Physics of an ordinary water droplet

The video is of an effect known in fluid dynamics as the coalescence cascade, which can be observed (provided you have access to a video camera with a sufficiently high frame rate) when a drop of liquid is deposited very gently onto the surface of a layer of the same liquid.

When a droplet impacts a pool at low speed, a layer of air trapped beneath the droplet can often prevent it from immediately coalescing into the pool. As that air layer drains away, surface tension pulls some of the droplet’s mass into the pool while a smaller droplet is ejected. When it bounces off the surface of the water, the process is repeated and the droplet grows smaller and smaller until surface tension is able to completely absorb it into the pool.

 

Pretty awesome, right? In the video shown up top, the effect manages to repeat itself four times (in what scientists who study fluid mechanics call “events”) before the viscous properties of the resting pool become too strong for the smallest drops to withstand coalescing completely. MIT’s John Bush claims to have observed as many as seven such events in a row.

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Aerogel : See-through, Strong as Steel & Ligher than Air

See-through, Strong as Steel & Ligher than Air

Despite its incredibly low density, aerogel is one of the most powerful materials on the planet. It can support thousands of times its own weight, block out intense heat, cold and sound – yet it is 1,000 times less dense than glass, nearly as transparent and is composed of 99.8% air. The lowest-density silica-based aerogels are even lighter than air.

 

A 2.5 kg brick is supported by a piece of aerogel weighing only 2 grams.

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There Is Such Thing As Dry Water

Powdered material called "dry water" could provide a new way to store carbon dioxide in an effort to fight global warming. (Credit: Ben Carter)

Don’t ask me what voodoo they used but scientists have created dry water. Well, they originally invented it back in 1968 but they’ve recently re-discovered it and this time, found an actual use for it.

First, dry water, how does that even make sense? Ben Carter, Ph.D, the researcher, explains:

[It’s] known as “dry water” because it consists of 95 percent water and yet is a dry powder. Each powder particle contains a water droplet surrounded by modified silica, the stuff that makes up ordinary beach sand. The silica coating prevents the water droplets from combining and turning back into a liquid. The result is a fine powder that can slurp up gases, which chemically combine with the water molecules to form what chemists term a hydrate.

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