Do you think ET life exists elsewhere?

Do you think ET life exists elsewhere in the universe?

  • Certain!

  • Probably.

  • Possible.

  • Unlikely.

  • Heck no!

  • I am not sure...:(


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  • #76
Its most likely about the circumtances that can cause to form a live. Which is tempature,water and other elements etc. And theres another thing which If you even satisfy these conditions life just doesn't pop up.
Considering Earth as the only example we have, life actually did just seem to "pop up" once conditions became favorable. Liquid water first appeared on Earth about 4.4 billion years ago. The first cells appeared about 4.3 billion years ago: a mere 100 million years after liquid water appeared. It might not have even taken that long, it's possible that new evidence will be found which will push the starting date for life even earlier.

The fact that life seems to be so readily formed, at least on Earth, suggests that the probability to form life may be rather large and that the conditions sufficient for abiogenesis may not be too particular.
 
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  • #77
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Considering Earth as the only example we have, life actually did just seem to "pop up" once conditions became favorable.
I agree. Thats also why its hard for me to believe an ET life form.There are just theories that trying to explain the formation of live on earth.
The fact that life seems to be so readily formed, at least on Earth, suggests that the probability to form life may be rather large and that the conditions sufficient for abiogenesis may not be too particular.
I like PeroK's post (#74) in this sense. In the vote section I voted unlikely, there could be life just I dont believe in that much.
 
  • #78
DaveC426913
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I agree. Thats also why its hard for me to believe an ET life form.There are just theories that trying to explain the formation of live on earth.
It should lead you to believe the opposite.

Having only one sample does not in-and-of-itself suggest ET life is rare.

In fact, in the one instance where life-as-we-know has popped up, it seems to have defied the odds of life not being common.

It seems that, almost the moment conditions became suitable, life took hold.
 
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  • #79
Dr. Courtney
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It seems that, almost the moment conditions became suitable, life took hold.
It seems your moments are a bit longer than my moments. There are various competing hypotheses regarding how chemical evolution gave rise to abiogenesis, but time scales seem to range from 1 million to 100 million years. I'm not sure how one can assign a span to the process before one of these hypotheses gathers enough evidence to be a real theory.
 
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  • #80
DaveC426913
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... time scales seem to range from 1 million to 100 million years. I'm not sure how one can assign a span to the process before one of these hypotheses gathers enough evidence to be a real theory.
Even the most pessimistic of those is fairly quick in geologic time.
The Earth's surface was molten for quite some time, and even once it had cooled, it suffered 100 million years of bombardment, and still had to wait for comets to come and deposit water.

That greatly constrains the earliest time before conditions were suitable at all. And that leaves not a lot of time left in there for a suitably conditioned earth to be lifeless before life came along.

And even that's based on the fossils that have survived for 5 billion years. It doesn't count anything that might have been around before, whose fossils have not been preserved.
 
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  • #81
russ_watters
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It seems your moments are a bit longer than my moments. There are various competing hypotheses regarding how chemical evolution gave rise to abiogenesis, but time scales seem to range from 1 million to 100 million years. I'm not sure how one can assign a span to the process before one of these hypotheses gathers enough evidence to be a real theory.
Ok, so how long are your geological "moments"? A million years after water first became liquid is about 4 billion years ago. A hundred million years after water first became liquid is also about 4 billion years ago. Why quibble about single digit percentages?; 1 vs 99 million years out of 4.4 billion is pretty fast either way. A pretty small window.
 
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  • #82
Dr. Courtney
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Ok, so how long are your geological "moments"?
Ok, so we're talking about geological moments. Please correct me if I am wrong, but I don't recall the adjective "geological" as a modifier for the use of the word "moment" that I disagreed with.
 
  • #83
DaveC426913
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Ok, so we're talking about geological moments. Please correct me if I am wrong, but I don't recall the adjective "geological" as a modifier for the use of the word "moment" that I disagreed with.
That would be implicit in the context of the thread.

Did you honestly think I meant "less than a few seconds"? :wink:
 
  • #84
Dr. Courtney
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That would be implicit in the context of the thread.

Did you honestly think I meant "less than a few seconds"? :wink:
It's not about your intent, but about the ambiguity and various ways it could be interpreted by the broad readership of Physics Forums, some of whom may not yet be familiar with the concept and magnitudes of geologic time. The concept of geologic time had not been mentioned a single time in this discussion when the statement was made, "It seems that, almost the moment conditions became suitable, life took hold."

Good science and good education practices are mindful of the full audience and are careful not to assume unstated definitions (a relative moment on the geologic time scale) rather than definitions in more common use (a normal moment in human experience.) A statement that may make perfect sense in an astrobiology journal may leave many PF readers confused.
 
  • #85
DaveC426913
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I think you're being pedantic. The time frame is implicit in the context of the discussion - the start of life on Earth, 4.5 Gy ago.
Why would you assume people will think "seconds"?
Anyway, we've wasted more time arguing it than necessary.
 
  • #86
russ_watters
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It's not about your intent, but about the ambiguity and various ways it could be interpreted by the broad readership of Physics Forums, some of whom may not yet be familiar with the concept and magnitudes of geologic time. The concept of geologic time had not been mentioned a single time in this discussion when the statement was made, "It seems that, almost the moment conditions became suitable, life took hold."

Good science and good education practices are mindful of the full audience and are careful not to assume unstated definitions (a relative moment on the geologic time scale) rather than definitions in more common use (a normal moment in human experience.) A statement that may make perfect sense in an astrobiology journal may leave many PF readers confused.
You are being pedantic, for really no good reason. The timeframe itself was given - numerically - in the discussion you responded to and you appear to have known it yourself! So it should have been clear that's what the labels were referring to. Either way: since you now seem to understand, does that change your view on the issue being discussed? You agree that in terms of the time available for life to occur, it occurred in a small fraction of that time. Right?
 
  • #87
Dr. Courtney
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You are being pedantic, for really no good reason. The timeframe itself was given - numerically - in the discussion you responded to and you appear to have known it yourself! So it should have been clear that's what the labels were referring to. Either way: since you now seem to understand, does that change your view on the issue being discussed? You agree that in terms of the time available for life to occur, it occurred in a small fraction of that time. Right?
100 million years is about 1/45 of the geologic time scale, probably more comparable to a year than a moment in typical human experience.

1 million years is about 1/4500 of the geologic time scale, probably more comparable to 3 days or so than a moment in typical human experience.

Even if it were clear that a geologic time scale is being discussed, 1-100 million years seems like a lot more than a geologic "moment" when scaling to typical human experience.

If you ask someone for something and their reply is "I'll be with you in a moment" do you feel they have kept their word if their delay is between 3 days and 1 year?
 
  • #88
russ_watters
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100 million years is about 1/45 of the geologic time scale, probably more comparable to a year than a moment in typical human experience.

1 million years is about 1/4500 of the geologic time scale, probably more comparable to 3 days or so than a moment in typical human experience.

Even if it were clear that a geologic time scale is being discussed, 1-100 million years seems like a lot more than a geologic "moment" when scaling to typical human experience.

If you ask someone for something and their reply is "I'll be with you in a moment" do you feel they have kept their word if their delay is between 3 days and 1 year?
So what you are saying is you have no intention of discussing the topic the rest of us are discussing and would rather just keep arguing over what colloquial label to apply?
 
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  • #89
DaveC426913
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If you have a counter statement to make that is relevant to the discussion at-hand about how long it took life to form, feel free to make it.
I'd suggest that we save the discussion about definitions of 'moment' for a different thread in a different forum.
The meaning is clear from the context.
 
  • #90
berkeman
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Thread closed for Moderation...
 
  • #91
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About the last dozen of posts here seem to be an argument on how "moment" in the various timescales may be interpreted. So this thread has run its course. Furthermore the topic itself is highly speculative and opinions are driven by a vast number of additional assumptions, from religious over probabilistic to detection related ones. This isn't by no means an allegation, but since we don't even know, whether other life forms exist in our own solar system nor how they might look like, a basis to seriously debate upon seems not to be given.

Thread remains closed.
 

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