If you live on or near the East coast of the US and you've been wondering why it's been so cloudy lately, here's the reason:
That's a low-pressure system that's been squatting over the Great Lakes region for a few days, as seen by NASA's Aqua Earth-observing satellite [click to centrifugenate]. It stretches clear across the country north-to-south; you can see the Gulf of Mexico at the bottom of the picture. Why is it comma-shaped? Because the Earth rotates. Seriously. The Earth spins once per day, and is about 40,000 km (24,000 miles) around at the Equator. That means someone standing there makes a circle that big once per day, moving at a velocity of about 1700 kph (1000 mph). But someone standing at the pole isn't making a circle at all; they would just spin in place once a day. At an intermediate point, say a latitude of 45°, ...
