6 ms·
For those wondering about interstellar travel in sleeping pods, at room temperature humans could only be “frozen” for 10 years (1% bonds broken) before too much
by samarama 5y ago
For those wondering about interstellar travel in sleeping pods, at room temperature humans could only be “frozen” for 10 years (1% bonds broken) before too much DNA damage would have occurred.
However, in temperature below zero at -5 degrees Celsius for example, half life of DNA is actually 10,000 years or more. https://en.m.wikipedia.org/wiki/Ancient_DNA https://en.m.wikipedia.org/wiki/Ancient_DNA
Still, this would also only allow 200 years of freezing before more than 1% of bonds would have been broken.
The third and probably most viable option is to wake up the crew every 200 years to repair accumulated DNA damage.
Also, a small percentage of the crew would probably be awake at all times for repairs etc., so the crew could rotate every 200 years.
- ReaLNero 5y agoA half-life of 10,000 years means the fraction (0 to 1) of healthy bonds at year t can be modeled by (1/2)^(t/10000). To have 1% bonds broken, it would take an expected 145 years. EDIT: Fixed the numbers, my bad!
- vient 5y ago>>> log(0.99, (1/2)**(1/10000)) 144.99569695122509
- jdmoreira 5y agoI don't understand this. Does half-life even say anything else about the probability distribution? aren't you assuming specific distribution here?
- dekhn 5y agohalf lives (specifically, the "decay" of any individual thing is stochastic but the aggregate of many molecules models exponential decay (in radioactivity. I have no idea what happens in a complex mash of DNA)
- sannee 5y agoIt's not a terrible assumption to make. We just need to assume[1] that the decay events are independent, that is, every bond flips a coin every 500 years and if it comes up heads, it breaks, independent of what the other bonds do. That is, the process is inherently "local", individual bonds having no way of knowing what the other bonds are doing. [1] It may be a bit worse in the long run, since if many bonds break, the higher order DNA structure gets damaged and that may change the rate of decay experienced by individual bonds (?).
- cochne 5y agoYour 15 years number is for 0.1%
- stocknoob 5y agoThis shows the importance of mental gut checks. If indeed 1% break after 15 years, then 10% (ignoring compounding) break after 150 years, and 50% after 750 years. That doesn’t square with a half life of 10,000.
- ReaLNero 5y agoI always forget Bernoulli's inequality. Your gut isn't as clever as mine :)
- lettergram 5y agoEven in a -80C freezer with dehydrated and frozen cells they don't recommend over 5 years. https://www.researchgate.net/post/How-long-can-fresh-frozen-tissue-be-stored-at-80C https://www.researchgate.net/post/How-long-can-fresh-frozen-...
- rthomas6 5y agoIf you go fast enough, accelerating and decelerating at 1 g, you can travel a million light years in a perceived time of about 27 years.
- mlindner 5y agoYes, but you also need nearly infinite fuel.
- rthomas6 5y agoNah, just 3e18 kg ;)
- opportune 5y agoAn efficient engine could use antimatter as its battery/fuel source and move itself forward by using antimatter to eject propellant close to the speed of light in the opposite direction right? That probably wouldn’t require a large mass of antimatter/propellant. Especially since you can collect propellant from the interstellar medium wherever you’re going
- ben_w 5y agoEven antimatter has limits, and those limits deny reaching a relativistic gamma of 1e6/27: http://www.projectrho.com/public_html/rocket/enginelist3.php http://www.projectrho.com/public_html/rocket/enginelist3.php But even if you ignore that limit, at that kind of speed you also need to account for your outer hull undergoing significant damage as each stray intergalactic hydrogen you hit has a kinetic energy of 34.75 TeV in your frame of reference, and while this will create a large supply of antimatter, it will do so in a way significantly less helpful to your goal than the fact we can transmute lead into gold by using the former as a radiation shield in a nuclear reactor is useful to someone who wants to get rich quick. Bonus fact: this energy level is higher than the LHC, so you may have some extra weird mass-modification effects besides relativity as the front of your spaceship is now a Higgs Boson torch.
- IncRnd 5y ago
- mchusma 5y agoI like your thinking! A couple of points: (1) we don't really know the threshold yet to be beyond repair I think. It may be 1% but may be 20%. (2) as others noted, it's 15 years for 0.1% damage using your math. (3) your timeline directly contradicts the article doesn't it, which suggests keeping people in ideal conditions would have a DNA half life of millions of years. (4) it's not a given that you need to wake people up to repair DNA. Maybe you just need to bring them to 1 degree Celsius or something. Or maybe nanobots can work on you while completely frozen. I think we are quite far from knowing right now. So yes, for long term travel DNA repair will be important but how it actually works I think we know little about.
- samarama 5y agoGood points, but why is it 15 years for 0.1%?
- sandworm101 5y ago>> crew would probably be awake at all times for repairs etc If the ship requires human crews to conduct regular repairs, then the ship probably won't last long enough to get where it is going. A ship that is going to last for 10,000 years will need to be built like an Egyptian pyramid, solid enough to last forever and be functional despite millennia of erosion. Putting someone on that pyramid to conduct repairs might sound good, but after 10,000 years those repairs would become just another source of erosion. The activities of that one person would wear down any system with which they interact.
- sixQuarks 5y agoErosion in space is much different than on earth. Even the rovers left on the moon 50 years ago should in theory still work.
- flatiron 5y agoAnd it’s silly to think about. Who cares. 300 years from now people will be taking trash out in mars and people will be picking it up. We will spread our disease at least within out universe.
- WalterBright 5y agoThere's no biosphere on Mars, nothing alive there, our Terran notion of pollution makes no sense on Mars.
- quartesixte 5y agoOur Terran notion of pollution makes no sense anywhere without Terran compatible atmospheres.
- mlindner 5y agoThe above poster is talking about physical erosion by human interaction. There are ruts worn into solid rock in many parts of the world with old roads that are only 1000 or 2000 years old. Over 10,000 years anything that is touched by humans will be worn away to no material at all.
- takinola 5y agoDon’t we have highly durable generational spaceships already? They’re called asteroids. If we find an asteroid that’s large enough to have internal geothermal activity, you could put a bunch of people in an underground system and nudge it into a trajectory towards another star system. As long as it can support crops, oxygen generation, etc the passengers just proceed to live a “normal” life for the next couple generations until they arrive in orbit around a brand new star. The hardest part would be maintaining culture to still identify with the purpose of the mission after there’s no one of the original passengers left over
- tremon 5y agoI don't think most asteroids are large or dense enough to have adequate geothermal heat to sustain a human population? Anyone got a back-of-the-envelope calculation for what size asteroid we'd need for this?
- Qem 5y agohttps://arc.aiaa.org/doi/10.2514/6.2014-4373 https://arc.aiaa.org/doi/10.2514/6.2014-4373
- justinator 5y agoDon’t we have highly durable generational spaceships already? They’re called asteroids. A planet. You're describing a planet. And we're doing a pretty terrible job keeping this planet we're traveling on sustainable for human habitation.
- takinola 5y agoWell the one we’re on has made it 4 billion years. Getting one to last 10,000 years should be a lot easier
- beaconstudios 5y agoIt has only been about 5000 years since humans became sedentary and formed civilisations and we're already seriously disrupting the ecosystem. That's the timeline you'd have to look at.
- Zenst 5y agoI'm sure there are ways in which we are still learning and right out of the plot of a film that needs no mention: https://newatlas.com/science/extract-insect-dna-amber/ https://newatlas.com/science/extract-insect-dna-amber/
- xorencrypted 5y agoAt the speed of travel you would want to traverse space, wouldn't the time dilation make the half life of passengers less of a problem?
- airstrike 5y agoHow about frozen embryos and artificial wombs for gestating those embryos X years before arrival? Then you only need a crew of X people at any given time to keep the ship operational. Some generations would be born and die during the trip (kinda depressing, but I like to think I would be happy in that scenario) If you don't like the idea of having a machine as your mother, you could also do IVF with the women that are alive and well and constitute ~50% of the crew keeping the ship operational