"Solar minimum" is defined as the period of least solar activity in the 11-year cycle of the Sun.
This essentially means there are fewer sunspots and solar flares for a while. It usually does not last for long and is not a cause for concern.
But back in the 1600s, a solar minimum lasted for 70 years. During that time of low solar activity, temperatures on Earth dropped.
Scientist are not positive there is a connection — it might have been volcanos, or something else.
During this time, which we call the Maunder Minimum, the winters were significantly longer and the summers were somewhat cooler.
Consequently, trees grew very slowly. In wood from this period, you can hardly see annual rings.
As I understand it, wood that has slow, even growth has the properties required for high-quality sounding boards in musical instruments.
The Maunder Minimum started in the year 1645. Antonio Stradivari was born in 1644.
By the time he reached what is called his “golden period” of instrument making, spruce wood unlike any before or since was available.
This may just be a coincidence, and, without a doubt, he was a master violinmaker, but in the period of a solar minimum, Stradivari crafted instruments of maximum quality.