But Does It Work On Ducks?

“So, a fake force is a force that is not an interaction between two objects. Rather it is like duck tape (I refuse to call it duct tape because it isn’t good for ducts) on your accelerating frame.”

Rhett Allain

Coriolis diagramWhat? I mean, it’s an obvious question, right?

Er … never mind*. But the consideration of physics in a game show context, from 2011, is still worth a read. Today’s discussion of gravity in a space movie is just as rewarding.

* I know … I know, I know. I just needed a title. Or, okay, to be honest, it was the first one that occurred to me.


“Okay, here’s what we’ve got: The Rand Corporation, in conjunction with the Saucer People, under the supervision of the Reverse Vampires, are forcing our parents to go to bed early in a fiendish plot to eliminate the meal of dinner.”

Milhouse van Houten

Fabian Oefner, Black Hole (detail)Cassini buzzes Titan again today.

• Paint … drill … physics … camera … art.

• This time it’s in Turkey; or, they found Hell … again.

• Er … oh, wait … Ur? (Wait, wasn’t that the Geo Quiz last week?)

Rhett Allain would like to confuse you; but then he sets everything straght again, so it’s safe to click the link.

• Today’s vocabulary lesson: ectopic eyes.

A Brief Physics Lesson: Bicycle Edition

Math? Physics? Those who enjoy brief exercises in applied speculation will certainly learn a thing or two from Rhett Allain, who took some time to consider bicycles and hills. At first blush, it seems an easy enough question: What’s the steepest gradient you could possibly ride on a road bike?

Of course, there is a difference between the simplicity of straightforward mathematics and the complexity of accounting for all the factors required.via Rhett Allain

I think there are three reasons why a slope would be too steep. For all of these cases, I am going to assume that it is a prolonged slope. This means that you can’t just build up a large speed and zoom up the slope. If this was the case, you could go straight up a wall (which you can for a short time).

Those three reasons are the limitations of human power, center of mass, and friction. If one wishes to point out, “What if you used these tires instead of those?” or, “What if you had a different gear set?” it’s all well and fine to do so, but therein lies the point about the complexity of accounting for all the factors required.

via Rhett AllainReally, the friction problem might be worse than this. The bike only uses the back wheel for moving forward, so it is the friction on the back wheel that matters. If the biker is leaning forward, the weight distribution might not be even on the two wheels. I will leave this estimation (combining the previous two limits) as an exercise for the reader.

And, of course, one is welcome to pursue such endeavors. (In truth, that might be part of the point.)


File under Whoops: I somehow managed to kill my Linkadelica template. No worries, I guess. I still haven’t figured out exactly what to do with it.

Abell 68 Space Invader (detail)Space Invaders! Or, a note on gravitational lensing.

Helicoprion! Or, the mysterious, spiral-toothed, squid-eating fish of antiquity.

Zen Pencils! Or, an ode to Chris Hadfield.

Dolighan! Or, as long as we’re speaking of Cmdr. Hadfield.

Tim Dolighan, March 1, 2013Thunder! Or, what Cmdr. Hadfield sees.

Physics! Or, Rhett Allain uses Neil deGrasse Tyson complaining about The Daily Show logo to teach us some science.

Heat! Fascinating and philosophical. Yes, really.

e, Not E, and Before e-

Apparently, I missed e Day. More than likely, so did you. Don’t worry, though, there will be another chance this year, though you’ll be celebrating with Europeans.

Rhett Allain didn’t miss e Day:

Why is Feb. 7 e Day? Well, in the USA we use the Middle-endian date format. So, Feb. 7 would be commonly written as 2/7/13. Guess what? The first two digits of e are 2.7. If you live in other places you might use the little-endian date format. In this case 2/7/13 would be July 2. For those people, just consider this an early post.

But don’t get distracted. (Yes, my first question was the same as yours: “Really? It’s really called ‘Middle-endian’?

But e Day is a celebration of e, the jealous little brother of π.

Allain offers his favorite definition: “e is the number that if you raise that number to the power x, the slope of the function is the same value as the function.

And it just goes downhill from there. Or uphill, I guess, if you look at it on a graph. Sort of. The graph at right does not show you e. Maybe you could try reading the Wikipedia entry on e, but that’s the fun thing about being a poor mathematician and clueless excuse for a scientist.

Sometimes called Euler’s number after the Swiss mathematician Leonhard Euler, e is not to be confused with γ—the Euler–Mascheroni constant, sometimes called simply Euler’s constant. The number e is also known as Napier’s constant, but Euler’s choice of this symbol is said to have been retained in his honor.

By the time you get to the part about derangements, well, yeah.

Oh, right. e = 2.71828 (and a whole bunch of numbers after that; it’s irrational and trancendental, just like π).

Science and Star Wars

The Death of Admiral OzzelAs Star Wars fever heats up toward its inevitable pandemic in 2015, when J. J. Abrams is slated to release the yet-untitled Chapter VII, the first symptoms are already apparent over at Wired Science, where physics professor Rhett Allain reflects on his Reddit AMA session discussing the science of the cinematic saga. Actually, he’s giving out homework:

• How hot is a light saber? (from roguepublichealth) I think you have to first figure out what a light saber actually is and why it glows.

• How much material would be needed to build the Death Star (from astanisic) You will obviously need some estimates here. If you want a second question, how long would it take to put this Death Star together. You can answer for both the first (Episode IV) and second (Episode VI) Death Stars – which are different sizes.

The physics of choking someone to deathAnd so on. In truth, it’s not one of his better Dot Physics posts, but only because he’s asking the questions and not explaining the answers. For instance, there is more to learn from his consideration of the vital question, “How much does Darth Vader weigh?”

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