Let's do the math. Lets say we re can re-equip the Curiosity rover and send it to an asteroid, asteroid 1981 Midas, to mine metal. We luck out, and after scraping off some cometary debris, it turns out that 1981 Midas is SOLID GOLD! Just we assumed it would be, based on the name. The rover then initiates its grizzled 1849 gold prospector protocol and jumps up and down whooping and yelling like crazy. Now it starts mining. How long before it turns a profit, in our scenario- which is at best very unrealistic but doesn't actually violate any laws of physics? The Curiosity rover cost about 2.5 billion dollars. Assuming our prospector rover costs the same, and assuming a gold price of $1250 / pound, it will need to mine two million pounds of gold- a thousand tons, a thousand times its own weight- to break even. That's ignoring the fact that mining metals is far beyond the capabilities of current space probes. That's ignoring that we have no easy way to get a thousand tons of gold back to earth. That's ignoring the fact that 2 million pounds is roughly equivalent to the entire world gold production, so you're going to depress the price and have to mine even more to break even, depressing the price further, putting the price of gold into a downward spiral.

Even a back-of-the-envelope calculation tells us that to mine anything from space, either (a) the cost of getting things to orbit and moving things through the solar system has to come down by orders of magnitude, (b) the price of the stuff being mined has to be very, very high- we're talking about gold, platinum, or Unobtanium, or (c) both. Anything you want for an asteroid, you can get cheaper right here on earth, because you don't need to travel to space and back. Dig deeper mines. Go to some godforsaken place like Alaska or Afghanistan. Develop undersea mining. And even if some substance, like gold, ever did become scarce on earth, it would be cheaper to develop substitutes or technologies that didn't depend on gold, or to improve recycling of resources, than to go into space for gold. Another way of looking at things: to send something into space requires an expensive machine sitting on top of an expensive rocket, supported by a small army of scientists, technicians, and aerospace contractors. Whatever you bring back has to be more valuable than everything you expended getting there. Right now, there's nothing in the known universe whose economic cost will justify the expense of going out and getting it.

It doesn't matter what you call it, the issue is that the manufacturing quality isn't up to the demanding requirements of a mass-murderer. If you want to slaughter a schoolroom full of kindergartners, you want to be sure your gun doesn't jam; you want something manufactured by a gun manufacturer, not some cheap plastic trinket squirted out of your Makerbot. Maybe someday the quality will be there. Right now you may be able to print something out that will kill people, but it's not a particularly reliable or effective killing machine. But we can dare to dream. After all, as the NRA tells us, the only answer to a bad guy with a gun is a good guy with a gun. Once everyone can print out their own fully functional, fully automatic M-16, I imagine that we'll enter a new era of peace and safety.

Which isn't to say that 3D printed guns couldn't have a niche in the near future. They would be perfect as untraceable weapons for one-off murders. Print the gun, walk up and shoot the guy in the back of the head, melt the gun down. Disposable handguns.

Yes, and people have the right to you know, not get shot in the face. The right not to have their children slaughtered in school shootings. The right not to worry about getting shot if they wander into certain parts of town. The right not to get shot by a gun trumps the right to own a gun.

The freedom argument is bullshit. In what way are Canada, the UK or Australia less free than the U.S.? In terms of political freedom they are as free or freer than the U.S. pretty much any way you care to look at it. And in what way is Somalia- a country where you can carry anything you want- a free country? Try wandering into one of the rougher areas of Chicago or DC and see how "free" you feel when you're worried that someone might shoot you. You don't have that kind of thing in Canada or the UK. Sure, there are rough places in every country where you might want to watch yourself at the bar, but it's not the same as worrying that someone could actually pull a gun on you.

You're right, we shouldn't be panicking about the idea that people can print out guns. We should be panicking at the thought that people can easily buy precision-made, high quality and relatively inexpensive semiautomatic pistols and assault rifles. Makerbot isn't the problem, the problem is Glock and Colt.

Taken to the logical extreme, the "guns don't kill people, people kill people" argument says any sort of gun control is illogical. Fully automatic AK-47s don't kill people, people kill people! Browning .50 caliber machine guns don't kill people, people kill people! Hand grenades don't kill people, people kill people! A plutonium implosion weapon doesn't kill people, people kill people! Ownership of a nuclear bomb doesn't violate people's rights, so we shouldn't restrict ownership of fissile material. Of course, if someone were to detonate a 20 kiloton weapon in a school and kill all the schoolchildren, and incinerate everyone for miles around, well should throw the book at them. But let's not get all crazy and talk about putting restrictions on enriched uranium. The fissile material, explosive lenses and triggers are just a tool, it's what people decide to do with it that matters, right?

The reason that argument sounds insane because it IS insane. Except for failed states like Somalia and Afghanistan, EVERY state accepts some limitations on the kinds of weapons that people can carry, the only difference is that some states apply more restrictions than others. The U.S. gun control laws are far more lax than in the UK, Australia, or Canada, but we have them- you can't just buy a machine gun. This always seems to get forgotten in discussions about gun control: gun control is already in existence, the only question is whether we need less, more, or to keep things the same. The US, UK, Australia and Canada all agree that some weapons are too dangerous to let people run around with, we just disagree about where to draw the line. Given that the US has an endless series of mass killings, and the other countries don't, it's not hard to see who made the right call.

Thank you, anonymous NRA supporter, for turning a discussion of a touching children's movie into a discussion about murder, rape, and assaulting the elderly. Because assaulting the elderly is precisely the kind of thing I associate with the sensitive, life-affirming films of Studio Ghibli and director Hayao Miyazaki. In fact, I think when you look closely, assaulting the elderly is the central message of Totoro.

Your anonymous tirade has shown us all the way. I think you are exactly the type of rational, not-at-all-insane person we want to help us all as a society to make informed decisions about how best to reduce gun violence and the slaughter of children. If this obviously well adjusted person says gun control doesn't work, let's all listen to him and everyone else who is fighting to keep those Glocks, AR-15 assault rifles and other implements of death on our streets!

Even the Unabomber used the U.S. mail...

A major issue here is that standard glass can wear down through abrasion pretty quickly. Glass is fairly hard stuff, with a Mohs hardness of 5 it's comparable to steel which is why you need specialized tools like diamond cutters to cut it. However, quartz- one of the most common minerals on earth and a major component of most sands and gravels- has a Mohs hardness of 7, so a bit of sand and grit can easily scratch and wear standard glass. Take a look at a piece of glass that's been on a rocky beach and you'll see that it's been worn down and frosted by the constant action of the waves and stones; thousands of cars a day driving over a surface and grinding pebbles and grit into it will have the same effect. It will wear grind down any texturing, and frost the glass such that it reduces the amount of light getting through to the solar cells. There are harder glasses out there, like the Gorilla Glass that smartphone screens are made out of, but it's unclear whether they've addressed this wear-and-tear issue or not.

That's not true. The homicide rate in the United Kingdom is 1.2 per 100,000. The homicide rate in Canada is 1.6. The homicide rate in Australia is 1.0 And the homicide rate for the US is 4.8 per 100,000. You can look it up on Wikipedia if you're so inclined ("List of Countries By Intentional Homicide Rate") but it's clear you've already made up your mind and are simply going to ignore any facts that don't support your preconceptions. Yes, the human tendency to murder other humans is a powerful force, and so a certain percentage of people who would otherwise be murdered by guns in the UK are murdered with knives, poison, or cricket bats, because those guns aren't available. But the end result of strict gun control is a per-capita homicide rate that is around 25% of the U.S. rate in the UK and 33% in Canada and 20% in Australia. The statistics don't lie, gun control saves lives.

I think it's time to start talking about real gun control in the United States. I'm not talking about banning a few models of assault rifles; I think the end goal of gun-control should be keeping rapid-fire weapons out of the public hands, which means requiring licensing for or simply banning all revolvers, semiautomatic pistols and semiautomatic rifles, creating something similar to the gun control laws seen in the UK. We've tried letting things run wild and all it's gotten us is thousands of deaths a year and an endless series of mass shootings. The next logical step is implementing the kinds of firearms controls seen in Canada and the United Kingdom, and I think the left needs to start pushing this seriously. No, Obama isn't out to get your guns... and it's a shame, because dammit, he SHOULD be. And if that takes a constitutional amendment, then we should pass a constitutional amendment- I'll line up to vote for that. Yes, it's in the constitution, but so was slavery, and we outgrew that. Times change, and a law written for muzzle-loaders is no longer useful in an age of machine guns. I'm tired of seeing thousands of people senselessly slaughtered every year because the political debate is held hostage by a handful of extremists. For too long we've played it the NRA's way and refused to talk about gun control. We need to start talking about gun control again, and nothing should be off the table.

Intelligent, informed speculation has a place and purpose. I remember Larry Niven's essay, "Bigger than Worlds" in this respect. He goes off into some metaphorical and literal deep-space territory here, but he's trying to constrain speculation in terms of the laws of physics. How would we build artificial worlds? He discusses Dyson spheres but can't figure out where the gravity comes from, so comes up with a compromise where you have a ring the diameter of Earth's orbit and spin it. This lead to the novel Ringworld; some engineering students later pointed out the structure's orbit was unstable, so in the sequel he adds in motors to stabilize the whole thing... obviously Niven's essays haven't led to any major, useful advances in building artifical worlds (although it did help give us the Halo franchise). But this sort of speculation- wondering what is possible, given the constraints of the real world, what is impossible and what is possible but just not realized yet- has led to major, useful advances. Arthur C. Clarke, another hard sci-fi author, was the first to sketch out the idea of orbital communications satellites. We don't have any cloned dinosaurs yet, but arguably Crichton's Jurassic Park helped spur people to do things like sequence the neanderthal genome. Virtual worlds are probably more advanced than they would be if Snow Crash hadn't sketched out what those worlds might look like and how they would function. Star Trek got people to think about how future computer interfaces might work. Perhaps more importantly, Star Trek got people to speculate about how future social and political structures might work in terms of sex, race, economics, and political boundaries. And soforth.

That being said, I don't think Adams really falls into that camp of informed speculators. He says at one point "If you put some scrubbers in the device I think there's a way to deal with pollution and climate change too. I saw some sort of tube-to-the-sky concept that was supposed to do that but I'm too lazy to search for the link." He's just screwing around. He's having fun playing with ideas, but can't actually be bothered to do the math or even Google something before saying it. It just comes across as self-indulgent and vain, not insightful or intelligent. For someone who spent so much time deriding people for being stupid or intellectually lazy, he's showing a lot of intellectual laziness himself.

If antidepressants are really the answer, why does America, with one of the highest rates of antidepressant use, also have one of the highest rates of depression in the world? If they were really effective, people should be less depressed, and in fact there's more depression and mental illness than ever. There's increasingly concern that antidepressants are actually making things worse. In the short term, antidepressants can be effective in managing the treatment of depression, for some people. The problem is that they can cause long-term changes in how the brain functions, such that the person becomes dependent upon the drug. This means that on quitting antidepressants, the depression is more likely to return than it would have been if it had simply been left to resolve itself. There have been a number of studies published that suggest that the long-term outcome of mental illness is worse when antidepressants are used. As far as I know, there isn't a single study that has shown that outcomes for depression are improved long-term- over the course of 5-10 years instead of 5-10 weeks- by the use of antidepressants.

Maybe antidepressants do have a role in treating mental illness, but given the risks- increased risk of suicide, the highly addictive nature of some of the drugs (especially ones with short half-lives) and the risk that they can make people worse than when they started, these should be a method of last resort for severe clinical depression, NOT a first-line treatment for everyone who seems moderately sad or anxious. There are a *lot* of things that have been shown to be potentially beneficial- cognitive behavioral therapy, exercise, light therapy, sleep therapy, and supplements like Omega 3 fatty acids, vitamin B, D, zinc and magnesium, cutting down on carbohydrates- which come without the risks posed by antidepressants.

Not a bubble, but maybe a froth, lot of little bubbles. We're not seeing the entire tech sector inflated, but we're seeing inflated prices in individual companies and within particular areas of the sector. At the height of the 1990's tech bubble, price/earnings ratios were about twice what they are now. Right now, buying $1 worth of earnings in a company costs about $19 worth of stock (Price/Earnings, or P/E, = 19). So if you buy $1 worth of a company, it will pay for itself in 19 years, assuming the earnings stay the same. At the peak of the dot com bubble in the late 1990s, buying $1 worth of earnings cost about $40 (P/E =40). So we'd have to see the prices of companies double to get back to where we were during the peak of the dot com bubble.

That being said, there are individual companies that are massively overvalued. Facebook is trading at 77 times earnings, Netflix is trading at 151 P/E, Amazon is trading at 489 P/E, which means that one dollar invested in Amazon will pay for itself if half a millennium at current earnings levels. That's pretty much the way stocks traded during the dot-com bubble. Tesla doesn't even have a P/E ratio since they can't actually turn a profit, but their stock soars none the less, which is again classic bubble behavior. So yes, these individual companies show bubble-level valuations of the sort we saw during the dot com bubble. But this isn't the case for all companies. Google is trading at a P/E of 30, Microsoft at a P/E of 15, Apple at a P/E of 14.67. Google is probably fairly priced given its rapid growth, Microsoft is underpriced assuming they ever manage to get their shit together (debatable), Apple is a bargain even if they manage to grow modestly in the next few years.

So yes, there are individual companies that are showing bubble-like behavior but it's not spread across the entire sector the way it was in the dot-com bubble. There are pockets of madness but it's not yet systemic. And even the companies that are wildly overvalued are solid companies. Maybe they're overpriced, but I don't think anyone doubts that Amazon, Netflix, and Facebook will continue to be important companies, we're not talking about Pets.com here.

How in the hell can you write an article called "The World's Worst Planes" and not include the massively over-budget and behind-schedule F-35 Lightning II?

The whole plan seems pretty sketchy. You can't just create a mashup of two distantly related animals and automatically expect to get something viable out of the mix. Mammoths and Asian elephants aren't actually that closely related- African elephant, Asian elephant, and mammoth are thought to have diverged around six million years ago, so mammoths are about as close to Asian elephants as chimps are to humans.

Hybridization can result in improved fitness if the parents aren't too distantly related. However, the more distant the relationship between the parents, the less likely the offspring are to be viable. Humans and Neanderthals split around 600,000 years ago and were able to successfully interbreed. However, horses and asses split around four million years ago. The offspring- mules and hinnies- are healthy, but they are either sterile or have reduced fertility. Breeding more distantly related animals produces non-viable offspring.

The article does mention that there have been hybrids between Asian and African elephants, which are slightly more distantly related than Asian elephant and mammoth. What the article neglects to mention is that the only known example of an African-Asian hybrid died several weeks after birth; there are other reports of hybrids being born but strikingly no reports of any surviving. This suggests that mixing mammoth and Asian elephant DNA is going to produce an unhealthy or non-viable offspring.