Earth's Tilt 2: Land of the Midnight Sun - Free Educational videos for Students in K-12

Earth's Tilt 2: Land of the Midnight Sun - By MITK12Videos

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00:07	imagine that you live in North America and one day
00:10	you can call up your friend in Norway up by
00:12	the North Pole , you guys are talking and you
00:14	make plans to go visit him next summer . So
00:17	any time next summer works for you , yep .
00:21	Any time is good for me . Okay , how
00:25	about june that summer for you ? Right of course
00:29	in a few months june rolls around and you hop
00:32	on a plane for your Norwegian vacation . You guys
00:35	are hanging out one night when he says mhm I
00:40	think I'm going to head to bed and you say
00:43	come on man the sun is still up , you
00:46	can't go to sleep and your friends like but it's
00:49	midnight . What ? I don't get this . Why
00:52	is the sun is still up in the middle of
00:54	the night here in Norway ? That's a great question
00:58	. I think we can help you out with that
01:03	. If we take a look at the Earth's orbit
01:05	from the side , we see that the Earth revolves
01:07	around the sun in this orbital plane once every year
01:10	. Remember that Earth is tilted at an angle of
01:12	23.5 degrees and it's rotating on its axis once every
01:15	day . At this point in the Earth's revolution ,
01:20	the southern hemisphere is at its maximum inclination towards the
01:23	sun . This is called the december solstice . At
01:28	this point in the Earth's revolution , the northern hemisphere
01:31	is at its maximum inclination towards the sun . This
01:34	is called the june solstice . Let's put a line
01:37	through the Earth that's perpendicular to the orbital plane .
01:40	We know that this angle here is 23.5 degrees .
01:43	That means that this angle here between our vertical line
01:46	and the equator is 90 minus 22.5 degrees . That's
01:50	66.5 degrees . We can draw a circle around the
01:54	Earth at the point where the line perpendicular to the
01:56	orbital plane touches the Earth's surface . This circle is
01:59	66.5 degrees of latitude north of the equator . Wait
02:03	latitude , what's that latitude is a measure of how
02:06	far north or south you are from the Earth's equator
02:09	. If you're zero degrees , then you're right here
02:11	on the equator . If you're 90 degrees north or
02:14	south , you're on one of the polls and if
02:18	you're 66.5 degrees north , like we just talked about
02:22	, you're at what's called the arctic circle , we
02:24	can do the same thing on the southern hemisphere .
02:26	We draw a circle at 66.5 degrees south . This
02:30	is called the antarctic circle . Okay , but how
02:33	does that keep the sun from setting during the summer
02:36	? In Norway ? I think it's best if we
02:38	explain this through an experiment here , we have a
02:41	globe of the Earth Tilted at about 23.5° and we're
02:45	using a flashlight to simulate the Sun . Were wondering
02:48	about summer in Norway . So we have the northern
02:50	hemisphere tilted towards our flashlight , son . Mm I
02:54	don't think that flashlight is powerful enough for this experiment
02:59	. Yeah . There we go . We can see
03:03	that the half of the Earth that's facing the sun
03:06	is lit up . It's daytime on this half and
03:08	nighttime . On the other half . We'll put a
03:11	little flag here on the northern part of Norway which
03:13	is above the arctic circle . And we'll put another
03:16	little flag here in the U . S . Which
03:18	is below the arctic circle . If we start rotating
03:20	the globe , we see that there's a point where
03:22	the sun is no longer shining on the U .
03:24	S . We experience this is sunset . However the
03:28	sun continues to shine on Norway , it's so far
03:31	north that it's always in sunlight . Oh awesome !
03:36	That's so cool . 24 hours of sunlight . So
03:40	much time for fun stuff , skiing , hiking ,
03:44	mini golf . Not in the winter . What do
03:47	you mean ? Let's take a look at Norway .
03:49	In the winter . During this season the northern hemisphere
03:53	is tilted away from the sun . So if we
03:55	rotate the earth we see that the U . S
03:57	. Is in periods of sun , light and darkness
03:59	but we can't see the Norwegian flag at all .
04:02	That means 24 hours of darkness . Sad but true
04:09	. Oh man that stinks . It sure does .
04:13	The same thing happens between the antarctic circle and the
04:16	south Pole too . During their summer they have 24
04:19	hours of sunlight and during their winter they have 24
04:22	hours of darkness . That's crazy . Even if you
04:25	don't live far north or south , the tilt of
04:28	the earth still affects the length of the day .
04:30	If it's the june solstice , we have 24 hours
04:32	of sunlight here above the arctic circle , And 24
04:36	hours of darkness here below the Antarctic Circle . Uh
04:40	so if we were to go a little south to
04:43	the US between the equator and the Arctic Circle ,
04:46	how many hours of daylight do you think we'll have
04:49	less than 24 ? Right ? It's the longest day
04:52	of the year in the northern hemisphere . If we
04:54	continue south until we get to the equator halfway between
04:57	the poles here , we have 12 hours of light
05:00	and 12 hours of darkness . If we go even
05:03	further south to Australia between the equator and the Antarctic
05:07	Circle , how many hours of daylight ? What we
05:09	have ? Less than 12 exactly . This is the
05:14	shortest day of the year in the southern hemisphere .
05:18	The effect is reversed during the December Solstice . There's
05:21	more than 12 hours of daylight below the equator in
05:24	less than 12 hours of daylight above it . So
05:27	now you know how the tilt of the earth causes
05:29	both the seasons and the length of the day to
05:31	change . So it's the tilt of the earth that
05:33	gives us longer days and summer and shorter days in
05:36	winter . Right , awesome . I think it's time
05:41	. It's a celebratory summer . Midnight minigolf , Right
05:44	, partly . Uh yeah , partly for you a
05:51	week .

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