Jump to content
Cold?
Local
Radar
Snow?

Do you believe in possibility of life in other galaxies?


Recommended Posts

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.   

    Link to post
    Share on other sites
    Spotted a post you think may be an issue? Please help the team by reporting it.
    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
    • Thanks 1
    Link to post
    Share on other sites
    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).

    • Like 2
    Link to post
    Share on other sites

    Create an account or sign in to comment

    You need to be a member in order to leave a comment

    Create an account

    Sign up for a new account in our community. It's easy!

    Register a new account

    Sign in

    Already have an account? Sign in here.

    Sign In Now
    • Cold waves hitting Europe continue to threaten growers, is there a link to climate change?

      Much of Europe, not just the UK, has experienced unseasonably cold weather since the Easter Weekend. A plunge of cold arctic air brought by northerly winds early last week brought several nights of frost and even snow across large swathes of Europe, followed by another wave of cold arctic air spreads across much of Europe this week. The frosts causing damage to new growth in vineyards and orchardsa0spurred on by a late March heatwave, the vineyards of France werea0particularly badly affected.

      Nick F
      Nick F
      Latest weather updates from Netweather 3

      High pressure rules, but still chilly out the sun & watch out for a few showers

      High pressure in charge for the rest of the week but the airmass will be chilly, so feeling nippy out of the sun. Not entirely dry either, with scattered showers around the next few days, especially in the west. Read the full update here

      Netweather forecasts
      Netweather forecasts
      Latest weather updates from Netweather

      You'll need your coat because it's still cold out of the sun

      More April snow for Monday morning with a widespread frost. If you have outdoor plans this week, the chill in the air remains especially once the sun goes down. Read the full update here

      Netweather forecasts
      Netweather forecasts
      Latest weather updates from Netweather
    • Recently Browsing   0 members

      No registered users viewing this page.

    ×
    ×
    • Create New...