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How many Goldilocks planets! - Comments

mmurray's Avatar Comment 1 by mmurray

Thanks for that. At last some numbers for the Drake equation. 500 million potentially life-bearing planets. Not too shabby.

Michael

Wed, 23 Feb 2011 10:58:35 UTC | #594882

Alan4discussion's Avatar Comment 2 by Alan4discussion

The Drake equation was an attempt to estimate the number of planets inhabitable by Earth life. It makes various assumptions which need to be evaluated to give meaningful results.

The team working the Kepler Space Telescope recently found another 54 exoplanets (5 Earth sized ones), bringing the total to 1,200, in a further 170 solar systems with more than one planet. Hopefully more will turn up soon. As the technology advances, numbers are rising all the time.

Many of these will be unsuitable for humans because of temperatures, pressures, gravity or radiation, but from the billions of stars and planets some should match up despite the rare nature of the Earth/Moon system. The Rare Earth Hypothesis would severely limit the planets suitable for humans.

Wed, 23 Feb 2011 11:21:52 UTC | #594892

Steve Zara's Avatar Comment 3 by Steve Zara

Who is Goldilocks? She was a person. What are we looking for - more little girls who meet bears? Remember that for most of the time life has been on Earth, Earth would not have been suitable for little girls. Remember that most of life on Earth lives in girl-unfriendly places. The depths of the oceans. Within the crust.

So are we looking for energy and water? Perhaps most of that is nowhere near Earth. It may be in the vast depths of the oceans of Europa, or the strange seas of Enceladus. Most liquid water in the solar system may be far away from this small ball of rock we call home.

So, I think we need to be clear about what we are looking for. If it is Earth like it is now, even Earth will be as it is now for no more than a month or so in the year of it's full lifetime. But perhaps we don't want to be clear what we are looking for?

The Goldilocks Zone is a hopelessly old fashioned way of looking for life. There are better ways: we look for systems far out of equilibrium, systems maintained in an odd state, just like our atmosphere.

But on the other hand, finding another Earth would be dead cool!

Wed, 23 Feb 2011 11:26:30 UTC | #594894

Alan4discussion's Avatar Comment 4 by Alan4discussion

Comment 3 by Steve Zara

But on the other hand, finding another Earth would be dead cool!

Starting with primordial porridge and just right for Goldilocks.

Investigations of Europa, or Enceladus would certainly give better projections for simple life. Stability over time and time to adapt to changes, would seem to be crucial.

Wed, 23 Feb 2011 11:38:12 UTC | #594895

anonymous.shyster's Avatar Comment 5 by anonymous.shyster

"The next question is why haven't they visited us?"

Most likely they are looking for intelligent life.

Wed, 23 Feb 2011 11:43:01 UTC | #594898

DavidMcC's Avatar Comment 6 by DavidMcC

Steve, perhaps we also need to be clear whether we are looking for just life, or intelligent life. The latter implies a rather more earth-like surface than the former. Enceladus and Europa are, after all, still candidates for the former, but almnost cedrtainly not the latter.

By "systems out of equilibrium", you obviously don't mean "solar systems out of equilibrium" (as with our own during the period of heavy bombardment), and obviously not very far out of equilibrium, since that would fit planets in highly eccentric orbits rather well, and they would not give life any real chance to get started, IMO.

Another point: Goldilox would not necessarily like most "Goldilox" planets anyway. For example, a very recently discovered one was orbiting a red dwarf (not unexpected, given that 80% of the stars in the Milky Way are red dwarves). That means that it would be gravitationally locked to its star. This, in turn means that, if it had a significant amount of surface water (and therefore an atmosphere to help prevent loss of that water), then it has been shown that it would have the mother of all hurricanes covering the star-ward half of it, so surface life would probably have to cling on on the edge of the dark zone, and only microbes, bacteria, etc would live elsewhere.

Wed, 23 Feb 2011 12:08:17 UTC | #594906

Cook@Tahiti's Avatar Comment 7 by Cook@Tahiti

In addition to liquid water, perhaps you need a stable long-lived single star, large moon for stable rotation, magnetic field for protection, a Jupiter big brother to protect against too many impacts, tectonic plates to regulate temperature via C & O cycles, and a whole lot of improbable good luck to get from single-cell microbes to 1300cc of neural wiring with language, tool use, and the empirical method.

Then you need to factor in Jared Diamond's Guns Germs and Steel thesis - that only a fortunate configuration of continents allowed cross-pollination of ideas, favourable climate, and domesticable plants and animals.

Australian Aborigines had remained technologically stable for 60,000 years. Progress can't be assumed, and regression is also possible. It's unlikely that any native tribes on isolated continents would have come up with radio astronomy.

Out of 4.5 billion years, we've had radio astronomy for about 100 years, with a Cuban Missile Crisis that almost set us back again.

The amount of obstacles a technologically advanced civilisation has to negotiate is staggering. There might be many more we haven't even discovered yet. Venus, the same size as Earth, is only a little closer to the sun and has temperatures to melt lead.

Wed, 23 Feb 2011 12:39:32 UTC | #594911

DavidMcC's Avatar Comment 8 by DavidMcC

Comment 7 by Rtambree :

In addition to liquid water, perhaps you need a stable long-lived single star, large moon for stable rotation, magnetic field for protection, a Jupiter big brother to protect against too many impacts, tectonic plates to regulate temperature via C & O cycles, and a whole lot of improbable good luck to get from single-cell microbes to 1300cc of neural wiring with language, tool use, and the empirical method. Then you need to factor in Jared Diamond's Guns Germs and Steel thesis - that only a fortunate configuration of continents allowed cross-pollination of ideas, favourable climate, and domesticable plants and animals.

Australian Aborigines had remained technologically stable for 60,000 years. Progress can't be assumed, and regression is also possible. It's unlikely that any native tribes on isolated continents would have come up with radio astronomy. Out of 4.5 billion years, we've had radio astronomy for about 100 years, with a Cuban Missile Crisis that almost set us back again.

The amount of obstacles a technologically advanced civilisation has to negotiate is staggering. There might be many more we haven't even discovered yet. Venus, the same size as Earth, is only a little closer to the sun and has temperatures to melt lead.

I'm sure Steve is aware of that, rtbramtree. We are only debating one aspect of the Goldilox conditions. It would be like saying that Goldilox would want her soup in a house that doesn't fall down as well as being just the right temperature. We just took that for granted. Sorry we didn't spelit out, though.

Wed, 23 Feb 2011 12:49:13 UTC | #594914

wynn's Avatar Comment 9 by wynn

"The next question is why haven't they visited us?"

When was the last time you visited the monkey cages at the zoo and tried to have a conversation with the inmates? Infidel, Satan!!

Wed, 23 Feb 2011 13:24:18 UTC | #594924

Alan4discussion's Avatar Comment 10 by Alan4discussion

Comment 6 by DavidMcC

Another point: Goldilox would not necessarily like most "Goldilox" planets anyway. For example, a very recently discovered one was orbiting a red dwarf (not unexpected, given that 80% of the stars in the Milky Way are red dwarves). That means that it would be gravitationally locked to its star.

I think there are two points here. First the issue of being locked in sychronisity would make the star facing side of a planet very hot and the dark side very cold, with severe climate implications. The second issue is red dwarves are noted for flaring up with fierce busts of destructive radiation on a regular basis. Brown dwarves, or Sun type mains sequence stars with an Earth/Moon type set up look like the best options for intelligent life. A large moon orbiting a very large planet in a "Goldilocks zone" could be another possibility.

Project ICARUS is a plan t o send an inter stellar probe

Using nuclear fusion propulsion.

It is a practical study by leading scientists.

Wed, 23 Feb 2011 13:31:26 UTC | #594926

Cook@Tahiti's Avatar Comment 11 by Cook@Tahiti

Comment 9 by wynn :

"The next question is why haven't they visited us?"

When was the last time you visited the monkey cages at the zoo and tried to have a conversation with the inmates?

The monkeys get visited all the time. We love to look at our closest relatives. Perhaps more appropriately, when's the last time you searched around for your local ants nest in order to study them?

Then again, we have entomologists. One would assume alien civilisations who also develop interstellar communications would also have their equivalent of entomologists. Some university academics that study primitive life on other planets. So where are they?

Maybe the distances are too great between each civilisation, given the slow speed of light. We've only been on the air for 100 years. If the nearest civilisation is in Andromeda 2m light years away, then for all intents and purposes they might as well not be there. Problem is this idea is unfalsifiable - there's no measurable difference between Earth being unique, and the Universe teeming with advanced civilisations that are too far away from each other to practicably communicate.

Wed, 23 Feb 2011 13:35:53 UTC | #594930

Cook@Tahiti's Avatar Comment 12 by Cook@Tahiti

Comment 10 by Alan4discussion :

Project ICARUS is a plan t o send an inter stellar probe

It's not really a plan, more a thought experiment. We're not going anywhere in the foreseeable future. Backwards possibly. Even the Shuttle will be retired this year. The USA won't even be able to put a person in low earth orbit any more, let alone the Moon or Mars or around other stars.

At present the energy requirements to send a 1000 ton ship to another earth-like planet (say 50 light years) within a couple of human generations, and have it survive particle collisions AND decelerate into orbit... is science fiction. At the rate we're "progressing", not in 1000 years. It would require some new type of exotic energy we haven't discovered yet.

Wed, 23 Feb 2011 13:43:27 UTC | #594934

Sample's Avatar Comment 13 by Sample

Goldilocks works for me. The earth is like one of those adjustable (just right) beds only instead of firmness and softness, it's also a bed of life-friendly topology from underwater thermal vents to the pelagic microbes of the atmosphere.

One of my dream jobs would be an astrobiologist trawling space with an as-of-yet uninvented extraterrestrial microbe/spore/particle tow behind an as-of-yet uninvented research vessel. I would require at least 12 weeks off per year. :-j

Mike

Wed, 23 Feb 2011 13:44:37 UTC | #594935

Alan4discussion's Avatar Comment 14 by Alan4discussion

Comment 12 by Rtambree

It would require some new type of exotic energy we haven't discovered yet.

You mean like this one which is not quite so far on in development planning?

Wed, 23 Feb 2011 14:00:44 UTC | #594942

aball's Avatar Comment 15 by aball

"The next question is why haven't they visited us?"

They may never visit us. The fact is that interstellar travel involves colossal distances and trip times that span generations. Einstein's theory of special relativity also doesn't help by imposing a speed limit and requiring huge amounts of energy to get anywhere near it. Travelling to the stars is a very hard thing to do.

If an advanced civilization exists 6000 light years from us, how likely are they to cross this distance to visit us? I have to admit that I don't know but I am skeptical about those chances.

Wed, 23 Feb 2011 14:01:43 UTC | #594944

DavidMcC's Avatar Comment 16 by DavidMcC

Comment 10 by Alan4discussion :

Comment 6 by DavidMcC

Another point: Goldilox would not necessarily like most "Goldilox" planets anyway. For example, a very recently discovered one was orbiting a red dwarf (not unexpected, given that 80% of the stars in the Milky Way are red dwarves). That means that it would be gravitationally locked to its star.

I think there are two points here. First the issue of being locked in sychronisity would make the star facing side of a planet very hot and the dark side very cold, with severe climate implications.

Alan, I agree. You probably didn't notice my comment 6 , above. It is a very fast-moving thread today!

Wed, 23 Feb 2011 14:14:58 UTC | #594952

Cook@Tahiti's Avatar Comment 17 by Cook@Tahiti

Comment 14 by Alan4discussion :

You mean like this one which is not quite so far on in development planning?

Hmm... article from 12 years ago. How's that project coming along? When skeptics were debunking the anti-matter plot device in the Angels & Demons movie, it was revealed that all the anti-matter manufactured in all the world's particle accelerators amounts to a minute fraction of a gram.

Yeah it might be possible one day in the far distant future. At present however, it seems the acceleration in transport technology that took off from the horse in the 19th century, to the train, car, plane, and rocket has hit a brick wall. Compare the 1890s - 1940s half-century, to the 1950s - 2000s. What new propulsion systems have we come up with in recent decades? I can only think of the Ion Drive (which is great for sending small payloads very slowly to the local neighbourhood).

Wed, 23 Feb 2011 14:18:29 UTC | #594955

Cook@Tahiti's Avatar Comment 18 by Cook@Tahiti

Comment 15 by aball :

"The next question is why haven't they visited us?"

They may never visit us. The fact is that interstellar travel involves colossal distances and trip times that span generations. Einstein's theory of special relativity also doesn't help by imposing a speed limit and requiring huge amounts of energy to get anywhere near it. Travelling to the stars is a very hard thing to do.

If an advanced civilization exists 6000 light years from us, how likely are they to cross this distance to visit us? I have to admit that I don't know but I am skeptical about those chances.

Well, it doesn't have to be about visiting. It can be just hearing from. Seth Shostak and Jill Tarter at SETI have been doing their best to listen for signals. SETI had its 50 year anniversary last year. Seth reckons that if we haven't heard anything in the next 20-25 years, given the broad spectrum of frequencies they can monitor full time now, then the pessimists may be right.

Wed, 23 Feb 2011 14:23:07 UTC | #594960

Schrodinger's Cat's Avatar Comment 19 by Schrodinger's Cat

I'm with the 'Rare Earth' hypothesists. I think we grossly over-estimate the chances of life elsewhere, and fail to grasp the sheer number of different elements that had to be 'just right' for our own evolution.

One of those aspects is the stabilising influence of the Moon, and the fact that the huge tides when the Moon first formed would have swept essential life-forming minerals into the sea. It's quite arguable that the Moon played a large part in the development of life here.

There are many other such factors. For example the amount of iron in the crust. Ironically this is also related to the formation of the Moon.....the re-melting of the Earth's crust led to a good deal more iron sinking to the core. If there were a third more iron in the crust than there is now......we would still have stromatolites struggling to oxygenate the atmosphere faster than iron could oxidise it into iron oxide.

These sort of examples show how everything is linked. Even the effect of water arriving on our planet when it did.......the timing was essential, to get those techtonic plates moving. When you add up all the things that had to be 'just right'...it goes well beyond simply being in some Goldilocks zone. I'd bet that there are probably billions of totally lifeless planets in Goldilocks zones.

Wed, 23 Feb 2011 14:47:07 UTC | #594973

DavidMcC's Avatar Comment 20 by DavidMcC

Comment 18 by Rtambree :

Comment 15 by aball :

"The next question is why haven't they visited us?"

They may never visit us. The fact is that interstellar travel involves colossal distances and trip times that span generations. Einstein's theory of special relativity also doesn't help by imposing a speed limit and requiring huge amounts of energy to get anywhere near it. Travelling to the stars is a very hard thing to do. If an advanced civilization exists 6000 light years from us, how likely are they to cross this distance to visit us? I have to admit that I don't know but I am skeptical about those chances.

Well, it doesn't have to be about visiting. It can be just hearing from. Seth Shostak and Jill Tarter at SETI have been doing their best to listen for signals. SETI had its 50 year anniversary last year. Seth reckons that if we haven't heard anything in the next 20-25 years, given the broad spectrum of frequencies they can monitor full time now, then the pessimists may be right.

Rtambree (I've spelt it right this time!), do you know what the range (in light years) is for the SETI project to have a reasonable chance of detecting radio signals that do not come from a transmitter that happenbs also to be a star? I'm thinking of something with only a few KW of power. I suspect that SETI is playing down the possibility that it can only "see" a few stars away, so they are blind to nearly all of the galaxy, and their negative results are almost inevitable

Wed, 23 Feb 2011 14:50:13 UTC | #594974

Schrodinger's Cat's Avatar Comment 21 by Schrodinger's Cat

Comment 18 by Rtambree

Seth reckons that if we haven't heard anything in the next 20-25 years, given the broad spectrum of frequencies they can monitor full time now, then the pessimists may be right.

It would simply mean that there's no current civilisation within radio communication distance...which is really only a few thousand light years. Below a certain frequency of life, it will appear to most civilisations that they are alone. That's the real problem......because one does not then know whether other life is just rare, or non-existent, as the observations will be the same.

It's a staggering thought that even if there's only 1 civilisation per galaxy ( which I suspect is closer to the mark ).....there's still over 200 billion civilisations in our universe.

Wed, 23 Feb 2011 14:59:44 UTC | #594978

aball's Avatar Comment 22 by aball

@DavidMcC

I have also wondered about the range of detection of the SETI project; and if SETI would actually recognise an alien signal as being intelligent.

Wed, 23 Feb 2011 15:00:51 UTC | #594979

Cook@Tahiti's Avatar Comment 23 by Cook@Tahiti

Comment 21 by Schrodinger's Cat :

It would simply mean that there's no current civilisation within radio communication distance...which is really only a few thousand light years. Below a certain frequency of life, it will appear to most civilisations that they are alone. That's the real problem......because one does not then know whether other life is just rare, or non-existent, as the observations will be the same.

That's the point I made in Comment #11 above.

It's a staggering thought that even if there's only 1 civilisation per galaxy ( which I suspect is closer to the mark ).....there's still over 200 billion civilisations in our universe.

And all alone, due to 'c'. The problem of 'c' has made hard (i.e. realistic) sci-fi boring, effectively killing it off as genre. Without tyrannical 'c', the golden age of science fiction was like the 18th century with ships zipping around the oceans discovering new islands/worlds, engaging in battles, love affairs, allliances, explorations, investigation, etc.

Wed, 23 Feb 2011 15:08:27 UTC | #594981

Cook@Tahiti's Avatar Comment 24 by Cook@Tahiti

Comment 22 by aball :

@DavidMcC

I have also wondered about the range of detection of the SETI project; and if SETI would actually recognise an alien signal as being intelligent.

Yes, they've thought of that - they're looking for anything that's not natural. We know what the natural cosmos sounds like. Noise from stars, nebulae, galaxies have certain shaped signatures (broad, distributed), while an 'intelligent' signal, even if we don't know what it means, would have a clean narrow signal that should be easy to discern if the transmitters know what they're doing. Short-pulse high-powered lasers is another medium we can investigate.

Wed, 23 Feb 2011 15:11:57 UTC | #594983

DavidMcC's Avatar Comment 25 by DavidMcC

Yes, Rtambree, I appreciate that, but what is the RANGE of detection expected to be, on the basis of a reasonable estimate of the power that the alien transmission would have (bearing in mind they are not likely to be harnessing a star for the purpose!). I found an article a few years ago, claiming to have shown that the range of detection could only be a few tens of light years. However, that would have been before SETI's recent upgrade to an array of their own.

Wed, 23 Feb 2011 15:33:18 UTC | #594987

Cook@Tahiti's Avatar Comment 26 by Cook@Tahiti

Comment 25 by DavidMcC :

but what is the RANGE of detection expected to be, on the basis of a reasonable estimate of the power that the alien transmission would have (bearing in mind they are not likely to be harnessing a star for the purpose!).

I've heard Shostak address this issue, and from memory his calculations show that it's a fair chunk of the galaxy (quadrant?). Somewhere between all the galaxy and just our local neighbourhood. He's optimistic it's enough to get a reasonable idea from statistical inference. After all, surveys can predict election results of a country of 300m with just a 1000 respondents.

The answer might be in here somewhere...

http://www.youtube.com/watch?v=SFFi3sWq5jE

Wed, 23 Feb 2011 15:56:26 UTC | #594993

DavidMcC's Avatar Comment 27 by DavidMcC

Thanks, Rtambree. Before they had their upgrade, I suspect that SETI was more like a guy who claimed to have a microphone that could pick up a conversation anywhere in his city, when all he could actually hear was his next-door neighbour, and only then when he was having a flaming row! :)

Wed, 23 Feb 2011 16:06:31 UTC | #594999

Al Denelsbeck's Avatar Comment 28 by Al Denelsbeck

Funny, I posted a three-part series of speculations on this some months ago, starting here. Lots of those factors can be held to debate, of course, but the overall impression is that there's a lot working against the whole idea - both from the development of "intelligent" life, and the likelihood that we'd ever hear anything. There are just too many variables to make more than a Wild-Assed Guess at the topic.

Just recently, I began to wonder about how evolution would progress with DNA (equivalents) that had different properties. Right now, change takes place only through mutational differences between the parent and the offspring, what might simply be referred to "transcription errors." But what if there was a function where gene changes could be influenced by the parents' environment? In other words, if the parent(s) began suffering from lack of a particular dietary need, and this could influence the genes passed on to subsequent offspring to adapt to this environmental change. Instead of transcription errors, species could more-or-less actively rewrite their genome in a single generation (albeit still in limited ways as it is now, but without the reliance on random mutation.) Speciation would take place exponentially faster, most likely producing much higher levels of competition, and perhaps even radically changing environments (such as the changes in oxygen production or carbon exchange from plant life that shifted to avoid predation.)

And in the other direction, a slower mutation rate might produce much shorter-lived species with higher extinction rates from their inability to adapt to environmental changes. Again, this might be exponential, where a mutation rate half of what life on Earth averages could result in four times or sixteen times slower development to "intelligence," if it made it at all due to frequent extinctions.

Much more fun to spend time on than philosophy ;-)

Wed, 23 Feb 2011 17:06:14 UTC | #595027

Cook@Tahiti's Avatar Comment 29 by Cook@Tahiti

Comment 28 by Just Al :

Much more fun to spend time on than philosophy ;-)

I've always wanted to ask Richard Dawkins about the rate of mutation. Is it just a happy coincidence the rate of mutation is just right for evolution to occur? Surely the overall rate itself can't be a product of selection, but more about the the background radiation, weakness hydrogen bonds, etc.

Didn't Isaac Asimov speculate about our large moon sucking up heavy elements (Uranium, etc) close to the crust during the early formation period, thereby allowing mutations to occur? No moon would mean heavier radioactive elements are deeper in the core which means less background radiation on the surface and a lower mutation rate less able to adapt to change. I don't know if this is a fringe or consensus position.

Wed, 23 Feb 2011 18:17:31 UTC | #595045

Alan4discussion's Avatar Comment 30 by Alan4discussion

Comment 16 by DavidMcC

Alan, I agree. You probably didn't notice my comment 6 , above. It is a very fast-moving thread today!

Actually I did, but when I quoted it I put in sychronisity to clarify the" locking" and added to it details about the Red Dwarves which you had raised.

Comment 25 by DavidMcC

I found an article a few years ago, claiming to have shown that the range of detection could only be a few tens of light years.

I would be sceptical about SETI signals. If a radio as recent as WW2 received a signal from a modern digital radio or TV, I doubt it would be recognised. Civilisations (if any) are likely to millennia or more apart.

Wed, 23 Feb 2011 19:30:08 UTC | #595074