So I’ve heard somebody wanted to see a gif of that moment when Brian Cox was ran over by Stephen Hawking. Here it is, I hope it loads.
This gif changed my life
Just another blog on physics and for me to share my findings
Sloshing is a problem with which anyone who has carried an overly full cup is familiar. Because of their freedom to flow and conform to any shape, fluids can shift their shape and center of mass drastically when transported. The issue can be especially pronounced in a partially-filled tank. The sloshing of water in a tank on a pick-up truck, for example, can be enough to rock the entire vehicle. One way to deal with sloshing is actively-controlled vibration damping - in other words, making small movements in response to the sloshing to keep the amplitude small. This is exactly the kind of compensation we do when carrying a mug of coffee without spilling. (Image credit: Bosch Rexroth; source)
There are five special points where a small mass can orbit in a constant pattern with two larger masses (such as a satellite with respect to the Earth and Moon). The Lagrange Points, named in honor of Italian-French mathematician Joseph-Louis Lagrange, are positions where the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them. This mathematical problem, known as the “General Three-Body Problem” was considered by Lagrange in his prize winning paper (Essai sur le Problème des Trois Corps, 1772).
The five Sun–Earth Lagrangian points are called SEL1–SEL5, and similarly those of the Earth–Moon system EML1–EML5, etc. Orbits around Lagrangian points offer unique advantages that have made them a good choice for performing certain spacecraft missions.
For example the Sun–Earth L1 point is useful for observations of the Sun, as the Sun is always visible without obstructions by the Earth or the Moon. SOHO, the ESA/NASA solar spacecraft is positioned there.
read descriptions about invidual L-points here
How to float a ping pong ball in mid-air
Dianna “Physics Girl” Cowern, physicist at UC San Diego’s Center for Astrophysics and Space Sciences, explains in this video how The Coandă Effect can make a ping pong ball float in mid-air.
Soap bubbles are ephemeral creations. The slightest prick will send them tearing apart in the blink of an eye. It may come as a surprise, therefore, that dropping a water droplet through a bubble will not break it. Instead, the bubble will heal itself using the Marangoni effect. In a soap bubble, the soap molecules act as a surfactant, lowering the surface tension of the water and allowing the fragile structure to hold together. When the water drop impacts the bubble, the local surface tension increases because of the relative lack of soap molecules. This increase in surface tension pulls at the rest of the bubble, drawing more soap molecules toward the point of contact. The effect evens out surface tension across the surface and stabilizes the bubble. You can test the effect at home, too. If you wet your finger, you can poke a soap bubble without popping it. (Video credit: G. Mitchell; via io9)
The evil geniuses at NASA Ames Research Center are trying to create super intelligent soccer balls with a top-secret vaporized serum! … er … wait, no. They’re just studying the aerodynamics of the official World Cup ball - the “Brazuca.”
Football fluid dynamics is a touchy subject on the international stage. Goalies hated the 2010 World Cup’s ball (the too-smooth “Jabulani”) because it was said to swerve and twist in the air. Joe Palca covered that story four years ago.
NPR: covering ball aerodynamics since 1971.
The mass of quantum particles is fundamentally unknowable
"This is because there’s that same inherent tension-and-uncertainty between energy and time as there is between position and momentum! So if you have a very small uncertainty in the timescale of a particular system, there must inherently be a very large energy uncertainty.
Think about this in terms of a particle’s lifetime, now. If a particle stably (or quasi-stably) exists for a very long period of time, its energy uncertainty can be very small. But what of an inherently short-lived, very unstable particle? Its energy uncertainty must be huge to compensate; Heisenberg demands it.
And now for the kicker: if there’s a large uncertainty in a particle’s inherent energy, and we know that there’s an energy-mass equivalence via E = mc^2, then the shorter a particle’s lifetime is, the less well-known its mass can be, even in principle!”
Just when you thought quantum mechanics couldn’t get any weirder: turns out that the mass of any individual particle is fundamentally UNKNOWABLE. Thanks a lot, Universe.