Guest Apocalypse Posted February 21, 2005 Share Posted February 21, 2005 (Sorry if I posted this in the wrong section) What is the longest day on Earth? I know it's different depending on where you live but my friend was telling me that tomorrow as in 22nd February (I'm from Australia by the way) is the longest day because the moon's gravitational pull is slowing the Earth's spin at the moment. Is this true? I always thought that the longest days were when the Summer Solstice occurs (Approx. 22nd December in Southern Hemisphere and approx. 21st June in Northern Hemisphere) Confuzed plz help Link to comment Share on other sites More sharing options...
Newtonian Posted February 21, 2005 Share Posted February 21, 2005 Your friends wrong,your right. In the northern half of the world, June 21st is the first day of summer and the longest day of the year. (Actually, summer "arrives" at 0148 UT on June 21st, which is 9:48 ET June 20th, so the solstice occurs during the night of the 20th,the 21st is still the first full day of summer. To the south, across the equator, winter arrives.June 21st will be the shortest day of the year. The coldest weather of the year is on its way, and winter sports are prepared for. Again in the north the vernal equinox(12 hours day /night)begins around March20,first day of spring here,autumn south of the equator. Thats about my limit,so i hope ive armed you with enough info to beat your friend up with Link to comment Share on other sites More sharing options...
jdurg Posted February 21, 2005 Share Posted February 21, 2005 That's if you define 'day' as the number of hours in which the sun is present, which depending on where you live can be up to 6 months. If you define 'day' as the time it takes for a full revolution of the Earth, then I'm not sure exactly when that is. (The 'day' you are defining Newtonian is caused by the tilt of the earth on its axis as it moves around the sun). Link to comment Share on other sites More sharing options...
swansont Posted February 21, 2005 Share Posted February 21, 2005 If you define 'day' as the time it takes for a full revolution of the Earth, then I'm not sure exactly when that is. (The 'day' you are defining Newtonian is caused by the tilt of the earth on its axis as it moves around the sun). If you define it as 'revolve so the sun goes from overhead to overhead' then I think it's in early January/July for southern/northern hemispheres. The earth's orbit is slightly eccentric and the perihelion (point of closest approach) is in early January. So the earth is moving faster and covers a greater distance along its arc, and thus must rotate through a slightly larger angle to return to solar noon. The slowing of the earth's rotation from tidal friction is a separate effect. The earth's rotation has actually been speeding up lately. Link to comment Share on other sites More sharing options...
Newtonian Posted February 21, 2005 Share Posted February 21, 2005 That's if you define 'day' as the number of hours in which the sun is present, which depending on where you live can be up to 6 months. If you define 'day' as the time it takes for a full revolution of the Earth, then I'm not sure exactly when that is. (The 'day' you are defining Newtonian is caused by the tilt of the earth on its axis as it moves around the sun). There's always one Link to comment Share on other sites More sharing options...
Janus Posted February 21, 2005 Share Posted February 21, 2005 According to a solar calculator I found, the longest Solar day of 2005 falls on Dec 23 with a length of 24h 0m 29.9 s The shortest Solar day falls on Sept 17 with a length of 23h 59m 38.6s Link to comment Share on other sites More sharing options...
Ophiolite Posted February 22, 2005 Share Posted February 22, 2005 According to a solar calculator I found, Could you give us the link please. There's always one No' date=' two.. Jdurg just beat me to the important clarification.[img']http://www.scienceforums.net/forums/images/icons/icon7.gif[/img] Link to comment Share on other sites More sharing options...
Newtonian Posted February 22, 2005 Share Posted February 22, 2005 To clarify my answer to Apocalypse question. http://www.jpl.nasa.gov/news/features.cfm?feature=550 I understand the confusion that in arctic regions there is up to 18hours daylight up to 6 months of the year.However there is no contradiction,summer solstice is factually the longest day wherever you are Northern/southern hemisphere.Only the months change. If you are in the arctic,you just happen to get even more daylight(19hrs 22 min,june21,2004) Link to comment Share on other sites More sharing options...
Janus Posted February 23, 2005 Share Posted February 23, 2005 Could you give us the link please. http://www.gcstudio.com/suncalc.html Just type in a range of Jan 1, 2005 to Dec 31, 2005 in steps of one day. The calculator will generate a list with all kinds of facts for each date, including the length of the Solar Day. Link to comment Share on other sites More sharing options...
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