Category: physics

Listen to the Sound of Saturn’s Electrom…

Listen to the Sound of Saturn’s Electromagnetic Energy

Via Gizmodo (source at NASA)

New model predicts that we’re probably t…

New model predicts that we’re probably the only advanced civilization in the observable universe. Via Universe Today.

Well, playing with the Drake equation and the Fermi paradox is always fun and educative, as long as you assume that you are on a purely speculative ground. We actually don’t know, and the “probably” adverb in the title is central.

From the original paper’s abstract (Dissolving the Fermi ParadoxPDF):

[…] The expectation that the universe should be teeming with intelligent life is linked to models like the Drake equation, which suggest that even if the probability of intelligent life developing at a given site is small, the sheer multitude of possible sites should nonetheless yield a large number of potentially observable civilizations. We show that this conflict arises from the use of Drake-like equations, which implicitly assume certainty regarding highly uncertain parameters. We examine these parameters, incorporating models of chemical and genetic transitions on paths to the origin of life, and show that extant scientific knowledge corresponds to uncertainties that span multiple orders of magnitude. This makes a stark difference.

Football Physics: The Science Behind the Banan…

teded:

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In 1997 in a game between France and Brazil, a young Brazilian player named Roberto Carlos set up for a 35 meter free kick. With no direct line to the goal, Carlos decided to attempt the seemingly impossible. His kick sent the ball flying wide of the players, but just before going out of bounds it hooked to the left and soared into the goal.

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According to Newton’s first law of motion, an object will move in the same direction and velocity until a force is applied on it. When Carlos kicked the ball he gave it direction and velocity, but what force made the ball swerve and score one of the most magnificent goals in the history of the sport?

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The trick was in the spin. Carlos placed his kick at the lower right corner of the ball, sending it high and to the right, but also rotating around its axis. 

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The ball started its flight in an apparently direct route, with air flowing on both sides and slowing it down. On one side, the air moved in the opposite direction to the ball’s spin, causing increased pressure, while on the other side—the air moved in the same direction as the spin, creating an area of lower pressure. 

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That difference made the ball curve towards the lower pressure zone. This phenomenon is called the Magnus effect.

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This type of kick, often referred to as a banana kick, is attempted regularly, and it is one of the elements that makes “The beautiful game” beautiful. 

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But curving the ball with the precision needed to both bend around the wall, and back into the goal is difficult. Too high and it soars over the goal. Too low and it hits the ground before curving. Too wide and it never reaches the goal. 

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Not wide enough and the defenders intercept it. Too slow and it hooks too early or not at all. Too fast and it hooks too late.

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The same physics make it possible to score another apparently impossible goal—an unassisted corner kick.

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The Magnus effect was first documented by Sir Isaac Newton after he noticed it while playing a game of Tennis back in 1670. It also applies to golf balls, Frisbees and baseballs. In every case the same thing happens: the ball’s spin creates a pressure differential in the surrounding airflow that curves it in the direction of the spin.  

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And here’s a question: could you theoretically kick a ball hard enough to make it boomerang all the way around back to you?  Sadly, no. Even if the ball didn’t disintegrate on impact or hit any obstacles, as the air slowed it, the angle of its deflection would increase, causing it to spiral into smaller and smaller circles until finally stopping. And just to get that spiral you’d have to make the ball spin over 15 times faster than Carlos’s immortal kick. So good luck with that.

From the TED-Ed Lesson Football physics: The “impossible” free kick – Erez Garty

Animation by TOGETHER

Just some facts you can throw out while watching the World Cup this summer.

My first code in Mathematica goes back to V2 (…

My first code in Mathematica goes back to V2 (1991) for the first reliable graphical environment from Microsoft (Windows 3.0, 3.1), lab reports improved instantly. Many things have changed in three decades in the world of computer algebra systems, even to the point to be of (irremediably) minority use, mostly because there are plenty alternatives both for high (Matlab, Octave, Sage) and low level (C, C++, Fortran…), or both (Python, Java, R…). But for people of a couple of generations (those born in the 60s and 70s or so) coming from an almost purely analogical world, seeing a pioneer (back then and now) of that generation as Stephen Wolfram (1959), posting this about the software that he himself had developed from the scratch before his 30 birthday, well, it makes us… happily nostalgic.

In her short life, mathematician Emmy Noether …

In her short life, mathematician Emmy Noether changed the face of physics:

About the David Hilbert’s answer to opposers to Emmy Noether’s application for the position of Privatdozent at University of Göttingen, the full quote goes:

“I do not see that the sex of the candidate is an argument against her admission as privatdozent. After all, we are a university, not a bath house.”

Noether’s application was rejected anyway, but Hilbert arranged for her to stay at Göttingen by having her lectures announced under his name. [See here or here]

Nano-discs act as micro-resonators, trapping i…

Nano-discs act as micro-resonators, trapping infrared photons and generating polaritons. When illuminated with infrared light, the discs concentrate light in a volume thousands of times smaller than is possible with standard optical materials. At such high concentrations, the polaritons oscillate like water sloshing in a glass, changing their oscillation depending on the frequency of the incident light. 

Credit: Harvard SEAS

Via Phys.org: Squeezing light at the nanoscale—Ultra-confined light could detect harmful molecules

Paper (Science Advances  – 15 Jun 2018): Ultra-confined mid-infrared resonant phonon polaritons in van der Waals nanostructures (PDF)

A pioneering physicist explains why it’s okay …

A pioneering physicist explains why it’s okay to not have all the answers:

Interesting interview with theorist Brian Greene, I liked his concept of personalized education, I think he could be quite right on this.

“[…] I think in some number of years we’ll have a far more personalized approach to education. Kids are different. They come at things completely differently, different DNA, different experiences. If we could allow them to drive the right way to learn for their particular biochemical and neurophysiological make-up, how much more powerful would that be than a one-size-fits-all approach, which is what we do now?

Beautiful illustration by Maciej Rebisz for a …

Beautiful illustration by Maciej Rebisz for a Quanta Magazine article about Penrose’s cosmic censorship hypotheses:

Mathematicians Disprove Conjecture Made to Save Black Holes

Surely If I were in Los Angeles area I would t…

Surely If I were in Los Angeles area I would try to go to the Caltech’s Beckman Auditorium to celebrate Richard Feynman’s 100th birthday. Relatives, friends, and top-notch colleagues will be there remembering Richard Feynman, one of the big theoretical physicists of the XX’s century, and hence, one of the giants of the human history.

Fair enough.

Fair enough.

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