Scientific Seen

News, Commentary, and Tutorials from a Scientific Perspective

A few years ago XVIVO and Harvard University released a video of a scientific visualization entitled, “The Inner Life of the Cell.” I wasn’t a big fan. It was a fairy-tale vision of cellular activities.

If you saw a simulation of traffic flow on the highways and every vehicle in each lane was going the same speed, maintaining proper following distance, signalling and changing lanes only when necessary, merging and exiting with decorum—it might be nice, but it would be so fanciful that it would do more harm than good if you were trying to understand highway traffic in the real world. When you look at real-world traffic, you have difficulty believing anyone can travel the highways safely, but the simulation would make it hard to imagine there could ever be such a thing as a freeway collision.

A scientific visualization should induce a mental model that catalyzes an improved understanding of reality, and the 2006 simulation failed.

Of course, a simulation like this is going to be unrealistic. Molecules aren’t distinguished by hues, atoms don’t remain stationary with respect to their neighbors, and there’s no classical music soundtrack in a real cell. But the 2006 simulation was so far removed from reality that (in my opinion, of course) it served more to confuse than clarify perceptions about molecular activities in a living cell. My biggest peeve: all the molecules were shown in stately glides as if a miniature synchronized swimming team was displaying the results of years of practice. On those scales, the “aqueous” environment behaves more like peanut butter. Kinesin molecules grab onto microtubules and pull because they have to to make it through the thick goop through which they travel, and none of that difficulty was shown.

Protein Packing in the Cell

A lot to admire in the new XVIVO/Harvard scientific visualization of molecular activities within a living cell.

Now the same scientific visualization team has created a new video, “Inner Life of a Cell—Protein Packing.” This one is so much better. It’s a much more crowded world, and the actions of proteins are limited by interference from all their neighbors. None of the small molecules are shown (not a criticism—if water, ions, and sugars were visible you wouldn’t be able to visualize anything through the resulting mess), but many of the proteins are shown. Of course it’s not “accurate”—it’s a visualization!—but this one is much more representative of the kind of confused and crowded environment within living cells. The new simulation makes it much clearer that the normal processes of life are challenged with every motion, and the new video makes it easier to be awed by the mere fact that we are alive. Heartily recommended!

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One of the reasons light is so useful is that, although it can do some pretty complicated things, it operates according to fairly straightforward rules. That might be hard to believe when you stand between two mirrors that face each other almost perfectly, and you can see a reflection of yourself going off into infinity, but that’s just a simple rule being applied over and over again with each reflection. Tri-fold mirrors operate by those same simple rules.

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Originally published at eHow, SEP 2011

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Imagine the fuel bill for the Space Shuttle. It’s hard enough to fill your car with 16 gallons of ordinary gas, so imagine the cost to fill a 526,000-gallon tank with rocket fuel. And that’s just to ferry a satellite into orbit. Once in orbit, satellites have to jet themselves around with fuel they’ve brought themselves. Space travel is expensive and there’s a constant search for less costly means of propulsion.

The thrust generated by a propulsion system is proportional to the mass of the propellant multiplied by its velocity. That is, a spacecraft sending 50 grams of propellant away at 3 meters per second has the same thrust as another sending 25 grams away at 6 meters per second. That’s the idea behind electric propulsion: Use less mass than traditional propulsion systems, yet expel it more rapidly. And bringing less mass into Earth’s orbit means the spacecraft is lighter, so it needs less expensive rocket fuel to the begin with.

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Originally published at eHow, SEP 2011

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If you’ve ever woken up early in the morning, piled into the car, and spent the day skiing in the mountains, you probably found yourself huffing and puffing the whole time. Some of that was almost certainly due to the exhilaration of flying down the snowy slopes, but you’d have been struggling to catch your breath even when walking up the steps to buy a hot cocoa in the lodge. The usual explanation? “The air is thinner up there.” That’s true, as far as it goes, but here’s a bit more detail.

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Originally published at eHow, 2011

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Einstein got his Nobel Prize for explaining the photoelectric effect. A metal surface releases photoelectrons when it absorbs light. Einstein showed that the energy of the electrons depended not upon the brightness of the light, but upon its wavelength. In and of itself, that’s an interesting if not so exciting fact. But Einstein’s discovery implies that the world consists of tiny, discrete particles that can only have specific amounts of energy — the foundation of quantum mechanics. The key to verifying Einstein’s interpretation is measuring kinetic energy by applying stopping voltages. You can make that very measurement.

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Originally published at eHow, AUG 2011

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