Highlights of US Women’s National Soccer Team vs. Japan, March 5th, 2014
posted @ 06:03 PM EST
about life, the universe, and everything
posted @ 12:10 PM EDT
The “curly” B-modes of polarization in the cosmic microwave background. Each line is a measure of polarization at one point on the sky. When the larger E-mode polarization is subtracted, this is what’s left. Nearly all of it is the signature of quantum-gravitational chaos in the first instant of the Big Bang. This is an actual map of the sky near the south galactic pole, about 15° tall, crossing the constellations Phoenix and Tucana. The strongest curl patterns (emphasized with colors) are a couple of degrees wide, roughly the size of your thumb held at arm’s length against the sky.
posted @ 07:52 AM EDT
It’s the vernal equinox today at 12:57 PM EST, when the center of the Sun is in the plane of the Earth’s equator. So, why aren’t the lengths of day and night equal? Look up the times of sunrise and sunset today and you’ll see that the time between sunrise and sunset is longer than twelve hours, which is due to two things.
First, the convention for specifying the time of sunrise holds that it is when a bit of the Sun first appears above the horizon. Likewise, the time of sunset is when the last bit of the Sun disappears below the horizon. These make the day longer by the time it takes the whole (half rising and half setting) Sun to cross the horizon.
Second, the light from the Sun is refracted by the Earth’s atmosphere, making the Sun appear above the horizon when it is actually just below, in the same way that the stopper at the bottom of a sink filled with water looks to be higher (the sink looking shallower) than it is. The displacement of the Sun’s image near the horizon is slightly larger than its angular size, making the day longer by twice (rising and setting) the time it takes the Sun to cross the horizon.
posted @ 06:57 AM EDT