Seasons why they occur

The direction of Earth's tilt nearly doesn't change — the two hemispheres point toward the same position in space through the entire year. What does change, as Earth revolves around the Sun, is the position of the hemispheres in relation to the Sun — the Northern Hemisphere points toward the Sun during the northern summer and away from the Sun during the northern winter.

Earth's path around the Sun is not circular, nor is the Sun situated at the center of this path. Instead, Earth's orbit is elliptical, with the Sun closer to one end of the orbital path than the other. Reservations are required for the planetarium and are available on a first-come, first-served basis. More info. Donate Join Tickets. California Academy of Sciences. K-1st 2nd-3rd 4th-5th 6th-8th 9thth. Toggle Close. Search calacademy. Search the Educators section.

Suggested Unit Progression. Download script. Activity 1: Longer Days, Shorter Nights grades View lesson. Activity 2: Photosynthesis Seen From Space grades Activity 3: Why Do Birds Migrate?

Connections to Standards. A: The Universe and Its Stars Patterns of the apparent motion of the sun, the moon, and stars in the sky can be observed, described, predicted, and explained with models. B: Earth and the Solar System 5 The orbits of Earth around the sun and of the moon around the Earth, together with the rotation of Earth about an axis between its North and South poles, cause observable patterns.

These include day and night; daily changes in the length and direction of shadows; and different positions of the sun, moon, and stars at different times of the day, month, and year. The seasons are a result of that tilt and are caused by the differential intensity of sunlight on different areas of Earth across the year.

C: Organization for Matter and Energy Flow in Organisms Plants, algae including phytoplankton , and many microorganisms use the energy from light to make sugars food from carbon dioxide from the atmosphere and water through the process of photosynthesis, which also releases oxygen.

A: Interdependent Relationships in Ecosystems: Organisms, and populations of organisms, are dependent on their environmental interactions both with other living things and with nonliving factors. In this reaction, carbon dioxide and water combine to form carbon-based organic molecules and release oxygen. Cellular respiration in plants and animals involve chemical reactions with oxygen that release stored energy.

In these processes, complex molecules containing carbon react with oxygen to produce carbon dioxide and other materials. California's Environmental Principles and Concepts Principle III: Natural systems proceed through cycles that humans depend upon, benefit from, and can alter. Concept a: Students need to know that natural systems proceed through cycles and processes that are required for their functioning. In summer and winter, these midpoints are called solstices. The summer solstice is the longest day, and shortest night, of the year.

The winter solstice is the shortest day of the year, and the longest night. In spring and autumn, the midpoints are called the equinoxes. At the spring and autumn equinoxes, day and night are the same length. For thousands and thousands of years — right back to the Stone Age — people have known how to work out when the solstices and equinoxes happen throughout the year. Indeed, they built hundreds of amazing stone circles — like the famous Stonehenge — all over Europe, which marked certain times of the seasons across the year.

These days, we even know how to calculate the seasons on other planets. For example, the next Spring equinox on Mars is on the 23rd March. To understand how this works, imagine a small ball representing the Earth moving around a lightbulb the Sun in a circle.

If you have these things at home, you can try this yourself. As the ball moves around the lightbulb, the half closest to the light will be lit, while the other half will be in darkness. One full circle around the lightbulb represents one full year on Earth.

As you move the ball around the lightbulb, try spinning it between your fingertips, so that the light always shines directly onto the equator. If the Earth span like this, day and night would be the same length all year round, and there would be no seasons.