally posted by Darkstar
#2) You presume life requires sunlight. Very bad. Current science now presumes that all life began deep in the ocean, where no light was found. Down at the tectonic plate boundaries... living off the heat and chemicals down there. It is now thought that life spread from there to what we think of as the normal life-ecosystems here at the surface. Why is it thought that way? Because early conditions on earth was like at the smokers, not like here. Earliest evirons. Life merely requires a source of energy. There's plenty of multi-cellular beings living down there. And so long as the energy-economy allows for better utilization of the energy source (or their harverters), then you get diversity (that's evolution). So, for Europa, all it needs is a steady energy source. Why does Europa have a liquid world ocean? Because of gravitational flexes caused by Jupiter in Europa's rocky core, generating pressure and heat. So, as long as things remain the same around Jupiter for Europa (on planteray scale), it will continue to flex, and give off energy. |
I said COMPLEX LIFE needed photosynthesis. Read the post before you spew stuff I already know. Chemoautothrophy is enough to sustain microbes, but animals need oxygen, and oxygen comes from photosynthesis, which cannot occur on Europa.
Life is most likely to start in water because water can desolve more things than any other natural substance and because it expands as it freezes. I'm not ruling it out, I'm just saying it's unlikely
|
|
| |
|
|
|
smacksim
|
 |
Deputy Chairman of the Council of Lords of Gaia
Feb 2004
time: 00:37
|
|
Considering all the new evidence for planets coming in, just this week even, my questions are:
When do you think we'll find a terran-like planet?
20 years, 40, 60, ? It will certainly be 15, until the new scopes are in orbit.
When will we find other life in the universe?
IE, how likely do you think it is that we'll find it on one of Sol's other rocks, or will we detect a methane-oxygen atmosphere (life for sure) on an extra-solar first? Or will it have to wait until we actually go somewhere else, which could be quite long.
And agree with Urban Ranger that animals, in the sense of multi-celled specialized-celled macroscopic critters with motility, don't necessisarily need Oxygen. But AFAIK the terran Kingdom Animalia depends utterly on Oxygen. Just think about photosynthesis. For a long time everyone believed there was only one photosynthetic pathway and energy cycle. Then CAM and C4 photosynthesis were discovered in Cacti. It is not at all inconceivable to imagine cellular respiration with other chemical models.
-S
Last edited by smacksim on 09-07-2004 at 09:31
|
|
| |
|
|
|
Darkstar
|
|
Huntsville, AL, USA
May 1999
time: 23:37
|
|
quote:
Originally posted by Odin
I said COMPLEX LIFE needed photosynthesis. Read the post before you spew stuff I already know. Chemoautothrophy is enough to sustain microbes, but animals need oxygen, and oxygen comes from photosynthesis, which cannot occur on Europa.
Life is most likely to start in water because water can desolve more things than any other natural substance and because it expands as it freezes. I'm not ruling it out, I'm just saying it's unlikely |
And you are COMPLETELY WRONG. We have COMPLEX LIFE at the bottom of the oceans that live PURELY inside eco-systems that never, ever, ever touch photosynthesis. You just need an energy source. You should go check out the smokers... and theres also the deep water super brine ecosystems. Both feature microbial life that fill that "photosysnethsis" energy harvestors that plants do on the surface. No photosynthesis involved. Those food chains goes up to highly advanced animals including crabs and octipi relatives. They are being studied very intensely by NASA... whole eco-systems that have ZERO input from sunlight, and have ZERO input from photosynthesis.
Water was convenient for us. That's why we need it. But again, that is merely one instance. We should not presume. Life, if it exists elsewhere, will use whatever is handy. That's the way of life. Now, if we want to go sit down and have tea with Intelligent life, it would be nice if they are mostly water, like us. Otherwise, it could be inconvienent trying to be around each other.
|
|
| |
|
|
|
Darkstar
|
|
Huntsville, AL, USA
May 1999
time: 23:37
|
|
Wrongo, Odin. There's sources for oxygen in the deep ocean that are completely unrelated. Remember, science currently believes they came first, before plants and photosynthesis. If that's so, that means there were no plants on the surface making O2 (that do not reach the deep waters in the first place, but you don't seem to be interested in that aspect). So they started utilizing oxygen before plants existed.
Honestly, I think it would do your interests a world of good to check out the latest on deep ocean eco-systems, the actors in the systems, etc etc etc.
And again, you presume.
All you need is electricity through H2O to get Oxy. And you can get that in an amazing number of ways. So, even if you say "You gotta have free oxygen!", then there is indeed the possibility to have free oxy roving around on Europa.
Heck, Europa isn't even the only water ocean moon in the solar system that we know of. So I don't know why you are so stuck on that one world.
And finally... when we begin talking about *life*, then you cannot accurately say quote:
all animals need oxygen |
That's cause we don't know that as a fact. We know that all terran animals need oxygen (not 100% true, but it is close enough for our discussion here).
We can presume many things by looking at what's in this one, isolated lab of life that we know of. Using it as a model, we can guess and hypothesize. But until we find other worlds full of life and can study them, we can not say that the only possiblity for complex life requires liquid water and oxygen. We can say, we know that complex life on earth require water and oxygen, and therefore life might repeat itself in some way under similar conditions. And that's what we really want. To find something very similar to ourselves out there that will be able to talk to us. And will bother to talk to us.
|
|
| |
|
|
|
Boris Godunov
|
 |
Portland, OR
Aug 2001
time: 00:37
|
|
quote:
Originally posted by Darkstar
See, that's just the wrong answer. We are delicate about those matters, but anything that actually evolved there wouldn't be.
Now, if we just want to find mammalian life, then we know *precisely* what to look for... earth like worlds with one or more large satellites that receive a certain amount of radiation, and has undergone several large killing incidences so as to create an environ to allow mammals to become the dominate life form.
Of course, the desire to find "mammalian" life is probably more out of some teenage Star Trek fantasy then genuine interest in finding real intelligent life, but heh, I suppose that's the only hope until "holo-decks" are invented and installed in some people's houses. |
I then suggest you take up some issues with your colleagues at NASA:
http://nai.arc.nasa.gov/news_storie...rint.cfm?ID=157
"Staying away from the galactic center has an additional advantage. The center of the Galaxy is awash in harmful radiation. Solar systems near the center would experience increased exposure to gamma rays, X-rays, and cosmic rays, which would destroy any life trying to evolve on a planet. "
There are other reasons why being closer to the center would be bad:
"Being in the outer region of the Galaxy protects our Solar System from the huge gravitational tug of stars clustered near the galactic center. If we were closer in, the combined gravity of all those stars would perturb the orbit of comets in the Oort cloud. The Oort cloud, which circles the outer perimeter of our Solar System, contains trillions of comets. The gravitational disturbances caused by other stars would send many of those comets in our direction - increasing the rate of comet impacts and endangering - if not eventually wiping out - life on Earth."
Overall, the article focuses on "Galactic Habitable Zones," which are indeed rare.
|
|
| |
|
|
|
DanS
|
 |
Kickball Capital of the World
Jan 1970
time: 00:37
|
|
quote:
And that's what we really want. To find something very similar to ourselves out there that will be able to talk to us. And will bother to talk to us. |
I agree that this is what we want, but economy suggests that this is a waste of time and money, considering that we would probably find them incidently while doing higher priority research, if they exist. For instance, we might find them while looking for worlds like ours. The highest imperative is to understand the broadest range of life on such worlds.
Sometimes I become frustrated when I hear about money going to SETI. Drake's equation seems like it is used to justify the work. Of course, people (like me) waste enormous sums of money on new plasma TVs too, so as long as it's not the government spending the money...
Last edited by DanS on 09-07-2004 at 22:27
|
|
| |
|
|
|
child of Thor
|
|
I think the universe is teeming with 'intelligent' life - thats why they haven't contacted us yet as we are too stupid to probably keep ourselves or our planet alive.
|
|
| |
|
|
|
DanS
|
|
Kickball Capital of the World
Jan 1970
time: 00:37
|
|
One of the problems with Drake's Equation is that you get stupid arguments like the following one, which banks on concensus "science" to assert a fact that can neither be argued against nor verified. When did science start running on such stuff?
quote:
First Contact Within 20 Years: Shostak
Will the 20s see ET roar onto center stage
Mountain View CA (SPX) Jul 22, 2004
If Intelligent life exists elsewhere in our galaxy, advances in computer processing power and radio telescope technology will ensure we detect their transmissions within two decades. That's the bold prediction from a leading light at the Search for Extraterrestrial Intelligence Institute in Mountain View, California.
Seth Shostak, the SETI Institute's senior astronomer, based his prediction on accepted assumptions about the likelihood of alien civilisations existing, combined with projected increases in computing power.
Shostak, whose calculations will be published in a forthcoming edition of the space science journal Acta Astronautica, first estimated the number of alien civilisations in our galaxy that might currently be broadcasting radio signals.
For this he used a formula created in 1961 by astronomer Frank Drake which factors in aspects such the number of stars with planets, how many of those planets might be expected to have life, and so on. Shostak came up with an estimate of between 10,000 and 1 million radio transmitters in the galaxy.
To find them will involve observing and inspecting radio emissions from most of the galaxy's 100 billion stars. The time necessary for this formidable task can be estimated from the capabilities of planned radio telescopes- such as SETI's 1-hectare Allen Telescope Array and the internationally run Square Kilometre Array- and expected increases in the power of the microchips that sift through radio signals from space.
Shostak assumed that computer processing power will continue to double every 18 months until 2015- as it has done for the past 40 years. From then on, he assumes a more conservative doubling time of 36 months as transistors get too small to scale down as easily as they have till now.
Within a generation, radio emissions from enough stars will be observed and analysed to find the first alien civilisation, Shostak estimates. But because they will probably be between 200 and 1000 light years away, sending a radio message back will take centuries.
Paul Shuch, executive director of the SETI League, a separate organisation in New Jersey, says Shostak's prediction ignores one important factor. "It is altogether reasonable to project the development of human technology, based upon past trends and planned investments," he says.
"But predicting the date, the decade or even the century of contact is another matter because the 'other end' of the communications link is completely out of our hands. It would be nice to think we know something about the existence, distribution, technology and motivation of our potential communications partners in space, but in fact, we don't."
Shostak admits that there are myriad uncertainties surrounding his prediction, but he defends the basis on which he made it. "I have made this prediction using the assumptions adopted by the SETI research community itself." |
http://www.spacedaily.com/news/seti-04e.html
|
|
| |
|
| |
All times are GMT. The time now is 05:37.
Apolyton Time is 00:37. |
top of page
|
| archivepost |
|
Forum Rules:
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
|
HTML code is ON
vB code is ON
Smilies are ON
[IMG] code is ON
|
|
|
|
|
|
05-07-2004 21:33
those animals could nor have evoled in the first place if PHOTOSYNTHESIZERS hadn't made oxygen. Remember, ALL animals need oxygen, many microbes don't. There is a huge difference between bacteria and tube worms. There can be no photosynthesizers on Europa, hence NO OXYGEN FOR ANIMALS.
|