The Wieliczka Salt Mine, with its pure-salt chandeliers, began operations in the 13th century, drew tourists as early as the 15th century, and became a United Nations World Heritage site in 1978. This year, it got yet another tourist treatment: It's now explorable via Google Street View.

In medieval times, when salt was precious, the mine brought great wealth to Poland. Over the centuries, the men who mined it filled it with religious and historical sculptures and underground chapels alongside their workshops. Older miners taught younger ones how to carve in salt. In modern times, mine officials invited artists to create other sculptures in the mine's passageways.

In an inherently dangerous job, the miners used the chapels to pray for their safety, according to the United Nations Educational, Scientific and Cultural Organization. Everything in the famed Chapel of St. Kinga that is not carved from rock is made of salt, including the chandeliers and the Virgin Mary statue in her salt-crystal alcove.

The mine has nine levels and about 190 miles of galleries, although only a small proportion of that is open to the public. In Google Street View, you are able to visit two different levels and see a few different rooms.

Click here to enter the gallery

In The Drug Book, author Michael C. Gerald details 250 milestones in the history of drugs, from the introduction of arsenic and Xanax to the passage of the 1906 Pure Food and Drug Act, the first major legislation aimed at protecting the public from dangerous medications. We asked Gerald, a professor emeritus of pharmacy at the University of Connecticut, to select a handful of the most important milestones. Read on to see what he picked.--Eds

Five months after the Netherlands-based private spaceflight project Mars One announced it would begin accepting applications for a one-way trip to the red planet, 202,586 people from more than 140 countries have submitted videos explaining why they should be chosen for the mission.

The first of four selection rounds ended August 31. Now, the Mars One selection committee will spend the next several months narrowing down the applicants. There are even plans to launch a reality TV show to choose the final candidates. The goal is for 24 to 40 people to begin a seven-year training program in 2015. Then, working with the private space flight company SpaceX, Mars One hopes to send the prospective Martian settlers to the red planet in teams of four, beginning in 2023.

Read more about what a human Mars colony would be like here. Then check out our Q&A with a Los Angeles-based video game designer who applied for the program earlier this year.

Did you apply to the Mars One program? We want to hear your story! Email rose.pastore@popsci.com with a link to your video application.

Labor Day has passed, and we're already mourning summer, but at least there's the fall foliage to look forward to. If you're wondering when to watch, the trip-planning site Roadtrippers put together this map showing peak leaf-shedding days for the whole country.

A few small parts of the country will reach peak season later this month, but the good majority will be in prime-time at some point in October (broken down by early, mid-, and late in the map). Some areas of the South and Southwest, meanwhile, will have to stick it out until November.

Fun! You could even go on a leaf-chasing tour with this, if you had a month and a ton of gas to burn. Or you could just be patient and wait for the best foliage to hit your area. Unless you live in southern Arizona or Texas, or anywhere in Florida, in which case enjoy your next five months of summer.

[Roadtrippers]

Everyone and their mother wants to send people to Mars these days. Dutch spaceflight nonprofits, President Obama, and even Buzz Aldrin have seriously discussed plans to put humans on the inhospitable planet in the next few decades. But what happens when they get there?

The aforementioned nonprofit, Mars One, hopes to turn the first human colonization of another planet into a reality TV show, allowing people on Earth to watch the settlers' every move. As the Guardian points out, though, the first few permanent Mars colonists will face more than just a freezing, dust-ridden environment. They're also likely to careen over the edge of psychological instability as everyone back home watches.

The combination of utter social isolation, eternal confinement in a tiny Mars-One-constructed habitat, the 24-hour surveillance of reality TV, and a lack of mental health services will converge to drive the few dozen people selected to die on the red planet completely bonkers. Even astronauts who know they're coming home eventually can become depressed and anxious in the lonely vacuum of space. Imagine being stuck in a tiny survival pod with only a few people, with transmission delays impeding your ability to keep in touch with people on Earth, unable to travel freely outside on the freezing, barren dustball that is the Martian surface. Forever. Until you die, going down in history as one of the first boldly idiotic explorers of a new world.

"Mars One is either ignoring the psychological consequences of colonisation or failing to disclose them," the Guardian notes. "Either way, if their plan goes ahead - and for the sake of the colonists we might hope that it doesn't - then Nasa's manned mission in the 2030s may well be dubbed Mars Rescue." Until they send a team of psychotherapists, best to explore from home, for now.

Read more on the psychological ramifications of a permanent Mars colony here.

NASA's LADEE spacecraft launched from Wallops Flight Facility in Virginia on Friday night, en route to an orbital trip around the moon. The night-flight provided photographers like Ben Cooper of LaunchPhotography.com an opportunity for some stunning shots.

This one probably tops them all, though. Taken from the top of Rockefeller Center in New York, the shot is a timelapse of LADEE's trip. Wow, right? The Empire State building is lit up for the U.S. Open, which only made the photo all the more amazing.

You can check out more of Cooper's work here.

Just as Scottish and Irish accents are clearly different from American English ones, so are Scotch and Irish whiskeys chemically distinct from their American counterparts, and ongoing research is analyzing exactly how.

Food science researchers at the University of California at Davis have been studying different whiskies to determine whether they can tell them apart, scientifically. Research director Thomas Collins gave a talk at the American Chemical Society's annual meeting today about the university's work, especially on American whiskeys.

"Right now, we can do a pretty good job of separating, for example, Scotch whiskies from bourbons and other American whiskeys and also Canadian and Irish whiskeys," he said during the talk, which the American Chemical Society recorded. "When you narrow it down into whiskeys from a particular region, the process gets a little more difficult because they're more similar to each other." The researchers are looking into the data more closely to try to distinguish chemically between American whiskey types, Collins said.

In the future, Collins' team hopes their studies will be able to tell distillers what practices make for the tastiest whiskey. For example, they could be able to answer whether whiskeys taste different if they're aged in different parts of the same warehouse, Collins said. Their chemistry could also help people identify whether particular bottles of whiskey are genuine, although there are already techniques for doing that.

"Ethanol is a good solvent and it will extract a number of things from the barrel," Collins said.The major chemicals that Collins' team uses to distinguish whiskeys from one another include some that come from the grain, some from the fermentation process, and some from the wood barrel in which whiskey ages. "Ethanol is a good solvent and it will extract a number of things from the barrel," Collins said.

It's the relative concentrations of about 30 to 50 chemicals that distinguish any two given whiskeys from one another, Collins said. Those chemicals include terpenes and terpenoids, which may come from either the barrel or the grain; fatty acids, which may come from either yeasts or plants; and polyphenols, such as tannins, which come from the aging barrels and vary by both distiller and a whiskey's age.

For their research, Collins and his team analyzed about 60 American whiskeys. They used two common chemical techniques, high-performance liquid chromatography and high-resolution mass spectrometry, which are able to separate the compounds in a mixture and tell scientists some facts about those compounds, such as their weights or some information about their structures. Researchers then used other data to deduce what those different compounds are. They also performed statistical analyses to check the differences between the concentrations of different chemicals in different whiskeys.

"Bioluminescent" is the preferred adjective for animals and fungi and bacteria (and bacteria-powered lamps!) that naturally glow. Information designer Kanny Yeung mapped those species in an expansive infographic that breaks down the creatures' family trees, first organizing them by either fungi or animalia, then moving along to individual species.

A bar next to the species name represents the color of the creature's glow, the size of the organ that causes it to glow, and why it glows. (A key at the bottom of the infographic has symbols for distraction, attraction, and more.) Plenty of species are on here--look at the colossal squid!--but it also seems slightly incomplete, and it's not quite clear why. Some bioluminescent fish don't have colored bars next to their names. Is it because the organs that create the light are too small? Because there's not enough info on those species? Something else? We're not sure.

Still, there are enough names here to keep you busy Googling weird ocean-dwellers for quite a while. See the full infographic here.

[Kanny Yeung]

Big cities have a problem: they weren't designed big. Roads that made sense for pedestrians and horses work less well for delivery vans and 18 wheelers. So MIT's Megacity Logistics Lab has created an open-source web platform that is designed to expose logistical problems in eight major cities. The goal: to give urban planners a tool for designing more efficient cities in the future.

Eleven MIT students partnered with students from local universities in Mexico City, Rio de Janeiro, Beijing, Santiago, Sao Paulo, Kuala Lumpur, Madrid, and Cambridge Massachusetts, to collect data on mundane aspects of daily urban life, such as where stores are located and how often they receive truck deliveries. Then they plotted the data onto interactive maps to show some of the logistical problems--from traffic congestion to inadequate loading areas--associated with pouring supplies into a big city designed with small-city bones.

Take the intersection in Cambridge, Massachusetts, pictured above. The map shows several businesses in the area that rely on the same few roads for deliveries. Flip on the map's traffic filter, and you'll see a single freight unloading on Hampshire Street that lasted 18 minutes and delayed seven vehicles, and another on Cambridge that lasted 17 minutes and affected 40 vehicles. Cities are tricky!

So what to do with all that depressing data? While it won't do anything to straighten Boston's crooked streets, it could help inform how we plan the cities of tomorrow, says Edgar Blanco, research director at MIT's Center for Transportation and Logistics. Planners could design streets such that they're able to accept deliveries without blocking traffic for miles. Or they could decide to ban certain vehicles during busy hours or in crowded parts of a city.

[MIT]

Earlier today, Sony announced a new gadget: the PS Vita TV, a cheap set-top box that'll let users play some (only some!) games and stream video through their televisions.

The Vita TV can use video streaming apps like Hulu, which play video without saving the full file, but more importantly, the box can download and play games. Users download the games through Sony's online store, then with a standard PlayStation control, play them. The Vita TV also comes with a slot that can play physical copies of games for the PS Vita, Sony's latest handheld gaming machine.

So: Which games can you play with this? Right now, the box can't handle the high-end stuff the PlayStation 3 plays. Instead, it plays games with less demanding graphics: there are digital versions of PlayStation 1 games, PSPS games (Sony's previous-generation hand-held console), and PS Vita games (although Sony says not all of the latter will be supported). The box will also be able to hook up to another TV and remotely stream PlayStation 4 games, provided your PS4 is connected to another TV on the same network.

You're out of luck right now if this sounds up your alley and you're not in Japan: the PS Vita TV is being released there first, for about 10,000 yen, or about $100, on November 14. There's also a 15,000-yen version (about $150) with a controller being released. No word on when the box is coming to other countries.

Click here to enter the gallery

Now underway in the San Francisco Bay is the America's Cup Finals, the last stage of this year's America's Cup international sailing yacht competition. After four of nine races, the current trophy-holding team, America's Oracle Team USA, has won one race while the challenging Emirates Team from New Zealand has won three.

Since the first America's Cup race in 1851, advances in technology have made the yachts significantly faster and stronger. Here's a gallery of the extreme tech behind some of the world's fastest boats.

Upcoming health care reforms could reduce one of the more mysterious disparities in the U.S.: The difference in infant mortality rates between black and white babies, the Los Angeles Times reports. Black babies are more than twice as likely to die before they turn one, compared to white babies.

In a new feature, the Times outlines the problem of disparate infant mortality rates by profiling two babies and their families. That's Adris Bradley at the top of the page on the Times's site, wearing the cutest-ever soft plastic baby glasses. It's a relief to see him so healthy and happy there, especially if you scroll down to see how he looked when he was born at a paltry 1 pound, 8 ounces.

There's been a lot of talk about improving black babies' health by upping the number of black moms who get prenatal care-vital for mom and baby-but researchers now think the roots of infant mortality inequality reach further back in time than that. The Obama Administration's controversial health care reforms are set to expand Medicaid coverage, require all Americans to have health insurance, and make other changes to health insurance in the U.S. Different parts of the law will take effect at different times; some have already come online. Overall, researchers hope the changes will reduce other health inequalities that affect black women disproportionately, and that may affect any babies they have down the road, including lower rates of health insurance coverage and higher rates of diabetes and obesity.

Nevertheless, equality may require changes on other fronts, too. Although differences in income, education and health care access explain some of the inequity in American infant mortality rates, they don't explain everything. Babies of highly educated black mothers, such as Adris' mom, are still at higher risk than babies of white women with less education. The cumulative effects of racism and stress seem to make a difference, too, U.S. Health and Human Services Department researcher Kay Johnson told the Los Angeles Times.

[Los Angeles Times]

Modern smartphones usually offer some kind of security option to let you into the phone. The iPhone has the a four-digit PIN-like passcode, Android phones have a swiping pattern, Windows Phone has a numeric or text-based password. Those work OK, but they're pretty hackable, and could well be improved by new technologies. Insidious and scary technologies. Here's the rundown.

The Problem

A large percentage of users select from a few easy-to-remember numbers. A four-digit PIN like the iPhone uses has around 10,000 possibilities, but the four most commonly used PIN numbers are used about 20 percent of the time. If the person trying to hack your phone knows anything about you--your birthday, when you were married, your address--it makes it that much easier to guess your PIN.

A PIN is easy to forget, which is why people often pick patterns that are easy to remember, like 1-2-3-4, which you should not use. And knowledge of the password is its only security; the security of an alphanumeric password does not involve the identity of the person entering it. The iPhone doesn't attempt to see who is entering the password; if it's right, that's all that matters.

Biometrics: The Solution?

Biometrics refers to the practice of identifying someone based on physical characteristics, rather than on an alphanumeric key. The most well-known biometric technique is fingerprinting, but biometrics extends to all kinds of other ideas, from retinal scanning to analysis of a person's gait to detection of a person's particular smell (really). Some of these are good fits for smartphone security! And some are not. (You probably won't be holding up your phone to your armpit for smell identification anytime soon.)

Fingerprinting: The grandpa of biometrics has a lot going for it. It requires minimal hardware, it's well-understood, and it's non-invasive. There are a few different ways to perform a fingerprint scan in a way that might be useful on a smartphone. There's optical scanning, which is basically a digital camera; capacitance scanning, which measures the minute differences between electrical stimuli in the ridges and valleys of your fingerprint; and 3-D scanning, which makes a digital map of your finger, sort of like a Microsoft Kinect.

Capacitance scanning seems the most likely here; a company called AuthenTec has made some strides in capacitance fingerprint scanning on phones, partnering with Toshiba for the Regza T-01D Android phone. And, not at all coincidentally, Apple bought AuthenTec just over a year ago.

Will Apple opt for this method? Well, we haven't ever seen a scanner of this type integrated into a button. The iPhone has very few buttons; the home button sees a lot of action, and the last thing you want a fingerprint scanner to have to deal with is a lot of gunk and debris piling up in there from undue use. That's why the Toshiba Regza put the scanner on the back, where it's less likely to accumulate dust and dirt that could foul up its inner workings. And fingerprint quality is often degraded over time, thanks to repeated manual labor or skin buildup. It can also be hacked with gummy bears. Seriously.

Face Recognition: Face recognition already exists! Ever since Android 4.0, back in 2011, Android phones have had face recognition as an unlocking option. The iPhone doesn't have face recognition built in, but you can snag an app that'll do it just as easily. Face recognition is great because it doesn't require any extra hardware--the front-facing camera on your phone is just fine for this--and, theoretically, when you turn on your phone, you've already got your face turned toward it, so you don't have to do much adjusting.

There are problems with this system; it's not particularly secure, for one thing. Like most biometrics that rely on mere optics, face recognition tools can be fooled with a good picture. It also depends on the quality of the teeny-tiny front-facing camera in your phone; what if it's dark? What if the camera breaks? What if there's blinding light? Any of those issues could make face recognition difficult.

Will Apple try to include this feature? Possibly! The technology (and precedents) already exists, so it'd be easy to implement. But on Android, it doesn't work particularly well, so Apple may decide it's not worth the trouble.

Retinal Scanning: Ah, here's where we get into the fun stuff, the stuff that doesn't quite exist yet. The retina is the part of the eye way at the back, a thin layer of tissue that serves basically the same function as a piece of film in a camera. It requires a complex series of blood vessels to feed it, and that configuration of blood vessels is unique to each person.

A retinal scan blasts some low-energy infrared light into the eye. The blood vessels don't reflect as much light as the surrounding tissue, so if you capture the image of the infrared reflection, you've got a unique map of the retina. It's very accurate, basically impossible to fool, and delivers results pretty much instantly. It's hard to fool with a fake retina; retinal scans can adjust to suit the movement of the retina upon getting blasted with the infrared light, so it's not easy to fool with a handheld fake eyeball.

The downsides? Certain diseases, like glaucoma, can alter the pattern of blood vessels in the retina, as can eye conditions like astigmatism and cataracts. But those are minor problems. The real issue with retinal scanning is that it requires an infrared beam directed into your eyeball, which is invasive and not terribly convenient. Imagine having to stick your eye onto a scanner on the back of your phone every time you wanted to check your email. Not super fun!

Will Apple use it? Not yet. Retinal scanning requires extra hardware, which isn't quite small enough yet to cram into a phone.

Iris Scanning: The iris is the colored part of the front of your eye, surrounding the pupil. The iris is also unique to each person, and much less likely to change over time than a fingerprint. It's also easy to scan, requiring only a camera and perhaps a slight infrared illumination to make things easier. The tech already exists as an external case, but wouldn't be too difficult to implement into a phone itself.

Iris scanning, though, can also be fooled by a photo. But it's harder to take a super sharp, high-definition photo of an iris compared to a person's face, which makes fooling an iris scanner with a photo relatively difficult. Still, it's far from impossible.

Will Apple implement it? Probably not; it's as yet unproven for mobile devices (without an external case, that is) and it's sort of awkward to use to unlock a phone. (How do you aim it precisely at your iris if you can't see the screen?) But the technology's there, so we wouldn't rule it out.

Electrocardiogram: According to a biometrics company called Bionym, your heartbeat is just as unique as your iris or fingerprint. The company very recently showed off its Nymi bracelet, which takes an electrocardiogram reading of your heart rate through your wrist. Then it uses Bluetooth to tell your phone to unlock.

It's a super promising technology; it could be nearly impossible to fool or replicate, low-power (because it relies on an external sensor), and cheap to implement. The downsides? It might take longer than you'd prefer to actually measure your heart rate, and it requires a wristband, which people may not feel like wearing.

What This Means

Biometrics are almost certainly coming, in some form, to smartphones. Whether it's this generation or an upcoming one, whether it's Apple or Samsung or Motorola, someone is going to figure out how to implement biometrics in a way that makes sense. Face recognition is already here!

But given the uproar over PRISM, people may also find it objectionable to subject themselves to any sort of identification, even if it's voluntary and even if it may assist with security. If you scan your retina to get into your iPhone, Apple has that data, Verizon (or whatever carrier you use) has that data, and we know from experience that if one of those companies has data, the government has access to it, too. And if the government has access to biometric data, that means they'll be able to link your fingerprints, heartbeat, iris, or retina to your email address, your Twitter account, your Facebook, your YouTube, your Instagram. It would be very, very easy to create a huge database that properly associates physical identifiers to your digital life. And that's pretty scary.

Are biometrics a good way to secure a phone? Sure, if you're talking about merely stopping people from getting into your data when they physically have possession of the phone. But that's not really how hacking is done these days; if that happens, both Android and iOS allow you to remotely wipe your phone of all its data. Biometrics could have the totally unintended consequence of making you much more vulnerable to hacking, simply by making your physical phone more secure.

A disembodied jet engine, attached to a hulking air vent, sits in an outdoor test facility at the Culham Science Center in Oxfordshire, England. When the engine screams to life, columns of steam billow from the vent, giving the impression of an industrial smokestack. Engineer Alan Bond sees something more futuristic. "We're looking at a revolution in transportation," he says. For Bond, the engine represents the beginning of the world's first fully reusable spaceship, a new kind of craft that promises to do what no space-faring vehicle ever has: offer reliable, affordable, and regular round-trip access to low Earth orbit.

Bond and the engineers at Reaction Engines, the aerospace company he founded with two colleagues in 1989, refer to the future craft as the Skylon. The vehicle would have a fuselage reminiscent of the Concorde and take off like a conventional airliner, accelerate to Mach 5.2, and blast out of the atmosphere like a rocket. On the return trip, Skylon would touch down on the same runway it launched from.

Bond's Synergistic Air-Breathing Rocket Engine (Sabre)-part chemical rocket, part jet engine-will make Skylon possible. Sabre has the unique ability to use oxygen in the air rather than from external liquid-oxygen tanks like those on the space shuttle. Strapped to a spacecraft, engines of this breed would eliminate the need for expendable boosters, which make launching people and things into space slow and expensive. "The Skylon could be ready to head back to space within two days of landing," says Mark Hempsell, future-programs director at Reaction Engines. By comparison, the space shuttle, which required an external fuel tank and two rocket boosters, took about two months to turn around (due to damage incurred during launch and splashdown) and cost $100 million. Citing Skylon's simplicity, Hempsell estimates a mission could cost as little as $10 million. That price would even undercut the $50 million sum that private spaceflight company SpaceX plans to charge to launch cargo on its two-stage Falcon 9 rocket.

The engine produces incredible heat as it pushes toward space, and heat is a problem. Hot air is difficult to compress, and poor compression in the combustion chamber yields a weak and inefficient engine. Sabre must be able to cool that air quickly, before it gets to the turbocompressor. In November, Reaction Engines hit a critical milestone when it successfully tested the prototype's ability to inhale blistering-hot air and then flash-chill it without generating mission-ending frost. David Willetts, British minister for universities and science, called the achievement "remarkable."

The Skylon concept has also impressed the European Space Agency (ESA), which audited Reaction Engines' designs last year and found no technical impediments to building the craft. The bigger challenge may be securing funding. While ESA and the British government have invested a combined $92 million in the project, Bond and his crew plan to turn to public and private investors for the remaining $3.6 billion necessary to complete the engine, which they say could be ready for flight tests in the next four years. Building the craft itself would require a much heftier investment: $14 billion.

The quest for a single-stage-to-orbit spaceship, or SSTO, has bedeviled aerospace engineers for decades. Bond's own exploration of the topic began in the early 1980s, when he was a young engineer working with Rolls-Royce as part of a team tasked with developing a reusable spacecraft for British Aerospace. That's when he came up with the idea of a hybrid engine. But the team struggled to figure out how to cool the engine at supersonic speeds without adding crippling amounts of weight. "By the time the plane hits Mach 2 or so, the air becomes very hot and extremely difficult to compress," Bond says. Rolls-Royce and the British government, doubtful that an easy and economical solution existed, canceled the program's funding.

NASA and Lockheed Martin, meanwhile, had their own plans for a fully reusable spacecraft, the VentureStar, intended as an affordable replacement for the partially reusable space shuttle. The VentureStar demonstrator, called X-33 (which graced the cover of this magazine in 1996), was a squat, triangular rocket that would take off vertically and glide back to Earth just as the shuttle did. Eliminating the expendable rockets needed to boost the shuttle into space could theoretically reduce the cost of launches from $10,000 per pound to $1,000 per pound. But by 2001, after sinking more than $1 billion into the project, the agency pulled the plug, citing repeated technical setbacks and ballooning costs. "We backed off because we felt it was better to focus our efforts on other, less costly ways to get payloads to orbit," says Dan Dumbacher, NASA's deputy associate administrator for exploration systems development, who spent two years working on the X-33.

With the shuttle now retired, and companies such as SpaceX under contract to resupply the International Space Station (ISS), NASA has doubled down on expendable boosters as a means of sending humans and probes well beyond Earth's orbit. NASA's new platform for deep-space exploration, the Space Launch System, will be the most powerful rocket ever built. The agency's focus on space exploration, and the need for big rockets to achieve it, means NASA no longer needs to build its own platforms just to get cargo into orbit. "From a pure technical perspective, we'd all love to go do SSTO," Dumbacher says. "But we're focused on making sure we get humans farther into space, and that's an expensive proposition."

Expendable rockets make sense for missions beyond low-Earth orbit. They can haul more cargo and more fuel than single-stage craft. Rockets also offer reliability-on average, only one out of 20 launches fail, in part because they suffer no wear and tear from repeated use. Finally, rockets come with fewer R&D costs, as much of the technology has existed since the 1960s.

But for routine missions to the ISS, or to park a small observational satellite in orbit, affordability becomes a critical consideration. SpaceX CEO Elon Musk told an audience at the National Press Club in 2011 that private spaceflights would need to follow a model closer to that of airlines. "If planes were not reusable, very few people would fly," he said. SpaceX plans to make rocket stages reusable, but there are drawbacks to that, too: While it is possible to recover rocket stages, designing bits and pieces to survive reentry in good working order adds a level of complexity and cost.

Fly anywhere in the world in under four hours.
Hempsell says Skylon could potentially make 100 flights annually-which, if true, could in its first year recoup the money spent in R&D and construction, leaving only expenses like fuel, maintenance, and overhead. And Bond's engine technology, aside from keeping a launch vehicle intact from start to finish, offers another advantage: supersonic aviation. "It could enable an aircraft to fly anywhere in the world in under four hours," says Bond.

When air strikes an engine at five times the speed of sound, it can heat up to nearly 2,000 degrees Fahrenheit. Bleeding off that heat instantly, before the air reaches the turbocompressor and then the thrust chamber, was the most onerous technical challenge for Reaction Engines engineers. Bond's solution is a heat exchanger that works by running cold liquid helium through an array of tubes with paper-thin metal walls. As the scorching-hot air moves through the exchanger, the chilled tubing absorbs the energy, cooling the air to minus 238 degrees Fahrenheit in a fraction of a second. Bond says his exchanger could handle about 400 megawatts of heat (equivalent to a medium-size natural-gas plant). "If it were in a power station, it would probably be a 200-ton heat exchanger," he says. "The one we've built is about 1.4 tons."

For rocket scientists, nothing matters more than weight. "Each pound you put into orbit requires about 10 pounds or so of fuel to get it there," says NASA's Dumbacher. "The challenge with the SSTO has always been to get the craft as light as possible [and generate] as much thrust as possible." Bond estimates that Skylon would weigh about 358 tons at takeoff and hold enough hydrogen fuel to carry itself and about 16.5 tons of payload-about the same capacity as most operational rockets-into orbit.

If and when the engine passes flight tests, one of Reaction Engines' plans is to license the technology to a potential partner in the aerospace industry. Bond hopes the recent success of the heat exchanger will inspire interest. After 30 years of research, it has certainly inspired him. "It represents a fundamental breakthrough in propulsion technology," he says. "This is the proudest moment of my life."

This article originally appeared in the September 2013 issue of Popular Science.

Yes, the universe itself will eventually outpace the speed of light. Just how this will happen is a bit complicated, so let's begin at the very beginning: the big bang. Around 14 billion years ago, all matter in the universe was thrown in every direction. That first explosion is still pushing galaxies outward. Scientists know this because of the Doppler effect, among other reasons. The wavelengths of light from other galaxies shift as they move away from us, just as the pitch of an ambulance siren changes as it moves past.

Take Hydra, a cluster of galaxies about three billion light years away. Astronomers have measured the distance from the Earth to Hydra by looking at the light coming from the cluster. Through a prism, Hydra's hydrogen looks like four strips of red, blue-green, blue-violet and violet. But during the time it takes Hydra's light to reach us, the bands of color have shifted down toward the red end-the low-energy end-of the spectrum. On their journey across the universe, the wavelengths of light have stretched. The farther the light travels, the more stretched it gets. The farther the bands shift toward the red end, the farther the light has traveled. The size of the shift is called the redshift, and it helps scientists figure out the movement of stars in space. Hydra isn't the only distant cluster of galaxies that displays a redshift, though. Everything is shifting, because the universe is expanding. It's just easier to see Hydra's redshift because the farther a galaxy is from our own, the faster it is moving away.

There is no limit to how fast the universe can expand, says physicist Charles Bennett of Johns Hopkins University. Einstein's theory that nothing can travel faster than the speed of light in a vacuum still holds true, because space itself is stretching, and space is nothing. Galaxies aren't moving through space and away from each other but with space-like raisins in a rising loaf of bread. Some galaxies are already so far away from us, and moving away so quickly, that their light will never reach Earth. "It's like running a 5K race, but the track expands while you're running," Bennett says. "If it expands faster than you can run, you'll never get where you're going."

This article originally appeared in the October 2011 issue of Popular Science magazine.

In 2010, the U.S. Army went to textile manufacturer Polartec with a problem: Troops needed a jacket that would breathe when they worked up a sweat but would also hold onto warmth when they sat still. Down and synthetic insulations don't allow this to happen. They require quilting and tightly knit, less-breathable fabrics to hold them in place and keep them dry. Polartec worked for more than a year to develop an insulation without those constraints. Last year, it gave the Army Polartec Alpha.

An Alpha-based jacket consists of a sheet of insulation sandwiched between loosely knit, breathable fabrics. When it's hot, sweat evaporates; when it's cold, Alpha traps warmth in its thousands of tiny air pockets. This fall, a dozen companies, including Marmot and The North Face, will release Alpha-based jackets. And Polartec will make Alpha in multiple thicknesses, so the jackets will only get warmer from here.

This article originally appeared in the September 2013 issue of Popular Science.

Early in the history of the U.S.' space program, space ice cream caught the imagination of American youngsters. Now, NASA and other researchers are developing a different kind of space food-space-grown vegetables, whose little roots would never touch Earth. (And which could actually be tastier than those weird, dry ice cream blocks.)

Modern Farmer has a feature today covering ongoing research into growing edible plants in space. There's a NASA effort to send romaine lettuce planters to the International Space Station, programs investigating crop production in Mars-like environments, and longer-term projects looking to grow soybeans and grains. Such space-farmed produce could save on the weight of the supplies astronauts need to bring with them; provide astronauts with a tastier and more nutritious diet; and even offer some psychological comfort. One of my favorite parts of the feature? The excerpts from American astronaut Don Pettit's writings about a zucchini plant he brought to space not for food, but just for fun. Go check it out.

[Modern Farmer]

greetings! I'm live blogging today's iPhone event, at which we're expecting to see at least one new iPhone, from my old iPhone 4S, which is moderately broken. There's a hairline crack on the left side of the screen, which is unsightly and also sometimes makes it hard to select things on that side. The back is pretty much shattered, which is a recent development. (I put the iPhone on the armrest of my couch and the. N kicked it off while napping, like a dog having dreams about chasing squirrels except I think that day I literally had a dream in which I bought too many radishes (???).)

12:15: haha omg HTML is SUCH A BITCH to use on an iPhone. This is going to be slow as hell. Also my phone is already VERY hot from the effort of just setting up this post.

12:18: the cracks on the back of the phone are shedding small shards of glass into my palm.

12:20: whoops I guess the HTML screwed up the bold text on that last update. My editors aren't allowed near this post, btw. It's probably wise of them to distance themselves from it.

12:26 I'm also using 3G because 1. That's the only network his shitty old phone has and 2. I've never been able to figure out how the in-office wifi works here at popsci. I'm a professional tech journalist btw

12:30: who the hell decided GLASS was a good material for a thing you fumble with while drunk. Jon I've is this your fault

12:35: I'm sitting at my desk, with a nice new iMac and a LEYBOARD AND MOUSE and an extra monitor and typing this on a cracked 3-inch screen like an idiot

12:37 I forget where the carrot symbol is every single time I need to type it, the iPhone is not liveblog-friendly, 4/5 stars

12:39 I messe up the closing HTML tags again