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Archive for the ‘Physics’ Category

Next Stop, Neptune, If the Brakes Work

Next time you’re in a pub with a dart board, pick up a dart, stand at the regulation distance, and toss a bull’s eye. Piece of cake, right? Now, stand in that same pub but throw the dart so that it goes into a nice, near orbit around Neptune. Not so easy this time, eh?

But we’re not done. To make things a little trickier, figure on using Neptune’s atmosphere to brake your dart’s velocity. While you’re at it, calculate the path your dart took to get from the pub to Neptune. Write that path out in a series of differential equations. Write a 500-word abstract. Do all this is 48 hours under the auspices of your faculty mentor. You’re almost done! Last step: enter the paper you’ve just written in the University Physics Competition.

With slight variations on the process above (like, they didn’t actually throw a dart), that’s what three WSU physics majors did. Julian Smith, Kyle Welch and Ken Dorrance spent a recent weekend bravely battling the complexities of Lagrangian mechanics to calculate just what it would take to get a rocket from Earth to Neptune. Their efforts won them a bronze award in the competition.

Left to right: WSU Physics and Astronomy majors Kenneth Dorrance, Kyle Welch and Julian Smith/photo and montage by Brian Charles Clark

A couple centuries ago, mathematician Joseph-Louis Lagrange made significant contributions to celestial mechanics, the area of math that deals with the movements of planets, moons and various other objects in space – including rockets. “Newton’s second law–force equals mass times acceleration–beautifully describes many simple physical systems when forces are known,” says Dorrance, a junior majoring in physics with the nanotechnology option. “Lagrangian mechanics lets you solve some less-than-simple systems without knowing the forces.”

All three of the young physicists agreed that the mechanics involved in aerobraking a probe in the atmosphere of Neptune is a complex business. “Julian and I spent a lot of time staring at the white board, looking for analytical solutions, while Ken worked on coding methods for finding numerical solutions,” says Welch, a senior from Olympia majoring in physics and neuroscience.

“Being someone who focuses on theory, I often like to believe that there will be a clean analytical solution for everything,” says Welch. “However, the complexity introduced by the drag of aerobraking showed me that sometimes you have to give up on finding an exact solution.”

Not only was the problem complex, but the three-person team had only 48 hours in which to formulate their solution. This involved investigating the composition of the upper reaches of Neptune’s atmosphere where the probe would experience frictional resistance and be slowed enough from its interplanetary velocity to go into orbit around the gas giant. Between the three of them, they hammered out a solution that satisfied them.

The University Physics Competition annually offers teams a choice between two problems.

“We chose the problem we thought would be the most interesting, and opted out of the one we thought would be easier to solve,” says Smith a senior in physics from Vashon Island. “The aerobraking problem was exciting for all of us but we really had to think outside the box. This contest taught us to be creative and to think quick.”

Michael Allen, the students’ mentor and competition advisor, says the competition problems are unlike what they would find in a textbook.

“The problems do not have a single approach, and do not have a single correct answer,” he says. “Also, the students are allowed Internet access whilst solving the problem, hence they have a lot of information available to them and must pick that tiny, relevant bit of it to use. In other words, there is scope for being creative, but there is also a need for discipline.”

Lightning 101, with slo-mo video and only a few big words

A loud, rousing thunderstorm is one of the rare treats in Washington State, the Lower 48’s last-place finisher for lightning strikes per square mile. One blew through Pullman a few nights ago, slamming doors in a late-summer fit of meteorological melodrama.

But as we’re fond of saying here at Discovery, when nature fails, there’s always the Internet, and few storms have lit up our browser more impressively than this bit of slow-motion footage of lightning strikes over Rapid City, SD. Unlike lightning in real time, the video makes it easy to see that lightning’s light—the bolts—not only go down but up. And not only do they strike the same place twice, they often follow the same route.

We ran this by Patrick Pedrow, associate professor in the School of Electrical Engineering & Computer Science, and got some helpful Lightning 101.

First, the basics: Lightning runs between large, separated pockets of positive and negative charges, some of which can accumulate on the earth and on protruding objects, like the towers in the video. Now and then, the charged pockets combine through what is called an “electron avalanche” and affiliated phenomena.  A free electron is accelerated away from a negative charge and towards a positive charge, and if the separated charge is large enough, the accelerated electron strikes and ionizes an atom or molecule. Now there are two free electrons, each of which is accelerated and can have collisions that make even more free electrons—and an electron avalanche.

Electron avalanches convert the air around them into a highly conductive channel of neutral and charged particles called plasma. Some channels can be less than a centimeter in diameter. When one “touches” the earth or a raised object, thousands of amperes of current flow through the channel to neutralize previously separated regions of charge and a very hot bright channel—a lightning bolt—forms.

Even after the glow disappears, the ionized channel remains and can act as a conduit for more currents and subsequent lightning bolts.

“The human eye integrates all of this emitted light together,” says Pedrow, “and the typical observer reports only one ‘lighting strike.’ But as shown in the film clip there can be a large number of charge pockets being ‘drained’ in one lightning event.”

Video courtesy Tom A. Warner of ZT Research

Science in the Sky: The WSU Planetarium

Note: This is the first in our new series, “Scene Around Campus: A Glimpse into WSU’s Corners and Curiosities.” Join us as we explore the many nooks and crannies of campus that residents and visitors might otherwise miss.

Welcome to “The Whoa Moment.”

You’re ushered into a room down a musty hallway. You take a seat, the lights go out, and — after a moment of darkness — the night sky flickers above you, a canopy of fuzzy white dots representing the universe as seen from Pullman. You forget about the world outside as you’re lost in space.

The Washington State University Planetarium is a 1960s star projector tucked away in Sloan Hall. WSU astronomers Michael Allen, Guy Worthey and Ana Dodgen lovingly keep it clean and in working order.

The planetarium is dated and clunky, but the astronomers’ faces light up when they talk about the roughly 2,000 fifth- and sixth-graders who visit every year on field trips.

“The little kids get so excited about what we’re telling them,” Dodgen says. “It’s a way to spark their curiosity in astronomy and science.”

Set up in 1962, the planetarium is likely older than these kids’ parents and possibly their grandparents. Working with the WSU Foundation, the astronomers are trying to collect donations to update the facility with a digital projector. Mostly, they’re hoping for a big donor, someone star-happy enough to hand over $50,000 or $70,000.

“Everyone loves the planetarium, but in terms of loving it enough to empty your wallet … that hasn’t happened yet,” Worthey says.

Within the planetarium, the projector is run from a main console with knobs for each celestial body. There are motors to animate daily, monthly and yearly paths. The console looks like a 1920s radio.

“This is like Frankenstein’s laboratory down here,” Worthey jokes during a recent visit, swinging Mars — a tiny red dot — across the screen.

Despite fuzziness and flickering, the northern hemisphere mostly works. From certain angles, pieces of the projector, a big black globe dotted with pinholes, block much of the rest of the sky. If you pick the wrong seat, the Southern Cross and Alpha Centauri might be obliterated.

The planetarium is closed to the public and used mainly for undergraduate science classes and local middle and elementary schools. However, WSU and community groups can schedule free shows through Allen or the physics department at astro.wsu.edu or 509-335-1279.

The Optics Man of Cairo

Geologist and science scribe Kirsten Peters regularly writes on the art and science of discovery for her Rock Doc column, syndicated in newspapers across the country and available at rockdoc.wsu.edu. Her latest column, a service of the College of Sciences at Washington State University, marvels at the man widely considered the Father of the Scientific Method.

Sometimes it pays to spend ten years in detention. Not that a person would ever want that to happen, but if it did – could you put the time to good use?

That’s a question I’ve asked myself. I’ve also asked my students exactly the same thing. The value of a good high school or college education, I say to them, is that it should give you the tools to use time like that well. What would you do with it?

Image courtesy of Wikipedia

One thousand years ago an Arab man named Ibn al-Haytham found himself under house arrest in Cairo. That far back ago in time, we don’t know much of the specifics of Ibn al-Haytham’s life. But we do know he was a towering giant of an intellectual in his day.

If you give a thinking person ten years to think, don’t be surprised if there are some powerful results in the end. In Ibn al-Haytham’s case, a good argument can be made that the ten-year gap in his life was quickly followed by the release of his major book on optics. That book was pivotal to our lives today, because optics was hardly the only issue it addressed.

In the ancient world – more than 1,000 years before Ibn al-Haytham’s own life – Greek philosophers had two main theories of vision. One theory (advanced by Ptolemy and Euclid) was that “vision rays” left the eye and went out to objects around us in the world. The other was put forward by Aristotle. The great philosopher had argued a “form” of some sort comes from an object in the world around you and enters your eye so you can see it.

Ibn al-Haytham pointed out, first, that not all the ancient Greek authorities could be right, since they followed two contradictory ideas on the subject. Then he noted that we don’t have vision unless there is light around us: either light from the object we are seeing (like a lamp) or light rays from reflected light (like sunlight in the day). So light, first, is what we need to understand in order to better understand vision.

Using only logic like this and a few simple experimental materials – a pinhole in a curtain or a hollow straight tube – Ibn al-Haytham went on to deduce a great deal about modern optics. Light rays travel in straight lines. Light on flat mirrors is reflected in one set of ways, and on curved mirrors in others.  Light is refracted (bent) when it moves from air to water.

Most importantly of all, Ibn al Haytham did all this good work using experiments and observations, writing out for his readers what they could do to show themselves the same evidence he had seen and reach the same conclusions.

That’s not bad for 10 years of work under nice conditions. For 10 years in detention, it’s really a remarkable feat.

Two hundred years passed after the death of the Arab scholar before a Christian monk took up a translated volume of the work and saw its value. Roger Bacon was our hero’s name. He was not Francis Bacon – there are two Bacons rattling around in history. Roger Bacon repeated some of Ibn al-Haytham’s experiments – but he also endorsed for the Christian tradition this new method of gaining new knowledge about the natural world. Experiments and testing of physical facts, Bacon argued, were the most productive ways to learn about the physical world around us. Others around Bacon were soon on board with the program, and Medieval Europe began to have at least an inkling of the modern, scientific method.

The reason science and engineering have been able to progress so much in our lifetimes is that the method of running experiments and testing results is enormously successful.  But in the old world, it was far from clear that this approach would lead to the most sound results.

We owe Ibn al-Haytham and Roger Bacon a lot, not just for their good work on optics, but for recognizing the power of the scientific method that has given us so much today.