Tour de France Physics

It’s Tour de France time. What goes best with long sporting events? Physics is the answer. Here are some summaries of older posts about physics and cycling.

In one of the stages of the Tirreno-Adriatic race in 2013, there was a 27 percent gradient. That’s pretty steep for a race. Many cyclist would just have to walk their bike up such an incline. But how steep is too steep? There are a few different reasons that a cyclist couldn’t make it up an incline.

• Limit due to human power. As a cyclist rides up an incline at a certain speed, it requires energy to move up the hill (work against gravity). Based on my estimations, a human with a 300 Watt output could go up a 20 percent gradient at 2 m/s.


• Limit due to center of mass. Of course you can’t ride up a vertical wall, a cyclist would flip backward. The key is that the center of mass of the human-bike system must stay in front of the rear wheel. Based on this, I estimate a cyclist leaning forward could conquer a 93% gradient (this is an incline of 43 degrees).


• Limit due to friction. What prevents the bike from sliding down the incline? Friction depends on the force the ground pushes on the bike (the normal force). At a steeper incline, this force and thus the frictional force decrease. With some estimations of the coefficient of friction, I get a maximum gradient of about 80 percent.

There is one more possible gradient limit – it’s in the homework questions below. Here are all the details from the original post.

What if you put your bike in a super aerodynamic shell with a lower profile? How fast could you go? Could you go 100 mph? If you assume a small enough cross sectional area and drag coefficient then yes. If you have a 1,000 watt human you could go 100 mph. 1,000 watts seems crazy – but it’s not too crazy for very short periods of time.

Here is the whole post with the details.

In 2010, Cancellara would have such awesome attacks that people wondered if he was cheating with a hidden motor in his bike. Does he cheat? No. There are no hidden motors. If you look at a video of one of his attacks, two things happen. First, Cancellara is going just a little bit faster than the pack. Second, he has a slightly higher acceleration. These two things together make his break away look more dramatic. Here are the details.

But what if you really did have a hidden battery in your bike? In this other post, I estimate that you could have a 1.6 kg hidden battery that would give you about 500 watts for 1.5 hours. That’s just an estimate.

What happens if you are riding a bike both into and against the wind? It turns out that the headwind hurts you much more than a tail wind benefits you. Why? Two reasons. If you make a round trip, you will have a lower speed (and longer time) going against the wind. Also, if the air drag is proportional to the relative air speed squared, a little increase in wind means a major increase in required power.

Here is the full post.

How do you learn to ride a bike? Training wheels is NOT the answer. They really don’t help. What does this have to do with the Tour de France? Well, don’t you think at some point these cyclists had to learn to ride a bike?

Why do training wheels not help? They don’t teach you the most important thing about riding a bike: if you are falling to the left, turn to the left. If training wheels don’t help, then what works? I recommend a push bike. With a push bike, a child just uses his/her feet to propel the bike forward. Here is an example.

Now’s Your Chance to Snag Your Very Own Harrier Hover Plane

This 1976 Hawker Siddeley Harrier GR3 jump jet is going up for auction this month. Silverstone Auctions

If you’ve always wanted to own a hover plane but aren’t actually in the military, here’s your chance. A Harrier jump jet goes up for auction later this month, and it won’t take much to get it flying again.

The Harrier, developed by the British in the 1960s and later embraced by Marine Corps, is best known for its ability to hover like a helicopter. The jet’s engine pumps air through four nozzles, which rotate to propel the plane forward or straight up. That allows for very short takeoffs and vertical landings, so the plane doesn’t need a long runway to operate. It’s among the coolest, most ingenious aircraft ever designed. It’s also a bitch to fly.

The plane in question, serial number XZ132, was built in 1976 by Hawker Siddeley for the British Royal Air Force. It served in Germany during the Cold War and flew in Belize and the Falkland Islands. After 15 years, it was sent to the RAF College Cranwell, where it was used for training purposes. If that has you worried the plane was used and abused by n00bs, rest assured the plane experienced “nothing horrendous,” according to Silverstone Auctions. It was, they insist, “a mere training aid for trainee engineering officers to be taught about aerodynamics, flying controls, and documentation” and last flown in August 1990.

If you’re interested in buying the jet, you should know early Harriers were notoriously difficult to control and had an egregious safety record. So if you decide to make this plane fly again, check your life insurance before suiting up.

The current (unnamed) owner acquired Harrier XZ132 in November and has spent six months making it nearly as good as new. It wasn’t much trouble, since the jet was kept in a heated building. The paint hasn’t corroded or faded. The mechanical components “appear to be in tip top condition” and the sale includes more than 150 pounds of paperwork and documentation. It even has the original Mk9A Martin Baker ejection seat. Unfortunately for the action hero in all of us, it’s inert.

The old Harrier is, however, missing a few things:

• Weapons systems and armaments. This almost certainly is for your own good. You really don’t need to be messing around with weapons and armaments, especially the rockets and BL755 cluster bombs the Harrier is made to carry.


• A mounted engine. The Rolls Royce Pegasus Mk103 engine comes on a wheeled stand.


• A few minor internal components, including the water tank, some fuel pipes, and some avionics.

The jet is crossing the block at the Silverstone Classic Sale in England on July 26. Silverstone won’t speculate on what it might go for, saying “market value for an aircraft of this pedigree is nearly impossible to gauge.” There’s no reserve, so if there aren’t a lot of bidders, you might get a really good price. Silverstone suggests the Harrier would be great “as a museum exhibit, gate guardian or centerpiece to a private collection.” Obviously it would be more fun to put in the extra work and make it fly again. If you dare.

If that’s too much for you, check out the Harrier Jump Jet pilot dummy that’s also going on auction, complete with night vision compatible helmet, oxygen mask, flying boots, leather gloves, and everything you need to connect to an ejector seat. All for a relatively affordable £1,000 to £1,500 ($1,710 to $2,570).

Tech Titans Take Their Fight to the Mean Streets of Same-Day Delivery

Amazon's reinvention of the warehouse is a logistical advance on par with the shipping container or the bar code. Gluekit; Alamy; Middle Truck: Corbis; Right Truck: Getty Images

Convenience stores are a trillion-dollar industry worldwide, despite the fact that they're not actually very convenient. In principle, at least, 7-Elevens have been optimally spread throughout your region and optimally stocked with items you want in a pinch. But with their limited footprints, they can't stock nearly enough items to satisfy everyone. And given that you probably need to drive there anyway, you might as well travel the extra 10 minutes to the supermarket or big-box retailer that has what you really want.

True convenience shopping is on its way, though, and we won't need to drive at all to enjoy it. Instead, the store will come to us: Within five years, the majority of items we crave on short notice—ice cream, books, umbrellas, lightbulbs—will be available for delivery the same day. This will be enabled, in part, by better interfaces (speech-recognition apps for ordering items by voice alone, sensors in fridges to guess what we'll need before we even realize it) and by better data analysis. But the most crucial change will be in the streets: fleets of delivery vehicles that strategically traverse the roads of cities and suburbs, stuffed with the items that retailers' algorithms will predict we want.

Of course, the 7-Elevens of the world probably won't be the companies to achieve this. Big tech firms—most of which built their multibillion-dollar businesses on moving weightless bits around—are now racing to make this sci-fi vision a reality. Just as getting those bits the “last mile” into homes and businesses was the defining technology challenge of the '00s, so getting actual stuff the last mile will be the tech challenge of this decade. In short, logistics—the tech industry's boring sideshow—has emerged as its central drama.

THESE TRUCKS COULD EVEN CARRY PRODUCTS THAT YOU HAVEN'T ORDERED BUT THAT AMAZON'S ALGORITHMS PREDICT YOU PROBABLY WILL.

It's hardly a surprise that Amazon is the farthest along in building this future. Back in the early days of the web, when everyone else was trying to figure out how to make the Internet work better in and for itself, Jeff Bezos was already trying to make it work for the world of physical retail. To move stuff at the speed of the Internet—that is, as fast as possible—the Amazon founder realized he needed to think algorithmically about order fulfillment. Amazon reengineered its distribution centers according to rules that make computer sense rather than common sense. Inventory is stored not by category but simply by whether a shelf has room. And multiples of the same item aren't stockpiled together; instead they're dispersed throughout a warehouse, to minimize the distance workers (or robots) have to travel through these monumental million-square-foot facilities. All told, Amazon's reinvention of the warehouse is arguably a logistical advance on par with the shipping container or the bar code.

But the ambition of what Amazon has done inside its warehouses is nothing compared to what it's now trying to do beyond those walls. On the streets of several US cities, lime-green trucks emblazoned with the AmazonFresh logo deliver groceries the same day they're ordered. And food is just a wedge product that, if it catches on for Amazon, could turn the company's trucks into roving nodes on a logistics network that's able to deliver nearly anything.

Over the past several years, Amazon has foregone profits to fund massive new “fulfillment centers” within range of the largest metro areas in the US. Once reluctant to set up operations in states such as California that would force it to collect sales tax, Amazon is now betting that proximity to its customers will lure them into ordering more, enticed by the sheer speed with which their every shopping whim can be fulfilled. And there's every reason to think the gambit will work. Unlike the first generation of delivery debacles (such as Kozmo and Webvan), Amazon has spent 20 years perfecting warehouse management and achieving the economies of scale required to make same-day delivery work. And while the retail world's other logistical powerhouse, Walmart, could become a viable competitor, only Amazon among all its rivals has always operated as a technology company first.

For Amazon, the endgame is nothing less than ubiquity: a fleet of trucks to serve as a 21st-century version of the milkman and the mail carrier combined. Amazon trucks could become a daily presence on neighborhood streets, delivering nearly anything the online retailer sells—which is almost everything. These trucks could even wind up carrying small aerial delivery drones—of the sort that Bezos touted, to much incredulity, on 60 Minutes last year—as well as products that you haven't ordered but that Amazon's “anticipatory package shipping” algorithms (a concept the company patented in December) predict you probably will.

LOGISTICS HAS ITS LIMITS: SAME-DAY DELIVERY MIGHT NEVER BE POSSIBLE EVERYWHERE, AND THE CARBON FOOTPRINT CAN'T BE SIMPLY WISHED AWAY.

All of the technologies to make that future possible already exist; it's just a matter of putting the pieces together. And Amazon is hardly the only company with the potential to pull it off. Think about Google, whose acquisitions and big experimental projects over the past year—robots, drones, self-driving cars, same-day delivery shopping—seem to be aimed at building a physical platform for its machine intelligence expertise. Meanwhile, Google's main online business, search, has focused on using artificial intelligence to anticipate users' information needs before they even ask. If Google could combine those two strengths into a kind of Google Now for stuff, it would have most of the necessary tools for taking on Amazon in the streets. And in the process, it would bring customers back to Google to search for products its advertisers sell, rather than heading straight to Amazon to buy them.

Yes, there is a limit to what high tech logistics can accomplish. Same-day delivery might never be possible everywhere, for example, and the carbon footprint of the system can't be wished away. But the improvement that such a system will represent over our convenience-store present will still be remarkable. Amazon is promising more than 500,000 different items available for same-day delivery through its current experimental program, while the biggest big-box superstores carry about 150,000. True, this is still just a small fraction of the hundreds of millions of items Amazon sells—but as the company's infrastructure expands, and its algorithms get better at shuffling merchandise according to patterns of demand, the portion of items available will radically expand as well. Both the beauty and challenge of same-day economics for Amazon is that the more the system gets used, the more efficient—and therefore affordable—it becomes.

Over time, the network of trucks can become a kind of ambient consumer layer, rendering brick-and-mortar retail ever more superfluous. In the process, as with the spread of broadband, these new delivery platforms will create multibillion-dollar businesses not just for the companies that control the platforms but also for companies that sell through them, hiring those ubiquitous trucks to ferry their own products, services, things we haven't even thought of, right to your doorstep. For that future to arrive, we just need to solve the new last-mile problem—and a solution may be right around the corner.

Uber’s Brilliant Strategy to Make Itself Too Big to Ban

Uber

The question of how Uber would spend its billion-dollar investment was never really much of a riddle. More rides in more places has always been the plan.

But with its ten-figure cushion, the San Francisco-based ride-hailing startup can be more cunning about how it tries to get huge. Uber wants to grow as quickly it can, and right now, it’s chasing that goal by undercutting the competition on price—even if it loses money in the process. This isn’t a novel approach among tech startups, for which profits aren’t valued nearly as much as popularity. But for Uber, playing in the new realm of the so-called sharing economy, the stakes are higher, since so many entrenched interests are trying to regulate it out of existence. With not just success but survival on the line, Uber has even more incentive to expand as rapidly as possible. If it gets big enough quickly enough, the political price could become too high for any elected official who tries to pull Uber to the curb.

Yesterday, Uber announced it was lowering UberX fares by 20 percent in New York City, claiming the cuts would make its cheapest service cheaper than a regular yellow taxi. That follows a 25 percent decrease in the San Francisco Bay Area announced last week, and a similar drop in Los Angeles UberX prices revealed earlier last month. The company says UberX drivers in California (though apparently not in New York) will still get paid their standard 80 percent portion of what the fare would have been before the discount. As Forbes‘ Ellen Huet points out, the arrangement means a San Francisco ride that once cost $15 will now cost passengers $11.25, but the driver still gets paid $12.

Uber says its new, lower UberX fares are cheaper than New York yellow cabs. Image: Uber

In that scenario, Uber loses money twice-over. First, it loses the 75 cents extra it pays to make up the difference to the driver. Second, its taking exactly zero commission. In effect, the company is paying for passengers to ride. (Apparently, drivers in New York aren’t getting the same sweet deal—Uber says they’ll make up the difference with more rides.) Loss leaders may be nothing new, but it’s a little different when you’re losing money on the main thing you sell. To be fair, Uber’s original black car business could make up some of the difference. But the company isn’t likely too worried either way. Its strategy here is much less traditional taxi and much more typical dotcom: grow the user base as quickly as possible and worry about making money later.

Like Uber, Like Amazon

Consider Uber’s kinship with Amazon. The comparison isn’t obvious at first, since Uber doesn’t sell goods, just a service. But their stories are similar. A startup led by a brash, charismatic CEO catches a creaky old industry unaware. It grows quickly, and its popularity explodes as its brand becomes nearly synonymous with the disruptive service it’s offering. Amazon grew—and is still growing— because it’s not afraid to lose money. Low prices and free shipping deals eat away at profitability, but they also keep customers coming back. Uber CEO Travis Kalanick has expressed admiration for Amazon founder Jeff Bezos, who is also an investor in the transportation company. And now Kalanick appears to be taking cues from the Amazon template.

Whether this strategy is really sustainable for Amazon after twenty years of existence is a question endlessly debated among shareholders. But for its current stage of development, the approach holds little but upside for Uber. Rapid expansion helps Uber both locally and globally. In cities, underselling traditional taxis gets more riders in UberX cars, striking a blow against yellow-cab competition. Popularity in one city creates covetousness in others. Demand spreads, and Uber follows (it now operates in about 140 cities in 40 countries around the world).

To keep spreading quickly, Uber needs to aggressively recruit new drivers, which could be difficult if price cuts also meant cuts to driver pay. Fiddling with prices has led to driver unrest, and the company’s assurances that drivers can make more than $90,000 per year in New York have been met with skepticism. On Twitter, Kalanick argued that lower prices meant drivers could make more, because increased demand would lead to more rides booked per hour. That claim is a lot easier to make if Uber is in fact subsidizing driver pay at a loss.

Don’t Take My Uber Away

But keeping drivers behind the wheel is ultimately an operational issue that Uber so far has handled adeptly. Much more dangerous to its future prospects are ongoing threats from regulators and lawmakers to shut Uber down, or at least severely curtail its freedom to operate. Ever since receiving (and ignoring) a cease-and-desist demand from transit regulators in San Francisco, Uber’s first city, in 2010, the company has followed the same playbook when faced with attempts to shut it down: keep the wheels on the road. The strategy has worked so far in San Francisco, though various state-level attempts to rein in Uber are still in play. Uber has survived many other efforts to restrict its service, though these victories are often incremental, and seldom come without extensive time and effort.

The uncertainty that comes with attempting to regulate Uber out of existence can’t be too comforting to investors, though it also didn’t deter more than $1.2 billion in funding so far. Some of that money is going toward hiring high-powered lobbyists to push back. But more powerful political leverage comes in the form of popularity. “The more they sort of popularize themselves, the stronger their argument becomes” against crackdowns, New York University Stern School of Business professor Arun Sundararajan told Businessweek.

That strength, however, doesn’t have as much to do with the quality of the argument as it does with the quantity of people who support it. The more riders Uber can get in its cars and accustomed to having its push-button convenience as an option, the less incentive politicians have to stay on Uber’s case. By drastically lowering its prices, Uber is doing more than increasing its customer base. It’s cultivating constituents — the people who will complain when someone in power tries to take away their Uber. If Uber can survive its many political battles, it stands to become a huge, and hugely valuable, global enterprise. For investors, that’s a billion dollars well spent.

Flash Forward

Photo: Josh Valcarcel/WIRED

You’ve been busy snapping photos with your digital camera all day. Now you want to get those pics transferred to your tablet or laptop. The other devices don’t have a compatible SD card slot. What to do?

Toshiba’s FlashAir II offers a handy solution, embedding a miniature Wi-Fi access point into a standard SD card. Just like that, you can access photos on the card from up to seven other devices, connecting directly via Wi-Fi to the card’s access point.

If this sounds familiar, you’re probably thinking of the venerable Eye-Fi line of products, which combine an SD card and a wireless radio, giving your camera instant wireless capabilities. But Eye-Fi and FlashAir work quite differently. With Eye-Fi, your camera connects to an existing wireless network, which it uses to upload photos to the cloud or another PC on the LAN. FlashAir doesn’t require an existing network—in fact, it can’t connect to an existing network. Rather, FlashAir is its own wireless LAN, and you configure your other devices to connect to it.

For casual users, this is the going to be the cumbersome deal-breaker of the process. If you’re already connected to one network, having to tell your phone or tablet to disconnect from it and then reconnect to a temporary LAN set up by the FlashAir II, is messy and time-consuming. If your camera happens to get turned off at any time along the way, you must start all over. (Tip: Disable the “auto off” feature on your camera to get things working much more smoothly.)

Once you’re connected you have to use an app (iOS or Android) to access the photos on the device. You can get to the photos via a web browser on a PC or Mac (or on any mobile device, really), but there’s no native file access provided, so don’t go hunting for a network drive in Windows Explorer where you can quickly scan through all the photos.

Within the app, your options are fairly limited. You can save photos to local storage or send them via standard email or social networks direct from the app, and that’s about it. Simplicity is fine, but the app is on the buggy side, too. I spent way too much time dealing with a “start” button that refused to be pressed before eventually stumbling upon a workaround that got me into a thumbnail view of my pictures.

At a street price of $36 for a 16GB card, the FlashAir II has a substantial premium over a standard SD card, which costs about 10 bucks. On the other hand, the FlashAir II is substantially cheaper than a comparable Eye-Fi card ($65). So if adding wireless features to a camera is important to you, and you don’t mind getting your hands a bit dirty, it’s a solution that might make sense.

On Motorcycles, the Real Fun Begins When the Pavement Ends

Jake Stangel

This is a disaster. Just a few hours into a three-day motorcycle ride through the unpaved wilds of Washington's Cascade Mountains, I've already dropped the bike several times. I'm beat up; my hair is matted with sweat. My wool base layers are wet-stuck to my skin. My confidence is brittle as burnt paper.

On a motorcycle, confidence is a small target that you need to hit squarely. Get too cocky, overcook a turn, and you're a flower-covered cross on the side of a highway. But if you ride timid, your lack of speed could put you at risk of wiping out; the faster the wheels are turning under you, the more gyroscopic stability they provide.

THE ROAD GETS BAD, BUT IN THE BEST WAY— MUDDY, NARROW, RUTS YOU COULD USE AS A KOI POND.

I'm doing that second thing: crawling too slowly over a rutted and rock-pocked moonscape. I'm supposed to be testing my own ability to step away from the civilized world, trying out the best equipment for eating, sleeping, and riding under the unobstructed sky. Instead, I'm spending way too much time looking up at the sky from underneath nearly 500 pounds of Kawasaki.

The problem, I'm guessing, is that I've strapped about 50 pounds of clothes and camping gear to the back of the bike, about a mile above my center of gravity. I'm riding the 2014 edition of the KLR650, a venerable model dating back to 1987. The KLR is the french fry of motorcycles: You can find one (and someone to fix it) anywhere from California to the Central African Republic. Its terrain-eating suspension and centrally mounted engine are designed to deliver the balance and clearance you need to go miles beyond the end of your comfort zone.

Unfortunately, the KLR's seat is 35 inches off the ground; my jeans have a 30-inch inseam. I don't so much sit on the bike as perch atop it like the kid in The NeverEnding Story riding the luck dragon. Only, the KLR doesn't kneel down gently to let me off. It just kind of tips over.

Jake Stangel

The first time I dumped the bike, it pinned my leg to the ground; if not for a pair of armored Alpinestars boots, my trip probably would have ended right there with a broken foot. It's not like I'm some first-timer. I started riding in college and have experience everywhere from the race track to rush hour. But I don't have much history off-road; riding on dirt is completely different from pavement. And because the bike is so tall, I can't get my feet on the ground to stop it if it starts tipping. This thought is in my head as the KLR slips out from under me again around a corner atop a steep slope of grass-covered rock. The only thing stopping me from stuffing a grenade under the bike and walking to the nearest bar is my lack of a grenade.

But if the problem is my center of gravity, I can do something about it. Choosing to think of it as an improvisation instead of a defeat, I unload the bags, set up a base camp, and saddle up again to explore the vicinity.

Free of its load, the KLR is still a beast, but I can handle it better. Now, if the bike starts to shift, I can recover from the wobble. Riding has begun to look feasible, but I'm still making mistakes. I'm shattered from the morning's dose of catastrophe, and I just want the day to be over. I point the KLR toward the campsite.

Jake Stangel

My tent, in contrast to the bike, is cooperative. Also it has a garage. Made by a mom-and-pop shop called Redverz, it sleeps two (technically three, but don't even) and has a ride-in vestibule to keep your bike sheltered from the elements. Sometimes, like when you're ducking a sandstorm while riding in the Paris-Dakar Rally, shelter for your gear as well as yourself can be important. On a clear weekend in the Washington mountains it is, I'll admit, a little overkillish.

The tent is great, but its instructions are laughable. One of the steps is basically “Put the poles in their corresponding sleeves,” but the single laminated page gives no indication of what corresponds to what. (I realize later that there is some half-assed color coding at play.) The tent also comes with stakes, so I put them in the ground, even though the instruction sheet doesn't mention them. Half an hour later I've got shelter. I wheel the bike in, start a fire (outside), change into sweatpants, rock back in my camp chair, and open a beer.

The cold of the morning on my nose—about the only thing peeking out of my down mummy bag—wakes me. It's still dark out, so I flick on my little Black Diamond LED lamp and dress without leaving the bag. (Put the next day's clothes in your sleeping bag at night and they're warm when you get up in the morning.)

Between my wool base layers and the insulated Rev'it riding getup, I'm cozy. Leaving my gear at the campsite, I get an early start and ride up a logging road that's supposed to have some challenging terrain. It gets bad, in the best way: muddy, barely 6 feet wide, ruts so deep you could use one as a koi pond.

The Redverz Expedition tent is so motorcycle-centric that it has a built-in garage to shelter your bike and gear. Jake Stangel

I ride it a few times, forcing myself to be light on the bars, to let the front tire follow the terrain, to steer with my knees rather than my arms. Speeding up, I aim for a sharp crest I previously avoided. I roll on the throttle to transfer weight to the rear wheel and hit hard. I clear it, only to realize that there's a bigger rock on the other side. Gravity and momentum pitching in, I hit that one even faster, and I feel the bike leave the ground. I touch down, tip to the right, throw my weight left, ride it out, and then skid my rear tire to a stop. This is what you call a turning point.

By the third morning, the bike feels dialed in. The air is cold on the patch of neck my suit and helmet leave exposed. I ride paved roads from mountain to mountain, and the bike is happy on the blacktop: dancing through the tar-snakes on the farm-lined back roads. Off-road, headed up a rock-and-mud slope, I push maybe a little too hard and almost lose it a few times. Almost.

SAR11, oceans' most abundant organism, has ability to create methane

The oxygen-rich surface waters of the world's major oceans are supersaturated with methane -- a powerful greenhouse gas that is roughly 20 times more potent than carbon dioxide -- yet little is known about the source of this methane.

Now a new study by researchers at Oregon State University demonstrates the ability of some strains of the oceans' most abundant organism -- SAR11 -- to generate methane as a byproduct of breaking down a compound for its phosphorus.

Results of the study are being published this week in Nature Communications. It was funded by the National Science Foundation and the Gordon and Betty Moore Foundation.

"Anaerobic methane biogenesis was the only process known to produce methane in the oceans and that requires environments with very low levels of oxygen," said Angelicque "Angel" White, a researcher in OSU's College of Earth, Ocean, and Atmospheric Sciences and co-author on the study. "In the vast central gyres of the Pacific and Atlantic oceans, the surface waters have lots of oxygen from mixing with the atmosphere -- and yet they also have lots of methane, hence the term 'marine methane paradox.'

"We've now learned that certain strains of SAR11, when starved for phosphorus, turn to a compound known as methylphosphonic acid," White added. "The organisms produce enzymes that can break this compound apart, freeing up phosphorus that can be used for growth -- and leaving methane behind."

The discovery is an important piece of the puzzle in understanding Earth's methane cycle, scientists say. It builds on a series of studies conducted by researchers from several institutions around the world over the past several years.

Previous research has shown that adding methylphosphonic acid, or MPn, to seawater produces methane, though no one knew exactly how. Then a laboratory study led by David Karl of the University of Hawaii and OSU's White found that an organism called Trichodesmium could break down MPn and thus it could be a potential source of phosphorus, which is a critical mineral essential to every living organism.

However, Trichodesmium are rare in the marine environment and unlikely to be the only source for vast methane deposits in the surface waters.

So White turned to Steve Giovannoni, a distinguished professor of microbiology at OSU, who not only maintains the world's largest bank of SAR11 strains, but who also discovered and identified SAR11 in 1990. In a series of experiments, White, Giovannoni, and graduate students Paul Carini and Emily Campbell tested the capacity of different SAR11 strains to consume MPn and cleave off methane.

"We found that some did produce a methane byproduct, and some didn't," White said. "Just as some humans have a different capacity for breaking down compounds for nutrition than others, so do these organisms. The bottom line is that this shows phosphate-starved bacterioplankton have the capability of producing methane and doing so in oxygen-rich waters."

SAR11 is the smallest free-living cell known and also has the smallest genome, or genetic structure, of any independent cell. Yet it dominates life in the oceans, thrives where most other cells would die, and plays a huge role in the cycling of carbon on Earth.

These bacteria are so dominant that their combined weight exceeds that of all the fish in the world's oceans, scientists say. In a marine environment that's low in nutrients and other resources, they are able to survive and replicate in extraordinary numbers -- a milliliter of seawater, for instance, might contain 500,000 of these cells.

"The ocean is a competitive environment and these bacteria apparently won the race," said Giovannoni, a professor in OSU's College of Science. "Our analysis of the SAR11 genome indicates that they became the dominant life form in the oceans largely by being the simplest."

"Their ability to cleave off methane is an interesting finding because it provides a partial explanation for why methane is so abundant in the high-oxygen waters of the mid-ocean regions," Giovannoni added. "Just how much they contribute to the methane budget still needs to be determined."

Since the discovery of SAR11, scientists have been interested in their role in Earth's carbon budget. Now their possible implication in methane creation gives the study of these bacteria new importance.