Thunder Bay is a bay in the U.S. state of Michigan on Lake Huron. The bay extends from North Point at 45° 01' 19" north latitude, 83° 15' 58" west longitude to South Point at 44° 53' 00" north latitude, 83° 18' 51" west longitude.
The city of Alpena lies at the mouth of the Thunder Bay River at 45° 03' 48" north latitude, 83° 25' 41" west longitude. The entire bay lies within Alpena County, with Alpena Township in the north and Sanborn Township in the south.
The name is the English translation of the FrenchAnse du Tonnere, which appears as early as the map of Franquelin in 1688. It was probably derived from the Native American name, as they believed that the Bay was peculiarly subject to thunder storms.
The sound that is eventually heard or detected, thunder, is the sum of many individual acoustic pulses, each a remnant of a shock wave, that have propagated to the point of observation from the generating channel segments.
By the mid-19th century, the accepted theory was that lightning produced a vacuum along its path, and that thunder was caused by the subsequent motion of air rushing to fill the vacuum.
In the 20th century a consensus evolved that thunder must begin with a shock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel.
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