Tag: measure

Prince Rupert’s Drop – Exploding Glass

By Anupum Pant

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What is it?

At first, a Prince Rupert’s Drop is an interesting yet harmless looking drop of glass with a long tail. It looks like a tadpole: [image]

It is no different from an annoyed person who refuses to let out his resentment – A slightest something might make him explode suddenly, but it isn’t easy to make him let it out. Confused? Read on…

Now, think of a glass drop that has immense amounts of potential energy stored inside it – It explodes (actually implodes) when the tail is disturbed, but it is impossible to hit it hard with a hammer and break it.

How?

A Prince Rupert’s Drop is formed when a drop of molten glass is suddenly dropped into a water bath. This quick cooling, solidifies the surface fast, while the inner part remains molten. Now, glass formed on the surface, being a poor conductor of heat doesn’t allow the inner part to cool quickly. When the inner part starts cooling, it tries to shrink and pulls the surface towards it. As a result, great amount of potential energy gets stored inside, in the form of stresses (stresses are seen using a polarized filter). This stored energy gets released when the tail is disturbed – It explodes into very tiny pieces of glass.

Toughened glass – a stronger variety of glass used in several places – also uses a similar technique to make strengthened glass.

On Wikipedia, a user asked about the possibility of utilizing the energy released from this explosion, being used to fire a bullet from a barrel. An interesting possibility, I must say.

The Name

Prince Rupert of Rhine did not discover the drops, but played a role in bringing them to Britain. He gave them to King Charles II, who in turn delivered them to the Royal Society for scientific study. Prince Rupert’s Drop was a widely known phenomenon among the educated during the 17th century – far more than now.

Watch it being explained better

Probably the best demonstration of this glass drop exploding is right here on the internet. Couple of months back, a YouTuber, Destin (Channel: SmarterEveryDay) posted a video demonstrating the physics behind it. He recorded  the progression of the explosive fracture using a hi-speed camera (at more than 100,000 frames per second) and calculated the speed of the fracture travelling through its tail (~ 1.5 miles per second). I’ve attached it below for you to watch.

10 Fancy Units of Measurement

by Anupum Pant

There exist a few unusual units of measurement which you must have never heard of, or would have never thought of them as units until now. Here is a list of 10 of the many fancy units of measurement.

Note: These units are not official. They’re often used for their humor value or for simplicity’s sake):

1. Car length – It is not a very unusual unit of measurement and is used normally to mention the braking distance of a vehicle. Deriving its length from a typical car’s length, 4 meters is referred as one “car length”. You must have heard one spy advising another spy to keep a 2 car length distance from a vehicle to avoid detection.

2. Nanoacres – A measure of area which is equal to about 4 sq.mm (4.0468564224 sq.mm exactly). It is the area of a single VLSI chip which is square in shape and measures 2 mm on each side. This unit is widely popular as a joke among electronic engineers – who often are known to make quips about VLSI nanoacres having costs in the same range as real acres.

3. Grave – It is a unit that measures mass and equals 1 kilogram or 1000 grams. Grave was set to be the standard unit of mass for the metric system, but it was replaced by kilogram in 1799. [read more about it]

4. Moment – Moment is actually something that was used to measure 90 seconds during the Medieval times. But for modern times, the Hebrew calendar’s definition of moment makes more sense. According to it, a moment is equal to 5/114 of a second or around 0.0438  seconds. [read more]

5. Jiffy – Jiffy is used popularly as an informal time in English. Think of someone saying “I’ll be back in a jiffy”. But, we’ve never thought of it as a unit. Also, every field has a different definition of Jiffy.

  • Early usage – 33.35 picoseconds or the time take by light to travel 1 cm.
  • Electronics – 1/50th or 1/60th of a second, depending on the AC power supply frequency.
  • Computing – Typically anything between 1 millisecond to 10 millisecond. Commonly: 10 ms.
  • Animation – The time interval between each frame of a dot GIF file or 1/100th of a second or 10 ms.
  • Physics/Chemistry – Time taken by light to travel 1 Fermi or 3X10^-24 seconds.

6. Dog Year – Based on a popular myth that dog’s age can be calculated in human years by multiplying it with 7. So, a single Dog year comes to around 52 days (365/7 – Days in a human year divided by 7)

7. A Bible – Used as measure of digital data volumes. It is like measuring the size of a disk in number of movies it can fit which I used in this article. A single Bible in uncompressed 8-bits, has around 4.5 million characters and 150 of them can be stored in a single CD. Hence, a bible can be measured to be approximately equal to 4.67 Megabytes. Similarly,  Encyclopedia Britannica and Library of Congress are used to represent much larger data volumes.

8.  Kardashian – Yes, it is named after the 72 day marriage of  Kim Kardashian to Kris Humphries. Of course, it measures 72 days of marriage. So, a 25 year marriage would amount to around 126.7 Kardashians.

9. Wheaton – Used to measure the number of twitter followers relative to the popular celebrity Will Wheaton. This became a standard when he had 0.5 million Twitter followers. Today, Will Wheaton himself has 4.88 Wheatons. I, for instance, with 210 followers, have about 0.00042 Wheatons.

10. Warhol – Derived from the widely used expression coined by Andy Warhol – “15 minutes of fame” – 1 Warhol measures exactly what you’d expect it to – 15 minutes of fame. Yes, it measures the amount of fame.
Consequently, 1 kilowarhol is equal to 15,000 minutes of fame or 10.42 days and 1 megawarhol measures 15 million minutes of fame or about 28.5 years.

 

How Loud Can it Get?

by Anupum Pant

Wives and moms can scream really well. But is it loud enough to inflict physical pain? Can sounds get louder than a nuclear bomb? How much damage can a loud sound cause? How about mass extinction? Read on to find out the answers.

What is sound?

Sound, as most of us know is a longitudinal, mechanical wave. That means, it is just a series of pressure changes [compressions and rarefactions] in a particular medium. So, the property of sound is as good as the medium it uses to travel. For instance, sound cannot travel in a vacuum due to the absence of any medium, but it can travel much faster in solids than in air. That is the reason you can’t hear someone talking in space (yes, movies that show loud explosions in space, lie). Also, the faster speed of sound in steel rails is exactly the reason why, you can tell a train is approaching, if you stick your ears to the rails (do not try this on electric rails).

Two of the fundamental parameters that describe a sound wave in numbers are pitch and amplitude. Pitch is measured in hertz – we’ll talk about it some other day. But, the amplitude of a sound wave determines how powerful it is; greater the amplitude, louder the sound. The loudness of sound is measured in Decibels (abbreviated dB).

More about decibel scale

Like most other linear scales, Decibel isn’t as easy to understand. A 10 point rise in the dB scale can be visualized as a 10 times increase in the loudness. Adding dB levels of different sound sources also doesn’t really work, the calculation is much more complicated; the resultant loudness depends on the coherency of the source [See this decibel addition applet]. Also, the perceived loudness is obviously lesser as you go away from the sound. Normally, a decibel scale ranging from 0 dB to 130 dB is enough for measuring the loudness of most things. But, things can get louder…much louder.

To get an idea of the decibel scale: 10 dB is 10 times more powerful than 0 dB, not 10 points greater. Similarly, 20 dB is 100 times more powerful and 140 dB is 100,000,000,000,000 times more powerful than a o dB sound.

0 dB is the loudness of near silence (a mosquito 10 feet away), while 120 dB is the loudness of a loud car horn heard from 1 meter away. Humans can hear sounds starting from 0 dB. But it can be quieter than 0 dB [the world’s quietest room]. It measures record setting -9 dB and can literally drive you crazy. In fact, the longest someone stayed in that room was for 45 minutes.
On the upper side of dB spectrum, a whisper is around 15 dB, conversations range from 40 – 60 dB and a jet engine measures 130 dB on the decibel scale. Like I said before, the perceived loudness depends on your ear’s distance from the source, so the loudness of a lawnmower can range anything from 90 dB to as much as 110 dB if you stand 3 feet away from it. [see the Decibel chart]

90 Decibels or a sound as loud as only a raised voice can cause gradual hearing loss (Refer to the hearing safety chart here). While 140 dB can cause physical pain. After 150 dB (firecracker) sounds can be felt in the form of shock waves. The pressure difference they cause in the medium can actually be felt by your body.

Beyond Decibels

Since the loudness depends on the medium, the maximum loudness a medium can propagate is dependent on its density. Our atmosphere can do nothing more than 190 dB, that, by the way, is enough to make you deaf or cause death. Sounds in water can get louder. A pistol shrimp is able to create a 200+ dB sound at 97 km/h to stun or kill its prey by snapping claws really fast. This is a very short lived pulse which doesn’t carry enough energy to do us any harm.

For events like the Saturn V launch, volcanic explosion, nuclear bomb explosion, earthquakes, star-quakes the concept of sound doesn’t really apply anymore. They are measured in terms of the shock wave they produce using the Richter scale. On this scale, 9 means total destruction (8.2 was measured during the explosion of the largest bomb ever, Tsar Bomba). An earthquake or earthly event measuring 10 has never been observed.

However, in the universe beyond earth, the starquake on the magnetar SGR 1806-20 registered 22.8 to 32 on the Richter scale. The magnetar released more energy in one-tenth of a second than our sun has released in 100,000 years. An event which thankfully took place 50,000 light-years away from earth. Had it been even 10 light-years away, the energy released would have wiped off life on earth. [read this BBC article for more information on this event]