Autumn Equinox: The Science Behind the First Day of Fall

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On September 22, the Sun will shine directly over the equator—the midpoint of the Earth. (For 2018, this moment will happen at 9:54 p.m. ET.) 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.

People light candles during the autumn equinox celebration at Neris River waterfront in Vilnius, Lithuania after sunset on September 21, 2013.
People light candles during the autumn equinox celebration at Neris River waterfront in Vilnius, Lithuania after sunset on September 21, 2013.
PETRAS MALUKAS, AFP/Getty Images

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?

A Maya priestess conducts an autumn equinox ceremony at El Salvador's Cihuatan Archeological Park.
A Maya priestess conducts an autumn equinox ceremony at El Salvador's Cihuatan Archeological Park.
Jose CABEZAS, AFP/Getty Images

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.

Members of The Druid Order of London conduct a ceremony on Primrose Hill to celebrate the Autumn Equinox on September 22, 2008 in London, England.
Members of The Druid Order of London conduct a ceremony on Primrose Hill to celebrate the Autumn Equinox on September 22, 2008 in London, England. The Druid Order of London, which was founded in Oxford in 1245, has been conducting the Autumn Equinox ceremony on Primrose Hill since 1717.
Matt Cardy, Getty Images

Now reverse all of this for the Southern Hemisphere. When we're at autumnal equinox, they're at vernal equinox. Happy first day of spring, Southern Hemisphere!

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.

This story first ran in 2016.

15 Scientific Ways to Relax for National Relaxation Day

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iStock/anyaberkut via Getty Images

Today is National Relaxation Day, so you have a great excuse to take it easy. Here’s how science can help you have the most laid-back day of the year.

1. Get a house or office plant.

Spending time in nature improves your overall wellbeing, but it turns out even just a little greenery is great for your health. Studies have shown patients in hospital rooms with plants report lower stress. Even just stepping into a lush space can reduce your heart rate. Plus, plants are effective at increasing oxygen and clearing out toxins, which should help you breathe easier—literally.

2. Avoid screens before bedtime.

Artificial light from TV and computer screens affects melatonin production and throws off circadian rhythms, which messes with your sleep. Studies have found that young adults were more likely to suffer from sleep disorders, high stress and even depression if they reported intensive use of cell phones and computers at night.

3. Eat a banana.

Potassium helps your body regulate blood pressure. Keeping that under control should help you bounce back more quickly from what’s got you stressed.

4. Indulge in some citrus.

Still hungry after that chocolate and banana? Try citrus. Recent studies show that vitamin C helps to alleviate the physical and psychological effects of stress.

5. Listen to classical music.

Portrait of a beautiful young woman lying on sofa with headphones on and closed eyes, relaxing
BartekSzewczyk/iStock via Getty Images

Any music you enjoy is bound to make you feel better, but classical music, in particular, has been shown to slow heart rate, lower blood pressure and even decrease levels of stress hormones.

6. Drink green tea sweetened with honey.

Green tea contains L-theanine, which reduces stress, and honey—unlike cane sugar—has been shown to counteract free radicals and reduce inflammation, which is sometimes linked to depression.

7. Give yourself a hand massage.

Especially if you spend all day typing, hands can get really tense. A quick massage should be doable at your desk and if you incorporate some lavender-scented lotion, you’ll get extra relaxation benefits.

8. Lock lips with someone.

Romance is relaxing! Kissing releases oxytocin, a chemical that is shown to reduce levels of the stress hormone cortisol.

9. Chew some gum.

No matter what flavor it is, the act of chewing gum has been proven to lower cortisol and improve reported mood.

10. Blow up a balloon.

Young woman blowing up a blue balloon against a yellow background
Deagreez/iStock via Getty Images

Reacting to stress with short, shallow breaths will only exacerbate the problem—your body needs more oxygen, not less, to relax. Blowing up a balloon will help you refocus on your breathing. No balloons around? Just concentrate on taking a few deep breaths.

11. Mow the lawn.

Research shows that a chemical released by a mowed lawn—that fresh-cut grass smell—makes people feel happy and relaxed. Plus, knocking it off your to-do list will give you one less thing to stress about.

12. Find something to make you laugh.

Watching a funny video online does more than just brighten your afternoon, it physically helps to relax you by increasing the endorphins released by your brain.

13. Grab some chocolate.

What’s also good at releasing endorphins? Chocolate. Studies show that even just 40 grams of dark chocolate a day can help you de-stress.

14. Focus on relaxing all of your muscles.

Take a break from whatever you’re doing and, starting at your toes and working upwards, spend a few moments slowly tensing, and then releasing, the muscles of each part of your body.

15. Take a mental vacation.

Man takes a break from work to meditate at his laptop
AaronAmat/iStock via Getty Images

If you’re feeling overwhelmed at work, take a moment to close your eyes and picture a particularly relaxing scene. It may sound cheesy, but numerous studies show that just a few minutes of disengaging from your stressors rejuvenates your ability to tackle the work.

5 Fascinating Facts About Middle Children

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francisgonsa/iStock via Getty Images

Full House's perpetually neglected Stephanie Tanner, The Brady Bunch's embittered Jan Brady, Downton Abbey's tragedy-prone Lady Edith Crawley: For many people, these are the images that pop into their heads when thinking of the stereotypical middle child. In TV shows and movies, they’re often used as comic relief, always stuck in the shadow of their other, seemingly more important siblings. But the reality is far more generous to middle children.

Studies have shown that middle children are exceedingly independent and creative, with certain leadership qualities that their firstborn and last-born counterparts can’t match. Some of our most important world leaders, artists, musicians, and entrepreneurs occupy this oft-mocked middle spot, but from most accounts, it’s a breeding ground for success. Here are five fascinating facts about middle children.

1. Middle children may be endangered.

There was a time during the first half of the 20th century when having three to four children was seen as the ideal number for parents, with 35 percent of moms between 40 and 44 having four children or more. Those numbers have been reversing for several decades—and now, the average American family consists of 3.14 people. On top of that, only 12 percent of women in their early forties have four children or more.

More people are going to college, taking longer to become financially settled, have easier access to birth control, and are embarking on demanding careers that put family life on the back burner. In addition to having children later in life, the average cost of raising a child has increased dramatically over the generations, so one or two kids might be all some couples can afford. These factors all add up to create smaller families, which means we’ll likely see fewer middle children throughout the country in future decades if these trends continue. And without them, we’ll lose out on all of the remarkable traits seen below.

2. Middle children can have first-rate negotiation skills.

Despite the common perception of middle children being resentful of their siblings and never getting enough attention from their parents, Katrin Schumann, co-author of The Secret Power of Middle Children, has done extensive research on the subject that found the plight of middle children may actually be a positive thing later in life. One such trait is their ability to negotiate.

“Middles are used to not getting their own way, and so they become savvy, skillful manipulators,” Schumann told Psychology Today. “They can see all sides of a question and are empathetic and judge reactions well. They are more willing to compromise, and so they can argue successfully. Since they often have to wait around as kids, they’re more patient.”

3. Their low self-esteem might not necessarily be a bad thing.

Yes, the middle child may suffer from low self-esteem when compared to their siblings, due to their “their lack of uniqueness and attention at home,” according to Schumann. However, this doesn’t have to be a negative thing as it helps keep their ego in check.

“Also, self-esteem is not as critical as our society believes,” Schumann explained. “Having an accurate sense of your self-esteem is more important than having high self-esteem. Surprisingly, new studies show that high self-esteem does not correlate with better grades in school or greater success in life. It can actually lead to a lack of perseverance in the face of difficulties.”

4. Middle children tend to be faithful in their relationships.

Dr. Catherine Salmon, Schumann's co-author on The Secret Power of Middle Children, found that 80 percent of middle children claimed they have never cheated on their partner. This is compared to 65 percent of firstborns and 53 percent of last-borns who said they were never unfaithful to their long-term partner or spouse. This, of course, led to separate studies confirming that middle children, and their spouses, were happiest in marriage when compared to other birth orders.

There is a catch, however: Schumann said that while middle children may be the happiest and make for satisfied partners, two middle children might not make an ideal match: "An Israeli marital happiness survey shows that middles are the happiest and most satisfied in relationships, and that they partner well with firsts or lasts—but less well with other middles, because they may both avoid conflict."

5. Some of history's most important leaders were middle children.

Though the conventional numbers have established that most U.S. presidents are firstborns, Schumann contends that half of our Commanders-in-Chief are actually middle children. In an interview with NPR, she revealed that the connection between the presidency and middle children was obscured for years because of one strange quirk: firstborn girls weren’t traditionally counted as older siblings. Instead, firstborns were only taken into consideration when it came to males.

In general, it's difficult to nail down certain presidential birth orders, as the middle child blog SmackDab puts it: "George Washington’s father had four children with his first wife before the first President was born. Washington was the first of six children from his father’s second marriage. So was he the first born or the fifth born?" Still, if we're to take conventional wisdom and a loose definition of what a middle child is (basically anyone not the oldest or the youngest), then it turns out that 52 percent of presidents were born in the middle, including Thomas Jefferson, Teddy Roosevelt, John F. Kennedy, and Abraham Lincoln.

It's JFK in particular, Schumann concluded, who displayed many of the traits typical of a middle child during his years in office, citing his ability to communicate and negotiate even under the most stressful of conditions.

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