Sad Trombone Exoplanet Reality Check | Hacker News Reader

Sad Trombone Exoplanet Reality Check

antipope.org

151 pointscstross195 comments

When I was a boy in the Soviet Union in the late 80's, I picked up a book on computers. It was targeted towards children, and talked about a lot of different components and ideas from bits and bytes to RAM to networking, and interesting applications like barcodes.

I remember my mind being blown by barcodes. But the idea seemed far-fetched and unrealistic. To put a barcode on EVERY single item in the grocery store? That would take decades to implement!

Then we emigrated to Canada and I was shocked to see it was already in place (and must have been for a while).

Maybe this isn't the best example of tremendous human achievement but it taught me to not take for granted what is unrealistic and how quickly humanity could achieve it if we put our minds to it.

With apologies to Cliff Stoll and his magnificent brain, let's not forget a pretty common perspective on the Internet from 1995: http://europe.newsweek.com/clifford-stoll-why-web-wont-be-ni...

Space exploration and rocketry is not cheap, and requires new innovation. Only SpaceX is doing anything on that front. But if humanity set getting to Proxima Centauri as a goal, I have no doubt we could achieve at least kicking off a single-generation journey within my lifetime (ie sub-80 year journey time in the next 80 years)

Effectively, what we need to do is to get some kind of space resource rush going. Similar to what fueled the likes of the East India Company.

Yes, if only Mars were already settled and we could exploit the people there.

The question has always been what resource, with 3He and platinum being the two main contenders.

Otherwise, it could be like coal mining in Antarctica, or manganese module mining from the deep seafloor - technically possible, but not profitable, and certainly not enough for a new EIC.

> what resource

Ideas. That crazy nuclear experiment you want to run? Fat chance in Montana. But on the far side of Mars? Why not.

Why would that interest a potential East India Company-like organization?

The best I could come up with would if be it leads to a fuel production source, like the satellite at the end of Heinlein's "Blowups Happen". But we know of no such thing, nor do the economics seem to work out.

There is no "far side" of Mars. It's not tidally locked, to either the Sun or Earth.

"Far side" relative to Mars's principal human installations, not to the Earth.

You still haven't addressed why there are "principal human installations" on Mars in the first place, much less why they are only on one side of the planet, or why the experiments require local human involvement.

You mean a private company that can legally declare interplanetary war?

Or just tell the government there's oil on Titan. ;)

There's lots of liquified natural gas on the surface of Titan.

Close enough, wouldn't you say? There are slightly heavier molecules to be found there as well.

And create addicts of the most advanced and ancient civilisation on the planet.

In space, if you have a rock, you're among the ... well, let's see.

There's about 1,000 atoms per cm^3 of interplanetary space. Let's say you've got 1 kg of silicate rock -- SiO4. That's 4 parts oxygen (atomic weight 16) to 1 part silicon (atomic weight 14).

A kilogram is about 10^30 atomic masses. So we need 10^27 cubic centimeters, which works out to about 100 million km^3.

The Earth has a volume about 16,000 times larger -- which means at the average density of interstellar space, there would be about 16,000 of those rocks you have in hand, or 16 tonnes of matter. Rather than the six thousand billion billion tonnes of matter actually in the Earth.

We've met the space resource rush and it is us.

I have vague memories of soviet grocery stores in late 80s/early 90s, but they certainly didn't have too much items to begin with.

Humans are capable of incredible achievements. But it is unlikely we will achieve interstellar travel any time soon. We are too busy fighting wars (relicts of the stone age, really), improving our advertising technology, and just generally slacking around and looking good in the process.

Thinking is hard. It's easier not to think too much.

Humans were busy fighting wars, improving its advertising technology, and just generally slacking around when the internet was being born as well.

It only takes a very tiny portion of this world's 7 billion people to be smart and motivated enough to create a breakthrough for the entire planet.

That said, interstellar travel is an order of magnitude more difficult, so I agree it won't be happening very soon.

I'm surprised that the internet so often comes up in the context of humanities great technical achievements.

Don't get me wrong, a seamlessly interconnected network of computers has changed society and our lives tremendously.

Technically speaking, it was not that remarkable of an achievement though. We already had some forms of remote communication for quite a while (telegraph, telephone, radio).

With the rise of computers, connecting them was bound to be the next step, and not that much of a challenge as far as hardware and technology goes.

The actual (technical) achievement was the computer.

Pretty much all of the early rocket and space development was the result of WWII and the Cold War.

And pretty much all space development stagnated as soon as the interests of space exploration diverged from the applications useful for military.

When we/they wanted to put the first satellites in orbit, that shit was serious and got done with extreme speed, due to obvious implications of nuclear-tipped ICBMs. After that we got excessive investments in spy satellites and communications technologies, which resulted in civilian applications such as GPS and satellite TV, but practical interest (and founding) for anything beyond geostationary orbit pretty much stopped after the initial dick-measuring propaganda competition.

It's true we are unlikely to achieve interstellar travel any time soon but this has nothing to do with the fact that there are wars and everything to do with the laws of nature.

If anything, wars tend to accelerate technological progress.

war spending rarely steps in the way of space spending. liberals hate the space program the most. they would much rather spend the money on healtcare and education. war as it turns out, has a lot of interest in space spending.

Healthcare and education seem like great ways to increase the innovation we need for space travel.

i dont think so. its not research. healthcare is perhaps the worst investment possible in the sense that we are just throwing the largest chunk of our budget towards old people who are going to die anyways. 2 trillion of the stuff and growing faster than our income, meanwhile we spend about 12 bil on NASA in total.

education? have no idea where that spending is going to

With apologies to Cliff Stoll and his magnificent brain, let's not forget a pretty common perspective on the Internet from 1995: http://europe.newsweek.com/clifford-stoll-why-web-wont-be-ni....

You know, he really wasn't wrong. Online news hasn't really replaced newspapers; it's just displaced them.

During the golden age of newspapers, when a city might have a dozen different newspapers, every single one of those newspapers was an explicitly biased propaganda rag. The newspaper boom was an era when newspapers served as easily consumable combinations of news and entertainment designed to sell advertising space. The definitive heyday of newspapers was the era of yellow journalism. The business model of Buzzfeed, Huffington Post, Gawker, or Breitbart would be clearly recognizable to Hearst and Pulitzer.

When TV and radio shrunk the newspaper industry, this gave way to local monopolies (or duopolies) of center-left and occasionally center-right newspapers that pretended to be unbiased, and eventually an oligarchy of center-left television networks. This left a large market opportunity, and as soon as the FCC repealed the Fairness Doctrine, right-wing talk radio emerged. CNN proved the viability of cable news but kept the same center-left, pretend-impartial bias as the networks, so Fox News erupted on the scene.

The supposed integrity and ethics of journalism, so far as they even existed, were a luxury that newspapers could afford because the decline of the newspaper industry led to monopolies. Just like Bell Labs was a luxury borne from the telecommunications monopoly of the mid-20th century.

If you have a monopoly on the news, you have a vested interest in marketing yourself as unbiased (in order to have the largest addressable market). You do not have a vested interest in being unbiased. Aside from the natural beliefs and biases of the journalists themselves, there is also a structural bias towards sensationalism and another structural bias in favor of the establishment (or else you lose access). Even the desire to appear unbiased introduces a bias--unbiased coverage one disagrees with looks like biased coverage, so mechanisms like bias towards the center and "he said/she said" reporting about matters of fact show up.

The 20th century golden era of journalism was an illusion. For all the faults of Internet journalism, breaking the monopoly alone was a public service. It's no longer possible for a sitting President to literally expose himself to journalists when he gets annoyed at their questions as Lyndon Johnson once did.

That's a relatively good history, and raises some good points, but leaves out a few elements and gets some timing wrong.

The rise of beat journalism and "modern journalistic standards" came with the arrival of the telephone (early 1920s), and the ability for reporters to, well, phone it in. (The emergence of the telegraph and the news wire had an earlier tremendous impact, though largely on the ability for news to move between cities rapidly, if not always accurately -- I've followed some 1890s stories and noted the discrepencies ranging from misspelled names to misattributed identities: https://redd.it/39w8u4).

WNYC's On the Media covered "The History of Beats" in a segment: http://www.wnyc.org/story/history-beatss/#transcriptContent

Beat reporting permitted these papers to develop people who had expertise. Writer Jacob Riis who's really known for his photographs was also a print reporter who made poverty on the Lower East Side his beat.... [H]e knew everything about what was going on. And so it gave authority to the newspapers. This is also important to the transition that is going on in journalism at that time. Before that journalism was an immature business. It was very partisan, often supported by political parties, and a failed politicians became editors and successful editors became politicians it was two sides of the same coin. But when newspapers established their economic independence by writing copy that people wanted to buy and if people bought a newspaper you could sell pages of advertising. In conjunction with that was enormous technological change. Paper that was strong enough to go through printing presses at incredible speeds. The telegraph delivering news from around the world. And the beat was part of that. It brought news that was reliable to the front page of the newspaper based on some form of expertise.

I'd argue that the two World Wars, particularly the second, also created the institution of the modern paper and news organisation.

Radio was starting to emerge by the 1920s, but was still pretty immature. Television wasn't a force until the 1950s, and only late within that period. Remember that the Kennedy-Nixon debates (1960) were the first time a US presidential debate was covered live. This was also the time of the first satellite links -- and they were part-time, occasional links, not part of broadcast transmission. That technology didn't mature until the late 1990s. NPR's Renee Montaigne discusses how NPR correspondents, especially overseas, would jump through hoops to get tape to the Washington studio over the course of days (and yes, physical tape), particularly from remote locations such as Africa.

As for balance and integrity, Google's Ngram Viewer is a useful tool for exploring the frequency of words and phrases in general usage. The phrase "journalistic integrity" started emerging in the 1960s, growing about fivefold through the early 2000s, at a nearly linear rate. Other related terms ("journalistic balance" and "impartial journalism") are less pronounced.

https://books.google.com/ngrams/graph?content=journalistic+i...

The terms "corporate media", "left-wing media", "liberal media", and "establishment media" appear about this time -- the first to dominate the latter, with corporate far more prominent than liberal, in Google's corpus.

https://books.google.com/ngrams/graph?content=left-wing+medi...

Stoll has a much more mixed record on that than he's given credit for. Some boners, some accurate predictions.

1. Replacing human teachers is very hard. Look at the whole MOOC space.

2. I'll give him mixed status on books and newspapers. Technologically, it's possible to have electronic books and papers. Some of the displays and devices are pretty good. Almost all the software sucks, and the business models are atrocious. (I'm saying this as someone who's got a few thousand, each, of articles and books on a tablet for research and organisation.) The best business model, from a user perspective, is free content. The content itself is a mess, and I find that older materials (archived books and content at Archive.org, most from 1924 and before), published books (I make heavy use of several pirate book sites for research materials, as well as libraries and more traditional sources), and scientific papers (Sci-Hub) tend to have much higher quality content than all but the very best online sites.

Hal Varian (now Google's chief economist) wrote some quite good essays regarding online content in the late 1990s. While the Web is catching up, his point was that at the time, the Web's not-insubstantial page count was the equivalent of perhaps a modest, and quite poorly-curated, local library, if that. Mind that the business models are still far behind, and I think completely flawed: information is a public good, information access wants to be free.

3. Electronic commerce is a mess. It's consistently underperformed booster's estimates. It comes with terrible compromises of privacy, security, and surveillance. The experience is pathetic (unfortunately it's also frequently made the brick-and-mortar experience pathetic). It's fraud-ridden for both buyers and sellers. Payment processors' practices are capricious.

The Web remains useful for information and communications, it's a poor fit for commerce. Almost all the actual technology is tremendously frustrating, for users, vendors, providers, and engineers (I've worn all hats).

Stoll may have missed a few points, but he hit a number of others smack on the head. That's far better than many "futurists", particularly in even considering downsides and negatives.

> it's a poor fit for commerce

And yet, it's becoming de facto.

With a hell of a lot of pounding of square pegs into round holes.

The places ecommerce does and doesn't work well are quite specific and pretty well structured. Helps a lot to not read what the boosters are saying.

Or at least supplement that with other P's of V.

There's a whole host of "impossible" things that have been achieved: https://en.wikiquote.org/wiki/Incorrect_predictions

In 1957 Lee de Forest, father of the vacuum tube, deemed all space travel impossible - six months later, Sputnik orbited Earth. https://news.google.com/newspapers?id=KXhfAAAAIBAJ&sjid=my8M...

Steam trains were deemed impossible, because people's heads would fall off at that speed.

Finally: No Wireless. Less space than a nomad. Lame.

There's also a whole host of "impossible" things that haven't been achieved - time travel, faster-than-light travel, heck, even lunar colonization.

Sometimes, you just have to wonder whether it's even possible to break our current understanding of physics.

> lunar colonization.

The other things are impossible or might as well be, at least based on our current understanding of physics. The reason lunar colonization hasn't happened is not because it is impossible but because there's just no compelling reason for us to colonize the Moon yet. Nothing is preventing us from doing it other than not having a good reason to expend the capital and do the engineering work.

If we find something on the Moon that we need and can't get on Earth, we'll colonize the Moon. Really, the only somewhat good reasons I've heard for doing it at all is as a test run for more ambitious things like Mars.

Otherwise, the Moon is just a dead, almost completely airless worldlet that is not really all that interesting beyond scientific exploration.

The moon is extremely interesting because it is seismically dead. Its core has cooled and solidified. This means we can create with existing technology all sorts of useful industrial structures hidden away below 500 miles of basalt. From that perspective, the moon offers a relatively cheap insurance policy for humanity. The moon could house hundreds of billions of humans, immense defensive weapon systems, and in uninteresting enough resource wise to be passed over by anyone else out there

0. The Moon is not "seismically dead."

1. The Moon has not cooled and solidified.

2. We do not have existing technology to create massive underground Moon factories. It would be unbelievably difficult, even on Earth, to drill 500 miles into basalt, let alone doing so in mostly vacuum. This is not an unsolvable problem, mind you, but probably more difficult than you are thinking and definitely more difficult than burying some prefabricated modules beneath a few meters of lunar regolith.

3. There are about 7.3 billion humans alive right now. We have no (current) need to put hundreds of billions of humans anywhere. And the Moon could not support such a population even under the absolute best colonization schemes unless we genetically engineer humans to be smaller and use fewer resources. Again, not impossible, but not possible with current technology and may not be morally correct even if it was possible.

4. Why would we need weapons systems on the Moon? We currently have treaties against militarizing outer space. You're not seriously proposing that as a defense against alien invasion are you? If extraterrestrial life exists and possesses the technology to cross interstellar space and is belligerent, something tells me they would not have any problems defeating us even if we did bury ourselves under the Moon.

Again, the Moon is simply not very interesting beyond a trial run for more complex colonization schemes for a place like Mars. If we do find some reason to colonize the Moon, we could do so fairly easily - probably within 10-25 years. IMHO, the biggest problem we would face is just getting stuff there to support people.

I am very sympathetic to the insurance argument, but for different reasons. An asteroid/comet collision is much more likely to trigger the need for that than any alien invasion. But even then, depending on the size of the impact object, being on the Moon may not do us much good if the impact kicks up enough debris.

But what you are proposing is pretty far beyond what we are currently capable of. Not impossible but certainly not easy or likely within the next century.

[0] https://en.wikipedia.org/wiki/Quake_(natural_phenomenon)#Moo...

[1] https://en.wikipedia.org/wiki/Internal_structure_of_the_Moon...

[3] http://www.census.gov/popclock/

[4] https://en.wikipedia.org/wiki/Outer_Space_Treaty

> We currently have treaties against militarizing outer space

Note that the United States is effectively repealing its obligations under the OST [1]. It was a silly assumption to begin with. Where value be it will be gotten from.

[1] https://www.congress.gov/bill/114th-congress/house-bill/2262...

??? "(Sec. 403) It is the sense of Congress that the United States does not, by enactment of this Act, assert sovereignty or sovereign or exclusive rights or jurisdiction over, or ownership of, any celestial body."

> facilitate the commercial exploration for and commercial recovery of space resources by U.S. citizens;

> promote the right of U.S. citizens to engage in commercial exploration for and commercial recovery of space resources free from harmful interference, in accordance with such obligations and subject to authorization and continuing supervision by the federal government.

> A U.S. citizen engaged in commercial recovery of an asteroid resource or a space resource shall be entitled to any asteroid resource or space resource obtained, including to possess, own, transport, use, and sell it according to applicable law, including U.S. international obligations.

As always, with government documents, you have to read carefully. Mind you, I'm neither a lawyer nor a policy experts, but:

This certainly establishes the right to harvest and own space resources.

The killer phrase is "free from harmful interference", basically meaning, the US shall protect US entities from adversaries in space.

While not mandating the need for military presence, it definitely hints at it.

You quoted the section about the US itself not establishing any ownership, but quite the contrary for private enterprises.

in uninteresting enough resource wise to be passed over by anyone else out there

If you have a nuclear fusion technology that can burn tritium then the moon is VERY INTERESTING INDEED.

If you have an automated means of sifting the lunar topsoil for it, it would be the investment of the century to send it there now and let it chug away while the science on Earth catches up. Of course you would also need a means to prevent anyone from taking it from you, which is almost certainly why noone has done this...

On the other hand, there are hard limits in physics and the speed of light is only the start. In general, Exponential curves of progress or growth are not unbounded, and are really just the lower part of a sigmoid curve: https://en.wikipedia.org/wiki/Sigmoid_function

In that vein, Newton and Kelvin both "proved" that heavier-than-air flying machines were physically impossible. That belief held for hundreds of years, and likely put many off even trying.

Einstein said that nuclear fission was impossible, before Fermi promptly proved him dead wrong.

I'm not saying that we're wrong about c, but we don't know what we don't know.

Which is why Stross ended with:

> Anyway, the point I'd like you to take away from this is that while it's really hard to say "sending an interstellar probe is absolutely impossible", the smart money says that it's extremely difficult to do it using any technology currently existing or in development. We'd need a whole raft of breathroughs, including radiation shielding techniques to kick the interstellar medium out of the way of the probe as well as some sort of beam propulsion system and then some way of getting data back home across interstellar distances ...

You wrote: "Einstein said that nuclear fission was impossible".

Do you have a reference for that? The closest account I know is described at http://www.doug-long.com/einstein.htm :

> Among those concerned were physicists Leo Szilard and Eugene Wigner. But Szilard and Wigner had no influence with those in power. So in July 1939 they explained the problem to someone who did: Albert Einstein. According to Szilard, Einstein said the possibility of a chain reaction "never occurred to me", altho Einstein was quick to understand the concept (Clark, pg. 669+; Spencer Weart & Gertrud Weiss Szilard, eds., "Leo Szilard: His Version of the Facts", pg. 83).

but that wasn't about nuclear fission per se but of a chain reaction.

Also, how was Fermi involved? Fission was "was discovered on December 17, 1938 by German Otto Hahn and his assistant Fritz Strassmann, and explained theoretically in January 1939 by Lise Meitner and her nephew Otto Robert Frisch." - https://en.wikipedia.org/wiki/Nuclear_fission .

Fermi supervised the first demonstration of fission [1].

[1] https://en.wikipedia.org/wiki/Chicago_Pile-1

Yes. But as that link point out, it was years after (and a consequence of) the Einstein–Szilard letter. When did Einstein say nuclear fission was impossible, and how was it Fermi who "promptly proved him dead wrong", as madaxe_again wrote?

Edit: jsnathan at https://news.ycombinator.com/item?id=12326618 found a 1934 quote by Einstein expressing an opinion that nuclear power wasn't possible. This is after fission was already demonstrated.

Fission was discovered in 1938. Fermi observed fission but drew the wrong conclusions, he thought he saw creation of transuranic elements.

> Newton and Kelvin both "proved" that heavier-than-air flying machines were physically impossible.

Can we please stop bringing this up? Same with the "faster than sound flight is impossible" quote. Kelvin was well aware that birds were heavier than air and before supersonic flight it was well known how fast a cannon ball can fly.

These people were talking about engineering and economic realities of their time, not physical laws. In contrast, we currently know of no natural phenomena that would hint at the possibility of faster-than-light travel and in fact have good reasons to believe that it is impossible.

> we currently know of no natural phenomena that would hint at the possibility of faster-than-light travel and in fact have good reasons to believe that it is impossible

Is this true? I thought that if my ship is capable, I can go as fast as I like. I just won't appear to be going faster than light to somebody else.

You are being downvoted for your misunderstanding, which is too bad.

In a nutshell, no matter how much energy you pump into your system, you will never go faster than the speed of light, relative to any other viewpoint.

That is, you would never appear to go faster than the speed of light to anyone - including somebody travelling at the same speed as you in the opposite direction.

The universe outside your window won't be passing by faster than the speed of light either. But that's a bit moot, since Lorentz contraction will make the distances in your line of travel shorter. Also time will pass more slowly for you. So subjectively, it's true that you can get anywhere in an arbitrarily small amount of time if you have arbitrarily large amounts of energy, but the rest of the universe will still see you only approaching the speed of light.

No, b6 has it right, you can travel as fast as you want. The universe will get squished along your direction of travel, effectively increasing the speed of light (relative to the distance you're traveling) as your speed increases.

Relative being the key word. With a sufficiently fast ship you could fly across the universe in your lifetime - but you'd get home to find the sun a cinder and earth long gone.

This is not true. Even in your frame of reference, you cannot go faster than the speed of light.

You certainly cannot travel as fast as you want. The speed of light is the speed limit of the universe, to all observers.

You can't travel as fast as you want because it will take ever larger amounts of energy to accelerate each fraction of a percent closer to the speed of light. You're effectively bounded above by the speed of light.

Maybe I need to clarify? A certain amount of energy must be expended to reach a particular velocity. For a relativistically relevant velocity, kinetic energy is given as: mass * c^2 * (1/sqrt (1 - v^2/c^2) - 1); it's clear that v will never reach c.

For an example of how things can escalate: an object massing 1 kiloton traveling at 90% the speed of light has 4x the kinetic energy as the same mass at 65% (for context, a 1kton object at 0.65c has ~50x the energy as was used in 2013). From 90% -> 99% it's a ~5x increase. And from 99% -> 99.9% it's 3.5x. So just a 0.9% increase in speed has almost as much impact on energy as the 25% increase at a lower velocity.

Relativity means that there's no difference between "I'm going at speed V forwards" and "That object is going at speed V backwards" (assuming neither of you is accelerating). In fact, the only way to tell your own speed is to look at the speed of the world around you, and reverse the direction.

Since it's impossible for you to observe anything else going faster than the speed of light, you can never conclude that you are going faster than the speed of light. (Unless you wanted to define everything in the universe as moving faster than the speed of light in the same direction, but that just makes the math stupid for no reason.)

If you start accelerating, you will find that the amount of energy required to go faster (or, equivalently, to push other objects away from you faster) increases to infinity as you approach the speed of light.

I am afraid I am not in the flight for “aerial navigation”. I was greatly interested in your work with kites; but I have not the smallest molecule of faith in aerial navigation other than ballooning or of expectation of good results from any of the trials we hear of. So you will understand that I would not care to be a member of the aëronautical Society.

What precisely is Stross talking about other than the engineering and economic realities of our time? No physical law prohibits interstellar travel.

When did I say faster-than-light travel?

The person you replied to was talking about the physical limits, and you replied "in the same vein".

You said, "proved that heavier-than-air flying machines were physically impossible". That's rather an extreme statement that isn't supported by the passage you quoted or, it seems, what you're saying now.

How about the Alcubierre drive (https://en.wikipedia.org/wiki/Alcubierre_drive)? Yes, there are many unknowns and in filling in those gaps, we might discover warp is impossible after all. But we could also discover the opposite. The reality is that there are potential work arounds that fit our current understanding of physics -- potentially -- and our current understanding of physics is incomplete. In filling in the gaps we might discover more workarounds. Or we might discover that our existing workarounds were duds.

The truth is we won't know until we try. And trying requires the firm belief that we could succeed.

It doesn't do us any good to be pessimistic and announce that we know the physical laws and the physical laws make this impossible. Instead, we should be hopeful and say "Well, here are a dozen things that may or may not work. Let's take a moonshot and see if we can make one of them fly."

Anyone have an estimate of the amount of energy needed for the drive?

never mind the energy requirements - it relies on the existence of exotic matter with negative mass. don't hold your breath. it's a cool idea though.

Not sure, I haven't done all that much physics since undergrad (it was my major). But with regard to the negative matter issue mentioned by another commenter, there is this in the wikipedia article:

> However, at the close of his original paper[2] Alcubierre argued (following an argument developed by physicists analyzing traversable wormholes[3][4]) that the Casimir vacuum between parallel plates could fulfill the negative-energy requirement for the Alcubierre drive.

The Alcubierre drive can be summed up as "If I have one thing that's impossible (negative matter), I can do something else that's impossible (FTL)." (And, no, negative matter is not antimatter.) It's an intellectual exercise, nothing more.

It's all very well and good to say "don't be pessimistic" but there has to be an open mathematically and physically valid path that makes it possible or all you're doing is wishful thinking. And right now, there isn't even a hint of a practical path that we can follow, either theoretically or experimentally, that enables the possibility of FTL.

You don't need warp drive to go to the stars. You need suspended animation, extreme life extension, brain uploading, sentient AI, or some combination thereof.

At 10% the speed of light it is maybe 50 years to the Centauri system including time to accelerate and decelerate. We already know one physically plausible propulsion system that could do it: thermonuclear Orion. Fusion rockets could as well but the physics is not as totally proven out as e.g. H bombs.

50 years is fast. It only seems slow because we are very short lived and very fragile. Biology, not propulsion, is the primary barrier to interstellar flight. Even if it were possible, fixing biology would probably be a ton easier than a warp drive.

But see also: Fermi paradox.

There's also the EmDrive (https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster), which is controversial because it seems to violate all known physical laws. But there are prototypes that seem to work and have been replicated a handful of times by responsible and credible research teams. In each case, there are possible sources of error, but the fact that it appears to be replicated and we can't (yet) rule out the idea that it does work is very exciting. It should be aggressively pursued, because if it does work it's a very big deal.

Instead of looking at things like this with jaded skepticism, we should look at them with excitement and pursue them aggressively! The moment we get overconfident in our own knowledge is the moment we cease to discover new things.

I think the EmDrive is probably fallacious and doesn't actually do anything, and we absolutely need to keep testing it and try to prove that, because if I'm wrong it would be amazing.

Even if we take it as a given that it's nonsense and doesn't actually do anything, we'd still need to test it further just to understand why it does appear to be doing something.

Scientific skepticism, not jaded skepticism: http://theness.com/neurologicablog/index.php/despite-headlin...

>Einstein said that nuclear fission was impossible, before Fermi promptly proved him dead wrong.

Reference please.

And was this before or after the famous Einstein-Szilard letter to Roosevelt, which not only motivated the Manhattan Project but also specifically referenced Fermi's unfinished theoretical research of a possible chain reaction in uranium?

Google found me this [1].

"On 29 December 1934, Albert Einstein was quoted in the Pittsburgh Post-Gazette as saying, “There is not the slightest indication that [nuclear energy] will ever be obtainable. It would mean that the atom would have to be shattered at will.” This followed the discovery that year by Enrico Fermi that if you bombard uranium with neutrons, the uranium atoms split up into lighter elements, releasing energy."

This would be before the 1939 letter.

[1]: https://www.newscientist.com/article/dn13556-10-impossibilit...

Do not confuse "no indication that [nuclear energy] will ever be obtainable" (there is no evidence that it is an achievable engineering feat) with "it is impossible" (it is explicitly not permitted by physics as we understand it)

You're probably right about Einstein not suggesting there was a hard physical limit preventing nuclear energy. But I don't think that hard physical limits are a good argument anyway.

There are FTL proposals that do not violate known physics, such as distorting spacetime using some perhaps yet unknown mechanism.

Saying that there are hard limits in physics here, as you did, suggests that research in this direction is not worth our time.

I believe that is misleading.

That seems way bogus to me. Fermi and the physics world believed that he had found transuranic elements. It was Hahn, Meitner and Strassman who said it was fission in late 1938 (a couple of months after Fermi got the Nobel citing that discovery, but no worries, he had done plenty of Nobel-worthy things).

> That seems way bogus to me.

I'm sorry, I'm not sure exactly which part you're objecting to?

In 1934 everybody thought that Fermi had discovered transuranic elements, that it was fission wasn't clear until Hahn and Strassman's experiment in late 1938.

If Einstein said that, I'd say he was wrong at the time, because already in the 1920s it seemed probable that nuclear fusion powers the stars: https://en.wikipedia.org/wiki/Stellar_nucleosynthesis#Histor...

Of course that's a long way from practical engineering, but it is evidence that nuclear power may be obtainable.

Technology is one thing, and the article has basically assume 2 order of magnitude better than anything that is currently somewhat achievable. But really, Earth has still millions of years of habitability, so really the limitation is not spending 200 years to send a probe and a few thousands in a space ship.

The key limitation here is obviously political stability, and in that area progress are counted in hundreds of years. We need something that fit within a tiny fraction of a single human life, because any plan longer than that is highly improbable, not because of physic, because of human.

Bingo.

> We need something that fit within a tiny fraction of a single human life

This can be worked on from two directions. I'd be shocked if we didn't manage to make any progress into slowing down old age. With a 120 year old lifespan and the perspective finding things even better when you come back, people may be willing to invest 50 year into this.

> Earth has still millions of years of habitability

The lower bound is probably 600m to 1bn years. By then the sun's luminosity will have increased enough to eventually boil off the oceans. To get over this hump we'd need to sequester or condense atmospheric water vapor. That'd push our planetary survival time out to about 3bn years.

We would think that by such time people would have figured out artificial solar shading to keep the planet at a nice stable temperature for a long time. This could even be decades-away technology.

Wow, there are some pretty hilarious howlers in that article. My favorite is "Even if there were a trustworthy way to send money over the Internet—which there isn't—the network is missing a most essential ingredient of capitalism: salespeople." Be careful what you wish for, eh?

He also misses the insight that while the internet as a whole is uncurated (and that's a good thing), nothing stops people from creating curated resources within that framework. For comparison, it took me ~3 seconds to find the date of the Battle of Trafalgar (highlight the text "date of the Battle of Trafalgar" in the article, right-click, 'search on Google', boom direct answer straight from Google itself).

Although if you'd responded to his at-the-time perfectly reasonable objections to internet publishing by informing him that, just over a decade later, we'd invent special beach-portable computers with sunlight-readable screens for the sole purpose of reading electronic books, and people would actually buy them, you'd probably come across as overoptimistic.

"Yet Nicholas Negroponte, director of the MIT Media Lab, predicts that we'll soon buy books and newspapers straight over the Intenet. Uh, sure."

I really like that there's an ad just under that sentence to subscribe to Newsweek, which is now online-only.

> note that 4.25 light years isn't an order-of-magnitude improvement over the previous winners for Earthlike proximity, such as Wolf 1061c (13.8 light years away) or Kapteyn B* (12.76 light years away). We're talking about the difference between 40 arbitrarily-huge-units and 100 arbitrarily-huge-units. So how should we contextualize these arbitrarily-huge-units?

This is nonsense. The point is that the exoplanet was (potentially) found orbiting the nearest star, which means it's as close as it can be.

The physics of space travel are harsh, and the distances involved even harsher. Plus, unless you want to go screaming by on a fly-by mission, you have to burn all that delta-V you generated to get there in order to slow down again.

The only real solution will be some kind of essentially magical faster than light technology - never say never, but it doesn't seem likely without some staggering breakthroughs in areas of physics we don't even have an inkling about.

Maybe it's the American exceptionalism and internalization of Manifest Destiny as the natural order of things, but the idea of being effectively stuck, as a species, on this one rock for eternity is pretty depressing. Especially if that is the fate, not just of ourselves, but of all life intelligent enough to look up at the stars and imagine walking among them. If the best we can hope for is a Motey-like[1] Malthusian cycle, it's not much to look forward to.

[1]http://amzn.to/2b5I0Ea

Basically wormholes/hyperspace/teleportation, or bust.

But I'd think living in orbital or interplanetary space right here in our solar system can be a happy medium, and sustain us for a loooong time to come.

Or just build a big ship and send it with settlers. If it takes 1000 years that's fine

Isn't "a ship where we can live for 1000 years" just the same as a planet?

Yeah, maybe the next big thing isn't travelling to a far away planet but just creating a ship big enough. I had a pretty cool theory about that when I was a kid, funny to see that it may be what actually happens.

Or just move the entire solar system closer.

I mean - crap - if you're doing going to do interstellar engineering, you might as well do it properly.

Supposing that next year we get viable coldfusion and that em drive thing turns out to be actually real somehow it would seem feasible to move the planets, but how would you move the sun? You can't very well put an engine on the sun. Maybe a Dyson sphere, but that requires a lot of material, probably more than is available in our solar system, so we'd need to start significant extrasolar mining operations before we could move it.

It only has to be thick enough to reflect light.

Oh wow thanks, good to know there's a name for this idea with some amount of thought put into it. Might have to binge on cosmic megastructures reading.

How many settlers? 1,000? 10,000? 100,000?

Would you launch adults (average weight about 70 kg) or children?

A founder population of 1,000 wouldn't be unprecendented.

https://en.wikipedia.org/wiki/Population_bottleneck#Humans

The real problem is that an individual can only learn so much and 1,000 can't support the skills needed to run something like a modern civilization.

The first and possibly only settlers will be AIs.

The scientific breakthroughs needed to make an interstellar spaceship are so far away that we must assume they'll be post-singularity tech.

A friend of mine was doing a Masters in Zoology a few years ago, and I briefly discussed the idea of generation ships with her. She explained to me that a foetus can't properly develop in microgravity, and they abort in the early stages. (I can't really remember because it's going back 12-13 years now.)

Accelerating such a ship at close to 1G for half the journey, then flipping it over and decelerating at the same for the other half of the journey would approximate Earth gravity for the occupants. Since acceleration acts by pushing against you, rather than acting against your entire body as gravity does, I'm unsure as to whether it would be an adequate substitute for gravity.

Perhaps someone here knows.

The other option (from the science fiction, anyway) would be to revolve part of the spacecraft enough to generate sufficient centripetal force to approximate gravity. It's become almost a trope since 2001, but I'd imagine there are some significant engineering challenges to actually implement such a thing. How do you keep the drum rotating, without spinning the rest of the craft? How do you engineer bearings that can handle the force, while at the same time dealing with vacuum and extremes of temperature? There's a lot of moving parts, and moving parts wear, seize, and can fail catastrophically...

If the bearings prove difficult, just rotate the whole thing.

You can just spin the rest of the craft as well. No moving parts required.

That increases mass and engineering considerations.

Designing a satellite or space probe is (structurally) pretty simple: you need a central truss or platform which is going to be subjected to very little stress or torque.

Pressurised compartments up the complexity a lot. Leaks are bad. Big, fast leaks are really bad. Even with out gravity, thermal gradients (sunlit side, dark side) present significant stress.

Pressurised compartments under constant 1g strain are even more complex. You've got stresses and strains, mass, things get dropped and bumped inside, etc.

Mass costs money. About $1k to $40k per kg in LEO, though the lower end of that's becoming more viable. Elon Musk and others would like to get down to $200 kg, though I find that unlikely.

Acceleration and gravity are entirely interchangeable. The feeling you get due to gravity is also because of something "pushing against you" - namely, the ground. If you didn't have the ground to push against, nor air to drag against you, you'd be in free fall, which is the same as being in zero gravity.

> Since acceleration acts by pushing against you, rather than acting against your entire body as gravity does, I'm unsure as to whether it would be an adequate substitute for gravity.

I'm far from an expert, but I thought it was a basic tenet of relativity that, without external information, there is no way of telling whether your spaceship is accelerating at 1G or standing on the Earth's surface.

I'm pretty sure steady 1G acceleration brings the subjective travel time within a lifetime for a lot of journeys. I haven't done the math myself, though, just heard it from others. Of course, the technology to apply such acceleration to any reasonable-sized ship is rather fanciful at this stage.

> She explained to me that a foetus can't properly develop in microgravity

How on (off?) earth can anyone know that?

Presumably animal models. Fish, frogs, mice, etc.

https://scholar.google.com/scholar?q=fetus%20development%20i...

That ship would have to be megatonnes of shielding and habitat. Consider that the article describes the entire energy output of North America being used to launch a dinky little probe like New Horizons. We're talking about a dozen orders of magnitude in energy technology needs. This is beyond "cold fusion" and into "cheap matter-energy conversion" like a cheap way to synthesize antimatter or something.

Or go part of the way and stop.

Interstellar space is riddled with bodies. Sol's Oort cloud extends out to a light-year or so, but the fringes of it mix with Alpha Centauri's. It's mainly composed of cometary nuclei and ejected rocky masses, so it's rich in low-mass elements: hydrogen, carbon, oxygen, nitrogen... all the elements of life. The total mass is on the order of tens of times the mass of the Earth, except unlike Earth, all that mass is accessible.

Finding estimates of the separation between objects is pretty hard, but the ones I've seen very from ~5 light seconds up depending on where you are and how big a body you're interested in. About half a light year out, it seems that there's likely to be a decent sized body (10s of kilometres across) within 30 light seconds. Larger objects are less common, but here's an estimate of there being about 10^5 moon-sized objects per star: http://arxiv.org/abs/1201.2687

It's surprisingly hospitable out there, too. The environment never changes, you don't really need to worry about radiation (except for the occasional supernova), and cooling is easy. Travel is easy, too: space is nearly flat, so you don't need to worry about transfer orbits: boost in a straight line, then decelerate and stop. Travel time is solely a function of how much energy you want to put in. Most objects are moving pretty slowly, too, way under a kilometre per second.

You need to be able to fuse hydrogen, of course. Or engineer yourself to use less energy.

It would be entirely feasible to build a ship, travel six months to a year, and then settle on a decent sized body and found a colony there. A few generations later, your children head off again. Eventually your child civilisation has hopped rocks all the way to Alpha Centauri, but of course by then the idea of living near a star would be utterly alien to them.

Personally, I think that when we discover proper alien intelligences, it'll be here: probably in the form of computational nets of bacteria-like organisms, living very slowly and efficiently, spreading via spores from rock to rock in the darkness. So much safer and more reliable than the fast, hot, dangerous worlds down on the edges of the solar fire...

My uncle was awarded a PhD in the late 1970's from Arizona for the technical papers on generations ship written for NASA, so I have some insight to this stuff [0].

The TLDR; for the project was that assholes suck. Many many things are hard to work out for a generation ship, from the correct number of light bulbs to bring with you, to the plumbing, to the risks of permanent 0g. In all, the engineering was remotely possible for the tech at the time, but extreme. A generation ship, ala a giant metal can with people and pipes in it, was engineeringly feasible, but the human considerations made it impossible.

The main issue was that the ship's inhabitants were to be born, essentially, in Alcatraz; a prison they could never escape. As time went on, the crew was expected to become less and less aware of the danger of the vacuum and an accident was exponentially likely to occur. Most highly isolated peoples, like on Rapa Nui or Naval ships, were brutally strict. As teenagers are wont to be boundaries testers, it was expected they would be the most risk to the ship. Add in deteriorating conditions and failure of parts, and you end up with the Stanford Prison Experiment[2] for generations. The project was a human rights nightmare. For thousands of years, potentially, you breed and die in what may eventually amount to a Nazi death camp.

The simplest solution was to make a giant Stanford torus [1] with the land area of between California or Maryland, stick an artificial sun in the center for light and heat, and launch it at your target [3]. Remove any computers or guidance of the Tube, just let gravity somehow guide you into the right place. Oh and make it big enough that some wacko death cult that may arise can't break it apart or kill everyone. Essentially, you launch a mini-Earth Tube, and let them fend for themselves. When the Tube gets into position, you hope they get curious enough to figure out a way to jump out.

Obviously, the mass of the thing alone is too much to begin to think about, let alone the time it would take to create, launch, fly out, orbitally park and decelerate, and finally disembark. Even back in the 1970's, they knew that the rate of tech increase would just make it so that you launch a robot with some zygotes and grow the people when you get there.

In the end, the possibility of a generation ship was deemed too remote to devote more funds towards. Our better natures think that we could live in harmony in the stars, but history tells us that our darker selves always arise. The issue with a generation ship of humans is not the ship, but the crew, as a lot of the time people can be nothing more than assholes.

[0] By awarded, I mean he published the papers, and someone at UA forced him to take a single class for the requirements, so impressed they were at the scholarship.

[1]https://en.wikipedia.org/wiki/Stanford_torus

[2]http://www.prisonexp.org/

[3]https://en.wikipedia.org/wiki/The_Book_of_the_Long_Sun

That's a very cynical view of humanity. For most of human history, people lived in small tribes of no more than 200 people and got along fine. The risk of sabotage is hugely over rated. Large cities survive on Earth every day because most people arent motivated enough to dump poison in the water supply or destroy critical infrastructure. The vast majority of people are not genocidal, and the few that are are terrible at it.

The zygote idea may be possible in the future. We don't have artificial wombs yet, not to mention baby raising robots. Perhaps cryopreservation could work. I believe a rabbit kidney has been successfully frozen and revived intact. But brains are more delicate.

For most of human history, people lived in small tribes and waged incessant tribal warfare over women, land, and resources. Trying to cast prehistoric humanity as some golden age of peace and harmony is disingenuous. And we know for a fact that in the historical era, mankind has been at war virtually every year since the Sumerians started pressing glyphs into clay or the Chinese scratched runes on ox bones.

I don't think there is a lot of evidence to support that. Ive read that war was mostly a product of agriculture, which led to famines and stores of food easy to steal.

But regardless, when hunter gatherers did go to war, they fought other tribes. Internal conflict is much less common. In a group where everyone knows each other and depends on each other for survival, war makes no sense. Groups of humans that didnt cooperate within a tribe would have died out long ago.

Such an environment will hopefully have plenty of resources. At least of food and water and other necessities. Which also reduces the motivation for war and conflict.

There's very little evidence of war (defined loosely as an organized conflict between two polities) before the development of agriculture and civilization. It's worth noting that, in ancient Sumer, whereas most advancements start from the south and go north, defensive walls originate at the north and go south. The best evidence for Paleolithic warfare--which is to say pretty much the only--is a single apparent cemetery (at the tail end of the Paleolithic) where about half the people died with signs of violent trauma.

Or a time stasis device, as described by Niven, Vinge, and others.

It is possible to leave this rock, but we'll need to think in terms of millennia, not lifetimes. Long term thinking that's also kind of unAmerican.

https://en.wikipedia.org/wiki/Generation_ship

While we wait for research to get there we can play with the other rocks in the vicinity. All those climate engineering ideas could be tried on Venus, for example.

If we could change that atmosphere (engineered bacteria and collision with an ice asteroid to lose some gas and gain some water?) and cool it down a little.. It's not that far out of reach.

> we'll need to think in terms of millennia, not lifetimes

I don't think it's safe to assume the maximum human lifetime is a constant in these discussions.

> The only real solution will be some kind of essentially magical faster than light technology

Doesn't have to be faster than light, if you don't care about everyone you ever knew being dead for decades (or centuries, or millennia) by the time you reach your destination: thanks to time dilation/length contraction, you can travel arbitrarily far distances in your lifetime by going at a large enough fraction of c.

Assuming you've got the technology, of course.

I don't think that's true, I think you're still limited to the range of < c * lifetime, about 390 trillion miles. If you think this is wrong, can you post some links?

Edit: nevermind? The equation here does indicate that length contracts to approach zero as velocity approaches c

https://en.wikipedia.org/wiki/Length_contraction

This page has a nice table for time dilation:

https://www.fourmilab.ch/cship/timedial.html

If you can instantaneously accelerate up to 0.99 c, you end up with a range of ~500-1000 light years before you die (dilation at that speed is 7:1, you have ~80 years of ship time).

So the distance you can travel does depend a great deal on how fast you can actually go.

Isn't it more useful to think in terms of how fast you can accelerate? Doesn't help if you arrive as jelly.

Yeah, that will give a lower, better estimate.

My point was just to clarify that the arbitrary range from time dilation doesn't really start to kick in until you approach c. The simpler, coarser calculation still shows that quite well.

A constant 1g acceleration gives a good general basis for extrapolation. It's survivable (on an acceleration basis). If perhaps difficult to attain.

And if you could attain (and sustain) it, it would bring you close to c within a year (shipboard time).

I should have clarified: the case is sufficiently obvious that there are a bunch of illustrations of how long (subjectively) it would take to travel various distances at 1g constant acceleration.

Ah, there's a Wikipedia article: https://en.m.wikipedia.org/wiki/Space_travel_using_constant_...

And a chart of subjective and observer times to various landmarks: https://upload.wikimedia.org/wikipedia/commons/f/f5/Roundtri...

It takes a while to get going. For round-trip subjective travel times, Prox. Centauri is about 7 years. Galactic center about 42. Andromeda Galaxy, 50 years. Edge of the observable universe, 100 years.

Mind, the folks you left behind would be up nights waiting slightly longer. About 15 years to Prox. Centauri, rather longer to some of the remoter destinations.

But is it meaningful to talk of spending a year or more of subjective time accelerating at 1G?

According to the Wikipedia page you link to, it does not become harder to accelerate a spaceship the closer it gets to c, at least from the point of view of its occupants.

So you've been accelerating for ~300 days (shipboard time), and you're now nearly at c. In fact, you're only 10m/s below it, so you should reach light speed in a bit more than a second.

But we know that's never going to happen, because it can't.

I'm assuming (I don't know, I'm a layman) that that final second-and-a-bit will stretch like taffy, in time-dilation terms. You're already travelling at 0.999999966c, at which for every second of shipboard time more than an hour will pass on Earth. Dilation will only increase the closer you edge to c: at some point, every yoctosecond of shipboard time will equate to many times the predicted lifespan of the universe outside.

It's hard to imagine something terminal wouldn't happen to the ship in that final second, assuming there's anywhere left for it to happen in.

> Plus, unless you want to go screaming by on a fly-by mission

In space, no one can hear you go screaming by.

In any case, terraforming some of the rocks we can reach (Mars, Venus, et. al), while an enormous undertaking, might be a more solvable problem than FTL travel (because the latter is most likely impossible, while the former is merely insanely difficult and impractical). The problem is terraforming projects would likely be multi-century efforts requiring some level of international cooperation, so... yea, we're stuck here.

Note in the comments Peter Erwin points out that Charlie has overestimated the density in the (relevant portion of the) interstellar medium by several orders of magnitude: http://www.antipope.org/charlie/blog-static/2016/08/san-trom...

> Currently, the most distant visited body in the solar system is Pluto, at 7.5 billion kilometers. The New Horizons probe flew past Pluto on July 14, 2015. It was launched on January 19th 2006 by a booster and upper stage combination that blasted it straight up to solar escape velocity, with a speed of 16.26 km/sec (58,536 km/h), making it the fastest human-made vehicle ever: it then executed a Jupiter gravity-assist flyby to slingshot it out past Pluto, where it arrived nine and a half years after departure.

Lots of people have no clue just how big the solar system is, and how small the planets are in comparison. (Never mind the distance to exoplanets). Here's one video that gives a nice demonstration using a soccer ball and pin heads, from Mark Rober (who worked on a Mars rover at Nasa): https://www.youtube.com/watch?v=pR5VJo5ifdE

Bill Nye demonstrated it pretty well on his tv show. Very easy for kids (including me when I first saw this) to comprehend. https://m.youtube.com/watch?v=97Ob0xR0Ut8

It's disingenuous to talk about Fukushima as a "meltdown", or imply that it was dangerous (on the scale of space-travel dangers).

The Project Orion design was for 10% of light speed, and didn't assume any scientific breakthroughs like fusion - it would require a massive amount of engineering , but the core technology (that used in nuclear weapons) was mature in the '70s.

We're still talking about a 40+ year journey, for a craft whose cost was estimated at $367B at the time - about $2.5T now. It's not easy by any means. But it is doable. We'll get there.

> a craft whose cost was estimated at $367B at the time - about $2.5T now.

So we can pay for it with just the money mismanaged by the US armed forces.

No you can't, Jesus, read the actual article. The entire yearly budget for the US armed forces is around $600 billion.

They had $2.5 trillion in adjustment lines that mostly netted out, they didn't actually lose track of $2.5 trillion, because they didn't have $2.5 trillion to lose track of.

> The entire yearly budget for the US armed forces is around $600 billion.

Oh, only.

My point still stands: 2.5T isn't that much for a project at a national, or even global, scale. A mere ten times ISS and ITER and LHC combined? Absolutely doable.

No part of your original point appears to have survived that rebuttal.

That's a yearly budget though. This craft could be built over many years, so the comparison makes a bit more sense.

It would be built over several years anyway, you can't get a project of that scale done and ready in a year.

Or just repurpose the incredibly expensive relict stockpile of nukes, which is where most of the cost sits.

The tricky bit is reliably getting hundreds of tonnes of thermonuclear goodness into orbit without a single accident, which is why Orion died a death.

Well, you just launch them on one Orion-drive space ship. A few dozen nukes to get it into orbit probably will only cause a few dozen cancer cases, if you do it right.

We'd get there even faster with the money mismanaged by the US welfare system. Armed forces is only 23% of the US federal budget. Welfare's a whopping 40%.

Of course, without American armed forces and the Pax Americana, the unprecedented world peace (relatively speaking) we have right now likely would not endure. And without welfare spending, morale would decline when old people and children that didn't need to die do. Both outcomes would likely lead to economic decline. Then we might not get there so fast after all.

Sometimes the expedient-seeming solution isn't always the best one.

remember the US military expenditure is almost the total sum of the next 14 countries, 12 of which are allies.

I'm sure the "pax americana" would hold with some cuts.

Arguably those twelve allies have such low budgets because the US budget is so high.

> Of course, without American armed forces and the Pax Americana

I didn't know that mismanagement and embezzlement of funds was a vital core aspect of the Pax Americana.

Similarly, the US health care system is about twice as expensive as comparable foreign systems for the same level of service provided. You can reform it and make it more efficient without compromising its mission.

How is it disingenuous?

Or is it more accurate to call Fukushima a dirty bomb that spread nuclear material all over Japan because of idiotic politicians?

That would be less accurate, because it wasn't (except in the minds of the idiotic politicians who fed the hysteria over radiation).

Only if stating the true facts as reported by the Nuclear Energy Agency is "disingenuous".

On 17 May, analyses performed by TEPCO indicate that significant fuel melting occurred in the unit 1 reactor core with relocation of molten fuel to the lower portion of the reactor vessel. Further, the high-temperature molten fuel (greater than 2 800°C) appears to have caused small leaks in the lower head of the reactor pressure vessel....

On 7 June 2011, the Government of Japan releases a report prepared by the Government Nuclear Emergency Response Headquarters for the IAEA Ministerial Conference on Nuclear Safety (20-24 June 2011, Vienna, Austria). This report includes analyses of the damage to the cores at units 1 to 3. The analyses show that unit 1 has suffered extensive fuel melting and that the reactor pressure vessel has been breached.

http://www.oecd-nea.org/news/2011/NEWS-04.html

Multiple additional reports, totalling about 50: http://www.nrc.gov/site-help/search.html?q=fukushima+meltdow...

Or:

1. Introduction The triple core meltdown at Fukushima Dai-ichi power plant on March 11, 2011 is the worst nuclear catastrophe after Chernobyl in 1986. The substantial losses of this accident have aroused in the public opinion an old age debate: Is nuclear power safe?

Safety Science April 2014, Vol.64:90–98, doi:10.1016/j.ssci.2013.11.017 How Fukushima Dai-ichi core meltdown changed the probability of nuclear accidents? Lina Escobar RangelFrançois Lévêque

http://www.sciencedirect.com/science/article/pii/S0925753513...

Or:

Journal of Nuclear Science and Technology Volume 49, 2012 - Issue 1

"Analyses of core melt and re-melt in the Fukushima Daiichi nuclear reactors Fukushima NPP Accident Related"

Fumiya Tanabe Page 18-36 | Received 11 Aug 2011, Accepted 16 Sep 2011, Published online: 24 Jan 2012

http://dx.doi.org/10.1080/18811248.2011.636537

Abstract:

Analyses are performed of the first core melt behavior of the Unit 1, Unit 2 and Unit 3 reactors of Fukushima Daiichi Nuclear Power Station on 11–15 March 2011 as well as the re-melt (melt again) behavior in another chaotic period of 19–31 March 2011. Analyses are based on a measured data investigation and a simple model calculation.I

Keywords: core melt, re-melt, severe core damage, Fukushima, nuclear reactors, energy balance, zirconium steam reaction, hydrogen generation, core materials inventory, core water level

A Google Scholar search turns up over 9,000 similar results:

https://scholar.google.com/scholar?start=10&q=fukushima+core...

Please do not spread disinformation.

I wasn't aware this reality check was needed, but it's worth noting that we haven't even left Earth yet (going to the Moon doesn't really count, and we've since lost that capability again). If we were a solar-system-wide civilization, I can see how it would make sense to talk about the feasibilities of interstellar travel, but today we are so far off it's not even an issue. We also don't have any ambitions to change that, so extrapolating from today's state of affairs, we'll probably remain thoroughly Earth-bound until we reach a tech level that enables individual people to have space programs (if we ever get there).

It's fun to think of probe-based exploration, but apart from acceleration/energy based problems we haven't even figured out how to make machines last that long. This is all very, very far off.

> going to the Moon doesn't really count, and we've since lost that capability again

What we've lost is will. The capability is definitely better today, even though still not affordable enough to fit today's budgets.

Well I think he means we couldn't just go to the moon next year, even if we wanted to. All the engineers and factories and equipment behind Apollo is scattered or lost. It would basically require starting a whole new moon program from scratch and designing and building entirely new spacecraft, etc.

Indeed, yes, that's what I meant. But Jakub isn't wrong either, we lost the will too. But I thought I addressed that, but apparently not clearly enough.

> This veritable speed racer of an interplanetary probe would thus require a mere 31,600 years to reach Proxima Centauri (if indeed it was pointed in the right direction, which it isn't).

Holy cow, that's multiple times longer than humanity has even existed as a civilization, and in all likelihood it might perish before that probe could even make it there. What a reality check. I don't think incremental improvements are going to cut it for space travel.

So we should send one out now, and hope we're still around when it gets there.

And each time we complete development of something better send one of those.

Can you imagine how pissed we'd be 31,000 years from now, not having sent whatever we finally determined to be the best we could do, when we could have done it? It may take N thousand years to get something there, but only four years to get data back. It's worth it.

Designing a machine that still works in 31,600 years seems a pretty tough challenge. Even remembering to listen for a signal in 31,600 years is probably already a hard problem.

> Designing a machine that still works in 31,600 years seems a pretty tough challenge.

Good point. I'm quite sure we can already point something somewhere and it'll get there, or close, in 31K years. So the real challenge is what you point out. And remembering is maybe even more challenging.

So the first one out ought to be very simple. Maybe it just pings home every N days. That would mean that we'd start out listening for it, and perhaps that infrastructure would be taken care of.

And maybe that first one would die before it arrives. But if we continue to send something better each time we're able, I think we'd eventually have success. And if we do continue to send things, maybe we'd have an institutional tradition of listening for the original.

Just a ping from four light years away does not seem worth the effort to me, it seems just slightly above throwing a rock in the direction of Proxima Centauri. At least take a picture.

By the way, there is also a thing called wait calculation [1] which deals with this very problem, when should you start an interstellar journey. There is not much of a point to start today if you can cut the travel time in half in, say, a hundred years since you would pretty quickly overtake the mission started today and arrive first despite the fact that you started a hundred years later.

[1] https://en.wikipedia.org/wiki/Wait_Calculation

> Just a ping from four light years away does not seem worth the effort to me,

That's all Sputnik was, a ping in orbit. But it was worth doing to get something, anything at all, in orbit. Sputnik itself wasn't important, but the knowledge and experience gained was.

You don't not throw a Sputnik up because you know that decades later you'll have the ability to throw up a space station. Sputnik is part of the space station process.

The title of this article sounds like a password [1].

Whenever one of these articles comes out I like to think of this fun paper: [2] Are Black Hole Starships Possible?", http://arxiv.org/pdf/0908.1803

[1] https://xkcd.com/936/ [2] https://en.wikipedia.org/wiki/Black_hole_starship

> 4.25 light years isn't an order-of-magnitude improvement over the previous winners for Earthlike proximity, such as Wolf 1061c (13.8 light years away) or Kapteyn B* (12.76 light years away).

Wrong. It is, quite literally, just about a order of magnitude better.

Maybe in base-3...

He was probably referring to base e (2.718281828).

I know Charlie is a writer, not a radiation physicist, nevertheless... major 'units' fail in his radiation calculation. 6 Trillion alpha particles per sq meter per second is 6 TBq per m^2; not 6 Tbq per m^2 per second. TBq as a unit already includes the "per second". In other words, you wouldn't get a Fukushima release every eight days - you'd just get about 1 millionth of a Fukushima... and that's it (per m^2, of course), as long as you are moving through an interstellar medium as thick as he posits at that speed.

160 Curies is a dangerous amount of radioactivity, but nothing outrageous. I often work with gamma sources much larger than that. I use a 1000 Curie source that easily fits in a sq meter, and it's used the same shielding for over 20 years.

Sounds like a riveting to-do list, with lots of big implications for the folks back home.

> We'd need a whole raft of breathroughs, including radiation shielding techniques to kick the interstellar medium out of the way of the probe

Game changer for nuclear power and propulsion, in terms of safety. If we did this with matter, that means we can get closer to hot things [1]. If we did this with energy, ha! - we can now start harvesting edge-of-magnetosphere antimatter and explore mining and terraforming using directed energy.

> as well as some sort of beam propulsion system

If we can beam massive amounts of power out that means we (a) have massive amounts of power up there and (b) can beam (a) home [2].

> and then some way of getting data back home across interstellar distances

Either we figured out how to keep lasers (or some other stream of stuff) columnar over super-long distances or we broke new ground in information theory. Either way, getting a grainy picture home from Proxima Centauri on an apple of an energy budget means getting lots more closer to home around faster and more efficiently.

[1] https://en.wikipedia.org/wiki/Star_lifting

[2] https://en.wikipedia.org/wiki/Dyson_sphere

Focusing on habitability from our perspective seems somewhat parochial.

From the perspective of colonization: by the time future sentients descended from or created by present humanity get to other planetary systems, we-for-some-definition-of-we would be capable of living anywhere, and space and novelty will be things that you get by computing more efficiently, not by going places.

From the perspective of adding data to the Fermi Paradox: assessing the possibilities of life being out there by looking for places in which bacteria of the known varieties could survive probably tells us little about the true range of life.

From the perspective of resource assessment: by the time descendant entities get to other systems, it won't much matter how the matter there is distributed. It will used efficiently whether a gas disk, rock and ice condensations, or (improbably) somehow all in the star.

When I read articles like this, I like to imagine that we are already on a multi-generational ship (earth) and are on our way to see the wonders of the Andromeda Galaxy :)

NASA should over the next 100 years build a hyper-telescope, so that people can begin to actually see these planets in detail before before a probe can be sent.

Even with current technology, a hyper-telescope could be self-assembled in space, built from billions of 3-d printed & smoothened mirror segments, all aligned to half wavelength of visible light. We need to have a 1000px x 1000px resolution of earth-like planets out to 100 light years away, which would be several thousand miles in diameter.

That's all but impossible. To optically resolve an Alpha Centauri planet of Earth size at Hubble resolutions of Pluto (about 680 pixels square) you'd need a 28 km wide scope (or array).

https://www.quora.com/How-big-would-a-telescope-have-to-be-t...

Rather than seeing shapes of objects, detecting their signatures -- light occlusion, spectroscopy, thermal and radio signatures -- is far more useful. Several of those would reveal chemistry and radiation indicative of life and/or intelligence.

Much xenoplanetary analysis isn't done through optical telescopes, per se, but through spectrographic analysis, which tells us what compounds and elements are present (or are blocking / reradiating) starlight.

Nothing wrong with a 28 km array though, if we can put it in space.

Besides, what about dynamic aperture? I know very little about it, I only heard that a moving camera effectively expands it aperture by the distance traveled within the duration of the exposure.

You're going to want _both_ light gathering _and_ range.

Keep in mind, a planet is probably going to be moving a lot over the course of a few hours. A 24 hour time-lapse of the Earth will give you a lot of pretty colours. But not much by way of a useful image.

You're trying to see something tiny and dim a very long way away, next to something which whilst also tiny (relative to the Universe) is far, far, far brighter.

A long-duration moving-apature exposure of a remote planet next to a dim star seems to me not to be an ideal candidate for high-quality imaging. I'm not sure a large-baseline, large-collector array would do much better, but at least it could narrow the time interval somewhat.

(Though I think you're still basically going to end up with a glared-out, underexposed, blurred pixel.)

The title of this blog post is one of the funniest I've read on HN, really made me laugh.

The author states:

"We might get a small probe up to arbitrarily high velocities if we cheat by using an engine that stays back home where we can keep it running, but then we run into other problems."

Does anyone know which rocket propulsion technology he is referring to there? In the paragraph before he is referring to plasma beam but he doesn't say what this is.

Here's the Wikipedia page:

https://en.wikipedia.org/wiki/Magnetic_sail

Some sort of light sail powered by a giant laser which we keep here.

Probably something similar to Breakthrough Starshot

http://breakthroughinitiatives.org/Initiative/3

The goto site for discussions about interplanetary and interstellar anything is Centauri Dreams:

http://www.centauri-dreams.org/

MagBeam

https://en.m.wikipedia.org/wiki/MagBeam

Excellent read, so much insight. We really need those gates from "The Expanse" series.

Interesting that he doesn't mention the Breakthrough Starshot concept at all.

Very interesting!

https://en.m.wikipedia.org/wiki/Breakthrough_Starshot

It's mentioned in the comments:

> As for the Starshot thing, that sounds like a reboot of Robert Forward's Starwhisp idea from the 1990s. The real problem with that is, how to get any data back from it. (Not to mention how to construct a continuously operating gigawatt laser array in space).

Just finished reading "The three body problem". A civilization on planet in a system with 3 suns would have some interesting challenges.

So what you're saying is, "we need a bigger rocket!"

I agree. It's high time we started on near light speed space travel.

We need cheap matter-energy conversion. Nothing less will provide enough energy for interstellar travel, and cheap matter-energy conversion may not be possible ever. Whether the engine is here or there, the amount of energy needed to launch a properly-radiation-shielded craft is simply obscene.

I don't understand the focus of the article being on sending a physical probe. Why not just send a radio message? Something like "Is there anybody out there?"

I've heard the argument that we shouldn't advertise our existence in case there are hostile beings. But can't we assume that all intelligent life is constrained by the same rules of physics? And why assume hostile?

The round trip time for such a message would be 9.0 year, so getting our signal discovered, and getting it mutually intelligible, could easily never happen, even if there was life there.

Clearly, part of the trick would be to figure out what to send, and to keep sending it.

Well, that, and figuring out how to send it.

Though when you've got the resources of a habitable planet at your back, generating strong signals seems more viable.

Thermodynamics is a real downer...

Imho the entropy laws are the real heartbreaker. They're the ones that explain how the universe doomed.

But they're also the reason we're here in the first place.

Shiva the destroyer, Brahma the creator, Vishnu the preserver.

Bah! That's an engineering problem.

Same story for colonising Mars, or even sending astronauts there. It's pretty much unfeasible. Yes maybe we could send some people there but the costs involved are so astronomical that it really can't be justified. We're stuck on this planet and we need to make the best of it.

And yet, two organizations have plans to do so in the next two decades.

Yeah a handful of astronauts can go there. But everybody else is stuck here.

There's a huge gulf between having plans to do something, and actually doing it. Moreso when that something has never been done before.

Reply on news.ycombinator.com