The Naked Scientists

The Naked Scientists Forum

Author Topic: Daylight problems  (Read 3494 times)

Offline Lusky

  • First timers
  • *
  • Posts: 2
    • View Profile
Daylight problems
« on: 20/05/2005 00:48:35 »
There is the same amount of daylight (on the equator) in summer and winter. Please, in basic words, could you explain why this is?






P.S. Atheists rule


 

Offline Bass

  • Neilep Level Member
  • ******
  • Posts: 1338
  • Thanked: 5 times
    • View Profile
Re: Daylight problems
« Reply #1 on: 20/05/2005 01:42:51 »
The equator always has 12 hours sunlight and 12 hours dark each day.  The equator is the only great circle perpendicular to the earthís axis of rotation.  No matter what time of year, the great circle of the equator will bisect the great circle of the sunís illumination (think of a half moon)- so it will always remain half in the circle of illumination and half out- 12 hours each.

Prediction is difficult, especially the future.  -Niels Bohr
 

Offline daveshorts

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 2583
  • Physics, Experiments
    • View Profile
    • http://www.chaosscience.org.uk
Re: Daylight problems
« Reply #2 on: 20/05/2005 12:09:42 »
Take an orange (or the household spherical object of your choice), then draw a line around the middle like an equator. now light the orange from one side - you will find that the shadow will take up exactly half of the line wherever you light it from (not including the top or bottom). so if the earth is rotating with this line as an equator  you will spend 12 hours in daylight and 12 in dark, however the earth is orientated.

The reason why other places don't have 12 hours of day and 12 of night is that they are moving around smaller circles so the above no longer holds.
 

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • Posts: 20602
  • Thanked: 8 times
    • View Profile
Re: Daylight problems
« Reply #3 on: 20/05/2005 13:51:35 »
quote:
Originally posted by daveshorts

Take an orange (or the household spherical object of your choice), then draw a line around the middle like an equator. now light the orange from one side -



I tried that but the juice kept putting the flame out :D...ok, I think it's time for my medication...;)

Men are the same as women.... just inside out !!
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Re: Daylight problems
« Reply #4 on: 20/05/2005 19:26:48 »
quote:
Originally posted by Bass

The equator always has 12 hours sunlight and 12 hours dark each day.  The equator is the only great circle perpendicular to the earthís axis of rotation.  No matter what time of year, the great circle of the equator will bisect the great circle of the sunís illumination (think of a half moon)- so it will always remain half in the circle of illumination and half out- 12 hours each.



Sorry, but that's not quite the case. The sun @ midday moves between the 2 tropics. Therefore @ the equator you get 2 longest days each year - 1 as the sun passes the equator moving south to north, & another as it moves back south again. The days average 12 hours, but vary from about 11hrs to about 13hrs.
 

Offline gsmollin

  • Hero Member
  • *****
  • Posts: 749
    • View Profile
Re: Daylight problems
« Reply #5 on: 20/05/2005 20:46:28 »
quote:
Originally posted by Lusky

There is the same amount of daylight (on the equator) in summer and winter. Please, in basic words, could you explain why this is?






P.S. Atheists rule



There is the same amount of daylight everywhere on the earth (except the north and south poles) on the spring and autumnal equinox. Then the earth's equator lies in the plane of earth's orbit around the sun. After the spring equinox the equator lies south of the plane of earth's orbit around the sun, and after the autumnal equinox the equator lies north of the plane of the earth's orbit around the sun.

As a result of this, there will be the same amount of daylight time on the northern hemisphere winter and  the summer solstices. There will also be the same amount of daylight time on those days spaced equally from the solstices. However, in the northern hemisphere winter, the sun angle will be to the south of the zenith, and in the summer it will be to the north of the zenith. On the equinoxes, the sun will be at the zenith at 1200 hours.
 

The Naked Scientists Forum

Re: Daylight problems
« Reply #5 on: 20/05/2005 20:46:28 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums