Category Archives: Physics

They're All Named Bob

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Here’s a pendulum demonstration that was part of an Exploratorium exhibit in the atrium of the Hyatt where I was attending a frequency & timing conference this past week. The bobs all start off in phase but since the period (or frequency) of a pendulum depends on \(sqrt{L} \) (or its inverse), the relative phases rapidly diverge. The bobs occasionally hit a condition that looks less chaotic, such as the slightly-out-of-phase S shape, and the condition where alternate bobs are 180º out of phase. They then go back to the “S” before briefly all being in phase again. That occurs when they have all undergone an integral number of oscillations, with each one having undergone one more cycle as its neighbor as you move from the front to the back (long to short)

Here’s another video, via @JenLucPiquant with even more bobs.

It's Ungodly

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The Dangerously Clean Water Used To Make Your iPhone

The ordinary person thinks of reverse-osmosis as taking “everything” out of water. RO is the process you use to turn ocean water into crystalline drinking water. And in human terms, RO does take most everything out of the water.
But for semiconductors, RO water isn’t even close. Ultra-pure water requires 12 filtration steps beyond RO. (For those of a technical bent, the final filter in making UPW has pores that are 20 nanometers wide.
…
Water is a good cleaner because it is a good solvent–the so-called “universal solvent,” excellent at dissolving all kinds of things. UPW is particularly “hungry,” in solvent terms, because it starts so clean. That’s why it is so valuable for washing semiconductors.
It’s also why it’s not safe to drink. A single glass of UPW wouldn’t hurt you. But even that one glass of water would instantly start leeching valuable minerals back out of your body.

Old McDonald Had a Scintillator

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Here a scope, there a cope, everywhere a spinthariscope

The spinthariscope — see atoms decay before your eyes!

A small radioactive source (the details of which we will discuss later) emits alpha particles that collide with a zinc sulfide (ZnS) screen. This screen gives off flashes of light (called scintillations) at the places the alpha particles hit. These minute flashes are magnified by a simple lens and can be viewed through the eyepiece. Every flash the viewer sees is the trace of a single atomic nuclear decay. By adjusting the bottom screw, one can effectively increase or decrease the rate at which alpha particles hit the screen, transforming a flood of particles into a trickle, or vice versa.

This is a pretty neat effect, and is worth blogging about in itself, but the spinthariscope also has historical significance: it was the first device invented that is able to detect individual radioactive particles, a precursor to the Geiger counter!

I got one, too, though mine lacks the adjustment screw. Neat flashes of light, though, as long as I am not wearing my glasses — I need to get my eye right up to the eyepiece. Unfortunately the flashes have proven too dim to capture on a camera. The low-light viewer we have in the lab didn’t help; it’s geared more to being sensitive in the IR (and shifting it to green, which helps the eye more than the camera) than to amplifying raw signals.

Coffee, Julie?

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Pretty neat: Coffee Joulies

Coffee Joulies are miniature thermodynamic heat storage devices. They cool your coffee by absorbing excess thermal energy when it is too hot. This energy is stored inside the Joulies. When your coffee reaches the right temperature, the Joulies slowly release this stored energy, keeping your coffee at the right temperature.

From their kickstarter page:

This amazing feat of thermodynamics happens thanks to a special non-toxic material sealed within the polished stainless steel shell. This material is designed to melt at 140 degrees Fahrenheit, and absorbs a lot of energy as it melts. This is how Joulies cool your coffee down three times faster than normal. Once it reaches this temperature, the special material begins to solidify again, releasing the energy it stored when it melted. This is how Joulies keep your coffee warm twice as long.

The better insulated your cup, the better Coffee Joulies work. Simply using a lid goes a long way. This is because less heat is lost to the environment, and more is stored within the Joulies themselves.

That energy is, of course, the enthalpy of fusion. Think of an ice cube: the ice absorbs energy as it melts, maintaining the same temperature but cooling the beverage down. What these people have done is use a material that melts at a convenient temperature for hot beverages and that takes advantage of the reverse process that happens in the freezer — the transition back to a solid, releasing that energy, at the melting point.

The site doesn’t specify the material, but the various forms of paraffin wax have melting points around 140 ºF with large heat capacities and enthalpies. Which would be pretty much what you want to use.

(The bit about the lid and/or insulation keeping things warm works without the Joulies, too)

It's Why Men Like to Barbecue

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Men Will Cook If Danger Is Involved. -Rita Rudner.

Evil Mad Scientist Laboratories: Cooking hot dogs via electrocution

Disclaimerzilla: While we could give you lots of warnings about all the different dangers involved and how to possibly skirt them, the simple truth is that this just isn’t safe. If you are foolish enough to attempt this, you will have to deal with pointy things, raw electricity out of the wall, hot steam, and the possibility of fire. If that isn’t enough, and you succeed, you are still faced with the possibility of having to eat a hot dog. In summary: do not, under any circumstances, cook hot dogs this way.

Note: the LEDs are not edible.

h/t to J

In Space, No One Can Hear You Scream, "Eureka!"

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Put two objects of unequal density on a balance, such that the scale reads that they have equal mass. Then evacuate the air.

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Lesson: air creates buoyancy, too. The larger object displaces more air, so it actually has more mass, but also has slightly more buoyancy.

h/t to michel

Water Doesn't Put Out This Fire

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Fire ants assemble into living waterproof rafts

What happens when you dump 8,000 fire ants into a tray of water? Nathan Mlot from the Georgia Institute of Technology wanted to find out. Mlot scooped the ants into a beaker, swirled it around to roll them into a ball, and decanted them into a half-filled tray.

Two can
can
a toucan but

You can’t
decant
an ant

(sorry; I seem to have contracted poetry. A case of bad poetry.)

 

Here’s the repeated attempts to push the ant-raft into the water

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Snake-Oil Science: The Romance of Empty Symbolism

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Quantum Entanglement: A New Way to Be Married

In other words, when two or more particles are entangled, they behave as if they were one and the same, and any change to one instantaneously and identically changes those entangled with it even if they’re a universe apart. “Just try doing that in a marriage contract,” Mr. Keats says.

That’s quoted text but there’s no link to the source, which led me to Google and find a press release which says something similar

According to quantum mechanics, when two or more particles are entangled, they behave as if they were one and the same. Any change to one instantaneously and identically changes those entangled with it even if they’re a universe apart.

Unfortunately, Mr. Keats is wrong. This is the oft-reperated canard of the pop-sci version of quantum entanglement. Any measurement of one will tell you the state of the other, but that breaks the entanglement, and it means you cannot know the state of the particle beforehand. So this gesture means having to forget who you are. As soon as you remember, or someone recognizes you, that’s gone.

What the quote should really say is

According to people who don’t understand quantum mechanics, when two or more particles are entangled, they behave as if they were one and the same. Any change to one instantaneously and identically changes those entangled with it even if they’re a universe apart. In real quantum physics, this isn’t the case.

You can still turn this into a romantic gesture, but please, don’t mangle the science to do so.