22 replies to this topic

[Live Forever]

Here is a link to a story about three potentially habitable planets that have been found around a nearby "Sun-like" star. While all of the planets are still quite a bit bigger than Earth (10, 12, and 18 times the size of our planet), I suppose the scientists think there is a better chance for life than the much bigger gas giants which have been the only ones discovered up to this point. I can't wait until we get some more powerful telescopes up into space that will allow for the discovery of smaller Earth-sized planets.

[rodentman]

The technique they use to find extrasolar planets, really only finds systems that are unlikely to have potentially habitable planets. Usually, they need a larger Jupiter-sized planet, orbiting close to the Star, for it to show up as a gravitational wobble. Systems like ours, that have larger gas giants on the outskirts, that help draw away incoming asteroids, and other heavenly bodies, cannot be detected as of yet with the 'wobble' signature.

RodentMan

[Live Forever]

The technique they use to find extrasolar planets, really only finds systems that are unlikely to have potentially habitable planets.  Usually, they need a larger Jupiter-sized planet, orbiting close to the Star, for it to show up as a gravitational wobble.  Systems like ours, that have larger gas giants on the outskirts, that help draw away incoming asteroids, and other heavenly bodies, cannot be detected as of yet with the 'wobble' signature. 

RodentMan

You are correct. Which is why these planets are so special, I suppose, since they are the "smallest" ones detected to date, and are unlikely to be gas giants like the others they have detected.

[rahein]

I think they could a planet a few months ago that was earth size (20-30x bigger IIRC) by directly measuring the change in light of the star. I think this planet was close (inside) the habitable zone though. I can’t find the article now of course.

[rodentman]

I don't think we'll really see a lot of potentially habitbal planets until the 'Terrestrial Planet Finder' (TPF) project in 2015. By then, I wouldn't be surprised if we already had the beginnings of a space elevator in place, and the TPF could be replaced by something much more massive, and more sensitive.

RodenMan

[mikelorrey]

Keep in mind that even jovian class planets around other stars, so long as they orbit in that stars habitable zone, can theoretically have quite habitable moons, possibly even as large as Earth. Given the number of moons around our jovians, we should take it as a given that any jovian in a stars habitable zone should have at least one or more life bearing moons.

[MichaelAnissimov]

All planets are 'habitable'. You just have to modify human biology a bit. Or surround a normal human with a protective envelope of transparent nanomachinery.

any jovian in a stars habitable zone should have at least one or more life bearing moons

Or none? Just because a celestial body is in a 'habitable zone' doesn't mean it has life. If life were so common, it would be here by now.

As we see frequently, the boring explanation - life just doesn't pop up that easily - is more plausible than the exciting explanation - a "Great Filter" that mysteriously causes all alien races to either destroy themselves or forever turn inward.

[Live Forever]

As we see frequently, the boring explanation - life just doesn't pop up that easily - is more plausible than the exciting explanation - a "Great Filter" that mysteriously causes all alien races to either destroy themselves or forever turn inward.

Unfortunately we won't know for sure until we are able to visit a few hundred solar systems, and even then it might just be our area of the galaxy that is less than habitable, in which case we would need to explore a larger portion of the Milky Way, and even then it might just be our specific galaxy that is less than habitable, in which case we would need to explore a few hundred other galaxies, and even then it might just be our area of the universe that is less than habitable, in which case we would need to....

Ok, I am out of breath.

[mikelorrey]

All planets are 'habitable'.  You just have to modify human biology a bit.  Or surround a normal human with a protective envelope of transparent nanomachinery.



Or none?  Just because a celestial body is in a 'habitable zone' doesn't mean it has life.  If life were so common, it would be here by now.

As we see frequently, the boring explanation - life just doesn't pop up that easily - is more plausible than the exciting explanation - a "Great Filter" that mysteriously causes all alien races to either destroy themselves or forever turn inward.

Nope. Life is easy. Interstellar travel is what is hard, expensive, with no profit incentive. The energy budget alone is huge for a one way no-slow-down trip. By the time it becomes affordable, the species has advanced to the point that there is no significant benefit.

Just look at how telescope technology is advancing. There is even a proposal for one to be orbiting out past Pluto that would use the Sun's gravity as a giant lens. By the time we can build interstellar probes, we'll be able to observe other terrestrial planets and moons directly, which will eliminate a lot of the reason for going, at least long enough that we'll become so posthuman that any species elsewhere simply would not recognise us as such unless they were already near our level. Similarly, here on Earth, there is nobody who would be capable of recognising a piece of crypto dirt as an alien civilization. Nor would we be worth travelling to to visit if their goals were to recreate their original bodies here: we don't have the tech yet to assist them. Its like trying to send an email to someone who has a phone but no computer: they are unable to recognise the message as anything but screeching.

[spins]

Keep in mind that even jovian class planets around other stars, so long as they orbit in that stars habitable zone, can theoretically have quite habitable moons, possibly even as large as Earth. Given the number of moons around our jovians, we should take it as a given that any jovian in a stars habitable zone should have at least one or more life bearing moons.

I agree, it has been speculated that most life in the universe will occur on large moons orbiting gas giants in the habitable zone as this seems to be the most common type of solar system.

Solar systems such as our own with the small rocky planets orbiting close to the parent star and gas giants orbiting in the outer reaches seem to be less common.

Obviously the only problem with life forming on a moon around a gas giant is there is a greater risk of asteroid or comet impact. Having our gas giants in the outer solar system has completely the opposite effect.

For this reason maybe intelligent life would be less likely to evolve and gain a foothold on moons orbiting gas giants than on small rocky planets in a solar system like ours. Not to mention there would be much more radiation on a moon orbiting a gas giant.

[Clifford Greenblatt]

MichaelAnissimov

All planets are 'habitable'.  You just have to modify human biology a bit.  Or surround a normal human with a protective envelope of transparent nanomachinery.

Could we go further to say that all stars are possibly habitable? A star is a source of enormous energy or mass. An extremely clever and advanced system may be capable of mining stars and enveloping them with orbiting life support environments. Stars may not have all the elements needed for construction of the life supporting environments, but extraordinarily advanced particle colliders could possibly convert helium and hydrogen to all required elements.

[emerson]

Nope. Life is easy. Interstellar travel is what is hard, expensive, with no profit incentive. The energy budget alone is huge for a one way no-slow-down trip. By the time it becomes affordable, the species has advanced to the point that there is no significant benefit.

Not to mention that the concept of an intelligent species giving a second, or even first, thought to the idea of expanding past their immediate environment makes a lot of assumptions about the nature of sentience. It's hard to know how much of what we think of as traits that would be universal among any intelligent being are instead rationalisations placed over instinctual ape behaviour.

[caston]

Try the Drake equation. Estimates of the number of intelligent and communicating civilisations in the milkway galaxy range from 1 to numbers in the millions. Personally I think it's something like 10,000.

http://www.activemin...e_equation.html

Some people even believe that Pulsars are the galactic equivalent of the communication satellite because their pulse rate is so constant. This is commonly doubted, however.

How many advanced species could have developed faster than light travel? That is the real question.

[mikelorrey]

Try the Drake equation. Estimates of the number of intelligent and communicating civilisations in the milkway galaxy range from 1 to numbers in the millions. Personally I think it's something like 10,000.

http://www.activemin...e_equation.html

Some people even believe that Pulsars are the galactic equivalent of the communication satellite because their pulse rate is so constant. This is commonly doubted, however. 

How many advanced species could have developed faster than light travel? That is the real question.

Ah, good question. The Drake Equation is something we'll have more hard data on within a few decades, as jovian moons get explored, and Mars is more extensively explored to determine if it ever held life. If we are optimistic, and assume that Mars once held life that was killed off, and two moons of jupiter and one of Saturn hold benthic life forms under the ice, then we can come up with a rough guestimate that stars with planets in near circular orbits bear life 40% of the time on the planets or their moons. 4/5 of lifebearing ecologies survive climatic changes, and 1/5 of life bearing planets develop intelligent life.

I'm also going to go out on a limb and declare that if you are smart enough to figure out how to build nuclear weapons, or engineer pandemic diseases, you are smart enough to figure out what a dumb idea it is to exterminate your species with them, at least 50% of the time. However, I'll also say that, unlike nuclear holocaust, a natural instinct against mutation or malformation, survival xenophobia/luddism, will be a huge force against acheiving uploading.

I'm going to be practical and assume that FTL does not exist for macro-sized beings like us. Its too damn expensive to move meat from star to star. I will also say that meat people don't interest data people except as research subjects, or perhaps pets, but never explain to them the data persons true nature, so we'll never interact toe to toe with alien species until after uploading. If your species remains luddite, you never meet the aliens.

[caston]

Ah, good question. The Drake Equation is something we'll have more hard data on within a few decades, as jovian moons get explored, and Mars is more extensively explored to determine if it ever held life..

What about Venus? Of course we will probably never be able to find out if Venus was once cool enough to have a large ocean and support life.

[mikelorrey]

Venus started off with 92 times more atmosphere than Earth has now. Earth started off with 52 times more atmosphere than Earth has now, and in a much cooler locale. From the estimates of the amount of water that would have been there to start with, I'm on the doubtful side. Venus was never even as wet as Mars was.

[caston]

It's much harder to keep water liquid with such low pressure. If there was water on mars I think that an increase in the suns brightness quickly caused it to evaporate. The only thing left is the brine we see today and perhaps the ice caps.

[caston]

Another interesting thought is the fact that there's billions of other galaxies. Here we are living on this deathist planet while the vast majority of the intelligent life in the universe is comprised of immortals.

[mikelorrey]

It's much harder to keep water liquid with such low pressure. If there was water on mars I think that an increase in the suns brightness quickly caused it to evaporate. The only thing left is the brine we see today and perhaps the ice caps.

I'd suggest obtaining Martyn Fogg's seminal text "Terraforming" if you want to reach informed opinions on the issue.

Today's sun is about as bright as its ever been. In the early period when Mars was wet, the Sun was actually dimmer than it currently is by a significant margin. Mars had more atmosphere, but, due to a lack of a moon-maintained magnetic field strong enough to shield it from solar wind, much has been stripped off over the ages, and much of the rest has been absorbed in carbonate formations due to the dropping temperature.

A small increase in Mars' temp today would lead to a vicious cycle outgassing of CO2 that would result in an atmosphere and climate similar to Tibet within about 30 years time.

Current Mars orbiters are finding so much subsurface water ice today that the sort of seas projected by Kim Stanley Robinson can be realized with sufficient warming.

[mikelorrey]

Another interesting thought is the fact that there's billions of other galaxies. Here we are living on this deathist planet while the vast majority of the intelligent life in the universe is comprised of immortals.

You know this?

If even a small percent of intelligent species survive their singularities to become immortal species, this is likely true, but at the same time, such have no intent, likely, of involving themselves with any species so agressive, hostile, and xenophobic that it would prefer its own destruction rather than change.

This is also a good reason supporting the Simulation Argument: the Drake Equation not only applies only to races in this galaxy, but races that exist as radio emitting civilizations RIGHT NOW in this galaxy. Even if you take the most cynical values for the Drake equation, this still means that tens of thousands, if not millions or billions of intelligent species surviving their singularities over the life of this universe.

If only two species survive their singularities per universe, and odds of immortals creating simulation universes is a mere 50%, then odds of any one universe being a simulation exceeds 99.999999'%.

[caston]

I hope what you say about mars is true but until now most of what I have read has been talking in terms of multiple life-spans. Could be 30 mins to thaw and heat the pie but for how long do we preheat the oven? so to speak

Also here is something about water:
http://www.lsbu.ac.uk/water/phase.html

Here is the website of Martyn Fogg:

http://www.users.glo...mfogg/index.htm

Edited by caston, 21 June 2006 - 09:25 PM.

[Infernity]

Sp funny how we hardly know all the creatures on earth and we try to figure if those in space. Few weeks ago there was another scorpion species found in Israel, that wasn't known ever before, All the depth of the ocean, humph. I still think, though that we will find living creatures on other plants other than them finding us. I tend to think we are very capable creatures.

-Infernity

[caston]

It's hard to know what will happen but the vastness of space, sheer statistics and probability tells me we are in for some big surprises in our future.