Category: Physics

By Anupum Pant

This one is a tough one to wrap your head around but it is amazing. Haven’t you ever thought why mirrors flip everything horizontally and not vertically. Like if you raise your right hand the mirrored image of you raises its left hand…and it doesn’t instead put down the hand. The vertical stuff remains the same, while the horizontal stuff gets inverted.

A mirror is the same in the vertical direction and the horizontal direction. Nor does it have a mind of its own. So, how does it figure out what’s horizontal and what’s vertical? Or does it?

Try this. Hold an arrow in front of the mirror. Point it right, the mirror does the same. Left, up or down, the mirror does the same. That’s it. Now point it towards the mirror, the mirror points towards you. So, it’s the z axis that gets inverted. If you think about it, it is pretty amazing!

Physics girl explains it much better in her video…

By Anupum Pant

Take a glossy black ceramic bowl and fill it with water. Now place it in the middle of a rotating wheel. What do you get?

Thanks to the complex play of centrifugal forces creating a gradient of forces as the function of radius, with earth’s gravity also doing its part, you get a parabolic shaped water surface. If this liquid you use is a liquid metal like mercury, or Gallium (at slightly higher temperatures), you’d have a parabolic mirror in a bowl.

Depending on the speed of your rotation, you can adjust the focal length of the mirror. That’s because the faster you rotate this wheel, the deeper mirror you have and the focal length is smaller. There, you have your own adjustable parabolic mirror.

A great thing about such mirrors is that they can focus parallel rays to a focal point. And this is what telescopes rely on. Large telescopes have large lenses, and it gets incredibly expensive to make these mirrors. So there are telescopes which use a liquid parabolic mirror like the one described above. However, their mirrors are huge.

This idea originated from Issac Newton, but he wasn’t successful in making a smoothly rotating platform. Quoting wikipedia…

The concept was further developed by Ernesto Capocci of the Naples Observatory (1850), but it was not until 1872 that Henry Skey of Dunedin, New Zealand constructed the first working laboratory liquid mirror telescope.

In fact, huge solid mirrors used in telescopes are also made using a similar method. That is to say, the melt is spun like this and is solidified.

via [Wikipedia]

By Anupum Pant

In most cities when gunshots are fired, the police firstly never hear them go off. Even if they do, they try and go everywhere to see where it came from. By the time they reach the actual spot where it was fired, it is too late. The perpetrator has left.

But the police department of DC uses a 1.8 million dollar system called the shotspotter which comprises of several microphones dotted all over the place which can detect gunfire. But that’s not all.

A gunfire almost always has three microphones which are closest to it. So these three microphones work in harmony, detect the difference in time it took the sound to reach them and triangulate the exact spot where the gun shot was fired. They can do it with an accuracy of 25 metres. That I think, is money well spent.

The shotspotter system has several other features built in. It, after facing initial problems, can now say for sure if it was a gunfire, and not a firecracker. Besides that it can also tell officers the direction towards which it was fired. And the kind of gun it was fired from and so on…

via [WashingtonPost]

By Anupum Pant

I’m not even sure if this is for real. It sure does look real. But there’s also an equal possibility that there was a cut in the video after the plane was thrown and then a plane tied to a suspended thread is shown. Anyway, here’s how to make your plane fly forever in your own home. All you need is paper and stove.

By Anupum Pant

A check valve is a no return valve. That means a fluid flowing through it in one direction flows well, but it doesn’t flow in the other direction. Check valves are parts of several household items. They are also used widely in many many places in the industry. Cranes, pumps, and even your heart couldn’t work without a check valve.

All check valves have a moving part called the obturator which closes the valve when there’s a flowing in the reverse direction. Or that is what most people think. But there’s a check valve that Tesla patented which had no moving parts.

Agreed, it is not the best of check valves and has also has turbulence issues which is not good for any hydraulic system. But it sure is an awesome idea.

By Anupum Pant

Ted Taylor was a celebrated theoretical physicist and a great nuclear bomb designer. It’s not very well known, but he was also the first person ever to light a cigarette using a nuclear bomb. How is that even possible you might think. But geniuses like Ted are quick to figure their own ways…

On June 1st 1952, a 15 kiloton nuclear bomb was to be tested in a northern Nevada town, Elko. At 3:50 in the evening, all the troops and researchers were tightly snuggled in trenches, waiting for the fission bomb to go off. Ted however had a plan to do his own little test.

He had a cigarette, and a parabolic concave mirror that he found a few days back and decided to bring along in the trench. Using a tiny wire, he suspended the cigarette and aimed the parabolic mirror towards the intense bright light that would come out of the fission reaction when the bomb would go off. It was all arranged in such a way that the bright spot would concentrate on the tip of that cigarette.

The bomb went off, sent a 37,000 feet tall mushroom cloud and a 41 mph wind in all directions. The intense heat from the fissile material, as calculated by Ted the last day, got focussed on the tip of that cigarette and lit it within a second or two.

Ted was now known as the man who lit a cigarette using a nuclear bomb. That little personal project of his brought him great reputation and he went on to do other great projects.

The cigarette, as soon as it was lit, got stubbed by Ted, and was preserved to be displayed on his table. It indeed was a pioneering work – a nuclear bomb powered cigarette lighter. However, while working on some other project, not paying much attention to what was going around, he smoked the reminder of his great feat.

via [Under the Cloud]

By Anupum Pant

Does quantum entanglement make faster-than-light communication possible?

We know the entangled particles must have undefined spins before we measure them because if they didn’t they would sometimes give the same spin when measured in a direction perpendicular to their well-defined spins (and they never do).

We know the entangled particles can’t have hidden information all along about which spin they will give in different directions because if they did we would measure different results at the two detectors >5/9ths of the time and we don’t – we only get different results 50% of the time.

We can’t use this behaviour to communicate faster than light because we can only pick the direction to measure in, we can’t force the spin to be up or down – and it will be random with 50/50 probability. When the two detectors pick the same direction to measure in the results at one detector will be random but the opposite random of those measured at the other detector, which is a bit spooky. – via Veritasium

By Anupum Pant

If you think about it, wouldn’t it be a great idea to make a home heater that would make humans feel hot without wasting energy to heat the air that surrounds them. Just like a microwave oven cooks meat without heating the surrounding air, this should in theory work to warm humans with smaller intensities, so they don’t get cooked. I know people are just too paranoid about microwaves, but trust me they are not that bad. But how safe can a microwave home heater possibly be?

This is what a Harvard physicist suggested in the 80s. At that time, according to Professor Robert V. Pound, microwaves could certainly be used to just make the humans feel the warmth, without heating the whole air in the house. This according to him, would cut electricity costs greatly and might serve as a great tool to deal with the world energy crisis. This article of his got published in the journal of science.

He said:

If a microwave oven is installed in a house, the waves would heat the people and not the air. So with the surrounding air remaining at low temperatures, the humans would still feel toasty.

A Harvard physicist said that. How wrong could an accomplished person like that be? Well, doctors urged you to smoke cigarettes in the old times. So, there is a lot he could have gotten wrong at that time. Also, since I haven’t come across any homes installed with microwave heating, even if they purportedly could offer a much cheaper alternative, there must definitely be something wrong with the professor’s idea.

This is what I think. Firstly, if anything like that was even possible, the whole house would have to be covered with metal foils to keep the waves in. Also, every thing in the house would have to be microwave safe. With electronics and silver ware of all sorts, that possibly doesn’t seem like a very good idea any more.

That is not even what could be the most wrong thing about it. The microwaves wouldn’t heat the whole human body uniformly. With the body containing different amounts of water, they’d certainly get heated differently, with different rates. In my view, if there’d be something like that, due to the high water content, your eyes would pop first.

And then all your tech, made of metal etc. would have to be microwave safe. No, that’s not happening.

via [Freelance star]

By Anupum Pant

Unless you stand there and keep stirring your boiling noodles, or pasta, they might stick to the bottom of your pot. Also, lumps of cornstarch are a mess the other times when you are trying to thicken gravy without putting much effort into stirring the sauce. All of that extra effort of standing there and stirring stuff can be eliminated if you incorporate this pot designed by a Japanese dentist, Hideki Watanabe. He calls it Kuru-Kuru Nabe (Round-Round pot).

The dentist designed a pot that can stir up the water inside it without you having to interfere. The interesting part here is that the pot doesn’t have any moving parts, neither it uses electricity to keep your water spinning. It’s the special shape of it that accomplishes this. The abnormal grooves this pot has on its walls keep the water spinning when it is hot.

My theory on what makes it work is – Leidenfrost effect happening at the walls. Like we’ve seen in the past that hot water can climb slopes using the same effect, it probably does the same here. Anyway, here’s what the pot looks like when it’s cooking.

via [InventorSpot]

By Anupum Pant

There’s much more to a rainbow than it is usually told to us in our basic science classes. There are double rainbows, complete circular rainbows and what not. Physics girl explains…

For example, have you noticed that the sky above the rainbow is darker, while under it the sky is brighter. I didn’t know that! There’s complex combination of reflections and refractions taking place inside droplets which causes this. I can’t even explain it in text.

It doesn’t stop at double rainbows. Did you know, if it wasn’t for the sun;s mighty glare, you might have been able to see tertiary and quaternary rainbows too. Stacker rainbows are for some other time…

By Anupum Pant

A golf ball is full of those cute dimples. Wouldn’t it have been better if they were clean and smooth with none of those tiny little bumps on their surface. Do these tiny bumps even really serve a purpose? Turns out, they do!

On a normal golf strike, a smooth golf ball would have reached 130 yards at most. Whereas a dimpled one travels more than twice as much – About 300 yards. What makes the difference? The dimples, of course. Aerodynamics!

A smooth ball has no lift. A dimpled one on the other hand is able to create a turbulent flow around it which provide it with a significant amount of lift. Such a ball can easily reduce the drag created by the air around it and is able to fly for longer.

The size, shape and number of dimples on a golf ball affect the amount of drag force it can reduce. So, different manufacturers have different parameters for their golf ball dimples. The more number of dimples you have, the more number have to fit on the ball’s surface and more desirable it is to reduce the drag. That means, each dimple has to be small and a point is reached where there are so many dimples that the ball is effectively a smooth one. So a sweet spot needs to be hit in order to optimise the flight of the golf ball.

The sweet spot lies somewhere in between 300 – 500. So, any ball with number of dimples less than 300 or more than 500 is not optimised for performance. So, most manufacturers have around 350-450 dimples on their golf balls. 336 dimples is believed to be a totally optimised number. Others believe that it has to be more than 380.

Back in the day when people did not really know about this, they had smooth balls and the flight of such a ball was something they weren’t impressed by. So now they had scratched golf balls, and then we had balls with dimples.

By Anupum Pant

If you hold a long piece of dry spaghetti from the ends and bend it till it breaks, something unusual happens. Almost always the strand breaks into three pieces. Sometimes even four, and more. Statistically, very rarely it breaks cleanly into two parts.

The answer to why this happens has troubled physicists for a long time. Still not much is known about this phenomenon. Richard feynman had his own theory explaining why this happens. Until now, it was believed that the vibrations from the first fracture cause the second fracture. But that doesn’t seem to be the mechanism if you see it at very high frame rates. Because the second fracture happens much before the vibrations from the first reach it. [Paper]

This work of spaghetti breaking also lead to the 20006 IG nobel Award.

Smarter everyday, a youtube channel, to find out how this happens, decided to delve deeper into this and did an experiment that has never been done by any one else. The host captured it in slow motion at quarter million frames per second.  Before this, people had gone upto 4000 frames per second. 4000 FPS doesn’t really give you a lot. But when the frame rated is kicked higher, the mechanism sort of starts becoming clearer.

Both fractures, if it braeks into three, takes place with a very small interval in between. And now, thanks to this extreme slow motion video, it is believed that the first fracture triggers the second fracture.

By Anupum Pant

Think about this. You have a glass full of water, with water nearly till the rim and then you have a mug full of beer, with its foam almost reaching the edge. Carrying the glass full of water in your hand from one end of the room is clearly more difficult than carrying the mug of beer that has foam in it. I have always thought that this must be due to the difference in viscosity of both the fluids. But what if one had beer with no foam and other had beer with foam in it?

Turns out foam plays a big role in determining if the liquid spills on shaking the container, or not. It’s much easier to spill beer with no foam on it or even a glass full of water, or a glass full of coffee (with no foam of course). But when you have foam on your drink it is much harder to spill it.

That is because walking with a liquid that has no foam on it lets the waves propagate easily, without any resistance. However with a liquid with foam on it has to go through the resistance from the foam to propagate waves on its surface. This makes it harder for the liquid to spill.

Some researchers at Princeton university are studying the actual physics involved in this “anti-sloshing mechanism” of foam on liquids by studying the motion of foam bubbles using a high speed camera.

By Anupum Pant

Have you ever tried dragging a plate (the one you use to eat food) on the surface of a swimming pool? If you haven’t, you’re missing out on something really cool.

Dragging a plate across the surface of a pool creates a toroidal vortex in the water which, thanks to the combined play of friction and pressure, keeps it going for a long time and long distance. Dolphins, volcanoes and human smokers all do it. It’s a perfect way to create disturbances in fluids  which can travel relatively long distances – the whole length of a pool in this case. A vortex travels slow usually in the perpendicular direction of its plane and could take several minutes to traverse, say the length of a pool. But, if done right, it won’t die out easily.

Another interesting thing to note in the plate and pool experiment is that there are two vortices created, each at one end of the plate. Both of them  travel together and seem to be rotating in opposite directions. So what really are these?

This is how it works.

Think of it as a curved tornado, a semi circular one created across the whole semicircular part of the plate which is inside the water. Here’s a creative way to see this half toroidal vortex in action.