http://news.ycombinator.com/item?id=140283
http://news.ycombinator.com/item?id=595419
http://news.ycombinator.com/item?id=1078831
http://news.ycombinator.com/item?id=1485286
http://news.ycombinator.com/item?id=1290590
http://news.ycombinator.com/item?id=2467703
Some have more comments than others.
Like a dream all of the net is meshing together.
At any rate, given how many readers are probably new to the The Last Question, it's probably worth citing another Asimov piece that is oft-mistaken for The Last Question - The Last Answer. It's a more recent work, and a bit more obscure, but worth the read if you're into Asimov.
Exponential decay is important because it is, as they say in statistics, "memoryless": it has a simple geometric property that adding a new point today has the exact same effect as adding a new point on the first day. It can therefore be implemented as follows: when you add points to a link, you add them not just to the total points, but also to some accumulator which I will call Hotness. This number is a double; we increment by 1 when someone adds a point.
Every half-hour, some independent process working over still-Hot threads multiplies their Hotness by 0.97153. This gives a half-life of about 12 hours: your rating has hotness 0.5 after half a day, 0.25 after a whole day, and so on. We could tune that if we wanted finer granularity. When something gets below 0.001 Hot we can probably just reset it to 0 Hot abruptly so that we don't check it anymore. (Because doubles will try to go to -infinity if you use them multiplicatively in this way, and if you get to, say, 1000 points this will still mean that we can stop paying attention to you in, say, 10 days.)
Suddenly, adding points to a dead article is the exact same as sponsoring a new article. So we store articles under their URLs as keys, and if you resubmit an existing news story you merely bump it up to 1 Hot.
The "new" page would be very peculiar in this system, though. It might work by listing only those 1 Hot posts which were 0 Hot previously, I don't know.
As for a major con to this approach, I think HN uses polynomial decay rather than exponential decay because exponential decay somehow didn't feel like it had the right "shape" to it or so. This is probably because they didn't implement it in the "memoryless" configuration, though, where each point has value 1 from the moment it's added, and decays slowly.
And so far we're doing a piss-poor job of it.
Taking care of what we have right now is the bigger priority because failing that we never will get off the planet anyway.
Getting off the planet requires a larger degree of international cooperation and funding than stewarding our own planet does. If we can't manage the one we certainly won't be able to manage the other. Also, it is something that we actually can do, if we set our minds to it. Whether or not we can actually get off the planet with meaningful numbers of people to a place that is no longer tied to the earth in some critical way remains to be seen.
And even that might not last long. Space is - sadly - currently not a priority.
1) I've heard many (non-physicist) people argue/think that the 2nd Law of Thermodynamics is a law in the sense that, say, General Relativity or Conservation of Energy is a law. That is not true. As explained here (http://physics.stackexchange.com/questions/4201/why-does-the...) the basic laws of physics are time-symmetric, i.e. there's no currently known fundamental reason that entropy behaves the way it does.
2) I've read this story 20+ times, yet each time it gets me. I think the force of the story comes not from the scientific predictions but from the poignant depiction of humanity's futile fight against oblivion. Aren't all monuments erected for this purpose? The fact that the story is very light on the tech details paradoxically increases its punch.
3) The described technology is a curious mix of far-sight and ridiculous backwardness: In describing harnessing the power of the Sun, Asimov may have had in mind something like a Dyson sphere, which Dyson described in 1960. However, the technicians still use a teletype to communicate with Multivac in 2061!
4) One thing that I think Asimov got wrong fundamentally is that researching the "final question" should have taken all of Multivac's CPU capacity. It's stupendous that Multivac just runs that question on a separate thread while doing everything else. The Hitchiker's Guide gets this right: when Arthur asks a very powerful AI (the Nutrimatic Drinks Dispenser) to make tea it totally paralyzes the machine.
5) I've never been able to find a good interpretation of Cosmic AC's response "NO PROBLEM IS INSOLUBLE IN ALL CONCEIVABLE CIRCUMSTANCES."
Couldn't (4) just represent a fairly good design for Multivac so asking it one hard question doesn't lock it up for everyone else?
I prefer my space exploration to be done on a Nostromo than a Enterprise.
There is for example the Cyberpunk genre (starting from eighties) which predicts things much better. There are much less large scale inventions in that, and a lot of smaller, human life style changing things that were got right. Cyberpunk also started after the world took direction towards the current form of capitalism, and the utopian ideas originating from before sound strange today.
Some anachronisms are not really anachronisms - they are just proofs of the fact that the old way was in some decisive way better.
I might not be understanding the science correctly, but due to the specific phrasing of the question, would "Sure--here's a schematic for an LED that converts waste heat back into photons[1]" be an acceptable answer?
[1] http://www.physorg.com/news/2012-03-efficiency.html (Previously discussed on HN)
The more exciting detail is that computation itself doesn't increase entropy, at least not if reversible computing is use. Only errors or, rather, their correction do... So things may be more rosy than you might guess: http://arxiv.org/abs/quant-ph/9908043
Surely this post adds to the experience of some as do many others like it. The first step in this trend would be a Hacker New reading list composed of posts that fit this profile.
Secondarily you could have a way to inject each of the posts on that list into each users front page based on if they had seen it before (followed link checking or HN logs). If I'm new to HN perhaps my front page would have these scattered throughout.
Next you could use them as content on slow news days in combination with the per user information above.
I, for one, would love it if my local movie theatre re-ran Star Wars during slow months, and I wouldn't mind being (re)exposed to classic posts on Sunday afternoons :)
However many times classics are resubmitted, they will still find new and appreciative readers. Thank you lisperforlife & HN.
