smartereveryday:

Wow… and actual volcano explosion shock wave.  Insane.  Hey!  We can do math on this!

The explosion happens at 0:12 seconds in, and the shock wave hits at 0:25 seconds.  13 seconds for the shock wave to hit the boat.

The speed of sound at sea level is 331.5 m/s (741.5 mph)

Velocity = Distance / Time

Therefore

Distance = Velocity x Time

Distance = 331.5 m/s x 13 seconds: = 4,309.5 meters

Ok.. so now we know the distance to the volcano… we can assume:

Density of the air at sea level = 1.224 kg/m^3

Speed of sound = 331.5 m/s as above

r = 4,309.5 meters from math….

If we had a calibrated microphone on the camera we could use the following equation from the paper "Generation and propagation of infrasonic airwaves from volcanic explosions"  to calculate the pressure in the volcano at the moment of explosion.

Acoustic Energy Equation

My raw notes for posterity.

idadarksky:

The Bortle Scale

The Bortle scale is a nine-level numeric scale that measures the night sky’s brightness of a particular location. It quantifies the astronomical observability of celestial objects and the interference caused by light pollution. John E. Bortle created the scale and published it in the February 2001 edition of Sky & Telescope magazine to help amateur astronomers evaluate the darkness of an observing site, and secondarily, to compare the darkness of observing sites. The scale ranges from Class 1, the darkest skies available on Earth, through Class 9, inner-city skies.

(Source: Wikipedia)

Reblogged from quantumaniac

More than one person in the streets of Ferguson has compared what is happening here to the chaotic days of the Birmingham desegregation campaign in 1963. And, like that struggle, the local authorities, long immune to public sentiment, were incapable of understanding how their actions reverberated outside the hermetic world where they held sway—how they looked to the world. That incomprehension was the biggest asset the protesters in Birmingham had. Michael Brown was left lying in the street for hours while a traumatized community stood behind police tape in frustration, grief, and shock: an immobile metaphor for everything that was wrong in Ferguson, Missouri.
New Yorker contributor Jelani Cobb compares the situation in Ferguson to a key moment in civil rights history. (via shortformblog)