Opinion on Rare Earth Theory: Exploring Life Beyond Our Solar System

In summary, the conversation revolves around the question of whether life is rare or abundant in the universe. Some argue that since we have not yet explored other galaxies, it is premature to make a judgment. However, others point out that even within our solar system, the lack of radio or other EM signals suggests that life may indeed be rare. The discussion also touches on the idea of a "freak event" leading to the development of intelligent life, and the possibility that different planets may have different evolutionary paths. Ultimately, it is agreed that the lack of empirical evidence makes it difficult to draw any conclusions about the prevalence of life in the universe.
  • #1
Holocene
237
0
What is everyones opinion on this?

How can we say life is rare in the universe when not only haven't we explored other galaxies, but have yet to even venture out of our solar system (excluding Voyager 1)?
 
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  • #2
We don't have to leave our solar system to notice the complete absence of radio or other EM signals in our sky.
 
  • #3
DaveC426913 said:
We don't have to leave our solar system to notice the complete absence of radio or other EM signals in our sky.
On the other hand, the absence may simply be due to the very low signal to noise ratio.

I am not sure that we could detect a faint signal from the Andromeda galaxy.

I think the power of most terrestrial systems are on the MW, and I imagine that the signals are rather feeble 1 light year away, let alone 100's, 1000's, million of ly away.
 
  • #4
Yeah but if we're looking 2M ly away for life, I'd call that rare.
 
  • #5
DaveC426913 said:
Yeah but if we're looking 2M ly away for life, I'd call that rare.

But the observable universe is 4000 Billion cubic light years!
Still one life per galaxy would be incredibly rare.
 
  • #6
DaveC426913 said:
Yeah but if we're looking 2M ly away for life, I'd call that rare.

Of course, finding it there would mean that the civilization is at least 2M years old. A newer one wouldn't know about us either.
 
  • #7
Maybe in the Milky Way or Local Cluster, the Earth is rare.

Are stars like the Sun rare? G2V
 
  • #8
Looking at the recent article about how humans may not have evolved to this point except for a freak collision with that asteroid 65 million years ago, and considering how long it would take for any transmissions we might be able to detect to reach us, I'd say that it's rather naive to consider ourselves the only life.
 
  • #9
Evo said:
Looking at the recent article about how humans may not have evolved to this point except for a freak collision with that asteroid 65 million years ago,
?

Doesn't a freak event leading to our existence imply a lower probability of intelligent life elsewhere?
 
  • #10
Evo said:
Looking at the recent article about how humans may not have evolved to this point except for a freak collision with that asteroid 65 million years ago
Something calling itself human might have evolved, it's just that it would have green scales and lay eggs.
 
  • #11
DaveC426913 said:
?

Doesn't a freak event leading to our existence imply a lower probability of intelligent life elsewhere?
It depends on what type of life developed on the other planets. In our case dinosaurs were predominant, once they were gone, we had a chance to develop. Another planet may have never developed giant dinosaurs. We can't expect every world to develop exactly as the Earth did.
 
  • #12
We are not making much progress on the empirical side, either:

http://www.livescience.com/space/news/070823_mars_life.html
 
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  • #13
Evo said:
It depends on what type of life developed on the other planets. In our case dinosaurs were predominant, once they were gone, we had a chance to develop. Another planet may have never developed giant dinosaurs. We can't expect every world to develop exactly as the Earth did.
But the logic here is that, in the only example of intelligent life in the known universe, it didn't come about without a _freak_ accident as a prerequisite. The implication is that the preconditions for intelligence are rare, which implies that intelligent life is a freak event.
 
  • #14
DaveC426913 said:
But the logic here is that, in the only example of intelligent life in the known universe, it didn't come about without a _freak_ accident as a prerequisite. The implication is that the preconditions for intelligence are rare, which implies that intelligent life is a freak event.
No, just in our case. On another planet a freak asteroid hit could wipe out what would have become intelligent life, the lack of such an accident could leave intelligent life evolving normally.
 
  • #15
the lack of such an accident could leave intelligent life evolving normally.

We will become extinct. Period. There is no endpoint in evolution, and, god help us, I'm sure we are not any kind of flowering pinnacle. More like a peduncle with any luck.

And if it matters, ants have already won the evolution cup for terrestrial animals. --- E. O. Wilson's point of view anyway. Us humans count for nada.
 
  • #16
mgb_phys said:
Something calling itself human might have evolved, it's just that it would have green scales and lay eggs.

Agreed. There's no reason to believe that reptiles wouldn't have achieved our level of intelligence had they been given the chance. My money would be on the small, fast ones. From what I've seen of fossil evidence, it looks as if their forepaws were well on the way to being capable of tool use.
 
  • #17
Danger said:
Agreed. There's no reason to believe that reptiles wouldn't have achieved our level of intelligence had they been given the chance.
I really don't know about that. If dinos had continued to rule the planet, would they have had any evolutionary pressure to develop intelligence? Mammals had strong pressure to evolve intelligence (I would think) as a way to stay out of the mouths of nasties.
 
  • #18
Rare Earth "theory" is about as useful as a hole in your head. So life on Earth has evolved to best make use of the planet, wow, so what does that tell us about life in the universe? Not a lot - other than perhaps how significant astronomical and geological events/processes are to evolution. Chemoautotrophs don't even need sunlight - that's a bit of a kick in the balls. The so-called "Fermi paradox" has plenty of possible solutions, so I wouldn't worry too much about lack of ETI signal detection.
 
  • #19
billiards said:
The so-called "Fermi paradox" has plenty of possible solutions, so I wouldn't worry too much about lack of ETI signal detection.
No, that actually highlights the Fermi Paradox. If there are plenty of solutions, then it is more odd why we don't see life everywhere we look.
 
  • #20
jim mcnamara said:
We will become extinct. Period. There is no endpoint in evolution, and, god help us, I'm sure we are not any kind of flowering pinnacle. More like a peduncle with any luck.

And if it matters, ants have already won the evolution cup for terrestrial animals. --- E. O. Wilson's point of view anyway. Us humans count for nada.

I love Wilson's work. Nevertheless, to say that humans count for nada is only true if the ants count for nada (thereby all things equally count for nada).

Back to the OP, even if life is rare, and even if only one life-sustaining system exists for every 100 galaxies, that still means 100s of millions of life-sustaining systems. I have no doubt that there has been ,is, and will be other "Earth's" out there. I also have little hope that contact will ever be made. (I think that's what most of us think anyway, isn't it?)
 
  • #21
DaveC426913 said:
No, that actually highlights the Fermi Paradox. If there are plenty of solutions, then it is more odd why we don't see life everywhere we look.
Huh? I don't follow. The way I was looking at, if there are plenty of solutions (by that I mean things that would undo the "paradox") to explain why we can't detect signals from ETI (extra-terrestrial intelligent life forms), then it should not be too revealing (as to the state of ETI in the universe) that we have not detected any (ETI signals).
 
  • #22
Maybe the ETI signals are cleverly disguised as noise so that they may spy on our activities and conduct social experiment on us by planting their own kid as leaders of the free world.

Or not.

I am certain intelligent life has/does exist somewhere out there.
 
  • #23
DaveC426913 said:
Mammals had strong pressure to evolve intelligence (I would think) as a way to stay out of the mouths of nasties.

But so did smaller reptiles, and the small mammals that evolved along with sabretooth tigers.
 
  • #24
A few years ago it was believed that we would be able to detect alien life via radio waves. But a scant 60 years after the first high power transmissions, signal strengths are poised to drop to the point where what we emit into space accidentally would not be detectable/deciperable even just a few light years away. So even if the galaxy were teeming with intelligent life, odds are we would never detect it with our current search methods. There are other ways to detect life, and I expect that within my lifetime, new ways of searching will answer the question to the satisfaction of scientists (but not necessarily laypeople).

So the answer to the question of why we don't detect life everywhere may simply be: how could we possibly detect life anywhere?
 
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  • #25
life is rare in the universe because when life started in the Earth it had to fight with environment and it developed in a complex way of life which is not possible in other planets for this you have to understand how Earth created after a comet collied with it and that does not happen with every planet that's why Earth developed this rare and complex life sequence.
 
  • #26
But complex life had evolved long before the comet strike. Who can say what would have happened had the strike not occurred?
Which brings to mind a pet peeve. In almost every SF series or movie that I've seen, the reptilian and avian females have significantly apparent tits. Since when do egg-laying species (other than platipi) use them? (Not that I mind watching them, though.)
Which also brings to mind:

"[PLAIN][PLAIN [/PLAIN]

Sorry; I know that it's a rerun, but it seemed appropriate.
 
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  • #27
anurag dimri probably had no idea s/he was necroposting.

Danger said:
Which brings to mind a pet peeve. In almost every SF series or movie that I've seen, the reptilian and avian females have significantly apparent tits. Since when do egg-laying species (other than platipi) use them?
Seriously, that's where you draw the line at plausibility? :wink:
 
  • #28
DaveC426913 said:
If dinos had continued to rule the planet, would they have had any evolutionary pressure to develop intelligence? Mammals had strong pressure to evolve intelligence (I would think) as a way to stay out of the mouths of nasties.
So had dinosaurs - there were all these other big nasty fierce dinosaurs around !
Evolution works at the level of a species not an order.
 
  • #29
DaveC426913 said:
Seriously, that's where you draw the line at plausibility? :wink:

No, but of my peeves this was the most titillating... :uhh:
 
  • #30
In almost every SF series or movie that I've seen, the reptilian and avian females have significantly apparent tits.
Put on the TV showings they all had some sort of necklace/jewelry that miraculously stayed in place to cover their nipples?
 
  • #31
Danger said:
No, but of my peeves this was the most titillating... :uhh:

I'm abreast with you on that issue.
 
  • #32
Oh well, I left it open for awhile.
 

1. What is the Rare Earth Theory?

The Rare Earth Theory is a scientific hypothesis that suggests that the emergence of complex life on Earth is a rare and unique event, and that the conditions necessary for complex life to evolve are not common in the universe.

2. What evidence supports the Rare Earth Theory?

Some evidence that supports the Rare Earth Theory includes the fact that Earth is the only known planet to have both liquid water and plate tectonics, which are believed to be crucial for the development and sustenance of life. Additionally, the existence of a large moon, a magnetic field, and a stable orbit are all factors that contribute to Earth's habitability and are not commonly found in other planets.

3. Why is the Rare Earth Theory controversial?

The Rare Earth Theory is controversial because it challenges the idea that life is abundant in the universe and that there may be many other habitable planets like Earth. It also goes against the principle of mediocrity, which suggests that Earth and the conditions that allowed for life to evolve are not unique.

4. What are some alternative theories to the Rare Earth Theory?

Some alternative theories to the Rare Earth Theory include the Copernican principle, which states that Earth is not special and that life is likely to exist on other planets, and the Panspermia theory, which suggests that life on Earth may have originated from microorganisms that were brought to our planet from elsewhere in the universe.

5. How does the Rare Earth Theory impact the search for extraterrestrial life?

The Rare Earth Theory has led scientists to focus their search for extraterrestrial life on planets that have similar characteristics to Earth, such as being in the habitable zone of their star, having a large moon, and having a stable orbit. It also highlights the importance of studying Earth and its unique features in order to better understand the conditions necessary for life to exist on other planets.

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