Why are the first days of summer and winter called the solstices?

Answer 1

Earth's rotational axis is tilted. Thus as it orbits the sun the length of the day varies. In either hemisphere the daylight hours are shortest during the winter season, and longest in the summer.

The length of the full day/night cycle does not vary by season, but is affected (very minutely) by other factors.

Answer 2

The summer and winter solstices occur when the earth tilts on it's axis. The sun crosses the line of the Tropic of Cancer (summer) and Capricorn (winter).The winter solstice is the shortest day of the year. The summer solstice is the longest day of the year.

Answer 3

The winter solstice is the shortest day of the year. In the northern hemisphere, this is generally around December 21, but this can vary a day either way depending on the cycle of leap years. In the Southern Hemisphere, the winter solstice occurs around June 21.

Answer 4

That completely depends on where you are.

-- On the equator, the difference is very small.

-- As you move farther from the equator either north or south,

the difference becomes greater.

-- At the north and south poles, every day is the same length,

namely 6 months, followed by 6 months of night.

Answer 5

Due to the tilt of the Earth's axis. At some times a greater portion of the latitude an observer on Earth has is illuminated and so it remain in sunlight for a larger portion of the revolution of the planet.

Answer 6

On or around June 21 each year, the rays of the sun will be perpendicular to the Tropic of Cancer at 23°30' North latitude. This day is the summer solctice in the Northern Hemisphere. On this day, the earth's "circle of illumination" will be from the Arctic Circle on the far side of the earth (in relation to the sun) to the Antarctic Circle on the near side of the earth. The equator receives twelve hours of daylight, there's 24 hours of daylight at the North Pole and areas north of 66°30' N, and there's 24 hours of darkness at the South Pole and areas south of 66°30' S. June 20-21 is start of summer in the Northern Hemisphere but simultaneously the start of winter in the Southern Hemisphere. It's also the longest day of sunlight for places in the Northern Hemisphere and the shortest day for cities south of the equator. However, June 20-21 is not the day when the sun rises earliest in the morning nor when it sets latest at night. As we'll see - the date of earliest sunrise or sunset varies from location to location. as sun's rays fall perpendicular to tropic of cancer the sunlight remains in the northern hemisphere for a longer time which causes the longest days

Answer 7

Actually, it is the other way around; the winter solstice in the SHORTEST day (and longest night) of the year, while the summer solstice is the longest day and shortest night of the year.

The reason is because the Earth's axis is tilted. Because the Earth spins like a gyroscope, the Earth maintains its same tilt all the time, and because the Earth is also orbiting the Sun, sometimes the tilt has the north pole closer to the sun and the south pole away, and 6 months later the north pole is pointed away while the south pole is pointed closer to the sun. (The poles never point right AT the sun.)

The time when the north pole is pointed as close to the Sun as it ever gets is the summer solstice in the northern hemisphere and is called the winter solstice in the southern hemisphere.

Answer 8

The shortest day of the year is the Winter Solstice, which is December 21 or 22 in the northern hemisphere.

South of the equator, the Winter Solstice happens on June 21 or 22. (The exact date depends on the cycle of leap years.)

Answer 9

The tilt, the whole tilt, and nothing but the tilt... and the elliptical orbit of earth, actually. If there were absolutely no tilt to the earth's axis, and if earth's orbit were perfectly circular, then the periods of daylight and night time would be fixed throughout the year, for any location. But our axis tilts close to 23.5 degrees, and our orbit is elliptical. The way all this works out is more complex than you might think. The basics: Imagine a classroom globe tilted at 23.5 degrees; it is in front of you. Your line of sight to the globe makes a 90 degree angle with the direction of a light source on the globe. You observe the edge between the lit and shadowed parts of the globe to be a line perpendicular to the floor. The 'north pole' of the globe is pointing toward the dark part of the room. As you imagine the globe spinning you can see that north of the equator, locations will spend longer in shadow than locations at the equivalent latitude in the south. You can 'see' that if the pole were pointed straight up, all locations except those extremely close to the poles would have fixed and equal periods of daylight and night time. The elliptical orbit idea may be a little harder to imagine. When a planet is in an elliptical (like an oval) orbit, it is sometimes closer to the sun and sometimes farther away. When it is closer, it is moving more rapidly in its orbit, and when it is farther away it is moving more slowly in its orbit. The moment of closest approach is 'perihelion' (I remember this by thinking-- close to the sun? Peril!) and the moment of farthest approach is aphelion. Now the (counter clockwise) spin of the earth on its axis is relatively constant. This isn't easy to visualize-- but imagine the earth moving very rapidly during part of its counter clock-wise orbit, and you want to measure the time from one solar noontime to the next. You can see that the earth will have to spin a bit more in order to 'move' the sun into position for the next noontime. The earth actually has to rotate MORE than one full turn in order to go from one solar noon to the next. Now the idea is that when the earth is at the other end of its orbit and moving through its orbit more slowly, the earth still has to rotate more than one full rotation to go from one solar noon to the next, but not as much as when the earth is moving more rapidly. So this adds to the effect of different periods of daylight and night time, since the actual length of the solar day is changing throughout the year.

Answer 10

The Earth is tilted as it moves around the sun. It rotates around the sun every 365.25 days and spins on its axis once every 24 hours. The Earth's axis, a line extending from the Earth's north and south poles is tilted 23.5 degrees. As the Earth reaches a particular point in its orbit about the sun, the northern hemisphere tilts towards the sun while the southern hemisphere tilts away from it. The imaginary line that divides the Earth into the northern and southern hemispheres is the equator. Michigan is in the northern hemisphere. The season when we are tilted toward the Sun is out summer. During our summer, the daylight lasts more than 12 hours because the sun is at it's northernmost position from the equator. During winter, daylight lasts less than 12 hours for the north because the sun is at its southernmost position from the equator. The farther north from the equator you are, the shorter the daylight hours.