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Scott Stuart
Lives in Lexington, MA
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Scott Stuart

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There is a leap second coming next week, don't be caught unaware!

Perhaps some day we'll be able to control the Earth's rotation so that it keeps time accurately.  Until then we have to adjust our clocks.
INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS) SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE SERVICE DE LA ROTATION TERRESTRE DE L'IERS OBSERVATOIRE DE PARIS 61, Av. de l'Observatoire 75014 PARIS (France) Tel. : 33 (0) 1 40 51 22 26 FAX : 33 (0) 1 ...
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Stupid moon.  Messing up our rotation.
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Here is a very nicely written explanation of something one normally takes for granted:  metals are shiny.  The reason illustrates how weirdly electrons can behave.

And, like all good physics answers, more questions.  Why are metal atoms willing to share their electrons?  Why are some metals (like gold) colored instead of silver?

The reason for the yellow color of gold has to do with the fact that some of the electrons that are not free to wander the entire metal volume are able to absorb blue (and shorter) photons.  The specific way that the energy levels of these valence electrons in gold differ from those in silver has to do with the increased number of protons increasing the "speed" of the electrons and (via special relativity) the effective  mass of the electrons.  So, I think you could say that the shininess of gold illustrates QM while the color illustrates SR.
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Their first winter summit!
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Yup, and a pretty short hike for short-legged people.
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Here is the result of another outing to see ice in the harbor. I failed to photo the food associated s with this one, bit suffice or to say that the sausage, onion, pepper pie at Santarpio's is worth a trip.
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Finally a clear enough night to see comet Lovejoy! Binoculars required.
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The Twelve Doctors
 
The Twelve Doctor Whos: A Christmas Carol (well, not really.)
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Scott Stuart

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Math/stats question:

If X_i are iid r.v.s that are exponentially distributed with E[X] = mu, and I define Y = sum{i=1..N}{X_i}

then Y has a Gamma (or Erlang) distribution with parameters N, and mu (or mu^{-1} depending how you like to write your Gamma distribution).

Now what happens if N is a random variable with a Poisson distribution with mean, say lambda?  Is there a named distribution for that?

I can generate random variables with this distribution in MATLAB (the accumarray function rocks!), and they match extremely well to my data, and I can even make up some plausible physics for why this is the correct distribution.  It would be much more convenient, though, if I had a nice way to fit for the two parameters (mu and lambda).  Given the huge number of variations on exponential distributions that have been studied, it seems like there is a chance for this to exist.
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Well, I haven't figured out the PDF of this distribution, but using the moment generating functions and MATLAB to verify, I have found the expected value and variance.  Using the notation above, E[Y] = lambda * mu and VAR[Y] = 2 * lambda * mu^2
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Scott Stuart originally shared:
 
Found on the Minuteman Bikeway this morning, in Bedford, about 100 meters NW of the intersection with Wiggins.  There was also a trail meandering through the woods and a field and crossing the bikepath several times.  The trail had an occasionally visible hoof print and an occasionally visible canine track, but was mostly too beaten down and chaotic to interpret.
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+Arun Sannuti More than 1, I suspect.
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We went out to Deer Island in the Boston Harbor this morning to see if the sunrise on the frozen sea would look interesting. It wasn't as frozen as I had hoped it would be, but it was very pretty and slushy.

Afterwards we stopped at Union Square Doughnut. I highly recommend the browned butter and hazelnut doughnut, surprisingly more so than the maple bacon doughnut, which was also quite good.
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Why will June 2015 be different from June in most years?  It will be one second longer than usual.
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...ah, no, not nearly.  http://en.wikipedia.org/wiki/Leap_second lists them all, needless to say.  So June was this long in each of 1972, '81, '82, '83, '85, '92, '93, '94, '97, and 2012.  Huh, old news.
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The solar eruption from a few days ago should be hitting the Earth around 8pm EDT tonight.  It probably won't be visible in the Boston area, especially with light pollution and the full moon, but the sky should be very clear so looking up is worthwhile.

(Actually, full moon was a couple of days ago and the moon won't rise until after 9pm, so not too much interference there).
Forecast: Auroral activity will be high. Weather permitting, highly active auroral displays will be visible overhead from Inuvik, Yellowknife, Rankin and Igaluit to Juneau, Edmonton, Winnipeg, Thunder Bay and Sept-Iles, and visible low on the horizon from Seattle, Des Moines, Chicago, Cleveland, ...
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It appears that there might be a new very intense meteor shower in the early morning of May 24, perfectly situated for North American viewers, with minimal interference from the moon, and a Saturday as well.  Of course that means it will be raining.  The dust for this shower was spewed from one of "my" comets (209P/LINEAR) in the late 1800s, and early 1900s.  Unfortunately, there are no observations of the comet from the 1800s to get an idea of how much dust was spewed back then and the Earth has never passed through this debris before, so the intensity of the coming meteor shower is hard to predict:  it could be a dud or a storm.
A new meteor shower spawned by a comet is due to light up the sky next week, with some forecasters predicting up to 200 'shooting stars' per hour, a potentially spectacular opening act for the meteor display.
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Can I join you guys?
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Hissing Cockroach Birth - Pt. 2
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Part 1 - http://www.youtube.com/watch?v=OhOGQINu0lk Madagascan hissing cockroach giving birth. This video was featured on Animal Planet'