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Do you believe in possibility of life in other galaxies?


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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
4 hours ago, Relativistic said:

It's essentially an impossibility that life doesn't exist elsewhere. The likes of Mars and Enceladus even just within the solar system are strong candidates.

However, as others have alluded to, complex lifeforms such as ourselves may we far rarer. It's taken over three billion years for intelligent life to evolve from the first single-celled organisms that appeared on Earth. Put another way, it took relatively stable conditions over time scales comparable to the age of the Universe to cook up humanity; if Earth is in any way representative of the majority of occurrences of intelligent life, then one has to ask questions about the assumptions that are fed into estimates on the number of intelligent species in our galaxy. Earth-like exoplanets are frequently discovered, but how likely is it that their local environments remain stable enough to facilitate the development of intelligent life? Perhaps humanity won a cosmological lottery?

My opinion is that the number of intelligent civilisations in the Milky Way is very low. The Milky Way is approximately 8 trillion cubic light years in volume, so even if as much as a thousand such civilisations existed at the present time (whatever that means), then one can roughly expect each one to occupy a cube of side length 2000 light years. That's a long way to travel to meet your next-door neighbour, and I consider that an under-estimate.

As for Fermi's paradox, given the above argument, and the fact that we've only been searching the skies for a relatively miniscule period of time, it's not that surprising that we've neither come into contact with intelligent life, nor have we conclusively detected it (although there have been a couple of candidates; see the Wow! signal).

It's interesting that your point concludes the likelyhood being relatively low while actually i'd say it makes it fairly high. 

The Milky Way has existed for around 3 times the age of our solar system and we know that 95% of stars are class G, K or M (all of which live at least as long as our sun - arguably class F stars also live long enough to produce your 3 billion year threshold). That's a significant sample of stars which cross our age threshold even now, let alone through the life of the galaxy.

Even if 1% of stars host intelligent life then thanks to sheer numbers your 1000 example begins to look quite low.   

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Posted
  • Location: Edinburgh (previously Chelmsford and Birmingham)
  • Weather Preferences: Unseasonably cold weather (at all times of year), wind, and thunderstorms.
  • Location: Edinburgh (previously Chelmsford and Birmingham)
1 hour ago, summer blizzard said:

It's interesting that your point concludes the likelyhood being relatively low while actually i'd say it makes it fairly high. 

The Milky Way has existed for around 3 times the age of our solar system and we know that 95% of stars are class G, K or M (all of which live at least as long as our sun - arguably class F stars also live long enough to produce your 3 billion year threshold). That's a significant sample of stars which cross our age threshold even now, let alone through the life of the galaxy.

Even if 1% of stars host intelligent life then thanks to sheer numbers your 1000 example begins to look quite low.   

 

Yes, that is true, but the stability of a star is not the only thing to take into account here.

 

Firstly, events other than the deaths of stars could feasibly cause total extinctions (or close to). In three billion years, Earth hasn't had, as far as I'm aware, an extinction event that has sent us from macroscopic organisms straight back to microbial life, or even no life at all. There are innumerable asteroids present in the solar system that are capable of doing so, and there's no evidence to suggest that features similar to the asteroid belt are uncommon in star systems (in fact, they're a corollary of our theories of star-system formation).

Supernovae, which occur in our galaxy two or three times per century, also have the potential to cause extreme extinction events. A back-of-the-envelope calculation on this is quite interesting. I found the following figures regarding supernovae in the Milky Way:

Rate of supernovae: approximately two per century;
Supernova safe zone (i.e. minimum distance to a supernova that would not pose a serious threat to life): 50-100 light-years;
Volume of the Milky Way: 8 trillion cubic light-years.

If we assume a best-case scenario of one supernova per century and a safe zone of 50 light-years, then you'd expect the entire galaxy to have been "supernova'd" (to have been within the deadly zone of a supernova) in about 10 billion years. So in the 3 billion years that it took humanity to evolve here on Earth, by this estimate there was a reasonable chance that things could have gone very wrong. Perhaps our local neighbourhood of stars has been kind to us. Nearer the centre of the galaxy, where the density of stars is much higher, such events may drastically hinder intelligent life's chances.

On top of this is the threat of volcanic eruptions. The most recent super-eruption wiped out most terrestrial life on Earth, although marine life was less severely affected. Earth is fortunate in this sense because there are a multitude of deep-sea "hiding places", which other water-harbouring planets might not have.

 

Secondly, a large fraction of stars in the Milky Way are members of multi-star systems. It's harder to envisage the emergence of complex life in these places as host planets are far more likely to have erratic orbits which cause unstable surface conditions (such as large temperature swings), although this is part speculation from me.

 

It's worth pointing out that many of the arguments made here won't necessarily apply to microbial life.


When it comes to the Fermi paradox, either intelligent life really is very rare, or intelligent life isn't so rare but quickly exterminates itself once established. The resolution to this depends on what you perceive to be more likely. If you think stable-enough environments are common throughout the galaxy (i.e. that Earth's stable history is typical and not a fluke), then things don't look so rosy for humanity; on the other hand, if you think Earth is a rare exception, then we might not have so much to worry about.

Edited by Relativistic
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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

The neighbourhood is a good point to make as we appear to be suburban. We do live in a region of space which is quite dense (about 4000 stars inside 100 light years) but our immediate neighbourhood is mainly full of M type stars. Only Tau Ceti and one of the Gillesse systems are old and K/G type within 15 light years (and not in a binary system - I agree that radiation means lone stars probably are more likely to produce life). This means that if there is a lot of life in K/G/F type single systems, we are near the edge of the cluster and so somewhat isolated. Of course if life is on M class star world's we are equally in luck potentially (but I consider it less likely even if age means the probability will be high potentially).

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  • 2 months later...
Posted
  • Location: Rossland BC Canada
  • Location: Rossland BC Canada

Just as a philosophical question, how would one go about proving the non-existence of life in the rest of the galaxy, let alone in other galaxies? 

You could never get closer than indications, I would submit, and there are only two possible indications --

-- non-existence of suitable habitats (already disproven) and

-- non-appearance of other life forms (already disputed).

For other galaxies we are pretty much going on the assumption that their star and therefore planet populations are similar to our galaxy (with scale being a factor, ours is one of the larger ones). There is no obvious reason why life would be more or less likely in other galaxies than in our galaxy and we already know there's life in our galaxy. 

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Posted
  • Location: St rads Dover
  • Weather Preferences: Snow, T Storms.
  • Location: St rads Dover

There must be life in other galaxies in my view, it's impossible, with all the possible opportunities, we are the only planet anywhere with life. Even if it's just a few cells of something or other, it's still life, and may even exist in this very galaxy, on other planets to. Would just be unlikely to be carbon based.

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Posted
  • Location: Kensington
  • Location: Kensington
19 minutes ago, Roger J Smith said:

Just as a philosophical question, how would one go about proving the non-existence of life in the rest of the galaxy, let alone in other galaxies? 

You could never get closer than indications, I would submit, and there are only two possible indications --

-- non-existence of suitable habitats (already disproven) and

-- non-appearance of other life forms (already disputed).

For other galaxies we are pretty much going on the assumption that their star and therefore planet populations are similar to our galaxy (with scale being a factor, ours is one of the larger ones). There is no obvious reason why life would be more or less likely in other galaxies than in our galaxy and we already know there's life in our galaxy. 

Its difficult   best estimates state there is around 60 billion planets in the goldilocks zone just in the milky way   odds are that some will harbour life   the number is mind-boggling if we take in the whole universe    intact some leading experts state that there are so many potential planets that could harbour life  that it  is possible that not only could humans exist on other planets  but infact there could be planets with exact replicas of oursevelves   taking various decisions that would lead to our lives panning out differently   kind of like a parrarel  earth    mind blown 

Edited by weirpig
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  • 4 weeks later...

I want to mention is that Earth's atmosphere not only gives us O2 but also saves us from the harmful rays of the sun. This is also very rare, none of the planets in the solar system has that kind of atmosphere. There are many other things that may extinct all life on Earth but are not happening because the Earth is, the way it is(example: Earth's magnetic property)

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  • 3 weeks later...
Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

I've been convinced that there's intelligent life elsewhere in the universe since the 1960s, even though I'm highly sceptical of most UFO sightings:

And then, back in the 1990s, I saw one myself: there was a stationary, silent black triangle (it blotted out the stars) directly overhead. My first thought was a Vulcan bomber, my second, a stealth bomber -- even an equilateral cloud! -- but, can either of those things silently hover? They can't, can they? So now I am stuck with a dilemma: either I admit to being an X-Files looney tune -- or I simply say what I saw . . . So, I'll simply say what I saw!

Edited by Ed Stone
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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
On 22/07/2021 at 09:02, bearnard18 said:

However, many people assume that Proxima B might have the same Environment as Earth. I guess we will have more detailed information when the James Webb Space Telescope will be launched

Proxima B is likely tidally locked so more likely to be Titan like (i.e. pre earth) since the Oxygen mainly came from life developing and Proxima has a lot more radiation preventing that.

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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

The existence of Venus does suggest a high likelyhood outside our solar system though even before we consider Mars and Titan.

Venus likely had oceans and an early earth atmosphere until a billion years ago and has a magnetic field.

Edited by summer blizzard
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Posted
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
  • Weather Preferences: Sunshine and 15-25c
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
36 minutes ago, summer blizzard said:

The existence of Venus does suggest a high likelyhood outside our solar system though even before we consider Mars and Titan.

Venus likely had oceans and an early earth atmosphere until a billion years ago and has a magnetic field.

im pretty sure that simple life has existed on both Venus and Mars and some point..which means that life has developed to some degree or another on at least 3 planets in our own solar system ..so i would assume that simple life is very common throughout the galaxy...it is also a possibility that intelligent life could have developed on Earth much earlier under the right circumstances ..one example is before the rise of the dinosaurs some 250 million years ago when mammal like creatures were starting to dominate the planet but got wiped out by the Permian extinction..had this not happened maybe the would have evolved into an intelligent civilization 200 million years ago..if evolution followed the same course as it did after the extinction of the dinosaurs that gave rise to intelligent humans?

IMO it must have happened elsewhere if evolution follows the same sets of rules and outcomes?

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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

Agreed. 

When you consider that it only took earth a billion years to form simple life and we know of three planets with a liquid ocean for circa a billion years minimum it is probable. Indeed complex life then came around 3 billion years later which we now believe Venus had a liquid medium for.

And yes, good point. 

 

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  • 2 years later...
Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

Absolutely, I do (but where has the 'Do You Believe in Aliens?' thread gone?). It's all down to Quantum Biology?

 

Edited by Methuselah
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Posted
  • Location: Arnside ,where people go to die 9000m Asl
  • Weather Preferences: All weather
  • Location: Arnside ,where people go to die 9000m Asl

Only the human race could entertain such hubris to consider  itself as the only intelligent civilisation in the universe 

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
3 minutes ago, Scuba steve said:

Only the human race could entertain such hubris to consider  itself as the only intelligent civilisation in the universe 

But didn't we create God in our own image?

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Posted
  • Location: Arnside ,where people go to die 9000m Asl
  • Weather Preferences: All weather
  • Location: Arnside ,where people go to die 9000m Asl
9 minutes ago, Methuselah said:

But didn't we create God in our own image?

A bit of reverse Genesis,lol that’s theological question 😂

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
4 minutes ago, Scuba steve said:

A bit of reverse Genesis,lol that’s theological question 😂

I blame Spock; it was all his fault! :drunk-emoji:

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Posted
  • Location: Arnside ,where people go to die 9000m Asl
  • Weather Preferences: All weather
  • Location: Arnside ,where people go to die 9000m Asl
2 minutes ago, Methuselah said:

I blame Spock; it was all his fault! :drunk-emoji:

lol, that’s entirely logical 😂

Edited by Scuba steve
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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
Just now, Scuba steve said:

lol, that’s entirely logical 

My ex-wife told me I was like Mr Spock. . . Maybe that's why she's my EX-wife! 😁

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Posted
  • Location: East coast side of the Yorkshire Wolds, 66m ASL
  • Weather Preferences: Snow, Storms, and plenty of warm sunny days!
  • Location: East coast side of the Yorkshire Wolds, 66m ASL
19 minutes ago, Methuselah said:

But didn't we create God in our own image?

Its all Apples and snakes to me 😂

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Posted
  • Location: Arnside ,where people go to die 9000m Asl
  • Weather Preferences: All weather
  • Location: Arnside ,where people go to die 9000m Asl
7 minutes ago, Wold Topper said:

Its all Apples and snakes to me 😂

 

 

7 minutes ago, Wold Topper said:

Its all Apples and snakes to me 😂

lol, would you Adam and Eve it 😂

Edited by Scuba steve
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Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
13 hours ago, Scuba steve said:

Only the human race could entertain such hubris to consider  itself as the only intelligent civilisation in the universe 

We are not that intelligent as we destroy our environment. There's also other intelligent life on earth

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