The direct sunlight point is the surface of the earthsunlightThe place with an angle of incidence (i.e., the solar altitude angle) of 90 degrees, which is the center of the earth andcenter of the sunThe intersection of the line and the earth's sphere.Of the meridian where the direct solar point is locatedLocal timeIt is 12:00 noon.
Chinese name
Subsolar point
Light
Solar light incident on the earth surface
Angle
90 degrees
Location
The intersection of the line between geocentric and heliocentric and the earth's sphere
Summer Solstice
The direct sunlight point is at the Tropic of Cancer
Winter Solstice
The direct sunlight point is at the Tropic of Capricorn
The direct sunlight point is the place where the incidence angle of sunlight on the surface of the earth (i.e. the solar altitude angle) is 90 degrees, which is the center of the earth andcenter of the sunThe intersection of the line and the earth's sphere.The local time of the meridian where the direct sunlight point is located is 12:00 noon.The activity rule is: at the vernal equinox (around March 21), the direct solar radiation point is at the equator (0 °), and then moves northward.the summer solstice(around June 22)the Tropic of Cancer(23 ° 26 ′ N), and then move southward.At the autumnal equinox (around September 23), the point of direct solar radiation is at the equator (0 °), and then continues to move southward.At the winter solstice (around December 22), the direct sunlight point isTropic of Cancer(23 ° 26 ′ S), and then move northward.
Geographical significance:
one
The movement of the direct solar radiation point causes changes in the global heat distribution.
two
Driven by the seasonal movement of the direct sunlight pointPlanetary systemThe north-south offset of.
3. The seasonal movement of the direct sunlight point causes the change of the length of day and night and the noon sun height.
Activity pattern
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The point of direct sunlight moves westward every hour, passing 15 degrees longitude every hour.In the calculation of geography problems, we can roughly take 0.25 degrees of latitude per minute.
At the vernal equinox, the point of direct sunlight is at the equator, and then moves northward until June 22 (i.ethe summer solstice）To the Tropic of Cancer.the summer solstice, the solar direct point is on the Tropic of Cancer, and then moves southward until September 23 (the autumnal equinox) to the equator.At the autumnal equinox, the direct point of the sun is at the equator, and then continues to move southward until December 22 (winter solstice) to the Tropic of Capricorn.At the winter solstice, the direct sunlight point is at the Tropic of Capricorn, then moves northward, and returns to the equator on March 21 (the vernal equinox).The cycle of the return movement is 5:48:46 on 365 days, which is about 365.2422 days, called a return year.[1]
according toKepler's law, the earth isElliptical orbitThe sun revolves around the sun. The sun is at a focus of the ellipse. Thus, perihelion andApohelion。Focusing on the sun,Earth movementThe area swept per unit time is equal.
At the beginning of July, the earth is farthest from the sun,Northern HemisphereThe days are long and the nights are short, andsouthern hemispherecontrary.After JanuaryPerihelion, short days and long nights in the Northern Hemisphere.
At the beginning of July, the heliocentric distance between the sun and the earth was 152.1 million kilometers, and the angular speed was 57 minutes/antenna speed was 29.3 kilometers/second
