Help with latitude/longitude, etc.?

Question

Hi, I'm taking a class in Oceanography. I'm hoping someone can explain in detail the following sample question so I can use it as a guide for my lab assignment. My lab instructor is not good at explaining what needs to be done.

"What is the time difference to the nearest minute between New York City (40^30'N 73^58'W) and Bergen, Norway (60^24' N 5^20'E)? Convert minutes to decimal fractions of degrees ______ hours / ______ minutes."

Remember, if you can help me, please outline this in steps and details, like an instruction manual. Easiest to understand answer gets 10 points.

Please be nice to me. I'm an arts major and I am fully aware that in matters of science and mathematics, I am severely intellectually challenged.

Thanks in advance for your help.

Answer 1

Two answers:

1. the non-trick answer

2. the trick answer

Non trick:

To convert from degrees-minutes to decimal degrees (both lat and long),

* divide the minutes by 60

* add the resulting decimal to the degrees

Now you will only need the longitudes, convert both to degrees east

* Subtract the NYC long from 360 (that is, 360 - NYC)

Finally, compute the difference in times between the two locations

* Subtract the two longitudes

* If the difference is bigger than 180 degrees, take 360 - difference

* take the result (now less than 180) and divide by 15 (the number of degrees the earth sweeps in an hour): that is the number of hours difference between the two locations.

Trick:

The above answer is a bit wrong, for social reasons.  It answers the question "how many hours apart are high noon in NYC versus high noon in Bergen?"  Of course, our noon does not correspond exactly with the astronomical high noon (sun at its highest point); we have time zones instead.  Thus high noon in Seattle vs. LA (both Pacific time) might be a bit different, but they have exactly the same time (no "time difference" in our usual way of telling time).  

The clever answer, if you think your teacher is trying to trick you, is to simply look at the time zones in the two places and subtract.  

Answer 2

Every 15 degrees of longitude equal 1 hour time difference. With that, the rest of the math should be easy.

Answer 3

First, you need the longitude difference from New York to Bergen.

73 deg 58 min West = -73 - 58/60 = -73.96667  (West is negative)

5 deg 20 min East = +5+20/50 = +5.33333 (East  is positive)

The difference is 79.3 degrees.

360 degrees is 24 hours, so the time difference is 79.3 x (24/360) = 5.28666 hours = 5 hours + (0.28666 x 60) minutes

= 5 hours 17.2 minutes.

The sun rises first in Bergen, then about 5 hours and 17 minutes later, it rises in New York.  So when it is 5:17 am in Bergen, it is midnight in New York.

(P.S.  This is solar time, not legal time.  The difference in legal time is a whole number of hours.)