Bernoulli Is Not Enough

By Simon Shapiro

Probably all of us science geeks think we know how aeroplanes fly. It’s thanks to the Bernoulli Principle, which says that faster flowing air exerts less pressure than slower air. Aeroplane wings are designed with flat bottoms and rounded tops. Air has to flow more quickly around the longer top surface than the shorter bottom surface. That gives us higher pressure below the wing and lower pressure above the wing.

This diagram is from my book, Faster, Higher, Smarter: Bright Ideas that Transformed Sports. (More information here; available from Amazon, Indigo, etc.)

So, the upward Bernoulli force overcomes the downward force of gravity, and the aeroplane can fly.

But there's a problem:

Think about a plane doing aerobatics. A pilot will happily flip her plane upside down and can fly that way indefinitely (at least until the plane runs out of fuel). But in the upside down configuration the Bernoulli force is directed downwards, just like gravity. So with both forces acting downward, how come the aeroplane doesn’t fall like a stone? Worse than that, like a stone with an extra downward force?

The answer is that there’s another factor, usually overlooked. And that’s the Angle of Attack. Aeroplanes don’t usually fly with the bottom of the wing parallel to the ground. They usually fly with the leading edge tilted up. That tilt angle is called the Angle of Attack.

In this configuration the wing pushes against the air and (thank you, Sir Isaac) experiences a normal (perpendicular to the surface) reaction  of wind resistance. That’s shown as the red arrow in the diagram above. The force shown by the red arrow is the same as two forces – a vertical one (shown by the green arrow) and a horizontal one (shown by the tiny blue arrow). That vertical “green arrow” force counteracts gravity, and is what keeps an upside-down aeroplane in the air.

In fact the Bernoulli effect alone isn’t strong enough to keep a heavy modern jet plane up. The Angle of Attack is critical even when the plane is flying rightside up.

Sing a Song of Science

Do you ever wish that scientists could just explain what they do in simple words? Or at least, explain a little of what they do? Or maybe even just talk about their studies without using big words in a way that makes everyone else feel foolish for not knowing the words?

What about if they sang?

No kidding. There are actually songs to be found that were written by scientists, and that were written about science. Some of the songs use familiar tunes, or tunes from classical music. You can find recordings of many of these songs on the Internet. And yes, most of these songs have been written by someone with a sense of humour, and a sense of wonder.

For chemists, there's a classic song written by comedian Tom Lehrer which names all the elements of the periodic table. All of them, in a list of names that isn't alphabetical and only parts of it are sorted. He sings the names of the elements to a tune by the composers Gilbert and Sullivan, called "The Modern Major-General." Lehrer's song has been sung on television shows about science, like "The Big Bang Theory" and older shows such as "Gilmore Girls."
It's hard to imagine how anyone can ever remember all the names of the elements like this. Singing this song is a fun feat of science memory. Daniel Radcliffe, who played Harry Potter in the films based on J.K. Rowling's books, has been known to sing this song at parties.

This kind of singing even works for particle physics. How about a discussion of string theory that's set to the tune of a famous song? It's neat to think that an explanation for how the building blocks of the universe work can not only make sense, but it can rhyme! This particular song is called "Bohemian Gravity" as it is a parody of the song "Bohemian Rhapsody" by the rock band Queen.
The video for this song was made up of 70 hours of recordings by a physics student while he was studying for his Master's degree. He uses the name Acapella Science when posting his videos on YouTube for others to enjoy. As one fan wrote in the comments section on the video's webpage, "I'm sure Brian May, the guitarist of Queen with a PhD an Astrophysics, would approve of this video if he sees it."

The Monty Python comedy troupe have covered astronomy in their song about the expanding universe. For philosophy, there's a drinking song written by the Pythons which names most of the philosophers studied at University -- but describes the philosophers as drinking a lot of booze. That's one song for young scientists to hear or sing only with their parents' advice. Listening to science songs might be a fun thing for a family to do together. And singing them certainly can be fun!

What's NOT a black hole?

By M. E. Powell
(Photo - http://creativity103.com)

Scientists and science fiction writers often influence or inspire each other. I gained some insight into that process during "When Words Collide," the Calgary science fiction and genre writers festival, earlier this year.

For example,  David Wesley Hobill of the University of Calgary led a workshop in his special interest subjects: black holes, dark energy, and dark matter. I'm sure I'll over-simplify what he said, but his lecture shed some light on the "dark side of the universe" for me.

Hobill talked about finding black holes by observing gravitational effects. For example, we may observe a quasar at a far distance from Earth. If something is between us and the quasar, we know the gravity of that object will bend the light coming from the quasar. This "gravitational lensing" results in multiple images. If we observe light bending or being redirected around an object, but we can't see what is causing the light to bend, we deduce that a black hole is likely the cause.

Gravitational time delays caused by strong gravity may also cause time to slow down. Curved space requires more time to traverse. Inside it, a person's heartbeat may slow to two beats per hour, for instance, causing the person to live longer. Time would appear to stop. (You can imagine what science fiction writers might make of that train of thought!)

Hobill also debunked some popular science fiction myths about black holes. For example, he said, black holes are not:
- cosmic vacuum cleaners
- portals to another universe
- made of dense material.
In fact, black holes are completely empty space, he said, caught at the moment of a change of energy.

Instead, he pointed out, scientists would say that black holes are:
- formed from the gravitational collapse of a star 
- empty of space-time
- boundaries of causally separated regions
- cold and black
- and very very small.
If our sun collapsed into a black hole, for example, it would implode the gravitational forces, and it would become 400,000 times smaller. In other words, Hobill said, it would end up being about the size of downtown Calgary.

Here are some interesting links to follow up, if you're interested in black holes:
Hubble Site: Black Holes - Gravity's relentless pull: http://hubblesite.org/explore_astronomy/black_holes/
NASA: Black Holes - What are they? http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html
NASA: What is a black hole? http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-a-black-hole-k4.html 
Black Holes - Frequently asked questions: http://cosmology.berkeley.edu/Education/BHfaq.html

M. E Powell is the a Regina-based professional writer and the author of Dragonflies are Amazing (Scholastic Canada, 2007).