Sunday, June 23, 2019
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They say not to judge a book by its cover. But what about a pizza by its cheese or a silicon chip by its top layer? This week was full of things hidden (but still important!) underneath the surface.
To start with the most relevant example of this, we need to take a quick look at a concept known to scientists and musicians alike: resonance. It’s the phenomenon that happens, in general, when an oscillating driving force matches the “natural” frequency of an oscillator. Just think of a child on a swing: you push them at a regular frequency because you know that’s the best way to increase their momentum. The same process of frequency matching happens in musical instruments, powerful lasers, glow-in-the-dark chemicals, and the electric circuits which make your radio antenna work.
In the Atomic Force Microscope, the probe tip is vibrating near the surface at (or around) its resonant frequency. But imagine now that some external force starts to act on the probe. To go back to the earlier analogy, it’s as though the child you’re pushing suddenly got heavier, or the swing lengthened. Your pushes are no longer perfectly timed, assuming you keep the same frequency of driving force. The electronics of the AFM measure this shift, and translate it into an electrical signal. When the AFM is measuring topography, this signal translates into bumps and valleys of the surface the tip is moving over. But in the type of AFM we’re working to develop, other forces between tip and sample allow details beneath the surface to be resolved. This is dependent on using an electrical signal to bias the tip and sample, creating an electrostatic force (like the one that sticks balloons to your hair or Styrofoam to your hands). So even though the top of our silicon chips might be perfectly flat, the wires beneath the surface are visible and clear (and abrupt) shifts in resonant frequency.
But you didn’t come here just to read about resonance (even though, if you ask any Organic Chemistry student, they’ll tell you that everything is about resonance). We also took time to have some fun this week. Wednesday night was community food night, and Bells did a great job making a pizza crust from scratch. We made vegetable pizza, two chicken-bacon-ranch pizzas, and a garlic cheese pizza[3]. I might have been a bit overzealous with the cheese application–but I won’t apologize for my Chicago-style leanings. It just made it difficult to tell what the rest of the toppings were; too bad there’s not an AFM probe for determining sub-cheese layers.
As you’ll probably read in some other posts, we got the chance to participate in a big science outreach event here on Saturday: Astronomy on the Mall. All kinds of scientific and public groups with an interest in space science were lining a major thoroughfare of the National Mall, presenting outreach activities and demonstrations (including some high-powered telescopes) to the general public. NASA shirts abounded, stardust glinted in the evening’s light, and the globe we stand upon rotated until our neighborhood star was out of sight. Jupiter shone brightly for all to see, and the assembled crowds could even glimpse the Galilean moons through one of the telescopes.
We at SPS’s tables had our own demonstrations going on, simple things that educators can create at low cost. Things like a spandex sheet stretched over a large hoop, with a weight in the middle, demonstrating the deformation of spacetime caused by gravity. By rolling small marbles around the indentation in the sheet, we showed how massive objects pull small objects into orbit around them. Kids and adults alike enjoyed giving our “planets” a whirl (or two, or three, or half an hour’s worth). Others around me demonstrated the composition of the universe with beads, stars’ life cycles with balloons and aluminium foil, and sound waves with a Slinky.
But the greatest adventure was yet to come! June 22nd was a special day for the Smithsonian museum; on “Solstice Saturday”, the already amazing (free) museums were open until midnight. After dropping off all our demo supplies, the group had a decision to make. We had a glorious two-hour window in which we could visit the widely-advertised dinosaur exhibit at the Smithsonian Museum of Natural History, with the added bonus of the evening hour adding a seemingly magical, after-hours kind of thrill. Or we could go find ice cream. Now, I’m not saying the people who used those two hours to get ice cream made a sub-optimal decision. I’m just saying they chose not to be a part of Team Dinosaur. So. But those of us who did go had a wonderful time exploring the exhibit (and realizing that the Museum as a whole is truly massive and would take days to fully appreciate). And it tied in nicely with this week’s theme: scientists only know things about dinosaurs by examining their bones. In terms of fossils, it really is what’s on the inside that counts. After the museum, the two groups met up again in good old Room 211 for a documentary screening which was both thought-provoking and enjoyable. And they say nerds don’t know how to have fun.
This last paragraph is back by popular demand: the breathless, context-less run-on evoking images both fanciful and frightening. Enjoy!
In the past week, we: completed crosswords, made contact with “mayonnaise” (with the help of a man on the metro), learned of the secret subway (something else beneath the surface!), got serenaded by trumpets, ate banana bread amid cries of “scalene triangle”, chose cake over death, put SOCKS in socks, planned a heist, learned that laser gyroscopes are, illogically, extremely accurate, boomwhacked, SAILed, played with spacetime, learned that Diversity is the Spice of Life, decomposed a lizard, ate cake in a church basement, learned that too many cooks spoil the broth, got the second degree, and, as always, gave thumbs up for science.
On the face of it, this is just another summer. Just another internship. But look a little deeper, and you’ll find a wealth of opportunity and excitement.
Here’s to a future of hidden possibilities made real.
Joseph
Joseph Tibbs