Example (in Boston): When measuring the Sun at 11am, you find that the compass reads 165° Calculations: Local time: 11:00 am 165° (measured) Local bearing of the sun: Greenwich Time: 4:00 pm Greenwich bearing of the sun: 180 + (15*4) = 240° Local Longitude: 240° -165° = 75° Reflection: In the 1600s, this fairly simple measurement was nearly impossible to make, not because they know how but because they have a way to know what time it was back in Greenwich didn’t didn’t with any reliability. Why would not knowing what time it was prevent them from calculating their longitude? If you know what time it is in Greenwich, it is impossible to know the position of the local don’t sun relative to its position in Greenwich. Therefore one cannot calculate his longitude. Pendulum clocks had been invented in the 1600s, they just take a clock aboard a so why couldn’t ship with them and keep it set to Greenwich Time as they sailed? Pendulums would not be able to swing at a regular one-second interval on a pitching and rolling ship. The clock would be unable to keep constant. If the world voted and decided to make the 0° longitude line run through Denver, Colorado, would this affect your ability to make the measurement you made here? Why or why not? The measurement would yield the same calculation, but the numbers themselves would be different.
Example (in Boston): When measuring the Sun at 11am, you find that the compass reads 165° Calculations: 11:00 am 165° (measured) 4:00 pm 180 + (15*4) = 240° 240° -165° = 75° Local time: Local bearing of the sun: Greenwich Time: Greenwich bearing of the sun: Local Longitude: Reflection: In the 1600s, this fairly simple measurement was nearly impossible to make, not because they didn’t know how but because they didn’t have a way to know what time it was back in Greenwich with any reliability. Why would not knowing what time it was prevent them from calculating their longitude? If you don’t know what time it is in Greenwich, it is impossible to know the position of the local sun relative to its position in Greenwich. Therefore one cannot calculate his longitude. Pendulum clocks had been invented in the 1600s, so why couldn’t they just take a clock aboard a ship with them and keep it set to Greenwich Time as they sailed? Pendulums would not be able to swing at a regular one-second interval on a pitching and rolling ship. The clock would be unable to keep constant. If the world voted and decided to make the 0° longitude line run through Denver, Colorado, would this affect your ability to make the measurement you made here? Why or why not? The measurement would yield the same calculation, but the numbers themselves would be different.
03x%20-%20Measure%20Longitude.docx