Daily Archives: February 23, 2012

In Space, No-One Can Hear You Go "Kerpow!"

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What Would Happen If You Shot a Gun In Space?

Newton’s third law dictates that the force exerted on the bullet will impart an equal and opposite force on the gun, and, because you’re holding the gun, you. With very few intergalactic atoms against which to brace yourself, you’ll start moving backward (not that you’d have any way of knowing). If the bullet leaves the gun barrel at 1,000 meters per second, you — because you’re much more massive than it is — will head the other way at only a few centimeters per second.

If the gun was not lined up with your center-of-mass, you would also feel a torque and begin rotating.

Time Has Come Today, Part I

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Last week I gave a seminar at Augusta State University called “It’s About Time” and promised to write up a summary of the talk, so here it is (sans a few cartoons and some data I don’t have permission to show). Some of the material I have discussed before, and some has been covered recently at the Virtuosi and, previously, at Uncertain Principles. Both discussions are good, but as I had noted for the former post, there are some subtleties to the discussion that one might not be expected to know if one isn’t exposed to timekeeping on a semi-regular basis.

The Chicago Way

I raised the questions asked in Chicago’s 1969/1970 song “Does Anybody Really Know What Time It Is?” the lyrics to which includes the followup question, “Does Anybody Really Care?”

Does Anybody Really Know What Time It Is? No.
Does Anybody Really Care? Yes.

(at which point I paused for comedic effect, as if this were the end of the talk. I crack myself up sometimes)

The basic point of the first answer is that there is no predefined “truth” for what time it is. There are choices/decisions that go into that determination, so the time is a voted quantity in addition to being a measured quantity — measurement limitations are not the only reason the answer is “no”.

For the second question, which is the whole motivation for precision timekeeping, the answer had better be “yes” or else there is no justification for performing the task. The motivation for the navy (both here and abroad) for timekeeping is navigation, and this dates back to Harrison and the “longitude problem”. To know your latitude it’s fairly straightforward — the north star is almost due north, so finding its angle in the sky relative to the horizon gives you that information, or you can get the information from the declination of the sun at noon. But the longitude isn’t so easy; for a long time navigation was done by dead reckoning, but with increased ocean travel and the reach of the British Empire there was too much “dead” in dead reckoning, and so the British navy sought a way to improve navigation.
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Sorry About That, Chief

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BREAKING NEWS: Error Undoes Faster-Than-Light Neutrino Results

According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos’ flight and an electronic card in a computer. After tightening the connection and then measuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed. Since this time is subtracted from the overall time of flight, it appears to explain the early arrival of the neutrinos. New data, however, will be needed to confirm this hypothesis.

Boom Boom

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The disposal of drums of sodium into Lake Lenore, an alkaline lake in the Grand Coulee area of eastern Washington State, in 1947 by the War Assets Administration.

Wanna dispose of some sodium? Na.

[A]fter WWII, the US government found they had some extra sodium no one wanted, so they disposed of it.
In a lake. Full of water. And by the way, it was ten tons of pure sodium.

Safety and environmental impact disclaimer

Oh, and all that surplus WWII sodium? While that would destroy the ecology of a lake, in this case it was already a heavily alkaline lake with no fish in it. While I wouldn’t say this was a great thing to do, at least they thought to minimize the impact. But cripes: don’t try this at home.