0786: "Exoplanets"

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Re: "Exoplanets" Discussion (#786)

Postby neoliminal » Mon Aug 30, 2010 5:59 pm UTC

Prediction: This thread will not be very long. And this post will very likely be a page topper. (no edits)
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Re: "Exoplanets" Discussion (#786)

Postby davidwk » Mon Aug 30, 2010 6:03 pm UTC

My only question is, how many people are in that bed? In true xkcd fashion, he can't be alone under those sheets.

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Re: "Exoplanets" Discussion (#786)

Postby unus vox » Mon Aug 30, 2010 6:16 pm UTC

SirMustapha wrote:I'm waiting for the first comment to go "BUT THIS STRIP ISN'T MEANT TO BE FUNNY!!!!1".


Well, we already got our complaints that this strip A) doesn't have a strong punchline, B) is boring, and C) isn't practical or scientifically plausible, so we've pretty much hit upon all points of "discussion" already.
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Re: "Exoplanets" Discussion (#786)

Postby EdgarJPublius » Mon Aug 30, 2010 6:20 pm UTC

DragonHawk wrote:
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.


Project Orion was fully conceived in the 1950s and 1960s

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.


300kt Orion was actually an early design, the later, more Mature designs included flight profiles to nearby stars, Wiki mentions one such profile that was a forty-four year trip to Alpha Centauri, and one of the last Orion Designs before the PTBT put an end tot hat particular instance of research, was an eight million ton orioncraft, truly a flying city, and was considered to be a viable candidate for an interstellar generation ship.

And the wiki doesn't even really mention subsequent projects or ideas, such as Mag-pulse Orion which provides even better fuel fractions

Yes, that is a lot of nuclear material. But that's not exactly something we're short of. Current nuclear stockpiles could easily propel a number of relatively small missions to nearby star-systems, and if breeder type nuclear reactors become more widespread (which is likely already, especially with 4th gen reactors being built in the next ten years) there will be a virtually unlimited supply of nuclear material just here on earth.

But the real revolution starts with asteroid mining, when uranium mined and enriched in space can be used to construct Orion-craft in space for far cheaper than in the Earth's gravity well,a nd without the political problems of trying to detonate nuclear devices in Near-Earth space.
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Re: "Exoplanets" Discussion (#786)

Postby sinistercom » Mon Aug 30, 2010 8:54 pm UTC

As an aide, some of you should really learn a bit more about nuclear fission vs. nuclear fusion before posting.

But back to the topic.."space is really big". So very true. It takes a long time to travel through . Worse, the relativistic effects which make it seem like less time you're travelling only start be be significant as you get going pretty close to light speed. It takes a LOT of energy to move some useful mass to the velocity needed to cross space in a 'reasonable' time (for instance, a human life span), and the same amount to slow it down again. It even takes a lot of that famous antimatter to use for energy creation when it gets annihilated in its destruction during an encounter with matter. Right now, the amount of antimatter being created is counted in atomic particles, when it needs to be measured in tonnes. Using currently available technology, the creation of antimatter as a source of energy is amazingly inefficient. I' like to point out that this isn't as important as it seems at first. When considered as a method to store energy and transport it from a place where energy is cheap to a place where it's expensive, antimatter is very nice and compact. Where is energy cheap? In close vicinity to something like a star such as our own Sol. So, humanity could create massive antimatter factories orbiting Sol (and eventually, other stars), from which antimatter is shipper periodically, for such projects as interplanetary travel and eventually interstellar travel, as well as feats of materials refining and construction several orders of magnitude larger than anything which has so far been constructed on earth.

There are several manners of using stars and other massive bodies to gain velocity, such as 'gravity assist', and solar sails. The technology for both of these methods is within our grasp at this time.

The point of mentioning all of this is that while interstellar travel may not happen for hundreds of years, interplanetary travel may become rather commonplace. Don't be felled by ideas that humanity is forever stuck on this ball of mud, but reach for the stars...or planets.

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Re: "Exoplanets" Discussion (#786)

Postby DragonHawk » Mon Aug 30, 2010 10:07 pm UTC

unus vox wrote:
SirMustapha wrote:I'm waiting for the first comment to go "BUT THIS STRIP ISN'T MEANT TO BE FUNNY!!!!1".


Well, we already got our complaints that this strip A) doesn't have a strong punchline, B) is boring, and C) isn't practical or scientifically plausible, so we've pretty much hit upon all points of "discussion" already.

You forgot how xkcd is really going downhill lately.

-----

EdgarJPublius wrote:
DragonHawk wrote:
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.

Project Orion was fully conceived in the 1950s and 1960s

Again: Viable. Not "conceivable", not "possible", viable. Practicable, workable, can be realistically done.
EdgarJPublius wrote:300kt Orion was actually an early design, the later, more Mature designs included flight profiles to nearby stars, Wiki mentions one such profile that was a forty-four year trip to Alpha Centauri, and one of the last Orion Designs before the PTBT put an end tot hat particular instance of research, was an eight million ton orioncraft, truly a flying city ...

Your response to my concern about the viability of a craft using 600,000 tons of nuclear material is to posit an 8 million ton craft.

If I complain that a hot air balloon made out of lead will never fly, will your response be to posit a hot air balloon made out of depleted uranium?
... was considered to be a viable candidate for an interstellar generation ship.

Considered viable by who? On what basis? It sounds more like "This would work on paper" to me. Kind of like a space elevator. Yah, a wonderful thing -- if you can build it, and you can devote the world's resources to building it (and not, say, blowing it up because it makes a good target).
Yes, that is a lot of nuclear material. But that's not exactly something we're short of. Current nuclear stockpiles could easily propel a number of relatively small missions to nearby star-systems...

Citation needed. As I mentioned, I could find no convenient figures regarding nuclear material.
... there will be a virtually unlimited supply of nuclear material just here on earth.

And atomic power "will be too cheap to meter".

Any time I encounter a phrase like "virtually unlimited supply" I have to assume we're not dealing in realities, which tend to be rather cold, harsh, and stark.
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Re: "Exoplanets" Discussion (#786)

Postby richdun » Mon Aug 30, 2010 10:54 pm UTC

DragonHawk wrote:
EdgarJPublius wrote:
DragonHawk wrote:
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.

Project Orion was fully conceived in the 1950s and 1960s

Again: Viable. Not "conceivable", not "possible", viable. Practicable, workable, can be realistically done.
EdgarJPublius wrote:300kt Orion was actually an early design, the later, more Mature designs included flight profiles to nearby stars, Wiki mentions one such profile that was a forty-four year trip to Alpha Centauri, and one of the last Orion Designs before the PTBT put an end tot hat particular instance of research, was an eight million ton orioncraft, truly a flying city ...


You all seem to be missing the real reason Orion-type vehicles will never happen - generational apathy. Why spend all those resources on something hard now, when at the pace technology advances, the next generation or the generation after that will probably come up with something that will fly right past an Orion?

Besides, my new iDevice needs to be faster / smaller / shinier in 6 months.

EDIT: Fixed random loss of quote nesting.

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Re: "Exoplanets" Discussion (#786)

Postby EdgarJPublius » Mon Aug 30, 2010 11:32 pm UTC

EdgarJPublius wrote:
DragonHawk wrote:
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.

Project Orion was fully conceived in the 1950s and 1960s

Again: Viable. Not "conceivable", not "possible", viable. Practicable, workable, can be realistically done.


A mission to mars by an Orion powered craft was actually planned for sometime in the 1960s, but was cancelled due to the PTBT.
As I mentioned, there's really no aspect of Orion propulsion that is much more complex or technologically demanding than Saturn V. In fact, other than the propulsion units themselves, most of the technology is the same or is less complicated, and the propulsion units are technology that was more or less mastered by the 1950s.

There's no theoretical, technical or engineering challenge to be solved here, at this point it's just a matter of money and political barriers.

EdgarJPublius wrote:300kt Orion was actually an early design, the later, more Mature designs included flight profiles to nearby stars, Wiki mentions one such profile that was a forty-four year trip to Alpha Centauri, and one of the last Orion Designs before the PTBT put an end tot hat particular instance of research, was an eight million ton orioncraft, truly a flying city ...

Your response to my concern about the viability of a craft using 600,000 tons of nuclear material is to posit an 8 million ton craft.


I was responding more to your concerns about flight times than size.
The proposed 300kt orioncraft was conceived using figures for relatively early fission devices, later fusion driven Orioncraft were considered to be capable of traveling two to three times faster, or conversely, similar magnitudes smaller for the same payload and performance.
Likely the most developed Orion design was a 4kt (this is similar to the launch-mass of the Saturn V) interplanetary vessel for reaching Mars, but theoretical work was done on crafts as small as 900 tons as potential test vehicles with no real payload.

The 300kt vehicle is nothing more than a reference design, and an early reference design at that.

In practical reality, it's extremely unlikely that any orioncraft would be built or launched from Earth, and with in-orbit construction and material from asteroids, the actual mass of the craft becomes considerably less of a barrier (if nothing else, you could just hollow out a suitable asteroid, use the mined material for a pusher plate and off you go, just add nukes)


... was considered to be a viable candidate for an interstellar generation ship.

Considered viable by who? On what basis? It sounds more like "This would work on paper" to me. Kind of like a space elevator. Yah, a wonderful thing -- if you can build it, and you can devote the world's resources to building it (and not, say, blowing it up because it makes a good target).


Considered by the designers, on the basis of being feasible with the resources and technical capabilities of the time (lest we forget, Project Orion was not only considered possible, but viable and practical in the early 1960s)

Wiki cites Dyson's book "Project Orion: The True Story of the Atomic Spaceship"
But I've read similar statements in "The Curve of Binding Energy" by John McPhee about Ted Taylor

Yes, that is a lot of nuclear material. But that's not exactly something we're short of. Current nuclear stockpiles could easily propel a number of relatively small missions to nearby star-systems...

Citation needed. As I mentioned, I could find no convenient figures regarding nuclear material.


Going simply by the number of bombs stated int he Wiki page, interplanetary missions could be carried out using relatively small numbers of bombs, in the low thousands. Even 8 million ton Orion required only a thousand small bombs to reach orbit.
And small interstellar missions would require between tens of thousands to hundreds of thousands depending on mass and flight profile.

Tens of thousands would be on the same order of magnitude as the current individual nuclear stockpiles of Russia or the U.S., and most of the devices that have been decommissioned since the heights of the cold war have simply been disassembled rather than destroyed, so within short order, many times that number could be re-constructed.

This doesn't take into account relative bomb masses, as most Orion designs actually used small kiloton or sub-kiloton yield devices, and most military nuclear weapons are in the high kiloton to megaton yields, it's likely that disassembling the current stock of bombs could easily provide nuclear fuel for hundreds of thousands of orion propulsion units.

... there will be a virtually unlimited supply of nuclear material just here on earth.

And atomic power "will be too cheap to meter".

Any time I encounter a phrase like "virtually unlimited supply" I have to assume we're not dealing in realities, which tend to be rather cold, harsh, and stark.


'Virtually unlimited supply' may be a bit hyperbolic, however, raw nuclear material is, in actuality, rather abundant on Earth (especially when you consider Throium fuel that will be used in fourth generation plants) and considering that nuclear breeder reactors (most likely a combination of third and fourth generation plants that use each others waste to breed more nuclear fuel) are the only currently viable energy generating method that is environmentally safe, it's not a stretch to imagine that in the next hundred years, enriched nuclear material will be rather abundant.

You all seem to be missing the real reason Orion-type vehicles will never happen - generational apathy. Why spend all those resources on something hard now, when at the pace technology advances, the next generation or the generation after that will probably come up with something that will fly right past an Orion?


You could say this of any generational technology, and indeed, many have. it wasn't true for ocean-going ships either.
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Re: "Exoplanets" Discussion (#786)

Postby SirMustapha » Tue Aug 31, 2010 12:10 am UTC

DragonHawk wrote:You forgot how xkcd is really going downhill lately.


Down "hill"? It's already jumped into the valley, headfirst into the river and straight down to the bottom.

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Re: "Exoplanets" Discussion (#786)

Postby DVC » Tue Aug 31, 2010 12:21 am UTC

Well, I genuinely liked this one. It felt like a classic to me.

Maybe that's because I'm a visiting fellow with a group that actually do exoplanet research, but I feel like the guy in the comic.

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Re: "Exoplanets" Discussion (#786)

Postby clanders » Tue Aug 31, 2010 12:48 am UTC

I felt, during the buildup, that this comic had real potential. That's not something I feel with most xkcd comics these days. And then came the punchline, and all that buildup let me down.

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Re: "Exoplanets" Discussion (#786)

Postby StClair » Tue Aug 31, 2010 1:08 am UTC

Yeah, and when I was a kid (b. 1970), we were going to have permanent bases on the Moon and Mars by now.

Granted, we got the Internet instead, but let's just say I'll believe it when I see it.

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Re: "Exoplanets" Discussion (#786)

Postby Stanistani » Tue Aug 31, 2010 2:12 am UTC

SirMustapha wrote:
DragonHawk wrote:You forgot how xkcd is really going downhill lately.


Down "hill"? It's already jumped into the valley, headfirst into the river and straight down to the bottom.

I don't know what we would do without your insight and superior wisdom.
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Re: "Exoplanets" Discussion (#786)

Postby SirMustapha » Tue Aug 31, 2010 2:31 am UTC

Stanistani wrote:I don't know what we would do without your insight and superior wisdom.


Possibly try to and not take offence from someone's opinion on a webcomic for a start? That'd be a good start.

clanders wrote:I felt, during the buildup, that this comic had real potential. That's not something I feel with most xkcd comics these days. And then came the punchline, and all that buildup let me down.


The thing is, Randall does not know what to do with his ideas. He has those spare, assorted, loose ideas and thinks they're good enough to make a comic on their own. What's the "idea" here? Beret guy is enthusiastic about the future, I suppose? That's all we get here!! And there are too many problems with that:

1. Beret Guy may be the single most inconsistent and ill defined character in history. There is no defining trait, nothing peculiar, nothing particularly his in his personality that makes him identifiable; he NEEDS the beret so we notice who he is, because otherwise, he'd just be another faceless, empty character. Therefore, this speech simply comes out of the blue -- there's no context, no point, nothing that could justify it;
2. After all that, Randall fails to craft the scene into a joke. "OHH, BUT IT DOESN'T HAVE TO BE HUMOUROUS! THERE DOESN'T HAVE TO BE A PUNCHLINE!" I hear people cry. Well, what is the point then? There isn't going to be another comic continuing this one, the speech itself is pretty much pointless and highly arguable, and the "jokes" in the final panel wouldn't be out of place in a shitty brainless TV sitcom. There's nothing interesting or worthwhile going on, so the lack of good comedy or punchline only makes things worse;
3. Randall just doesn't know how to write. But then again, he knows how to draw pretty well, but actively avoids it. Maybe he can write well, but avoids it too? I find it hard to believe. Randall's work lacks fundamental writing skills: the dialogue is usually stilted and unnatural (it's not made to be so -- he tries to be casual and colloquial and fails horrendously), it lacks flow and rhythm, characterisation is atrocious, and so on and on. Randall needs someone who can take his ideas, filter them and shape them into a truly good read. He needs an editor. This has been pretty evident since a couple hundred comics ago.

To attack the most glaring problem directly: either he should drop his recurring characters or learn how to write them. The visual cues should be just an auxiliary aid for the reader, but they function as the character's primary mark for Randall. That is just no good. I mean, look at the previous comic: I don't think I ever remember seeing such a lame and boring Black Hat Guy; is that the same guy who cut people's arms off, pricked holes in condoms and killed people for completely gratuitous reasons? Is that the best he can do??

Randall, get out of my head an editor!

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Re: "Exoplanets" Discussion (#786)

Postby Stanistani » Tue Aug 31, 2010 3:00 am UTC

SirMustapha wrote:
Stanistani wrote:I don't know what we would do without your insight and superior wisdom.


Possibly try to and not take offence from someone's opinion on a webcomic for a start? That'd be a good start.


I am amused, not offended. I am surprised that someone of your caliber hasn't picked up on that.

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Re: "Exoplanets" Discussion (#786)

Postby unus vox » Tue Aug 31, 2010 3:59 am UTC

SirMustapha wrote:The thing is, Randall does not know what to do with his ideas. He has those spare, assorted, loose ideas and thinks they're good enough to make a comic on their own. What's the "idea" here? Beret guy is enthusiastic about the future, I suppose? That's all we get here!! And there are too many problems with that:

1. Beret Guy may be the single most inconsistent and ill defined character in history. There is no defining trait, nothing peculiar, nothing particularly his in his personality that makes him identifiable; he NEEDS the beret so we notice who he is, because otherwise, he'd just be another faceless, empty character. Therefore, this speech simply comes out of the blue -- there's no context, no point, nothing that could justify it;
2. After all that, Randall fails to craft the scene into a joke. "OHH, BUT IT DOESN'T HAVE TO BE HUMOUROUS! THERE DOESN'T HAVE TO BE A PUNCHLINE!" I hear people cry. Well, what is the point then? There isn't going to be another comic continuing this one, the speech itself is pretty much pointless and highly arguable, and the "jokes" in the final panel wouldn't be out of place in a shitty brainless TV sitcom. There's nothing interesting or worthwhile going on, so the lack of good comedy or punchline only makes things worse;
3. Randall just doesn't know how to write. But then again, he knows how to draw pretty well, but actively avoids it. Maybe he can write well, but avoids it too? I find it hard to believe. Randall's work lacks fundamental writing skills: the dialogue is usually stilted and unnatural (it's not made to be so -- he tries to be casual and colloquial and fails horrendously), it lacks flow and rhythm, characterisation is atrocious, and so on and on. Randall needs someone who can take his ideas, filter them and shape them into a truly good read. He needs an editor. This has been pretty evident since a couple hundred comics ago.

To attack the most glaring problem directly: either he should drop his recurring characters or learn how to write them. The visual cues should be just an auxiliary aid for the reader, but they function as the character's primary mark for Randall. That is just no good. I mean, look at the previous comic: I don't think I ever remember seeing such a lame and boring Black Hat Guy; is that the same guy who cut people's arms off, pricked holes in condoms and killed people for completely gratuitous reasons? Is that the best he can do??

Randall, get out of my head an editor!


My take on it was that Randall is very enthusiastic about the progression of current technology/astronomy (more so than the average person), and used today's comment to show his excitement for the possible future of space travel. Since I too am interested in those topics, I felt it was a nice sentiment. Maybe my standards are drastically lower than yours, or I don't require much humor out of every strip to find the comic enjoyable on the whole, but I don't really have a problem with what's going on. Randall wanted to draw attention to something, so he did. And already I feel like I've written too much on this dead horse.

I'm sorry you couldn't find a "point" in something that was a simple acknowledgment of cool technology. Then again, you're looking for characterization, compelling dialogue, and cohesion in a 3-panel web comic with stick figures.
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Re: "Exoplanets" Discussion (#786)

Postby Ool01 » Tue Aug 31, 2010 8:56 am UTC



Well, it will happen, but planets aren't necessary. I mean, for every square meter of real estate on Earth there are three billion cubic meters of unused material holding it up -- most of it molten magma or hot, solid iron. For every ray of sun hitting Earth two billion rays of sunlight are wasted into space. So it doesn't matter whether there are any Earth-like planets out there because by the time we reach them we won't be living on planets any more anyway. We'll be dismantling planets, creating habitats on which altogether quadrillions of people could live, not just billions.

Long before we reach the first neighboring stars more people will be living in orbit around planets or simply the Sun than on the surface of all the planets combined. The asteroid belt will be a greater boon to early space colonization than Mars, Venus, or Mercury. And those will come into their own only once we start taking them apart, not once we touch down on their surface and build bases there. That's just peanuts.

Gas clouds will probably be more interesting to us than planets once we have the technology to go that far...

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Re: "Exoplanets" Discussion (#786)

Postby SlyReaper » Tue Aug 31, 2010 10:10 am UTC

EdgarJPublius wrote:You could say this of any generational technology, and indeed, many have. it wasn't true for ocean-going ships either.


Well yes, but an ocean-going ship could reasonably be expected to reach its destination before a later generation ship overtook it. If you're going to be a pioneer who is the first to depart for the promised land in a high-risk voyage, you at least want to be the first to arrive. It would be a bit of an anticlimax to make such a journey, ready to create a new life on virgin soil, and then when you arrive, someone has already built a McDonalds and a shopping mall.
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Re: "Exoplanets" Discussion (#786)

Postby uncivlengr » Tue Aug 31, 2010 12:05 pm UTC

This seems like it'd make a better blog post than a comic.

Does anyone else find xkcd stick figures jarring when drawn at a scale different from that normally used? That third panel just looks weird.

It's funny that it goes from saying "they're first discovering...", "they're finding them..." which establishes that beret guy isn't involved in the process. By the last panel it's "we're discovering all these destinations", and he's all eager to do.... something. I'm curious as to where beret guy thinks he needs to be, or what he needs to be doing... sort of like I wonder what a sports fan thinks will happen if they miss watching a game.

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Re: "Exoplanets" Discussion (#786)

Postby theduffman » Tue Aug 31, 2010 12:17 pm UTC

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..."

oh, oops.
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Re: "Exoplanets" Discussion (#786)

Postby littlelj » Tue Aug 31, 2010 1:13 pm UTC

uncivlengr wrote:Lastly, there's no snooze button to hit when someone wakes you up.

Your aim is bad.
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Re: "Exoplanets" Discussion (#786)

Postby SirMustapha » Tue Aug 31, 2010 1:44 pm UTC

Stanistani wrote:I am amused, not offended. I am surprised that someone of your caliber hasn't picked up on that.


Yeah, "amused". It's easy to be "amused" on the Internet.

uncivlengr wrote:This seems like it'd make a better blog post than a comic.


Yes. You took the words right out of my fingers. It was a blog post, nothing more and nothing less, only barely disguised as a comic. Are my standards "too high" just for expecting a little more than that?

unus vox wrote:Then again, you're looking for characterization, compelling dialogue, and cohesion in a 3-panel web comic with stick figures.


And what's wrong with that? If you're a webcomic artist, you're expected to do much with little. That's the business, and no one said it's easy.

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Re: "Exoplanets" Discussion (#786)

Postby Eebster the Great » Tue Aug 31, 2010 1:51 pm UTC

SirMustapha wrote:Yeah, "amused". It's easy to be "amused" on the Internet.

U mad

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Re: "Exoplanets" Discussion (#786)

Postby EdgarJPublius » Tue Aug 31, 2010 3:35 pm UTC

SlyReaper wrote:
EdgarJPublius wrote:You could say this of any generational technology, and indeed, many have. it wasn't true for ocean-going ships either.


Well yes, but an ocean-going ship could reasonably be expected to reach its destination before a later generation ship overtook it. If you're going to be a pioneer who is the first to depart for the promised land in a high-risk voyage, you at least want to be the first to arrive. It would be a bit of an anticlimax to make such a journey, ready to create a new life on virgin soil, and then when you arrive, someone has already built a McDonalds and a shopping mall.



Unless faster than light propulsion is discovered and implemented, it's seems highly unlikely that any propulsion method based on our current understanding of physics will out-pace nuclear propulsion sufficiently for that to happen.

Let's take a proposed mission to alpha-centauri on an orion-craft that will take about 50 years.
In order for say, an anti-matter propelled craft that is three times faster than fusion-orion to reach alpha-centauri first, a method for generating and storing enough anti-matter for the trip and using it for propulsion would have to be discovered, engineered, tested, approved and then a suitable ship built, crew chosen and trained all within ten to twenty years. And even then, you won't arrive significantly sooner.

Once you get into the upper end of anti-matter propulsion (theoretically about .7-8c), then further generational advances run fast into diminishing returns, where relativity means that large increases in propulsive capability are required to gain only small increases in velocity.
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Re: "Exoplanets" Discussion (#786)

Postby art » Tue Aug 31, 2010 4:23 pm UTC

SirMustapha wrote:Randall, get out of my head an editor!


Maybe he should cut down to only 2 or even 1 comic per week? I doubt he's reading this very sentence, but I feel that comics like this one may have become more wholly satisfying with extra time and effort. I'd much rather some quality over these half-baked episodes we've been getting for a while now.

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Re: "Exoplanets" Discussion (#786)

Postby SlyReaper » Tue Aug 31, 2010 5:22 pm UTC

EdgarJPublius wrote:
SlyReaper wrote:
EdgarJPublius wrote:You could say this of any generational technology, and indeed, many have. it wasn't true for ocean-going ships either.


Well yes, but an ocean-going ship could reasonably be expected to reach its destination before a later generation ship overtook it. If you're going to be a pioneer who is the first to depart for the promised land in a high-risk voyage, you at least want to be the first to arrive. It would be a bit of an anticlimax to make such a journey, ready to create a new life on virgin soil, and then when you arrive, someone has already built a McDonalds and a shopping mall.



Unless faster than light propulsion is discovered and implemented, it's seems highly unlikely that any propulsion method based on our current understanding of physics will out-pace nuclear propulsion sufficiently for that to happen.

Let's take a proposed mission to alpha-centauri on an orion-craft that will take about 50 years.
In order for say, an anti-matter propelled craft that is three times faster than fusion-orion to reach alpha-centauri first, a method for generating and storing enough anti-matter for the trip and using it for propulsion would have to be discovered, engineered, tested, approved and then a suitable ship built, crew chosen and trained all within ten to twenty years. And even then, you won't arrive significantly sooner.

Once you get into the upper end of anti-matter propulsion (theoretically about .7-8c), then further generational advances run fast into diminishing returns, where relativity means that large increases in propulsive capability are required to gain only small increases in velocity.


Why go to alpha centauri? As far as I'm aware, it's not thought to have any planets. I think the closest star which is known to have planets is about 20 light years away, which will take an orion craft 200 years to reach*. And even that is only guaranteed to have gas giants (although they'd probably have rocky moons if our own gas giants are any indication). That's plenty of time to prefect a faster propulsion system and overtake the pioneers. Maybe they'll moon the orion craft and pull silly faces out the window as they fly past.

*In reality, we'd want to be damn sure there was an earth-like planet with oxygen atmosphere, liquid water, decent gravity, etc before setting off, so the nearest destination may be even further away than that.
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Re: "Exoplanets" Discussion (#786)

Postby @dmin » Tue Aug 31, 2010 6:45 pm UTC

All I can think of is this,

I'm sorry, Randall. I'm afraid I can't do that.

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Re: "Exoplanets" Discussion (#786)

Postby Tath » Wed Sep 01, 2010 12:12 am UTC

If one observes closely, one notices it was not, in fact, the alarm clock that woke the sleeper in the first place, but the beret-shod technological fanatic.






THE SLEEPER HAS AWAKENED!

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Re: "Exoplanets" Discussion (#786)

Postby Stanistani » Wed Sep 01, 2010 1:37 am UTC

Ool01 wrote:


Well, it will happen, but planets aren't necessary. I mean, for every square meter of real estate on Earth there are three billion cubic meters of unused material holding it up -- most of it molten magma or hot, solid iron. For every ray of sun hitting Earth two billion rays of sunlight are wasted into space. So it doesn't matter whether there are any Earth-like planets out there because by the time we reach them we won't be living on planets any more anyway. We'll be dismantling planets, creating habitats on which altogether quadrillions of people could live, not just billions.

Long before we reach the first neighboring stars more people will be living in orbit around planets or simply the Sun than on the surface of all the planets combined. The asteroid belt will be a greater boon to early space colonization than Mars, Venus, or Mercury. And those will come into their own only once we start taking them apart, not once we touch down on their surface and build bases there. That's just peanuts.

Gas clouds will probably be more interesting to us than planets once we have the technology to go that far...

I think that
  1. This is one of the best posts in the thread.
  2. It's a great plot for a horror story, featuring aliens that arrive in our solar system, ready to rearrange it as described above.

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Re: "Exoplanets" Discussion (#786)

Postby EdgarJPublius » Wed Sep 01, 2010 2:13 am UTC

SlyReaper wrote:
EdgarJPublius wrote:
SlyReaper wrote:
EdgarJPublius wrote:You could say this of any generational technology, and indeed, many have. it wasn't true for ocean-going ships either.


Well yes, but an ocean-going ship could reasonably be expected to reach its destination before a later generation ship overtook it. If you're going to be a pioneer who is the first to depart for the promised land in a high-risk voyage, you at least want to be the first to arrive. It would be a bit of an anticlimax to make such a journey, ready to create a new life on virgin soil, and then when you arrive, someone has already built a McDonalds and a shopping mall.



Unless faster than light propulsion is discovered and implemented, it's seems highly unlikely that any propulsion method based on our current understanding of physics will out-pace nuclear propulsion sufficiently for that to happen.

Let's take a proposed mission to alpha-centauri on an orion-craft that will take about 50 years.
In order for say, an anti-matter propelled craft that is three times faster than fusion-orion to reach alpha-centauri first, a method for generating and storing enough anti-matter for the trip and using it for propulsion would have to be discovered, engineered, tested, approved and then a suitable ship built, crew chosen and trained all within ten to twenty years. And even then, you won't arrive significantly sooner.

Once you get into the upper end of anti-matter propulsion (theoretically about .7-8c), then further generational advances run fast into diminishing returns, where relativity means that large increases in propulsive capability are required to gain only small increases in velocity.


Why go to alpha centauri? As far as I'm aware, it's not thought to have any planets. I think the closest star which is known to have planets is about 20 light years away, which will take an orion craft 200 years to reach*. And even that is only guaranteed to have gas giants (although they'd probably have rocky moons if our own gas giants are any indication). That's plenty of time to prefect a faster propulsion system and overtake the pioneers. Maybe they'll moon the orion craft and pull silly faces out the window as they fly past.

*In reality, we'd want to be damn sure there was an earth-like planet with oxygen atmosphere, liquid water, decent gravity, etc before setting off, so the nearest destination may be even further away than that.


Recent speculation indicates that terrestrial planets could form in stable orbits within the Alpha Centauri system. It hasn't been considered a strong contender for planetary searches because previously, it was thought that there weren't any stable orbits such planets could occupy in the system.

As far Gliese 581, there's no particular reason for early missions to be launched in that direction, neither of the 'prime candidate' planets are particularly suitable for human exploration, and it's likely that new planetary detection techniques will detect more suitable planets in closer systems.

Towards that end, a number of candidates exist within ten to fifteen lightyears (off the top of my head, Epsilon Eridani is rather promising and only 10 light years away)

Also, as Ool01 mentions, it's possible that habitable planets won't even be necessary for future colonization, orbital habitats and paraterraforming could easily provide livable environments in an extremely wide variety of stellar systems. I mean, if a starship was able to provide a livable, self-contained environment for the forty, fifty or two hundred years it takes to reach a nearby-system, it might as well be a self-sufficient colony already.


I'm hesitant to discuss timelines for technology further than fifty years in the future, so I don't want to say explicitly that it's impossible for anti-matter to be developed as a method of propulsion before even a distant future Orion mission could reach it's destination, but the gap between the two is more than simply generational. Orion and other methods of Fusion propulsion are more or less 'current' technology, the components all exist, the physics have all been analyzed and understood, and if we started tomorrow, a working inter-planetary vessel could in all likelihood be launched within the next ten years, and an interstellar vessel just a few decades after that.
Whereas antimatter is poorly understood, no methods of generating such large quantities exist or have even been theorized that don't require on the order of quadrillions of dollars and/or billions of years, and storage of any quantity of anti-matter for any period of time longer than minutes is all but theoretically impossible.
Furthermore, anti-matter, unlike nuclear fission/fusion, fundamentally can not be used for generating power, only for storage (and in all likelihood, not even especially efficient or long term storage), so there's no particular drive to make the leap between generating relatively small amounts for research and imaging to generating and storing enough for a starship.

Even though we're likely talking about a period of time farther in the future from now than the first man on the moon was from the first powered flight, I find it extremely unlikely that anti-matter propulsion will be any where near sufficiently plausible soon enough that it becomes a serious concern for any future planned interstellar Orion mission. The difference between the levels of technology required is simply far too great. I'd almost be more willing to believe that faster than light travel could short-cut interstellar Orion than that anti-matter propulsion could do it, if only because the barriers to feasible FTL are unknown, while the barriers to anti-matter are known and extremely daunting.

EDIT: did someone mess with my quotes in the last few posts? I went through and fixed them but I seem to remember them all working when I posted those comments.
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Re: "Exoplanets" Discussion (#786)

Postby Josephine » Wed Sep 01, 2010 7:31 am UTC

Alpha centauri should have potentially earthlike planets. Excerpt:
Spoiler:
To study planet formation around Alpha Centauri B, the team ran repeated computer simulations, evolving the system for the equivalent of 200 million years each time. Because of variations in the initial conditions, each simulation led to the formation of a different planetary system. In every case, however, a system of multiple planets evolved with at least one planet about the size of Earth. In many cases, the simulated planets had orbits lying within the habitable zone of the star.
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Re: "Exoplanets" Discussion (#786)

Postby RabbitWho » Wed Sep 01, 2010 11:32 am UTC

It's funny because the morning before I read this my phone woke me and I set it to snooze. The spelling of snooze seemed so strange to me that I made a mental note to set my phone back to English once I woke up.

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Re: "Exoplanets" Discussion (#786)

Postby Pez Dispens3r » Wed Sep 01, 2010 11:39 am UTC

RabbitWho wrote:It's funny because the morning before I read this my phone woke me and I set it to snooze. The spelling of snooze seemed so strange to me that I made a mental note to set my phone back to English once I woke up.

Crap, I thought I was the only person who did this.
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Re: "Exoplanets" Discussion (#786)

Postby ijuin » Wed Sep 01, 2010 7:19 pm UTC

nbonaparte wrote:Alpha centauri should have potentially earthlike planets. Excerpt:
Spoiler:
To study planet formation around Alpha Centauri B, the team ran repeated computer simulations, evolving the system for the equivalent of 200 million years each time. Because of variations in the initial conditions, each simulation led to the formation of a different planetary system. In every case, however, a system of multiple planets evolved with at least one planet about the size of Earth. In many cases, the simulated planets had orbits lying within the habitable zone of the star.


Note that it says they followed the simulation for a 200 million year span. I have concerns about the stability of the orbits over a five billion year span. After all, the Late Heavy Bombardment in our own solar system is tenetively attributed to the breakup of a small protoplanet or several large asteroids about 500-650 million years after our solar system's formation.

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Re: 0786: "Exoplanets"

Postby Qaanol » Wed Jun 20, 2012 4:54 am UTC

The new comic 1071, being named “exoplanets.png”, has broken comic 786, which was also named “exoplanets.png”. The original comic 786 image is attached:

exoplanets.png
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Re: "Exoplanets" Discussion (#786)

Postby Pfhorrest » Wed Jun 20, 2012 8:44 am 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.

Wouldn't there be some way of giving up a lot of that energy to the star you're aiming for and possibly some of its planets; the opposite of a slingshot maneuver? Of course you'd need some delta-v to steer to accomplish that maneuver but I imagine that's got to be less than would be required to slam on the space breaks.
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Re: 0786: "Exoplanets"

Postby Yablo » Wed Jun 20, 2012 9:06 am UTC

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


So, the Alt text I got was "Planets are turning out to be so common that to show all the planets in our galaxy, this chart would have to be nested in itself--with each planet replaced by a copy of the chart--at least three levels deep."

Also, when I right-clicked to View Page Info with Firefox (in order to cut and paste this text because I'm lazy), I noticed it was referred to as "Associated Text" which may or may not be a better term than "Alt Text", "Mouse-over Text", etc ...

*shrug* I don't know. I don't really care for it.
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Re: 0786: "Exoplanets"

Postby albannach » Wed Jun 20, 2012 9:19 am UTC

We know nothing about what's on any of them


Strictly speaking, this is not true. With transiting planets, we can get the atmosphere's spectrograph by comparing the star's colour when the planet is behind the star, and when it is infront of the planet. This is now routine, and lets us determine the planet's atmosphere's composition.

It is just possible to do the same as the planet emerges from behind the star's limb. This will include light reflected off the planet's surface (its albedo), which allows us to determine the surface composition (or at least the opaque lower atmosphere).

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Re: 0786: "Exoplanets"

Postby Max™ » Fri Jun 22, 2012 9:24 pm UTC

Qaanol wrote:The new comic 1071, being named “exoplanets.png”, has broken comic 786, which was also named “exoplanets.png”. The original comic 786 image is attached:

exoplanets.png

I had to sign up to reference this "accident" and this comic:
Image

Given the number 786 cited in the 1071 comic and how much Randall loves his xkcd injokes I must conclude:

It's so meta even this accident
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Re: 0786: "Exoplanets"

Postby Whizbang » Thu Aug 23, 2012 5:19 pm UTC

Has anyone done the math on sending an asteroid full of frozen bacteria to any of these systems, as a sort of Seeding Program? You know, not in preparation of colonization, but just to, perhaps, ensure that life continues on after us, just in case we are the only life in the universe.

Just thinking long-term here. If we never achieve intersolar travel, at the very least we should send microbial life questing out to the stars. Hitting a specific planet might be impossible, but if we send enough out, we might get lucky.


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