Photo via http://ow.ly/YuADn
My favorite time of year is fast approaching. I love to see the layers of snow in my yard start to disappear, revealing patches of green. I have a small square of ground near my front door where daffodils make an early appearance every year. Have you ever stopped to think about the reasons behind the change of seasons? This week, I decided to take a closer look at the seasons, and here’s what I found. Enjoy!
Why Do We Have Four Seasons?
Our earth is tilted and orbits around the sun. This means that sometimes the Southern Hemisphere receives more sunlight than the Northern Hemisphere or vice-versa. When it is summer in the Southern Hemisphere, it is winter in the Northern Hemisphere. The earth’s position and the distribution of sunlight dictate the four seasons.
Photo via http://ow.ly/YuBvD
Subtle and Extreme Seasonal Changes
The change of seasons is more dramatic in areas that are farther away from the equator. The amount of daylight and darkness stays the same year round at the equator. Alternatively, there is a drastic change in the amount of daylight during the summer and winter seasons at the North and South poles. Some cities in northern Alaska receive just four or five hours of daylight on the day of the winter solstice.
Autumn to Winter
In autumn, the position of the earth delivers less sunlight to the Northern Hemisphere and more to the Southern. In winter, the Northern Hemisphere is tilted far away from the sun. This brings on cold temperatures as well as snow and ice. In the Northern Hemisphere, the official start date for winter is Dec. 21.
Spring to Summer
As the earth continues to move, there’s an increase in the amount of sunlight experienced in the Northern Hemisphere. The official start date of spring is March 20. By June, the sun is shining directly on the Northern Hemisphere, turning the season to summer.
The Future of the Four Seasons
Scientists have noticed a change in the timing of the seasons. The hottest day of the year as well as the coldest day are occurring earlier than they have in the past. There are many theories as to the cause behind this change. Some scientists say this shift in timing is due to global warming caused by humans, while others say it’s caused by changing wind patterns. In addition, some say that the magnetic pole reversal has something to do with seasonal timing changes. But pole reversal has been a regular occurrence over millions of years and will continue to happen.
The Seasons on Other Planets
I was surprised to learn that other planets experience changes of season, too. But seasonal changes on other planets don’t look the same as they do on Earth. For instance, Venus tilts only three degrees on its axis and has a small orbit. This means the seasons on Venus are short and temperatures don’t vary much. On Mars, there are 687 days in a year, while on Earth, there are 365. This makes the seasons longer on Mars. Plus, Mars’s axis has a larger tilt than Earth does, and Mars doesn’t maintain a regular distance from the sun. The ice caps on Mars grow during the wintertime and melt in the summer. Like Venus, Jupiter’s axis has a slight tilt, resulting in very subtle seasonal changes. But Jupiter is farther from the sun than Venus, which means its seasons are very long. In fact, each season on Jupiter lasts for three years! So be grateful you don’t live on Jupiter, and enjoy the change of seasons here on earth.
Photo of ice caps on Mars, via http://ow.ly/YuCpG