4 ms·

Is this the Great Filter?

benbreen 12y ago
Certainly seems like one of them, if this claim is true: "The Milky Way would therefore be among only 10% of all galaxies in the universe – the larger ones – that can sustain complex life in the long-term."
- fiatmoney 12y ago
  Actually, filters that select on galaxy scale are unlikely to be the "great filter", because we don't seem to see any artificially generated signals coming from within our own galaxy. This particular filter does strike within our own galaxy though, just to a lesser degree. So maybe.
  - api 12y ago
    It seems like it might exclude a lot of the galaxy, the central part, from hosting long lived complex life. This would mean that complex life is more common along the outer rim, where we are. This in turn means that the median distance between complex living biospheres might be very large, further reducing the likelihood of visitation or receiving signals.
    - jerf 12y ago
      There's a reasonably broad consensus that life isn't possible in the central part of the galaxy due to normal excessive radiation levels, even before considering extreme events. Of course, galactic size being what it is, these two "central parts" could have boundaries differing by, oh, say, twenty thousand light years no problem. I forget the details but I've seen arguments that too far away from the core is bad too.
- moyix 12y ago
  I thought the Fermi Paradox (and hence the Great Filter) was about the absence of life originating in our own galaxy? I don't think anyone has suggested that any species is likely be able to cross intergalactic distances.
  - api 12y ago
    It is, but on a side note: If you actually had the technology to accelerate to a speed close to light, time dilation might actually allow you to make an intergalactic journey as long as you were okay with leaving behind your home forever... Since a few years for you might be tens of millions of years elsewhere. There is also little matter between galaxies, so the hyper velocity particles problem would be less severe. Still total sci fi from where we are sitting, just saying that once you approach c distances shrink a lot (relative to your frame of reference). So if travel close to c is possible at all, travel almost anywhere is possible. This is one of the reasons the Fermi paradox is so interesting. There are tons of possible explanations. One simple one in this context is, of course, that accelerating to speeds that close to light is just physically impossible for various reasons. This would at least limit migration to nearby interstellar distances at best, which when combined with other factors would make intelligences encountering one another statistically rare in the universe. There was a sci fi book where a ship's Bussard Ramjet got stuck in the "on" position and they kept accelerating until time dilation allowed them to survive a great crunch and another Big Bang. By the time they stopped they were in a new universe.
    - mahranch 12y ago
      The issue with Fermi's Paradox is the fact that it's not a paradox at all. It relies on assumptions and presumptions that are now dated (we have explanations for). For starters, let's begin with the first point it makes; If there are a bunch of civilizations out there, why haven't we heard them yet? That's the wrong question. It makes an incorrect presumption; Why should we have heard them? Do you think a highly advanced civilization is going to be using something as archaic as "radio signals" to communicate across vast interstellar distances? Due to the inverse square law, it's incredibly inefficient, laughably so. It would be like trying to use smoke signals to communicate across oceans. A beam of light would be more efficient. But the beam would be instant and you could never "listen in" unless you were physically at the location of the target. And who knows what else, maybe they communicate with gravitational waves, or something else we haven't discovered yet. Perhaps something with quantum entanglement (although that's unlikely). Yet, all of those cannot be detected unless you were specifically the target of the communication. They're not like radio waves where you can listen in. That's actually the very reason why they're so inefficient, they're broadcast omnidirectional and that takes a lot of power - wasted power. And that's only one of the incorrect presumption Fermi's Paradox makes. There are more. I don't know why people keep bringing up the term when it's no longer applicable given what we know now. There is no paradox. There are plenty of great reasons why we haven't detected aliens yet, and none of them are paradoxical.
jjoonathan 12y ago
Probably not. <JeffGoldblum> Life will find a way! </JeffGoldblum> > The bacterium Deinococcus radiodurans is the best known extremophile among the few organisms that can survive extremely high exposures to desiccation and ionizing radiation, which shatter its genome into hundreds of short DNA fragments2, 3, 4, 5. Remarkably, these fragments are readily reassembled into a functional 3.28-megabase genome. Here we describe the relevant two-stage DNA repair process... figure [1] Direct radiation exposure is not the only threatening aspect of a GRB and even Deinococcus Radiodurans can't withstand the full onslaught of a nearby GRB [2], but I do believe that D.R. is a good enough proof of concept to argue that adaptation is not only feasible but probable. GRBs would set life back a few hundred million years (whether here or in a remote galaxy), but I doubt they would put an end to it. [1] http://www.nature.com/nature/journal/v443/n7111/fig_tab/nature05160_F2.html http://www.nature.com/nature/journal/v443/n7111/fig_tab/natu... [2] http://www.world-science.net/exclusives/070226_grb-life.htm http://www.world-science.net/exclusives/070226_grb-life.htm
- eloff 12y ago
  It's tough to imagine a similar process in a complex lifeform. So it could well be the great filter. Evolution doesn't work well with things that happen rarely over geological timescales. This is one reason why life on earth is very sensitive to climate change, even although the climate has gone through many major changes in the past.
  - jjoonathan 12y ago
    I wouldn't expect the ability to evolve in Eukaryotes if a GRB happened near Earth, but I see no reason why frequent GRBs in a distant galaxy would put a ceiling on complexity. Here's how I see it going down: 1. Life evolves. Not radiation resistant except for a group of bacteria that like to hang out in uranium-rich soil (or something). 2. GRB. Radiation-resistant bacteria repopulate the planet. 3. Radiation-resistant mechanism breaks in 99% of bacteria, but vestiges remain. 4. Mechanisms to handle bigger genomes evolve (Let's call them "eukaryotes" for the sake of the argument). 5. Single-celled "eukaryotes" invade the uranium-rich soil ecosystem by fixing the vestigial radiation resistant genes. 6. GRB. Radiation-resistant prokaryotes and radiation-resistant "eukaryotes" repopulate the planet. 7. Rinse, repeat. 8. Eventually there will be big multi-cellular radiation-resistant "eukaryotes" walking aroud. ---- > life on earth is very sensitive to climate change We are very sensitive to climate change, as are a bunch of higher organisms we care greatly about. Life on Earth? Not a chance. We couldn't come close to sterilizing the planet if we wanted to.

Certainly seems like one of them, if this claim is true: "The Milky Way would therefore be among only 10% of all galaxies in the universe – the larger ones – that can sustain complex life in the long-term."

fiatmoney 12y ago
Actually, filters that select on galaxy scale are unlikely to be the "great filter", because we don't seem to see any artificially generated signals coming from within our own galaxy. This particular filter does strike within our own galaxy though, just to a lesser degree. So maybe.
- api 12y ago
  It seems like it might exclude a lot of the galaxy, the central part, from hosting long lived complex life. This would mean that complex life is more common along the outer rim, where we are. This in turn means that the median distance between complex living biospheres might be very large, further reducing the likelihood of visitation or receiving signals.
  - jerf 12y ago
    There's a reasonably broad consensus that life isn't possible in the central part of the galaxy due to normal excessive radiation levels, even before considering extreme events. Of course, galactic size being what it is, these two "central parts" could have boundaries differing by, oh, say, twenty thousand light years no problem. I forget the details but I've seen arguments that too far away from the core is bad too.
moyix 12y ago
I thought the Fermi Paradox (and hence the Great Filter) was about the absence of life originating in our own galaxy? I don't think anyone has suggested that any species is likely be able to cross intergalactic distances.
- api 12y ago
  It is, but on a side note: If you actually had the technology to accelerate to a speed close to light, time dilation might actually allow you to make an intergalactic journey as long as you were okay with leaving behind your home forever... Since a few years for you might be tens of millions of years elsewhere. There is also little matter between galaxies, so the hyper velocity particles problem would be less severe. Still total sci fi from where we are sitting, just saying that once you approach c distances shrink a lot (relative to your frame of reference). So if travel close to c is possible at all, travel almost anywhere is possible. This is one of the reasons the Fermi paradox is so interesting. There are tons of possible explanations. One simple one in this context is, of course, that accelerating to speeds that close to light is just physically impossible for various reasons. This would at least limit migration to nearby interstellar distances at best, which when combined with other factors would make intelligences encountering one another statistically rare in the universe. There was a sci fi book where a ship's Bussard Ramjet got stuck in the "on" position and they kept accelerating until time dilation allowed them to survive a great crunch and another Big Bang. By the time they stopped they were in a new universe.
  - mahranch 12y ago
    The issue with Fermi's Paradox is the fact that it's not a paradox at all. It relies on assumptions and presumptions that are now dated (we have explanations for). For starters, let's begin with the first point it makes; If there are a bunch of civilizations out there, why haven't we heard them yet? That's the wrong question. It makes an incorrect presumption; Why should we have heard them? Do you think a highly advanced civilization is going to be using something as archaic as "radio signals" to communicate across vast interstellar distances? Due to the inverse square law, it's incredibly inefficient, laughably so. It would be like trying to use smoke signals to communicate across oceans. A beam of light would be more efficient. But the beam would be instant and you could never "listen in" unless you were physically at the location of the target. And who knows what else, maybe they communicate with gravitational waves, or something else we haven't discovered yet. Perhaps something with quantum entanglement (although that's unlikely). Yet, all of those cannot be detected unless you were specifically the target of the communication. They're not like radio waves where you can listen in. That's actually the very reason why they're so inefficient, they're broadcast omnidirectional and that takes a lot of power - wasted power. And that's only one of the incorrect presumption Fermi's Paradox makes. There are more. I don't know why people keep bringing up the term when it's no longer applicable given what we know now. There is no paradox. There are plenty of great reasons why we haven't detected aliens yet, and none of them are paradoxical.

jjoonathan 12y ago

Probably not. <JeffGoldblum> Life will find a way! </JeffGoldblum> > The bacterium Deinococcus radiodurans is the best known extremophile among the few organisms that can survive extremely high exposures to desiccation and ionizing radiation, which shatter its genome into hundreds of short DNA fragments2, 3, 4, 5. Remarkably, these fragments are readily reassembled into a functional 3.28-megabase genome. Here we describe the relevant two-stage DNA repair process... figure [1] Direct radiation exposure is not the only threatening aspect of a GRB and even Deinococcus Radiodurans can't withstand the full onslaught of a nearby GRB [2], but I do believe that D.R. is a good enough proof of concept to argue that adaptation is not only feasible but probable. GRBs would set life back a few hundred million years (whether here or in a remote galaxy), but I doubt they would put an end to it. [1] http://www.nature.com/nature/journal/v443/n7111/fig_tab/nature05160_F2.html http://www.nature.com/nature/journal/v443/n7111/fig_tab/natu... [2] http://www.world-science.net/exclusives/070226_grb-life.htm http://www.world-science.net/exclusives/070226_grb-life.htm

eloff 12y ago
It's tough to imagine a similar process in a complex lifeform. So it could well be the great filter. Evolution doesn't work well with things that happen rarely over geological timescales. This is one reason why life on earth is very sensitive to climate change, even although the climate has gone through many major changes in the past.
- jjoonathan 12y ago
  I wouldn't expect the ability to evolve in Eukaryotes if a GRB happened near Earth, but I see no reason why frequent GRBs in a distant galaxy would put a ceiling on complexity. Here's how I see it going down: 1. Life evolves. Not radiation resistant except for a group of bacteria that like to hang out in uranium-rich soil (or something). 2. GRB. Radiation-resistant bacteria repopulate the planet. 3. Radiation-resistant mechanism breaks in 99% of bacteria, but vestiges remain. 4. Mechanisms to handle bigger genomes evolve (Let's call them "eukaryotes" for the sake of the argument). 5. Single-celled "eukaryotes" invade the uranium-rich soil ecosystem by fixing the vestigial radiation resistant genes. 6. GRB. Radiation-resistant prokaryotes and radiation-resistant "eukaryotes" repopulate the planet. 7. Rinse, repeat. 8. Eventually there will be big multi-cellular radiation-resistant "eukaryotes" walking aroud. ---- > life on earth is very sensitive to climate change We are very sensitive to climate change, as are a bunch of higher organisms we care greatly about. Life on Earth? Not a chance. We couldn't come close to sterilizing the planet if we wanted to.