Dancing Drops of Water and Dipping Hands in Molten Metal

By Anupum Pant

When you sprinkle water on a hot pan, you’ll find that the droplets start dancing on the surface, as if there was no friction at all. From far, this effect looks a lot like water droplets on a lotus leaf (a super-hydrophobic surface). But, the physics behind this phenomenon is completely different. Read on to find out what is the mystery behind these dancing drops of water.

The Leidenfrost Effect

Why does this happen?
Unlike the drops on a lotus leaf, this happens at a particular temperature for a specific liquid. Different kinds of liquids display this effect at different temperatures.
For water, at a temperature when a small amount of water in contact with the pan gets heated enough to form a thin-film of vapor below the drop, water is no longer stuck on the pan (water sticks to some surfaces due to low surface tension). The drop has a thin vapor film below it which enables the drop to move around on the film. The formation of this vapor film is a continuous process, till the whole drop turns into water, one film at a time. This is called the Leidenfrost Effect.

Some liquids like liquid Nitrogen are extremely cold. At normal room temperature, they start boiling. A normal room’s floor is like a hot pan for liquid Nitrogen. So, it forms these dancing drops on a floor which is just at room temperature. You can try this yourself – If you can find some liquid Nitrogen, you can simply drop it on the floor and watch droplets moving effortlessly. They won’t stop moving!

Dipping hands in Liquid Nitrogen

The temperature of liquid Nitrogen is around -195 degree centigrade. It is one of the coldest substances and is used with extreme caution in industries and laboratories. If it touches you, your skin can easily get burnt. Yes, burnt – at extremely low temperature. It could probably also make the dipped limb useless for life. So, you shouldn’t try stuff with liquid Nitrogen at home.

But, it turns out, you can safely dip your hand in it for a small amount of time and return unharmed. Thanks to the Leidenfrost effect. Our hot-pan like hand – for cold liquid Nitrogen – makes a thin film of vaporized Nitrogen around the whole hand. This film, protects our skin from the ill effects of extremely cold temperatures. Still, there is no reason for you to try this. It has been done already.

The crazy duo from Myth Busters tried this with molten lead. It worked!  They, of course had to wet the finger with water – for the vapor film formation.

Water flowing uphill

Recently, an undergraduate research student group from the University of Bath found out a way to manipulate the movement of water on a specially designed surface, using this phenomenon. They found that machining ridges on the surface (and heating it) would make the thin vapor films under water droplets move in such a way, that they could use it to propel drops against gravity. They were able to demonstrate this by showing water moving uphill on a slope. It is enthralling to see it for yourself. I’ve attached their video below.

Tardigrades – Toughest Creatures on Earth

By Anupum Pant

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So, if you think elephants or cockroaches are tough, that could be because you probably haven’t heard about these amazing creatures called Tardigrades (picture).

What are Tardigrades?

Tardigrades, also known as moss piglets or waterbears, are oddly cute little animals that live in water and feed on moss. Their size ranges from 0.1 mm to 1.5 mm and they have eight legs (they walk like bears). The most extreme thing about these extremophiles is that they can survive almost anything (actually, they kind of die for a while with an option to come back to life later). Here is a list of things Tardigrades can survive. They can:

  • Survive without water and food for 10 years.
  • Waddle away in the vacuüm of space (for 10 days & get exposed UV radiation), come back and walk around as if nothing happened.
  • Survive 1000 times more radiation that would kill an elephant.
  • Live through extremely low temperatures (almost absolute zero) or high temperatures (~150 degree Centigrade)
  • Repair their own DNA after getting exposed to lethal amounts of radiation.
  • Survive pressures of about 300 Jumbo jets stacked on a person. (6 times more than the deepest ocean trenches)

Scientists love them

People at NASA and the European Space Agency love doing tests on them because they think, Tardigrades can help them understand the origin of life on earth (probably by supporting Panspermia). Also, scientists want to find out more about their extreme capabilities. If you ask them, if these things are aliens, they’ll tell you – “Probably not”

[Learn more about Tardigrades]

The Red Rain of Kerala

By Anupum Pant

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In the year 2001, between 25th July and 25th September, people from the Indian state of Kerela (Kottayam and Idukki districts) experienced a bizarre oddity – The Red Rain of Kerala. Sporadic heavy downpours of mysteriously colored water left the people of Kerala dazed. More recently, red rains were also seen in parts of Sri Lanka between 15th November and 27th December, 2012.

Yellow, Black and Green rains have also been reported several times since 1896.

Red Rain of Kerala – Studies

A study conducted in India showed that the rain was colored because these raindrops contained millions of spherical and oval red particles which had an internal structure. These things looked like biological cells. Initially, when scientists weren’t able to confirm the existence of DNA (a fact which has baffled scientists) in them, in spite of an internal structure present in the cells, some started claiming that the origin of these red particles was extraterrestrial, possibly, coming from an exploded meteor.

Later the mystery was solved, the presence of DNA was confirmed and a study, destroying popular media claims, concluded that the red rain of Kerala had been colored due to airborne spores originating from a type of algae. There was nothing alien about it.

The unusual color of the rain was due to the presence of a unicellular micro-organism belonging to Kingdom Protista, of the Phylum Euglenozoa, known as Trachelomonas. Trachelomonas was the main cause of reddish downpours in other regions of the world as well.

[Source: The Red Rain of Kerala]