• Announcements

    • Robin

      Welcome!   03/05/2016

      Welcome, everyone, to the new 910CMX Community Forums. I'm still working on getting them running, so things may change.  If you're a 910 Comic creator and need your forum recreated, let me know and I'll get on it right away.  I'll do my best to make this new place as fun as the last one!
detrius

Story Wednesday, July 3rd, 2019

Recommended Posts

9 hours ago, Darth Fluffy said:
12 hours ago, hkmaly said:

I don't think anyone who actually UNDERSTANDS the physics thinks LHC is dangerous.

I kind of agree with you about your specific point, but there is an undercurrent of "We'd never do anything we knew was dangerous", and in a broader sense our track record says that we will do quite a bit without fully understanding what we're doing, particularly if the effects are long term and don't kill us right out immediately. Technically, you'd still be correct, we didn't know it was dangerous. Check out early use of x-ray devices (may need to find "fluoroscope"), early work in chemistry with radioactive elements, "Radium Girls" painting numbers on clocks with radium paint, and health effects on troops handling chemical weapons. LHC has never personally bothered me, and people do get worked up over nonsense, but on the other hand, our own ignorance combined with our inherent hubris tends to be deadly.

I meant dangerous to the planet - unlike that mentioned case with nuclear weapons, when we were building LHC all that talk about black holes were from people who don't really know how black holes work.

Yes, health effect of long-term radioactivity exposure were underestimated. Although the "Radium Girls" are bad example, as while the girls themselves were told it's harmless and that they should lick the brushes, the owners and scientist already used lead screens to protect themselves. Still, the inventor of radium dial paint himself died by it too, and THAT would probably count.

9 hours ago, Darth Fluffy said:
12 hours ago, hkmaly said:

Sure. They watched our TV.

"You mean the historical documents?" ...

"Surely, you don't believe Gilligan's Island is a ..."

"Those poor people!"

Those jokes aside, there are numerous better reasons than canceling their favorite show why some aliens might decide to wipe humanity due to our shows. Starting with, yes, not understanding that some of them are fictional, especially horrors and sci-fi. Or possibly knowing those are fictional but assuming there is more truth in them that really is.

Or they may be observing real documents about second world war and decide we are too aggressive ...

 

 

Share this post


Link to post
Share on other sites
On 7/12/2019 at 7:04 PM, hkmaly said:

Bottle it? You mean like using it to carbonate mineral water?

If you want to cool Venus down, you need to remove the greenhouse effect. To do that, you either blow the atmosphere off (not completely, you're not going to be that efficient anyway), or put it in containers, a little bit at a time, and move it. Think gas bottles, but larger; railroad cars designed to move gases, for example. Scale up from there. There could be chemical alternatives, that would require shipping a lot of material there.

999,999,999,999 bottles of SO2 in the air,

999,999,999,999 bottles of SO2,

Pick one up, ship it to Mars,

999,999,999,998 bottles of SO2 in the air.

 

 

Share this post


Link to post
Share on other sites
18 hours ago, hkmaly said:

Note that it's long drive either way ; I mean, conquering planet with intelligent life doesn't seem to be worth the effort for any rational reason, leaving just less rational reasons like preferring slaves to machines. It's much simpler to mine stuff on asteroids, and if you want habitable planet, it's better to choose one which is not already damaged even BEFORE you start the war to conquer it.

Pretty much. If they want to dominate us rather than kill us off, it's either because they like having other intelligent species subordinate to themselves, or because they think it's "for our own good" ("Little Green Man's Burden", or else because they want to spread their ideology/religion). If they want our planet but not us, then it's because they want something produced by our biosphere (exotic foods or spices or other chemicals). Anything inorganic can be easily found in a lifeless place without having to go to the bother of killing off the native life, unless they've got some extreme bias towards wanting to do their mining inside of a breathable atmosphere.

Share this post


Link to post
Share on other sites
15 hours ago, Don Edwards said:

Or maybe they like planets in the goldilocks zone, but can't stand that horrible oxygen stuff.

I prefer to think of it as The Three Bears zone, rather than the break-in and enter perp. Ya gotta have standards.

Share this post


Link to post
Share on other sites
19 hours ago, Darth Fluffy said:

Think gas bottles

... to my surprise, high-pressure gas cylinders are also called bottles.

16 hours ago, ijuin said:

If they want our planet but not us, then it's because they want something produced by our biosphere (exotic foods or spices or other chemicals).

While we don't have any statistical data confirming that, I find likely there are more planets with biosphere than planets with intelligent life. On the other hand, maybe they are harder to find without the so-called intelligent life broadcasting the location ...

 

Share this post


Link to post
Share on other sites
5 minutes ago, hkmaly said:

... to my surprise, high-pressure gas cylinders are also called bottles.

It's been years, but I've worked in places that had them, I've heard them called either.

I've used a few, but much smaller and more bottle-like.

Share this post


Link to post
Share on other sites
1 hour ago, hkmaly said:

While we don't have any statistical data confirming that, I find likely there are more planets with biosphere than planets with intelligent life. On the other hand, maybe they are harder to find without the so-called intelligent life broadcasting the location ..

I would consider this certain, on either or both of two reasons:

1) It's unlikely that every planet with a biosphere develops intelligent life.

2) Developing intelligent life sometimes, probably usually, takes a long time. In the extant sample, there's been a biosphere for probably close to 4 billion years and we currently believe it's had intelligent life for significantly less than a million years. So, at present, probably about 0.1% of the lifespan of the biosphere. Assuming nothing wipes us out or causes us to abandon the planet before the sun runs low on hydrogen and starts fusing helium (which will eventually cause it to swell and engulf the earth), that will rise to somewhere in the vicinity of 50%... after which the earth becomes distinctly uninteresting, unless we figure out a way to move it to a slower orbit.

Share this post


Link to post
Share on other sites
6 hours ago, hkmaly said:

While we don't have any statistical data confirming that, I find likely there are more planets with biosphere than planets with intelligent life. On the other hand, maybe they are harder to find without the so-called intelligent life broadcasting the location ...

Yes, but I was more referring to the aliens wanting things that are produced by species specific to our planet and not just any old biosphere--e.g. particularly tasty species. Spices were literally worth their weight in gold during the Age of Sail, for example. The Netherlands traded New Amsterdam (now New York) for one of the only places in the world where nutmeg would grow, and felt that they were getting the better half of the deal.

Share this post


Link to post
Share on other sites
4 hours ago, ijuin said:

The Netherlands traded New Amsterdam (now New York) for one of the only places in the world where nutmeg would grow, and felt that they were getting the better half of the deal.

Why they changed it?
I can't say.

Share this post


Link to post
Share on other sites
On 7/14/2019 at 8:05 AM, hkmaly said:

Or maybe most civilizations came to conclusion that experiments with creating a black hole on their home planet are safer than broadcasting their presence to universe.

Sure. They watched our TV.

Or maybe most species capable of intentionally broadcasting their presence aren't desperate enough to find other species to talk with to justify the expense of broadcasting long and loud enough to have much chance of anybody else hearing it... And those that have done so either are so far away that their signal still isn't strong enough for us to detect, or the timing of their civilization was/is wrong for us to detect them (either the civilization ended prior to the point where they would have to have sent the signal for us to hear it today, or the civilization is far enough away that the signal hasn't had time to reach us yet). ...It's worth noting that even on Earth finding the funding for such things is hard to come by, and we've mostly broadcasted for just a short time in a few directions we thought looked promising.

As for TV (and Radio, and other over-the-air transmissions), these are generally aimed towards the Earth, not into space, so they're not nearly as strong as signals actually aimed at other stars - and radio signals do get weaker as they travel (thanks to spreading out, as well as the occasional obstacle). There's also lots of sources of interference out there... From what I've heard, it would be extremely difficult (if not impossible) for aliens outside our solar system to make out such a faint signal. 

And even if aliens did detect TV and radio broadcasts, I would think all the different stations broadcasting at the same time (and not all on different frequencies, as we're talking about the whole world here) would make the signal a jumbled mess - I wonder if it would be possible for them to decipher it?

15 hours ago, Don Edwards said:

2) Developing intelligent life sometimes, probably usually, takes a long time. In the extant sample, there's been a biosphere for probably close to 4 billion years and we currently believe it's had intelligent life for significantly less than a million years. So, at present, probably about 0.1% of the lifespan of the biosphere. Assuming nothing wipes us out or causes us to abandon the planet before the sun runs low on hydrogen and starts fusing helium (which will eventually cause it to swell and engulf the earth), that will rise to somewhere in the vicinity of 50%... after which the earth becomes distinctly uninteresting, unless we figure out a way to move it to a slower orbit.

Actually, we probably will have to abandon the planet (or go through a monumental effort to keep the planet habitable) long before the Sun goes red giant; the Sun is increasing in luminosity over time, and in about 1 billion years it will become too hot for water to remain in liquid form on most of the Earth's surface. The most hardy life-forms might be able to last to 2.8 billion years from now on the surface and longer underground, but without advanced future technology human-descendants probably wouldn't be among them (and with advanced future technology it would probably be easier to move to another more habitable planet, like Mars).

So if we speculate that our descendants will make it to the 1 billion year mark, and depending on how long the biosphere survives, that would be 14% to 20% of its lifespan.

Share this post


Link to post
Share on other sites
On 7/16/2019 at 3:27 AM, Don Edwards said:
On 7/16/2019 at 1:49 AM, hkmaly said:

While we don't have any statistical data confirming that, I find likely there are more planets with biosphere than planets with intelligent life. On the other hand, maybe they are harder to find without the so-called intelligent life broadcasting the location ..

I would consider this certain, on either or both of two reasons:

1) It's unlikely that every planet with a biosphere develops intelligent life.

2) Developing intelligent life sometimes, probably usually, takes a long time. In the extant sample, there's been a biosphere for probably close to 4 billion years and we currently believe it's had intelligent life for significantly less than a million years. So, at present, probably about 0.1% of the lifespan of the biosphere.

While that makes sense, we have zero data for planets with biosphere without intelligent life and just single point for ones with one, so it's still just theory.

On 7/16/2019 at 3:27 AM, Don Edwards said:

Assuming nothing wipes us out or causes us to abandon the planet before the sun runs low on hydrogen and starts fusing helium (which will eventually cause it to swell and engulf the earth), that will rise to somewhere in the vicinity of 50%... after which the earth becomes distinctly uninteresting, unless we figure out a way to move it to a slower orbit.

Earth will became uncomfortable hot even before Sun starts fusing helium.

Slower? Putting Earth on slower orbit would make it even worse, unless you speak about angular speed.

8 hours ago, ChronosCat said:

Actually, we probably will have to abandon the planet (or go through a monumental effort to keep the planet habitable) long before the Sun goes red giant; the Sun is increasing in luminosity over time, and in about 1 billion years it will become too hot for water to remain in liquid form on most of the Earth's surface. The most hardy life-forms might be able to last to 2.8 billion years from now on the surface and longer underground, but without advanced future technology human-descendants probably wouldn't be among them (and with advanced future technology it would probably be easier to move to another more habitable planet, like Mars).

So if we speculate that our descendants will make it to the 1 billion year mark, and depending on how long the biosphere survives, that would be 14% to 20% of its lifespan.

Changing Earth's orbit or installing something like big solar glasses MIGHT be simpler than terraforming Mars.

And even with current technology, I think we would be able to survive underground quite long.

But on the other hand, NOONE was able to predict most of today's technology in 1800. Predicting what technology we will have after another billion years is funny. Technology in 2500 will already be completely unpredictable, and possibly based on string theory. Maybe at that point we will be colonizing other UNIVERSES.

18 hours ago, ijuin said:

Yes, but I was more referring to the aliens wanting things that are produced by species specific to our planet and not just any old biosphere--e.g. particularly tasty species. Spices were literally worth their weight in gold during the Age of Sail, for example. The Netherlands traded New Amsterdam (now New York) for one of the only places in the world where nutmeg would grow, and felt that they were getting the better half of the deal.

How would they find out about that? And wouldn't be better if they tried to trade for it instead of risking we find out what it is and destroys it during the war?

8 hours ago, ChronosCat said:

Or maybe most species capable of intentionally broadcasting their presence aren't desperate enough to find other species to talk with to justify the expense of broadcasting long and loud enough to have much chance of anybody else hearing it... And those that have done so either are so far away that their signal still isn't strong enough for us to detect, or the timing of their civilization was/is wrong for us to detect them (either the civilization ended prior to the point where they would have to have sent the signal for us to hear it today, or the civilization is far enough away that the signal hasn't had time to reach us yet). ...It's worth noting that even on Earth finding the funding for such things is hard to come by,

Oh, right: problems with funding are unlikely to be limited to our civilization :)

8 hours ago, ChronosCat said:

we've mostly broadcasted for just a short time in a few directions we thought looked promising.

As for TV (and Radio, and other over-the-air transmissions), these are generally aimed towards the Earth, not into space, so they're not nearly as strong as signals actually aimed at other stars - and radio signals do get weaker as they travel (thanks to spreading out, as well as the occasional obstacle). There's also lots of sources of interference out there... From what I've heard, it would be extremely difficult (if not impossible) for aliens outside our solar system to make out such a faint signal. 

Note that "broadcasting" usually means omnidirectional signal ... but yes, our deliberate-to-aliens signals are not omnidirectional.

I'm not sure about details, but somewhere I've read that on the radio wavelengths, Earth is actually more visible than Jupiter. That's obviously all our signals together, not single specific signal. And note that radio signals get weaker just as much as light, and we CAN see other stars.

8 hours ago, ChronosCat said:

And even if aliens did detect TV and radio broadcasts, I would think all the different stations broadcasting at the same time (and not all on different frequencies, as we're talking about the whole world here) would make the signal a jumbled mess - I wonder if it would be possible for them to decipher it?

Actually, even if they would catch just single signal, if that signal would be DVB-T2 multiplex, deciphering it would be quite a challenge. Back when we used analog, it was really possible to search for patterns and realize how the signal is used to produce image. But decoding H.265/MPEG-H HEVC without knowing anything about it? Good luck.

But speed of light is finite. It IS possible that just now, some aliens are watching the old analog signal from us which still CAN be decoded.

 

Share this post


Link to post
Share on other sites
3 hours ago, hkmaly said:

How would they find out about that? And wouldn't be better if they tried to trade for it instead of risking we find out what it is and destroys it during the war?

Yes, they would have to come and examine our native life to find out which species would be useful to them, but I was mainly positing it as a motive for why aliens would want specifically Earth rather than any random planet with advanced life--i.e. what do WE have that Rigel VII or Omicron Persei VIII does not?

24 minutes ago, Don Edwards said:

To have any chance at all of detecting our radio broadcasts, aliens have to be fairly close by...

they haven't gotten very far yet.

That explains nicely why no aliens would be aware of humanity's existence without coming here first. It does not however explain why, in the 250+ million years before humanity during which Earth has been uninhabited prime real estate free for the taking for anybody who likes Earth-like climates, nobody has decided to claim it and colonize it. Even without faster-than-light travel, a starfaring species should be able to occupy all compatible planets within the entire galaxy in only 10-20 million years.

Share this post


Link to post
Share on other sites
14 hours ago, hkmaly said:

Changing Earth's orbit or installing something like big solar glasses MIGHT be simpler than terraforming Mars.

And even with current technology, I think we would be able to survive underground quite long.

Early on, keeping the Earth cool would probably be easier than terraforming Mars. However, over time as the suns output increases, it will get harder to keep the Earth cool  and easier to terraform Mars (as Mars will get warmer too). I imagine there will come a tipping point where it's easier to just terraform Mars if it hasn't been done already, and the only reason for continuing to put the effort in to save Earth is sentimentality.

Moving the Earth would be such a massive undertaking I doubt it would be any easier than terraforming Mars. Particularly if we don't want to kill off what's left of the biosphere in the process.

As for surviving underground, there are only so many naturally occurring caves and most of them aren't appropriate for long-term human life, so we'd have to dig out new underground dwellings. We'd also need sources of food (underground farming?), water (aquifers might work at first, but my understanding is eventually most of the water makes its way to the surface and evaporates, so eventually you'd need a way to draw the water back out of the atmosphere and pump it back down to your dwellings), and breathable air (the farms might help with that). With current tech it might be possible for small numbers, but it would be expensive. With future tech it might be practical and worth the expense for large numbers, but I doubt there would be the resources to support billions of people underground, so if the population hasn't significantly dropped by then some people would probably still need to move off-world.

Although I've heard some of the details of Earth's future overheating before, at the moment I'm going by the wikipedia article "Future of Earth." While it mentions that life underground might be able to survive long after the surface is uninhabitable, it seems to forget about those underground life-forms after that, mostly treating the point the surface becomes uninhabitable as the point where life on Earth ends. It also doesn't speculate on how intelligent life might react to these changes. So I can't really say how long human-descendants would be able to survive underground. Perhaps we would be able to survive until the surface went molten (in which case human-descendants and the other life forms in our shelters might well be the last living things on Earth), but even that might be sooner than when the Sun goes Red Giant; in one scenario a runaway greenhouse effect 3 to 4 billion years from now could heat the planet up enough to melt the surface.

10 hours ago, ijuin said:

That explains nicely why no aliens would be aware of humanity's existence without coming here first. It does not however explain why, in the 250+ million years before humanity during which Earth has been uninhabited prime real estate free for the taking for anybody who likes Earth-like climates, nobody has decided to claim it and colonize it. Even without faster-than-light travel, a starfaring species should be able to occupy all compatible planets within the entire galaxy in only 10-20 million years.

Reaching close enough to light-speed to fully take advantage of time dilation would require incredible amounts of energy; for all but the most advanced civilizations it probably wouldn't be worth the cost. However, without time dilation interstellar journeys take an incredibly long time - many human lifetimes in most cases. The most obvious solutions to this are  sleeper ships, generation ships, or some form of immortality (including sentient machines). In the case of the generation ships and immortals, however, once you've been traveling the void of space for thousands or tens of thousands of years, why would you want to settle down when you found a planet? (And for a machine designed for space, Earth wouldn't even be any more appealing as a place to settle than a lifeless rock.) Chances are they'd have a look around, maybe replenish their resources (which in most cases could be done on uninhabited worlds as easily as inhabited ones), then continue their journey.

As for sleeper ships, maybe no successful interstellar civilizations in our galaxy have decided to go that route, maybe they don't interfere with existing biospheres for moral reasons, or maybe they just came through our neighborhood so long ago there's no trace of them anymore (there's no reason interstellar civilizations can't fall just like any other). This is a bit of a stretch, but maybe they settled on Earth hundreds of millions of years ago only for the colonists to be killed off in one of Earth's mass extinctions (obviously this would require them not leaving behind any fossils in places we've looked so far, but it's not like we're even close to knowing all the species that ever lived on Earth). Or maybe they came through so long ago Earth wasn't habitable yet (heck, maybe this was before the Sun formed).

It's also possible that the aliens that came through weren't the sort that would find Earth inhabitable. Or, (as with the machine intelligences I mentioned above), they might not find it any more habitable than any other rocky world that isn't so hot it would melt them.

Share this post


Link to post
Share on other sites
1 hour ago, ChronosCat said:

I imagine there will come a tipping point where it's easier to just terraform Mars if it hasn't been done already, and the only reason for continuing to put the effort in to save Earth is sentimentality.

This will come later than you think. It isn't just a matter of terraforming Mars, it's also a matter of building all the necessary housing, manufacturing capacity, etc.

And it's not as if we'll suddenly realize that we have to immediately start finding ways to deal with a much-hotter Earth. It'll be a gradual thing. No single generation will see a much-hotter Earth... each generation will see a very-slightly-hotter Earth. (Unless we build something like a planetary shade, and then after working for a while it breaks. Which isn't implausible.)

I still like the idea of moving the planet farther from the sun... the engineering of that task is left as an exercise for the reader. Or someone.

Share this post


Link to post
Share on other sites
4 hours ago, MSFrost said:

The sun, has no place in this discussion, what you purport, is incorrect.

When (and whether) the sun will render Earth inhospitable (by becoming a Red Giant or by other means) is entirely relevant to the discussion of how long intelligent life can survive on Earth (and by extension, how long alien races might be able to survive without moving to new planets). And to be clear, what exactly is it that you are claiming is incorrect, and do you have any sources for your claim?

3 hours ago, Don Edwards said:

This will come later than you think. It isn't just a matter of terraforming Mars, it's also a matter of building all the necessary housing, manufacturing capacity, etc.

According to the Wikipedia article on the future of the solar system about 1.5 billion years from now, Mars will warm enough for ice (both water and carbon dioxide) to melt on its surface, possibly leading to a greenhouse affect. Of course (based on what I can read of the source for that claim) it will be billions of years before Mars grows warm enough by natural means for life as we know it to survive there... But the combined efforts of both "humankind" (and I use the term loosely, I don't expect homo sapiens to still be around by then) and nature will surely be able to produce results faster and more easily than either working alone...

Of course, Wikipedia also claims that multi-cellular life on Earth will go extinct by 800 million years from now, and the oceans will likely boil away by 1.1 billion years from now, so it will require more than just the forces of evolution for our descendants to last long enough to see the point where rising temperatures make terraforming Mars significantly easier. (On the other hand, the article does go on to mention the possibility of the nitrogen cycle reducing atmospheric pressure enough to slow the rising temperatures, giving us until 2 billion years in the future before the oceans are lost, and presumably extending the reign of multi-cullular life as well.)

As for building housing and an industrial base on Mars, I would expect that could easily be done in a few centuries - and when dealing with a catastrophe that takes hundreds of millions of years (or even a couple billion) to reach it's conclusion, that's nothing.

...Then again, maybe we won't bother terraforming Mars at all. Maybe we'll just build enclosed bases/homes/cities/etc. there and call it good. If those of us with dreams of space have our way, we'll be building such things on Mars in the not-so-distant future anyway.

Share this post


Link to post
Share on other sites
21 hours ago, hkmaly said:

Slower? Putting Earth on slower orbit would make it even worse, unless you speak about angular speed.

I'm pretty sure he meant exactly that, further out.

But lets see, roughly 100 or so miles up, about an hour to orbit ~ 25,000 mph.

Geosync, around 27,000 miles up, ballpark 85,000 miles around, in 24 hours, yeah, you've actually slowed down as well. You've added energy, but your forward velocity is lower. And if you put on the brakes, so to speak, you'll speed up as you fall inward (while you are still orbiting).

 

39 minutes ago, ChronosCat said:

..."humankind" (and I use the term loosely, I don't expect homo sapiens to still be around by then) ...

Agree, evolution does not sit still; adapt or die. One scenario is, as we spread among the close stars, we become multiple competing species. Niven uses this in  A World Out of Time.

 

Share this post


Link to post
Share on other sites
28 minutes ago, Darth Fluffy said:

Agree, evolution does not sit still; adapt or die. One scenario is, as we spread among the close stars, we become multiple competing species. Niven uses this in  A World Out of Time.

The plausible outcomes:

1) We develop FTL, and our descendants - probably eventually evolving to something we wouldn't recognize as H. Sapiens Sapiens, but still our descendants and probably a single species (depending on just how much FTL the FTL is; 1.1C wouldn't help much; the Jenkinsverse works in kilolights and interstellar travel between places worth going to still routinely takes weeks or months) - spread to the stars.

2) We develop high-energy drive systems, but not FTL, and our descendants spread to the stars and evolve into multiple species. And perhaps we also save the Earth - or Mars, or both - from incineration...

3) We die with the Earth, if not before.

Share this post


Link to post
Share on other sites
8 hours ago, ChronosCat said:

As for surviving underground, there are only so many naturally occurring caves and most of them aren't appropriate for long-term human life, so we'd have to dig out new underground dwellings. We'd also need sources of food (underground farming?), water (aquifers might work at first, but my understanding is eventually most of the water makes its way to the surface and evaporates, so eventually you'd need a way to draw the water back out of the atmosphere and pump it back down to your dwellings), and breathable air (the farms might help with that). With current tech it might be possible for small numbers, but it would be expensive. With future tech it might be practical and worth the expense for large numbers, but I doubt there would be the resources to support billions of people underground, so if the population hasn't significantly dropped by then some people would probably still need to move off-world.

You have the cause and effect backwards. Yes, there would be limited space underground, so if the rest of people won't manage to move off-world, they would die ... which is the population drop you mentioned.

8 hours ago, ChronosCat said:

Reaching close enough to light-speed to fully take advantage of time dilation would require incredible amounts of energy; for all but the most advanced civilizations it probably wouldn't be worth the cost. However, without time dilation interstellar journeys take an incredibly long time - many human lifetimes in most cases. The most obvious solutions to this are  sleeper ships, generation ships, or some form of immortality (including sentient machines). In the case of the generation ships and immortals, however, once you've been traveling the void of space for thousands or tens of thousands of years, why would you want to settle down when you found a planet? (And for a machine designed for space, Earth wouldn't even be any more appealing as a place to settle than a lifeless rock.) Chances are they'd have a look around, maybe replenish their resources (which in most cases could be done on uninhabited worlds as easily as inhabited ones), then continue their journey.

It is possible that even after those tens of thousands of years, the population of that generation ship would want to expand. Planet offers much more space than ship, even if they would try to build more ships. But yes, it's hard to predict what will that time do to their psychology ; perhaps they wouldn't be able to live on planet anymore.

8 hours ago, ChronosCat said:

This is a bit of a stretch, but maybe they settled on Earth hundreds of millions of years ago only for the colonists to be killed off in one of Earth's mass extinctions (obviously this would require them not leaving behind any fossils in places we've looked so far, but it's not like we're even close to knowing all the species that ever lived on Earth). Or maybe they came through so long ago Earth wasn't habitable yet (heck, maybe this was before the Sun formed).

Note that while we may not be first civilization in galaxy, we are not that slow either ; inhabitable planets require heavy elements which needs to be produced by supernovae first, and evolution is not that fast either ... meaning, it's entirely possible there were NO intelligent civilizations millions of years ago.

8 hours ago, ChronosCat said:

I imagine there will come a tipping point where it's easier to just terraform Mars if it hasn't been done already, and the only reason for continuing to put the effort in to save Earth is sentimentality.

Sentimentality is VERY strong motivation.

40 minutes ago, Darth Fluffy said:
22 hours ago, hkmaly said:

Slower? Putting Earth on slower orbit would make it even worse, unless you speak about angular speed.

I'm pretty sure he meant exactly that, further out.

But lets see, roughly 100 or so miles up, about an hour to orbit ~ 25,000 mph.

Geosync, around 27,000 miles up, ballpark 85,000 miles around, in 24 hours, yeah, you've actually slowed down as well. You've added energy, but your forward velocity is lower. And if you put on the brakes, so to speak, you'll speed up as you fall inward (while you are still orbiting).

.... right. Geostationary orbit is about 24h at distance of 42,000 km, moon orbits at about 380,000km and it takes it 27 days, so it's about three times slower. My bad.

16 minutes ago, Don Edwards said:
48 minutes ago, Darth Fluffy said:

Agree, evolution does not sit still; adapt or die. One scenario is, as we spread among the close stars, we become multiple competing species. Niven uses this in  A World Out of Time.

The plausible outcomes:

1) We develop FTL, and our descendants - probably eventually evolving to something we wouldn't recognize as H. Sapiens Sapiens, but still our descendants and probably a single species (depending on just how much FTL the FTL is; 1.1C wouldn't help much; the Jenkinsverse works in kilolights and interstellar travel between places worth going to still routinely takes weeks or months) - spread to the stars.

2) We develop high-energy drive systems, but not FTL, and our descendants spread to the stars and evolve into multiple species. And perhaps we also save the Earth - or Mars, or both - from incineration...

3) We die with the Earth, if not before.

It's true that spreading to stars without FTL will force us to evolve into multiple species, but we can still evolve into multiple species WITH FTL if we choose so.

And there is definitely option of surviving inside solar system without the ability to leave it - we may lose Earth, but there will always be option to live in space stations, small enough to be kept in habitable zone.

Share this post


Link to post
Share on other sites
7 hours ago, hkmaly said:

... FTL ...

Maybe we'll find a loophole, but basic physics says, "Don't get your hopes up."

Flip side, it has been pointed out the fundamental argument for why c is the speed limit have to do with avoiding cause and effect contradictions. As long as you are willing to toss the even more fundamental notion of causality, there is no reason c has to be the speed limit, for information at least.

 

 

Share this post


Link to post
Share on other sites

The danger in causality is not because of problems with effects preceding their causes, so much as it is the possibility of the Grandfather Paradox. What is so paradoxical is not that you kill your own grandfather, but rather that thus preventing your own birth seems to mean that you could not have been there to kill him in the first place, leading to the apparent contradiction of “you did” and “you didn’t” being simultaneously true—an apparently unresolvable superposition that makes Schroedinger’s cat look look like child’s play. If killing your grandfather merely erased you from history yet allowed his death to happen even without you existing, then there would be no paradox.

Share this post


Link to post
Share on other sites
13 hours ago, Darth Fluffy said:
21 hours ago, hkmaly said:

... FTL ...

Maybe we'll find a loophole, but basic physics says, "Don't get your hopes up."

Advanced physics says wormholes are possible. The classical "flying in real space just fast" not, of course ... except in case of warp which is also complicated.

As a bonus, if you create a wormhole, then take one end on circular tour with relativistic speed, when you return, you WILL have a time machine allowing you to send stuff into past (but not before creating the wormhole obviously). See Xeelee Sequence by Stephen Baxter.

13 hours ago, Darth Fluffy said:

Flip side, it has been pointed out the fundamental argument for why c is the speed limit have to do with avoiding cause and effect contradictions. As long as you are willing to toss the even more fundamental notion of causality, there is no reason c has to be the speed limit, for information at least.

3 hours ago, ijuin said:

The danger in causality is not because of problems with effects preceding their causes, so much as it is the possibility of the Grandfather Paradox. What is so paradoxical is not that you kill your own grandfather, but rather that thus preventing your own birth seems to mean that you could not have been there to kill him in the first place, leading to the apparent contradiction of “you did” and “you didn’t” being simultaneously true—an apparently unresolvable superposition that makes Schroedinger’s cat look look like child’s play. If killing your grandfather merely erased you from history yet allowed his death to happen even without you existing, then there would be no paradox.

Thing is that in quantum physics, causality ALREADY doesn't work how would you expect. Electron can interfere with itself. Grandfather paradox is obviously impossible, but that doesn't mean time travel is - it just means that when the waveform collapses, every effect will have it's cause.

Of course, we still need exotic matter to create the wormholes (which may not exists). Also, our understanding of universe is incomplete. For example naked singularity: both quantum physics and theory of relativity give totally absurd prediction about what would happen around naked singularity ... and those predictions are DIFFERENT.

Share this post


Link to post
Share on other sites
1 hour ago, hkmaly said:

Advanced physics says wormholes are possible. The classical "flying in real space just fast" not, of course ... except in case of warp which is also complicated.

Yes, and going where and when you don't know, and classically also tiny, you might send a signal through, but probably not a hamster.

 

1 hour ago, hkmaly said:

As a bonus, if you create a wormhole, then take one end on circular tour with relativistic speed, when you return, you WILL have a time machine allowing you to send stuff into past (but not before creating the wormhole obviously). See Xeelee Sequence by Stephen Baxter.

Sure, sure, we have a plan, trivially easy, we leave it as an exercise for the students, who hopefully have exotic matter to keep it open ...

 

1 hour ago, hkmaly said:

Thing is that in quantum physics, causality ALREADY doesn't work how would you expect. Electron can interfere with itself. Grandfather paradox is obviously impossible, but that doesn't mean time travel is - it just means that when the waveform collapses, every effect will have it's cause.

At a quantum level, sure. A positron might be an electron moving back in time, it would look the same; entropy barely holds with very small numbers and quantities. But scale it up, and it falls apart quickly.

 

1 hour ago, hkmaly said:

Of course, we still need exotic matter to create the wormholes (which may not exists). Also, our understanding of universe is incomplete. For example naked singularity: both quantum physics and theory of relativity give totally absurd prediction about what would happen around naked singularity ... and those predictions are DIFFERENT.

Something other than normal "stuff" is filling up most of the universe.

Not sure about black hole nudity. It's based on spin, and I don't get why starting with the angular momentum of a star, as the object collapses to zero size, the rotational speed should be effectively infinite to maintain that angular momentum (think skater bringing their arms in), but apparently that's not the case. (Still, I would be really surprised if someone discovered a singularity of significant size that was not spinning.) Never been observed, yet, but that doesn't mean they're not out there.

 

New topic

My theory is time travel is easy, but every timeline that discovers it is inherently unstable, so only the ones where it's never discovered remain.

 

 

Share this post


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