[Tyler_JC]

While I love the idea of interstellar colonization, I just don't think it will ever be technologically workable.

The Saturn rocket used 10^11 joules of energy. The difference between the Wright Brothers plane and the Saturn rocket was only 4 orders of magnitude.

But we would need a rocket nearly 100 billion times more powerful than the Saturn rocket to get to Gliese 581g in any reasonable length of time. And even flying at 1/10 the speed of light would still take over 200 years.

[Sixstrings]

While I love the idea of interstellar colonization, I just don't think it will ever be technologically workable.

The Saturn rocket used 10^11 joules of energy. The difference between the Wright Brothers plane and the Saturn rocket was only 4 orders of magnitude.

On the other hand, the Wright Brothers would probably have thought the idea of the Saturn rocket technologically unworkable.

But you may be right. Logically, our solitude on this planet is the greatest proof that interstellar travel may be out of reach. If it were possible, then somebody would have paid us a visit by now. Unless we're the only intelligent organism in the galaxy, though that's statistically unlikely.

[Tyler_JC]

While I love the idea of interstellar colonization, I just don't think it will ever be technologically workable.

The Saturn rocket used 10^11 joules of energy. The difference between the Wright Brothers plane and the Saturn rocket was only 4 orders of magnitude.

On the other hand, the Wright Brothers would probably have thought the idea of the Saturn rocket technologically unworkable.

But you may be right. Logically, our solitude on this planet is the greatest proof that interstellar travel may be out of reach. If it were possible, then somebody would have paid us a visit by now. Unless we're the only intelligent organism in the galaxy, though that's statistically unlikely.

There is a limit to how much energy we can get from the Sun on a daily basis. In the past, life on earth under-consumed this resource, leading to a large surplus of stored energy (fossil fuels).

We can over-consume this resource now but only because someone under-consumed it in the past.

So we can go from burning wood to burning diesel and do this for several centuries but at some point, we'll be limited to how much new energy enters the system from the Sun.

The idea that we could ever consume several year's worth of sunlight on one project just doesn't make sense. There isn't enough stored energy to make it work.

Between 1900 and 1969, US energy use per capita roughly tripled. In that time, we could increase the power of our best flying machine by 4000 times.

But that meant diverting energy from non-flying use to flying machines. To increase the power of our flying things by another 4000 times, we would need MORE than a tripling of energy availability because otherwise, we would have nothing left over for the rest of society. Total energy use and flying machine energy use have to roughly track each other if we don't want to starve the rest of society.

So a machine that is several billion times more powerful than the Saturn rocket, will require a substantial increase in energy availability per capita.

My design for an interstellar craft required 5000 times more energy than the human species used in 2007. Does anyone think a 5000 fold increase in energy use is coming any time soon? And if so, does anyone think ALL of that increase is going into the fuel tank of 1 rocket?

[yeahbut]

Logically, our solitude on this planet is the greatest proof that interstellar travel may be out of reach. If it were possible, then somebody would have paid us a visit by now. Unless we're the only intelligent organism in the galaxy, though that's statistically unlikely.

One factor I don't often hear included in calculations of the statistical likelihood of other intelligent lifeforms in the galaxy (100 billion stars, many it seems now with planets, a healthy percentage of those planetary systems having a candidate for life-providing conditions etc) is time. Yes, there may well be a very large number of planets that might produce life of some kind(and possibly in a tiny fraction of those, intelligent life that we could recognise), but they are not only seperated from us by the vast gulf of space. We are adrift in an immense ocean of time, also. The age of the universe is currently held to be around 14 billion years or so, the earth 4.4 billion. Plenty of time for a species to arise and wink out of existence again, millions of times over. What are the odds of an intelligent life-form arising anywhere near us both in space and time? Unless one holds that, once sentient, a species would avoid the usual path to eventual extinction, they would have to be vanishingly remote, I would have thought.

[Sixstrings]

So we can go from burning wood to burning diesel and do this for several centuries but at some point, we'll be limited to how much new energy enters the system from the Sun.

At present, we fuel our society with PAST solar energy. Once we shift toward tapping PRESENT solar energy then it's pretty limitless (only limitation being the raw material to manufacture solar power equipment). And then there's fusion energy, an even more direct forum of solar energy (fusion is the process that fuels the sun itself).

Yes, in five billion years the sun will expand into a red giant and overtake Earth. So that's the only limit to solar energy, the 5 billion years we have until our sun boils off all our oceans and possibly engulfs us.

5 billion years is a very long time. If I remember correctly, I read that the star Gliese will last billions of years longer than our sun. So that's actually quite a bit of time to get off this planet and over to Gliese 581g -- assuming of course we don't collapse to the Stone Age and never advance again and all that. But then 5 billion years is also long enough for another of Earth's species to develop intelligence; maybe we won't make it, but descendants of chimpanzees will.

One factor I don't often hear included in calculations of the statistical likelihood of other intelligent lifeforms in the galaxy (100 billion stars, many it seems now with planets, a healthy percentage of those planetary systems having a candidate for life-providing conditions etc) is time.

We're in one of the outer rings of the Milky Way Galaxy. I don't think stars deeper in the galaxy are necessarily older or younger? As far as I know, there's a cycle that's been ongoing all across the universe since the big bang. And so there are countless systems that are at about the same stage of evolution as we are.

Not to get off subject, but what I find really interesting is what happens at the end of the universe. It used to make sense to me that it was all a big cycle, big bang - expansion - then contraction - then another big bang. But I believe the latest evidence suggests the universe will just keep expanding into infinity, destroying all matter forever. Which makes things harder to understand; to me anyway, a never ending cycle is more comprehensible than a definite beginning and a definite end.

[yeahbut]

One factor I don't often hear included in calculations of the statistical likelihood of other intelligent lifeforms in the galaxy (100 billion stars, many it seems now with planets, a healthy percentage of those planetary systems having a candidate for life-providing conditions etc) is time.

We're in one of the outer rings of the Milky Way Galaxy. I don't think stars deeper in the galaxy are necessarily older or younger? As far as I know, there's a cycle that's been ongoing all across the universe since the big bang. And so there are countless systems that are at about the same stage of evolution as we are.

I'm not sure if I'm getting your meaning there Six, are you saying that there is a fairly similar age of stars across our galaxy? If so, that's not correct. All the stars within a cluster can be assumed to be very close in age, because they all formed from the same gas/dust cloud, but the ages of the clusters themselves vary from still forming, to 'brand new', to nearly as old as the universe itself. For instance, the Pleiades are about 100 million years old, and the stars in Omega Centauri are estimated to be 12 billion years old. Given that there is an only a certain window of age for both star and planet in terms of conditions conducive to life (in our own case, complex life has only found a foothold for ten percent of our planet's life up to this point, tool-making primates .005%), I still hold that we have to intersect both in space and time- surely a much taller order.

btw, I think that's what I like about this site more than anything else- it's always making me want to learn new stuff. Your post made me realise I didn't know about the relative ages of stars in our galaxy, and made me want to find out.

Not to get off subject, but what I find really interesting is what happens at the end of the universe. It used to make sense to me that it was all a big cycle, big bang - expansion - then contraction - then another big bang. But I believe the latest evidence suggests the universe will just keep expanding into infinity, destroying all matter forever. Which makes things harder to understand; to me anyway, a never ending cycle is more comprehensible than a definite beginning and a definite end.

Indeed. I always found the notion of an expanding and then collapsing universe comforting in a strange way- it's almost like breathing, or birth and death. It is comprehensible, it can be related to life. A universe that expands forever into dissolution and heat death, until everything is utterly seperate and absolutely cold is a very bleak notion. There's no comfort to be found in that- personally I'm holding out for the revival of the old theory

[EnergyUnlimited]

Logically, our solitude on this planet is the greatest proof that interstellar travel may be out of reach. If it were possible, then somebody would have paid us a visit by now. Unless we're the only intelligent organism in the galaxy, though that's statistically unlikely.

One factor I don't often hear included in calculations of the statistical likelihood of other intelligent lifeforms in the galaxy (100 billion stars, many it seems now with planets, a healthy percentage of those planetary systems having a candidate for life-providing conditions etc) is time. Yes, there may well be a very large number of planets that might produce life of some kind(and possibly in a tiny fraction of those, intelligent life that we could recognise), but they are not only seperated from us by the vast gulf of space.

We really don't know how life is forming from normal non living matter.
At this early stages no natural selection can take place as there are no replicators.
It also seem improbable that features like photosynthesis or Krebs cycle are a product of natural selection (take away or modify 1 enzyme out of 100 necesserary and remaining lot is entirely useless)
This flies into face of Information Theory.
We do not know how life is formed, but if it indeed appeared by pure chance and cannot spread through vacuum of space (and then show up here and there), then we are in all probabilities alone in Universe.
And there are zillions of Universes very much like ours with zillions of zillions of planets in each one and we are still alone there.

Plenty of assumptions are made about what is needed to form life.
It is said that water, right temperature range and right composition of atmosphere are needed between plenty of other things.

However one, perhaps most important thing is missing here:
initial load of information is also needed.
Information does not appear out of nothing by pure chance, and if it does, then the odds for that are incredibly low.
These odds are as low as temporary breaches of 2nd Law of Thermodynamics, which are also possible in theory as shown by Statistical Mechanics, but nevertheless rare enough not to bother with it.
Needless to say time is ironing out these even if occur, so in longer run 2nd Law is safe.

Actually you can connect Thermodynamics with Information Theory (read about Maxwell's Demon)

So until we can show that there are certain paths to life which are likely to be followed, we demonstrate that life favoring chemistry is intrinsic property of matter making Universe and we show from where initial information as per requirements of Information Theory is drawn, we must assume that we are a product of incredible fluke, and as such we are alone in Universe.

Alternatively we may start calling in deities but this solves nothing as it is still a mystery from where these came to existence (it is just kicking can down the road).

Don't you think that SETI's failures might be a hint of our peculiar situation?

[yeahbut]

Don't you think that SETI's failures might be a hint of our peculiar situation?

Definitely. If the galaxy is teeming with intelligent life, why is it so shy? Of course, the absence of discernable communication could just mean that life doesn't necessarily become sentient, in most cases it just stays at a single cell level, or reptilian equivalent or whatever and our species is the fluke, not life itself. Or we are still so primitive and stupid that we don't have the tech to recognise alien communication. Or that it is too far away in space, on the other side of the galaxy, or in another galaxy. Or too far away in time, arisen and disappeared long ago. Probably Occam's razor applies tho, eh?

As for the information theory part of your post, I am too primitive and stupid to have anything useful to add, I'm afraid

[EnergyUnlimited]

As for the information theory part of your post, I am too primitive and stupid to have anything useful to add, I'm afraid

To enlighten yourself a bit, you may begin with this:
http://www.amazon.com/Information-Theor ... 0521802938
Book is dealing with emergence of life and evolution in context of Information Theory.

This is well balanced book, written by prominent and respected physicists.

While researching this subject, which is quite contentious one needless to say, it is very easy to bump on plenty of stupid arguments from creationists and equal amount of comparably stupid arguments from militant atheists, so be careful.

[rangerone314]

Maybe Gliese 581g may turn out to be the first planet with intelligent life. (including the Earth, since it is only inhabited by kudzu apes)

[Serial_Worrier]

It's extremely unlikely that Gliese 581g has anything more then microbial life in the deep sea. That's just my gut feeling about it. We are special in the universe!

[Sixstrings]

I'm not sure if I'm getting your meaning there Six, are you saying that there is a fairly similar age of stars across our galaxy? If so, that's not correct. All the stars within a cluster can be assumed to be very close in age, because they all formed from the same gas/dust cloud, but the ages of the clusters themselves vary from still forming, to 'brand new', to nearly as old as the universe itself.

I think I misunderstood what you were saying about stars being separated in time. I guess you meant separated as in the time required to travel between them?

Within our galaxy, there's a cycle for death and birth of new solar systems. So yes ages vary. Galaxies are also in motion, some will collide and we've observed some in the process of colliding. New nebulae can arise from these collisions, and then condense into new stars and planets.

Stars can also collide, or lock each other into a binary orbit. Novae create new nebulae. Our own sun won't ever go nova, but when it collapses to white dwarf it will create a new nebula from all the mass it will shed.

Here's an interesting thought.. aren't the stars in the milky way denser as you get closer to the center? Here's where we are:



We're sort of out in the boonies. Further in, the stars are closer to each other. It could be there are tens of thousands of aliens who are just close enough to have contact, but being out near the edges we're missing the party. Or the inter-stellar wars for all we know.

Indeed. I always found the notion of an expanding and then collapsing universe comforting in a strange way- it's almost like breathing, or birth and death. It is comprehensible, it can be related to life. A universe that expands forever into dissolution and heat death, until everything is utterly seperate and absolutely cold is a very bleak notion.

Then again, if certain quantum theories are correct then there are infinite universes. Every time you do one thing instead of another, you create an alternate universe wherein you did that other thing instead. Which fits in nicely with the Buddhist and Hindu ideas of Karma, that personal actions have a karmic effect on the universe as a whole.

The expanding / contracting universe theory also fits into Buddhism; but if heat death is the reality and there is no universal cycle, just a beginning point and an end point and then I guess the Christians end up closer to the truth.

[EnergyUnlimited]

Stars can also collide, or lock each other into a binary orbit. Novae create new nebulae. Our own sun won't ever go nova, but when it collapses to white dwarf it will create a new nebula from all the mass it will shed.

As per current understanding of stellar evolution Sun will go nova but it will not go supernova.
Nova will be a terminal part of its red giant phase.
After nova it will proceed to white and then black dwarf status.

Further in, the stars are closer to each other. It could be there are tens of thousands of aliens who are just close enough to have contact, but being out near the edges we're missing the party. Or the inter-stellar wars for all we know.

If stars are too close to each other, there won't be stable planetary orbits and advanced life is unlikely to evolve.

Then again, if certain quantum theories are correct then there are infinite universes. Every time you do one thing instead of another, you create an alternate universe wherein you did that other thing instead. Which fits in nicely with the Buddhist and Hindu ideas of Karma, that personal actions have a karmic effect on the universe as a whole.

True.
However if Copenhagen interpretation of QM is correct, then all these alternative -verses are fantasy.

The expanding / contracting universe theory also fits into Buddhism; but if heat death is the reality and there is no universal cycle, just a beginning point and an end point and then I guess the Christians end up closer to the truth.

Heat death is not an end but it is a state of eternal boredom.
I would hate to find myself immortal (say as a soul) and face prospects of heat death of Universe.
The worst possible fate, one can imagine - face eternity in empty space with no hope to do anything about it.

There is a better end of Universe scenario.
Read about Big Rip.
If correct, it would bring Universe to conclusive end.
Some observations are supporting this scenario, some other don't.

[Serial_Worrier]

We're sort of out in the boonies. Further in, the stars are closer to each other. It could be there are tens of thousands of aliens who are just close enough to have contact, but being out near the edges we're missing the party. Or the inter-stellar wars for all we know.

Not likely. The closer stars are the more unlikely stable, life-giving planets are to form. Also you get bombarded by at least 2x the radiation we get out in the suburbs. I find the idea of any life among the globular clusters to be zero.

Most likely there are intelligent beings besides us on the outer spiral arms but we're all too primitve to make contact yet. Our androids will meet theirs one day.

[Tyler_JC]

Although a little radiation is helpful if it encourages genetic mutation which promotes evolution.

So there could be life closer to the galactic center but not anywhere near the exact center itself.

[Serial_Worrier]

Although a little radiation is helpful if it encourages genetic mutation which promotes evolution.

So there could be life closer to the galactic center but not anywhere near the exact center itself.

Ii very much doubt that any intelligent life is near the galactic center EXCEPT for advanced beings who evolved on the outer spiral arms.

[Keith_McClary]

Recently Discovered Habitable World May Not Exist

at this week's Astrophysics of Planetary Systems meeting, astronomer Francesco Pepe of the Geneva Observatory and the Swiss group reported that he and his colleagues could find no reliable sign of a fifth planet in Gliese 581's habitable zone. They used only their own observations, but they expanded their published data set from what the U.S. group included in its analysis to a length of 6.5 years and 180 measurements. "We do not see any evidence for a fifth planet ... as announced by Vogt et al.," Pepe wrote Science in an e-mail from the meeting. On the other hand, "we can't prove there is no fifth planet." No one yet has the required precision in their observations to prove the absence of such a small exoplanet, he notes.

[Tyler_JC]

Way to be a wet blanket. Jeez...

[Sixstrings]

Way to be a wet blanket. Jeez...

Tell me about it. First a gazillion posts about how we'll never get there, now it may not be there in the first place. You guys are no fun.

[Keith_McClary]

We've still got 20 years:
Time to find a second Earth, WWF says

Carbon pollution and over-use of Earth's natural resources have become so critical that, on current trends, we will need a second planet to meet our needs by 2030