November 26th, 2015

Why doesn’t the Moon smash into the Earth?

Because it’s in orbit. But can you explain why this is?

I’m currently writing two non-fiction children’s books about the Universe and Earth. In order to explain certain concepts simply, I’m finding I have to gain a much deeper understanding of them myself. Proof of what Einstein said: ‘If you can’t explain it simply, you don’t understand it well’.

Searching for explanations to the question of why the Moon doesn’t get pulled into the Earth by its greater gravity, I found a lot of perplexingly vague answers. But I also found this excellent explanation by one Mark Eichenlaub on StackExchange, illustrated with a beautiful diagram by Isaac Newton:

The moon does not fall to Earth because it is in an orbit.

One of the most difficult things to learn about physics is the concept of force. Just because there is a force on something does not mean it will be moving in the direction of the force. Instead, the force influences the motion to be a bit more in the direction of the force than it was before.

For example, if you roll a bowling ball straight down a lane, then run up beside it and kick it towards the gutter, you apply a force towards the gutter, but the ball doesn’t go straight into the gutter. Instead it keeps going down the lane, but picks up a little bit of diagonal motion as well.

Imagine you’re standing at the edge of a cliff 100m tall. If you drop a rock off, it will fall straight down because it had no velocity to begin with, so the only velocity it picks up is downward from the downward force.

If you throw the rock out horizontally, it will still fall, but it will keep moving out horizontally as it does so, and falls at an angle. (The angle isn’t constant – the shape is a curve called a parabola, but that’s relatively unimportant here.) The the force is straight down, but that force doesn’t stop the rock from moving horizontally.

If you throw the rock harder, it goes further, and falls at a shallower angle. The force on it from gravity is the same, but the original velocity was much bigger and so the deflection is less.

Now imagine throwing the rock so hard it travels one kilometer horizontally before it hits the ground. If you do that, something slightly new happens. The rock still falls, but it has to fall more than just 100m before it hits the ground. The reason is that the Earth is curved, and so as the rock traveled out that kilometer, the Earth was actually curving away underneath of it. In one kilometer, it turns out the Earth curves away by about 10 centimeters – a small difference, but a real one.

As you throw the rock even harder than that, the curving away of the Earth underneath becomes more significant. If you could throw the rock 10 kilometers, the Earth would now curve away by 10 meters, and for a 100 km throw the Earth curves away by an entire kilometer. Now the stone has to fall a very long way down compared to the 100m cliff it was dropped from.

Check out the following drawing. It was made by Isaac Newton, the first person to understand orbits. IMHO it is one of the greatest diagrams ever made.


What it shows is that if you could throw the rock hard enough, the Earth would curve away from underneath the rock so much that the rock actually never gets any closer to the ground. It goes all the way around in the circle and might hit you in the back of the head!

This is an orbit. It’s what satellites and the moon are doing. We can’t actually do it here close to the surface of the Earth due to wind resistance, but on the surface of the moon, where there’s no atmosphere, you could indeed have a very low orbit.

This is the mechanism by which things “stay up” in space.

Gravity gets weaker as you go further out. The Earth’s gravity is much weaker at the moon than at a low-earth orbit satellite. Because gravity is so much weaker at the moon, the moon orbits much more slowly than the International Space Station, for example. The moon takes one month to go around. The ISS takes a few hours. An interesting consequence is that if you go out just the right amount in between, about six Earth radii, you reach a point where gravity is weakened enough that an orbit around the Earth takes 24 hours. There, you could have a “geosynchronous orbit”, a satellite that orbits so that it stays above the same spot on Earth’s equator as Earth spins.

Although gravity gets weaker as you go further out, there is no cut-off distance. In theory, gravity extends forever. However, if you went towards the sun, eventually the sun’s gravity would be stronger than the Earth’s, and then you wouldn’t fall back to Earth any more, even lacking the speed to orbit. That would happen if you went about .1% of the distance to the sun, or about 250,000 km, or 40 Earth radii. (This is actually less than the distance to the moon, but the moon doesn’t fall into the Sun because it’s orbiting the sun, just like the Earth itself is.)

So the moon “falls” toward Earth due to gravity, but doesn’t get any closer to Earth because its motion is an orbit, and the dynamics of the orbit are determined by the strength of gravity at that distance and by Newton’s laws of motion.

Still, it will be hard to condense this into a few short sentences for kids.

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November 5th, 2015


A page from the graphic novel/cookbook I’m working on with artist Val Gallardo.

I’m currently working on a graphic novel/cookbook with artist Val Gallardo. We are working on the story together and she is illustrating it. I’m developing the recipes for the book. It follows the story of a group of friends who haven’t seen each other since art school but are brought back together after each receiving an invitation to dinner from a mysterious vegan burger franchise owner named Bingo Lovelett.

November 5th, 2015

The Leaden Echo and the Golden Echo

I read Gerard Manley Hopkins 1918 poem and turned it into an ambient-electro track.

August 18th, 2015

David Wagoner, Lost

Stand still. The trees ahead and bushes beside you
Are not lost. Wherever you are is called Here,
And you must treat it as a powerful stranger,
Must ask permission to know it and be known.
The forest breathes. Listen. It answers,
I have made this place around you.
If you leave it, you may come back again, saying Here.
No two trees are the same to Raven.
No two branches are the same to Wren.
If what a tree or a bush does is lost on you,
You are surely lost. Stand still. The forest knows
Where you are. You must let it find you.

David Wagoner, Traveling Light Collected and New Poems. Urbana: University of Illinois Press, 1999.

April 9th, 2015

Cat Reacts

New track with words by Dominique De Groen.

April 4th, 2015

Het Doel en de Strekking

I composed the end-credits music to a poetic Flemish cop series from the nineties that never existed.

March 26th, 2015

All-Purpose Device

A text distilled from a manual for a photocopier.


November 8th, 2014

The Air Became Their Habitat

An ambient track about the first flight of the pterosaur.

October 26th, 2014

The Art of Conversation

I’m quite good at going around in circles, so I thought I’d try composing a waltz.

October 13th, 2014


June 23rd, 2014

Spooky Mulder

Something I made to amuse myself while everybody else was watching the football this evening.

June 10th, 2014

Shakespeare and Love

Stephen Fry at the 2014 Hay Festival, speaking about Shakespeare’s sexuality, sonnets and the disputed authorship of his works.

June 5th, 2014

Ray Kurzweil: Get ready for hybrid thinking


May 31st, 2014

look closer…


Amazing GIF image created using images from a scanning electron microscope:

As the incredibly powerful microscope zooms in, it goes from showing an amphipod (a type of shell-less crustacean), to a diatom (a type of algae) that’s on the amphipod, to a microscopic bacterium that’s on the diatom that’s on the amphipod. It’s life, on life, on life:

The GIF was created by James Tyrwhitt-Drake back in 2012, when he captured the images at the University of Victoria’s Advanced Microscopy Facility and posted the final product to his Tumblog, Infinity Imagined.

Via PetaPixel.

May 30th, 2014

Alan Watts on business, ‘rascality’ and trust

May 25th, 2014

Beneficial brain activity during ‘non-directive’ meditation

Psyblog reports on an interesting study that suggests that non-directive meditation has more beneficial effects than focused meditation.

All the different types of meditation can be split into two main types:

In non-directive types of meditation, people focus on their breathing or a sound, but also allow their mind to wander where it will.
In concentrative types of meditation, people try to focus closely on their breath, or something else, in order to suppress other thoughts and feelings they experience.

“The study indicates that nondirective meditation allows for more room to process memories and emotions than during concentrated meditation.”

“This area of the brain has its highest activity when we rest.

“…types of meditation that allow spontaneous thoughts, images, sensations, memories, and emotions to emerge and pass freely without actively controlling or pursuing them, over time may reduce stress by increasing awareness and acceptance of emotionally charged experiences.

“…mind wandering and activation of the default mode network in general may serve introspective and adaptive functions beyond rumination and daydreaming.

Potentially useful functions would include mental simulations, using autobiographical memory retrieval to envision the future and conceiving the perspective of others.” (Xu et al., 2014).

Read more.

May 8th, 2014

Psychogeography and the dérive


…The situationists’ desire to become psychogeographers, with an understanding of the ‘precise laws and specific effects of the geographical environment, consciously organized or not, on the emotions and behaviour of individuals’, was intended to cultivate an awareness of the ways in which everyday life is presently conditioned and controlled, the ways in which this manipulation can be exposed and subverted, and the possibilities for chosen forms of constructed situations in the post-spectacular world. Only an awareness of the influences of the existing environment can encourage the critique of the present conditions of daily life, and yet it is precisely this concern with the environment which we live which is ignored.


Psychogeography on wikipedia

December 21st, 2013

forget words

I live here in a village house without
all that racket horses and carts stir up,

and you wonder how that could ever be.
Wherever the mind dwells apart is itself

a distant place. Picking chrysanthemums
at my east fence, I see South Mountain

far off: air lovely at dusk, birds in flight
returning home. All this means something,

something absolute: whenever I start
to explain it, I forget words altogether.

No. 5 from Drinking Wine; T’ao Ch’ien (365-427 CE)

Translation: David Hinton

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