The vernal equinox is upon us: On Wednesday, March 20, both the Northern and Southern hemispheres will experience an equal amount of daylight. For those of us in the Northern Hemisphere, it marks the beginning of spring, with daylight hours continuing to lengthen until the summer solstice in June. For those south of the equator, it’s the beginning of autumn.
Technically speaking, the equinox occurs when the sun is directly in line with the equator. This will happen at 5:58 pm Eastern time on Wednesday. (A few hours later, at 9:43 pm, you can look out for the “supermoon”, the last one until 2020.)
Below is a short scientific guide to the most equal night of the year.
1) Why do we have an equinox?
The equinox, the seasons, and the changing length of daylight hours throughout the year are all due to one fact: The Earth spins on a tilted axis.
The tilt — possibly caused by a massive object hitting Earth billions of years ago — means that for half the year, the North Pole is pointed toward the sun (as in the picture below). For the other half of the year, the South Pole gets more light. It’s what gives us seasons.
Here’s a time-lapse demonstration of the phenomenon shot over the course of a whole year from space. In the video, you can see how the line separating day from night swings back and forth from the poles during the year.
And here’s yet another cool way to visualize the seasons. In 2013, a resident of Alberta, Canada, took this pinhole camera photograph of the sun’s path throughout the year and shared it with the astronomy website EarthSky. You can see the dramatic change in the arc of the sun from December to June.
This is a 6 month pinhole photo taken from solstice to solstice, in Medicine Hat, Alberta, Canada. We are one of the sunniest cities in Canada, and this shows it nicely.
Posted by Ian Hennes on Saturday, December 21, 2013
(You can easily make a similar image at home. All you need is a can, photo paper, some tape, and a pin. Instructions here.)
2) How many hours of daylight will I get Wednesday?
Equinox literally means “equal night.” And during the equinox, most places on Earth will see approximately 12 hours of daylight and 12 hours of night.
But not every place will experience the exact same amount of daylight. For instance, on Wednesday, Fairbanks, Alaska, will see 12 hours and 15 minutes of daylight. Key West, Florida, will see 12 hours and six minutes. The differences are due to how the sunlight gets refracted (bent) as it enters Earth’s atmosphere at different latitudes.
That daylight is longer than 12 hours on the equinox is also due to how we commonly measure the length of a day: from the first hint of the sun peeking over the horizon in the morning to the very last glimpse of it before it falls below the horizon in the evening. Because the sun takes some time to rise and set, it adds some extra daylight minutes.
Check out TimeAndDate.com to see how many hours of sunlight you’ll get during the equinox.
3) Over the course of the entire year, does every spot on Earth get an equal number of daylight hours?
In the summer months, the northernmost latitudes get a lot of daylight. Above the Arctic Circle, during the summer, there’s 24 hours of daylight. In the winter, the Arctic Circle is plunged into constant darkness.
So does this mean the number of daylight hours — in total, over the course of the year — equal out to places where the seasonal difference is less extreme?
The answer to this question is somewhat surprising: Roughly speaking, everywhere on Earth sees a similar number of daylight hours every year. But the equator actually gets slightly fewer daylight hours than the poles.
As astronomer Tony Flanders explained for Sky & Telescope magazine, sunlight at the poles gets refracted more than sunlight at the equator. That refracting results in the visible disc of the sun being slightly stretched out (think of when the full moon is near the horizon and looks huge — it’s being refracted too). And the refracted, stretched-out sun takes slightly longer to rise and set. Flanders estimated that the equator spends around 50.5 percent of its year in sunlight, while the poles spend between 51.5 and 53 percent of their years in sunlight.
And, of course, this is how much sunlight these areas could potentially receive if the weather were always perfectly clear; it’s not how much sunlight they actually see, nor the strength of the sunlight that hits their ground. “Where are the places on Earth that receive the largest amount of solar radiation?” is a slightly different question, the answer to which can be seen on the chart below.
4) Can I really only balance an egg on its tip during on the equinox?
Perhaps you were told as a child that on the equinox, it’s easier to balance an egg vertically on a flat surface than on other days of the year.
The practice originated in China as a tradition on the first day of spring in the Chinese lunar calendar in early February. According to the South China Morning Post, “The theory goes that at this time of year the moon and earth are in exactly the right alignment, the celestial bodies generating the perfect balance of forces needed to make it possible.”
This is a myth. The amount of sunlight we get during the day has no power over the gravitational pull of the Earth or our abilities to balance things upon it. You can balance an egg on its end any day of the year (if you’re good at balancing things).
5) Is there an ancient monument that does something cool during the equinox?
During the winter and summer solstices, crowds flock to Stonehenge in the United Kingdom. During the solstices, the sun either rises or sets in line with the layout of the 5,000-year-old-monument. And while some visit Stonehenge for the spring equinox too, the real place to be is in Mexico.
That’s because on the equinox, the pyramid at Chichen Itza on the Yucatan Peninsula puts on a wondrous show. Built by the Mayans around 1,000 years ago, the pyramid is designed to cast a shadow on the equinox outlining the body of Kukulkan, a feathered snake god. A serpent-head statue is located at the bottom of the pyramid, and as the sun sets on the day of the equinox, the sunlight and shadow show the body of the serpent joining with the head.
This is easier to see in a video. Check it out below.
6) Are there equinoxes on other planets?
Yes! All the planets in the solar system rotate on a tilted axis and therefore have seasons. Some of these tilts are minor (like Mercury, which is tilted at 2.11 degrees). But others are more like the Earth (tilted at 23.5 degrees) or are even more extreme (Uranus is tilted 98 degrees!).
Below, see a beautiful composite image of Saturn on its equinox captured by the Cassini spacecraft (RIP) in 2009. The gas giant is tilted 27 degrees relative to the sun, and equinoxes on the planet are less frequent than on Earth. Saturn only sees an equinox about once every 15 years (because it takes Saturn 29 years to complete one orbit around the sun).
During Saturn’s equinox, its rings become unusually dark. That’s because these rings are only around 30 feet thick. And when light hits them head on, there’s not much surface area to reflect.
7) I clicked this article accidentally and really just want a mind-blowing picture of the sun
The image above was taken by NASA’s Solar Dynamics Observatory, a spacecraft launched in 2010 to better understand the sun.
This past summer, NASA launched the Parker Solar Probe, a spacecraft that will come within 4 million miles of the surface of the sun (much closer than any spacecraft has been before). The goal is to study the sun’s atmosphere, weather, and magnetism and figure out the mystery of why the sun’s corona (its atmosphere) is much hotter than its surface. Still, even several million miles away, the probe will have to withstand temperatures of 2,500 degrees Fahrenheit.
It’s essential to understand the sun: It’s nothing to mess with. Brad Plumer wrote for Vox about what happens when the sun erupts and sends space weather our way to wreak havoc on Earth.
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Whales dying from plastic bags: The alarming trend, explained
Another dead whale has washed ashore with a belly full of plastic.
This week, the carcass of the young sperm whale, estimated to have been 7 years old, was found on a beach in Cefalù, Italy. Investigators aren’t certain whether the plastic killed the whale. But it’s part of a gruesome pattern that’s become impossible to ignore.
In April, a pregnant sperm whale washed up on a beach in Sardinia with nearly 50 pounds’ worth of plastic bags, containers, and tubing in her stomach. Biologists in Florida last month euthanized a baby rough-toothed dolphin with two plastic bags and a shredded balloon in its stomach.
“The dolphin was very young and emaciated,” said Michelle Kerr, a spokesperson for the Florida Fish and Wildlife Conservation Commission, in an email. “Due to a poor prognosis, the decision was made to humanely euthanize the animal on scene.”
In March, a 1,100-pound Cuvier’s beaked whale was recovered in the Philippines filled with 88 pounds of plastic bags, fishing line, and rice sacks. A beached sperm whale was found in Indonesia last year with more than 1,000 pieces of plastic inside.
As the quantity of plastic humans dump in the ocean has reached obscene proportions, we’re seeing more and more sea life — including birds, otters, sea turtles, and fish — choking on it.
But the impact on whales is particularly alarming. After centuries of whaling and overfishing, the survival of many whale species is already precarious. Now, just as their numbers are starting to recover, whales are consuming our toxic waste. And their deaths aren’t just about biodiversity loss: Whales play a critical role in marine ecosystems, which provide 3 billion people with their primary sources of protein.
To find out more about why whales are so vulnerable to plastic waste, I talked to Lars Bejder, director of the Marine Mammal Research Program at the University of Hawaii Manoa. He said there are multiple mechanisms at work here and that dying isn’t the only plastic hazard for whales, and explained why the problem will only get worse.
There’s a gargantuan amount of plastic in the ocean
The root cause of these stranded, plastic-filled whales is that plastic is cheap and easy to produce but almost impossible for nature to destroy. Chunks of plastic linger for decades, breaking down into smaller and smaller pieces. This waste then churns in the ocean in massive gyres.
Roughly 8 million metric tons of plastic — a mass greater than that of the Great Pyramid of Giza — enters the ocean each year.
Meanwhile, we’re still trying to figure out how much plastic waste has already accumulated in the ocean. A study published this week in the journal Scientific Reports estimated that 414 million bits of garbage weighing 238 tons have been deposited on the Cocos (Keeling) Islands 1,300 miles off the coast of Australia. It’s a sign that even the most remote regions of the world are now contaminated with the detritus of civilization.
“Sadly, the situation on the Cocos (Keeling) Islands is not unique, with significant quantities of debris documented on islands and coastal areas from the Arctic to the Antarctic,” researchers wrote. “[G]lobal debris surveys, the majority of which are focused solely on surface debris, have drastically underestimated the scale of debris accumulation.”
And the amount of plastic waste in the ocean is surging. Our current trajectory puts us on track to have more plastic in the ocean than fish by weight by 2050, according to the World Economic Forum.
So for the largest, hungriest animals in the ocean, plastic is becoming an unwelcome part of their diets.
Different whales face different risks from plastic
Whales are among the more intelligent creatures in the ocean, so why aren’t they smart enough to avoid eating plastic?
Well, one reason is that often plastic is in their food.
Small crustaceans like krill and tiny fish like anchovies often end up inadvertently consuming microplastics. Whales, the largest animals ever known to have existed, have a voracious appetite for these critters. A blue whale eats between 2 and 4 tons of krill per day.
Whales like the blue whale have baleen plates in their mouths that act as filters, trapping their small prey as well as small bits of plastic. This means they are less likely to ingest larger plastic waste items like bottles and containers, but the small plastic bits they consume quickly pile up.
“These baleen whales filter hundreds of thousands of cubic meters of water per day,” Bejder said. “You can imagine all these microplastics they encounter through this filtration process that then become bioaccumulated.”
Microplastics are unlikely to obstruct the digestive tract of a baleen whale, but as they build up inside an animal’s tissues, they can leach toxic chemicals like endocrine disruptors that make the creature sick. This problem can affect all ocean filter feeders, including manta rays and whale sharks.
That means there could be large whales dying of plastic poisoning without obvious culprits like flip-flops and food containers in their stomachs, according to Bejder.
A study published this week in Royal Society Open Science also reported that plastic pollution is more dangerous to baleen whales than oil spills. “Particle capture studies suggest potentially greater danger to [baleen whales] from plastic pollution than oil,” the authors wrote.
Toothed whales like sperm whales and dolphins normally catch bigger prey, like squid. But since they can swallow larger animals, they are vulnerable to larger chunks of plastic, like bags and nets.
“They might be seeking those out because they’re thinking they might be prey,” Bejder said. A plastic container in murky waters could resemble a fish to a toothed whale, or a sperm whale may inadvertently swallow plastic garbage as it hunts for a meal.
Once ingested, the plastic piles up in the whale’s stomach. It can then obstruct bowels, preventing whales from digesting food and leading them to starve to death. It can also give a whale a false sense of being full, leading the whale to eat less and get weaker. That leaves it vulnerable to predators and disease.
We’re only seeing a tiny fraction of the whales being harmed by plastic
Part of the reason we pay so much attention to whales killed by plastic is because the whales themselves are very big and the plastic culprits are startlingly obvious. Large animals decay slowly, giving people plenty of time to figure out the cause of death, whereas smaller fish and crustaceans dying from plastic decompose quickly and are rarely investigated. Even for casual observers, a dead whale blocking a beach vacation photo is pretty hard to ignore.
Still, we’re missing a big part of the picture.
“The ones that land on the beach that are killed through ingestion, they’re just the tip of the iceberg. They’re just the ones that we see,” Bejder said. “I’m sure that many, many marine mammals have some levels of plastic bags and plastic items in their stomachs.”
Many more whales could be dying from plastic poisoning without our knowledge. Around the Gulf of Mexico for example, 2 to 6 percent of whale carcasses end up on a shoreline. That means the vast majority sink to the ocean floor. This is likely the case for most of the world’s waters.
And the fact that whales are suffering shows that our marine ecosystems in general are in peril. “Whales, baleen whales, these larger dolphins species are pretty much at the top of the food chain,” Bejder said. “They are sentinels of ocean health for sure.”
But with more plastic waste pouring into the ocean, the prognosis for the most mega of megafauna is grim.
Yoga With ELLE: When You’re Low On Energy
Join Fern Ross, our Chief Sub-Editor / Production Editor and resident (ahem, registered) yoga teacher as she takes you through several yoga poses each tailored to specific needs. This week, yoga for when you’re low on energy aka yoga for when you’re on your period.
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