You were vacationing in Greenwich and bought a watch. You then boarded a ship to
ID: 158088 • Letter: Y
Question
You were vacationing in Greenwich and bought a watch. You then boarded a ship to go on a cruise. You never reset your watch.
Unfortunately, the weather turned poorly and you were shipwrecked on an island. Luckily, the ship’s food stores washed up with you, including a bottle, and everyone else on the cruise.
One day, when it was noon on your island, your watch read 5:30 PM back home. That night, you saw the North Star 30° above the horizon at the beach.
You saved the day by figuring out your latitude and longitude, writing it on a note, and casting your message adrift, in an empty bottle.
What is your latitude? __________________________
What is your longitude? __________________________
Make a sketch to the right, showing where you are with respect to Greenwich.
Show the time and longitude at each location.
Explanation / Answer
The observer's latitude is defined by the declination going through the observer's zenith.
If it is the equinox, then the Sun is on the celestial equator (declination = 0).
If the altitude at local noon (meridian transit) is 30 north, then you are in the northern hemisphere.
The angle between the Sun and your zenith is 90-30 = 60
Therefore, the declination going through your zenith is 60N.
That is your latitude.
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b. Now for Longitude, Ignoring the time equation
the sun crosses the meridian at 12.00 local time.
If your UT clock shows 5:30, then you are 5.30 hours west of longitude 0.
360 degrees = 24 hours
therefore 5.30 hours = 79.5 degrees.
You are at 79.5-60 = 19 N 5 deg
c. in google , 378 nautical miles Southeast of the Big Island (Hawaii).
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