gravity – Awesci – Science Everyday

Double Pendulum and Why We Can Never Predict Weather

By Anupum Pant

A single weight, if suspended from the ceiling, forms a pendulum – A simple device whose position at any point in the future can be predicted fairly easily if the initial conditions are known.

Now, if another pendulum is attached to the bottom of this first pendulum, preferably using a rod (not a string), and is then given a good amount of initial energy, things move from a simple single pendulum to a very complicated two pendulum system.

The system turns so chaotic that it is impossible to make two of such exactly same systems, forget keeping them synchronised. Even if every mass and ever little distance is carefully calculated and two such systems are constructed, it would be impossible to drop them from the same height and see them move in the exactly same manner.

That is because even if they are really dropped from the same position, they’d in reality have a very tiny difference in some parameter, which would eventually become so huge that the two systems would soon go out of sync. Initially they might really seem like they are moving in a synchronized motion, but that doesn’t stay for too long.

This is also the reason why we’ll never be able to predict the weather perfectly. Nikola explains…

Gravity Explained

By Anupum Pant

I’m always amazed by how teachers all around the world come up with fantastic ideas to make science easier for kids. A couple of months back we saw a video of Dan Burns using a trampoline to explain the space-time warping at a Physics Teacher SOS workshop in Los Gatos High School. In fact there is even a place on the web where you can learn it to do yourself [here].

Another explanation which came around much later just takes the cake. EdwardCurrent uses a “space-time stretcher” to demonstrate how gravity, well, stretches the space-time fabric. Moreover, the material he uses to construct this teaching aid comes mostly amongst all the old stuff lying in his garage.

Continue reading Gravity Explained

The Weissenberg Effect

By Anupum Pant

Remember the time we talked about a boiled egg spinning on a pool of milk? If you don’t then it’s good to know that if you do spin a hard-boiled egg on a pool of milk (or any relatively viscous liquid) the milk mysteriously climbs the side of the egg, reaches the equator, and then sprinkles around beautifully. It’s fun to see it happen. This is something similar…

The thing we see today is called the Weissenberg effect and this is how it works.

You take a spinning rod and put it into a solution of liquid polymer (which is usually very viscous). And when you do that, you see that the liquid polymer magically climbs the walls of the rod.

Some liquids reach a little high and never beyond. While others can climb up really high. The difference in heights to which different liquids can climb to is demonstrated in the following video very clearly. The three liquids used in it are as follows:

Guar gum solution crosslinked with sodium tetraborate
Pancake batter
and Dyed glue crosslinked with sodium tetraborate.

[Read more]

Outperforming Humans – Speed

By Anupum Pant

Humans can use tools, communicate, count, make others laugh, socialize and are self aware too. We also have emotions and a pretty good memory. All of the things put into a single creature sure makes the “most advanced” creature we’ve ever known. But if these traits are considered individually, you’ll easily find an animal who beats us at one trait at a time. Today, I wanted to read and write about where humans stand when it comes to speed.

Talk about running speeds and the fastest person ever, Usain Bolt comes to my mind. A bolt indeed. As on date, if I’m not wrong, the world record set by him in the 100m race is 9.58 seconds. To put this human freak show into perspective, the average speed of the Jamaican sprinter in this race comes to about 37 km per hour (23 miles per hour). And he’s clocked 28 mph somewhere in the race, they say.

In a world full of cars and planes, where distances travelled have become really huge, 28 mph sounds like a speed which does no good in our practical lives. And yet, it takes an Olympic runner to clock that speed. Normally, people run at about, say 10 mph. Damn!
The biological human limit to running speeds is estimated to be about 40 mph.

Quick fact: The fastest human objects ever are Helios 2 (a German probe) clocks about 150,000 mph. Another spacecraft, Juno does about 25 miles in a single second!

Now compare that with a Peregrine Falcon which can make use of the gravity and its perfectly aerodynamic body to travel at a speed of 216 mph (360 kph). But, that’s hardly any work for the animal. It’d the gravity making it fall.

In level flight, the white throated needletail (swift) can fly at speeds more than 100 miles per hour (up to 106). That’s the fastest bird if you do not count gravity assist.

An on land, of course the Cheetah takes the prize with about 70 mph of running speed. But, there’s a catch. If you measure speeds of animals relative to their body sizes, there’s a little blood sucking mite that beats cheetah by a huge margin.

The fastest swimming fish is the sailfish, which can swim and jump for small distances at about 70 mph.

Humans can swim at about 5 miles per hour.

Moving at 35 miles per hour a jack rabbit can travel faster than a human. The patas monkey, the fastest primate, runs at about 35 miles per hour too!

Now these are some animals you probably already know. Soon there’s more to come. In the coming days I wish to do a series on outperforming humans…Maybe I’ll write about endurance next.

Keep reading for more.

Helium Balloon in a Car

By Anupum Pant

Background

Whenever I choose to write about Helium, there’s something I almost never forget to mention – Helium is precious (Click to know why). So, if you’ve read that, you’ll know that you shouldn’t use it in party balloons, nor should you use it to make your voice sound funny. These are the most silliest things you could do with a borderline non-renewable resource. However, if someone uses it in party balloons to make science look cool to 5-year-old, it’s beautiful.

The Experiment

Destin, a super-cool dad, from the YouTube channel Smarter every day, did exactly that. This is what he did:

Pendulum in a car: First, he tied a pendulum to the roof of his car. Then he accelerated the car. As everyone must have guessed, the pendulum moved back as the car accelerated. It’s natural for our brains to assume that everything would move back in an accelerating vehicle.

Helium Balloon in a car: Next, he tied a balloon filled with Helium to the base of the car. Then, right when he was about to accelerate his car, he asked his 5 year olds sitting in the back seat – “Where do you think the balloon would go if I accelerate?”

Answer the question before proceeding, and reason it if you can. (Even if you don’t know it, it’s easier to guess it right now because of the build up I gave in the previous paragraphs)

The Answer

Unless you already have dealt with this “anomaly”, it’s pretty tough to guess that the balloon would actually move forward as the car accelerates. Yes, it moves forward! Something moving forward in an accelerating car sounds counter intuitive. I knew it because someone had asked me it in a physics puzzle sometime back. Just for the record, I had answered it wrong then. There’s no way I could have guessed, or reasoned it accurately the first time. Did you?

The balloon seems to be defying the laws of physics. But a helium balloon moving forward as the car accelerates can be completely explained by physics. It’s just our brain fooling us again.

Simple Analogy

Here’s how Destin explains it with a simple analogy – using a glass jar filled incompletely with water (so there’s an air bubble inside). Assume that the glass jar is like the car. The water in it, is like the air in the car. And the Helium balloon is like the air bubble in the jar – Since an air bubble is lighter than water, it is safe to assume that because even Helium is lighter than the air.

Now when the jar accelerates forward, the water in the jar moves back – so does the air in the car. As a result, the air in the jar moves forward – just like the Helium balloon does.

Here, watch the video if that sounds too confusing…

Most of you probably know this. But I’m sure that many don’t. Moreover I found the video really cute – A super cool dad explaining science to his little kids in a car. Plus they ask you to go to their audible link that would get you a free audio book. At the same time, it would help a cool dad fund his children’s education. My heart melted. If nothing, the video will at least make you smile.

Everyone Knows Magnet in a Copper Tube, But this…

By Anupum Pant

I’m sure you know that if you let a strong magnet drop along a thick copper tube, the magnet falls in a very interesting manner. It falls slower than it normally should, delaying the span of the fall, as if gravity acting on the magnet mysteriously drops. If you haven’t heard about it, I’ll give it to you, you probably aren’t a YouTube addict, and that’s definitely good (and maybe also bad because there’s awesome stuff out there which you are missing). Just watch this, what I just said will start making sense…

Why does this happen?

OK, that’s pretty cool, but you knew about this little magnet-copper trick already, and you were expecting something more? You got it.

Whatever you just saw neither was a magic trick, nor was the Copper tube acting as an anti-gravity machine. This is pure science, can be easily explained by it. Here…

When a magnet moves quickly near a metal, it generates current in the metal. Here, current is generated in the Copper tube.
The current generated in the tube generates another magnetic field which opposes the magnetic field of the magnet and pushes the magnet upwards, away from the force of gravity. Gravity being stronger, pulls it down, but not with as much force because the magnet is being pushed in the other direction too. That’s the simple science behind it.
Still, someone else could explain it better on a page which is completely dedicated to explain it to you. [Here] and [Here]

But, you probably knew even that -The trick and the science behind it. So, there’s more for your-kind-of-people.

A new skill-toy that uses the same…

Feel flux. An amazing new skill toy that works on the same principle. Who would have thought, playing with gravity could get fun. The crowd funding campaign for it runs on indiegogo. Go fund it!

Space Oddities – Part II

By Anupum Pant

pat on the back self — Self-administered pat on the back to me.

A few days back, in the month of December I had compiled a list of 6 space oddities that really interested me. At that time, I was pretty sure I would stumble upon a few more odd/interesting things about space within a month or two. With that in mind, I had decided to suffix the heading with “Part – I”. Four months have passed. That was a very thoughtful thing I did – thinking 4 months into the future. I have to appreciate my forethought (with a self-administered pat on the back) for doing that because today I’m back with a few more of these odd / interesting things about space and I’m still not embarrassed about the heading for the post.

So, here is the part II of space oddities (read the part I here):

1. A Hole in the Universe

About 7 years from now, researchers from University of Minnesota found out about a really huge void in our universe. The abnormal hole measures approximately sixty billion trillion miles. In easier words, it is about 10 Billion light years wide. Imagine! A beam of light would takes 10 Billion years to travel through that empty place. How lonely would it be at the centre of it. The void is bigger than anything else scientists have ever seen in space.

The whole volume of space shows no sign of any stars, planets, asteroids, gases, clouds, dust. The volume doesn’t even have any signs of dark matter (95% of our universe is dark matter) too. [read more about it]

2. Costliest thing ever built

Think of a huge 5 bed room house floating in space that can be seen moving from the surface of the earth with the naked eye! Yes, I’m talking about the International Space Station. It is a whooping 200,000 kg object that is 171 feet long, 240 feet wide and 90 feet high.

When it comes to the price of building something this huge in space, it beats everything from the most lavish sky scrappers to the most largest dams ever built. The price of building it is estimated to be about $160 Billion and fortunately the cost is shared by Canada, the European Union, Japan, Russia and the US. It is officially the most expensive object ever constructed, and it is NOT on earth! – Guinness book of World Records.

3. The Cosmic Smile Continue reading Space Oddities – Part II

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.

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.

Gravity Light – A Light With No Running Costs

By Anupum Pant

A $5 lamp that lights up using gravity can be used without electricity or batteries, over and over again with no running costs. Impressive enough? There is more.

A British company, after working for 4 years on this project, with an aim to replace kerosene lamps, started an internet fundraising campaign on Indiegogo and successfully raised about 7 times more than what they had aimed for – aimed for raising a fund of $55,000 and ended up raising $399,590. They had invented the Gravity Light.

Gravity light uses the force of gravity to light up – a free, completely reliable and totally unlimited source of energy. For it to start, the user is supposed to lift up a hanging weight of about 10 kg. And there! As the bag full of dirt, stones or sand starts coming down slowly, it lights up an LED light. The weight keeps coming down for about 30 minutes and then it has to be raised again. It generated a very minuscule amount of electricity and manages to give out a much brighter light than a kerosene lamp.

The energy generated from it can also be used to charge batteries, charge phones, run a radios etc, with attached accessories.

Interestingly, the company has plans to develop various other gravity powered solutions. So, in the future, we might probably see a way to reach the internet without batteries or electricity.

Other interesting lighting ideas:

[Gravia lamp] [Water + Bleach lamp] [Algae + CO2 lamp]