Christy Hovanetz, Ph.D., is a Senior Policy Fellow for ExcelinEd focusing on school accountability and math policies.
On August 7, 1789, the Lighthouse Act became the ninth act of America’s first Congress. Signed into law by President George Washington, the act called for a federal role in building new lighthouses. It also transferred state responsibility for the nation’s 12 existing lighthouses to the federal government for support, maintenance and repair.
Exactly two hundred years later, on August 7, 1989, federal recognition again shined on lighthouses. President Ronald Reagan established that date as National Lighthouse Day by signing into law a joint resolution of the 100th Congress.
Lighthouses represent a nostalgic and storied history in America, standing on shorelines from the Atlantic Ocean to the Pacific, from the Great Lakes to the Gulf Coast. Their role in navigation began with one structure, the Boston Light, built in 1716 and illuminated by candles—and tended around the clock by a lighthouse keeper. Today’s lighthouses, now numbering more than 700 throughout the U.S., are electric and fully automated.
Lighthouses have changed over time, but one thing hasn’t: Math is required to determine a lighthouse’s optimal height.
To be an effective navigation tool, a lighthouse’s beam must be high enough for a mariner to see and make navigational corrections before encountering danger. Heights for shining the beam vary based on location, coastal hazards and climate.
To determine the optimal height for shining the beam, trigonometry is used to calculate the distance to the horizon. The calculation accounts for Earth’s curvature, which limits the geographic horizon, and also the height of the observer, standardized at 15 feet above water level. This determines how far out to sea the light will be visible to the mariner.
The Cape Hatteras Lighthouse is the tallest lighthouse in the United States, measuring 210 feet. The light emitted from the tower at 192 feet above the water line can be seen 20 nautical miles away.
Even now with modern GPS navigation, lighthouses remain active aids used by mariners. Plus, they are often stunning structures in picturesque settings—maybe you even visited one this summer.
Be a beacon for math policy. Read and promote ExcelinEd’s math policy fundamental principles and comprehensive K-8 math model policy based on the National Mathematics Advisory Panel report. They’ll transform math education and help every student shine!
Did you know?
Michigan has 3,280 miles of shoreline, more than any state except Alaska. Its shorelines border four of the Great Lakes, one of the nation’s busiest waterways. It’s no wonder Michigan has 121 lighthouses—more than any other state!
