On September 22, at 4:02 p.m. ET, the Sun will shine directly over the equator—the midpoint of the Earth. The whole world will thus experience a day and night of equal length. In the Northern Hemisphere, we call this the autumn equinox. It marks the first day of fall. Around the world, people are marking the day with ceremonies, some of them ancient (and some less so).
You might be wondering two things: 1. Why on almost every other day of the year (the vernal equinox being the other exception) do different parts of the world have days and nights of differing length? 2. What do they call the day in the Southern Hemisphere?
A DAY AT THE BEACH
The answer to each of these questions resides in the Earth's axial tilt. The easiest way to imagine that tilt is to think about tanning on the beach. (Stay with me here.) If you lay on your stomach, your back gets blasted by the Sun. You don't wait 30 minutes then flop over and call it a day. Rather, as you tan, every once in a while, you shift positions a little. Maybe you lay a bit more on one side. Maybe you lift a shoulder, move a leg a little. Why? Because you want the Sun to shine directly on a different part of you. You want an even tan.
It might seem a little silly when you think about it. The Sun is a giant fusion reactor 93 million miles away. Solar radiation is hitting your entire back and arms and legs and so on whether or not you adjust your shoulder just so. But you adjust, and it really does improve your tan, and you know this instinctively.
The Earth works a lot like that, except it's operating by physics, not instinct. If there were no tilt, only one line of latitude would ever receive the most direct blast of sunlight: the equator. As the Earth revolved around the Sun, the planet would be bathed in sunlight, but it would only be the equator that would always get the most direct hit (and the darkest tan). But the Earth does have a tilt. Shove a pole through the planet with one end sticking out the North Pole and one end sticking out the South, and angle the whole thing by 23.5 degrees. That's the grade of Earth's tilt.
Now spin our little skewered Earth and place it in orbit around the Sun. At various points in the orbit, the Sun will shine directly on different latitudes. It will shine directly on the equator twice in a complete orbit—the fall and spring equinoxes—and at various points in the year, the most direct blast of sunlight will slide up or down. The highest latitude receiving direct sunlight is called the Tropic of Cancer. The lowest point is the Tropic of Capricorn. The poles, you will note, are snow white. They have, if you will, a terrible tan—and that's because they never receive solar radiation from a directly overhead Sun (even during the long polar summer, when the Sun never sinks below the horizon).
WHEN DO THE SEASONS CHANGE?
The seasons have nothing to do with the Earth's distance from the Sun. Axial tilt is the reason for the seasons. The Sun is directly over the Tropic of Cancer (66.5 degrees latitude in the Northern Hemisphere) on June 21 or 22. When that occurs, the Northern Hemisphere is in the summer solstice. The days grow long and hot. As the year elapses, the days slowly get shorter and cooler as summer gives way to autumn. On September 21 or 22, the Sun's direct light has reached the equator. Days and night reach parity, and because the Sun is hitting the whole world head-on, every latitude experiences this simultaneously.
On December 21 or 22, the Sun is directly over the Tropic of Capricorn in the Southern Hemisphere, meaning the Northern Hemisphere is receiving the least sunlight it will get all year. The Northern Hemisphere is therefore in winter solstice. Our days are short and nights are long. Parity will again be reached on March 21 or 22, the vernal equinox for the Northern Hemisphere, and the whole process will repeat itself.
And welcome to fall, Northern Hemisphere! Enjoy this long day of sunlight, because dark days are ahead. You'll get less and less light until the winter solstice, and the days will grow colder. Take solace, though, in knowing that the whole world is experiencing the very same thing. Now it's the Southern Hemisphere's turn to get ready to spend some time at the beach.
The first Rosh Hashanah supposedly occurred in the Garden of Eden. But what does this important Jewish holiday involve today?
1. IT LITERALLY TRANSLATES AS "HEAD OF THE YEAR."
Rosh Hashanah, the Jewish New Year, can fall any time between the fifth of September and the fifth of October on the Gregorian Calendar. On the Jewish calendar, it is the first day of the month of Tishrei and marks the start of the High Holy Days. These days are also known as the days of awe, ushering in the final phase of atonement. The holiday celebrates the anniversary of the creation of the world.
2. FOR THE MONTH BEFORE, JEWS ASK FOR FORGIVENESS FROM FRIENDS AND FAMILY.
In order to have a clean slate going into the New Year, Jews ask for forgiveness from those close to them. The idea here is that God cannot forgive transgressions against people until those wronged have forgiven.
3. TRADITIONALLY, ROSH HASHANAH HAPPENS OVER TWO DAYS.
These days are combined into the yoma arichta, or "long day." At sunset on the first evening, candles are lit by the lady of the house. Then blessings are recited: a traditional holiday blessing over the candles, followed by the shehecheyanu, a thanksgiving prayer for special occasions. Both evenings also feature a festive meal.
4. UNLIKE DECEMBER 31, THE JEWISH NEW YEAR IS A TIME OF SERIOUS REFLECTION AND REPENTANCE.
Even Jews who go to synagogue at no other time of year will often go on the high holidays, which include Rosh Hashanah and Yom Kippur. Religious poems called piyyutim are recited and a special high holy day prayer book called the machzor is used. The service is often longer than Sabbath services, and centers around the theme of God’s sovereignty, remembrance, and blasts of the shofar (see below).
5. DESPITE NOT BEING A HUGE PARTY, JEWS ARE EXPECTED TO ENJOY THE YOM TOV, OR HOLIDAY.
People often get fresh haircuts and new clothes in order to celebrate. The tradition is to wear white clothing as a sign of purity and renewal. Some avoid wearing red, since it's the color of blood.
6. ACCORDING TO THE TALMUD, ON ROSH HASHANAH, GOD INSCRIBES EVERYONE'S NAMES INTO ONE OF THREE BOOKS.
The metaphorical understanding is that good people go into the Book of Life, and evil ones into the Book of Death; those who are in the middle are put in an intermediate one and have judgment put off until Yom Kippur. Since virtually no one is all good or all evil, you're supposed to assume you fall somewhere in the middle, and in order to be inscribed in the Book of Life for the coming year, it is important to do everything possible to atone before Yom Kippur.
7. THE SOUNDING OF THE SHOFAR IS THE MOST ICONIC IMAGE OF THIS HOLIDAY.
The shofar is a ram’s horn that is curved and bent. It is hollowed out and blown during religious ceremonies to make three different sounds. Hearing it is meant to call you to repent.
8. WHILE SOME JEWISH HOLIDAYS INVOLVE FASTING, ROSH HASHANAH INVOLVES A FEAST.
It is traditional to eat apples dipped in honey to represent having a sweet year ahead. A round challah bread symbolizes the cycle of the year (another interpretation is that it represents a crown and thus God’s sovereignty). Sometimes a fish, or just its head, is included, possibly to represent that as fish cannot survive without water, Jews cannot survive without the Torah. Pomegranates contain many seeds, which have long been associated with the commandments that Jews follow, so by eating them they remind themselves to be good in the coming year. Other common foods include dates, leeks, gourds, and black-eyed peas, all of which are mentioned in the Talmud as foods to eat on New Year’s.
9. SOME BRANCHES OF JUDAISM PARTICIPATE IN THE RITUAL OF TASHLIKH, OR "CASTING OFF."
The ritual involves standing near water, like a river, and reciting prayers. Then participants symbolically cast away their sins by throwing bread crumbs or stones into the water. This is supposedly derived from the Biblical passage “You will cast all their sins into the depths of the sea” (Micah 7:19), although most Jewish sources trace it back to 15th century Germany. In New York City, large groups gather on the Brooklyn Bridge, while in Israel—where there is much less open water—people might use something as small as a fish pond.
10. THERE ARE VARIOUS TRADITIONAL GREETINGS FOR ROSH HASHANAH.
L'Shana Tova Tea-ka-tayvu is Hebrew for “May you be inscribed for a good year,” referring to that person’s name being put in the Book of Life. This is often shortened to Shana Tova, which just means “Good Year.” This isn’t to be confused with wishing each other a “Happy New Year.” Happy implies a level of superficiality, while the Jewish wish for a good year hopes the person will achieve their purpose.
11. THE HAVDALAH PRAYER IS PERFORMED AS NIGHT FALLS ON THE SECOND AND LAST DAY.
It involves saying blessings over a full cup of kosher wine or grape juice, although other drinks can be used in a pinch. After this, Rosh Hashanah is over.