Brian Cox Introduces You To Quantum

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Here it is: a lifeline to get you through this Pop Physics drought. Professor Brian Cox, host of the excellent BBC series Wonders of the Universe, delivering a fun and insightful introductory Quantum Physics lecture. Complete with celebrities like Simon Pegg, a million-pound diamond, and a breathless northern English accent. Professor Brian Cox: A Night … Read more

A Real Perpetual Motion Machine, in the Wild!

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Somewhat coincidentally, I just came across this video of a supposed perpetual motion machine / free energy device via reddit. It’s a coincidence because my last post was all about perpetual motion and why it’s impossible. It may seem like a bit of an archaic problem to tackle, but as the popularity of this video shows, these things still pop up from time to time in real life. This one uses magnets, as most self-respecting perpetual motion con artists do these days.

My favourite part is in the video description: “This technology has been suppressed because it is a threat to the profits of the energy corporations.” Not sure how those tricky energy corporations haven’t managed to get this video taken off YouTube yet, but I suppose it’s only a matter of time.

So why doesn’t it work?

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5.4 Perpetual Motion Machines

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Critical Question:

  • What are perpetual motion machines, and why are they impossible?

There was an episode of The Simpsons in which Lisa made a perpetual motion machine, which angered Homer because “it just keeps going faster and faster.” Later, he called her into the room and yelled, “In this house, we obey the laws of thermodynamics!”

homer perpetual motion machine
Man, what won’t Homer say next?

He had every right to be angry, but Lisa is not alone in her fascination with the idea of a machine that never stops. As we’ve already seen, motion requires energy, and energy isn’t always easy to come by. But if we had a machine that could keep moving forever without assistance, the possibilities would be endless.

Alas, this is one of those cases that really is too good to be true.

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5.3 Conservation of Energy

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Critical Questions:

  • What is energy?
  • What do all of the different types of energy have in common?
  • How do we use food to move ourselves around?

Now that we’ve described a bunch of different types of energy (in the previous post), we can talk about how they behave. Following on Mr. Feynman’s comments, each of these types of energy has a very specific mathematical formula, so we can calculate exactly how much of each type of energy we have in a given situation.

The most interesting thing about energy is this: it cannot be created or destroyed; it can only change forms.

I’ve already hinted at this idea when talking about the examples from the previous post. Any kind of potential energy can turn into kinetic energy when the object in question is free to move. The simplest example involves one of those wind-up toys you probably had as a kid, or at least you probably saw them in old cartoons.

caterpillar wind-up toy
I like this one because it’s a happy caterpillar.

To make these toys work, you turn a little crank; this tightens a spring inside the toy, which means that you have increased the toy’s elastic potential energy. When you let go of the crank, the spring turns some gears, which cause the toy to spin, or walk, or drive away. Whatever it does, it’ll probably move somehow – in other words, it’s gained kinetic energy. But meanwhile, the spring is no longer wound up, so it’s lost all its potential energy.

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Using Ancient Ovens to Trace the History of Earth’s Magnetic Field

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Scientists have known for some time that the Earth’s magnetic field has undergone significant changes throughout the planet’s history. In fact, about once every few hundred thousand years, it completely reverses – what was once magnetic north is now magnetic south.[1. The planet’s magnetic poles are a small distance away from the geographic poles, which … Read more

Voyager’s Photos: Our Message to Space

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Ok, I really should be getting on with the chapter on Energy, but I just had to post this.

Voyager 1, a space probe the size of a small car, will soon become the first human-made object to leave our solar system. Launched in 1977, it is still – amazingly – sending back new data about the mysteries of outer space 10 billion kilometers away, more than 35 years later.

Great Red Spot From Voyager 1
Jupiter's Great Red Spot, photographed by Voyager 1.
Voyagers 1 and 2 flew past Jupiter and Saturn, taking photos on the way. (Voyager 2 also went by Neptune and Uranus, but its path slowed it down a bit, meaning Voyager 1 is now farther from us.) Then they headed out towards interstellar space with the hope of being found, someday, by intelligent beings. Both probes were equipped with a golden record, which contained music, sounds, and images, as well as instructions on how to properly play the disks. (For more on the audio side of this project, you should definitely listen to this wonderful episode of Radiolab.)

The reason for today’s post is this gallery of images from the records, which I always find mesmerizing.

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How Galaxies Are Formed

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I wanted to take a quick break from discussing the mysteries of energy to share a mesmerizing video. This NASA-created computer simulation illustrates how moving clouds of dust created in the Big Bang could accrete into the spinning collection of billions of stars that we call a galaxy. “This cosmological simulation follows the development of … Read more

5.2 What is Energy?

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Critical Questions:

  • What is energy?
  • What do all of the different types of energy have in common?

Despite its abstract and purely mathematical nature (as discussed in the previous section), we’re still going to have to come up with a good definition of energy for the purposes of this site.

The term ‘energy’ in physics means something very similar to what it means in everyday English. If you’re lying in bed and you don’t have the energy to get up, you may actually be lacking in something that could be equated with the scientific idea of energy. (Or you could just be a slothful person.) We would also say that it takes energy to light up our homes and to drive our cars, and this usage fits with the physics one as well.

Solar Flare
The best kind of energy: magic (i.e. solar flares)
Already we can see that energy has a lot of different forms – your ability to get out of bed is quite different from a car’s ability to drive down the road, for example. And yet they all have some shared quality in order for us to be able to use the same word to describe them. We do have some excellent mathematics to help us define that similarity, but for now I’d like to propose a loose definition – one which is simplified almost to the point of inaccuracy, but which will nevertheless allow us to come to a better understanding of the topic.

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5.1 Introduction to Energy and Heat

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In my experience, the subject of energy tends to be badly taught in lower-level physics classes. I’ve met a lot of students who, when asked what energy is, can promptly recite the following answer: “Energy is the ability of a system to do work.” Continuing with this website’s theme of trying it yourself, I recommend that you take a field trip to the nearest university campus or high school science class and perform this very experiment, and watch the pride in the students’ eyes as they prove their intelligence to you.

sunshine, flowers, windmills, and solar power.
Fig. 12C: Windmills are just really big, genetically altered sunflowers.

But if you want to throw a bit of a wrench into things, try following up your first question with another: what is work? Many students will frown slightly. Some will say that it is a force exerted over a distance. Others will simply shrug and point at the formula. In other words, most physics students don’t really understand what energy is.

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