4 ms·

I saw this gif on reddit a few days ago which really puts into perspective how _slow_ the speed of light actually is. Fermi Paradox? There's yer problem right

I saw this gif on reddit a few days ago which really puts into perspective how _slow_ the speed of light actually is. Fermi Paradox? There's yer problem right there: https://preview.redd.it/w67ihk0r2ly71.gif?format=mp4&s=4611c264ba207548072dd10628eadadba1e9cc10 https://preview.redd.it/w67ihk0r2ly71.gif?format=mp4&s=4611c...

jjoonathan 5y ago
Light is only slow relative to human timescales. It's wicked fast on evolutionary timescales. Even accounting for sublight speeds and conservative spreading assumptions, galactic colonization should only take millions of years, not billions. Evolution has taken billions of years. So if an alien civilization in our galaxy got a billion year headstart -- which would be an unremarkable change to the evolutionary timeline -- then they should already have colonized the galaxy. They should be everywhere, and we should see them, but we don't.
- tsimionescu 5y ago
  Life has existed on Earth for almost a third of the lifetime of the universe as far as we can tell. This doesn't leave that much room for older civilizations, especially if it happens that life on Earth was especially fast evolving.
  - harles 5y ago
    John has existed for about a third of the time since the industrial revolution. This doesn’t leave much room for people who have earned more money, especially if it turns out John was an especially fast earner. Therefore, we shouldn’t expect to find billionaires yet.
    - tsimionescu 5y ago
      What I pointed out is not some iron-clad argument that it's impossible for there to be galactic empires or that people with reasonable assumptions can't be surprised that the universe isn't teaming with life. My point was that it's also not unreasonable to not be surprised. After all, we know for sure that, even if the universe is eventually full of life, there must still exist at least one species with our experience - looking out and seeing no one else. That one species guaranteed to have this experience is of course the first one that starts colonizing. To be clear again, I'm not claiming that we are for sure the first ones - there are many other reasonable explanations, but I believe this one is too.
      - harles 5y ago
        There’s a lot to unpack there and I think it’s missing the point that extreme outliers exist but we shouldn’t expect ourselves to be one. It’s akin to saying some people win the lottery therefore it’s unsurprising if we do. Yes, some civilization will be first. The odds of it being us are astronomically low based on time and # of planetary systems. Given that it’s exponential growth, it’ll likely either never start or quickly explode. If a capable species came even 0.01% before us, we’d expect to see them. If a species came after us but had even a slightly faster growth rate, we’d expect to see them. The Fermi paradox is puzzling because time is on the side of galaxy colonizing civilizations, not against it. There are many possible explanations to the Fermi paradox, but “we’re the first” is extremely naive.
  - tshaddox 5y ago
    Right. There are a bunch of stars that are way older than our Sun. (Remember, the Sun is pretty much the same age as Earth.)
  - jjoonathan 5y ago
    Right, on first glance "we really might be first" looks like a poor hypothesis -- it's inconsistent with the mediocrity principle, it plays into dangerous self-centered cognitive biases -- but it's actually one of the better Fermi paradox solutions. If I had to bet, I'd bet that we were first, and that it happened due to an early filter. I can hear a crowd of doomers grabbing their pitchforks and torches, screaming "late filter, late filter," but I don't buy it. There are many plausible apocalypse scenarios that would wipe out most of humanity and make life miserable for a long time -- but finishing the job is a very different thing, and you have to reach deep into the scenario bag to find an apocalypse that actually does the trick. In contrast, there are a bunch of cellular biology innovations that sound magnificently tricky to evolve. Cellular membranes and the eukaryotic transition are two that stand out, but who knows. Point is: I find the "early filter" hypotheses easy to believe, and not just because they wind up being good news in the end.
    - tsimionescu 5y ago
      I agree with all or most of your comment. I wanted to comment a little bit on this though: > ["we really might be first"] plays into dangerous self-centered cognitive biases I'm not so sure that this bias exists to a great extent, and in fact an opposite bias seems to be to prevalent - in almost all art, there is always an assumption of some older more advanced progenitor race, some old golden age of advanced wisdom. This is true happens in the Epic of Gilgamesh (the antediluvian civilization was more advanced) just as in modern video games.
- kokanee 5y ago
  I don't think it's accurate to say that light is slow on any timescale. It's literally the fastest thing, no matter what scale you're on. The issue at hand, and the reason that we can make light look slow, is that we can't comprehend the distances we're talking about covering. No one said anything about restricting the search for life to our galaxy, so let's set that aside. Given the distances involved, the odds that evolution has gone complex in more than one galaxy are high, but the odds that we might find evidence of this are low.
  - jjoonathan 5y ago
    Yes, it's true, to define a velocity scale you need to plug in a spatial scale and a temporal scale. A human lifetime defines the temporal scale, but I technically didn't mention a spatial scale. However, we were talking about Fermi paradox and galactic colonization -- so a reasonable spatial scale would be that of the galaxy, and then we have defined a velocity scale and can make comparisons: c << (galactic diameter / human lifetime) c >> (galactic diameter / billion year evolutionary lead)
  - dhosek 5y ago
    The end of the gif with the distances between the sun, Mercury, Venus and Earth to scale is kind of informative and then you look at the fine print that indicates that with that scale the planets are all represented at 50x and the sun at 2x and it really makes the distances that much more amazingly large. And I have to confess that my mental image of the distance from Mercury to the sun was way off—I'd always envisioned it as being close enough that the sun would fill the daytime sky but really it would just look about 2.5–3 times bigger than it does on Earth.
- jjk166 5y ago
  But intelligent civilizations don't exist on evolutionary timescales, they exist on the timescales of intelligent beings, like us. We struggle to maintain projects for more than a few years, a tiny fraction of our lifetimes. Our oldest institutions are only a few thousand years old, dozens of generations. Many of our civilizations rose and fell within centuries. Our species is much less than a million years old, and while it is unclear how long we will last, it seems pretty optimistic to think we are in the first few percent of our species history, nonetheless the first few thousandths of a percent of our civilization's history. If we had built ships travelling at 1% of lightspeed to colonize the galaxy, and launched them when the common ancestor of humans and chimps lived, some of them would still be travelling to their destinations. Maybe there are rare species that live on timescales tens, hundreds, even thousands of times longer than ours, but even for them these would be long time periods. And it's not enough to simply reach these distant star systems, you need to survive there indefinitely. A billion years is a long time, much longer than complex life has existed on Earth. Most of Earth's crust is less than 250 million years old. Objects in space would be pulverized to dust by a billion years of collisions, assuming their orbits were even stable for anywhere near that long. On timescales like that, even structures made of solid granite would erode away on a planet's surface. Maybe by looking for weird minerals which couldn't have formed naturally or microfragments of broken down structures we could identify a civilization as having existed in the deep geologic past, but there is no way we could do that sort of analysis from light years away, even if we knew what to look for. Realistically, there are only a few technosignatures we could hope to find. Of course there are active radio transmissions, which requires the civilization to be active in an incredibly narrow timeframe. Exoplanet atmospheres containing short lived gases with no known natural production mechanism would be good, and may outlive a civilization, but anything stable enough to last for geologic timescales would be impossible to rule out as natural. Probably the longest lived evidence that we could detect would be the remnants of alien megastructures in space. No one really knows how long say a dyson sphere would last after it stops being maintained, maybe millions of years. But unless we make some extremely tenuous assumptions about what and how alien civilizations would construct megastructures, we can only make extremely rough guesses as to what a functional megastructure would look like, nonetheless one that has suffered millions of years of wear and tear. Of course eventually they'll all start to look like clouds of dust and debris, but how do we distinguish them from the clouds of dust and debris that we find all over the place with a presumed natural origin?

jjoonathan 5y ago

Light is only slow relative to human timescales. It's wicked fast on evolutionary timescales. Even accounting for sublight speeds and conservative spreading assumptions, galactic colonization should only take millions of years, not billions. Evolution has taken billions of years. So if an alien civilization in our galaxy got a billion year headstart -- which would be an unremarkable change to the evolutionary timeline -- then they should already have colonized the galaxy. They should be everywhere, and we should see them, but we don't.

tsimionescu 5y ago
Life has existed on Earth for almost a third of the lifetime of the universe as far as we can tell. This doesn't leave that much room for older civilizations, especially if it happens that life on Earth was especially fast evolving.
- harles 5y ago
  John has existed for about a third of the time since the industrial revolution. This doesn’t leave much room for people who have earned more money, especially if it turns out John was an especially fast earner. Therefore, we shouldn’t expect to find billionaires yet.
  - tsimionescu 5y ago
    What I pointed out is not some iron-clad argument that it's impossible for there to be galactic empires or that people with reasonable assumptions can't be surprised that the universe isn't teaming with life. My point was that it's also not unreasonable to not be surprised. After all, we know for sure that, even if the universe is eventually full of life, there must still exist at least one species with our experience - looking out and seeing no one else. That one species guaranteed to have this experience is of course the first one that starts colonizing. To be clear again, I'm not claiming that we are for sure the first ones - there are many other reasonable explanations, but I believe this one is too.
    - harles 5y ago
      There’s a lot to unpack there and I think it’s missing the point that extreme outliers exist but we shouldn’t expect ourselves to be one. It’s akin to saying some people win the lottery therefore it’s unsurprising if we do. Yes, some civilization will be first. The odds of it being us are astronomically low based on time and # of planetary systems. Given that it’s exponential growth, it’ll likely either never start or quickly explode. If a capable species came even 0.01% before us, we’d expect to see them. If a species came after us but had even a slightly faster growth rate, we’d expect to see them. The Fermi paradox is puzzling because time is on the side of galaxy colonizing civilizations, not against it. There are many possible explanations to the Fermi paradox, but “we’re the first” is extremely naive.
- tshaddox 5y ago
  Right. There are a bunch of stars that are way older than our Sun. (Remember, the Sun is pretty much the same age as Earth.)
- jjoonathan 5y ago
  Right, on first glance "we really might be first" looks like a poor hypothesis -- it's inconsistent with the mediocrity principle, it plays into dangerous self-centered cognitive biases -- but it's actually one of the better Fermi paradox solutions. If I had to bet, I'd bet that we were first, and that it happened due to an early filter. I can hear a crowd of doomers grabbing their pitchforks and torches, screaming "late filter, late filter," but I don't buy it. There are many plausible apocalypse scenarios that would wipe out most of humanity and make life miserable for a long time -- but finishing the job is a very different thing, and you have to reach deep into the scenario bag to find an apocalypse that actually does the trick. In contrast, there are a bunch of cellular biology innovations that sound magnificently tricky to evolve. Cellular membranes and the eukaryotic transition are two that stand out, but who knows. Point is: I find the "early filter" hypotheses easy to believe, and not just because they wind up being good news in the end.
  - tsimionescu 5y ago
    I agree with all or most of your comment. I wanted to comment a little bit on this though: > ["we really might be first"] plays into dangerous self-centered cognitive biases I'm not so sure that this bias exists to a great extent, and in fact an opposite bias seems to be to prevalent - in almost all art, there is always an assumption of some older more advanced progenitor race, some old golden age of advanced wisdom. This is true happens in the Epic of Gilgamesh (the antediluvian civilization was more advanced) just as in modern video games.
kokanee 5y ago
I don't think it's accurate to say that light is slow on any timescale. It's literally the fastest thing, no matter what scale you're on. The issue at hand, and the reason that we can make light look slow, is that we can't comprehend the distances we're talking about covering. No one said anything about restricting the search for life to our galaxy, so let's set that aside. Given the distances involved, the odds that evolution has gone complex in more than one galaxy are high, but the odds that we might find evidence of this are low.
- jjoonathan 5y ago
  Yes, it's true, to define a velocity scale you need to plug in a spatial scale and a temporal scale. A human lifetime defines the temporal scale, but I technically didn't mention a spatial scale. However, we were talking about Fermi paradox and galactic colonization -- so a reasonable spatial scale would be that of the galaxy, and then we have defined a velocity scale and can make comparisons: c << (galactic diameter / human lifetime) c >> (galactic diameter / billion year evolutionary lead)
- dhosek 5y ago
  The end of the gif with the distances between the sun, Mercury, Venus and Earth to scale is kind of informative and then you look at the fine print that indicates that with that scale the planets are all represented at 50x and the sun at 2x and it really makes the distances that much more amazingly large. And I have to confess that my mental image of the distance from Mercury to the sun was way off—I'd always envisioned it as being close enough that the sun would fill the daytime sky but really it would just look about 2.5–3 times bigger than it does on Earth.
jjk166 5y ago
But intelligent civilizations don't exist on evolutionary timescales, they exist on the timescales of intelligent beings, like us. We struggle to maintain projects for more than a few years, a tiny fraction of our lifetimes. Our oldest institutions are only a few thousand years old, dozens of generations. Many of our civilizations rose and fell within centuries. Our species is much less than a million years old, and while it is unclear how long we will last, it seems pretty optimistic to think we are in the first few percent of our species history, nonetheless the first few thousandths of a percent of our civilization's history. If we had built ships travelling at 1% of lightspeed to colonize the galaxy, and launched them when the common ancestor of humans and chimps lived, some of them would still be travelling to their destinations. Maybe there are rare species that live on timescales tens, hundreds, even thousands of times longer than ours, but even for them these would be long time periods. And it's not enough to simply reach these distant star systems, you need to survive there indefinitely. A billion years is a long time, much longer than complex life has existed on Earth. Most of Earth's crust is less than 250 million years old. Objects in space would be pulverized to dust by a billion years of collisions, assuming their orbits were even stable for anywhere near that long. On timescales like that, even structures made of solid granite would erode away on a planet's surface. Maybe by looking for weird minerals which couldn't have formed naturally or microfragments of broken down structures we could identify a civilization as having existed in the deep geologic past, but there is no way we could do that sort of analysis from light years away, even if we knew what to look for. Realistically, there are only a few technosignatures we could hope to find. Of course there are active radio transmissions, which requires the civilization to be active in an incredibly narrow timeframe. Exoplanet atmospheres containing short lived gases with no known natural production mechanism would be good, and may outlive a civilization, but anything stable enough to last for geologic timescales would be impossible to rule out as natural. Probably the longest lived evidence that we could detect would be the remnants of alien megastructures in space. No one really knows how long say a dyson sphere would last after it stops being maintained, maybe millions of years. But unless we make some extremely tenuous assumptions about what and how alien civilizations would construct megastructures, we can only make extremely rough guesses as to what a functional megastructure would look like, nonetheless one that has suffered millions of years of wear and tear. Of course eventually they'll all start to look like clouds of dust and debris, but how do we distinguish them from the clouds of dust and debris that we find all over the place with a presumed natural origin?