Clear Science!

One of the most vexing topics for fluid dynamicists and their audiences is the subject of how wings generate lift. As discussed in the video above, there are a number of common but flawed explanations for this. Perhaps the most common one argues that the shape of the wing requires air moving over the top to move farther in the same amount of time, therefore moving faster. The flaw here, as my advisor used to say, is that there is no Conservation of Who-You-Were-Sitting-Next-To-When-You-Started. Nothing requires that air moving over the top and bottom of a wing meet up again. In fact, the air moving over the top of the wing outpaces air moving underneath it. 

In the Sixty Symbols video, the conclusion presented is that any complete explanation requires use of three conservation principles: mass, momentum, and energy. In essence, though, this is like saying that airplanes fly because the Navier-Stokes equations say they do. It’s not a terribly satisfying answer to someone uninterested in the mathematics. 

Part of the reason that so many explanations exist – here’s one the video didn’t touch on using circulation – is that no one has presented a simple, intuitive, and complete explanation. This is not to say that we don’t understand lift on fixed wings – we do! It’s just tough to simplify without oversimplifying. 

Is zero a number? Was it always a number?

Today, zero has two roles: First, as a placeholder within our number system, representing an absence of a value. It allows us to create huge numbers without extra digits. Its second role is as a number in its own right, in between -1 and 1. We can subtract, add, multiply by 0… but dividing gets tricky. I mean, you can’t divide 1 chicken by 0 chickens:

(You might think the answer would be infinity chickens, but it’s not, as infinity is a concept, not a number)

Most ancient civilisations developed some sort of number system to keep track of things, and they are all thought to have had a general concept of zero.

And when the Indians began developing a number system (the one that evolved into what we use today), zero was first explicitly born, with 9 number symbols and a dot to represent the absence of a number.

In the 7th Century, Brahmagupta developed terms for zero in addition, subtraction and division… though he struggled a bit with that last one.

Over time, the mathematics of India matured and spread outwards. But it found resistance in Europe, in particular against the established Roman numeral system.

But by the 13th century academics like Fibonacci were championing zero, helping it gain a solid foothold across Europe:

Zero went on to form the cornerstone of calculus, which allowed anyone to break down dynamic systems into smaller and smaller units approaching zero, but never quite getting there, avoiding the tricky problem of dividing by zero.

More recently, the binary numerical system formed the basis of the computer system and zero’s importance shone once more.

We can’t be the only ones disappointed that the Internet fails to provide a beautiful electromagnetic spectrum, right? So we enlisted the aid of our graphic design team to put together this lovely ocean-inspired image, which covers everything from blue whales to oxygen atoms. Look at that pygmy seahorse!

Electromagnetic radiation—including radio waves, visible light, and x-rays—rises and falls as it travels through space, like waves rippling across the ocean. The length of these waves, measured from peak to peak or valley to valley, helps define their properties and potential uses.

At Brookhaven, we specialize in exploring the ultra-small right end of the spectrum using ultra-bright x-rays, electron microscopes, and other fantastic tools. Investigating materials at that scale allows fundamental discoveries that can revolutionize our understanding of biology, energy technology, and even the cosmos.

The paper describes an innovative new cathode design for batteries. (A cathode is one of the two battery electrodes.) However, most reports of the paper in the mainstream and scientific press have focused on the idea that a real-world battery developed using this cathode will charge in less than 60 seconds.

A battery scientist’s trivial dilemma

You may find yourself hunting through all the batteries at the drugstore, trying to find an LR44 to buy instead of a 303/357. All because you want to be ‘faithful’ to MnO2. (By the way, this particular day you won’t find one.)

Functionally, these button cells are essentially interchangeable, but they have different active materials inside them. The LR44 is an “alkaline” battery which has the overall reaction:

3 MnO2 + 2 Zn = Mn3O4 + 2 ZnO

The 303/357 is a silver oxide battery having the overall reaction:

Zn + Ag2O = 2 Ag + ZnO

Laser-sparked fusion power passes key milestone  |  New Scientist

Okay, okay, okay, okay, guys. Scientists at the National Ignition Facility have taken the first itty bitty baby steps towards fusion and I’m having trouble containing my excitement.

First of all, they’re using 192 laser beams, which are pointed at a gold chamber that converts the lasers into X-ray pulses, which then squeeze a small fuel pellet and make it implode and undergo fusion. That anyone ever figured out even how to do this is completely nutso.

Secondly, the lead researcher is named Omar Hurricane. I have never in my life heard a better name. He sounds like a comic book character. Please someone write a comic starring Omar Hurricane and his band of laser-wielding scientists.

And then there’s what it actually means. So far, they’ve been able to get 15 kilojoules of energy out of a fuel pellet that was blasted with 10 kilojoules. But, as The Guardian points out, much more energy is delivered by the lasers (and lost in the conversion to X-rays): “The lasers unleash nearly two megajoules of energy on their target, the equivalent, roughly, of two standard sticks of dynamite.” 

Even so, this is a hugely significant tiny step forward toward recreating the clean energy production that happens in the heart of stars.

(via chels)

Due to a peculiarity of nuclear physics, you can release energy either by 1) breaking apart heavy atoms, or 2) forcing together light atoms. Breaking apart is called fission and forcing together is called fusion. We already know how to generate energy by man-made fission, but generating energy by man-made fusion remains an aspiration. (Of course, we know how to build bombs both ways. Nuclear and thermonuclear bombs respectively.)