# Is the universe old or young? **URL:** \ **Category:** Great Debates\ **Created:** [April 23, 2022, 10:17pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334 "2022-04-23T22:17:54Z")\ **Posts on this page:** 20\ **Page:** 6
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [April 30, 2022, 6:37pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/101 "2022-04-30T18:37:09Z")
> [@EllisDee](#): > > Alternately, if we travel at conventional speeds in self-contained arks, we could make it to the closest stars. Not only the closest stars. And not only arks. > [@EllisDee](#): > > But my point here is that we would not then be an analog for the alien races we should be seeing. In other words, we did not progress that eye blink in this hypothetical. This is exactly what kind of thing my “eyeblink” alluded to, but I think I get what you’re saying. I think you’re saying that colonies spreading by generation starship would not be detectable. Maybe generation starships (and colonies) are all over the Galaxy and we can’t see them yet. But… It again has an issue with the replicating probes. If (multiple) species can build ships capable of ferrying whole communities around, the sending thousands of probes, or self replicating probes, is childs play. Why do we not see any? ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [April 30, 2022, 6:38pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/102 "2022-04-30T18:38:28Z")
> [@EllisDee](#): > > We should see aliens because we’re an eyeblink away from getting to the stars ourselves, so they should be too, or already did so long ago. Depends on what you mean by eyeblink. We are talking in cosmological scales, where an eyeblink is a million years. > [@EllisDee](#): > > I say we’re not an eyeblink away, we’re infinitely far because at this point our only solution to the light speed problem is essentially magic. Except, as explained, it doesn’t require going faster than the speed of light. > [@EllisDee](#): > > Alternately, if we travel at conventional speeds in self-contained arks, we could make it to the closest stars. But my point here is that we would not then be an analog for the alien races we should be seeing. We are not seeing _any_ is the problem here. > [@EllisDee](#): > > We should not be obviously detectable in this hypothetical. So if that’s really how it works, why should we see aliens? If an asteroid world ship pulled into our solar system and started dismantling the planets for materials, we would most likely be able to detect that. > [@EllisDee](#): > > My main point is that there’s probably hundreds of civilizations thousands of light years away, and they can’t see us and we can’t see them and never the twain shall meet because light speed is the great filter. Light speed is not the great filter if it doesn’t prevent us from expanding out into the galaxy, and there is no reason why it _has_ to be done at such a high speed. We could take our time, move at .1% the speed of light, and have the entire galaxy filled up in a few hundred million years. ---
**Author:** ![Jackknifed\_Juggernaut](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@Jackknifed\_Juggernaut](https://boards.straightdope.com/u/Jackknifed_Juggernaut)\ **Post date:** [April 30, 2022, 6:39pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/103 "2022-04-30T18:39:02Z")
Are the plethora of challenges of reaching other habitable planets less complex than simply building a new planet in a desired location? Perhaps super-intelligent species just build their own, and thus have no reason to travel great distances? ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [April 30, 2022, 6:39pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/104 "2022-04-30T18:39:24Z")
> [@Jackknifed\_Juggernaut](#): > > Are the plethora of challenges of reaching other habitable planets Habitable planets don’t matter here. They will be extremely rare, if they exist at all. What civs would be going for is just the raw resources contained outside of their solar system. > [@Jackknifed\_Juggernaut](#): > > Perhaps super-intelligent species just build their own, and thus have no reason to travel great distances? Out of what? ---
**Author:** ![Babale](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/babale/32/15666_2.png) [@Babale](https://boards.straightdope.com/u/Babale)\ **Post date:** [April 30, 2022, 6:40pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/105 "2022-04-30T18:40:03Z")
> [@EllisDee](#): > > We should see aliens because we’re an eyeblink away from getting to the stars ourselves, so they should be too, or already did so long ago. > > I say we’re not an eyeblink away, we’re infinitely far because at this point our only solution to the light speed problem is essentially magic. > > Alternately, if we travel at conventional speeds in self-contained arks, we could make it to the closest stars. But my point here is that we would not then be an analog for the alien races we should be seeing. In other words, we did not progress that eye blink in this hypothetical. We should not be obviously detectable in this hypothetical. So if that’s really how it works, why should we see aliens? > > My main point is that there’s probably hundreds of civilizations thousands of light years away, and they can’t see us and we can’t see them and never the twain shall meet because light speed is the great filter. And that’s why we don’t see them. The problem is that if given, say, a million years, we probably WOULD have done all these things. Now, life could have probably existed in our universe billions of years before it started on earth, but let’s be generous and say life could not have evolved anywhere until it did on Earth. Well, here on Earth, once multicellular life evolved, we ended up with a familiar pattern - ecosystems diversify and life becomes varied and widespread; mass extinctions destroy most of that variety; the survivors rediversify into new complex ecosystems. The main cycle we evolved in started when the dinosaurs died out 65 million years ago; since then, despite ups and downs, the land has mostly been dominated by mammals. The cycle before that started around 251 million years ago, and was dominated by reptiles. At no point during that time did intligent life arise. But that was just luck. Imagine another world where life evlolved around the same time as us. Intelligent life couls just as easily evolved in an earlier cycle (just as it could have never arisen until life on the planet ended completely). If these aliens had a million year head start on us - much less 65 million - they’d have had eons to colonize the stars ---
**Author:** ![Jackknifed\_Juggernaut](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@Jackknifed\_Juggernaut](https://boards.straightdope.com/u/Jackknifed_Juggernaut)\ **Post date:** [April 30, 2022, 6:40pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/106 "2022-04-30T18:40:12Z")
Stuff from planets, moons, etc. close by? ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [April 30, 2022, 6:41pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/107 "2022-04-30T18:41:19Z")
And what happens when they run out of nearby materials? Do they just stop existing, or do they go further out for more? ---
**Author:** ![Jackknifed\_Juggernaut](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@Jackknifed\_Juggernaut](https://boards.straightdope.com/u/Jackknifed_Juggernaut)\ **Post date:** [April 30, 2022, 6:44pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/108 "2022-04-30T18:44:40Z")
Why would they run out of materials? Matter doesn’t disappear, does it? Perhaps if they are adding net population, then they would need more stuff. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [April 30, 2022, 6:47pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/109 "2022-04-30T18:47:27Z")
> [@Jackknifed\_Juggernaut](#): > > Perhaps super-intelligent species just build their own, and thus have no reason to travel great distances? But once again, for the Fermi paradox it is not enough to posit that a species has good reason to do something other than interstellar travel (and other than anything else detectable, like a big ass laser light show). We need those things to basically be out of reach. Because if 9/10 species decide to only build planets, but 1/10 has _one faction_ that decides to launch probes, or just be noisy, that could leave evidence across the galaxy and/or within our own star system. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [April 30, 2022, 6:50pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/110 "2022-04-30T18:50:59Z")
> [@Jackknifed\_Juggernaut](#): > > Matter doesn’t disappear, does it? When you turn it into energy, it does. Do you think the stars will last forever? What will fuel this civilization? > [@Jackknifed\_Juggernaut](#): > > Perhaps if they are adding net population, then they would need more stuff. And why wouldn’t they be adding to net population? Keep in mind, your answer has to explain why _no_ alien species, at all, ever in the history of the universe, is expansionistic. ---
**Author:** ![EllisDee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ellisdee/32/4531_2.png) [@EllisDee](https://boards.straightdope.com/u/EllisDee)\ **Post date:** [April 30, 2022, 7:01pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/111 "2022-04-30T19:01:48Z")
Forgive these unwieldy posts, this thread is moving so fast…(so fun!) > [@Mijin](#): > > that could leave evidence across the galaxy and/or within our own star system Okay I think here’s my disconnect. Somebody else said something similar about would we notice when they entered our star system or something. In my mind, space is very big. The reason they haven’t been here is because we’re one of 100 billion stars in the Milky Way galaxy. Statistically speaking, it’s unlikely they would ever come to our particular star or even look at it. Right now on earth, what percentage of land is dark at night? The unpopulated part? Maybe our star system just happens to be in the equivalent of the middle of Wyoming, while the rest of the galaxy is lit up like the rest of the earth is at night. I guess the response would be we would see that, but would we for sure? I’m asking; I don’t know. > [@k9bfriender](#): > > Habitable planets don’t matter here. They will be extremely rare, if they exist at all. What civs would be going for is just the raw resources contained outside of their solar system. That doesn’t sound like a civilization we would have any particular reason to be able to detect, though. > [@k9bfriender](#): > > Light speed is not the great filter if it doesn’t prevent us from expanding out into the galaxy, and there is no reason why it _has_ to be done at such a high speed. We could take our time, move at .1% the speed of light, and have the entire galaxy filled up in a few hundred million years. That doesn’t sound right to me. Google says the radius of the Milky Way galaxy is 50,000 light years. At 1/1000th the speed of light it would take us 50 million years just to go halfway across the galaxy without stopping to colonize anywhere else along the way. Surely each of those colonizations take several hundred years before they are ready to send out more colonizations. Does the math check out? What if there are actually around 2,000 interstellar civilizations, but they all started out within the last hundred million years. I say the galaxy is big enough that they could have all still never run across any of the others in this conventional speed strip mining model. > [@Babale](#): > > The cycle before that started around 251 million years ago, and was dominated by reptiles. At no point during that time did intligent life arise. > > But that was just luck. Aside: Was that just luck? For some reason I seem to think that reptile physiology wouldn’t be able to sustain a large brain. Something about regulating body temperature. Do I have that wrong? Could a cold-blooded creature theoretically have a large brain? Actually, are octopus cold-blooded? ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [April 30, 2022, 7:03pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/112 "2022-04-30T19:03:31Z")
It’s interesting that whenever the Fermi paradox comes up on SD, or forums like it, by far the most popular explanations are psychological: Perhaps ETs are out there, and have the means to explore or leave evidence, but just choose not to… How can we be so arrogant as to guess what they would do? But such propositions are very much at the back of the list among astrophysicists and astrobiologists. For the reason that I said: that psychological explanations require _every_ individual of _every_ civilization of _every_ species to _always_ come to the same conclusion, for billions of years. Given the variety of behavior we see among the one sentient species we know of, this looks like quite a stretch. ---
**Author:** ![EllisDee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ellisdee/32/4531_2.png) [@EllisDee](https://boards.straightdope.com/u/EllisDee)\ **Post date:** [April 30, 2022, 7:05pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/113 "2022-04-30T19:05:10Z")
My explanation isn’t psychological. My explanation is essentially “big sky” theory writ large. > **[Big sky theory](https://en.wikipedia.org/wiki/Big_sky_theory)** > > In aviation, the Big Sky Theory is that two randomly flying bodies are very unlikely to collide, as the three-dimensional space is so large relative to the bodies. Some aviation safety rules involving altimetry and navigation standards are based on this concept. It does not apply when aircraft are flying along specific narrow routes, such as an airport traffic pattern or jet airway. > The Big Sky Theory has been mathematically modeled, using a gas law approach. This implies that collisions of airc... ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [April 30, 2022, 7:08pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/114 "2022-04-30T19:08:48Z")
> [@EllisDee](#): > > Maybe our star system just happens to be in the equivalent of the middle of Wyoming, while the rest of the galaxy is lit up like the rest of the earth is at night. Ok but if you’re in Wyoming you can _detect_ that life exists elsewhere 🙂 Also, again it’s not about a species pointing to a map of the Galaxy and singling out our star as their destination. It’s about the various ways a species could spread around to billions of systems and/or leave detectable signals. ---
**Author:** ![EllisDee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ellisdee/32/4531_2.png) [@EllisDee](https://boards.straightdope.com/u/EllisDee)\ **Post date:** [April 30, 2022, 7:10pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/115 "2022-04-30T19:10:48Z")
But what are the detectable signals we should be seeing in any of these hypothetical examples? If they’re not colonizing planets, what should we be seeing? In any example of us expanding to billions of stars, would we be easily detectable to every single star in the galaxy? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 30, 2022, 7:14pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/116 "2022-04-30T19:14:51Z")
Unless aliens solve the light speed problem they’d have to be close by. They would have had to detect us long enough ago through radio noise to have an expedition heading in our direction, or else heading here by random chance. And even if we are detected it will be a long time until they get here, and unless the mission includes aliens and is not just a machine then it may be a long time until the aliens find out about us back on their home world. So no light speed travel and we’re not likely to meet any aliens anytime soon. But the odds improve over time. Eventually there should be a lot of technologically advanced aliens and eventually we and some aliens will run across each other. As long as we don’t wipe ourselves out anyway. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [April 30, 2022, 7:17pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/117 "2022-04-30T19:17:44Z")
That was quite a popular explanation for the Fermi ‘paradox’ at one time; there are hundreds of billions of stars in our galaxy alone, so why would they come here? In 1980, Frank Tipler suggested that a civilisation could launch a relatively small number of self-replicating probes, and thereby explore every system in the galaxy within the space of a few million years, so the question now becomes ‘why have they not launched self-replicating probes?’ ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [April 30, 2022, 7:22pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/118 "2022-04-30T19:22:39Z")
> [@EllisDee](#): > > The reason they haven’t been here is because we’re one of 100 billion stars in the Milky Way galaxy. Statistically speaking, it’s unlikely they would ever come to our particular star or even look at it. Statistically speaking, it’s extremely unlikely that a particular worm will crawl under the rock in your front yard, and yet, if you pick up the rock, there’s a worm. We are not talking about an individual coming over to visit, we are talking about a growth curve of an entire species. > [@EllisDee](#): > > Right now on earth, what percentage of land is dark at night? The unpopulated part? Maybe our star system just happens to be in the equivalent of the middle of Wyoming, while the rest of the galaxy is lit up like the rest of the earth is at night. If you look at it that way, it’s the other way around, as our star is larger and brighter than the vast majority of stars out there. But, once again, look under a rock in Wyoming, see those worms there? They didn’t crawl all the way from Ohio. > [@EllisDee](#): > > I guess the response would be we would see that, but would we for sure? If other civs were out there stellarforming, putting up dyson spheres, and lifting the materials out of the stars, we would see that, for sure. > [@EllisDee](#): > > That doesn’t sound like a civilization we would have any particular reason to be able to detect, though. Easy enough to detect when they land on Earth and start taking it apart and shipping the resources back home. Or even the moon, a planet or an asteroid. What is _so_ special about our solar system that wards them off entirely? > [@EllisDee](#): > > Google says the radius of the Milky Way galaxy is 50,000 light years. At 1/1000th the speed of light it would take us 50 million years just to go halfway across the galaxy without stopping to colonize anywhere else along the way. Surely each of those colonizations take several hundred years before they are ready to send out more colonizations. Does the math check out? Sure, for a couple reasons. One is that I used those same numbers and math to come to a few hundred million year timescale. And why do you think that everyone will stop at every star system? If you have dandelions in your yard, they don’t invade your neighbor’s yard, then go from there to _their_ neighbor’s yard, one at a time. The dandelion seeds get blown all over the neighborhood. If you set out from Earth to colonize another system, why would you go to the next one over, when you know that there are already others going there? You don’t, you go on to the next. If you are part of a interstellar colony, and your faction decides to move on, you aren’t going to just hit the next star over, it’s probably already inhabited. You are going to push on past a number of them to get to one that is unclaimed. > [@EllisDee](#): > > What if there are actually around 2,000 interstellar civilizations, but they all started out within the last hundred million years. Why do you think that for the first 13.6 billion years, there was nothing, and then all of a sudden in the last .1 all these civs came up at once? > [@EllisDee](#): > > I say the galaxy is big enough that they could have all still never run across any of the others in this conventional speed strip mining model. And I’ve shown the math that says that we would. Not only would we see them in our back yard, but we would also see as they dismantle solar systems over a thousand light years away. ---
**Author:** ![EllisDee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ellisdee/32/4531_2.png) [@EllisDee](https://boards.straightdope.com/u/EllisDee)\ **Post date:** [April 30, 2022, 7:23pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/119 "2022-04-30T19:23:33Z")
> [@eburacum45](#): > > In 1980, Frank Tipler suggested that a civilisation could launch a relatively small number of self-replicating probes, and thereby explore every system in the galaxy within the space of a few million years, so the question now becomes ‘why have they not launched self-replicating probes?’ For the same reason we haven’t and likely won’t, is my guess: Without a solution to the light speed problem, there is no point. I really don’t see humans doing one-way expansion. That’s not really our bag. When we discover new worlds, the point is to connect them to our existing world, to make the world bigger. That’s what I think of as the human drive. Sending an ark 4 light years away (the closest!) means writing off everyone and everything on the ark, and for those on the ark, writing off everyone and everything back home. Forever. I don’t think it’s in the human psyche to do something like that. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [April 30, 2022, 7:26pm UTC](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334/120 "2022-04-30T19:26:04Z")
> [@EllisDee](#): > > But what are the detectable signals we should be seeing in any of these hypothetical examples? If they’re not colonizing planets, what should we be seeing? Who knows? Again, I’m not positing any particular behavior of aliens, the critical thing is just what technology is at their disposal and the likely cost of said technologies. For example, let’s say we discover a massive helical structure, radiating a complex pattern of gamma waves. We’d absolutely consider this potential evidence of ETs even while having no clue whatsoever of what such a structure is for. However, we see no such helices. We see nothing at all in fact. No deliberate signals, no incidental ones either. [Previous page](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334.md?page=5) [Next page](https://boards.straightdope.com/t/is-the-universe-old-or-young/963334.md?page=7)