Seasons
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1. Name the four seasons. summer, autumn (fall), winter, spring 2. Are the Earth's seasons caused by the differences in the distance from the Sun throughout the year or the tilt of the Earth's axis? The tilt of the Earth's axis 3. What is the tilt of the Earth's axis (in degrees)? 23.45 degrees 4. During which season do the Sun's rays hit the Earth at the most direct angle? summer 5. During which season are the days the shortest? winter 6. What is the name of the shortest day of the year (and the beginning of winter)? winter solstice 7. What is the name of the longest day of the year (and the beginning of summer)? summer solstice 8. What is the name of a day in which the day and night are of equal duration? an equinox 9. How many times each year do we have days in which the day and night are of equal duration? 2 times 10. What are the names of each of these days? the vernal equinox and the autumnal equinox
The vernal equinox occurs in late March (this is the beginning of spring in the Northern Hemisphere and the beginning of fall in the Southern Hemisphere); the autumnal equinox occurs in late September (this is the beginning of fall in the Northern Hemisphere and the beginning of spring in the Southern Hemisphere). What is a Leap Year? A leap year is a year that has one extra day in it. A leap year occurs roughly every four years. Most years have 365 days, but a leap year has 366 days. The extra day is added onto the end of the shortest month, February; in a leap year, February has 29 days (instead of its usual 28 days). February 29 is called leap day.
Why Do We Have Leap Years? A year is defined as the time it takes for the Earth to orbit around the sun once. It takes the Earth about 365 1/4 days to make one entire orbit around the sun (a day is one rotation around the Earth's axis). By adding one extra day about every four years, the Earth is in the same point of its orbit at the same time of the calendar year each year. Before a leap-year calendar was used, the seasons drifted around the calendar (the drift is about 1/4 day or 6 hours each year). For example, over three hundred years, July would go from summer to spring. Our current calendar is called the Gregorian calendar; this calendar was devised by Aloysius Lilius (an Italian physician) and named for Pope Gregory who decreed in 1582 that it be used in Catholic areas. This calendar wasn't adopted in Britain and the American Colonies until 1752. What Years are Leap Years? Usually, there is a leap year every four years -- but once in a long while, a leap year has to be skipped (this is because the Earth's orbit is 365.242 days, a bit less than 365 1/4). To determine if the year is a leap year: •
•
Non-century years (a century year is a year ending in 00) are leap years if they are divisible by four. For example, 2004, 2008 and 2012 are leap years; 2009, 2010 and 2011 are not. Century years are leap years if they are divisible by 400. For example, 1600, 2000, and 2400 are leap years; 1700, 1800, 1900, 2100, 2200, and 2300 are not.
A List of Some Leap Years A list of some leap years: ...1984, 1988, 1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020, 2024, 2028, 2032, 2036, 2040, 2044, 2048, 2052, 2056, 2060, 2064, 2068, 2072, 2076, 2080, 2084, 2088, 2092, 2096, 2104, 2108, 2112, 2116, 2120, ... Leap Day Birthdays People born on leap day (February 29) can celebrate their birthday on March 1 (or February 28) on non-leap years. A person born on a leap day is sometimes called a leapling. What percentage of the population is born on leap day? Assuming an equal distribution of birthdays throughout the year, the fraction of people born on
leap day is the fraction of people born on one day out of four years, or 1/[(365 x 4 ) + 1] = 1/1,461 = 0.068% (less than one-tenth of a percent of the population).
Thirty days hath September, April, June, and November, All the rest have thirty-one, Excepting February alone, And it has twenty-eight days time, But in leap years, February has twenty-nine.
Calendar Rhyme (Two versions)
Thirty days hath September, April, June, and November, All the rest have thirty-one, Excepting February alone, And that has twenty-eight days clear, And twenty-nine in each leap-year.
The vernal equinox occurs in late March (this is the beginning of spring in the Northern Hemisphere and the beginning of fall in the Southern Hemisphere); the autumnal equinox occurs in late September (this is the beginning of fall in the Northern Hemisphere and the beginning of spring in the Southern Hemisphere). What is a Leap Year? A leap year is a year that has one extra day in it. A leap year occurs roughly every four years. Most years have 365 days, but a leap year has 366 days. The extra day is added onto the end of the shortest month, February; in a leap year, February has 29 days (instead of its usual 28 days). February 29 is called leap day.
Why Do We Have Leap Years? A year is defined as the time it takes for the Earth to orbit around the sun once. It takes the Earth about 365 1/4 days to make one entire orbit around the sun (a day is one rotation around the Earth's axis). By adding one extra day about every four years, the Earth is in the same point of its orbit at the same time of the calendar year each year. Before a leap-year calendar was used, the seasons drifted around the calendar (the drift is about 1/4 day or 6 hours each year). For example, over three hundred years, July would go from summer to spring. Our current calendar is called the Gregorian calendar; this calendar was devised by Aloysius Lilius (an Italian physician) and named for Pope Gregory who decreed in 1582 that it be used in Catholic areas. This calendar wasn't adopted in Britain and the American Colonies until 1752. What Years are Leap Years? Usually, there is a leap year every four years -- but once in a long while, a leap year has to be skipped (this is because the Earth's orbit is 365.242 days, a bit less than 365 1/4). To determine if the year is a leap year: •
•
Non-century years (a century year is a year ending in 00) are leap years if they are divisible by four. For example, 2004, 2008 and 2012 are leap years; 2009, 2010 and 2011 are not. Century years are leap years if they are divisible by 400. For example, 1600, 2000, and 2400 are leap years; 1700, 1800, 1900, 2100, 2200, and 2300 are not.
A List of Some Leap Years A list of some leap years: ...1984, 1988, 1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020, 2024, 2028, 2032, 2036, 2040, 2044, 2048, 2052, 2056, 2060, 2064, 2068, 2072, 2076, 2080, 2084, 2088, 2092, 2096, 2104, 2108, 2112, 2116, 2120, ... Leap Day Birthdays People born on leap day (February 29) can celebrate their birthday on March 1 (or February 28) on non-leap years. A person born on a leap day is sometimes called a leapling. What percentage of the population is born on leap day? Assuming an equal distribution of birthdays throughout the year, the fraction of people born on
leap day is the fraction of people born on one day out of four years, or 1/[(365 x 4 ) + 1] = 1/1,461 = 0.068% (less than one-tenth of a percent of the population).
Thirty days hath September, April, June, and November, All the rest have thirty-one, Excepting February alone, And it has twenty-eight days time, But in leap years, February has twenty-nine.
Calendar Rhyme (Two versions)
Thirty days hath September, April, June, and November, All the rest have thirty-one, Excepting February alone, And that has twenty-eight days clear, And twenty-nine in each leap-year.
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