Redshift refers to light being 'shifted' towards the redder end of the spectrum — longer wavelengths — as objects move away from each other. If a light source is moving towards us then light is blueshifted, shifting towards the bluer end of the spectrum, shorter wavelengths.

Imagine waving a spring back and forth to create a wave and then starting to run away – the waves would be stretched longer. Because the universe is expanding 🤯 distant galaxies are moving away from us faster than nearer ones — imagine how the chocolate chips in a cookie move away from each other as the cookie bakes and grows in an oven. By comparing the redshift of light seen from distant galaxies with what we would expect to see it's possible to use redshift to determine how far they are away.

Redshift is an example of the Doppler effect, or Doppler shift, in action. It's more commonly known by the stretching or compressing of soundwaves as, say, an ambulance moves towards or away from you, or how the sound in front of a moving aircraft eventually can produce a sonic boom.

Redshift

Physics envy refers to the wish that a field of study would turn out to be as precise, as predictable, as repeatable, and as amenable to modeling and theory that replicates practice as physics is.

As it turns out, most fields that involve people — such as economics and the social sciences — are rarely so tidy and orderly and neatly mathematically modeled. They are instead usually messy, uncertain, and filled with context, nuance, history and confounding factors such that making sense of them in broadly applicable ways is rather difficult. And while we do our best to quantify and identify effects, or cleanly isolate our cognitive biases or our quirks of behavioural psychology, rarely are they able to live up to the purest standards of physics. It's enough to turn one green with envy.

It reminded me of the best laid plans of our Saturday sports coaches turning for their substitutes to execute their plans, only to find the players climbing trees in the adjacent field.

Physics Envy

Brilliance bias is the tendency for people to think of 'brilliance' as generally a male trait. With fewer women generally recorded in the history books, the brilliant people that come to mind from a young age tend to be men.

Underrepresentation has consequences. Careers that are generally understood to require 'brilliance' to succeed such as maths, physics, or philosophy, are likely to have fewer women working in them. Even at school age, attitudes start to shift in both girls and boys. For example, having interest in games that require you to be 'really smart' or whether, when asked to draw a scientist, we draw a woman or a man. We need to stop teaching brilliance bias and we need to celebrate the many female role models we have.

My sister shared with me a page on drawing famous faces that showed 49 men to draw, and an example of the board game Guess Who having as many women to guess as it has men with facial hair as an attribute.

I learned about brilliance bias, including the examples here, from Caroline Criado Perez's eye-opening book Invisible Women.

Brilliance bias

If you wanted to know who would win an election, then the only reliable (most of the time) way to do that is to ask everyone to vote for real and count them all. Short of doing that, if you want to get an idea who would win you can pick a group that you hope is representative of the whole of the voting population, ask them what they plan to vote instead, and then multiply up to the full group. But it turns out, whenever you ask people things, it's jolly hard to really have confidence in what you're extrapolating up to as all sorts of bias can creep into your sample.

If you ask people what they plan to vote they may lie, they may tell you what they plan to do then change their mind, they may tell you what they think you want to hear depending on who's asking, they may say the first option because it's easiest, and you may ask in the places where it's easy or cheap to do so, or hear from only the people who are happy and not too busy to talk with you.

In the example in the sketch, if you hope to receive responses to your questions by surveys then you get responses from people who happen to not mind doing surveys — from anyone who throws them in the bin you won't receive a single data point.

All of these, and others, can lead to a bias in your sample and, at times, to drawing wholly inaccurate conclusions.

Extreme example from How to Lie with Statistics by Darrell Huff.

Sampling bias

Sir Arthur Eddington, an English astrophysicist, told a short story involving a scientist studying fish by pulling them up with nets. After checking all the fish hauled up, the scientist concludes that there is a minimum size of fish in the sea. But the fish seen were determined by the size of the holes in the net, the smaller ones having slipped through, unmeasurable. The instrument you use affects what you see. Or as Richard Hamming puts it: "You get what you measure."

This analogy provides a nice concrete example of a phenomena that affects us routinely in more subtle ways. What and how we choose to measure affects the conclusions we draw. So, a website may easily measure sales and bounce rate for its pages, while things like trust, authority or satisfaction, which may be more significant longer-term metrics, go unmeasured.

"There is always a tendency to grab the hard, firm measurement, though it may be quite irrelevant as compared to the soft one which in the long run may be much more relevant to your goals. Accuracy of measurement tends to get confused with relevance of measurement, much more than most people believe. That a measurement is accurate, reproducible, and easy to make does not mean it should be done, instead a much poorer one which is more closely related to your goals may be much more preferable. For example, in school it is easy to measure training and hard to measure education, and hence you tend to see on final exams an emphasis on the training part and a great neglect of the education part."

What gets measured gets better (an earlier take on this)

Quote from Chapter 29, You get what you measure, of Richard Hamming's, The Art of Doing Science and Engineering: Learning to Learn.

If you happen to be in the business of doing research or science Richard Hamming's Bell Lab's talk, You and Your Research (pdf), is an excellent read.

You get what you measure

A school science refresher: the 3 primary states of matter, solids, liquids and gases and the transitions between each one. If you’re like me you probably forget about the more obscure sublimation and deposition directly between solids and gases. And vaporisation of a liquid is evaporation, occurring at the surface, if it is below boiling point, otherwise it’s boiling.

There are some more unusual states including plasma — seen in lightning and fluorescent lights — and Bose-Einstein condensates, but mostly we’re familiar with ice cubes, water and steam.

States of matter

Also known as Brandolini’s Law, this is the simple observation that it’s far easier to produce and spread BS, misinformation and nonsense than it is to refute it.

In fact, the iSchool at University of Washington launched a course on Calling Bullshit with the first class being booked up within one-minute of registration. The professors, Carl Bergstrom and Jevin West have since written a book: Calling Bullshit: The Art of Skepticism in a Data-Driven World.

Phil Williamson in Nature also wrote a nice article emphasizing that we should take the time and effort to correct misinformation where we can. In it, he proposed the idea that “The global scientific community could…set up its own, moderated, rating system for websites that claim to report on science. We could call it the Scientific Honesty and Integrity Tracker, and give online nonsense the SHAIT rating it deserves.”

The BS asymmetry principle

Perhaps the most important curve of our times, Charles Keeling’s  curve shows the change in concentration of CO2 in the air with measurements taken every year for over 60 years. Taken at the top of Mauna Loa volcano in Hawaii because of its high altitude and relative isolation in the Pacific, Charles Keeling’s measurements show that the monthly average CO2 concentration in the air has risen from around 310 ppm (parts per million) to around 410 ppm in 2020. As a greenhouse gas this change in CO2 concentration is one of the critical causes of climate change.

The concentration varies seasonally as plants bloom in Spring and Summer reducing the concentration from its high around May as the CO2 has built up over the Norhern Hemisphere Winter.

The Scripps CO2 program is now overseen by Charles’ son Ralph Keeling.

The Keeling curve

A full moon that hits twice in a calendar month. Given the cycle from full moon to full moon is about 29.5 days it doesn’t happen very often that this coincides so nicely. And February never has a blue moon.

I like this definition, but it is apparently a modification to the original definition which is a little more complicated. Given the 29.5 day cycle, most seasons of 3 months have 3 full moons. But every now and then, a season would come by, like Sep, Oct, Nov in the sketch, where there would be 4 full moons. The 3rd of these was known as a blue moon, or a seasonal blue moon. See why I like the modern definition?

Here’s a good article that explains the subtleties and history of blue moons.

Check out more moon or astronomy sketchplanations

What is a blue moon?

These days beards are in. There will come a day when beards are out. And a day when beards are back in again. That’s how it seems to go.

Turns out there is a name for this kind of thing: negative frequency-dependent selection. Essentially, the less common it is, the more useful a trait it is. As opposed to positive frequency-dependent selection which, as you can imagine, is the reverse.

According to this study, for example, when there are fewer men with beards in a population, they are judged as more attractive than when there are more of them. Hence they become gradually more popular until the effect starts to wear off and the clean-shaven look starts to appeal again. And round the cycle we go.

The beard cycle

I’ve never used one, but I’d love to. They seem a little like magic. Basically, you pressurise the air of an underwater box enough to keep the water from coming in. This enables you to have a kind of swimming pool entrance to water even though you’re already actually underwater. So cool.

Moon pool

Which is kind of amazing. The magnetic field is produced by some remarkable result of the convection of molten hot iron alloys in the core of the Earth. Kind of hard to really get your head round if you’re sitting calmly at your desk or walking on a nice stable surface. Periodically, the poles switch round it seems but at the moment the magnetic South pole is actually near the point we’d normally call the geographical North pole. They’re pretty close, but the geographic axis doesn’t exactly coincide along the geographic axis of rotation of Earth. And the lines of force go from magnetic North to magnetic South so your compass needle is actually pointing towards magnetic South. Remember iron filings and bar magnets from physics class?

Earth is a big magnet.

I like this radius. It explains some of why asteroids are lumpy and bumpy, kind of like potatoes, and yet planets and moons are smooth round balls.

From the potato radius size, about 2–300km, the mass of the rock itself gets large enough that it is pulled in on its own gravity and consequently starts to round itself off.

I learned about this from Brian Cox’s show Forces of Nature.

Not sure about asteroids, meteors and meteorites?

The potato radius

How do you remember which are stalactites and stalagmites in a cave? And how to spell them?

The key to getting the whole thing the right way round in my mind is to remember that you need to cling tight (tite) to the ceiling. Once that’s established, you have a letter C in stactite that fits cling and ceiling. And stalagmites, with its cheeky G, naturally then is the other one which would grow on the ground. Sorted?

Stalactites, Stalagmites

The clarity of the night sky. A low number means clear, black and amazing stars. Higher numbers mean gradually more urban environments with increasing light pollution. At 9 you’ll barely spot a star being pretty much in Piccadilly Circus or Times Square.

More detail needed? John Bortle, Light Pollution And Astronomy: The Bortle Dark-Sky Scale, Sky and Telescope, July 18 2006.

Bortle Scale

All of these guys can grow back major parts of their body, even limbs, and in the case of the flatworm a new head. Crazy.

Animals that regenerate

It’s good to know your waxing (growing) from your waning (shrinking), and that a gibbous is the shape of the moon when you take a crescent of shadow from a circle of light, and that the hardest moon to see is a new one.

If it’s light on the right, it’s gonna get bright. If it’s light on the left, it ain’t.

Like the moon? Apparently so do I: See the moon illusion, super moon, one side of the moon or just sketchplanations > astronomy.

Phases of the moon

This chart is from the original he published - just the five data points. Pretty simple huh? The “observation, originally made in 1965, that the number of transistors on an integrated circuit would continue to double every year. Although this increase has slowed to a doubling in eighteen to twenty four months, Moore’s law has held true for nearly fifty years and is the foundation for the astounding Information Technology revolution we see around us.”

For those interested in Moore’s law, remarkably, I think the best information is my Dad’s book, The Computing Universe, which is also the source of the quote.

Moore’s Law

A centipede has 1 pair of legs on each body ring, and a millipede has two on most body segments. Hence millipedes will generally have plenty more legs to go round. As far as I know this is fairly foolproof. Though generally speaking there are more obvious ways to tell, such as millipedes looking more like long armoured nice round worms and usually moving slowly, and centipedes zipping around while generally seeming more long-legged and insecty, with longer antennae at the front and longer angled back legs, sometimes with hooks for defence.

If you were offered to pick one of them up, you’d probably pick the millipede.

Also, in case you were tempted to think they are insects, they’re not because insects have six legs. They are arthropods (loosely meaning jointed feet) along with insects, spiders, scorpions and crustaceans, but in their own subphylum of, aptly named, myriapoda (loosely meaning many legs).

Check out core insect anatomy for a sketchplanation insect refresher.

How to tell a centipede from a millipede

Meteor: A rock burning up as it enters the atmosphere. Also known as a shooting star.

Meteorite: Parts of a meteor that made it all the way to the ground. Look out!

It was a long time before I really knew the difference between these things.

Asteroids, meteors and meteorites

Turns out a bunch of substances have the power to make you sleepy - tryptophan, vitamin B6, calcium, glycine, lactucarium and carbohydrates are some of the major ones. Some even interact with each other for maximum sleepiness. A few common foods with these compounds in good measure include:

turkey, walnuts - tryptophan
tuna, pistachios - vitamin B6
dairy - calcium
chamomile - glycine
lettuce - lactucarium

So an evening turkey or tuna, walnut, cheese and lettuce sandwich with a glass of milk and a side of pistachios or walnuts and you’ll be set for a good night.

Sleepy foods

Thunder clouds are so impressive. Lightning forms due to air currents in the cloud as warm moist air rises up quickly. All the collisions between particles cause different charges to develop between the top and the bottom of the cloud. When that gets large enough, kapow!

Also see: thunderclap or rumble, dirty thunderstorms.

Thunder clouds

Reproduction. Excess. Variation. Selection. Divergence.

Darwin’s 5 principles of Natural Selection

And straighter hair is rounder. You can demonstrate this with a strand of you hair by gripping it between the nails of two fingers and squeezing all the way down. As you make it oval, you’ll also see it curl.

Apologies to those who caught this earlier. I accidentally posted several in a row and removed them to post one at a time. Really sorry if it disappeared from your blog, and thanks for sharing.

Curly hair is oval

Stratus: layers AND Cumulus: heaps + height + Cirrus at the very top and you’re a long way already.

Know your clouds

How soap gets things clean is pretty amazing. What’s really nice is how the chemical properties generate such a simple mechanical solution.

The magic of soap

I shall always remember when I was finally taught that the trick is to dip your finger in the wine first.

Make a wine glass sing

Helpful reminder of how fragile the atmosphere is despite it looking pretty big when you’re standing outside.

Our atmosphere is as thick for the Earth a the skin on an apple

One way mirrors definitely do something, but a lot of what they accomplish is also due to maintaining dark on one side and light on another.

Dark and light are the keys to one-way mirrors

The sun behind you, the rain in front of you, and the angle is due to the refraction of light in the raindrops.

The position of a rainbow is predictable

A large boulder, transported and deposited by a glacier. This is my favourite location for glacial erratics. Bonus points if you can tell where it is.

Glacial erratic

Sure the big city is worse than the country. But the reality is back streets in a big city are significantly better than the busy streets in a big city, and air pollution changes massively even for small children down at the height of exhausts versus adults standing higher.

So if you’re not about to move to the country you could help yourself a lot nonetheless by taking the back streets (I read this premise in Focus magazine, but can’t find an online link to reference).

Pollution is highly localized: take the back streets

Part of the reason why bottles should really have their necks to one side instead of in the centre.

Give air a pathway to avoid glugging

Whichever way you look at it, water is a remarkable substance.

Why ice doesn’t sink

When a moon appears its largest. A treat for photographers with big zooms and aspirational looking cityscapes or yachts on the horizon (or ET on a flying bike). Hat tip to Science Llama.

Super moon

I love this quote from PW Anderson. More often seems like it should be more of the same, but more is different. It would be good if more people considered this.

More is different

Common in experience. Less commonly understood.

Anatomy of a wave

Every time I stop and think about a microwave I am reminded of Arthur C Clarke’s 3rd law of prediction:

“Any sufficiently advanced technology is indistinguishable from magic.”

Right up there with wifi and MRI. All just magic.

Also, I think you can use microwaves that little bit better when you understand what’s really going on.

On microwaves

It shuffles a little, but you’ll notice you can always see the face. The mathematics of it are quite hard to fathom.

Incredibly, we only ever see one side of the moon

the Angle of Incidence equals the Angle of Reflection

I wish I could echolocate. Then I wouldn’t need the one eye trick.

Sketchplanations tagged with science