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If we wish to colonize another world, finding a planet with a gravitational field that humans can survive and thrive under will be crucial. If its gravity is too strong our blood will be pulled down into our legs, our bones might break, and we could even be pinned helplessly to the ground.
Finding the gravitational limit of the human body is something that's better done before we land on a massive new planet. Now, in a paper published on the pre-print server arXiv, three physicists, claim that the maximum gravitational field humans could survive long-term is four-and-a-half times the gravity on Earth.
Or, at least you could if you are an Icelandic strongman – and Game of Thrones monster – who can walk with more than half a metric ton on your back. For mere mortals, the researchers say, it would need to be a little weaker.
[...] For the maximum gravity at which we could take a step, the team turned to Hafþór Júlíus Björnsson, an Icelandic strongman who once walked five steps with a 1430 pound log on his back, smashing a 1,000-year-old record[*].
[*] YouTube video.
What's the Maximum Gravity We Could Survive?
(Score: 2) by Arik on Tuesday September 25 2018, @04:31AM (8 children)
Arrival within decades was not one of the specified parameters, you can't just tack on extra requirements afterwards.
"Probably not even in centuries."
No, definitely within centuries. With 1970s tech, it would be ~300 years to Alpha Centauri. If the project had been funded and planned back then, likely improvements available before completion would have reduced it to ~100 years, possibly even less.
"Nor do we have a good enough understanding of managing a closed ecosystem to keep the colonists and their ecosystem alive for hundreds, maybe thousands of years between stars with no possibility of getting any additional supplies. "
To the degree that's true it's simply because we have NOT been working on a project where we would have gained that experience.
If laughter is the best medicine, who are the best doctors?
(Score: 2) by Immerman on Tuesday September 25 2018, @02:08PM (7 children)
My point was that we don't have the technology to keep people alive for the duration of the voyage. Not today, and definitely not in the 70s.
And sure, *if* we had started seriously developing the technology in the 70s, *maybe* we'd have it ready today. But that dioesn't change the fact that the technology doesn't yet exist, and thus we couldn't then, and still can't today, establish an interstellar colony. Rocketry is the easy part.
(Score: 2) by Arik on Tuesday September 25 2018, @02:29PM (6 children)
I guess that's a fundamental disagreement then. I think you're simply wrong. We knew how to do it then and we certainly know how to do it now. ANY time you do something new of course there are things you will only learn by doing, so you can ALWAYS say that you lack the technology to do ANYTHING new by that standard.
If that's your standard then by that standard you're right, I just don't think it's a useful standard.
If laughter is the best medicine, who are the best doctors?
(Score: 2) by Immerman on Tuesday September 25 2018, @11:37PM (4 children)
No, we *don't* know how to do it now. When it comes to managing complex closed ecosystems all we have is theory, and even that still has serious known gaps in it - and who knows how many unknown ones. As the saying goes "In theory there's no difference between theory and practice. In practice there is." Technology is what you get after you've distilled theory to practice.
The few attempts we've made at managing closed ecosystems have ended badly within a couple years. Had we launched a colony ship in the 70s it wouldn't have exited the solar system yet, and the colonists would likely already mostly be dead.
(Score: 1) by Arik on Wednesday September 26 2018, @01:28AM (3 children)
Again, with our actual timeline of technology, we could easily have 40 years of experience with long-term space habitations, more than enough time to work out the details of engineering and practice that are always lacking when you start to apply a new technology.
I didn't suggest launching an interstellar colony ship in the 70s, I suggested *planning* and *commencing* the project to produce it as early as that decade.
That's not something you just do in one stage. First you need HOMEs, and then... well it doesn't matter. We still haven't gotten to step 1, but not because we lacked any essential technology.
If laughter is the best medicine, who are the best doctors?
(Score: 2) by Immerman on Wednesday September 26 2018, @02:08PM (2 children)
I think we have a disagreement over what the word technology means. I say it's not just the hardware - you're right that we had the necessary hardware. It's *also* the practical knowledge (both beyond and preceding theory) on how to do a thing. Democracy is a social technology. Irrigation is an agricultural technology. Managing a closed ecosystem is a bio-ecological technology - one that we don't have, and that we'd need a lot of practice to develop.
We absolutely could have started building space habitats in the 70s if we had the will. But there's a lot of decades developing ecological technologies, not to mention orbital manufacturing technologies, before we would be anywhere close to ready to start building an interstellar ark.
(Score: 2) by Arik on Wednesday September 26 2018, @02:50PM (1 child)
To me, we had the tech - we had all the necessary pieces to get it going. The stuff you're talking about, the experience, well the only way you get that is by doing. And we just haven't been doing.
"We absolutely could have started building space habitats in the 70s if we had the will. But there's a lot of decades developing ecological technologies, not to mention orbital manufacturing technologies, before we would be anywhere close to ready to start building an interstellar ark."
Only way to know would be to go, but I suspect "decades" might even be an exaggeration. For sure, though, it's a stage that we could have passed by now, but one we still have to start at this point.
If laughter is the best medicine, who are the best doctors?
(Score: 2) by Immerman on Thursday September 27 2018, @03:19AM
The Wright brothers had all the necessary pieces to build an aircraft - but you wouldn't want to try to cross the Atlantic in the plane they first flew from Kitty Hawk. You need some steps in between to work the inevitable kinks out of the system, optimize, etc. They didn't have the tech for the job - they only had the beginnings of the tech, it took another 25 years to develop it to the point where someone managed to cross the Atlantic.
I think you're grossly underestimating the complexity of managing a closed ecology complex enough to support us. I don't forsee any serious problems in building off-world ecologies. A rough start for sure, but I don't think there'll be any insurmountable problems, primarily because they'll have relatively easy access to whatever ecological supplements they discover they need (mineral and/or biological). However, I don't think we will have even discovered all the problems, much less solved them, in only a few decades. And I doubt anyone will even be seriously *thinking* about closed ecologies - they'll be importing resources at a breakneck speed as they grow.
An interstellar voyage is just far too expensive to even consider launching before you've got every last detail hammered out. Just the raw kinetic energy required is E= 1/2*m*(10%*300,000,000m/s)^2 = 4.5x10^14J/kg = 125GWh/kg. For an 80kg average American, that's about 10TWh of kinetic energy in their body - without any supporting ship, or any losses to the hideous inefficiencies of existing propulsion systems. About 1/1,000th of annual global energy consumption. And you probably want to add at least two or three zeros to the end of that if you're using any existing propulsion system- at which point you're taking the entire annual global energy consumption to accelerate one person ('s frozen corpse) to interstellar speeds. Multiply that by enough people to make a viable colony (at least a few hundred, assuming lots of frozen gametes to reintroduce genetic diversity at the other end) , plus enough ship and ecology to keep them alive for many decades of interstellar travel (the ISS masses about 100,000kg per person, with no attempt at being self sufficient), PLUS - and this is where it gets REALLY bad - enough energy and propellant to do the same exact maneuver in reverse to stop at the remote star, with no external infrastructure. That probably adds at least a couple more zeros right there.
So, call it imparting probably many millions, maybe billions of times annual global energy consumption to something, for a minimally viable colony ship. Not something to do lightly. You want to be *sure* those colonists reach their destination alive and healthy. And you need a massively larger energy-base than anything this planet has ever seen.
(Score: 2) by Immerman on Tuesday September 25 2018, @11:41PM
Oh, and as for
>ANY time you do something new of course there are things you will only learn by doing
Absolutely. And we need a lot of time doing, with access to additional resources to fix our mistakes, before we'll have the mature technology required to survive the decades or centuries journey through the void to another star. Had we started seriously building off-world settlements in the 70s, we might have the technology today. But we didn't have it then, and we still don't have it now.