Is there life in the universe, and if so has it visited Earth?

[The Dagda]

Yes, but it is possible to look at what conditions might prevent it.
1] How the heck stable was the Earth a mere 150my after formation? It was mostly magma.
2] How the heck did life get so advanced as to leave fossils in a mere 150my?
3] How the heck did life get such an impressive foothold in a mere 150my? Widespread enough for us to find these fossils. (As a comparison, there are only about 5 complete T.Rex skeletons in the world. This is an indication of how rare preserved fossils really are.)

Nobody's arguing it's impossible, it is just getting implausible. So, an alternate possibility is put forth: perhaps it had all the time it needed - somewhere else.

The age of the Earth is ~4.54 Billion years, that puts the time for formation between 4.2 billion and 3.7 billion years ago. I also believe the fossil record goes back to ~3.5 Billion years ago. As for when life was able to develop, I think the above estimates are accurate enough. I don't know how that quote can be that accurate anyway, seems a bit of a stretch on some pretty big assumptions.

And really, what's so ridiculous about that? It started somewhere, why must it have been here?

It's not ridiculous it's just one of many ideas.

 

[BoomBoom]

Yes, but it is possible to look at what conditions might prevent it.
1] How the heck stable was the Earth a mere 150my after formation? It was mostly magma.
2] How the heck did life get so advanced as to leave fossils in a mere 150my?
3] How the heck did life get such an impressive foothold in a mere 150my? Widespread enough for us to find these fossils. (As a comparison, there are only about 5 complete T.Rex skeletons in the world. This is an indication of how rare preserved fossils really are.)

Nobody's arguing it's impossible, it is just getting implausible. So, an alternate possibility is put forth: perhaps it had all the time it needed - somewhere else.

And really, what's so ridiculous about that? It started somewhere, why must it have been here?

While 150 million years sounds like the blink of an eye in astronomical terms, it really is quite a long time. Homonids evolved and spread throughout the world in just a few million. Besides, as mentioned by others, our estimates could leave a lot of "wiggle" room as the age of the Earth is an estimate that probably has a fairly large margin of error.

The postulation that life came from space can never be verified or proven, nor does it do anything to describe the process of abiogenisis. You are still left with the question of how life started.

 

[CEL]

Yes, but it is possible to look at what conditions might prevent it.
1] How the heck stable was the Earth a mere 150my after formation? It was mostly magma.
2] How the heck did life get so advanced as to leave fossils in a mere 150my?
3] How the heck did life get such an impressive foothold in a mere 150my? Widespread enough for us to find these fossils. (As a comparison, there are only about 5 complete T.Rex skeletons in the world. This is an indication of how rare preserved fossils really are.)

Nobody's arguing it's impossible, it is just getting implausible. So, an alternate possibility is put forth: perhaps it had all the time it needed - somewhere else.

And really, what's so ridiculous about that? It started somewhere, why must it have been here?

Dagda has already corrected the time. About the planet being mostly magma, this is an idea that was abandoned a long time ago. The accepted theory of planetary formation is no longer that of a ball of magma that cools down and solidifies. Planets are formed by accretion. Small bodies are attracted by gravity forming larger ones. When the body is large enough, the pressure melts the interior.

 

[JorgeLobo]

no dave - "implausible" is subjective and presumes some level of knowledge, It's as unsupportable as your claim of a remote "start" or boom boom's rejection.

 

[WhoWee]

Ahhhh...don't you love it when nobody really knows for certain...lot's of theories to put things into perspective...distances/speed of light, probability of life supporting planets, time requirements of evolution, dangers of technological advancements, etc.

Accordingly, I've always wanted to write a book with a title of something like: "I Believe...Yet Darwin Was Right?...some people absolutely evolved from apes and some from aliens" (by the way God by definition is an alien - not FROM this planet)...LOL.

...just saying.

 

[The Dagda]

Ahhhh...don't you love it when nobody really knows for certain...lot's of theories to put things into perspective...distances/speed of light, probability of life supporting planets, time requirements of evolution, dangers of technological advancements, etc.

Accordingly, I've always wanted to write a book with a title of something like: "I Believe...Yet Darwin Was Right?...some people absolutely evolved from apes and some from aliens" (by the way God by definition is an alien - not FROM this planet)...LOL.

...just saying.

Let's face it the question is so open that it involves all sorts of ideas, from the sublime to the ridiculous.

 

[harvellt]

I hope The James Webb Space Telescope finds Dyson spheres! :P

 

[phyzmatix]

Let's face it the question is so open that it involves all sorts of ideas, from the sublime to the ridiculous.

That is so true...And what I find interestingly ridiculous about this is that nobody will ever really know with absolute certainty and yet people will fervently defend their theories and hypotheses as if their particular opinions were fact...

 

[DaveC426913]

It's not ridiculous it's just one of many ideas.

Yes, that's my point. I was refuting BoomBoom's claim that we are reaching for a solution that is (granted facetiously) as "absurd" as "dark DNA".

 

[The Dagda]

That is so true...And what I find interestingly ridiculous about this is that nobody will ever really know with absolute certainty and yet people will fervently defend their theories and hypotheses as if their particular opinions were fact...

Never say never, if one day we manage to voyage to the stars, we may find that life develops according to a fairly predictable plan, science isn't about truth though, but enough circumstantial evidence will make virtually anything fairly certain. Let's not forget we may spark abiogenesis in the lab as well.

 

[phyzmatix]

Never say never, if one day we manage to voyage to the stars, we may find that life develops according to a fairly predictable plan, science isn't about truth though, but enough circumstantial evidence will make virtually anything fairly certain. Let's not forget we may spark abiogenesis in the lab as well.

True, but until that time, there is nothing but theory. I find this interesting though: Miller-Urey experiment

 

[CEL]

True, but until that time, there is nothing but theory. I find this interesting though: Miller-Urey experiment

We don't really need to go to the stars. Probes to the planets and satellites of our solar system may discover signs of life. If we find life similar to that on Earth, the panspermia hypothesis will be reinforced.

 

[baywax]

We don't really need to go to the stars. Probes to the planets and satellites of our solar system may discover signs of life. If we find life similar to that on Earth, the panspermia hypothesis will be reinforced.

There is the disputed fossil evidence of life from Mars in Meteorite ALH84001


http://nssdc.gsfc.nasa.gov/planetary/marslife.html

Looking at the numbers... over 9 billion years of opportunities for water based life to develop in the universe is astounding. I'd say that over that time it has become a "knee-jerk" development which the elements simply evolve into by way of the laws of thermodynamics, fluid dynamics and other sets of laws I am not qualified to talk about!

 

[The Dagda]

True, but until that time, there is nothing but theory. I find this interesting though: Miller-Urey experiment

Nothing but theory and hypothesis, let's keep theory in the science camp and hypothesis in the other camp, there's too much of that mixing the twain for my liking these days. Both are vital to science, but one is philosophy the other is science and philosophy.

We don't really need to go to the stars. Probes to the planets and satellites of our solar system may discover signs of life. If we find life similar to that on Earth, the panspermia hypothesis will be reinforced.

Very true.

 

[JorgeLobo]

The so-called fossil evidence from Mars is not disputed - it isn't even generally accepted as such. IF we find life ("signs" are subjective) AND we haven't found life so far.

 

[BoomBoom]

If we find life similar to that on Earth, the panspermia hypothesis will be reinforced.

Unless, of course, we find that the basic structure of life is universal.

However, any similar life we were to find in our solar system would have some claiming panspermia. So I guess we will have to find life outside our solar system that is similar to life on Earth to put that claim at rest? Or maybe that wouldn't do it either...maybe we need to find similar life outside our galaxy?

I guess since that theory (panspermia as the origin of life on earth) can never be proven or disproven, it will always be around...but it will never be anything more than pure speculation.

 

[The Dagda]

Unless, of course, we find that the basic structure of life is universal.

However, any similar life we were to find in our solar system would have some claiming panspermia. So I guess we will have to find life outside our solar system that is similar to life on Earth to put that claim at rest? Or maybe that wouldn't do it either...maybe we need to find similar life outside our galaxy?

I guess since that theory (panspermia as the origin of life on earth) can never be proven or disproven, it will always be around...but it will never be anything more than pure speculation.

If we find a load of humanoid races that are practically identical to us that might seal it, or The Greys tell us the truth or whatever. But let's face it we are unlikely to know possibly ever, but not never.

 

[baywax]

I guess since that theory (panspermia as the origin of life on earth) can never be proven or disproven, it will always be around...but it will never be anything more than pure speculation.

There must be a way to trace the origin of life with regard to abiogenesis vs panspermia. I think we've covered some methods using the configuration of a specimen's DNA or the single strand configuration of RNA and how it relates to the type of sunlight or mineral content in which it has evolved. Meteorites sporting apparent fossils tend to speak volumes about the relative ease life seems to have sprouting up in other regions of space.

 

[DaveC426913]

I guess since that theory (panspermia as the origin of life on earth) can never be proven or disproven, it will always be around...but it will never be anything more than pure speculation.

Of course it could be dis/proven (or at least satisafactorily resolved). It might take a fabulously advanced technology and knowledge base but, in principle, it's not much different from showing at Ebola arose out of an epicentre in Africa.

 

[Ivan Seeking]

Yes, there is no reason to think this can never be resolved. What's more, we could find a meteor containing alien bacteria, tomorrow.

 

[baywax]

Yes, there is no reason to think this can never be resolved. What's more, we could find a meteor containing alien bacteria, tomorrow.

Could it be determined if the meteor originated from an Earth impact or not?

 

[Ivan Seeking]

Could it be determined if the meteor originated from an Earth impact or not?

There may be situations where we couldn't be sure, but there are certainly indicators that would show it did not have terrestrial origins. For example, the meteor could be older than the earth. Or, we could find isotopic ratios not found on earth. Not my field but those are a couple of possiblities.

 

[CEL]

Unless, of course, we find that the basic structure of life is universal.

However, any similar life we were to find in our solar system would have some claiming panspermia. So I guess we will have to find life outside our solar system that is similar to life on Earth to put that claim at rest? Or maybe that wouldn't do it either...maybe we need to find similar life outside our galaxy?

I guess since that theory (panspermia as the origin of life on earth) can never be proven or disproven, it will always be around...but it will never be anything more than pure speculation.

There is no proof in empirical sciences. Observations are made, hypotheses derive from the observations and a theory is formulated. If subsequent observations confirm the theory, it is accepted. If in the future new observations don't fit the theory, it is reformulated or abandoned, but proof exists only in axiomatic sciences like Math or Logic.

 

[DaveC426913]

There is no proof in empirical sciences. Observations are made, hypotheses derive from the observations and a theory is formulated. If subsequent observations confirm the theory, it is accepted. If in the future new observations don't fit the theory, it is reformulated or abandoned, but proof exists only in axiomatic sciences like Math or Logic.

Well...

If we found a rock that had a markedly different composition from Earth, say it matched the composition of the Moon rocks to several decimals across a dozen elements, we can be pretty confident that rock is a meteorite.

You could bifurcate bunnies and claim "that's not proof" but frankly, if there's only one contender for theories and any other contender would require us throwing out centuries of well-established knowledge (such as: maybe it's a rock from a quarry that has an astonishingly coincidental elemental makeup to that of the Moon that heretofore has never been seen on Earth, and because, well, it's never been exposed to oxygen ... or water) then it's pretty much proven in my books.

 

[CEL]

Well...

If we found a rock that had a markedly different composition from Earth, say it matched the composition of the Moon rocks to several decimals across a dozen elements, we can be pretty confident that rock is a meteorite.

You could bifurcate bunnies and claim "that's not proof" but frankly, if there's only one contender for theories and any other contender would require us throwing out centuries of well-established knowledge (such as: maybe it's a rock from a quarry that has an astonishingly coincidental elemental makeup to that of the Moon that heretofore has never been seen on Earth, and because, well, it's never been exposed to oxygen ... or water) then it's pretty much proven in my books.

The only cases where you have only one contender to a theory is when this contender is the null hypothesis. In your example of a found rock: it is a meteorite or not. You can prove the null hypothesis if the rock was found in a quarry on Earth, where all he rocks have the same composition.
The hypothesis that it is really a meteorite cannot b proved, but we can accept it as very likely, in the case of an extraordinary match of its composition with that of a known extraterrestrial body. But very likely does not mean sure.

 

[The Dagda]

There is no proof in empirical sciences. Observations are made, hypotheses derive from the observations and a theory is formulated. If subsequent observations confirm the theory, it is accepted. If in the future new observations don't fit the theory, it is reformulated or abandoned, but proof exists only in axiomatic sciences like Math or Logic.

Just to be needlessly pedantic: math and logic are not really sciences unless they are applied to something real world. For example the death penalty why it is wrong, would be a sociological concern logical or not. And the aerodynamics of shuttle re-entry would be science, but n-dimensional topography may well be not, and neither is the ontological argument.

 

[baywax]

Well...

If we found a rock that had a markedly different composition from Earth, say it matched the composition of the Moon rocks to several decimals across a dozen elements, we can be pretty confident that rock is a meteorite.

You could bifurcate bunnies and claim "that's not proof" but frankly, if there's only one contender for theories and any other contender would require us throwing out centuries of well-established knowledge (such as: maybe it's a rock from a quarry that has an astonishingly coincidental elemental makeup to that of the Moon that heretofore has never been seen on Earth, and because, well, it's never been exposed to oxygen ... or water) then it's pretty much proven in my books.

Apparently its not that hard to tell the difference between terrestrial originating and extraterrestrial originating meteorites... from the Astrophysics Section..."When did H2O develop during the last 13.5 b y?"

On 28 September 1969, near the town of Murchison, Victoria in Australia, a bright fireball was observed to separate into three fragments before disappearing. A cloud of smoke and, 30 seconds later, a tremor was observed. Many specimens were found over an area larger than 13 km², with individual masses up to 7 kg; one, weighing 680 g, broke through a roof and fell in hay. The total collected mass exceeds 100 kg.

The meteorite belongs to the CM group of carbonaceous chondrites. Murchison is petrologic type 2, which means that it experienced extensive alteration by water-rich fluids on its parent body. before falling to Earth. CM chondrites, together with the CI group, are rich in carbon and are among the most chemically primitive meteorites in our collections. Like other CM chondrites, Murchison contains abundant CAIs. Over 100 amino acids (the basic components of biological life) have been identified in the meteorite. A 2008 study showed that the Murchison meteorite contains nucleobases. Measured carbon isotope ratios indicate a non-terrestrial origin for these compounds.

Measured purine and pyrimidine compounds are indigenous components of the Murchison meteorite. Carbon isotope ratios for uracil and xanthine of 44.5% and +37.7%, respectively, indicate a non-terrestrial origin for these compounds. These new results demonstrate that organic compounds, which are components of the genetic code, were already present in the early solar system and may have played a key role in life's origin.

More recent dating sets its age at nearly 4.95 billion years; nearly 500 million years older than the age of the Earth.

The Murchison meteorite contains 12% water.

http://en.wikipedia.org/wiki/Murchison_meteorite

 

[DaveC426913]

Apparently its not that hard to tell the difference between terrestrial originating and extraterrestrial originating meteorites.

Yep. I was impressed when I first read about the uniqueness of the composition of extraterrestrial rocks.

 

[CEL]

This is interesting:
http://edition.cnn.com/2009/TECH/space/02/25/galaxy.planets.kepler/index.html

 

[Karl G.]

In Richard Dawkin's "The God Delusion", he argues that even if the probability of life occurring is extermely small (sorry, can't remember exact figures!), there still is a good probability that life exists somewhere else in the universe. Assume, for example, that there are 1,000 civilizations dispersed evenly throughout the universe. The distances between us and them would be so huge that (keeping relativity in mind and ignoring the slim possibility that large organisms can travel through worm-holes) communication and travel between any two civilizations would remain highly improbable, even if several of the civilizations where highly advanced compared to Earth. So the fact that foreign organisms have never visited Earth (I tend to believe all accounts of UFO's are spurious) doesn't mean they don't exist.