# I Wasn't Your Source on This

Explosions, Fireballs in Virginia Skies May Have Been Russian Rocket

The mysterious boom and flash of light seen over parts of Virginia Sunday night was not a meteor, but actually exploding space junk from the second stage of a Russian Soyuz rocket falling back to Earth, according to an official with the U.S. Naval Observatory.

For the record, it’s Geoff, not Jeff. Silly Journalists.

Pick me! Pick me! Adopt-a-physicist is running again this spring. Registration/sign-up is open as of today, with the forums open April 13 – May 1.

Help high school students explore what it’s really like to be a physicist – consider participating in Adopt-a-Physicist! In this program, people with physics degrees (at any level) are “adopted” by high school classes interested in finding out about the careers, educational backgrounds, and lives of real physicists.

# Thinking in Two Dimensions

Solar power: A Friday editorial said that according to the U.S. Energy Department, enough sunlight hits a “100-square-mile” portion of the Nevada desert to power the entire country. It should have said “100-miles-square.”

The commentary: On square miles

I’d argue that “square miles” and “square kilometers” really have no place in popular journalism, because we have little connection to what they mean.

As humans, we never travel a “square mile.” We travel a mile. Or ten miles. If we’re thinking about an area of land, we’re probably mentally walking along two of its edges — which is what the LA Times and the U.S. Department of Energy were doing.

What you mean “we?” While the statement may be true (for some people), I’d argue that it’s an issue of mathematical/scientific literacy. Eliminating the use of area is to lower the bar of what we expect of journalists and readers of journalism. I never travel a cubic meter, either, but use of volume has its place — we don’t need to describe a liter as 10 cm on a side. We’re used to volume measurement, even if we in the US have an overall aversion to metric except when applied to some beverage containers. Why aren’t we used to areas — is it the name? Would “acres” be better, to avoid the “square” business?

The proposed solution includes giving an example, though, and giving a reference for scale is a good idea.

# Attack of the Killer Dust Bunnies

I was waylaid by dust bunnies yesterday. It started in the lab; I was exposing the fresh layer of sticky mats as I usually do, and noticed that the air disturbance (quite a flourish if you want to get the sheet up in one motion) had sent some dust bunnies scurrying. I tracked them down and captured them with an unused section of the mat, but they really shouldn’t be in the lab at all — that’s what the mats are for. We don’t let the cleaning crew in, because of safety issues and the potential for damage. But the mats have proven to be stronger than the floor, and the tile has been failing, so there are areas that have been mat-less for a while, and that has helped the bunnies thrive. I bought some frames (non-skid backing rather than adhesive) for the mats, so the mats can be reintroduced. Open season on dust bunnies! My colleague that signed the receipt for the mat frames said, “Mat frames. Cool!” Sure. He’s the one playing with the pulsed laser.

So I get home, and there’s a dreaded “Can’t connect to the internet” error on the computer. So I went searching for the likely suspects — cycle power on the modem and router, and then recheck all of the connections. Which requires some crawling around in places that have more dust bunnies! I had to wield the bunny-buster to ensure I got out alive. Turns out my phone jack had died, so no more DSL from there. I had to move the model and router to another room, and now I’m relying on wireless (and had some trouble with the router. Obviously an ally of the bunnies)

# Run Away!

Time-Lapse Video: Retreating Glacier

This remarkable image sequence captures a series of massive calving events at Columbia Glacier near Valdez, Alaska. Composed of 436 frames taken between May and September of 2007, it shows the glacier rapidly retreating by about half a mile (1.6 kilometers), a volume loss of some 0.4 cubic miles (1.67 cubic kilometers) of ice or 400 billion gallons (1.5 trillion liters) of water.

# Yelling for a Good Reason

The issue that helped instigate the issue in the previous post was How long would you have to yell to heat a cup of coffee?, which Zz had linked to.

The analysis is fine up until this point

The average human yells at about 80 decibels, which carries along with it about .001 watts of energy

The 0 dB reference for sound energy is 10-12 Watts, so 8 orders of magnitude higher is not a milliWatt. They get this right a little later on.

The average person whispers at about 40 decibels, which translates out to about 10-8 (sic) watts.

Go up by 40 dB, and you get 4 orders of magnitude in power, or 10-4 Watts. But I also read that “loud speech” is equated to 90 dB, not 80 dB, so I’m not sure where the error truly lies. If the power in Watts is what they wanted to use then their answer is fine, but if they really meant 80 dB then the answer is too small by a factor of 10.

When I first saw this problem, it was in the form of a claim that it would take 8 years of yelling, and that fits if you yell at somewhere around 83 dB. The point is that sound doesn’t carry much energy, which is one reason behind Nick’s calculation about how the Electrons per Song on an iPod has been decreasing, and how it’s possible that you can run one for 10 hours on a 3.7 V battery with only 73 mAh of capacity. That’s just 2.7 Joules, but even at 110 dB, this would only represent 1 Joule of sound energy during that span.

# On the Job

How Physics Can Solve Crime And Help To Cure Cancer

Zapperz has a nice little rant, after linking to a story that presents an order-of-magnitude solution to some trivial situation.

I also received a rather nasty and profanity-laced “comment” to the blog, which basically asked why us “MF’s” are wasting out time and not using our brains to cure cancer

Short answer: Chill, bro. “We” (meaning some physicists) are, but OOM calculations are only the beginning of such issues, whereas they were the end of the “how much energy does it take to do X” problem.

# Does it Weigh the Same as a Duck?

Iron: 7.87 g/cm^3 Mercury: 13.5 g/cm^3