Into the night sky
On the seventh anniversary of World Asteroid Day, let us get to know more about these celestial objects.
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Power of the pull
(Part #8) Hanuman finds out how the Moon orbits the Earth and also makes a new friend.
The story so far: Hanuman learns about gravity, air pressure, temperature and density and that air pressure, density and temperature decrease when gravity decreases.
Hanuman: Friends, I have a nagging doubt.
Air molecules: What about, Hanuman?
Hanuman: Earth’s gravity is what is pulling us all towards it and keeping us from falling off, right?
Air molecules: Absolutely. It’s what Sir Isaac Newton deduced when the apple fell from the tree.
Hanuman: Then why isn’t the Moon not being pulled towards Earth?
Air molecules: Ummm…Maybe it is because it escaped Earth’s gravitational pull…
Hanuman: Can’t be! If that’s the case, then the Moon wouldn’t be revolving around Earth.
Air molecules: Hmmm…Wait! We know someone who may know the answer.
Hanuman: Who is it?
Air molecules: Nala, son of Viswakarma, the divine architect. He is very smart and has a good knowledge of physics.
So the air molecules and Hanuman visit Nala, who is surprised to see them flying towards his house.
(Illustration: Sahil Upalekar)
Nala: Welcome, Hanuman!
Hanuman: How do you know me, Nala?! You are a vanara (half-man half-ape) as well?
Nala: Yes, I am a vanara. And who doesn’t know you? You are famous! So, what brings you here?
Hanuman: I have a doubt, which my friends say you can help clarify.
Nala: What is it?
Hanuman: How come the Moon is not affected by Earth’s gravity?
Nala: It is. But it does not move towards Earth because of Angular Velocity.
Hanuman: What’s that??
Nala: Let me explain how Newton figured it out.
Hanuman: Newton, again! Fine…
Nala: Newton had the same doubt — how come the Moon, which weighs 7.3 x 10^22 kg, is not falling towards Earth? He had no one to help, so he started finding answers using his thought experiment.
Hanuman: What does ‘thought experiment’ mean?
Nala: It means to try and find answers by imagining a scenario. In this case, it famously came to be known as Newton’s cannon ball experiment.
Hanuman: What does the Moon have to do with a cannon?
Nala: Imagine that you are standing on top of Mount Meru and shoot a cannon ball horizontally at a very low speed. What will happen?
Hanuman: It may fall very close to the cannon.
Nala: Exactly. It will follow a horizontal path at the start and then eventually drop because of gravity. What will happen if you increase the speed?
Hanuman: It may fall a little farther.
Nala: Yes, it will take a longer path. As you keep increasing the speed, the cannon ball may travel a longer distance but it will eventually fall down. Now tell me, Hanuman, what will be the shape of the ball’s path?
Hanuman: A straight line?
Nala: No, it will be a curve. Air molecules, please throw some seeds into the air to demonstrate.
The air molecules throw some seeds, which follow a curved path.
Nala: As you keep increasing the speed, the projectile — anything thrown using applied force can be called a projectile — takes a bigger curvature. At one point, it will start to match the curvature of Earth.
Hanuman: How?
Nala: What is the shape of Earth?
Hanuman: A sphere
Nala: If you keep increasing the projectile’s speed, it will start to travel far and, at the same time, be pulled down by Earth’s gravity. At some point, its speed and the pull of gravity will match so that the projectile will continue to fall without touching the ground and thus complete a full circle around Earth.
Hanuman: Gravity is very low at 3,84,000 km — the distance of the Moon from Earth — and friction is also less because there are no air molecules, making it a vacuum-like environment. So it never losses its speed.
Nala: Yes. And this cycle just goes on for millions of years. This is what we call as its orbit. Eventually, there will be small changes in the orbit. Our Moon is moving away from Earth at about 3.8cm per year but other planets’ Moons may either move away or closer and crash into them.
Hanuman: But you still haven’t told me what angular velocity is.
Nala: Oh yes. Speed with direction is velocity. Velocity with a certain angle is angular velocity.
Hanuman: So this is what keeps moon circling around Earth.
Nala: Orbiting.
Hanuman: All right! Orbiting! Are you always this geeky?
Nala: Ha ha! Yes, since my birth.
Hanuman: Can we be friends?
Nala: Of course!
Hanuman (sarcastically): I need some smart friends too.
Air molecules (cheekily): In that case, you can fly yourself home without our help.
Hanuman: Hey, no! I was just kidding!
Air molecules (laughing): So were we!
The author is the founder and CEO of Vaayusastra Aerospace, an IIT-Madras incubated ed-tech startup that offers Air Science workshops for children between five and 14 years.
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Below is an illustration of how and why the moon orbits around Earth. Based on your reading of the conversation between Hanuman and Nala, can you drag and drop the labels into the correct boxes?
Big slam
Relive one of the moments from the French Open with this spot the difference game…
If you are a lover of tennis, then you would know that the 125th edition of the French Open concluded recently. The French Open is one of the four annual Grand Slams of tennis (the other three are The Australian Open, The US Open and Wimbledon). In Europe, the French Open is more commonly known as ‘Roland Garros’, named after a French aviator and fighter pilot during World War I.
This year, once again saw remarkable competition. The Women’s Singles was won by Barbora Krejčíková from the Czech Republic while Novak Djokovic from Serbia won the Men’s Singles, making it his 19th Grand Slam win and just one short of tying with Roger Federer and Rafael Nadal for the most Grand Slam wins.
It’s ok if you weren’t able to catch any of the matches; the Wimbledon is set to begin soon. In the meantime, here is a small highlight from the French Open Men’s finale. Compare the two pictures and see if you can spot the differences.
Musical trails
Music has no language and, indeed, no boundaries! Learn about some genres from countries across the world.
When it comes to music from different parts of the world, genres such as salsa, tango, samba, and even K-pop probably come to mind. This World Music Day, go one step beyond the widely popular styles and discover some new genres from countries around the world. You may just stumble upon your new favourite music!
Click on the hotspots in the map below.
Olympian facts
It’s International Olympics Day! What is this day all about? Find out…
June 23 is international Olympic Day; however, it is most commonly known as ‘Olympic Day Run’. This is an international Olympic Movement to promote competitive sport as a revival of the ancient Olympic Games. The day aims to promote the Olympic Games while encouraging more people to participate in sports and explaining why incorporating it into their lives is important. The occasion marks the day when International Olympic Committee was founded in 1894.
To celebrate the day and the 2021 Summer Olympics, which is being held in Tokyo next month, go through the cards below to learn some interesting facts you might not have known about one of the biggest sporting events.
Turn the cards over to read the fact.
What is the end result?
What is your actual experience of redundant phrases during the course of your conversation? Can you find the number of times the same idea has been repeated?
Ask a question and, as an added bonus, you will get a free gift.
What do you think is wrong with this sentence?
To ask is to pose a question, so question is redundant. A bonus is an extra feature, so to say added is unnecessary. And, finally, if you had to pay for something it is not a gift.
In our conversations, we often use phrases like this. Can you complete the phrases in these cards?
The Man and His Machine
On Alan Turing’s 109th birth anniversary tomorrow, learn more about the scientist whose work led to the development of the computers that we know today.
Mathematician, computer scientist, crypto-analyst, philosopher, theoretical biologist… Alan Turing was all this and more. His work laid the foundation for the foundation for the development of computers and Artificial Intelligence. Check out this timeline to know more about him.
All that glitters
How much do you know about the world’s most precious gems? Find out here…
Gold glitters, silver shines, and gems…. well, they sparkle. How much do you know about them? Try your hand at this crossword to find out.
Get set, yoga!
On International Yoga Day, here are four simple poses or asanas that you can start with to help boost your health.
June 21 is observed as World Yoga Day. It is a day dedicated to raising awareness about the benefits of the ancient physical and mental practice that originated in India.
This is especially useful during the COVID-19 pandemic that is affecting the physical, as well as the mental health of people caused by fear, anxiety, and social isolation.
Yoga is really for anybody – irrespective of age and physical ability. Here are four simple poses or asanas that you can start with to help boost your health.
Images courtesy: Taamara Rasa Yoga Studio
My Monthly Planner: July 2021
Discover interesting facts about Tropical and Exotic fruits and download your own calendar to keep yourself organised.
