0786: "Exoplanets"

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0786: "Exoplanets"

Postby Eebster the Great » Mon Aug 30, 2010 4:00 am UTC

Image
Alt text: "I'm just worried that we'll all leave and you won't get to come along!"

Brilliant. Of course, no explanation is given as to why we should look for destinations decades before the method of travel exists, but meh.
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Re: "Exoplanets" Discussion (#786)

Postby Dason » Mon Aug 30, 2010 4:06 am UTC

Eebster the Great wrote:Brilliant. Of course, no explanation is given as to why we should look for destinations decades before the method of travel exists, but meh.


Code: Select all
from __future__ import interstellar
double epsilon = -.0000001;
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Re: "Exoplanets" Discussion (#786)

Postby Werewolf » Mon Aug 30, 2010 4:19 am UTC

These topics were posted within the same minute :/

I don't know what to do.
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Re: "Exoplanets" Discussion (#786)

Postby Eebster the Great » Mon Aug 30, 2010 4:20 am UTC

Werewolf wrote:These topics were posted within the same minute :/

I don't know what to do.

Technically mine was first, according to the forum. That is, his was on top.

But I don't have a screenshot to prove it, and it doesn't really matter.
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Re: "Exoplanets" Discussion (#786)

Postby homeobocks » Mon Aug 30, 2010 4:25 am UTC

Eebster the Great wrote:Image
Alt text: "I'm just worried that we'll all leave and you won't get to come along!"

Brilliant. Of course, no explanation is given as to why we should look for destinations decades before the method of travel exists, but meh.


Brilliant? A wordy lead to a "snooze-button" joke that sounds like something Seinfeld would have wrote while coming down off coke?
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Re: "Exoplanets" Discussion (#786)

Postby Dason » Mon Aug 30, 2010 4:26 am UTC

Eebster the Great wrote:
Werewolf wrote:These topics were posted within the same minute :/

I don't know what to do.

Technically mine was first, according to the forum. That is, his was on top.

But I don't have a screenshot to prove it, and it doesn't really matter.

That's why I posted in this one. Plus I've actually seen you around and yours was formatted better.
double epsilon = -.0000001;
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Re: "Exoplanets" Discussion (#786)

Postby NoOutlet » Mon Aug 30, 2010 4:28 am UTC

You don't need a screenshot. The topic_id is enough to prove it. Yours is 63796 and his is 63797.
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Re: "Exoplanets" Discussion (#786)

Postby Pez Dispens3r » Mon Aug 30, 2010 4:30 am UTC

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Re: "Exoplanets" Discussion (#786)

Postby paragon12321 » Mon Aug 30, 2010 4:32 am UTC

Is this the Sagan Man alarm clock?
For great justice! Take off every sig!
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Re: "Exoplanets" Discussion (#786)

Postby Eebster the Great » Mon Aug 30, 2010 4:43 am UTC

homeobocks wrote:Brilliant? A wordy lead to a "snooze-button" joke that sounds like something Seinfeld would have wrote while coming down off coke?

Well, my comment was a. directed at the character, not Randall, and b. sarcastic. But you can take it however you like.
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Re: "Exoplanets" Discussion (#786)

Postby homeobocks » Mon Aug 30, 2010 4:55 am UTC

Eebster the Great wrote:
homeobocks wrote:Brilliant? A wordy lead to a "snooze-button" joke that sounds like something Seinfeld would have wrote while coming down off coke?

Well, my comment was a. directed at the character, not Randall, and b. sarcastic. But you can take it however you like.

Cool.
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Re: "Exoplanets" Discussion (#786)

Postby pgn674 » Mon Aug 30, 2010 5:24 am UTC

homeobocks wrote:Brilliant? A wordy lead to a "snooze-button" joke that sounds like something Seinfeld would have wrote while coming down off coke?
I think Randal wanted to point out that we live in cool times and, on a long time scale, exciting times. He probably used his artist character because artists (or maybe at least this guy) tend to think big. Also, this artist has displayed a lack of understanding logical relationships in the past, now between the length of snooze time and the logistics of choosing a planet for your future generations. I do think this comic may have worked better as an awe-inspiring type, probably without a joke at the end, though.
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Re: "Exoplanets" Discussion (#786)

Postby Eternal Density » Mon Aug 30, 2010 5:29 am UTC

My version:
"How exciting, a new xkcd!"

"Can I just hit snooze?"
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Re: "Exoplanets" Discussion (#786)

Postby LSN » Mon Aug 30, 2010 5:45 am UTC

pgn674 wrote:
homeobocks wrote:Brilliant? A wordy lead to a "snooze-button" joke that sounds like something Seinfeld would have wrote while coming down off coke?
I think Randal wanted to point out that we live in cool times and, on a long time scale, exciting times. He probably used his artist character because artists (or maybe at least this guy) tend to think big. Also, this artist has displayed a lack of understanding logical relationships in the past, now between the length of snooze time and the logistics of choosing a planet for your future generations. I do think this comic may have worked better as an awe-inspiring type, probably without a joke at the end, though.


He's the Existentialist, just to clarify. I don't recall him doing anything artsy thus far.
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Re: "Exoplanets" Discussion (#786)

Postby Panama1984 » Mon Aug 30, 2010 5:46 am UTC

Somebody was reading last month's Wired...
http://www.wired.com/magazine/2010/08/f ... ferrell/2/

And it wasn't a "snooze" joke, it was making fun of people that are all "Oh me yarm WE NEED TO GO NAOO" for space travel even though, in all practicality, it won't be another ~100 years before we even start sending ships to the outer planets.
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Re: "Exoplanets" Discussion (#786)

Postby Roivas » Mon Aug 30, 2010 6:00 am UTC

I am somewhat surprised that a science fiction writer, though he hasn't done many books, could say that something will never happen. Just because something seems impractical or even fantastical in scale and scope doesn't mean it isn't possible. We can instantly communicate with one another from one side of the planet to the other right now, a feat that our grandparents are still having a tough time wrapping their heads around.

We're going to colonize any viable planet we can find. It just isn't going to be quick. Like the comic says, we're probably not going to do it ourselves, but we might live just long enough to see the first ships leave earth only to fly straight into a black hole or something.

Basically, we already live the future. We just need to live in the distant future now.
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Re: "Exoplanets" Discussion (#786)

Postby LesZedD4 » Mon Aug 30, 2010 6:07 am UTC

Scaling out to the universe would be cool. personally, i'm just waiting for us to be able to live on the moon. I'm gonna be first in line. I want to be able to point a microwave emitter at the ground and pave my path in glass. :D
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Re: "Exoplanets" Discussion (#786)

Postby EdgarJPublius » Mon Aug 30, 2010 6:15 am UTC



This basically only brings up two problems with space colonization, both of which are adressed by the comic:

Problem 1: suitable exo-planets are few and far between
Solution: This is actually because we haven't been looking hard enough for long enough, the equipment used to search for planets in other systems is just now on the cusp of being able to detect planets that are actually suitable for colonization, and given the current rate of new-planet discovery it's likely that within the next five or ten years we'll be spotting terrestrial planets within their stars habitable zone.
Before very recently, we've only been able to guess at the existence of planets in other systems, and even just a few years ago, spotting all but the most obvious super-sized planets was mere fantasy, so the universe looked like a pretty barren place. We live right now at the dawn of a time when we're starting to populate our celestial neighborhood with planetary systems.

Problem 2: it takes a really long time to get anywhere outside our own solar system
Solution:
GLORIOUS NUCLEAR PROJECT ORION.
Project Orion is actually an idea first formulated by some of the earliest nuclear scientists and engineers, including some key members of the Manhattan project, back in the late 1940s. The idea was actually thoroughly investigated and some relevant proof of concept tests were carried out, including some tests involving live nuclear detonations.

The idea is to propel a spacecraft with a long string of nuclear explosions.
Although it sounds pretty fantastical, there's really not much to it, and most of the engineering problems were solved by the 1960s, when the program was eventually canceled by the partial test ban treaties which restricted atmospheric and orbital tests of nuclear devices.

Compared to 'conventional' space-craft, such as chemical rockets, Project Orion has quite a few advantages. But for interstellar travel the upshot is that an orion-craft would be capable of reaching nearby stars within a human lifetime, and would have a favorable enough fuel fraction (the ratio of fuel to payload needed to make the trip) that very large colony ships are practical.

Roivas wrote:
We're going to colonize any viable planet we can find. It just isn't going to be quick. Like the comic says, we're probably not going to do it ourselves, but we might live just long enough to see the first ships leave earth only to fly straight into a black hole or something.

I actually wrote a short story where this happens :P
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Re: "Exoplanets" Discussion (#786)

Postby horza » Mon Aug 30, 2010 7:06 am UTC

If asteroid-based automated mining stations/refineries are to be build - and we're not really far from that give that china expressed interest in asteroid minig not so long ago - then the steps to at least Project Daedalus will be easier to take.

Once Daedalus is sent - it's going to be some 50 years before we manage to get a positive response from it along with a thorough scan of whatever viable destination (not the original barnard's star, which was probably chosen only because the coolness of the name) we might choose for it.

During the 50 years from launch - it's probable that additional models will be launched, probably also smaller scale probes designed for solar planets.

Also, from asteroid bases - moon jumping will be easier, also materials for base building will be cheaper. Once the mining becomes feasible, private companies will invest heavily and civilian travel to orbit and even moon will become as cheap as maybe current airplane tickets. Also with orbit being available so readily and cheaply, medical research will improve dramatically - it already does, with the low resources available right now - and life expectancy might improve sensibly as a result.

Which makes me confident that - given no unexpected accidents - I might be alive to at least witness, if not take part, in a outer planet colonization project.
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Re: "Exoplanets" Discussion (#786)

Postby theduffman » Mon Aug 30, 2010 7:24 am UTC

Correction: in slide 3, "cultures" should read "cultural" or "culture's"
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Re: "Exoplanets" Discussion (#786)

Postby ijuin » Mon Aug 30, 2010 7:30 am UTC

horza wrote:IOnce Daedalus is sent - it's going to be some 50 years before we manage to get a positive response from it along with a thorough scan of whatever viable destination (not the original barnard's star, which was probably chosen only because the coolness of the name) we might choose from it.

Actually, at the time that Daedalus was first conceived, Barnard's Star was believed to possess two planets orbiting it, but more recent data makes their existence doubtful. Thus, it would have been the nearest star to us that would have a planetary system (Alpha Centauri A and B are too close together for planets in the habitable zone to have stable orbits over a multibillion-year time span, and Proxima Centauri is believed to have no Earth-mass or larger planets).

The threshold, I think, for sending the general population into space, would be when the cost gets below about a million dollars per person (in 2010 US dollars). Above that cost, and even the government will want to limit the list of people to those whom it deems the most useful (or lucrative).

Eebster the Great wrote:Brilliant. Of course, no explanation is given as to why we should look for destinations decades before the method of travel exists, but meh.


Conversely, why should we invest hundreds of billions of dollars in inventing methods of travel when there's nowhere to go? Would the Europeans have invented sailing ships capable of traveling through hurricanes out of sight of land for half a year on end if they didn't believe that they could reach distant lands? The biggest incentive to develop interstellar flight would be to discover a planet out there with life on it (not intelligent life, but even just a planet whose atmosphere has free oxygen). To have an actual New World to go to would be far more attractive than all the thousands of uninhabitable rocks and gas giants that we will find before finding a planet with life.
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Re: "Exoplanets" Discussion (#786)

Postby horza » Mon Aug 30, 2010 8:07 am UTC

Actually, at the time that Daedalus was first conceived, Barnard's Star was believed to possess two planets orbiting it, but more recent data makes their existence doubtful.


My god and I wanted to add that extra info but thought it would be too much :))
Yea indeed - however that was a fine example of why you shouldn't build for space travel before you have a firm grip of what the destination really is like :)
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Re: "Exoplanets" Discussion (#786)

Postby oddy » Mon Aug 30, 2010 10:15 am UTC

This comic is brilliant, sums up the way I feel when people (read: idiots) complain that this is a boring time to be alive.

Just makes it a bit of a shame that I won't live to see it happen. Unless of course the singularity happens soon! (Fingers crossed)

Also: why enrich uranium? I thought H-bombs were more powerful?
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Re: "Exoplanets" Discussion (#786)

Postby chrth » Mon Aug 30, 2010 11:29 am UTC

oddy wrote:Also: why enrich uranium? I thought H-bombs were more powerful?


I may be misremembering, but I believe H-bombs are two- or three-stage detonations. I think you need an initial fission reaction to create the fusion reaction. I think. (Did I qualify that enough?)
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Re: "Exoplanets" Discussion (#786)

Postby Pez Dispens3r » Mon Aug 30, 2010 11:35 am UTC

EdgarJPublius wrote:


This basically only brings up two problems with space colonization, both of which are adressed by the comic:

Problem 1: suitable exo-planets are few and far between
Solution: This is actually because we haven't been looking hard enough for long enough, the equipment used to search for planets in other systems is just now on the cusp of being able to detect planets that are actually suitable for colonization, and given the current rate of new-planet discovery it's likely that within the next five or ten years we'll be spotting terrestrial planets within their stars habitable zone.
Before very recently, we've only been able to guess at the existence of planets in other systems, and even just a few years ago, spotting all but the most obvious super-sized planets was mere fantasy, so the universe looked like a pretty barren place. We live right now at the dawn of a time when we're starting to populate our celestial neighborhood with planetary systems.

Problem 2: it takes a really long time to get anywhere outside our own solar system
Solution:
GLORIOUS NUCLEAR PROJECT ORION.
Project Orion is actually an idea first formulated by some of the earliest nuclear scientists and engineers, including some key members of the Manhattan project, back in the late 1940s. The idea was actually thoroughly investigated and some relevant proof of concept tests were carried out, including some tests involving live nuclear detonations.

The idea is to propel a spacecraft with a long string of nuclear explosions.
Although it sounds pretty fantastical, there's really not much to it, and most of the engineering problems were solved by the 1960s, when the program was eventually canceled by the partial test ban treaties which restricted atmospheric and orbital tests of nuclear devices.

Compared to 'conventional' space-craft, such as chemical rockets, Project Orion has quite a few advantages. But for interstellar travel the upshot is that an orion-craft would be capable of reaching nearby stars within a human lifetime, and would have a favorable enough fuel fraction (the ratio of fuel to payload needed to make the trip) that very large colony ships are practical.

Nice points. If I'm not convinced, I at least feel more informed :)
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Re: "Exoplanets" Discussion (#786)

Postby gordysc » Mon Aug 30, 2010 12:21 pm UTC

chrth wrote:
oddy wrote:Also: why enrich uranium? I thought H-bombs were more powerful?


I may be misremembering, but I believe H-bombs are two- or three-stage detonations. I think you need an initial fission reaction to create the fusion reaction. I think. (Did I qualify that enough?)


This comic made my day. Not because of the strip, or the arguing about using bombs to go through space, but because of this comment I looked up H bomb and found on wikipedia:

" The second was detonated three days later when the United States dropped a plutonium implosion-type device code-named "Fat Man" on the city of Nagasaki, Japan. "

So, what have I learned from all of this? Never mess with a Fat Man. Never.
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Re: "Exoplanets" Discussion (#786)

Postby Kulantan » Mon Aug 30, 2010 12:23 pm UTC

chrth wrote:
oddy wrote:Also: why enrich uranium? I thought H-bombs were more powerful?


I may be misremembering, but I believe H-bombs are two- or three-stage detonations. I think you need an initial fission reaction to create the fusion reaction. I think. (Did I qualify that enough?)

Needs more google.
Summary: "[the standard design] employs hydrogen fusion to generate neutrons, in most applications the bulk of its destructive energy comes from uranium fission, not hydrogen fusion."
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Re: "Exoplanets" Discussion (#786)

Postby DragonHawk » Mon Aug 30, 2010 1:02 pm UTC

Roivas wrote:I am somewhat surprised that a science fiction writer, though he hasn't done many books, could say that something will never happen.

Read more closely. He doesn't say it won't happen. He says that there is no currently foreseeable technology which would make it viable.
Roivas wrote:We can instantly communicate with one another from one side of the planet to the other right now...

No, we can't. We can *nearly* instantly communicate with one another from one side to the other right now. The speed of light still impacts even terrestrial communications. And as soon as you go to geo-sync orbit (sat telecom), the delay becomes quite noticeable for real-time communications. On an interplanetary scale (let alone interstellar), geo-sync orbit isn't even leaving our backyard.

The thing so many people having trouble understanding is the scale involved in space. ("Space is 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's, but that's just peanuts to space." Douglass Adams) It's quite staggering, which is what all of Stross's math is about.
Roivas wrote:We're going to colonize any viable planet we can find. It just isn't going to be quick. Like the comic says, we're probably not going to do it ourselves, but we might live just long enough to see the first ships leave earth only to fly straight into a black hole or something.

The difference between "science fiction" and "fantasy" is that you don't get to say "or something".

As Stross says, if you want to wave a magic wand, go right ahead. That's useful for speculation on human culture and dynamics, or just for telling a good story. But when it comes to envisioning a viable propulsion system, you need to be a bit more concrete.
-----
EdgarJPublius wrote:... Project Orion has quite a few advantages. But for interstellar travel the upshot is that an orion-craft would be capable of reaching nearby stars within a human lifetime

According to the always-reliable Wikipedia, 300,000 tons of nuclear material would be able to accelerate to 3.3% c. So double that -- you need to decelerate. 600,000 tons. I can't find convenient figures for how much nuclear material is used in a weapon or power plant, but I know 600,000 tons is a *lot*. The largest seagoing vessel ever built by man weighed roughly that much (gross), and it didn't need to get into orbit. (I also don't know if that includes reaction mass. If it doesn't, you're well and truly screwed, so let's assume it does.) Closest known star to Sol is roughly 4 light-years away. So roughly 120 years. For something which may or may even be possible to build, and which would consume a staggering amount of fuel.

Again, not impossible, simply not viable.
Last edited by DragonHawk on Mon Aug 30, 2010 1:04 pm UTC, edited 1 time in total.
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Re: "Exoplanets" Discussion (#786)

Postby SpringLoaded12 » Mon Aug 30, 2010 1:03 pm UTC

Eebster the Great wrote:Brilliant. Of course, no explanation is given as to why we should look for destinations decades before the method of travel exists, but meh.

Because we don't want to blow a bunch of time looking for them once we already have the method of travel, as opposed to just leaving right away.
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Re: "Exoplanets" Discussion (#786)

Postby Palpatineli » Mon Aug 30, 2010 1:34 pm UTC

kudos for mentioning the 'real' Orion project (as opposed to the current petty substitute). And the alt-text...isn't this some poor guy in Marooned in Realtime?
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Re: "Exoplanets" Discussion (#786)

Postby melladh » Mon Aug 30, 2010 1:50 pm UTC

It's a fair point considering how people tend to say "oh to have been alive then-and-then when everything was set in motion / changed / whatnot", though if you actually had been alive at the time, you probably wouldn't have noticed any more than you do now.

Eebster the Great wrote:Alt text: "I'm just worried that we'll all leave and you won't get to come along!"


Also, this made me think of one of the LEXX movies...
You know it was my fault after all.
I knew we were leaving Brunnis. After all
the sun was dying. But we had this
farewell party and I did a few Kaboo
flowers and ... well, you know those Kaboo!
Boom! One too many and - whoo hoo!
You wake up four days later and the whole
planet's empty!
And then like the singing of a sad silent song
you awaken from slumber..
And everyone's gone.
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Re: "Exoplanets" Discussion (#786)

Postby Xentropy » Mon Aug 30, 2010 2:05 pm UTC

theduffman wrote:Correction: in slide 3, "cultures" should read "cultural" or "culture's"


No, it shouldn't. "...if one of earth's cultures advances its space program enough..." is grammatically correct. You seem to think it read something like, "...if one of earth's cultural advances is to space programs..."
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Re: "Exoplanets" Discussion (#786)

Postby BioTube » Mon Aug 30, 2010 2:19 pm UTC

DragonHawk wrote:According to the always-reliable Wikipedia, 300,000 tons of nuclear material would be able to accelerate to 3.3% c. So double that -- you need to decelerate. 600,000 tons. I can't find convenient figures for how much nuclear material is used in a weapon or power plant, but I know 600,000 tons is a *lot*. The largest seagoing vessel ever built by man weighed roughly that much (gross), and it didn't need to get into orbit. (I also don't know if that includes reaction mass. If it doesn't, you're well and truly screwed, so let's assume it does.) Closest known star to Sol is roughly 4 light-years away. So roughly 120 years. For something which may or may even be possible to build, and which would consume a staggering amount of fuel.

Again, not impossible, simply not viable.
Not at this moment, but if we're launching an extrastellar mission, then either this system is royally fucked or we've already developed a sufficient mining infrastructure on the asteroids to be able to divert such resources without massive economic disruption. Of course, there's also the possibility that staged bomb technology may advance to the point where only a very small amount of fissile material is needed per device(the Orion design would be useful just within the system, so it stands to reason it would be improved upon).
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Re: "Exoplanets" Discussion (#786)

Postby Siguy » Mon Aug 30, 2010 3:04 pm UTC

Sigh... Once again Randall recognizes that we need to make progress in space but misses what actually needs to be done... As a matter of fact Project Orion is hardly a capable mode of interstellar transportation, true, it would be more efficient than anything we have now, but just the same amount of research could develop something much better. And last time he suggested that the space elevator would be the way of the future, while in reality the space elevator would be extremely impractical in comparison to mass drivers, among other things...
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Re: "Exoplanets" Discussion (#786)

Postby philip1201 » Mon Aug 30, 2010 3:09 pm UTC

Maybe in the future we'll be capable of significant antimatter production. If one quarter of your ship's mass is antimatter, you can accelerate to 86.6% light speed. (when kinetic energy = rest mass energy). For slowing back down again, you need only a quarter again, so 37.5% of your ship needs to be antimatter. Including special relativity effects, they will have aged by such an amount as if they were traveling at the speed of light. So there would be several semi-habitable planets well within the range of a single generation of travelers.

Nuclear explosions are at least a hundred times less efficient, so even if the engine would be capable of perfectly using all available energy for thrust, you would need 99.983% of the ship's mass to be hydrogen.

So all we need to develop is large-scale antimatter production and we're good to go.
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Re: "Exoplanets" Discussion (#786)

Postby SirMustapha » Mon Aug 30, 2010 3:19 pm UTC

I'm waiting for the first comment to go "BUT THIS STRIP ISN'T MEANT TO BE FUNNY!!!!1".
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Re: "Exoplanets" Discussion (#786)

Postby chrth » Mon Aug 30, 2010 3:55 pm UTC

Siguy wrote:Sigh... Once again Randall recognizes that we need to make progress in space but misses what actually needs to be done... As a matter of fact Project Orion is hardly a capable mode of interstellar transportation, true, it would be more efficient than anything we have now, but just the same amount of research could develop something much better. And last time he suggested that the space elevator would be the way of the future, while in reality the space elevator would be extremely impractical in comparison to mass drivers, among other things...


I'm pretty sure the comic was not meant to be a policy directive.
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Re: "Exoplanets" Discussion (#786)

Postby rcox1 » Mon Aug 30, 2010 4:09 pm UTC

When people say things are not possible they are saying that things are impossible given the current social and economic structure. Pretty much there is no incentive to put the resources behind a project, or there is some taboo preventing it from being done. We say it is impossible to feed or care for everyone in the world, but that is mostly because there are certain taboos against certain technologies, and many believe that people who cannot generate sufficient input into the worlds economic system should not benefit from the output. It is possible, but we just don't want to do it.

We know technology will advance, and we know that philosophy will be reinterpreted. We have human made craft at the edge of or in intersteller space. Certainly some people in the 19th century would say this was impossible, especially those that continued to hang onto the biblical/Ptolemic interpretation that the earth was the center of the universe. There is no reason to believe that such changes in thought will not continue.

How this will happen I do not imagine. It may be in way that we do not expect, in the the sam way that a sewing machine or airplane works in an unexpected manner. There are great distances to travel. I would imagine that the first trip would take a very long time. I can imagine that it would be funded by being transmitted as an episode of big brother, 6 pioneers traveling through the cosmos, working, fighting, loving, with the requisite shower scenes to keep rating up.

"There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy."
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Re: "Exoplanets" Discussion (#786)

Postby art » Mon Aug 30, 2010 4:33 pm UTC

Interesting but why a comic? The illustration added no value
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Re: "Exoplanets" Discussion (#786)

Postby JudeMorrigan » Mon Aug 30, 2010 5:12 pm UTC

ijuin wrote: (Alpha Centauri A and B are too close together for planets in the habitable zone to have stable orbits over a multibillion-year time span, and Proxima Centauri is believed to have no Earth-mass or larger planets).


Could I trouble you for a cite on the first point? This is far outside my field, so I'll cheerfully admit to the possiblity that I've missed articles, but what I have seen seems to suggest the opposite. See:

http://iopscience.iop.org/0004-637X/576/2/982/

and

http://iopscience.iop.org/0004-637X/660/1/807/

for example.
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