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GrandMasterK

Was there enough time for a planet like earth to exist long before earth?

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I ask this with the evolution of the universe in mind. The universe was born 14 billion years ago, the earth 4.5 billion years ago, and life on earth...I don't know 1.5-2 billion years ago? How much earlier than 4.5 billion years ago could a planet like earth of been created. How about intelligent life. Could people smarter than us of lived 2 billion years ago, which means life on their planet probably started 2-3 billion years before that (if their evolution is anything like ours) or was the universe just not fit to do such a thing yet?

 

About stars also. Stars have been observed "burning out" right? Our star's lifespan will be longer than 14 billion years....right? Why did those stars burn out so fast?

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How much earlier than 4.5 billion years ago could a planet like earth of been created.
Probably quite earlier, Earth is distinctly undistinctive, it wasn't one of the first ever planets or anything like that.
How about intelligent life. Could people smarter than us of lived 2 billion years ago
I don't see any reason why not.
if their evolution is anything like ours
Highly improbable.
Why did those stars burn out so fast?
14 billion years is fast for you?

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I'm inclined to think that the universe is big enough that everything happens somewhere as soon as it's possible to do so. There were almost certainly planets around earlier stars, and I don't see why some of them couldn't have life, and, once life, intelligent life in a much shorter timespan than it took our planet. Intelligent life has got to be very uncommon among life, but I don't see why it would necessarily take 2 billion years. Certainly there was life as complex as ourselves in far, far less than that after the Cambrian explosion on Earth, and a similar explosion could happen at any time on some other planet as long as the conditions are right.

 

Our star's lifespan will likely be about 10 billion years, which is actually quite long for a star, in general. We've got enough fuel to last a long time, but not to burn too fast. And, unlike most stars, we're in a relatively sparse area, where stars don't heat each other up too much. And I'll echo the tree. That seems fast to you?

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I guess a better question would be when was the universe fit to make life. Obviously not 5 seconds after it's birth, or even a million years after it's birth. I'm not sure how long the universe was in chaos. I read that when the earth was in it's early molten stage it kept being nailed and bashed by all kinds of shit until it ceased and the planet started cooling down.

 

Also, are planets the way they are because of their distance and exposure to their star or is it possible for a planet like earth to maintain the same kind of environment and be 10 times further away from our sun than we are now?

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Our star is classified as a third generation star.

The first generation contained little more than hydrogen, and some helium impurity.

Second generation included larger atoms.

Third generation included the full range of atoms currently present.

 

It is very likely that only a solar system with a third generation star could produce life, since earlier models would not have had the right mix of more complex atoms. However, third generation stars have been around for at least 6 to 8 billion years. The Milky Way galaxy has stars (third generation) which are two billion years older than our own. In fact 10% of the galaxy is made up of such stars.

 

Thus life could easily have developed two billion years before Earth life developed. Of course, this is speculation, since we still do not know the specific set of conditions required for biogenesis. The one thing we do know for sure, is that no trace of alien life or alien civilisation has been seen on Earth. Not even a fossil coke bottle!

 

Since it is possible in theory to travel between the stars at one tenth of light speed, crossing the galaxy in a million years, and an advanced civilisation could probably do this, and since the power to reproduce and increase population numbers is unlimited, if evolution had led to a number of intelligent life forms developing two billion years before we did, it is almost certain that they would have visited, and maybe colonised the Earth. Since there is no sign of any such visit, that reduces the probability that intelligent life in our galaxy preceded human life by terribly much, if at all.

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and life on earth...I don't know 1.5-2 billion years ago?

As far as I know life on earth started around 3.5 to 4 billion years ago. It seems that, no sooner than life could develop, it did.

 

I think that SkepticLance has nailed it. Life on Earth is dependant on some of the heavier elements (like carbon) and what was produced in the earlier generations of stars. But the Sun and our solar system is not the first of these 3rd genration of stars to form.

 

Scince there are some 3rd generation stars that have formed around 2 billion years before the sun then it is posible that life developed on there too. But the big question is: If they have had 2 billion years development ahead of us, then where are they?

 

Here on earth the average time for a species to survive is around 1 million years (ther are exceptions and a big spread of survival times). Usually because the environemnt changes too much (and therefor the species needs to adapt to the changes and a new species is seen in the fossil records), a natural catastrophy (just ask the dinosaurs :D ) or some other event, a species will either evolve into a different one or become extinct.

 

If we assume (and this is a big assumption) that this same average survival time occures on other planets with life, then 2 billion years is a long time for a species to survive. In the 4 or so billion years that life on Earth has existed, only in the last million years (approx) has inteligent life existed that we know of. In a million years most traces of humanity will be destroyed, very little will survive.

 

So the infrequency of inteligent life, the fleetingness of species and the decay over time of any fossil eveidence (coke bottles or otherwise), means that if any alien species did visit us in the past, it is unlikely that we would find any trace of them.

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Since there is no sign of any such visit, that reduces the probability that intelligent life in our galaxy preceded human life by terribly much, if at all.

 

Unless most intelligent species kill themselves off. Or are, for some reason, inherently incapable of space travel. Or they never saw any reason to bother with our planet. Those are three good reasons they might not have visited, and if intelligent life is exceptionally rare, that might explain it nicely.

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Sisyphus said :

 

and if intelligent life is exceptionally rare, that might explain it nicely.

 

I absolutely agree. I have a problem with those who claim (Star Trek et al) that intelligent life is common. If so, where are the traces?

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Sisyphus said :

 

and if intelligent life is exceptionally rare' date=' that might explain it nicely.[/i']

 

I absolutely agree. I have a problem with those who claim (Star Trek et al) that intelligent life is common. If so, where are the traces?

 

 

How would you detect them, without assuming they had somehow discovered workarounds for the physical laws with which we are familiar (e.g. limitations imposed by relativity)?

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Swansont,

NASA scientists estimate that humans will have begun our journey to visit and colonise other star systems within 1000 years. While some other intelligent species might be 'stay at homes' or else kill themselves off early, if there are large numbers of intelligent species, then it appears probable that at least some would set out to explore the galaxy.

 

At an estimated speed of 0.1c (we assume Einstein was right), and reasonable estimates for speed of population growth etc., we can assume they will fully explore and colonise the entire galaxy withing 2 to 10 million years (depending on which assumptions you use). Do the math yourself.

 

Since 10% of the stars in the Milky Way are about 2 billion years older than our one, then (based on the assumption that lots of intelligences evolve) it is reasonable to deduce that at least one intelligence colonised the galaxy 1 to 2 billion years ago. Thus, the signs I am talking about would be right here on Earth. Hell, humankind produce enough durable garbage. An alien species would be seriously likely to do the same. The result would be a plethora of fossils.

 

Since there are no such signs, it is reasonable to assume that alien intelligences are rare.

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Swansont' date='

NASA scientists estimate that humans will have begun our journey to visit and colonise other star systems within 1000 years. While some other intelligent species might be 'stay at homes' or else kill themselves off early, if there are large numbers of intelligent species, then it appears probable that at least some would set out to explore the galaxy.

 

At an estimated speed of 0.1c (we assume Einstein was right), and reasonable estimates for speed of population growth etc., we can assume they will fully explore and colonise the entire galaxy withing 2 to 10 million years (depending on which assumptions you use). Do the math yourself.

[/quote']

 

Since I don't know what assumptions you have used, I can't do the math myself. Fully explore in 2 million years? At 0.1c, it takes more than 2 million years to cross the galaxy and back, with no time for stopping off to see the galaxy's largest ball of twine.

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Since it is possible in theory to travel between the stars at one tenth of light speed' date=' crossing the galaxy in a million years, and an advanced civilisation could probably do this, and since the power to reproduce and increase population numbers is unlimited, if evolution had led to a number of intelligent life forms developing two billion years before we did, it is almost certain that they would have visited, and maybe colonised the Earth. Since there is no sign of any such visit, that reduces the probability that intelligent life in our galaxy preceded human life by terribly much, if at all.[/quote']

 

Who's to say that WE are not the result of an early alien visit. When you look around at life here on earth, there isn't another life form even close to us in terms of mental capacity (which to me seems improbable). Can we really rule out that we human beings were not created or at least "nudged" in a certain direction by an alien visitor?

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When you look around at life here on earth, there isn't another life form even close to us in terms of mental capacity (which to me seems improbable).

 

Yes, the chimpanzee. While chimpanzees lack the advanced communication and abstract thinking skills of humans, they still possess them in a rudimentary form. Certain bonobos have vocabularies of over a thousand words, use simple sentences, talk on the phone, and gossip. In short, they use language in many of the same ways humans do.

 

See this story/thread: http://www.scienceforums.net/forums/showthread.php?t=21862

 

Can we really rule out that we human beings were not created or at least "nudged" in a certain direction by an alien visitor?

 

No, we can't rule it out, however, this is a great place to use Occam's razor: what does an alien origin for humanity explain which evolution by natural selection alone does not? It's an extraneous element which doesn't provide any additional explanatory power.

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Since I don't know what assumptions you have used, I can't do the math myself. Fully explore in 2 million years? At 0.1c, it takes more than 2 million years to cross the galaxy and back, with no time for stopping off to see the galaxy's largest ball of twine.

 

swantsont, SkepticLance is essentially asking about the Fermi paradox.

 

You might want to read the "Why SETI Will Fail (and why we are alone in the Universe)" section of Kurzweil's article on the Law of Accelerating Returns:

 

http://www.kurzweilai.net/articles/art0134.html?printable=1

 

The real point is that the amount of time it would take for evidence of an alien civilization to reach earth, either via information (which can travel at c) or through physical artifacts (obviously much slower, and probably pertainent only to life in our own galaxy) is a mere fraction of the time it took for the solar system to form and for life to evolve. Therefore, if we aren't the only life systems which evolved to the point of human-level intelligence, why haven't we found evidence of other such civilizations yet?

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A very perceptive observation from bascule.

Yes, this is the Fermi Paradox.

There was a very interesting article in the February 1999 issue of Scientific American by two NASA scientists, who claimed that the theoretical 'ultimate' speed limit in interstellar travel would be 0.1 to 0.2 c. I used the lower number as my basis for calculations.

 

Swansont, at 0.1 c, it would take about 700,000 years for humans to reach the far side of our galaxy (we are two thirds towards the outer edge of a spiral 100,000 light years across.). This would be most definitely a one way trip, so we need not talk about time to return. Information, on the other hand, would take only 70,000 years to arrive.

 

When I carried out my calculations, I was surprised to see that the most limiting factor time-wise was the average speed. The human reproductive rate was not very limiting, and nor was the suggestion that we would have to spend many generations in one star system before sending out the next manned probe.

 

End result, humans (or hypothetical aliens) could cross and fully colonise the galaxy in 2 to 10 million years. The higher numbers came from the assumption (unproven but possible) that star systems towards the centre would be toxic to human life, and we would have to travel around them.

 

You will appreciate that even 10 million years is a mere eye blink in relation to biological time, since life is probably 3 to 3.8 billion years old. (Some rock structures in Western Australia have been tentatively identified as 3.6 billion year old stromatolite fossils). Thus, if lots of intelligences evolve, then plenty must have been around 2 billion years ago. If even one was expansionist, we can expect the early Earth to have been visited, and even colonised.

 

Thus, if intelligent life in our galaxy is common, we should be finding fossil artifacts.

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Who's to say that WE are not the result of an early alien visit. When you look around at life here on earth, there isn't another life form even close to us in terms of mental capacity (which to me seems improbable).

 

In addition to the 2 species of chimps, orangutuans have a large mental capacity that is easily demonstrable. E Linden, Can animals think? Time 154: 57-60, Sept 6, 1999. And, of course, we don't know exactly the capacity of dolphins and whales.

 

Can we really rule out that we human beings were not created or at least "nudged" in a certain direction by an alien visitor?

 

We can rule out the "created" as in directly manufactured in our present form. The evidence is clear that that did not happen.

 

However, there are at least 2 ways that evolution could have been nudged in the past and be undetectable by science.

 

Bascule, your use of Occam's Razor is incorrect. It is the exact opposite of what William of Occam had in mind and the position he argued against. The simplest explanation is not necessarily the correct one.

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I ask this with the evolution of the universe in mind. The universe was born 14 billion years ago' date=' the earth 4.5 billion years ago, and life on earth...I don't know 1.5-2 billion years ago? How much earlier than 4.5 billion years ago could a planet like earth of been created. How about intelligent life. Could people smarter than us of lived 2 billion years ago, which means life on their planet probably started 2-3 billion years before that (if their evolution is anything like ours) or was the universe just not fit to do such a thing yet?

 

About stars also. Stars have been observed "burning out" right? Our star's lifespan will be longer than 14 billion years....right? Why did those stars burn out so fast?[/quote']

 

From my reading, there is the problem of heavy elements and planets. At the Big Bang there was only hydrogen, helium, and some lithium. Other elements up to iron are formed by fusion in stars. Some stars then explode in novae or supernovae (depending on their size) and scatter these elements into interstellar dust and gas. Then new solar systems form from the dust and gas. When the first generation of stars formed, there was no carbon to be the basis of life. Even second generation stars apparently are unlikely to have had enough heavy elements in the dust and gas of their solar systems to get rocky planets like earth. Our sun is a 3rd generation star.

 

Now, life formed at least 3.8 billion years ago and probably earlier. It appears that life appeared as soon as the earth was not molten from the impacts of rocks whose impact formed the earth in the first place.

 

Once you have the intelligence and language ability to build a technological civilization, there really isn't a lot of selection pressure to be more intelligent than that. Of course, if any species had a several million year head start on us, their technology would be impressive, even tho their basic intelligence is probably not above ours.

 

The larger a star, the more gravitational pressure compresses the material of the star. This means that more nuclear fusion happens in the core and the star is hotter. That's why you get stars that a blue or blue-white. Our star is a medium sized star. Since "more nuclear fusion" means more fusion reactions per second, it also means that larger stars exhaust their nuclear fuel faster. So they "burn out" faster. The really big stars collapse under their own gravity, causing fusion of heavier elements than hydrogen and resulting in novae and supernovae.

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Since 10% of the stars in the Milky Way are about 2 billion years older than our one' date=' then (based on the assumption that lots of intelligences evolve) it is reasonable to deduce that at least one intelligence colonised the galaxy 1 to 2 billion years ago. Thus, the signs I am talking about would be right here on Earth. Hell, humankind produce enough durable garbage. An alien species would be seriously likely to do the same. The result would be a plethora of fossils.

 

Since there are no such signs, it is reasonable to assume that alien intelligences are rare.[/quote']

 

You have to leave out all the stars except those in a toroid at some distance from the center. That's in a new Scientific American article earlier this year. So I'm not sure your calculations of probability are correct.

 

Now, "durable garbage" is different from fossils. Durable garbage would be things like titanium turbine blades for jet aircraft, or plastics. However, I'm not sure if even this would last after a million years. Of course, gold rings or other jewelry should last.

 

You mean "reasonable to conclude", not "assume". However, that conclusion is no more reasonable than the opposite conclusion supplemented by different hypotheses: such as technological civilizations destroy themselves before they can make the massive financial investment in an interstellar ship (moving at 0.1c).

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Maybe the aliens have visited already? Maybe they regard us as too aggressive, so don't want to interact with us, but because they are so advanced (morally as well as technologically) they don't want to destroy us. Therefore they have set up an no-fly buffer around us, not letting any other intelligent life get too close.

:D

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Isnt that egotistical :D

 

It may be possible that we are the most advanced civilization in our galaxy (or at least, any other civilzations are a million or less years ahead).

 

How about inter-galactic travel?

statistically, there HAS to be intelligent life in the universe. If not in our galaxy, then perhaps in another. If they had a 1 billion yr head start then I'm sure they could make it intergalactically

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How about inter-galactic travel?

statistically' date=' there HAS to be intelligent life in the universe. If not in our galaxy, then perhaps in another. If they had a 1 billion yr head start then I'm sure they could make it intergalactically[/quote']

 

Why are you sure?

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A billion years? They MUST have thought of something to get to the next galaxy. A billion years is a lot of time... and a billion years for technology to develop is an extremely long time.

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Bascule' date=' your use of Occam's Razor is incorrect. It is the exact [b']opposite[/b] of what William of Occam had in mind and the position he argued against. The simplest explanation is not necessarily the correct one.

 

Occam's razor in its original form states simply that entities should not be multiplied unnecessarily. In other words, make as few assumptions as possible, and discard those aspects of an explanation which are not necessary to it. He also said that, given two explanations with equal predictive power, one should favor the simpler one. So how was bascule's usage incorrect?

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A billion years? They MUST have thought of something to get to the next galaxy. A billion years is a lot of time... and a billion years for technology to develop is an extremely long time.

 

But special relativity isn't a technology restriction.

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