This Is Why … Romanesco broccoli is the nerdiest veg (IMHO)

“Roman Cauliflower” by Federico Galarraga is licensed under CC BY-NC-ND 2.0 

Broccoli can be something of an acquired taste, with children everywhere staging dinner-table standoffs with their parents over this dreaded veg. But whether you like the taste or not, it’s hard to argue with the aesthetic appeal of this particular variant – the Romanesco broccoli.

On closer inspection, the distinctive spiral is actually a repeating pattern. If you cut a piece off and zoom in, it looks exactly like the main head it originated from. Mathematicians call this a fractal, and this self-similar repeating feature can be see in everything from the formation of ice crystals on a frosty windowpane to the network of veins that provide nutrients in leaves.

Technically, the Romanesco broccoli is only an approximate fractal because, in the true mathematical use of the word, a fractal must repeat infinitely. For example, the classic Koch snowflake (below) is created by superimposing equilateral triangles on top of each other in very specific ways. When you repeat this process again and again, the resulting shape has an infinite distance around its edge, but a finite volume inside.

Koch snowflake gif by Leofun01 / CC0

This all sounds delightfully trippy, and the resulting patterns are mesmerizing to look at, but what does this have to do with real life, other than providing you with an incredibly geeky factoid for your next social gathering?

In addition to finding these amazing structures in your refrigerator and on your windowpanes, the human body has them too. We are full of complicated structures and trying to model these with regular everyday shapes (spheres, cubes, etc.) is not going to be very successful. We need something a little more sophisticated than that, which has led scientists to apply fractal analysis to certain structures, such as the branching of the airways inside our lungs. A team of Japanese scientists recently used fractals to understand the complexity of small growths in the lung that were suspected of being cancerous. By combining this fractal math with standard imaging techniques, the ability to distinguish between malignant and benign was significantly improved.

So, the next time you’re in the produce section of your grocery store, reach for some Romanesco broccoli. Will it win over the kids? Maybe not. But it will give you a great dinner-table conversation starter!

This Is Why… penguins can fly!

(but the landing isn’t pretty)

Emperor penguins are portly creatures. That’s a good thing – all that bulk is a great way to stay warm when it’s -30°C. The downside (pun intended) is that they are not the most nimble of birds when moving around on the ground, especially since they have relatively short hind limbs. Nor can they fly (in the conventional sense), so it would seem that penguins drew the short straw in the birdly attributes department. But, given that their food and their predators are in the water, being nimble swimmers is really the key to their survival.

If you’ve ever been to a zoo or aquarium, you’ve probably been transfixed by the speed of these amazing creatures as they zig-zag through the water. Their cruising swim speeds are about 2 m/s, similar to the steady pace of about 3 m/s of a typical marathon runner. Obviously they are capable of much faster bursts to catch prey or deke out a predator, but how do they get out of the water in a hurry? If there’s a pod of hungry orca on their tail, the safest place is on the ice surface above. They need to be able to leap out and clear the edge convincingly so they don’t slip back into waiting jaws below. Awkwardly clamouring out at the water’s edge is just not going to cut it.

Bubbles to the rescue! When at the surface, penguins often preen and groom, filling up their plumage with air. When they dive, that air is compressed by the increasing pressure. If they want to escape the water in a hurry, they dive to a depth of about 15 to 20 m and squeeze that compressed air tightly against themselves. When the penguins start to climb, the air wants to expand again, but it can’t. The result? Tiny bubbles of air sneak out through the mesh of feathers all around the penguin, creating a column of bubbles for the tuxedo-wearing torpedoes to rocket through.

By creating a tiny air layer around itself, the penguin lessens the drag of the seawater, reaching launch speeds that are 3 to 4 times their regular cruising speeds. This is more than enough to beat the force of gravity as they leave the water, sending them flying through the air, bellyflopping to safety. Engineers have been experimenting with the use of microbubbles to reduce drag in the shipping industry since the 1970s, with modest success. Another example of the animal world applying physical principles more expertly than the human experts.

An amazing video from the fabulous National Geographic team can be found here:

This Is Why … auroras are only found at the poles

Photo by stein egil liland on

If you’ve ever had the pleasure of seeing the northern lights in person, you know that words do not do them justice. The auroras (aurora borealis in the north, aurora australis in the south) are beautiful and haunting, moving across the night sky as ethereal light. The displays are typically green, but occasionally you’ll see hints of red, pink, or purple. Why do we only see them at the extremes of our planet – near the poles – and why these specific colours?

Our planet, as well as others in the solar system, is constantly hit by high-energy charged particles from the Sun, known as the solar wind. Think of it as the price we have to pay for all that heat and light we get. When these particles pass through our atmosphere, some of them smash into the molecules they find there, transferring their energy to these gases. This extra energy then gets released in the form of light, with the different gases in the atmosphere giving off different colours of light. For example, green light is mainly emitted by oxygen.

But why do we typically see this spectacle close to the poles? More physics! Our planet has a magnetic field, which is incredibly useful for navigation. It turns out that it is also incredibly useful for protecting most of the planet from these solar winds. When the charged particles enter Earth’s field, our magnetic protection redirects the charges in such a way that they travel around the planet towards either the north or south pole. Instead of crashing straight through the atmosphere, partially giving energy to the gases there and generating an aurora, partially getting through to the surface, the charged particles are pushed aside like raindrops hitting the top of an umbrella. When they reach the poles, Earth’s field is no longer able to redirect the charges[1], so they plunge through the atmosphere creating this iconic luminous display.

A little physics, a little chemistry, and solar winds that have traveled 150 million kilometres become dancing ribbons of light in our far north and south.

Video by Distill from Pexels

[1] At the poles, Earth’s magnetic field is parallel/antiparallel to the direction of the charged particles’ velocity coming in through the atmosphere. When the field and the velocity are in the same direction, there is no magnetic force applied to the charged particles – they have to be travelling a bit at an angle to the magnetic field in order to experience a redirection force.

This Is Why … I’m Writing

Let’s face it, physics has an image problem. If we were to play a little word association game, what are the first words that comes to mind when I say “physics”?

  • boring
  • hard
  • math-y (i.e. see points 1 and 2!)

Or, if we play an image association game, what are the first things you picture when I say “physics”?

But here’s the thing – physics is so much more than cosmology and quantum computers, and you don’t have to be ‘Sheldon-Cooper smart’ to appreciate it. Fundamental physics principles help us to understand everything from how the heart pumps blood through the circulation system to why soap films form spheres when you blow air into them.

This is why I write: I love that a surprisingly small set of fundamental physical principles can explain the ‘why’ of just about any everyday phenomenon. I want to share that with anyone who will listen. The world is full of incredible examples of physics in action and you don’t need a PhD in quantum mechanics to appreciate them! And, although I feel a little late to the party in starting this blog now, I’m taking inspiration from something I saw at #SciCommTO 2020:

by Michelle Rial