Because of the axial tilt (obliquity) of Earth, our planet circles the Sun on a slant, which means that various parts of the globe point toward or away from the Sun at different times of the year. Definitions and terminology used in astronomy Around the June solstice, the North Pole is inclined toward the sun, allowing the Northern Hemisphere to receive more direct sunlight. At the December solstice, the North Pole is inclined away from the sun, allowing the Northern Hemisphere to receive less direct sunlight. The amount of daylight changes throughout the year with maximum lengths of 12 months each at either end of the spectrum - spring and fall. These seasons affect what can be seen from Earth and how it changes over time.
As well as being affected by where you are on Earth, the appearance of the sky is also determined by the weather. If it's windy or not, if it's cloudy or not, and if it's night or day when you look up into the sky - all these things can influence what you see. For example, if it's foggy or not there may not be any clear stars because there aren't any lights bouncing off clouds to reflect back towards us as we watch TV together after dark. Fog also affects what we can see on Earth during daytime, especially in coastal areas where it is common for skies to be completely obscured for large parts of each day.
The weather also has an impact on the colors of the sky. If it's clear out there then you will see white clouds against a blue background.
Seasons are caused by the orientation of the Earth's axis in relation to the Sun. The tilt of the Earth's axis remains aligned with the North Star while the Earth circles the Sun. SUMMER IN THE NORTHERN HEMISPHERE The North Pole is inclined toward the sun, and the sun's rays hit the northern hemisphere more directly in the summer. Because the ground under the sun's rays is warmer than the air above it, heat builds up and causes changes in the weather. In the northernmost parts of Canada and Alaska, this effect is strong enough to cause glaciers to melt and rivers to flow.
WINTER IN THE SOUTHERN HEMISPHERE The South Pole is inclined away from the sun, and the sun's rays hit the southern hemisphere more directly in the winter. The coldest part of Antarctica is located here, so ice forms over most of the continent in the winter.
SEASONAL CHANGE In the northern hemisphere, the days get longer as we move away from the north pole toward the equator. This is because the angle between the Earth and the Sun gets smaller as we go south. At the same time, the nights get shorter because the Earth is moving farther from the Sun during its orbit around it. So even though it is winter in the southern hemisphere, it will soon be spring there as well. Why don't we have four seasons instead of two? The reason we only have two seasons is because of the way that the direction of the Earth's axis has changed over time.
As we move through the year, different portions of the Earth receive direct sunlight. As a result, sometimes the North Pole tilts toward the Sun (as in June) and occasionally the South Pole tilts toward the Sun (like in December). As a result, the seasons. The angle at which the Earth's axis forms with respect to the orbit of the Sun around it is called its tilt. The Earth's orbit is elliptical, not circular; thus, it has an inclination with respect to the plane of the ecliptic, the path that the Earth follows as it orbits the Sun. This means that at any given time, some parts of the planet are in darkness while others are exposed to light from the Sun.
The tilt of the Earth's axis causes differences in climate between the northern and southern hemispheres. During part of each year, most of Northern Europe is in daylight, but much of Australia is in darkness. In contrast, during part of each year, most of Australia is in daylight, but much of Northern Europe is in darkness.
The tilt of the Earth's axis is one of the main factors governing the length of the day and seasonality of climate on Earth. Long before humans arrived on the scene, natural phenomena such as solar eclipses and volcanic eruptions caused by movements of the Earth's core led to changes in the amount of sunlight reaching various regions of the planet. These changes in turn affected the temperature and climate there.
The Earth's axis is tilted at 23.5 degrees from perpendicular, which means that when the Earth revolves the Sun over the course of a year, the angle of the Sun's rays varies at any given place. Seasons fluctuate as a result of variations in angle toward the sun and the accompanying solar energy. When the angle between the Earth and the sun is 90 degrees (direct sunlight), winter comes when the temperature drops below 0 degrees Celsius (32 degrees Fahrenheit). At this time of year, the days are short and cold, with little light left after sunset. The polar regions experience four seasons in two years because of the rotation of the earth acting on the sunstroke principle. As soon as spring arrives at the equator, it grows hotter and drier there, while further north it gets colder and more rainy.
As for the tropics, they have only one season all year round: the rainy season. During the dry season, there is no water anywhere near the surface of the ground. But just as the rainy season begins, so too does the summer season. It too is short - about nine months - but very hot and humid, with frequent rainstorms. Seeds from plants that grow well with such conditions produce spores in large numbers, so that when the wind blows them around, new plants can grow from these spores far away from their original location.