Monday, December 3, 2012

Top 4 Questions You Never Knew You Wanted to Ask

Welcome to the latest Science for Writers post. Last time we discussed the Nobel Prize winners in Peace and Economic Sciences. In this post I will be doing a quick fire of the top 4 questions you never knew you wanted to ask. The questions are a mix of those you thought too obvious to even contemplate asking and those that just weren't even on your radar.

I have put important words in bold. These words are important in science and I will refer to them throughout the post. It isn't overly important for you to know the exact meaning, so long as you get the gist of what I'm talking about you will be fine following this post.

Writing Links are in italics and these discuss how the science could be used in writing.

Why Does Salt + Water = Pain?

In this video we see a bunch of idiots doing the Salt and Ice Challenge. Before I even go into the science of this I think I should take a moment and say not to try this at home, though I doubt you'll want to after reading the background to this challenge.

Let's think a bit about what they're actually doing here. They pour salt onto their hands, add an ice cube, and squeeze; seems harmless enough. But then they start crying out in pain and laughter. The laughter is likely because they don't want to cry in front of their friends, but the pain ... the pain is definitely real. To give them credit, they lasted longer than some other people on YouTube doing this challenge have.

So, why does squeezing salt and ice cause pain? Well it's to do with the type of reaction happening. In this case it is an endothermic reaction. That means it takes energy in from its surroundings, which in this challenge in the person's warm hand. The salt wants to react with the water in the ice. When it does the ice will melt at a colder temperature. This is why we grit roads with ice in the winter; the ice will melt despite the colder temperature. But doing that means it draws energy from your hand, much more than just normal ice would.

But why does it burn if it's getting colder? Those burns are frostbite. When you do this challenge you give yourself second degree (and sometimes third) frostbite burns that take weeks to heal and can leave a permanent scar.

Incidentally, if you did this on a hot day, you wouldn't need the salt. If you're really sweaty and press ice against your sweaty areas the melting point of the ice is lowered and the same result occurs. So, you can actually get frostbite in the summer!

Writing Link:  Endothermic reactions take in energy. Perhaps magical objects are endothermic and draw magic from the beholder. Maybe this salt and water trick could be a nasty way to torture a character? The opposite is exothermic which means the reaction gives out energy; an explosion is very exothermic.

Why does stuff knot when I'm not looking?

Knotted Cable
Knotted Cables
Image Courtesy of The Washington Post
It is a problem that plagues anyone who owns anything with any degree of flexibility:  wires, rope, string, long hair, hose pipes, tinsel. Stuff knots together for no apparent reason. We put a two wires in a draw separately and yet they come out entwined in some kind of weird wiry embrace. They were not together before, but they are now despite not having been moved at all.

It all comes down to a seemingly innocent word, entropy. Entropy is the word used to say 'everything gets more chaotic as time passes'. So, in the case of wires they just want to get more disordered. Being straight and organised is unnatural and they are more likely to get tangled as that is known to have a higher entropy.

There are more ways 2 wires can be tangled in a given space than there are untangled. In a small space there are only so many ways the wires can be and the vast majority of those combinations are tangled. In a large space 2 wires have many more ways to be and so there are more ways for them to be untangled. Imagine a drawer with some wires in. There's hardly any space and so the wires, according to the laws of entropy will be more likely to get tangled as there are more possible combinations of tangled wires than untangled  Now imagine a field. There are a million times the number of possible arrangements and most of them are untangled.

Writing Link:  Things get more chaotic. Apply this principle to plotting and character and you get interesting stories. Adding more characters and back story increases the number of ways things can be arranged. Over time stuff gets chaotic, so should your stories. Start off simply then get more and more chaotic - who's the imposter? who's been killed? who's safe?

Why don't I fall through the floor?

Sometimes we take things for granted. Not falling through the floor is one of those things. Think about the question for a moment. Is it that stupid a question? Consider that everything is made of atoms and atoms are 99.9999999999999% empty space and that in day to day life we can drop stuff through empty space.

body through floor
Body through floor
Image courtesy of The Sims 3 Forums
To answer this question we need to think about the atom. The atom has 2 main parts - the nucleus (protons and neutrons), and electron 'shells'. For the purpose of this question we can ignore the nucleus.

Electrons have a negative charge. When two electrons meet it is 2 negative charges meeting. Using magnets as an analogy we know that opposite poles attract and like poles repel. If we think of 2 negative charges being like 2 south poles of a magnet meeting we can predict what will happen. They will repel each other.
Electrons orbit the nucleus (but are much, much smaller than this image suggests)
Image courtesy of ZME Science

What happens is the electrons in our body repel the electrons from the floor and that holds us up. This is because this force is much stronger than gravity, which really doesn't take much as gravity is the weakest of the four forces.

Writing Link:  What would happen if a device could somehow remove all electrons from two objects? You could theoretically make the two things fall through each other, but without electrons the object would just fall apart so falling through would be pointless as the object would be destroyed. But if you're writing sci-fi you could invent an electron remover with built in stabiliser to make objects pass-through-able.

How much wind does it take to bend a bridge?

Turns out, not much. "But wait!" I hear you cry, that bridge is swaying loads - there must have been loads of wind. I can assure you there is not that much wind, in fact if there were much wind the bridge wouldn't have collapsed. Galloping Gertie was not caused by high winds.

If you still don't believe me look carefully at the video:  watch the trees in the background. If it were really windy they would be swaying too. The bush near the bridge is moving because of the wind produced by the bridge. The trees in the background aren't moving much at all.

This is a great example of a phenomenon known as resonance. What that means in technical terms is that the forced oscillation matches the natural frequency of an object. Every object has a specific frequency at which it likes to vibrate. If something external acting on the object, in this case a gentle, but consistent breeze, matches this almost perfectly then the object will oscillate with that frequency. When this happens the amplitude, that is the how high/large the movement it, will slowly increase. This graph explains the effect:

natural frequency
Natural frequency plotted against amplitud
Image courtesy of Physics Net
As you can see when the natural frequency, fo, is reached the amplitude is at its highest. When the bridge was swaying back and forth at its natural frequency for so long the structure began to fracture and it eventually collapsed.

Nowadays, civil engineers design bridges where the natural frequency is either unnaturally low/high and/or varies at different points along the bridge.

For those that are interested, the car on the bridge had a dog in it. The owner crawled to the car to save his dog, but the dog wouldn't get out so the owner had to leave him. When the bridge collapsed the dog and car went into the water, but the dog miraculously survived and was reunited with its bewildered owner.

Writing Link: Many fantasy stories are set in medieval times where things like natural frequency aren't understood. What would happen if there was a consistent breeze that matched the natural frequency of a key bridge? Would they blame magic users? What impact would it have on the economy?

So, there you have it, four questions you had never even thought of asking. That's it for this post. Please comment on this post below; I'd love to here from you. Share this post if you enjoyed it. There are social media buttons at the bottom of the post for your convenience.



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