Tag: reason

Screaming Coin and a Singing Spoon

By Anupum Pant

Dry ice, or Cardice – as British researchers call it, is a solid form of carbon dioxide. When carbon dioxide is cooled below temperatures of -78.5 degrees centigrade, the gas gets directly frozen into a solid form. -78.5 degrees centigrade is extremely cold, and handling dry ice without proper protection can be very dangerous – could cause frostbite / burns. The point being, it’s extremely cold.

Since it’s too cold compared to something at room temperature, even everyday objects at room temperature can make it vaporize. A simple metal coin at room temperature would feel like a hot pan to dry ice. So, when a coin is shoved into a piece of dry ice, it creates a funny sound, just like water would, on a very hot pan; or, you could say the sound be very much like a hot metal ball being dropped into a cold bath of water (the temperature difference being much less in this case, of course).

This is how it works: The metal piece at room temperature vaporizes some amount of carbon dioxide from the piece of dry ice when it comes in contact. There’s a pressure difference (Bernoulli’s principle) associated with this process and the gas tries to escape. This makes the metal vibrate very fast, creating that funny sound. This is how it sounds…

Metals work best because they have a good thermal conductivity. For the sake of trying it out yourself, if you have a piece of dry ice lying unused, you could dip a spoon in hot water and make it touch the piece of dry ice. A slightly warmer spoon will probably give you a better effect. And then the spoon will be singing…

The Natural Segmented Sleep

By Anupum Pant

Background

The light bulb changed everything. Before it came, when the only practical sources of artificial light were candles & lamps, people did not often use candles to stay awake at night. These sources of artificial light costed a lot more per lumen hour. They were not always used. They were used only when artificial light was totally necessary. Normally, as the sun went down, people preferred sleeping. As bulbs came, they transformed the way we slept. Or, so argued the historian A. Roger Ekirch.

In his detailed published anthropological work – At Day’s Close: Night in Times Past – he mentions that the eight-hour single block of sleep is a recent change in our sleeping schedule. For many many years more than we’ve slept for eight hours in the night, our ancestors had practised a very different kind of sleep schedule which became the natural way of sleeping for humans. It was a segmented sleep.

The schedule went like this…

When the sun went down, there was more or less no artificial source of light. Due to this, our ancestors could do nothing useful. Bored with inactivity, they slept. Then somewhere in the mid-night, they woke up. For an hour or so, they remained awake and went back to sleep again till the morning.

The time for which these people remained awake, was probably the most relaxing and most calm time of their lives. Due to increased levels of pituitary hormone prolactin, people felt a lot at peace during this hour. During this time, people liked involving themselves in some kind of activity. Some preferred reading, others wrote. Some smoked, others visited their friends. And so on… The point is, people found themselves replenished during this time. It was apparently blissful.

This pattern of sleep became a natural way for us humans. Turns out, the eight-hour block of sleep is not the way we always used to sleep!

This sleep pattern has been observed to come back to today’s humans when they were completely deprived of any artificial light. This can be seen in the famous experiments of a psychiatrist, Thomas Wehr.

End

That waking hour of bliss – a fact of life before the industrial revolution came – was probably a period which I feel, needs to come back to cure the modern world’s rising anxiety, stress, depression, alcoholism and drug abuse.

Some scientists believe that if you give your bodies a chance, they’d go back to a segmented sleep pattern. This is also bolstered by Wehr’s experiments. While others prescribe you sleeping pills if you tell them you wake up at night for an hour or so.

Just for the record, I’m writing this at 2:30 AM. I just woke up, and I’m off to sleep again.

[Read more]

[Mastering Biphasic sleep] A detailed blogpost on the experience by Jayson Feltner…

Weight of the Copper Tube with a Falling Magnet

By Anupum Pant

Remember I talked about Copper tube and a magnet a couple of days back? Turns out the same happens when you use an aluminium tube too. In short, a magnet (a strong one – neodymium magnet) when dropped into an aluminium or copper pipe falls very slowly, as if gravity stops acting on it.

It is due to the opposing magnetic forces generated by the electric field which is in turn generated by the magnetic field of the magnet (more in the link above).

That said, have you wondered what happens to the weight of the tube when the magnet is falling? Does it increase, decrease or remain the same? Just give it a guess and watch the following video.

The Royal Institution Explains:

Hit like if you learnt something today.

Did a Teacher Ever Scold You for Yawning in Class?

By Anupum Pant

Background

I always found school interesting. I wasn’t one of those kids who felt bored and sleepy during the class. And yet, during the classes, I yawned often. I remember being sent out of the class a couple of times because I had yawned. This happened again, and again at college. However, lecturers never cared to send me out in college. And then there were no more classes.

Then, when I started working, at a meeting one day, a friend yawned in a board room where the head of the company was present. The head saw this happen. Being a fresher, the guy got scolded very badly by the head. I felt sad for him. I knew, he wasn’t really sleepy when he yawned; clearly he wasn’t bored too. There could have been a different reason for it. The head should have known this.

Yawning is universally considered as a sign of sleepiness or boredom. I however, am pretty sure that a yawn doesn’t necessarily comes when someone is bored or sleepy. I do have a theory to back my belief that I discuss below. Also, yawning has a lot to do with empathy too. But that is not what I’m discussing today. To educate yourself about the empathy side of it, you could watch the following video.

No one knows for sure why we yawn. In addition to that there might be several different reasons that could explain why we yawn. Like a couple of reasons that explain why we sleep (may be there are more). Most definitely, it isn’t a single reason.

A study shows that yawning could be the body’s way of cooling down the brain and it makes perfect sense to me!

The Study

Scientists from the Princeton University say that people yawn more during the winters. That is because during the winter the air outside is colder and the body knows that. So, it makes us yawn to take in the cold air to cool the brain by exchanging heat.

There’s also this other explanation which breaks down the process of yawning into two parts – 1. stretching of your jaw muscles and 2. air entering your mouth after you do that.

When you stretch the jaw muscles in the first step, blood flow increases in your face, brain and sinus area. Now the cool air enters and cools down the blood vessels in the nasal cavity and sinus area. These blood vessels in turn cool the blood and circulate cooler blood to your brain, to cool it down.

Teacher’s theory

Now, it’s a well-known human rhythm that bodies get heated up just before we fall asleep. As a result, we yawn more. So, teachers were not completely wrong. However, sleep is not the direct reason. The reason we yawn is because the brain gets heated up, and it may as well get heated up due to other reasons; not always due to sleepiness or tiredness. Plus the yawn tries to correct the heated-sleepy-brain by circulating cooler blood.

The body does this to cool down the over-heated brain – which obviously gets heated due to extra information processing – like a computer processor. Why would the brain heat up when I’m not actively processing information better. So, yawning doesn’t mean I’m bored, or I’m not actively listening to the teacher when they’re speaking. Teachers need to know this.

Even if yawning is a sign of boredom to some extent. A yawn actually helps you cool down and helps you to process information better. So, teachers should be happy when you yawn in their class. You are trying to be a better listener than people who aren’t yawning in the class!

Hit like if you learnt something interesting today.

The Rainbow Coloured Lake – Grand Prismatic Spring

By Anupum Pant

Of all the “cool” places we have here on earth, lakes and other water bodies fascinate me the most. This is probably the reason I keep stumbling upon some of the most amazing lakes over and over. In the past I’ve written about the Taal lake and the bleeding lake of Antarctica. I have several others in mind, but this is the one I’ve picked for today, and it isn’t “cool” – The rainbow coloured lake.

Lying amidst the colourful geysers and hot springs of Yellowstone National park, located in the state of Wyoming, is a lake where you’ll see colours ranging from brilliant yellow, orange, red, green and of course blue. Here is what it looks like…

The lake is called the grand prismatic spring and it is the largest hot spring in the US. The water there is hot enough to burn you. And yet…

The hot spring, is home to different kinds of tiny living creatures. Organisms called thermophiles have learnt to thrive in the abnormally hot place. In fact, these creatures depend so much on the heat that they can’t live away from the hot water.

What makes it coloured?

The lake is coloured, yes. But what causes these bright vivid colours? Is it because there is something in the air around it, or is it due to a industrial chemicals leaking into the lake, or is it due to these organisms? Whatever causes the lake to appear coloured, that too colours appearing in the same order like they would be seen on a rainbow, I wanted to know.

Turns out, it isn’t just the lake that is coloured. The steam that arises from the hot water comes in different colours too!

The orange and other non-green/blue colours which appear there the most after blue are due to a multi-layered sheet of microorganisms that thrive in the lake. These are pigmented. The main pigment is chlorophyll (the same thing which helps the plants make food). But chlorophyll is green. So there are some other yellow, red and orange coloured pigments called Carotenoids, that protect the chlorophyll when the sunlight is bright enough to damage it.

The colour of the part of lake is a function of, amount of Carotenoids  present with chlorophyll. More the Carotenoid, more colours you’ll see. A greater ratio of cartenoids to protect the chlorophyll during summers is the reason why the lake appears not-so-coloured during winters and vividly coloured during the summers. So, it isn’t the variety of microorganisms or chemicals or atmospheric conditions that colour the lake, the colour is due to the different mix of chlorophyll and carotenoids at different patches of the lake at different times of the year.

The best time to visit this place would thus be the summer season!

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Problem with Facebook – On Facebook Everybody Loses

By Anupum Pant

I had to say this a couple of weeks back. But, now I think, I’ve gravely been irritated by Facebook to let it out. So here goes a post on how Facebook is repeatedly trying to make you confirm your own  pre-conceived notions and is basically making you an ignorant person everyday, is hurting page owners, and they are doing all of this to make short-term money for themselves. It is evil. That, is the problem with Facebook.

Almost every good thing you want to see is hidden from you on Facebook

Okay, let us start with my Facebook page. I know it is a small one, with just 446 likes (as of today). That said, I can tell you one thing for sure, I never forced any one of these people to like my page, nor have I ever advertised my page on Facebook to amass likes. All, or may be most of the people who like my page wished to clearly subscribe to my content and my views. Clearly, they wanted to be updated on the things I was posting. But Facebook tells me, that isn’t happening, unless I pay them the money.

Now take a minute to look at the screenshot below:

Facebook page insights
Look at the total reach.

See the first post in that list. Of all the 446 people who’ve subscribed to the page, this appeared on only 15 news feeds. Moreover, the chances are high that all of these 15 people must have not even scrolled down to see the loaded post. So, probably 10 of the 15 loads were just useless loads. 5 of them who actually saw the post, decided (probably subconsciously) to not engage – that is understandable. Even if all the 15 people did see this post, how is that fair? Continue reading Problem with Facebook – On Facebook Everybody Loses

Water vs. Red-Hot Nickel Ball

By Anupum Pant

Let me just not say anything before I make you watch this video today:

In the video, a Nickel ball is heated using a torch and is dropped into a bowl of water. As the hot ball touches water for the first time, it makes a certain “Ping” sound. It enters the water and gets covered in a bubble sort of thing. As it cools and the bubble is lost, that “ping” sound comes back again. The “Ping” repeats several times and is fun to hear a metal ball do that!

So much fun that the good guys on Reddit even made a couple of ringtones out of it. Download the longer one here. And the shorter one for notifications here.

Why does it form a Bubble cover?

This happens because the metal that is dropped into water is extremely hot and makes the water around it vaporize. The vapor formed around the ball acts as an insulator and doesn’t let the water touch the metal ball. This is the same effect that lets dip your hand in molten lead or Liquid Nitrogen without getting harmed by it. The same thing happens when you drop water on a hot pan – it dances.

This effect is called the Leidenfrost effect and I’ve covered it in an article before…

I’m not sure what exactly causes the “Ping” sound. If you know or have any theories, please tell me in the comments below.

CrashCourse in Quenching

Well, if I’d have wished to piss you off with jargon, I’d have said: “You just watched a hot Nickel ball being quenched in water”

Yes, quenching. Quenching is the name for making a hot metal cool very quickly. It is pretty interesting to know why some one would, with great effort, heat a metal, and then choose to drop it in water to cool off!
Cooling a hot piece of metal very quickly makes it extremely hard. So hard, that the same process is used to make the hard edges of swords that don’t get damaged even if they are used to cut metal!

There is so much more I wanted to write about the process, but I feel this isn’t the right place for it. Let me leave it for some other day.

Gravity Defying Chain of Beads

By Anupum Pant

Chain of Beads

Suppose, you have a neat pile of a really long chain of beads in a beaker (Newton’s beads) and you give one end of the beads a tug and let it drop on the floor, what do you think will happen?

Steve Mould, a YouTuber, did the same with a 8000 bead chain. It was 50 meter long chain of beads placed neatly in a container. Then, after he tugged it out and let it drop, the chain mysteriously formed an arc above the beaker and continued to self-siphon away till the end. Just like a water-siphon.

Watch it in video to see what happens. [Video]

What keeps it going?

To figure out what was actually going on here and to understand the exact physics of it, a group of physicists recorded the “gravitational defiance” using a hi-speed camera. Here is a five-minute long video-bliss, brought to you by the Earth Unplugged channel. [video]

As Steve explains, it is like a tug-of war between the outer chain and the inner chain. The inner chain has to keep up with the fast-moving outer chain. As a result, it [the inner chain] goes up fast. It builds up momentum and is unable to stop itself. So, it ends up forming that arc while it is trying to slow down and change direction.

Benford’s Law Will Make You Wonder For a While

By Anupum Pant

Benford’s law is a fairly simple law to grasp and it will blow your mind. It deals with the leading digits of numbers.

So, for example, you have the number 28 – The leading digit for it would be 2. Similarly, the leading digit for 934 would be 9. Just pick the first digit. Now…

In a data set you’d say – it is common sense to assume that the probability of leading digit one (1) appearing would be more or less equal to that of leading digit nine (9).
As there are 9 possible leading digits, you’d think that the probability of each leading digit would compute to something around 0.11
You’d imagine that it would be normal to assume a nearly straight graph of probability vs. leading digit. But this isn’t true.

Benford’s law says

Your common sense fails. What actually happens is that the likelihood of 1 appearing as the first digit in a data set is around 0.3
For the following digits, the probability keeps decreasing. And the following graph appears. You’ll see that the numbers rarely start with nine!

Benford2

When does it work?

This counter-intuitive result applies to a wide variety of natural data sets. It works the best if your set spans quite a few orders of magnitude. Natural set of data like stock prices, electricity bills, populations, which could range from few single digit values to several digits work the best. Other data like the heights of people doesn’t work because it does not span “quite a few orders of magnitude”. Also, artificially tampered data fails to comply because the person who tampers does the same mistake everyone does. Therefore, Benford’s law is also used to detect frauds in data.

Example:

  1. Count the number of data points in a data set which have the leading digit 1 and write the number next to the number 1 in a table.
  2. Then, keep repeating it for all the numbers 2, 3, 4 and so on.
  3. Calculate the probabilities for each. In the end you’ll be left with a table that would look something like this. (Probability = Number of Data Points for that  digit / Total Data Points)
Leading Digit Digit Probability
1 0.301
2 0.17
3 0.125
4 0.097
5 0.079
6 0.067
7 0.058
8 0.051
9 0.046

How does it work?

Watch the  following video for the explanation:

Try it yourself: [Kirix]

Cryoseism – Frost Quakes in Canada

By Anupum Pant

Note: Remember that the ideas I share on this blog everyday don’t magically get formed in my brain. I’m no genius. What I am, is an average curious person. I read about things and then I experience a burning urge to find out more. I think of this blog as a record of everything I learn – kind of a public journal (NOT an Official gazette). I hope it helps you in some way. If it does, do mention it in the comments section below.

The Polar Vortex

For the past few days, in most of the things I’ve read, I’ve come across a reference to the extremely cold polar winds (incredible pictures) people are experiencing in the United States and Canada. 50 states have gone sub-zero in the US. Similarly, Canada is experiencing even  colder temperatures. While some have decided to stay at home, others are tossing boiling water to try out the Mpemba effect in the open. 8,500 miles away, almost sweating in a room with temperature 30 degrees (Celsius) above zero, I’m learning about new frost related phenomena that I had never heard of before.

My sympathies to the people who are suffering this bitter cold wave. 

Cryoseism

Thanks to the frost, I’m coming across some of the never-before-heard things that are appearing in the mainstream media. One of them which I came across yesterday was – Cryoseism or an Ice-quake.

People in Toronto woke up to loud sounds and rattling objects yesterday. People thought that an earthquake had hit Toronto. It wasn’t an earthquake. What they were experiencing was an Ice quake or Cryoseism.

What caused it?

Expanding water can be an extremely powerful force. It can break the strongest materials ever made. Industrial valves and pipes made of thick steel walls can be fractured by water as it expands. In this case, the earth got split open by it.

Unlike most other liquids, water expands on it freezing. Thus, ice formed is of higher volume and lower density. Although we aren’t dealing with density here, it is interesting to know, the phenomenon of expanding water is what makes gargantuan icebergs float on water. Apparently, there is nothing in the world that can contain expanding water without getting fractured (if you know about something that can, inform me in the comments section below). For a live demonstration, you can have a look at the video below, in which a metal pipe is split by freezing water.

This is what happened in Toronto. Water below the surface froze. As a result, it expanded and fractured the surface with a boom to find space for the 10% increase in volume. This was a Cryoseism.

With loud sounds some people have reported distant flashing lights. What was that about?

Electrical changes happen in the rocks when they get squeezed, pushed and rubbed around when pressure stored in the ground is released. The flashing lights are most definitely caused by these electrical changes due to rubbing and squeezing of rocks.

In the past the north and north-eastern parts of US have also reported such quakes.

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Valporate – Performance Enhancing Drug for Perfect Pitch

By Anupum Pant

Today we find out if it would be a good idea to impress your friends during the next gathering by hacking your brain with pills to learn a rare ability fairly quickly. But first, pay attention to the following jargon.

Perfect pitch

Perfect pitch is an exceptional ability among few gifted humans that enables them to recognize and re-create the pitch of a musical note instantly without the help of any external reference. There have been no cases of adults learning this ability by practice. However, pseudo absolute pitch can be learnt with great practice and only retained through regular use.

Brain plasticity

Learning to recognize musical notes, or any other ability for that matter can be reasonably easy at an early age due to a brain’s plastic state. The brain’s ability to change and adapt as a result of experience is far better at younger ages. As people age, they lose the ability to learn like kids.

For instance, picture the rate at which infants learn language. By the time they turn 2 – 4 years old, they start using thousands of words. Try learning a new language at the age of 35. It is tough.

However, a new research suggests that this state of brain can be recovered by using drugs. One such drug, according to Dr. Takao Hensch is Valporate.

Is Valporate a Performance Enhancing Drug?

No! it is not a performance enhancing drug. Valporate or Valporic acid is a drug sold under the common names – Depakote, Depacon and Stavzor. For several years it has been used to treat various disorders from migraines to bipolar disorder. It is a chemical substance that can cross the blood–brain barrier. As a result, it has the power to affect an individual’s perception, mood, consciousness, cognition, and behavior.

Dr. Takao Hensch, a Harvard University professor, recently published a study which tested the effects of Valporate on 23 healthy male subjects for two weeks. None of them had a musical experience. During this period they were trained in music. At the end of this study, researchers found that these 23 men did remarkably better than an average adult would do, at perfect pitch tests.

In the future

He thinks, may be 10 years down the line, this drug could be used to enhance other learning abilities like language learning among adults, by changing the state of their brains.

Presently, studies on how the brain changes at cellular level when this drug is taken are underway. Also, Dr. Hensch thinks that humans have evolved to experience these learning stages for a reason. If it is okay to mess around with it, is still being studied. At this stage, trying this out at home can be extremely risky. It would be wise for us to wait for scientists to come out with a comprehensive study on the effects of this drug.

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So, What Does The Fox Say?

By Anupum Pant

One of the most popular videos on YouTube last year was a song sung by two Norwegian brothers titled, The Fox. I’m not sure what was it exactly that made the video go viral, which is not to say that it wasn’t funny.

I think it was those absurd lyrics dropped at a time when you expect something serious, made it so popular. With an infectious catchy tune, the lyrics of this song seem very childish and at the same time, it is sung in a serious tone.
Popularity kept aside for a while, the number poses an important question which not many of us must have considered – What does the fox say? Makes us go looking for answers, doesn’t it?

As scientists would put it, the question this song poses, is indeed a challenging one. It isn’t easy to generally vocalize the sound made by a fox. Also, foxes make variation of sounds for different situations. Moreover, that, there are varieties of foxes out there, makes it even more difficult to answer the question.

The high pitched bark:
For instance, the red fox, which is the most common variety of fox, screams in a high-pitched bark. It sounds like a woman screaming in distress. In words, it sounds like a YAAGGAGHHGHHHHH. And is exactly the reason we aren’t taught this at school. Imagine, the teacher teaching with a YAAGGAGHHGHHHHH in a classroom.

The bird like sound:
When they fight, foxes can sound like birds. Unlike the screams discussed above, these sounds aren’t heard for long distances. Little fox pups also make these guttural sounds when they play. The sound is called Gekkering.

The high-pitched howl:
When greeting a more powerful foxes, weaker ones make a very high-pitched howl that can be heard for several kilometers.

Apart from these broad categories, they make several other subtle variations for different situations. The video below has a good collection of fox sounds:

On that note

What do you think the Cheetah says? Most of us have seen a cheetah (probably at the zoo), but not many must have heard it talk. It may come as a surprise to you that Cheetahs chirp like birds. Or you could call it more of a cat-fight sound.

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Raining Frogs and Fish

By Anupum Pant

Raining cats and dogs is a bit unlikely, but there is nothing wrong about saying, “it is raining frogs and fish”. It happens more often than you think. So, don’t be alarmed if one day you wake up and find fish on your terrace.

When we talk about rain, the one place in India which stands out is Kerala. As we’ve seen in a previous post that Kerala has seen red rains, it has also seen raining fish. This isn’t a joke. On February 12, 2008, people actually saw fish falling down from the sky.

Not just that. I’ve seen reports of water birds, tomatoes, coal, and even a boats falling from the sky.

Raining Animals

After a few moments of awe, when you look at the occurrence of raining animals with the science microscope, you’ll find that it is not something very extraordinary. In fact, there is a whole Wikipedia page on raining animals. It turns out, several places around the world have experienced raining frogs, fish, spiders, worms etc. And as always, science has an explanation for it.

How does it happen?

Water Sprouts: When tornadoes move on land, they can pick up trucks, houses, trees and what not. They suck up several things from the ground and cause total destruction along the path they travel. But, when such storms travel on water, they suck up water, fish and of course, frogs.

This experiment proves how a low pressure can pick up things. – [Experiment]

These things can stay up with the storm for a long time. And eventually when the storm comes on land and weakens the animals may drop down with rain. As a result, we see fish and frogs raining from the heavens.

There Is No Lake Like The Taal Lake

By Anupum Pant

Geologically this is quite a phenomenon and might get a bit confusing to grasp if you stop paying enough attention. Here we go…

Island in a lake on an island in a lake…

Taal lake is a freshwater lake on the Luzon island of Philippines. Almost at the center of this lake, is an island called the volcano island. At the center of this island is another lake called the main crater lake. And in this lake is a small landmass called the Vulcan point. [map]

Now take a deep breath…in short, it is, Luzon island > Taal lake > Volcano island > Main crater lake > Vulcan Point.

The main crater lake: Even though the crater lake isn’t a very big lake, it is still claimed as the  world’s largest lake on an island (Volcano Island) in a lake (Taal Lake) on an island (Luzon). Of course it is, where else in the whole world would you find a lake on an island in a lake on an island?

Vulcan point: On this world’s largest lake on an island in a lake on an island, is a tiny land mass called the Vulcan Point which is the world’s largest volcano in a lake (Main Crater Lake) on a volcano (Taal Volcano). It isn’t even big enough to support a small house.

Home to Unique Species

But all that is just a part of what is interesting about the Taal lake. Ecologically it is another marvel in a way that it is home to a few species of animals that are found nowhere else on earth. In this lake you’ll find the only varieties of fresh water sardines, sharks and sea snakes.

Reason: This lake was not a lake several thousands of years back. Then, due to volcanic eruptions, it got separated from the sea. Now the only thing that connected this water mass and the sea was Pansipit river. Gradually, several hundreds of years of precipitation converted this lake from a saltwater lake to a freshwater lake. For centuries, animals living here have remained isolated and have evolved into unique species to adapt to this desalination.

Sun’s Green Flash

By Anupum Pant

More often while setting than rising, if the conditions are right, a part of the sun (on the top) can appear green. This happens for very short interval lasting for about 2-3 seconds and is considered a rare phenomenon. Since it is green and lasts for a very small interval, it is also called the green flash, emerald flash or green ray. If you have ever captured it or plan to do it in the future, do share your results with me through mail/twitter. [See the animation] [Real GIF]

What does it look like?

Sometimes the sun’s rim can appear green (in optically zoomed images). Otherwise, when the sun is set, for a brief moment, it appears as if a part of sun has separated from the main body and has turned green. It is usually seen as a horizontal line, like in the video below. But, a few lucky ones have captured complete green auras too.

Why does it happen?

The sun gives out a white light, which contains all the colors – Green is one among  them. Normally, our eye isn’t able to resolve the separate colors and sees them as a mixture which is white. When the sun sets, our atmosphere acts like a prism and bends the colors. A few colors get bent more than others. For example, green bends more than red. As a result the two colors get separated enough to be resolved by our eye. But the right amount of bending happens only if the atmospheric conditions are right.

In extremely rare cases, blue or violet flashes have been reported. [image]

For a detailed explanation you can go through this – [Geometric Optics of Green Flashes]

At poles where the sun moves in a different manner, probably the green ray can last much longer. Admiral Richard Byrd has claimed to have seen this green flash for 35 minutes while on an expedition to Antarctica.