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

[Ivan Seeking]

I think you mean that all accounts of alien spacecraft s are spurious. People see UFOs every day.

 

[NWH]

I have three feelings on this matter. The first is my realistic opinion, what I think's realistically possible. The second is my back-up feeling, what I'd feel should the first be proved wrong. And the third is basically my fantasy...

1. Inteligent beings have not visited us, however the chances of them visiting us are greater than us visiting them. I don't believe there's any inteligent life near enough to us that we'd be able to view or observe from Earth or our solar system, other than micro-organisms. I think the amount of time involved in getting technology to a point of exploring anywhere outside of our own solar system, would take so long, it would probably never happen. If technology was ever possible to reach that kind of stage, I think it would be known to us by other beings from deeper in the universe who've had more time to develop and master the technology of intergalactic space travel. When concidering the fact that some galaxies are older than others, I'd imagine if inteligent life is around there, they'd probably do it before us. Once light drive is invented (if it ever is), that boundary is elimineted and the stars are open for exploration, which is why I believe whoever invents it first will be the one to make the visit and it won't be us.

2. Earth was inseminated by organisms hitching a ride on a commet which crash landed in the sea, bringing inteligent life into Earth's existence. I really like this idea, because in this instance, we'd be the visitors our selves.

3. Life in our solar system origionated from Mars. Sadly, they had to abandon their world because of being bombarded with asteroids from the near by exploding planet which created the asteroid field. With that, they fled to Earth and watched their planet continue to die, creating the Pyramids across the world as they colonised their new planet.

 

[CEL]

...
3. Life in our solar system origionated from Mars. Sadly, they had to abandon their world because of being bombarded with asteroids from the near by exploding planet which created the asteroid field. With that, they fled to Earth and watched their planet continue to die, creating the Pyramids across the world as they colonised their new planet.

Contrarily to popular belief, the asteroid belt is not the residue of an exploding planet, but the remains of matter insufficient to form a planet.
As for Mars, its gravity is insufficient to retain enough atmosphere, necessary to sustain intelligent life.

 

[Ivan Seeking]

As for Mars, its gravity is insufficient to retain enough atmosphere, necessary to sustain intelligent life.

Then why do we find NASA scientists who want to terraform Mars?

Perhaps you meant that the atmosphere wouldn't be sustainable long for intelligent life to evolve?

 

[harvellt]

Not that I agree life on Earth came from mars. I have seen some pretty credible people say that Mars could have sustained an atmosphere befor its iron core cooled and stopped spinning. Its not gravity alone that let's us keep our atmosphere but also the magnetosphere that prevents it from beeing torn off by the solor winds.

 

[Ivan Seeking]

Its not gravity alone that let's us keep our atmosphere but also the magnetosphere that prevents it from beeing torn off by the solor winds.

True. There was a discussion about this some time ago. IIRC, Mars could have had an atmosphere for a couple of billion years. But even if I am remembering this correctly, it may be a subject of debate.

 

[NWH]

Contrarily to popular belief, the asteroid belt is not the residue of an exploding planet, but the remains of matter insufficient to form a planet.
As for Mars, its gravity is insufficient to retain enough atmosphere, necessary to sustain intelligent life.

Yeah, that's why I said it's more of a fantasy than my actual realistic opinion. I just like the idea that our solar system was vastly different to how we imagine and that inteligent life might have existed before us. But yeah, the first point I made was pretty much how I see things.

 

[baywax]

Then why do we find NASA scientists who want to terraform Mars?

Perhaps you meant that the atmosphere wouldn't be sustainable long for intelligent life to evolve?

Did Mars lose atmosphere, oceans and gravity (including the detriment of its core) after being hit so badly that it lost half its crust and was practically run through by an impact?

 

[harvellt]

From what I understand, can't have less gravity unless you have less mass. Also Mars is smaller than Earth so the core cooled faster and solidified.

 

[DaveC426913]

From what I understand, can't have less gravity unless you have less mass.

Depends. You can have less surface gravity if the body is larger.

Gliese 581c is five times more massive than Earth but its surface gravity is only a little more than 2x Earth's because Gliese's radius is 1.5x Earth's.

i.e. for a given mass, surface gravity can vary depending on the density (and thus radius) of the body.

That may or may not factor into Mars, I'm merely pointing out that mass(p) =/= gravity(p).

 

[harvellt]

Ahh yea makes perfect sense but you would need to change the density of the sphear of a planet and I am not sure how this could have happened on mars.

 

[Ivan Seeking]

At the least, it takes on the order of a billion years for the atmosphere to be blown away by the solar winds. It isn't like the atmosphere just floats away.

 

[baywax]

How Mars Lost its Atmosphere
15 April 1989

ASTEROIDS and comets have blasted away most of Mars's original atmosphere, according to new calculations made at the University of Arizona, in Tucson. The new results contradict earlier ideas that comets may have built up the water and atmosphere on planets in their early days.

Jay Melosh and Ann Vickery have looked at what happens to a planet's atmosphere when a comet or asteroid strikes the surface. Other researchers found that solid fragments from the explosion could push a negligible amount of the gases into space. Melosh and Vickery have now discovered a much more important effect (Nature, vol 338, p 487).

When an object hits the planet, it explodes into a plume of hot gases that can expand faster than the planet's escape velocity. This gas sweeps up the surrounding gas in the atmosphere, and lifts it into space.

The process is most efficient when the planet has a low gravity, so an object that hits Mars, which is a small planet, would need to be only 3 kilometres across, to sweep the gas up, while for the Earth we would need something 13 kilometres in diameter to produce the same effect.

Melosh and Vickery suggest that Mars originally had an atmosphere with a pressure similar to that of Earth. At present the atmospheric pressure of Mars is only 1/150th that of the Earth.

http://www.newscientist.com/article/mg12216603.400-science-how-mars-lost-its-atmosphere-.html



And about Mars' crust/core...

The interior of Mars appears to contain a dense core of about 3,400 km (2,200 miles) in diameter, a molten rocky mantle somewhat denser than the Earth's, and a thin crust. The crust is about 80 km (50 miles) thick in the southern hemisphere but only about 35 km (22 miles) thick in the north. Mars' relatively low density compared to the other terrestrial planets indicates that its core probably contains a relatively large fraction of sulfur in addition to iron (i.e., as iron sulfide).

Although scientists now believe that the planet's core still has liquid molten iron in an outer layer, they are uncertain whether the inner core solidified like Earth's (more). Mars appears to lack active plate tectonics and volcanic activity at present like Mercury and Earth's Moon. Large but weak, and not global, magnetic fields exist in various regions of Mars which are probably remnants of an earlier global field that has since disappeared.

http://www.solstation.com/stars/mars.htm

I'd suspect that the loss of half of the northern hemispheric crust of Mars due to a more recent super-sized impact event would reduce an already weaker gravitational environment. You can see in these statistics that Mars' crust in the southern hemisphere is about 50 miles thick and in the north appears to be more than 50% less in thickness. Please feel free to calculate how much mass was lost during the impact event.

 

[phyzmatix]

As for Mars, its gravity is insufficient to retain enough atmosphere, necessary to sustain intelligent life.

...as we know it...

 

[Ivan Seeking]

The building blocks of life may be more than merely common in the cosmos. Humans and aliens could share a common genetic foundation.

That's the tantalizing implication of a pattern found in the formation of amino acids in meteorites, deep-sea hydrothermal vents, and simulations of primordial Earth. The pattern appears to follow basic thermodynamic laws, applicable throughout the known universe.

"This may implicate a universal structure of the first genetic codes anywhere," said astrophysicist Ralph Pudritz of McMaster University in Hamilton, Ontario...

http://blog.wired.com/wiredscience/2009/04/thermodynamino.html

Preprint
A thermodynamic basis for prebiotic amino acid synthesis and the nature of the first genetic code
http://arxiv.org/abs/0904.0402

 

[GODISMYSHADOW]

You mustn't ask a question like, "Is there life beyond our planet?"
Here's a better question: "Is there life beyond our planet within
500 light-years?" Put some limits on it.

 

[Blenton]

You mustn't ask a question like, "Is there life beyond our planet?"
Here's a better question: "Is there life beyond our planet within
500 light-years?" Put some limits on it.

What difference does it make? Honestly if they haven't found faster than light travel then that pretty much limits them effectively reaching us in this solar system only. If they do have FTL travel then who is to say that they can't travel 1 light year as easily as 500.

 

[GODISMYSHADOW]

What difference does it make? Honestly if they haven't found faster than light travel then that pretty much limits them effectively reaching us in this solar system only. If they do have FTL travel then who is to say that they can't travel 1 light year as easily as 500.

For a measured region of space, like within 500 light-years of Earth, there could be a definite
yes or no answer. For unlimited space you can't say there's not, so why even ask?

 

[ibcnunabit]

The answer in the poll that I would have preferred would be "possibly, but I doubt it."
I'd almost say no, but there's always that chance that it's happened and we never knew, so I felt compelled to say "maybe/maybe not."

 

[Vectus]

Wow, just got done reading this thread.


I saw a couple times mentioned the possible reasons why we have not yet encountered a technological civilization yet, given that the evidence we have and what we know suggests that such should be commonplace in the universe and a sufficiently advanced civilization could colonize the galaxy on the order of less than a million years.

I believe the reasons cited were 1) That such civilizations do not exist [or may not exist simultaneously](i.e. - intelligent life capable of producing said civilizations are either extremely rare or inherently self destructive), 2) That interstellar travel or communication is not feasible for any civilization due to the massive scale of time and space, and (as pointed out by Dave) 3) They may be there but intentionally avoid contact with us.

I just wanted to add a 4th since I haven't seen the idea discussed any:

They may not want or need to colonize other planets.

 

[Vectus]

As for my thoughts on the matter--

What we know and the limited evidence we have suggests heavily that the universe could be teeming with life at every possible location. As suggested in an article linked earlier by Ivan, there is even the possibility that life so alien as to be fundamentally based on a different structure than ours may exist in droves in intergalactic dust clouds!

Just as we look on our own planet, life gives testament to its resilience. Aside from the very fact that it is still here after nearly four billion years and persisted through 5 or 6 major mass-extinction events, it not only exists, but thrives in the harshest of environments. We even have life that can survive unaided in space!

Given that even a tiny fraction of life may develop civilizations, it is indeed a real wonder why we have not encountered said intelligent life, when the prospects are so high of it being out there. I find this tantalizing to say the very least.


I think the most compelling argument to solve this issue is that we have not been looking long enough or even in the right ways. That to me is the most likely.

 

[DaveC426913]

Just as we look on our own planet, life gives testament to its resilience. Aside from the very fact that it is still here after nearly four billion years and persisted through 5 or 6 major mass-extinction events, it not only exists, but thrives in the harshest of environments. We even have life that can survive unaided in space!

Yes, but the question of how existing life survives has nothing to do with how non-life becomes life in the first place.

I find the most compelling argument to solve this debacle ...

I do not zink zat word means what you zink it means...
-Inigo Montoyez

 

[Vectus]

Yes, but the question of how existing life survives has nothing to do with how non-life becomes life in the first place.

My point is this: once life takes a foothold, next to nothing can get rid of it short of the planet being nearly destroyed or it's star going supernova.

Given the timescales involved, and even if the chance for life to arise turns out to be minutely small, we would still expect to see that it has cropped up all over the place.

I do not zink zat word means what you zink it means...
-Inigo Montoyez

It was like 4 am when I typed that. I must have been thinking of another word, which escapes me now. >.>

 

[DaveC426913]

My point is this: once life takes a foothold, next to nothing can get rid of it short of the planet being nearly destroyed or it's star going supernova.

I'll grant this, but:

Given the timescales involved, and even if the chance for life to arise turns out to be minutely small, we would still expect to see that it has cropped up all over the place.

I see where you're going but there's a logical disconnect.

If the chances of life arising are 1 in 200 billion over 13 billion years, then chances are it will have cropped up only twice in our galaxy. I grant that it might last virtually forever, which means, no matter how long ago they cropped up, they're likely still around. But there's still only 2 of them.

The fact that life appears to be tenacious has absolutely no bearing on how often it has arisen.

 

[Vectus]

The fact that life appears to be tenacious has absolutely no bearing on how often it has arisen.

Given. But let us not assume that there is only one chance for a life-capable planet to actually give rise to life. Over time, conditions may become more favorable to abiogenesis, the planet may be seeded via panspermia, or life may arise by other mechanisms that we do not know of or fully understand at present (terraforming, perhaps?).

That is all I meant. I find it wildly unlikely that we're the only ones out here given the amount of time we're looking at and the fact that nothing suggests our little mote of dust is special in any way.

Saying we're alone because of the results of our past and current search for life can be reckoned to shining a flashlight into a dark room for a couple seconds and declaring it empty. And I think that's actually giving it several orders of magnitude too much credit.

 

[DaveC426913]

Saying we're alone because of the results of our past and current search for life can be reckoned to shining a flashlight into a dark room for a couple seconds and declaring it empty.

No, it's equivalent to saying "We don't know if there's a mosquito in it."

 

[Vectus]

No, it's equivalent to saying "We don't know if there's a mosquito in it."

Well of course. We don't know until we know, right? :D

I wasn't trying to make an analogy to the rational stance of agnosticism towards the matter, but to the irrational stance that because of our inability to find life that it must be rare, despite everything else pointing to the contrary.

 

[imiyakawa]

I know for a fact, because I've witnessed what could be called a "UFO" (wasn't very unidentified though).

 

[Ivan Seeking]

I know for a fact, because I've witnessed what could be called a "UFO" (wasn't very unidentified though).

Would you like to share your story?

 

[junglebeast]

I know for a fact, because I've witnessed what could be called a "UFO" (wasn't very unidentified though).

The only thing that can be called a UFO is an unidentified flying object.