fuckyeahfluiddynamics:

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)

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skunkbear:

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.”

Geoff Brumfiel has the full story here.

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.

(via freshphotons)

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startswithabang:

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.

(via chris-tophe)

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fuckyeahfluiddynamics:

Like many sports, the gameplay in football can be strongly affected by the ball’s spin. Corner kicks and free kicks can curve in non-intuitive ways, making the job of the goalie much harder. These seemingly impossible changes in trajectory are due to airflow around the spinning ball and what’s known as the Magnus effect. In the animation above, flow is moving from right to left around a football. As the ball starts spinning, the symmetry of the flow around the ball is broken. On top, the ball is spinning toward the incoming flow, and the green dye pulls away from the surface. This is flow separation and creates a high-pressure, low-velocity area along the top of the ball. In contrast, the bottom edge of the ball pulls dye along with it, keeping flow attached to the ball for longer and creating low pressure. Just as a wing has lift due to the pressure difference on either side of the wing, the pressure imbalance on the football creates a force acting from high-to-low pressure. In this case, that is a downward force relative to the ball’s rightward motion. In a freely moving football, this force would curve its trajectory to the side. (GIF credit: SkunkBear/NPR; original video: NASA Ames; via skunkbear)

fuckyeahfluiddynamics:

Like many sports, the gameplay in football can be strongly affected by the ball’s spin. Corner kicks and free kicks can curve in non-intuitive ways, making the job of the goalie much harder. These seemingly impossible changes in trajectory are due to airflow around the spinning ball and what’s known as the Magnus effect. In the animation above, flow is moving from right to left around a football. As the ball starts spinning, the symmetry of the flow around the ball is broken. On top, the ball is spinning toward the incoming flow, and the green dye pulls away from the surface. This is flow separation and creates a high-pressure, low-velocity area along the top of the ball. In contrast, the bottom edge of the ball pulls dye along with it, keeping flow attached to the ball for longer and creating low pressure. Just as a wing has lift due to the pressure difference on either side of the wing, the pressure imbalance on the football creates a force acting from high-to-low pressure. In this case, that is a downward force relative to the ball’s rightward motion. In a freely moving football, this force would curve its trajectory to the side. (GIF credit: SkunkBear/NPR; original video: NASA Ames; via skunkbear)

(via atomic-whale)

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jtotheizzoe:

Richard Feynman discusses why there is a difference between the past and the future, in this clip from his legendary 1964 lecture series at Cornell: The Character of Physical Law.

It’s well worth taking 45 minutes out of your day to hear Dr. F explain why the workings of nature unfold in one direction. You see, while we innately know that the future is different from the past, and so much of our conscious experience is built around the fundamental just-so-ness of time moving forward, the equations of physics describing phenomena from gravity to friction can be run in either direction without breaking the rules. Yet irreversibility is what we observe.

That’s where entropy and probability come into play. When we take into account complex systems, like the jiggles and wiggles of the uncountable atoms that make up our bodies and this chair and my coffee and our world and even out to the scale of the universe itself, there is simply a greater chance that things will become more disordered than less. It’s not that the universe can’t run in reverse, it’s just that there are so many other ways for it not to.

Or as Feynman says, nature is irreversible because of “the general accidents of life”.

This seven-part series, which Open Culture has assembled in its entirety, captures the physicist in his prime, one year before he won the Nobel Prize and became a household name. Feynman was seemingly born for the scientific stage. He had this uncanny ability to weave profound observations of the universe’s inner workings with off-the-cuff (and often brash) humor. James Gleick wrote of Feynman’s unique style and skill:

He had a mystique that came in part from sheer pragmatic brilliance–in any group of scientists he could create a dramatic impression by slashing his way through a difficult problem–and in part, too, from his personal style–rough-hewn, American, seemingly uncultivated.

This clip was a huge influence on my recent video Why Does Time Exist? Although my take scarcely measures up to Dr. Feynman, you can watch below:

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(Source: chandra.harvard.edu, via chris-tophe)

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(Source: runningonoatmeal, via physicsninja)

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(Source: studygeek, via physicsninja)

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Misconceptions About the Universe

The expanding universe is a complicated place. During inflation the universe expanded faster than light, but that’s something that actually happens all the time, it’s happening right now. This doesn’t violate Einstein’s theory of relativity since nothing is moving through space faster than light, it’s just that space itself is expanding such that far away objects are receding rapidly from each other. Common sense would dictate that objects moving away from us faster than light should be invisible, but they aren’t. This is because light can travel from regions of space which are superluminal relative to us into regions that are subluminal. So our observable universe is bigger than our Hubble sphere - it’s limited by the particle horizon, the distance light could travel to us since the beginning of time as we know it.”

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