Can't Touch This

A surprisingly common notion that comes up in science popularization is that nothing ever touches. This comes up things from youtube videos to the remake of Cosmos. As far as the scientific facts go, they're right. When you touch something, say when you pick up a ball, the electrons in the atoms of your fingers repel the electrons in the atoms of the ball, so the atoms in your fingers never come near the atoms in the ball. Near, that is, relative to the size of an atom.

But I wouldn't say that means nothing ever touches. Rather, it's a microscopic description of the macroscopic phenomenon of touch.

As an analogy, consider temperature. You can feel temperature as things feel hot or cold. You can measure temperature with thermometers. You can come up with laws that describe how heat flows from hot things to cold things. But on a microscopic scale, temperature is just speed. When atoms and molecules vibrate faster, they're hot. When they vibrate slower, they're cold.

But that doesn't mean that temperature doesn't exist. Rather, that's what temperature is. Thermometers still work, and the laws of thermodynamics are still accurate. They just refer to an emergent property of a complex system, rather than fundamental property.

I would argue the same applies to touch. Electrons repelling each other is what touching is.

Admittedly, this is entirely an argument over semantics. It's just about the definition of the word "touch", rather than any actual facts. But I think this definition is better and more useful. Because if nothing ever touches (except maybe where fusion occurs, like in the heart of a star), then the word "touch" never makes any useful distinctions, which is the purpose of a word.

Folk Morality

Folk science is pre-scientific ideas about how the world works. For example, a common idea in folk physics is that an object in motion requires a constant force to stay in motion, and if the force stops being applied, the object will soon come to a halt.

Now, folk science is not always wrong. It actually tends to be very good at predicting what happens in everyday circumstances. If you're pushing a cart, the carts stops moving when you stop pushing. It's when you leave everyday circumstances that folk science fails.

I think the same idea applies to morality. Folk morality is what people generally use when making moral decisions. It doesn't have any kind of rigor or theory behind it, but in everyday circumstances, it works alright. Don't lie, don't steal, don't kill.

The biggest problem with this idea is that folk science is based on things that can be directly observed. Folk morality doesn't seem to be. As a result, it's much more prone to differ between cultures and eras. For example, two hundred years ago, slavery was common and accepted, but it isn't today.

Viewer's Guide to the ISS

Did you know the International Space Station is easily visible to the naked eye? In fact, at it's brightest, it can outshine Venus! The problem is that it moves very fast (17,130 mph) so you need to know when to look, or you'll miss it.

So, how do you know when the ISS will be overhead? One great resource is Heavens-Above. It will tell you exactly when the ISS will be visible, how long it will be visible for, and where in the sky it will be. It also has information on lots of other satellites and other things of astronomical interest.

But sometimes it will be months before the ISS passes over your location at night. You'll need some kind of reminder after that long. That's the purpose of Spot The Station. Sign up for it, and it will send you an email 12 hours before the next sighting.

There are also apps for mobile devices that are very useful. A good one I just got is ISS Detector.

Also worth mentioning is Wolfram|Alpha. It's less practical for finding good viewings, but it has lots of interesting information. Not just about the ISS, not just about satellites, not just about astronomy, it knows about pretty much everything.

So, go out and look at the sky. It's an awesome place.

Ode to the ISS

Tonight, I saw a point of light in the sky.

It could have been a burning ball of hydrogen, millions of miles across, and trillions of miles away. But I knew it wasn't a star, because it was much too bright.

It could have been a ball of rock, brightly reflecting sunlight off its clouds of acid. But I knew it wasn't Venus, because it was moving much too quickly.

It could have been a bit of dust, falling to the earth a hundred times as fast as a speeding bullet. But I knew it wasn't a meteor, because it lasted much too long.

It was a structure the size of a football field, made of aluminum, titanium and silicon, over two hundred miles above our heads, always falling, but always missing the ground, current home to six. It was the International Space Station.

The Autumnal Equinox

We live on the surface of a giant spinning ball. From our perspective, everything else appears to move around us as we spin. The sun, the moon, the planets, the stars. As we spin to face the sun, it appears to rise the sky. As we spin to face away is appears to set. It is no coincidence that we spin around exactly once each day. It is our spinning that determines the length of the day.

But we don't just spin in place. As we spin, we move in a circle around the sun. But the way we spin is tilted compared to the way we move around the sun. And the direction we're tilted doesn't change as we move around the sun, which means that sometimes we're tilted toward the sun, and sometimes we're tilted away from it. When you're tilted away from the sun, the days are shorter and the nights are longer, which makes it colder. The winter solstice is the day when you're tilted exactly away from the sun. When you're tilted toward the sun, the days are longer and the nights are shorter, which makes it hotter. The summer solstice is the day when you're tilted exactly toward the sun. It is no coincidence we move around the sun exactly once each year. It is our moving around the sun that determines the length of the year.

Not to scale. Credit: NOAA

Keep in mind that when the northern hemisphere is tilted toward the sun, the southern hemisphere is tilted away, and vice versa. The summer solstice in the northern hemisphere is the winter solstice in southern hemisphere, and the winter solstice in the northern hemisphere is the summer solstice in the southern hemisphere.

But today, we aren't tilted toward the sun, or away from it. Today, we are tilted perpendicular to the sun. Today is the autumnal equinox, the day when the day is equal to the night.

The equinox is a time of change. It marks the midpoint in the transition from the summer solstice to the winter solstice. Beyond that, it is also an inflection point. After the summer solstice, the days get shorter. At first, only a little bit. One day will be only a few seconds shorter than the day before it. But over time, the change increases, until one day will be minutes shorter than the day before it. The solstice is the time of the fastest change. After the solstice, the days will continue to get shorter, but the speed of the change will slow down again.

Science and Wonder

It is a common notion that science takes the wonder out of life. A prime example is John Keats's poem, Lamia.

Do not all charms fly
At the mere touch of cold philosophy?
There was an awful rainbow once in heaven:
We know her woof, her texture; she is given
In the dull catalogue of common things.
Philosophy will clip an Angel's wings,
Conquer all mysteries by rule and line,
Empty the haunted air, and gnomèd mine—
Unweave a rainbow, as it erewhile made
The tender-person'd Lamia melt into a shade.

I think this notion is wrong. Science, when properly understood, doesn't destroy wonder, it enhances it.

First, I'd like to clearly separate two relevant meanings of the word wonder. The first is synonymous with awe, the feeling you get when you think, "That's really really cool!". The second is synonymous with curiosity, the feeling you get when you think, "I wonder how that works...". They frequently come together, but they don't have to. It's entirely possible to feel awe at something that you understand completely, or to feel curious about something isn't particularly awe-inspiring.

Science enhances the feeling awe, because it reveals nature, and nature is, well, awesome. The real world is far cooler and more interesting than any fictional world I've ever read about (which is not to say that fictional worlds can't also be cool and interesting). I've written about this before, and given several examples of real awe-inspiring things. Most of those things would never be known about without science. And you can't have a feeling of awe towards something you don't know exists.

Science enhances curiosity in much the same way. Every question answered by science uncovers still more to be asked. Questions you wouldn't even be able to ask before, since you wouldn't have known the concepts they apply to.

I think the reason Keats, and others who make this claim do so because of two mistakes. First, they don't realize that the feeling of awe can be separated from the feeling of curiosity. Second, they don't realize that answering questions you're curious about can uncover deeper questions. If those two things weren't the case, then science would destroy wonder. Fortunately they're not.

Superman and the Physics of Collapsing Buildings

I saw the new Superman movie this weekend, and I liked it. But it wasn't perfect, and the thing that bothered me the most was the bad physics. I'm not talking about Superman being able to fly or the Kryptonian terraforming machine being able to increase Earth's mass. That kind of thing is expected in a superhero movie. I'm talking about more everyday physics. The most egregious example is skyscrapers falling over.

It happens multiple times in the movie. Superman throws a bad guy (or a bad guy throws Superman) through a skyscraper, part of the building is damaged, it tips and falls over like a tree. You might be wondering what's wrong with that. After all, trees fall down like that. If you build a tower out of Legos and knock it down, it falls down like that. But large buildings don't fall down like trees or Legos. They don't fall over sideways, they simply fall straight down.

So, why do large building fall down? Because gravity pulls them down. It does not pull sideways, so it doesn't tip sideways. But then why do Legos and trees fall sideways? Because there are other forces at work, namely the internal forces holding them together and in the same shape. Gravity is pulling down, but the internal forces prevent the top from simply collapsing into the bottom, so it falls sideways.

Here's a force diagram of a brick in a Lego tower tipping over. Gravity is pulling down. Normal force is pushing at the same angle the building is tipping. The total force is in blue. The vertical components mostly cancel, leaving the total force going mostly sideways.

But why don't large buildings do the same? Don't they have internal forces too? Well, yes, but they don't scale up. As the building gets bigger, it gets heavier, and gravity pulls more strongly. The internal forces of a large building will be stronger than those of a Lego building because it's made with steel rather than plastic, but it will be weaker relative to the force of gravity. The normal force will still be there, causing it to tip just a little bit, but gravity will dominate, so it will fall almost straight down. The top will simply collapse into the bottom, rather than being pushed to the side.

So why does this matter? It's just a movie, right? That's true, but understanding physics and how forces scale can be important. For example, there was a very well known case where some tall buildings fell down unexpectedly. As physics predicts, the buildings fell mostly straight down. (But not entirely. A lot of nearby buildings were hit by debris.) But a lot of people didn't understand the physics, and thought that the fact that the buildings fell down instead of over meant the buildings weren't brought down by airplanes, but rather by controlled demolition, and thus a conspiracy theory was born.