A graph of sunspot numbers from 1700 through 1993, showing the 11-year sunspot cycle.
Click on image for full size
Image courtesy NOAA/NGDC.
Space Weather: Quiet vs. Active Times
We tend to think of the Sun as unchanging. In some ways it is! The Sun rises every morning and sets every night. The amount of light it shines on Earth is very stable from day to day and even over the course of many, many years. But, some things do change about the Sun.
The number and placement of sunspots on the face of the Sun changes over time. The number of sunspots tells us roughly how active the Sun will be. Lots of sunspots means the Sun will be very active and stormy. That means solar flares and CMEs. Very few sunspots means the Sun will be calm. How active the Sun is does affect life here on Earth.
The Sun, like all stars, has changed over the course of its very long life. When it was younger, the Sun was more active then it is now. The Sun has also gotten brighter over its lifetime.
You can go to bed tonight knowing the Sun will rise in the
morning. Remember, though, that tomorrow's Sun will be a tad different that
the one that sets tonight!
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