physics gifs

We’re used to radiation being invisible. With a Geiger counter, it gets turned into audible clicks. What you see above, though, is radiation’s effects made visible in a cloud chamber. In the center hangs a chunk of radioactive uranium, spitting out alpha and beta particles. The chamber also has a reservoir of alcohol and a floor cooled to -40 degrees Celsius. This generates a supersaturated cloud of alcohol vapor. When the uranium spits out a particle, it zips through the vapor, colliding with atoms and ionizing them. Those now-charged ions serve as nuclei for the vapor, which condenses into droplets that reveal the path of the particle. The characteristics of the trails are distinct to the type of decay particle that created them. In fact, both the positron and muon were first discovered in cloud chambers! (Image credit: Cloudylabs, source)

In slow motion, vortex rings can be truly stunning. This video shows two bubble rings underwater as they interact with one another. Upon approach, the two low-pressure vortex cores link up in what’s known as vortex reconnection. Note how the vortex rings split and reconnect in two places – not one. According to Helmholtz’s second theorem a vortex cannot end in a fluid–it must form a closed path (or end at a boundary); that’s why both sides come apart and together this way. After reconnection, waves ripple back and forth along the distorted vortex ring; these are known as Kelvin waves. Some of those perturbations bring two sides of the enlarged vortex ring too close to one another, causing a second vortex reconnection, which pinches off a smaller vortex ring. (Image source: A. Lawrence; submitted by Kam-Yung Soh)

Note: As with many viral images, locating a true source for this video is difficult. So far the closest to an original source I’ve found is the Instagram post linked above. If you know the original source, please let me know so that I can update the credit accordingly. Thanks!

Catching prey using Vortices

I was reading about Vortices and after hours of research online, out of the blue I stumbled upon this amazing bird. This is the Red Necked Phalarope and from the looks of it seems to have put vortices to a really productive use - catching its prey.

By rotating around ~60-80 times a minute, it produces an upward vortex that sucks out insects/bugs/crustaceans from the water, which it swiftly picks up with its beak and eats. ( This one would have aced the Fluids class for sure :D)

This is analogous to tornadoes sweeping up cars and houses along its way in an upward swirl.

Mind Blown!

** The actual dynamics of vortices of course is waay more complicated. ;)

*** There are three species of phalarope (red-necked, red/grey, and Wilson’s), and they can all feed like that.            

“If there is energy within the substance it can only come from without. This truth was so manifest to me that I expressed it in the following axiom: ‘There is no energy in matter except that absorbed from the medium…’ If all energy is supplied to matter from without then this all important function must be performed by the medium.”

“When radio-active rays were discovered their investigators believed them to be due to liberation of atomic energy in the form of waves. This being impossible in the light of the preceding I concluded that they were produced by some external disturbance and composed of electrified particles. My theory was not seriously taken although it appeared simple and plausible. Suppose that bullets are fired against a wall. Where a missile strikes the material is crushed and spatters in all directions radial from the place of impact. In this example it is perfectly clear that the energy of the flying pieces can only be derived from that of the bullets. But in manifestation of radio-activity no such proof could be advanced and it was, therefore, of the first importance to demonstrate experimentally the existence of this miraculous disturbance in the medium. I was rewarded in these efforts with quick success largely because of the efficient method I adopted which consisted in deriving from a great mass of air, ionized by the disturbance, a current, storing its energy in a condenser and discharging the same through an indicating device. This plan did away with the limitations and incertitude of the electroscope first employed and was described by me in articles and patents from 1900 to 1905. It was logical to expect, judging from the behavior of known radiations, that the chief source of the new rays would be the sun, but this supposition was contradicted by observations and theoretical considerations which disclosed some surprising facts in this connection.

“Light and heat rays are absorbed in their passage through a medium in a certain proportion to its density. The ether, although the most tenuous of all substances, is no exception to this rule.  Its density has been first estimated by Lord Kelvin and conformably to his finding a column of one square centimeter cross section and of a length such that light, traveling at a rate of three hundred thousands kilometers per second, would require one year to traverse it, should weigh 4.8 grams. This is just about the weight of a prism of ordinary glass of the same cross section and two centimeters length which, therefore, may be assumed as the equivalent of the ether column in absorption. A column of the ether one thousand times longer would thus absorb as much light as twenty meters of glass.  However, there are suns at distances of many thousands of light years and it is evident that virtually no light from them can reach the earth. But if these suns emit rays immensely more penetrative than those of light they will be slightly dimmed and so the aggregate amount of radiations pouring upon the earth from all sides will be overwhelmingly greater than that supplied to it by our luminary. If light and heat rays would be as penetrative as the cosmic, so fierce would be the perpetual glare and so scorching the heat that life on this and other planets could not exist.

“Rays in every respect similar to the cosmic are produced by my vacuum tubes when operated at pressures of ten millions of volts or more, but even if it were not confirmed by experiment, the theory I advanced in 1897 would afford the simplest and most probable explanation of the phenomena. Is not the universe with its infinite and impenetrable boundary a perfect vacuum tube of dimensions and power inconceivable? Are not its fiery suns electrodes at temperatures far beyond any we can apply in the puny and crude contrivances of our making? Is it not a fact that the suns and stars are under immense electrical pressures transcending any that man can ever produce and is this not equally true of the vacuum in celestial space? Finally, can there be any doubt that cosmic dust and meteoric matter present an infinitude of targets acting as reflectors and transformers of energy? If under ideal working conditions, and with apparatus on a scale beyond the grasp of the human mind, rays of surpassing intensity and penetrative power would not be generated, then, indeed, nature has made an unique exception to its laws.

"It has been suggested that the cosmic rays are electrons or that they are the result of creation of new matter in the interstellar deserts. These views are too fantastic to be even for a moment seriously considered. They are natural outcroppings of this age of deep but unrational thinking, of impossible theories, the latest of which might, perhaps, deal with the curvature of time. What this world of ours would be if time were curved…“

–Nikola Tesla

“The Eternal Source of Energy of the Universe, Origin and Intensity of Cosmic Rays.” October 13, 1932.

The simple harmonic oscillator

Anonymous asked: Please explain the intuition of solving the SHM equation.

Okay Anon! Here you go, this is my rendition.


The problem

You have a mass suspended on a spring. We want to know where the mass will be at any instant of time.

Describe the motion of the mass


The physical solution

Now before we get on to the math, let us first visualize the motion by attaching a spray paint bottle as the mass.

Oh, wait that seems like a function that we are familiar with - The sinusoid.

Without even having to write down a single equation, we have found out the solution to our problem. The motion that is traced  by the mass is a sinusoid.


But what do I mean by a sinusoid ?

If you took the plotted paper and tried to create that function with the help of sum of polynomials i.e x, x2, x3 … Now you this what it would like :

By taking an infinite of these polynomial sums you get the function Since this series of polynomial occurs a lot, its given the name - sine.

I hope this shed some light on the intuition of the SHM equation. Have fun!

Around 6 million years ago, the African and Eurasian plates moved together, cutting the Mediterranean Sea off from the Atlantic. Without an influx of water from the Atlantic, evaporation began removing more water from the Mediterranean than rivers could replace. The sea dried out almost completely over the course of a couple thousand years.

About 5.3 million years ago, the Straits of Gibraltar reopened, creating a massive flood into the Mediterranean known as the Zanclean Flood. Water rushed down the straits and into the Mediterranean at speeds as high as 40 m/s (90 mph). At its peak, the Zanclean Flood is estimated to have reached rates 1000 times greater than the volumetric flow rate of the Amazon River. 

A similar breach flood occurred in the Black Sea within the past 10,000 years when the Bosporus became unblocked. That flood likely had a devastating impact on Neolithic societies in the area and may be the inspiration for the floods described in the Epic of Gilgamesh and the Bible. (Image credit: BBC, source)

Water spirals are absolutely magnificent

This gif from one of the Slow mo guys videos is extremely fascinating. Water spirals have been of considerable research interest in Fluid Dynamics and as it turns out the gif is only a mode of ejection for the water.

Here are the other modes:

These are dependent on the angular velocity of the sphere The sphere is rotating clockwise with an angular velocity of (a) 84, (b) 137, © 357, and (d) 406 rad/s.

And as one keeps increasing the angular velocity, the stability of the sheet is destroyed and the fluid ejects as small droplets from the equatorial region.


Source: Langley, Kenneth & Maynes, Daniel & Truscott, Tadd. (2015). Eggs and milk: Spinning spheres partially immersed in a liquid bath. Physics of Fluids. 27. 032102. 10.1063/1.4913574.