amazing – Page 8 – Awesci

The Coastline Paradox

By Anupum Pant

The length of Australia’s coastline according to two different sources is as follows:

Year Book of Australia (1978) – 36,735 km
Australian Handbook – 19,320 km

There is a significant difference in the numbers. In fact, one is almost double the other. So, what is really happening here? Which one is the correct data?
Actually, it depends. The correct data can be anyone of them or none of them. It completely depends on the kind of precision you decide to use while measuring the coastline. This is the coastline paradox.

The coastline paradox

The coastline paradox is the counter-intuitive observation that the coastline of a landmass does not have a well-defined length. – Wikipedia

The length of the coastline depends, in simple terms, on the length of scale you use to measure. For example, if you use a scale that is several kilometers long, you will get a total length which is much less than what you’d get when you would use a smaller scale. The longer scale, as explained neatly in this picture, will skip the details of the coastline.

This is exactly what happened when the two different sources measured the coastline of Australia. The first, Year Book of Ausralia, used a much longer scale than the one, Australian Handbook used. Ultimately, the great disparity in the result had to do with the precision of measurement. Had they used a scale just 1 mm in length, the result would have been a whooping 132,000 km.

This effect is similar to the mathematical fractal, Koch’s flake. Koch’s snowflake is a figure with finite area but infinite perimeter. Veritasium explains it better in this video:

Another factor is to take into account the estuaries to measure the length. Then,what about those little islands near the coast? and the little rocks that protrude out of the water surface? Which ones do you include to come out with the data? And the majestic Bunda cliffs? Probably this article from the 1970’s clarifies what was included and what was not during the time the results were published.

So, the next time someone decides to test your general knowledge and asks you the length of certain country’s coastline, your answer should be – “It depends.”

Largest Meteorite Left No Crater On Earth

By Anupum Pant

You should know: Meteor vs. Meteoroid vs. Meteorite

Meteor: The streak of light that we see in the sky is “Meteor”. When debris enters earth and gets burned up while entering, it leaves a streak of light. Unlike what is popularly believed, meteor is not the debris itself rather the word “meteor” refers to only the flash of light.

Meteoroid: A meteoroid is a mass that is small – ranging from a kilometer to only a few millimeters in diameter. Most meteoroids that enter the Earth’s atmosphere are so small that they vaporize completely and never reach the planet’s surface.

Meteorite: If the Meteoroid survives and reaches the earth’s surface, it becomes a Meteorite.

Hoba the Meteorite

About 80,000 years back, a ridiculously huge mix of Iron and Nickel entered the earth. It was so large that what was left out of all the burning through the atmosphere, measured 66,000 kg in the end. About half ton of this meteorite has gone to laboratories for research. Even after accounting for losses towards laboratories and vandalism, it is still the largest single mass of natural Iron on the Earth’s surface. It is the largest meteorite ever discovered till date and is called “Hoba”.

This meteorite was discovered by a farmer in Namibia in the year 1920. Since then, due to its mass, it has never been moved. The meteorite and the site has been declared as a national monument by the Namibian government and several tourists visit it every year.

Farmer’s Story:

One winter as I was hunting at the farm Hoba I noticed a strange rock. I sat down on it. Only its upper part was visible. The rock was black, and all around it was calcareous soil. I scratched the rock with my knife and saw there was a shine beneath the surface. I then chiselled off a piece and took it to the SWA Maatskappy in Grootfontein, whose director established it to be a meteorite.

If that was hardly interesting…

The most puzzling thing about this meteorite is probably not that it belongs to a very rare class of meteorites (Ataxite), but the fact that it has no crater to be seen around it. Normally, a meteorite of this size should have left a crater hundreds of meters wide.

The best theory that explains the absence of any preserved crater around it is that, this piece of rock must have hit the earth’s surface at a very low angle. As a result, it must have skipped on the surface like a flat stone on water surface. And in the end, must have landed at the place where it lies today.

McGurk Effect – What You See is What You Hear

By Anupum Pant

Do Not Cheat

Close your eyes: Before you watch this video, you should know that, when you watch it for the first time, you have to watch it with closed eyes. Well, you can’t ‘watch’ with closed eyes. It simply means, you have to just hear the sound track first. I’m sure you can do it because closing eyes for 5 seconds is not asking for much. I don’t have any veiled interests here. It is for you. You won’t appreciate the effect if you keep your eyes open during the first go.
Open your eyes: Watch it again with your eyes open. Be calm. It happens to everyone.

So that was the McGurk effect. It is a perfect example to show that accurate perception of reality may involve more than one sense. This is called “Multimodal perception”. In simple words, our senses do not learn from the surroundings independent from each other, they work together and learn together to help us perceive information.

The video

The video shows a man moving his lips as if saying “Ga” or “Da”, although it is just a visual of him saying that, let us call this the visual for the first sound (“Da” sound). The second sound is the “Ba” sound that is actually playing – this is the second sound.

When your eyes are closed, you hear the correct sound, the second sound – the “Ba” sound.
When you watch it again with your eyes open, you hear the “Da” sound. The brain combines the visual and audio signals to make you believe that the sound you are hearing is actually “Da”. Even if you are aware of this illusion, your brain doesn’t correct it for you, no matter how many times you repeat this.

Some interesting things about McGurk effect

You can focus anywhere on the face (not just the mouth) to perceive the same effect.
Women show a stronger McGurk effect than men.
Normally, people with mental disorders do not hear much difference in the sound with eyes open or closed.
By the age of 4 months, infants are able to identify facial movements and relate them to sounds. So, even infants show this effect to a certain extent.
Information rich perceptions are easier to remember. So, the next time you are trying to learn something, involve more senses. Probably involving a particular smell that goes with a piece of information will help you remember things well. Or a sound, maybe.

Note: Since my posts were getting longer everyday, I’ve tried to keep this one short. I don’t want the posts to be overwhelming for people who are not used to long reading. This blog is meant to make science sound interesting to everybody, not to scare them away from it. I’ll be waiting to receive your feedback on this. You can get in touch through twitter (@indigoanalysis)

There Is No Pink

By Anupum Pant

As we’ve seen before in a talk by David Eagleman, that there is nothing like colors really. They are simply electromagnetic waves with varying wavelengths. Colors are perceptions created by our brains that give us an evolutionary advantage to differentiate things easily. Without colors it would have been really difficult for us to spot fruits on trees. Of course that is just one of the millions of examples of how colors help us.

Perception kept aside for a while, we actually do know that there is a spectrum of visible light as we see it – ranges from violet to red. We see this spectrum on rainbows and thin films. Each of these colors on the spectrum is a wave (and particle) that has a particular frequency.
Mysteriously, the universal symbol of love, the color pink, is absent in this spectrum. There is no specific frequency for the color pink. There is no pink. Still we see it. So, what is pink, really? If it isn’t in the spectrum, why do we see it?

Why do we see pink?

Single type cone alone: We detect colors through these things called cones that are present at the back of our eye. There are 3 types of cones – let us call them red, blue and green. So, if an object absorbs all the white (sun) light and sends just the red color [waves] towards your eyes, red cones get activated and your brain tells you, you are seeing the color red. Similarly, green or blue cones get activated when the respective green or blue waves come towards your eye and then you are able to see the colors green or blue.

2 of them together: For other colors, things can get a bit complicated. To see pure yellow, both red and green cones have to get activated. Similarly, when green plus blue cones get activated, you see cyan, and blue plus red cones let you see the color magenta.

But cone aren’t switches that go either one or zero. They are like sliders. For instance, to see the violet color, your blue cones get fully active, while the red cones are activated only to a certain extent. As a result, your brain says, violet! That is 2 types of cones working together.

3 of them together: Now let us see how three of them work together. The color white activates all the 3 type of cones fully. Black activates none. And so on…

Pink does something similar as it uses three types of cones. To see pink, all three types of cones have to work together. When red cones get fully active and the other two are only partially activated, we see the color pink.

So, even if objects don’t reflect magenta, yellow or pink (or several other RGB combinations like that), our cones can send mixed signals to our brains and the brain in turn creates these colors for us. In reality, they don’t exist.

[Read more]

What is pink really?

Henry Reich of minute physics, in his video explains this by referring to pink as white minus green. So, according to them, the color pink is actually minus green. In short, absence of green color is nothing but pink. I’ve attached the video below:

Mpemba Effect – Hot Water Freezes Faster Than Cold Water

By Anupum Pant

In the past, we have seen that when it comes to estimating temperature, we are not so smart. Once again seeing the Mpemba Effect defying all known logic, reminds me to be careful about applying logic to most of the natural phenomena which are seemingly simple but in reality are extremely complicated.

By applying simple logic, a 7-year-old could tell you that cold water should turn into ice quicker than hot water would. It should, because a hot liquid contains a lot more heat as compared to a colder liquid, which [the heat] has to be removed in order to freeze it. Yes, it is what anyone who is unaware of the Mpemba Effect would think. But, that isn’t the case with water. It turns out that a very common substance – water – is not as simple as it looks.

Mpemba Effect

Since the time of Aristotle and Descartes, scientists have noted that hot water can freeze faster than cold water (and yet the effect is not popularly known among us today). Although the effect was noted back then, the actual mechanism which caused it remained a mystery all along…until the year 2013.

All this time this effect must have been known by some other term because, it was not until the 1960s it was named “Mpemba effect”. It was named that after a Tanzanian cookery student Erasto Mpemba when he observed that hot ice cream mix froze faster than the cold mix.

Several theories have tried to explain the mechanisms that cause the Mpemba Effect. Not even one of them was convincing enough. Probably this is what propelled the geniuses from Singapore who could finally solve this mystery during the month of October this year.

What causes it?

In simple words, Hydrogen bonds cause this effect – faster freezing hot water. Normally, individual water molecules are connected by this bond called the Hydrogen bond. Think of the water molecule as a string with two bullies – hydrogen bonds – one on either side. These Hydrogen bonds pull this string from both sides. As a result, the string stretches. We’ve all fought with rubber bands and know that a stretched string has a butt load of energy stored inside it. The same thing happens with water. Energy is stored in stretched water molecules at normal temperature. This extra energy has to be removed to cool water.

At a higher temperature, the heat kind of weakens these bullies. So, the weak bullies aren’t able to pull the string as much. Now, individual molecules sit apart. They are no longer stretched. Thus, not much energy is stored in these strings anymore. They have given up energy. There is no longer any extra energy that needs to be removed. Hence, cooling is faster.

Sorry: Today I don’t have my buddy – the internet – with me. So, you won’t see any outgoing reference links today. I have a just a bit of internet (a slower 2G connection) which I’m using up to publish this.

Space Oddities – Part I

By Anupum Pant

Note

During the past few days, I came across a couple of interesting things related to space, which I felt were worth sharing. Individually, none of them could have been made into a good long article. So, I thought of compiling a list of these amusing post-lets to form a single good read.

Also, in the words of Chris Hadfield: Since Space is profound, endless, a textured black, a bottomless eternal bucket of untouchable velvet and untwinkling stars, it is a place that holds infinite possibilities for me to collect more of such amusing ideas. Therefore, I have suffixed the title of this post with a phrase – Part 1 – that leaves an open possibility for other such articles. If you’d like to contribute snippets for the upcoming parts of this post, you can get in touch with me. [About Page]

Space oddities begin

1. A year in Venus:

Two facts. Venus rotates on its axis only once every 243 earth days. It orbits the sun every 224.64 earth days. But, both of these things put together mean that on Venus, a day is longer than a year. Or simply put, almost everyday is everyone’s birthday. Wonderful, isn’t it?
Also, Venus rotates backwards. So, the sun as seen from Venus, rises from the west and sets in the east. The rotation is so slow that it is unable to generate a magnetic field like earth.

2. International Space Station:

Floating around in the ISS, it is often possible for an astronaut to get struck floating in the middle of a room when walls are out of reach. To get out of such a position, astronauts have to be patient and have use the drafts of light crosswinds from fans or call for help for a physical push. – [Source]

3. Going from ‘a planet’ to ‘not a planet’:

Discovered in 1930, Pluto was originally classified as the ninth planet from the Sun. In the year 2006, this definition excluded Pluto and reclassified it as a member of the new “dwarf planet” category.
For the whole time during which Pluto was a planet, it did not complete even half a orbit. That means within half a Pluto year, it went from being called a planet to not a planet. Sad.
Today, Pluto is the tenth-most-massive body observed directly orbiting the Sun or the largest object in the Kuiper belt.

4. Visibility from space:

We have always been told that the only man-made object that can be seen from space is the Great Wall of China, but it is NOT true. You cannot actually see the great wall of China from space.
What you can actually see is the biggest structure made by living organisms (not humans) – The Great Barrier Reef.

5. Sun as seen from Mercury:

On Mercury, the sun appears to briefly reverse its usual east to west motion once every Mercurian year. The effect is visible from any place on Mercury, but there are certain places on its surface, where an observer would be able to see the Sun rise about halfway, reverse and set, and then rise again, all within the same day. [Sun’s unusual behaviour as seen from Mercury]

6. Flying on Titan is easy:

The largest moon of Saturn is a very peculiar place. It is the only known moon to have an atmosphere. But that isn’t all.
Its atmosphere has 1.19 times more mass than the earth’s atmosphere. Secondly, the gravity is far lower as compared to earth. This means, had there been humans on Titan, they would have been able fly in Titan by just flapping wings attached to their arms.

In the end, I’d like to leave you with two very interesting things. An inspirational comic by Zen Pencils and a revised version of David Bowie’s Space Oddity, recorded by Commander Chris Hadfield on board the International Space Station (I had this on repeat the entire time I was writing this article):

Lycurgus Cup – An Ancient Nanotech Marvel

By Anupum Pant

The concepts of modern nanotechnology must have been first seeded in the year 1959 by the renowned physicist Richard Feynman, but Romans were already doing it back in 300 AD (around 290-325 AD). About 1700 years back, utilizing the principles of Nanotechnology, Roman engineers had crafted a magnificent chalice – Lycurgus Cup (picture). Like the Prince Rupert’s drop, this is another glass marvel you should know about.

Side note: You can listen to the legendary lecture by Dr. Feynman on YouTube – There’s Plenty of Room at the Bottom, where he discusses the “possibility of synthesis via direct manipulation of atoms”, or Nanotechnology.

Lycurgus cup description

The Lycurgus cup was probably the first ever optical artificial [meta]material – Ruby Glass – engineered to have properties that may not be found in nature. Its unusual optical properties are something that makes it stand out.

Normally, the cup appears green, but if it is illuminated from the inside or lit up using a light placed behind it, it glows ruby-red; hence the name, ruby glass. This kind of glass is known as a Dichroic glass. Dichroic literally means ”two colored” and is derived from the Greek words ”di” for two, and ”chroma” for color; in this case, the colors green and red.

The technology behind this cup baffled scientists for around 40 years (from 1950s to 1990s). It was only in 1990s that they figured out how it really worked. The goblet has been preserved well, and is presently at display in the British Museum.

Dichroic glass

Dichroic glasses do not use paints, dyes, or any coloring agents for the color. They are made using fine coatings on glass. The coatings themselves do not have a color, but rather they bend light to reflect colors like a prism does, to make rainbows.

These colors are visible due to the presence of very minute amounts of finely ground gold and silver particles in it. Romans could have included these powders unknowingly as contaminants or might have added them on purpose to achieve the very effect, we’ll never know.

Inspired by an age-old technology

NASA, in the 1950s, used a similar technology to fabricate a kind of glass that could selectively reflect light wavelengths. They achieved this by depositing a thin-film of metal on the glass.

With innumerable combinations of oxides, glass colors and patterns available, the possibilities to utilize this phenomenon for various useful purposes are endless.
The unusual properties of this cup have also inspired material scientists to create concepts for an invisibility cloak using modern nanofabrication technology. [Source]

I want to study interesting materials like these

If you think the Lycurgus cup, Wolverine’s claws and Aerogels (If you haven’t heard about it, you must definitely check this out!) are awesome. You can make a career in researching materials like these by making a foray into Materials Science and Engineering. Most good universities offer a course in it. It is a budding field, growing at a rapid pace, replete with real-world challenging conundrums waiting to be resolved.

Is There a Scientific Explanation for Everything?

By Anupum Pant

Today we have Dr. Eben Alexander III, an American Neurosurgeon and the author of a number one New York Times bestseller, in the house. Well, not really, but let us imagine he is here with us.

Background: Dr. Eben Alexander has been a member of the American Medical Association, a neurosurgeon and has taught at the Harvard school of medical sciences. He has spent a lot of time among scientists believing that there is always a scientific explanation for everything. But, one day, he experienced something that defied all scientific explanation. Turns out, there isn’t a scientific explanation for everything. Later he went on to write a number one New York Times bestselling book – Proof of Heaven: A Neurosurgeon’s Journey into the Afterlife.

Like logical open-minded Possibilians, let us read the book first, to start arguing against it. I haven’t read it yet. So, for now, I’ll stick to writing about just what I’ve learnt about it, rather than formulating theories against it.

The story: In the year 2008, Eben was affected by a severe case of bacterial Meningitis and fell into a coma for 6 days. His Neocortex showed no signs of activity. When he got cured miraculously (with just 2% survival chance) and returned from coma, he had experienced something out of this world. According to him, during the coma, he had experienced a vivid journey into the afterlife – kind of a near death experience.

The experience: When he fell into coma, he found himself in a dark and suffocating place for a very long time. Later a spinning bright light with a beautiful melody came in slowly and “rescued” him out of this agony. It took him to a fertile green land. Some points that he makes about this mysterious land:

There was no need for a spoken word to communicate there. Every communication was telepathic.
The instant you asked questions, you knew the detailed answers for those questions. (Something similar to the experience of Zen)
The experience was more real than real-life. In comparison, real-life seemed like an illusion.

You can watch a 42 minute long interview here for further details. [Video]
I’d also suggest reading: Supernatural: Meetings with the Ancient Teachers of Mankind

Possibilianism

Although we’ve progressed a lot in science and technology in the past 400 years, there is a much more science doesn’t explain than there are things it can.

For instance, to make our equations sound right, we assume there is something out there we can’t touch, feel or sense in any way; we choose to call it dark matter. The most incredible thing – 90% of our universe is dark matter (and dark energy). That is too much to sweep under the rug. And we know nothing about it.

In the words of David Eagleman – “Our ignorance of the cosmos is too vast to commit to atheism, and yet we know too much to commit to a particular religion.”

Or in the words of Carl Sagan – “An atheist is someone who is certain that God does not exist, someone who has compelling evidence against the existence of God. I know of no such compelling evidence. Because God can be relegated to remote times and places and to ultimate causes, we would have to know a great deal more about the universe than we do now to be sure that no such God exists. To be certain of the existence of God and to be certain of the nonexistence of God seem to me to be the confident extremes in a subject so riddled with doubt and uncertainty as to inspire very little confidence indeed.”

Klein Bottle – A Bottle That Contains Itself

By Anupum Pant

To appreciate the beauty of mathematics and nature there is no escaping without learning about a Klein Bottle. A three-dimensional representation of a Klein bottle looks like this – [image]

There are number of phrases you can use to describe (not exhaustively) it. A few of them are as follows:

An object with no boundaries.
An object with no inside or outside.
One sided surface.
Non-orientable surface

Wikipedia describes it as:

The Klein bottle is a non-orientable surface; informally, it is a surface in which notions of left and right cannot be consistently defined.

Simplifying things: A Möbius strip is a simpler example of a non-orientable object. That means it has no inside or outside. Add another aspect – having no boundaries – to it, it gets more complex and you end up with a Klein bottle.
If you haven’t heard of Möbius strips, to understand such surfaces, you can make one for yourself now.

Tear off a strip of paper.
Hold it horizontally, straight with both of the short edges in your hands.
Now, twist one of the edges by 180 degrees and join the two short edges. You’ll have something like this in your hands – [image]

Test the surface and edges: On this object you just created, move your finger along the surface. You’ll find that your finger comes back to the same place eventually. There is no inside or outside for this object, there is just one surface.
The same thing happens with its edge (try moving your finger along the edge). Here is a Music box playing a Harry Potter theme continuous – forward, inverted, forward and so on – manner; Relevant video: [video]

Now spin it (the Möbius Strip) fast. You can NOT practically do it. I mean, spinning it like you spin a circle and get a sphere. There! You have a Klein bottle. It is better than a Möbius strip in a way that it (Klein Bottle) has no boundaries.

Klein bottles cannot actually exist in our three-dimensional worlds, the ones that look like them (Klein Bottles) are just 3D representations of a 4D object. Like a two-dimensional drawing of a 3D cube. These models are available for you to buy. Interestingly, in spite of having no inside or outside, they can be filled with a liquid. But, given the opposing force of air, they are pretty tough to fill. It is important to note that the 3D representation of a 4D Klein bottle has an intersection of material, this doesn’t happen in 4D. It is like the intersecting edges of a 3D cube in the 2D representation.

You’re thinking 3D? At MIT (and other places) 4D printing is already happening.

If you are having a tough time imagining this 4D object, the following 4D animation might help (or leave you perplexed) – [video]
[Extra reading for math geeks] as if they already didn’t know about Klein bottles.

Axolotl – A Walking Fish That can Regenerate Limbs

By Anupum Pant

If you are looking at an Axolotl for the first time, it will confuse you. With an oddly shaped body that resembles both a catfish and a salamander, you’ll wonder if it lives in water or on land. [Image]

What is it?

A fish? Axolotl, commonly known as the Mexican Walking Fish, isn’t actually a fish. It is an amphibian, which means it has both lungs and gills. They almost never come out of water, hold their breath and take in oxygen using their gills (those three pairs of parts coming out at the back of its head are the gills). They can hold their breath for a year, beat that Mr. David Blaine.

Or Salamanders? They are closely related to salamanders and interestingly the adult Axolotls look like baby Salamanders. They have long abandoned the usual amphibian-transformation from a larva stage to an adult. Unlike Salamanders, they don’t transform into adults that can live outside water. They stay in water and walk around on the water-bed.

However, strange species of Axolotl was once delivered to a zoologist Auguste Duméril, which had somehow transformed like salamanders and would happily come out of water. But this transformation (metamorphosis) shortened their life span. Later it was found that this process can be artificially triggered by injecting iodine. (Do NOT try this at home)

As pets: Today, these animals are fairly common and are used as exotic pets all around the world. Especially in Japan, people love to have them in their aquariums.

Side note: Like several other Pokémon based on real animals, Whooper and Mudkip were actually based on Axolotls.

Regenerative Powers

Besides having the ability to walk underwater and its unusual appearance, there is something that is much more interesting about them. Unlike, almost any other vertebrate, they have the power to regenerate various cells. Not just cells, Axolotls can regenerate complete body parts – limbs, gills, eyes, kidneys, even large portions of its liver and its heart muscle. Even portions of its spine and brain can be regenerated. They are able to grow back a severed limb in span of few months. This is the reason scientists love these creatures and conduct a number of studies on them every year.

A Few Things About Sloths Everybody Should Know

by Anupum Pant

A few days back, on 20th October, Sloth Day was celebrated all around the world. You’d be thinking, what is so good about these strange animals, that makes people have a special day around them. Well, in that case, you need to read this.

What are these creatures?

Sloths are slow animals that make even cows look extremely active. They are so slow that they are almost stationary and algae grows on their hair. Most of their life is spent on trees hanging upside down. They hang on trees to protect themselves from the predators on the ground. Their bodies are so well engineered to stay inverted that the hair on their bodies, is oriented in the opposite direction – growing from stomach to back (This helps them to stay dry by draining water easily). Even dead sloths have been know to retain their grip and remain suspended after death. They come down only around once a week to excrete. They eat, sleep, travel, find partners, mate, give birth and even raise young ones in the canopies.

Although sloths might seem gross, creepy and unseemly, they really aren’t that bad. Sloths are sweet looking [1] [2] [3] animals (especially their babies, they are adorable) who can also swim efficiently and move wisely. We can definitely learn a lot from them.

Their diet is unbelievable

Sloths eat only leaves throughout their lives. They chew leaves slowly like cows to extract whatever nutrients they can. Sloth intestines are also adapted to extract the maximum out of their poor quality food, they are unusually long. They often like to shift to a different kind of leaf after a day or two. This balances their nutrient intake. Humans couldn’t possibly survive on a leafy salad diet for a very long time.

To save energy, sloths drop the temperature of their bodies at night. Even their bodies have more bones than muscles to prevent wastage of energy through muscular movement. After the Orangutan they are the most energy efficient animals.

Other facts about them

Sloths have blunt teeth to chew leaves properly, have large claws to hang on to branches and inverted fur orientation (as also mentioned before). Another interesting thing about them is that they have remained physically un-evolved for a long time because they don’t really have to compete with anyone else for their diet.

Mutualisms

This is where the awesomeness of Sloths come in. Sloths are home to a several kinds of other organism (tiny ones living in their fur). These organism depend on sloths (hosts) for various things and in turn provide an advantage to their hosts. This is called mutualism.

Algae + Sloth – Algae, for instance, uses the long grooves on sloth hair to grow with a secure footing. As a rent for this safe apartment, the algae gives them [sloths] a nice shade of green color to camouflage on trees. This and their still bodies make them virtually impossible to spot with the naked eye. The camouflage protects them from eagles.
Bacteria + Sloth – Apart from the several other bacteria which live inside a sloth to digest the leafy diet, two kinds of Cyanobacteria live on sloth furs too. These bacteria also give sloths a nice gray hue which helps them in the same ways as above.
The Sloth Moth – The Pyralidae Moth also live on Sloths. These feed on the algae which grows on the fur. In return for the good food, moths give them nothing. Yes, nothing. This is called Commensalism.
Others – Similarly, various other organisms like flies, mites and three types of beetles are often found living in a Sloth. Up to 900 beetles have been found on a single Sloth!

There is so much more to write about these amazing little creatures who provide for so many other creatures too. I’ll keep it for the second part that I’ll write some other day. So the next time you see a Sloth crossing the road, carefully pick it up by holding its mid body and gently place it on a tree. Remember to use a glove/cloth.