Ask Hackaday: What Can Only A Computer Do?

It is easy to apply computers to improve things we already understand. For example, instead of a piano today, you might buy a synthesizer. It looks and works — sometimes — as a piano. But it can also do lots of other things like play horns, or accompany you with a rhythm track or record and playback your music. There’s plenty of examples of this: word processors instead of typewriters, MP3 players instead of tape decks, and PDF files instead of printed material. But what about something totally new? I was thinking of this while looking at Sonic Pi, a musical instrument you play by coding.

But back to the keyboard, the word processor, and the MP3 player. Those things aren’t so much revolutionary as they are evolutionary. Even something like digital photography isn’t all that revolutionary. Sure, most of us couldn’t do all the magic you can do in PhotoShop in a dark room, but some wizards could. Most of us couldn’t lay out a camera-ready brochure either, but people did it every day without the benefit of computers. So what are the things that we are using computers for that are totally new? What can you do with the help of a computer that you absolutely couldn’t without?

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Kathleen Lonsdale Saw Through The Structure Of Benzene

The unspoken promise of new technologies is that they will advance and enhance our picture of the world — that goes double for the ones that are specifically designed to let us look closer at the physical world than we’ve ever been able to before. One such advancement was the invention of X-ray crystallography that let scientists peer into the spatial arrangements of atoms within a molecule. Kathleen Lonsdale got in on the ground floor of X-ray crystallography soon after its discovery in the early 20th century, and used it to prove conclusively that the benzene molecule is a flat hexagon of six carbon atoms, ending a decades-long scientific dispute once and for all.

Benzene is an organic chemical compound in the form of a colorless, flammable liquid. It has many uses as an additive in gasoline, and it is used to make plastics and synthetic rubber. It’s also a good solvent. Although the formula for benzene had been known for a long time, the dimensions and atomic structure remained a mystery for more than sixty years.

Kathleen Lonsdale was a crystallography pioneer and developed several techniques to study crystal structures using X-rays. She was brilliant, but she was also humble, hard-working, and adaptable, particularly as she managed three young children and a budding chemistry career. At the outbreak of World War II, she spent a month in jail for reasons related to her staunch pacifism, and later worked toward prison reform, visiting women’s prisons habitually.

After the war, Kathleen traveled the world to support movements that promote peace and was often asked to speak on science, religion, and the role of women in science. She received many honors in her lifetime, and became a Dame of the British Empire in 1956. Before all of that, she honored organic chemistry with her contributions.

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A Beginner’s Guide To X-Ray Crystallography

In graduate school, I had a seminar course where one of the sections was about X-ray crystallography. I was excited, because being able to discern the three-dimensional structure of macromolecules just by shining X-rays on them seemed like magic to me. And thanks to a lackluster professor, after the section it remained just as much of a mystery.

If only I’d had [Steve Mould] as a teacher back then. His latest video does an outstanding job explaining X-ray crystallography by scaling up the problem considerably, using the longer wavelength of light and a macroscopic target. He begins with a review of diffraction patterns, those alternating light and dark bands of constructive and destructive interference that result when light shines on two closely spaced slits — the famous “Double-Slit Experiment” that showed light behaves both as a particle and as a wave and provided our first glimpse of quantum mechanics. [Steve] then doubled down on the double-slit, placing another pair of slits in the path of the first. This revealed a grid of spots rather than alternating bands, with the angle between axes dependent on the angle of the slit pairs to each other.


To complete the demonstration, [Steve] then used diffraction to image the helical tungsten filament of an incandescent light bulb. Shining a laser through the helix resulted in a pattern bearing a striking resemblance to what’s probably the most famous X-ray crystallogram ever: [Rosalind Franklin]’s portrait of DNA. It all makes perfect sense, and it’s easy to see how the process works when scaled down both in terms of the target size and the wavelength of light used to probe it.

Hats off to [Steve] for making something that’s ordinarily complex so easily understandable, and for filling in a long-standing gap in my knowledge.

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Rosalind Franklin Saw DNA First

It’s a standard science trivia question: Who discovered the structure of DNA? With the basic concepts of molecular biology now taught at a fairly detailed level in grade school, and with DNA being so easy to isolate that it makes a good demonstration project for school or home, everyone knows the names of Watson and Crick. But not many people know the story behind one of the greatest scientific achievements of the 20th century, or the name of the scientist without whose data Watson and Crick were working blind: Rosalind Franklin.

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