Why is the length of days different in different seasons?

Question

i know that in summer the days are longer and in winter they are shorter but i don't know how this happens.... i know its something to do with the sun and earth.

Answer 1

thats because the sun is at different location actually because the earth is moving around the sun therefore causing the illusion the sun is moving. also because the earth tilt on its axis so the sun's location in the sky is different causing the shadow to be different. just like morning, noon and night the shadow is different

Answer 2

The Earth spins on an axis as it revolves around the Sun. The length of a day stays the same since the spin is constant, but the amount of daylight any given portion of the planet receives changes. In the Summer season the hemisphere receives more light due to the tilt Earth has. During the Winter light becomes scarce and the temperature drops because you are tilted away from the Sun more than in other seasons.

Again, the days length stay the same, but the amount of daylight will change depending on how far you are tilted away from the Sun. The shadow on Earth is simply the portion of the planet not illuminated by the Sun during any given time... Hence night! Your shadow will be stretched if the Sun hangs more in the horizon instead of higher in the sky especially during the Summer and Winter Solstices. During the Spring Equinox the Sun should be at the point where the Day is longer than the night thus your shadow should not be stretched as much.

It all has to do with the tilt of the planet as it spins and orbits the Sun.

Answer 3

It is purely a function of the latitude (+Lambda)of the place and sun's seasonal shift.

First, the pole (N if in morthern hemisphere or S in the southern hemisphere) lifts above at an elevation of Lambda. Let's talk in terms of local 'meridians', those lines joining the pole visible (at elevation Lambda) to the pole below the horizon, at the same depression (-Lambda) at the other end. There is a'noon' (12:00) meridian passing through 'Zenith' (Z). Imagine 2 meridians passing through East (Azimuth 90d) and West (Azimuth 270d). The first one we call '6am' meridian & the other '6pm' meridian. Equidistant between poles (visible & invisble- below horizon) lies the 'celestial equator' (CE) the diurnal path of sun on equinoxes (March 21, Sept 23). You'd notice that CE, connecting E & W is not vertical (not passing through Z) but tilted away from Z by  /_Lambda towards the invisible pole. This presents 2 circles - the 'horizon' and another '6 am/pm' pinjointed at E & W points. I hope we agree that sun crosses horizon at -rise & -set.

I could have drawn it, but for the constraints of 'html'; but one can draw it as per the description above. With the above construction one can imagine the seasonal shift of sun's diurnal path parallel to CE, reaching 23.45d N (measured on 'noon' meridian) on summer solstice (June 21), 23.45d S on winter solstice (Dec 23) as the limits. Near hemispheric solstice (N for northern summer & vice versa) the 6am meridian being lifted above the horizon implies sun rise (on horizon) before 6am. At W end the same thing happens & sunset (on horizon, obviously) happens later to 6pm.

The spherical triangle (let's designate it as 'a b c') -E (or W), the sun's positions on horizon & the timing, and on 6am (or 6pm) can be solved to get the time differential from 6am (6pm) and sun's azimuthal deviation from E (90d Az) or W (270d Az). Sun doesn't rise in exact E (or set in W) except on equinoxes giving rise to shadow lengthening or shortening.

The lateral shift parallel to CE in degrees is given here as 'b'

Tan b = Tan i * sin d

where i=23.45d (axis inclination of earth)

d= days after spring equinox(Mar21)X(360/365.25) in angle.

The advance (or delay) to/from 6am/pm in angle is 'a', which angle can be translated into time @ 4minutes of time/every degree of arc (angle). The azimuthal shift from E/W is 'c' and the angle between a & b sides is right angle.

In the winter (of the particular hemisphere), this triangle is below the horizon and all quantities mentioned above reverse their signs.