英语时差：太阳黑子

Sunspots occur at places where the sun’s irregular magnetic field is highly concentrated. The sun’s surface is usually reheated by a continual flow of hot material from deep inside the sun. However, a strong concentration in the magnetic field can interfere with this reheating flow. Sunspots are therefore slightly cooler and darker than their surroundings. Because the sun’s magnetic field reverses regularly, the concentration of sunspots also follows an eleven year cycle. At the height of this cycle there can be as many as a hundred spots a day, some larger than the Earth itself. During quieter parts of the cycle, the sun can be completely unblemished. Don’t try to look for sunspots yourself, even through sunglasses. It is especially dangerous to look at the sun through binoculars, a telescope, or a camera. The only safe way to see what sunspots look like is to find a picture of them.