If he’s kept up with the science section, then presumably the past four decades have been a roller coaster for poor Alvy, with astronomers and astrophysicists speculating that the universe would eventually start contracting again (it figures he could never permanently escape Brooklyn), and then deciding that it would go on expanding forever, in fact, that it’s expanding faster and faster. Also, the universe is flat, at least the part of it we can see, which isn’t much. As Richard Panek explains in his lively new account of 20th-century (plus a little 21st-century) cosmology, “The 4 Percent Universe: Dark Matter, Dark Energy and the Race to Discover the Rest of Reality,” 85 percent of everything consists of stuff that’s undetectable to the human senses and profoundly mysterious. And we’re not talking about Staten Island.

“The 4 Percent Universe” is largely an account of the uneasy alliance between astronomers and particle physicists in the quest to grasp what the astronomer Alan Sandage called “the only two numbers to measure in cosmology,” that is, how fast the universe is expanding right now and at what rate that expansion is changing over time — otherwise known as the deceleration parameter. These two figures can tell you how old the universe is and when it will come to an end. But figuring out what those numbers are and above all why they are what they are has been no easy task.

Impetus from the explosion known as the Big Bang (when the universe went from being one very tiny, unimaginably dense particle to, well, everything) seemed to be what was making the universe expand. However, gravity — the attraction between masses — should be exerting a countervailing influence to slow down the force of the Big Bang and eventually cause the universe to suck itself back in. This changeover, however, doesn’t seem to be on the menu, as astronomers discovered during the past 100 or so years, as they developed more and more sophisticated and sensitive instruments with which to make observations. (When the 20th century opened, for example, we were wondering if ours was the only galaxy. Now we’ve identified hundreds of thousands of others.)

Astronomers like Vera Rubin, studying the behavior of galaxies and galaxy clusters (they tend to clump up), noticed that they behaved weirdly, at least as long as you assumed that the only stuff in them was the stuff you could see. It’s as if your breakfast of cinnamon toast arrived at the table looking like nothing more than a spiral of cinnamon floating over the plate. The bread holding it in formation might not be visible, but from the configuration of that cinnamon, you could deduce it was there.

The existence of invisible “dark matter” was first inferred by the Swiss astronomer Fritz Zwicky in the 1930s, but inferring is not the same as demonstrating, and the quest to actually measure a particle of dark matter is ongoing. (“The 4 Percent Universe” follows the story right up to the present day.) Much of Panek’s book is taken up with describing the pitched rivalry between two teams working on methods to determine Sandage’s famous numbers. One, working out of the Lawrence Berkeley National Laboratory and headed by Saul Perlmutter, was oriented more toward physics, while the other, more astronomically minded team was a looser coalition of scientists who chose the Australian Brian Schmidt as their leader.

According to Panek, physicists and astronomers have pretty different working styles, and it’s hard not to root for Schmidt’s team (the High-Z SN Search program), as it bucks the hierarchical customs by which “big gun” senior scientists take credit for the work done by junior team members. Nevertheless, if Perlmutter’s team, the Supernova Cosmology Project (SCP), was less democratic, it still got important results. Both groups independently arrived at the conclusion that the expansion of the universe is accelerating (further evidence for the existence of both dark matter and dark energy), and the race was neck and neck all the way. (Essentially, it was a tie, but you wouldn’t want to say so to a member of either team in a bar.)

They did this by observing supernovae, high-energy stellar explosions that, unlike most other cosmic events, take place over a period of time short enough that mere human beings can watch them unfold. Over the course of the century, astronomers have developed more and more exquisite ways to spot and analyze supernovae in order to determine how far away they are (that is, were — since what we’re really seeing is the light produced by events that happened billions of years ago) and how fast they’re moving.

These efforts have been complicated by the discovery that there are several kinds of supernovae, and by the meddling of factors like cosmic dust. For example, the redness of the light emitted by a supernova can tell you how fast it’s moving away from you (this is a distortion of light waves like the Doppler effect that you hear in sound waves as a siren drives past), but it could look redder than it really is if there’s red dust between the telescope and the supernova.

The backbone narrative of “The 4 Percent Universe” is the story of how High-Z and SCP arrived at their discovery, with the astronomers talking trash about the physicists (and vice versa), duels over who gets time on the Hubble Space Telescope and more than a few dust-ups in the scientific press. The book is as much about how the science got done as about the science itself, and sometimes the false leads and wild goose chases can be confusing to the astronomical novice. Nevertheless, Panek, who has written early accounts of these matters for the New York Times, is a wondrously clear explicator of some thorny concepts, and by the end even cosmological dilettantes will chuckle knowingly upon learning of an e-mail Schmidt sent to one of his team in 1998, that read, “Well Hello Lambda!”

So yes, Alvy, the universe is still expanding, even Brooklyn, and it may indeed break apart someday. But until then, there is still the thrilling mystery of dark matter and dark energy to plumb, so in the meantime, for God’s sake: Do your homework.

Fox News has an excellent explanation of the Perseids for laymen, while the Christian Science Monitor covers the pre-shower fireball (actually a tiny meteor) spotted over Alabama this week. NASA scientists compare meteor showers to bugs splatting on your car windshield, and MSNBC has tips on how to enjoy the display effectively. Check out this brief night-vision footage of 2007′s Perseids:

In fact, it’s burning itself off with such intensity that it shines at nearly 10 million times the luminosity of the sun.

“Unlike humans, these stars are born heavy and lose weight as they age,” said Crowther, an astrophysicist at the University of Sheffield in northern England. “R136a1 is already middle-aged and has undergone an intense weight loss program.”

Crowther said the giant was identified at the center of a star cluster in the Tarantula Nebula, a sprawling cloud of gas and dust in the Large Magellanic Cloud, a galaxy about 165,000 light-years away from our own Milky Way.

The star was the most massive of several giants identified by Crowther and his team in an article in the Monthly Notices of the Royal Astronomical Society.

While other stars can be larger, notably the swollen crimson-colored ones known as red giants, they weigh far less.

Still, the mass of R136a1 and its ilk means they’re tens of times bigger than the Earth’s sun and they’re brighter and hotter, too.

Surface temperatures can surpass 40,000 degrees Celsius (72,000 degrees Fahrenheit), seven times hotter than the sun. They’re also several million times brighter, because the greedy giants tear through their energy reserves far faster than their smaller counterparts.

That also means that massive stars live fast and die young, quickly shedding huge amounts of material and burning themselves out in what are thought to be spectacular explosions.

“The biggest live only 3 million years,” Crowther said. “In astronomy that’s a very short time.”

Small lifespans are one of several reasons why these obese stars are so hard to find. Another is that they’re extremely rare, forming only in the densest star clusters.

Astronomers also have a limited range in which to look for them. In clusters that are too far away, it isn’t always possible to tell if a telescope has picked up on one heavyweight star or two smaller ones in close proximity.

In this case, Crowther’s team re-examined previously known stars to see if they could find an accurate measurement of their weight. The team reviewed archival data from the Hubble Space Telescope and gathered new readings from the European Southern Observatory’s Very Large Telescope at Paranal in Chile.

Scientists who weren’t involved in the find said the results were impressive, although they cautioned it was still possible, although unlikely, that scientists had confused two very close stars for a bigger, single one.

“What they’re characterizing as a single massive star could in fact be a binary system too close to be resolved,” said Mark Krumholz, an astronomer at the University of California, Santa Cruz.

Both he and Phillip Massey, an astronomer with the Lowell Observatory in Arizona, also cautioned that the star’s weight had been inferred using scientific models and that those were subject to change.

But both scientists said the authors had made a strong case, arguing that the solar material being thrown off from feuding stars in a binary system would produce much more powerful X-rays than have been detected.

Crowther acknowledged that R136a1 could have a partner, but he said it was likely to be a much smaller star, meaning that the star’s its birth weight was still considerable — perhaps 300 solar masses instead of 320.

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Online:

European Southern Observatory: http://www.eso.org/

“Quantum” orbits around the celebrated fifth Solvay conference, held in Brussels in 1927, a gathering of the greatest minds in 20th-century physics. It was at Solvay that Werner Heisenberg and Max Born presented the theory of quantum mechanics they had been working on for several years under the informal leadership of Niels Bohr. Their understanding of subatomic reality came to be called “the Copenhagen interpretation” (after the location of the Institute of Theoretical Physics, which Bohr ran), and its champions proclaimed it a “closed theory, whose fundamental physical and mathematical assumptions are no longer susceptible of any modification.”

Albert Einstein, also present, disagreed, and the following decades saw a series of intense, if friendly, arguments between Einstein and Bohr — who, as Kumar notes, had a diagram of one of Einstein’s most famous thought experiments up on his office chalkboard on the day he died in 1962. That experiment, which involved the imaginary weighing of a “box filled with light” before and after a single photon is allowed to escape, is an example of the surreal mental territory that “Quantum” explores. Reading it is a bit like lifting the hood of your mind and moving the working parts around; it’s challenging and trippy — as only the Dr. Seuss realm of the quantum can be.

Kumar, a science writer in Britain (where this book was first published, two years ago), makes a point of playing up the collaborative aspects of the evolution of quantum theory, as well as the conflicts; the two can’t really be separated. He begins with Max Planck’s reluctant invention of the “quanta” — an indivisible unit of energy — in 1900. He insisted it was a mere theoretical, most likely temporary “trick,” designed to get certain formulas to work properly. When, five years later, Einstein, during a period of astounding scientific creativity that included his famous paper on special relativity, suggested that light might be made up of “particle-like quanta” (later called photons), he thought of it as his most daring break with the classical physics of Newton. Light, like other forms of energy, had long been believed to flow in continuous waves, not in tiny chunks.

It was in the 1920s that quantum mechanics as we know it was born, with physicists like Heisenberg, Wolfgang Pauli, Erwin Schrödinger and Paul Dirac scrutinizing each other’s proposals, seizing upon weak spots to investigate, discovering little-known laboratory data or mathematical methods that might provide a solution and writing important papers only to find that some theoretician in the hinterlands had gotten there first. It was, as Kumar puts it, “a golden age … unparalleled since the scientific revolution in the 17th century led by Galileo and Newton.” The dollops he offers of these scientists’ personal lives and youths emphasize the importance of teachers, mentors and patrons, as well as those rare individuals, like Bohr, whose tact and generosity aided in keeping things collegial. (By contrast, 17th century science was impeded by the paranoia and secrecy of Newton.)

That it can be hard to wrap your brain around the principles of the subatomic world is a given. It’s a strange kingdom, full of things that don’t exist or exist in two opposite conditions at once until somebody looks at them, particles that influence each other instantaneously despite being separated by lightyears and electrons that move from one place to another without traveling through the space in between. Books on the subject rely on good metaphors, clearly explained, and Kumar delivers them, but “Quantum” is not for the complete novice or those timid souls who quail at the sight of an equation. (I can’t claim to understand the few equations Kumar includes myself, but they don’t scare me away, and I found this book is perfectly intelligible even though I can’t do the math.)

Much of the debate between Einstein and Bohr revolved around Einstein’s intuitive rejection of the implication of the Copenhagen interpretation — which is that objective reality, independent of any observer, doesn’t really exist. Bohr, by contrast (and sounding a lot like Wittgenstein), insisted that physics isn’t concerned with what is but solely with what we can say about it. Not only were these two geniuses battling over where to draw the line between the familiar, cause-and-effect world of classical Newtonian physics and the quantum Wonderland, they were sketching, erasing and resketching the boundary between science and philosophy, debating the nature of reality itself.

Einstein was for many years regarded as a stubborn, even senile holdout against the quantum gospel, but Kumar finds that view simplistic. “Quantum” concludes by surveying developments since the deaths of Bohr and Einstein, such as Bell’s Theorem and the many worlds interpretation, some of which point to critical problems that the Copenhagen interpretation left unresolved. (One is how the phenomenon of the universe came to be in the first place if there was no one to observe the Big Bang.) All of this, the author maintains, has led to “a reconsideration of the long-standing verdict against Einstein in his long-running debate with Bohr.” Instead, he paints Einstein as a partisan of that most precious of scientific tools: the question. That’s why he ends with one of the physicist’s favorite quotations, from the German philosopher Gotthold Lessing: “The aspiration to truth is more precious than its assured possession.”

“Imagine a plane is sitting on a massive conveyor belt,” poses Pogue’s Dec. 11 Times blog, “as wide and as long as a runway. The conveyer belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off?”

When I last checked, more than 860 people had posted their opinions, split about 50/50 between those who say the airplane will fly and those who insist it can’t. If you look carefully you can locate my own contribution, flatly declaring that no, absolutely not, the aircraft will not get off the ground. “If this is truly ‘ripping around the Internet,’” I snarked, “then heaven help us. The plane will not fly. Of course it won’t fly.”

And why should it? How can it fly if it’s not moving? For an aircraft to get and stay aloft, it needs lift; it needs air passing above and below its wings. And for that it needs to move. For a cursory lesson on how this works, simply shove your arm out the window of a speeding car. Shape your hand into an approximation of a wing, angle it slightly into the oncoming wind, and voilà, it’s flying.

Now, imagine you are in that same car, on a treadmill. The car’s wheels are spinning — be it at 60 mph or 600 mph — but when you put your hand out the window, does it rise up? Of course not. Your hand won’t fly, and the plane won’t fly either for exactly the same reason: because for all its efforts, the vehicle isn’t moving. You have zero relative speed and zero lift.

This seemed so obvious that it needed a caveat: “On the other hand, if you were able to generate a tremendous enough amount of thrust,” I noted in a follow-up post, “and redirect the vector of that thrust downward, you could, conceivably, lift the plane off like a rocket. Heck, you can make anything ‘fly’ if you stick enough power under it. But that isn’t fair to the spirit of the premise.”

Except, wait a minute, what is the premise?

Go back and read it. “Imagine a plane is sitting on a massive conveyor belt,” it says, “as wide and as long as a runway.” I’d glanced right over those key words, “as long as a runway.” I was so caught up in the image of a motionless plane on a regular old treadmill — like the kind you might see at the gym — that I missed the whole question. Looking back, that does seem a dull and senseless riddle: Can a plane fly if it can’t move? Obviously not. There has to be more to it.

And there is. At heart, this has nothing to do with the principles of lift but, rather, with those of friction and acceleration. The gist of the question is better understood as follows: Will an airplane, under its own power, remain motionless on a 10,000-foot-long treadmill, or will it roll forward? Will it accelerate and fly?

Turns out the answer is yes. A distinctly theoretical yes, for reasons we’ll get to shortly, but for all intents and purposes of the puzzle, that’s yes enough.

A car won’t accelerate on a treadmill; the belt will always match the rotation of the tires. You will not accelerate on a treadmill; the belt always runs in sync with your footfalls. But an airplane is different. An airplane’s wheels are not powered by gears or a drive train. They hang inertly below, and are free-spinning. The thrust force that moves the plane along couldn’t care less about the ground. The engines are not fighting against the surface, they are fighting against the air.

Confusing, I know, and in the interest of full disclosure, physics was the one class in high school that I outright failed and had to take twice (you try ciphering out equations while listening to Minor Threat on a pair of clandestinely strung ear buds). And some of you might remember what happened the last time I combined things aeronautical and mathematical. So let’s get somebody else to explain.

According to Paul J. Camp, a professor in the department of physics at Spelman College, it’s all pretty simple. “At first, the conveyor will hold the plane still. But only to a certain point, after which, driven by thrust from its engines, the craft will accelerate.”

But the problem clearly states: The conveyer belt is designed to exactly match the speed of the wheels, moving in the opposite direction.

“The key is in the behavior of friction,” Camp says. “Friction is a peculiar force in that it has an upper limit. For instance, push an object on your desk, but not hard enough to move it. Why doesn’t it move? Because the friction force exactly balances the force of your push. At some point you push hard enough to set the object in motion. This is the point where friction has topped out and is not capable of growing any larger.”

With the airplane and treadmill, there is, at the outset, friction force capable of rotating the tires at the proper speed to keep the plane stationary. However, as the thrust is increased, that force eventually maxes out. (Two separate frictions are at play here, actually, one between the tires and belt, the other between the plane’s axles/bearings and its wheels. The first will max out before the second.)

“And at that point the wheels no longer roll, they slide,” says Camp. “Or rather, they roll and slide at the same time. Tire motion is now decoupled from the belt motion. No matter how much you whiz up the treadmill, you won’t add any more rotational velocity to the wheels because friction is already doing everything it is capable of. The plane skids toward takeoff — likely accompanied by much smoke and a powerful rubbery stink.”

And there you have it, at least on paper. Bear in mind that for a plane to reach that point of decoupling would require two things above and beyond the pale of normal engineering. First, a remarkable amount of power — far more than any jetliner, and probably any military plane, is capable of developing. The illustration on Pogue’s blog is of an Airbus A320; some sort of rocket plane would be more appropriate. Second, no existing aircraft tires could take such abuse. The rotational velocity required before reaching the friction limit would have them bursting within seconds, causing the plane to be flung backward. Believe it or not, landing gear isn’t engineered with giant treadmills in mind, and pilots need to adhere to maximum groundspeed limits, lest their tires wind up like this. These limits occasionally present problems during tailwind operations or in the case of flap and slat malfunctions — scenarios dictating the need for unusually high takeoff or landing speeds.

For good measure, the treadmill itself, as described, could never be built. It can’t “exactly match the speed of the wheels,” because the wheels will turn at the speed of the treadmill plus the speed of the plane relative to the ground. When the speed of the plane is greater than zero (which it is the moment its wheels start to spin; otherwise they would never move), then the problem becomes impossible. By definition, the wheels have to be turning faster than the treadmill.

Whose idea was this crazy problem?

Meanwhile I can’t decide if this is good or bad news for the conveyor belt industry and treadmill enthusiasts worldwide. Though, as they say, any publicity is good publicity.

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