Added: 4 years ago
From: psidot
Views: 36,193
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  • how many times do you tap the bottom of the cup before it breaks, spewing hot coffee all over the place?

  • Not sure if the word allaso is the ancient Greek word for change but the current/modernversion is spelled allakso. I wonder who came up with this word

  • @spolida  allakso is how it sounds when its said by a greek

  • Holy shit, I've been wondering about this for years. HOWEVER I always notice the effect when I clink the the rim of the cup with my spoon, and there are no dissolving crystals in the tea. I've always assumed that the effect was caused by the tea (having been circularly stirred) gradually losing its angular momentum and therefor not climbing so high on the sides of the cup. I'm too lazy but somebody else immediately investigate this before it's too late! The future of humanity is at stake!

  • but why does it happen?!...

  • Thats why my cup exploded, hit the resonance. :)

  • Does it HAVE to be instant coffee?

  • Well someone went to Yale

  • A ver si entiendo tu malestar, resulta que a medida que golpeas mas fuerte la taza, su sonido aumenta. No creés que esa prueba es una estupidez y que solo es para perder el tiempo? Creo que te puedo dar otra prueba similar, llamala el efecto Pablo. Golpeate los nudillos contra la mesa cada vez mas fuerte y vas a ver que cada vez te duelen mas. Si querés patentala.

  • wow

  • flaco no cazas ni media vos, si te pones a ver videos de efectos fisicos no esperes ver un capitulo de los caballeros del zodiaco ni te imaginas la cantidad de fisicos q habran estudiado este fenomeno, aparte que tan importante sera TU tiempo para cualquiera! seguro q lo gastas a pura paja jajaj

  • To complicate matters, if you stir the liquid, the pitch gets low again and starts the rise all over again. The pitch rise continues after the rotation of the liquid appears to have stopped. The stirring trick will work repeatedly. Any explanation has to take this into account. You'd think that the dissolving and release of bubbles would only work for a short time.

  • The vibration of the tapping allows molecules to interlock thus changing its resonant characteristics. This happens without tapping with a solution of alcohol and water (the interlocks). Stirring the coffee unlocks the molecules lowering the resonant frequency. Very tight crystals generally have higher resonant frequencies.

  • try this...just after pour hot water to a glass with coffee powder, stirr it then drink it till finish...try to slap your stomach at regular interval..sounds nice too..aaaaarghhhh!

  • @BreakFreeze stupid u are

  • referrin to the more info, why would you wanna put salt in your pint

  • After a while, the dissolving crystals in the powder have finished dissolving and the change in pitch stops. As crystals of sugar, salt and other substances dissolve, they form ionic lattices in the liquid as the concentration changes. The effect changes the speed of sound in a liquid.. which changes the resonance, thus changing the pitch.

  • i wonder what would happen if you did for an hour

  • My coffee cup does this with standard brewed coffee. i suspect it would happen with hot water and the ceramic is undergoing strress as it heats.

  • Exactly.

  • it is a good song. i agree

  • i believe its to do with the speed of sound in the liquid changing as the new substance is absorbed into the liquid. and the % coffee in this case increases, the speed of sound changes through that medium.

  • ahhh... speed of sound is good song.

  • Nice water boiler! haha and very interesting indeed!

  • Speed of sound in the liquid changing as the number of small air bubbles changes?

  • thats quite interesting

  • My guess is that the pitch changes due to the amount of dissolved versus undissolved solids in the liquid.

  • IT IS AMAZING!

  • lol

  • the ending :D

  • I've observed this effect before with othere stuff like cold beverages, as well as hot.

    I wonder if the effect is caused by the molecules of the container speeding up, or slowing down with heat, and cold applied to them.

    Fascinating.

    Did I leave the theremin on?

  • I think the sound that is being provoked by tapping the spoon against the cup could be in a way acknowledging the slowing down/speeding up of the molecules

  • that is acually really cool - I just subscribed because your videos are awesome :p

  • lol if that was me that cup would be broken

  • Cool. I wonder what effects the interplay between this phenomenon and doing the resonating of a crystal glass lip thing could do if done at the same time.

  • Noticed this for years. You DONT have to tap the bottom of the cup. You will notice the same sound change if the spoon rubs against the inside of the cup. I am sure the pitch increases as the cup absorbs heat from the hot liquid slightly.

  • agree...due to the expansion of the ceramic object

  • "agree...due to the expansion of the ceramic object"

    Why would the pitch of the sound increase when the ceramic cup gets warmer and expands?

    Have you read the infobox? The effect is said to occur with cold beer, too.

    Read tr5939's comment. I don't know if he hit the nail on the haid, but his theory seems to be more though-out.

  • Just tried it out for myself. Of course the pitch did not change when there were only hot water in the cup. For the allassonic effect to occur, I had to add cappuccino powder. I also could change the pitch of the sound back to its initial, low level by stirring again.

    Now tr5939's bubble theory seems to make even more sense to me. It would also explain the 'beer and salt' experiment.

  • "I am sure the pitch increases as the cup absorbs heat from the hot liquid"

    Why would the pitch of the sound increase when the ceramic cup gets warmer?

    Have you read the infobox? The effect is said to occur with cold beer, too.

    Read tr5939's comment. I don't know if he hit the nail on the haid, but his theory seems to be more though-out.

  • Just tried it out for myself. Of course the pitch did not change when there were only hot water in the cup. For the allassonic effect to occur, I had to add cappuccino powder. I also could change the pitch of the sound back to its initial, low level by stirring again.

    Now tr5939's bubble theory seems to make even more sense to me. It would also explain the 'beer and salt' experiment.

  • oh... that happens all the time. never actually truly noticed it before though.

    interesting.

  • either that or it's the bottom of the cup breaking off

  • IMHO:

    the powder traps small bubbles of air in the liquid. The bubbles start off well distributed and small, and with time rise to the top and coalesce into bigger bubbles and burst at the top.

    Air bubbles slow the (apparent) speed of sound through water (by reflection, less transmission and a lower inherent mach speed). So when you tap the cup, a pulse of sound goes very quickly up and down the height of the cup. These oscillations are at a frequency that we hear as a sound pitch.

  • As the bubbles settle, the apparent speed of sound of the liquid increases, tending to the speed in pure water, so the pulse can do more oscillations per second = Hz = higher pitch.

    Also, if you put more liquid in the cup, the length of water the pulse has to travel increases, so the number of oscillations per second = Hz decreases. This accounts for musical water glasses (like a xylophone), pitched by varying amounts of water.

  • okay...so....what's happening though?

  • the pitch in the cup is rising... amazing

  • google "standing waves"

  • why does it do that?

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