Wikipedia:Reference desk/Archives/Science/2017 March 14

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March 14

Interstellar travel and intergalactic travel

Does the entire planet Earth has enough resources for interstellar travel? Is intergalactic travel possible? --IEditEncyclopedia (talk) 00:14, 14 March 2017 (UTC)

Voyager 1 and Voyager 2 are engaged in interstellar travel. If you're talking about practical travel, i.e. by humans in something well short of an average lifespan, we don't have the technology to do that, so we can't say what resources it would require. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:33, 14 March 2017 (UTC)

Yeah it is about manned travel. --IEditEncyclopedia (talk) 00:35, 14 March 2017 (UTC)

And as the articles imply, interstellar would necessarily precede intergalactic, as the nearest neighboring galaxy is way much farther away than the width of our own galaxy. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:43, 14 March 2017 (UTC)

I agree with the above; even human interplanetary travel further than the moon, or for any long stay, is currently very challenging. There are some complex scenarios being studied to send humans on Mars, and for colonization of Mars. PaleoNeonate (talk) 00:48, 14 March 2017 (UTC)

To quote Douglas Adams, "Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:55, 14 March 2017 (UTC)

IMHO, the lowest form of power source that might be viable for manned interstellar travel is a nuclear fission reactor, which could then be used to run a linear accelerator and send a matter stream out the back at near the speed of light, hopefully in quantities that can produce a constant 1 g acceleration. We have a huge quantity of fuel for such a reactor, especially if we were to decommission nuclear weapons for their atomic cores. This technology is available now. The next step up would be fusion reactors, which don't require specialized fuel, or better yet, matter-antimatter reactors (no article ?), which require extremely specialized fuel (the antimatter part), which we would need to produce on Earth, or hopefully someplace safer, like the Moon. Those technologies don't yet exist, at least in practical forms. As for the mass to shoot out the back, we could grab an asteroid for that. I like the idea of placing it in front of the ship, for the journey, to use it as a shield, while it is mined down to use as the propulsion mass. StuRat (talk) 01:09, 14 March 2017 (UTC)

Or just digitize your brain, send a simple radio message explaining how to decode and run the data in the next message and then go ahead with sending the data. We repeat this over and over again (so, we don't wait for a reply). If 2.5 million years later, ET in the Andromeda galaxy were to receive StuRat's digitized brain contents this way, they could run him and then StuRat, who would be long dead here on Earth, would wake up in the same state he was in when he was digitized. From StuRat point of view, this means that he has to be prepared for the fact that he could find himself in some ET's computer immediately after being digitized, even though he would yet have to be sent and the message would be received a long time after that. Count Iblis (talk) 02:03, 14 March 2017 (UTC)

Would that really be you or just something just like you? And no, he would not have to be prepared to wake up immediately after being digitized, the StuRat that wakes up will be a brand new sentience that never existed before. To show that this is true, what if some guy reanimated his brain into his clone on Earth while he was still young? Then he could immediately screw the clone. He will not be the bottom, a being that never existed before would be the bottom. Sagittarian Milky Way (talk) 15:32, 14 March 2017 (UTC)

That brand new sentience is nevertheless identical to StuRat because, by construction, he will react to every stimulus in exactly the same way as the "real" StuRat the moment he was digitized. It's basically what is pointed out here at the end of this story about identical copies of us in an infinite multiverse. Count Iblis (talk) 00:23, 15 March 2017 (UTC)

James Patrick Kelly's Think Like a Dinosaur and the subsequent Think Like a Dinosaur (The Outer Limits) episode were excellent fictional treatments of this topic, and, in particular, whether destroying the original is murder. StuRat (talk) 01:07, 15 March 2017 (UTC)

• (Edit conflict) To elaborate on Bugs' earlier point, the nearby Andromeda galaxy is 2 1/2 million light years away. So even if we could quickly accelerate to near light-speed, it would take 2 1/2 million years to get there. So manned intergalactic travel is not possible unless we are willing to commit many generations of space travelers to the effort. Loraof (talk) 02:08, 14 March 2017 (UTC)

  Understatement of the year. Anatomically modern human have only existed for about 45,000-50,000 years. So we'd have to survive as a species some 50 times longer than we already have, and do so on a spaceship. That is, if we had started traveling towards Andromeda at the beginning of when anatomically modern humans evolved, we'd only be 1/50th of the way there today. Good luck on making it that far... --Jayron32 02:18, 14 March 2017 (UTC)

• You've neglected time dilation. If close enough to the speed of light, very little time would pass aboard the ship. Of course, there may very well be nothing recognizable as human to report your results to, after making a round-trip. StuRat (talk) 03:53, 14 March 2017 (UTC)

• Time would appear "normal" to those on-board the travelling ship. It would be the distance to the other galaxy that would appear contracted. (I agree that this depends on your speed of view.) Dbfirs 07:12, 14 March 2017 (UTC)

That's only unless people are able to achieve an alcubierre drive,which I'm surprised no one has even mentioned.Uncle dan is home (talk) 02:33, 14 March 2017 (UTC)

Be careful. Linking to that article will summon BenRG, and he will have to explain to you why people get way too excited about it. Actually, go and look for it in the refdesk archives, he's made some good comments on it. Someguy1221 (talk) 02:36, 14 March 2017 (UTC)

An infinite improbability drive or Bistromathic drive would both do the trick. --Jayron32 02:42, 14 March 2017 (UTC)

• The real problem with traveling fast enough to get to Andromeda in a few years is that your spacecraft will be exposed to extremely high energetic radiation and dust particles. At a gamma factor of a million, the kinetic energy of a dust particle will be a million times its rest mass; being hit by a microgram dust grain will lead to about $10^{14}$ Joules of energy being deposited, which is similar to the yield of the atomic bomb dropped on Hiroshima. Count Iblis (talk) 00:41, 15 March 2017 (UTC)

• This is why I propose travelling with an asteroid in front of the ship, to use as a shield. StuRat (talk) 01:00, 15 March 2017 (UTC)

• The classic hard science fiction story about this is Tau Zero. If you can continue to accelerate at 1 G, your velocity will eventually (within two shipboard years?) get so close to C that time dilation becomes extreme ("Tau" approaches zero) and you can reach anywhere in the universe. This is not possible with today's technology because the amount of fuel would be "very large." The author avoids this by using a Bussard ramjet, which gathers hydrogen from the interstellar/intergalactic medium while the ship is in flight. -Arch dude (talk) 03:31, 15 March 2017 (UTC)

The Tau Zero story ship also had some kind of gravity control so they could accelerate at substantially more than 1 g. 10 g comes to mind. Jim1138 (talk) 10:07, 18 March 2017 (UTC)

The equation is driven by the the square of the time, so at 1 G, it takes sqrt(10) longer, or about three times longer to achieve the same result. Thus, it will take our voyagers about 6 years ship time instead of 2 years to reach anywhere in the observable universe, given a drive capable of 1 G acceleration. As the Bussard ramjet article points out, the ramjet will need to operate on a CNO fusion cycle to be efficient enough to overcome the inertia of the collected hydrogen at very low Tau: proton-proton fusion is insufficient. All of this requires engineering far beyond our current capabilities, but not mega-engineering or new physics. -Arch dude (talk) 15:50, 18 March 2017 (UTC)

I think, given the way commercial spaceflight companies are booming, in the next 200 years, humans will established permanent lunar base for mineral extraction and space experiments. In the next 500 years, asteroid mining might well become commercially viable. So human will colonize gradually, starting from moon, then mars, then expanding to outer solar system. I might well take 5000 years. After that, they will start colonizing extra solar planets. So, say, lets assume, 1 million years from now, humans will colonize the entire Milky Way. So the starting point of journey towards another galaxy will not be Earth, but some other star system in our galaxy. Should be reduce the distance between the starting point of journey and the other galaxy? --IEditEncyclopedia (talk) 01:36, 16 March 2017 (UTC)

Anything's possible, but we're still using conventional rocketry for transportation. And no matter where you start within the Milky Way, you're way much closer to anything in the Milky Way than you are to the nearest neighboring galaxy. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:41, 16 March 2017 (UTC)

• I have heard that to colonize Mars and make it self-sufficient, the colony would need about a million highly productive people. If the destination planet is not Terraformed, one would probably need at least a million and lots of equipment just to build and maintain an infrastructure to survive. An economy capable of producing everything needed to build, maintain, and grow a colony would be huge. Raw materials mining, extraction, and processing to make goods. Instrument and equipment construction from scratch. Food production, likely the easy part (in a self-contained habitat). Power plant construction. Semiconductor fabrication including all the equipment and chemicals needed, etc. Take a look around you and think what equipment and people you would need to transport to enable it to be manufactured on another planet. A cell phone, for instance might have hundreds of thousands of people involved in one aspect or another of its construction from raw-materials. If something critical in the infrastructure fails, it's all over.

Putting a number of people into a box (interstellar space craft) for a few hundred years is probably not without its risks as well.

The Orion drive, using current technology, possibly could reach a nearby star. It uses nuclear bombs for propulsion. You would need about a million bombs to accelerate up to 3% of lightspeed, 9,000 KM/S (150 years to lpha Centauri and another million bombs to decelerate. Hopefully your bombs won't degrade over 150 years...

If the planet is Terraformed, you could just drop of a few people (good genes preferred) and let them reproduce. No advanced technology needed.

Maybe we could send a robot to Terraform the target planet or build a space habitat. People could be grown from frozen embryos or even a DNA data bank. Jim1138 (talk) 10:07, 18 March 2017 (UTC)

pinpointing science fiction movie with "very noisy rain dropping down"?

I'm trying to pinpoint/remember a science fiction movie staged at a planet with devastating rain and two guys taking shelter in some mushroom shaped structure so they wouldn't turn crazy from the noise of the rain which (I think) was amplified due to the planets high gravity. Lots and lots of years have past since I saw that (part of?) the movie. I guess it's from the 80's or early 90's. Quite grateful if someone can resolve that brain fart of mine.--TMCk (talk) 01:32, 14 March 2017 (UTC)

You may get an answer here but I would suggest you move this to Wikipedia:Reference desk/Entertainment TracyMcClark. MarnetteD|Talk 01:35, 14 March 2017 (UTC)

(ec) I'm asking it here on the science desk since I might have some science related followup questions.--TMCk (talk) 01:36, 14 March 2017 (UTC)

The film is The Illustrated Man, and the story on which this part of the film was based is The Long Rain by Ray Bradbury. DuncanHill (talk) 01:39, 14 March 2017 (UTC)

Thanks. That sure must be what I watched some late night years ago. Now the next question is if there is some science of such "hard dropping noisy" rain causing any mental harm in real life.--TMCk (talk) 02:27, 14 March 2017 (UTC)

Perhaps I was over confident - it was also adapted as an episode of The Ray Bradbury Theater in 1992. DuncanHill (talk) 01:45, 14 March 2017 (UTC)

Also sounds vaguely like an original Outer Limits episode, where being caught in the rain caused one to become evil, grow comically large eyes, and gain the powers to read minds and vaporize people with a touch. Not their best work. StuRat (talk) 02:10, 14 March 2017 (UTC)

There's noise pollution, but that fortunately seems nowhere near that. PaleoNeonate (talk) 02:52, 14 March 2017 (UTC)

The Mutant is the episode in question, but it was chemicals in the rain, not the noise, which were the supposed problem. StuRat (talk) 03:46, 14 March 2017 (UTC)

I have to wonder if the author had a metal roof on his house, which seem like they could drive one insane from the noise, during rain. StuRat (talk) 03:48, 14 March 2017 (UTC)

Much of Futurama is a reference to other work. The episode Brannigan, Begin Again features high velocity rain on a high gravity planet, but I don't see anything indicating that the high gravity rain has anything to do with previous work. I hoped there would be some geek reference system that would say, "The high gravity rain is a reference to..." 209.149.113.5 (talk) 17:55, 14 March 2017 (UTC)

Did you look at IMDb's Trivia and Connections pages for the episode? —Tamfang (talk) 15:31, 18 March 2017 (UTC)

This is where ear plugs come in. But then you wouldn't have a story. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:20, 14 March 2017 (UTC)

I'm fairly sure a survey of literature with a 19th-century colonial setting would find instances of Europeans supposedly being sent mad by unending torrential monsoon rain on a corrugated tin roof: that and the continual drumming of the locals is something of a comedy cliché. I can't however bring any specific instances to mind. {The poster formerly known as 87.81.230.195} 90.202.209.145 (talk) 18:42, 14 March 2017 (UTC)

Honey, I Shrunk the Kids? --Hans Haase (有问题吗) 11:32, 16 March 2017 (UTC)