11 ms·
The Challenge of Relativistic Spaceflight
- ceautery 13y agoI think he may have meant 1/12th rather than 1/2th of the speed of light, but I must say I'm very tempted now to start calling one half a "tooth" instead.
- shasta 13y agoMaybe not "tooth", but why do we use the phrases "a third" and "a fourth" for fractions, but not "a second" for half?
- arethuza 13y agoPerhaps because of the potential confusion with "a second" being used to mean "another" i.e. 2X rather than 1/2X. e.g. I could eat a second pizza Do I mean another pizza or half a pizza? [OK it should be phrased as "a second of a pizza" - but that is rather close to "a second pizza"]
- warbastard 13y agoYou can say "a third of a pizza" and not be confused though, so there's no difference in saying "a second of a pizza" if that were indeed an accepted use of the word.
- wernercd 13y agoSecondth?
- jperras 13y agoNot that I have a better answer, I believe the phrase "a third of a pizza" is just as confusing.
- arethuza 13y agoYou are, of course, quite correct. I should make a mental note to comment on HN while actually focusing on something else..... :-)
- bmohlenhoff 13y agoThird can be used both as a noun and an adjective. Noun form: "A third of a pizza". Adjective form: "A third pizza".
- mcdoh 13y agoBecause we should be saying "one third", "one fourth", etc., but it's a little bit faster to say "a third".
- deleted 13y ago[deleted]
- cruise02 13y agoNo, he meant 1/2 the speed of light. The speed of light is 299,792,458 m/s, so about 300,000 kilometers per second. Half that is the speed he mentioned.
- higherpurpose 13y agoI think we'll need fusion to make intra-solar system travel (really) possible, where we just transport stuff through-out the entire system, with a speed of at least 1/100 of the speed of light. Achievable in ~50-100 years. For inter-stellar space travel, say to the closest 20-100 star systems, we'll need either an anti-matter powered ship or a black-hole powered one (a bit more likely) that can travel to these stars in only a few years to a decade, and then another few years to a decade back, with the speed of 30-50 percent of the speed of light. Achievable in ~200-300 years (remember technological progress is exponential not linear). For whole galaxy exploration we'll definitely need something like a warp engine. When we'll get this is harder to predict, but it will probably take at least 1,000 years to do it. Things that could definitely help with space exploration: figuring out immortality against aging, which could also make us more interested in 100-year old projects, transferring our consciousness to machines/more resilient avatars not just for space travel, but also for living on new dangerous planets, and quantum Internet so we can rapidly communicate through long distances. If we do the last one, we might not even need to travel ourselves or transfer into other bodies, to go to those places. We'd just send robots that we control absolutely and very precisely, just like we were there (Avatar/Surrogates-style).
- jp555 13y ago> (remember technological progress is exponential not linear) No it is not. For example, airliners fly about as fast as they did a generation ago, and if you buy a desktop computer today it won't be noticeably faster than the ~3 year-old one you're using now. Do you really think the next TV you'll buy will be exponentially bigger than the one you have today? Prepare to be disappointed. warp-engine would require FTL travel, which is not possible. How can you travel a distance less than zero? At C all distances are zero. DNA is already a pretty good way to travel the stars, a human ovum (the largest human cell) has a low enough mass to get out of Earth's gravity well using only electrostatic or solar-pressure forces, no fuel required. If it were somehow interstellar-vaccum-hardened and able to modulate the energy gradient it uses to change direction, it could travel to the stars. I suppose you have misunderstood quantum entanglement, as it does not offer any way to communicate instantaneously over vast distances. It's more like when the light-standard in front of you turns green, you know INSTANTANEOUSLY that the "entangled pair" light-standard perpendicular to your view is red.
- rwmj 13y agoDoesn't your spaceship get ground down or blown to bits by interstellar dust?
- seiji 13y agoUse a very tiny, highly reinforced spaceship about the size of a standard 330 ml can.
- ackydoodles 13y agoThe numbers only become science-fictiony large if you want to go fast. Why not go slowly? The only reason humanity is obsessed with speed is because of our short life spans, but that is a solvable problem. All we have to do is to eliminate aging and it's associated diseases, and then we can take our time going to the stars. The most difficult part may be accepting limits upon our appetites, so that we are not driven to consume everything and we can live sustainably. This is an issue aboard a starship, where we will have to take a chill pill on consumption of resources, just as it is an issue on starship Earth.
- kjs3 13y agoIgnoring the whole "we'll just cure mortality...how hard can it be?", people tend to go batshit crazy after spending a couple of months in confined conditions looking at the same faces day after day. Think they're going to do better mentally when they look forward to the same for a 100 years.
- userulluipeste 13y agoThen we have to address this newly pinpointed problem - to somehow make people not „go batshit crazy”. Maybe practicing some kind of meditation? I admit that it's not as exciting as some technical overhaul we all expect, but still...
- drjesusphd 13y agoIs continually accelerating at 9.8 m/s^2 necessary? Sure, that's what's needed to get off the ground, but it seems excessive for a whole interstellar journey.
- sp332 13y agoWell if you accelerate slower, then you travel slower, then the relativistic effects of your speed are exponentially slower. So it's good to accelerate as quickly as possible.
- josh-wrale 13y agoMaster the art of "the transporter" with information being sent via optics. Send a ship out into space. Aboard will be an environment for humans and a big receiver on the side. Send the ship. Wait until it reaches it destination. "Beam" humans to the ship. If boredom ensues, reverse the transmission. Leave the "Stargate" behind. :) Edit: see quantum entanglement Edit 2: Thinking aloud about quantum entanglement. I understand that we can slow and stop light by passing it into a Bose-Einstein condensate. Can we thereby suspend two entangled particles, each in its own BEC? That way, we can send our ship out into space, unfreeze light (time?) and proceed to transmit Data (heh). Edit 3: Transmit, that is: faster than the speed of light. (thinking not) :) Edit 4: Now, I want to know what happens when a BCE containing stopped light travels at or near the speed the speed of light.. Ah never mind. I'm not a physicist. Cold and fast don't go together easily, either. :) Edit 5: Do watch: https://www.youtube.com/watch?v=-8Nj2uTZc10 https://www.youtube.com/watch?v=-8Nj2uTZc10 Edit 6: By the way, if Edit 2 is used, no big receiver would be required. Hmm.. Send the quantum receiver to a Class M planet.. Skip the on-ship environment. Terraform to taste.
- kjs3 13y agoEdit 7: Learn what all those words really mean and how they relate; drop the whole thing a get a beer.
- josh-wrale 13y agoThanks for the tip. Ever thought about going into teaching?
- kjs3 13y agoYeah. And I do.
- teraflop 13y agoYou can't use entanglement to do FTL communication. http://en.wikipedia.org/wiki/No-communication_theorem http://en.wikipedia.org/wiki/No-communication_theorem
- asgard1024 13y agoOne challenge to relativistic spaceflight is computing. If you put a CPU into a vehicle, which goes close to speed of light, it may not work properly, because the energy pulses in the device will become unsynchronized when going in different directions.
- josh-wrale 13y agoCool. I wonder if this holds true for quantum computation, as we theorize it anyway.
- ryandrake 13y agoSpecial relativity says the speed of light is the same in all reference frames. In the reference frame of the moving CPU, it would operate correctly.
- JoshTriplett 13y agoWhile the speed of light is the same, relativity also has a lot to say about accelerating reference frames. That said, if you were accelerating fast enough to affect the behavior of a CPU, you'd be experiencing G-forces comparable to the tidal forces of a black hole; computation would be the least of your problems.
- deleted 13y ago[deleted]
- scarmig 13y agoHmm, suggests a vaguely related question to my mind. Generally speaking, do black holes have any implications for computations? E.g. does having a black hole at your disposal let you solve any problems you wouldn't be able to otherwise?
- oakwhiz 13y agoWhat you are describing is a form of hypercomputation. It is not yet known whether hypercomputation is even really a "thing." A hypercomputer, if it existed, would be able to solve the halting problem. http://en.wikipedia.org/wiki/Hypercomputation http://en.wikipedia.org/wiki/Hypercomputation http://en.wikipedia.org/wiki/Malament-Hogarth_spacetime http://en.wikipedia.org/wiki/Malament-Hogarth_spacetime
- ryandrake 13y agoTL;DR: Chemical propulsion is a dead end. But, the alternatives require matter/energy of ridiculous scale (hundreds of times the power output of human civilization, launching hundreds of millions of tons of matter into orbit). We're not going anywhere, any time soon.
- Tloewald 13y agoNot just magnitude but duration. Name one machine that works without major overhaul for more than 100 years. For bonus points, name a machine that's significantly more complex than a clock.
- ForHackernews 13y agohttp://www.wired.com/gadgetlab/2011/06/10000-year-clock/ http://www.wired.com/gadgetlab/2011/06/10000-year-clock/
- Tloewald 13y agoHence my bonus points ;-)
- Houshalter 13y agoName one machine that's designed to work for over 100 years. Many of NASA's spacecraft have survived well beyond their intended death dates, because they were constructed so well, and because space is cold, static, and good at preserving things.
- Tloewald 13y agoThere are plenty of simple, well-made machines designed to work indefinitely -- e.g. doorknobs, window assemblies. Even simple, robust, well-maintained machinery tends not to last a very long time. There's a stone bench somewhere that Thomas Jefferson supposedly used to sit on that has become curved over time.
- 13y ago
- cousin_it 13y agoWhat's the point of these huge generation ships? It's not like there's not enough atoms on other planets. You should send a tiny fast robotic ship, maybe with an uploaded mind if your AI tech isn't good enough. It will mine materials at the destination and build a receiver antenna. Then you can send more uploaded minds by radio, which will arrive at the speed of light with low energy cost. Another reason why you shouldn't send human bodies in tin cans, or even grow them from eggs on the spot, is that human bodies are not adapted to the conditions in space or at the destination, so they would need an unreasonable amount of life support equipment. If you really want a colony of biological creatures with human minds for some reason, bioengineer the right kind of bodies on the spot and download minds into them.
- snowwrestler 13y agoIf we're going to stipulate fantastic concepts like "uploaded minds" then let's just invent a hyperspace engine too and solve all the problems at once. In the real world, we want to send human bodies because that's what human minds are. Cartesian duality is a religious/philosophical concept for which no scientific basis has yet been found.
- Tloewald 13y agoUploaded minds is hardly an argument depending on cartesian duality. Arguing that there's something irreproducible about the human brain is quite close to cartesian duality. I am not arguing that uploading minds is any more feasible than a generation ship, but it is at least more plausible than hyperdrive -- based on what we think we know right now.
- mitchty 13y agoI guess I disagree that uploading minds is more feasible. One is more of an engineering/physics challenge, and uploading minds is dependent upon a vast set of unknown unknowns. We aren't even out of the door on the idea of biological computing let alone at the mailbox.
- adrianN 13y agoOne efficient way to convert mass to energy is using the Hawking radiation of artificial black holes. This seems to by allowed by the laws of physics according to this paper: http://arxiv.org/abs/0908.1803 http://arxiv.org/abs/0908.1803
- TrainedMonkey 13y agoWhat I got out of that is first company or nation to manage useful self replication technology in space will gain immense power.