Siberian Hamster Testicles are Growing, Which Means the Vernal Equinox is Here

Standing before the Pyramid of the Sun in Teotihuacan, Mexico, a woman embraces spring on the vernal equinox. Image Credit: Ronaldo Schemidt/AFP/Getty Images

Today you, I, and everyone in the world have something in common. Regardless of whether you live in Australia or Austria or Austin, day and night are approximately the same length the whole world over. Today is the vernal equinox—the first day of spring. If you live in the Northern Hemisphere, your days will be getting longer, your trees greener, and your animals friskier. We think it all happens because billions of years ago, a proto-planet collided with an embryonic Earth. Here's what's going on.


Winter and summer have nothing to do with the distance of the Earth from the Sun. Rather, seasons are the product of axial tilt and orbital dynamics. The Earth is tilted slightly at 23.5 degrees relative to its orbital plane. (That tilt is thought related to the aforementioned collision.) The orientation of the tilt never changes, and as Earth revolves around the Sun over the course of a year, different latitudes are thus in direct sunlight. When the Northern Hemisphere is in direct sun, it is summertime there and wintertime down under, and vice versa when the Southern Hemisphere is in direct sunlight.

If this is hard to visualize, take your cell phone and hold it upright next to the left side of your computer screen, tilted slightly toward the computer. The top-right corner should be closest to the screen. It is summertime in that corner (the screen being the Sun in this demonstration). Now keep everything the same, but bring your phone to the right side of your screen. Now the bottom-left of your phone is closer. It is summertime there. If your phone were a spinning sphere, those two corners would be the Tropics of Cancer and Capricorn, respectively. Over a full orbit of the Earth around the Sun, this means the center of the Earth—the Equator—is in direct sunlight twice.

Today is one of those times, marking the transition from winter to spring in the Northern Hemisphere. (The other, autumnal equinox, transitions fall to winter.)


Humans today have it pretty easy. We have coats and fires during the winter, and shorts, air conditioning, and Disney vacations in the summer. For many in the developed world, seasons are in some ways a neat way of marking time, but they don’t necessarily dictate the course of our lives. For plants and animals, though, the seasons are serious business. The availability of food and warmth are vital for reproduction and rearing young animals. During the fall and short winter days, for example, the testicles of Siberian hamsters change dramatically in size (and under no circumstances should you google that). That’s a pretty granular-level effect of the axial tilt of an entire planet.

The same goes for birds flying south for the winter. Studies suggest that the migration is in large measure simply birds following the food. (Starvation winters in the north can be summer feasts in the south. Go where the worms are.) There is some evidence that the migratory patterns are also wired into the DNA of some birds. We’ve discussed this previously at mental_floss:

Captive birds have been observed getting pretty fidgety and changing their sleep patterns right before their natural migration time. Ethologists—those who study animal behavior—call the birds' behavior zugunruhe ("migratory restlessness"). Captive birds display zugunruhe even if they're not exposed to natural light or to seasonal temperature changes.

It goes far beyond that, though. Even plants know what’s up. “Spring is sooner recognized by plants than by men,” says the Chinese proverb. Plants produce phytochromes, which are compounds sensitive to the light spectrum and used to regulate flowering and budding. In some regions, the vernal equinox and the longer days of direct sunlight it brings lead to an increased production of red phytochromes. (In the winter, the Sun’s position in the sky, and the sunlight often shining indirectly, leads to the increased production of far-red phytochromes.) As the ratios shift, you get flowering. No tilt, no bouquets.

So while today is an interesting day to mark for social reasons—a rare point of global harmony and equality imposed by the natural world, even if only concerning light and dark—it’s also a day marking a shift in the behaviors of the natural world itself. Today we are all equal, and for the next few months, the Northern Hemisphere begins anew.

Photo Illustration by Mental Floss. Curie: Hulton Archive, Getty Images. Background: iStock
10 Radiant Facts About Marie Curie
Photo Illustration by Mental Floss. Curie: Hulton Archive, Getty Images. Background: iStock
Photo Illustration by Mental Floss. Curie: Hulton Archive, Getty Images. Background: iStock

Born Maria Salomea Skłodowska in Poland in 1867, Marie Curie grew up to become one of the most noteworthy scientists of all time. Her long list of accolades is proof of her far-reaching influence, but not every stride she made in the fields of chemistry, physics, and medicine was recognized with an award. Here are some facts you might not know about the iconic researcher.


Maria Skłodowska was the fifth and youngest child of two Polish educators. Her parents placed a high value on learning and insisted all their children—even their daughters—receive a quality education at home and at school. Maria received extra science training from her father, and when she graduated from high school at age 15, she was first in her class.


After collecting her high school diploma, Maria had hoped to study at the University of Warsaw with her sister, Bronia. Because the school didn't accept women, the siblings instead enrolled at the Flying University, a Polish college that welcomed female students. It was still illegal for women to receive higher education at the time so the institution was constantly changing locations to avoid detection from authorities. In 1891 she moved to Paris to live with her sister, where she enrolled at the Sorbonne to continue her education.


Marie Curie and her husband, Pierre Curie, in 1902.
Marie Curie and her husband, Pierre Curie, in 1902.
Agence France Presse, Getty Images

In 1903, Marie Curie made history when she won the Nobel Prize in physics with her husband, Pierre, and with physicist Henri Becquerel for their work on radioactivity, making her the first woman to receive the honor. The second Nobel Prize she took home in 1911 was even more historic. With that win in the chemistry category, she became the first person of any gender to win the award twice. She remains the only person to ever receive Nobel Prizes for two different sciences.


The second Nobel Prize she received recognized her discovery and research of two elements: radium and polonium. The former element was named for the Latin word for "ray" and the latter was a nod to her home country, Poland.


Marie Curie's daughter Irène Joliot-Curie, and her husband, Frédéric Joliot-Curie, circa 1940.
Marie Curie's daughter Irène Joliot-Curie, and her husband, Frédéric Joliot-Curie, circa 1940.
Central Press, Hulton Archive // Getty Images

When Marie Curie and her husband, Pierre, won their Nobel Prize in 1903, their daughter Irène was only 6 years old. She would grow up to follow in her parents' footsteps by jointly winning the Nobel Prize for chemistry with her husband, Frédéric Joliot-Curie, in 1935. They were recognized for their discovery of "artificial" radioactivity, a breakthrough made possible by Irène's parents years earlier. Marie and Pierre's other son-in-law, Henry Labouisse, who married their younger daughter, Ève Curie, accepted a Nobel Prize for Peace on behalf of UNICEF, of which he was the executive director, in 1965. This brought the family's total up to five.


The research that won Marie Curie her first Nobel Prize required hours of physical labor. In order to prove they had discovered new elements, she and her husband had to produce numerous examples of them by breaking down ore into its chemical components. Their regular labs weren't big enough to accommodate the process, so they moved their work into an old shed behind the school where Pierre worked. According to Curie, the space was a hothouse in the summer and drafty in the winter, with a glass roof that didn't fully protect them from the rain. After the famed German chemist Wilhelm Ostwald visited the Curies' shed to see the place where radium was discovered, he described it as being "a cross between a stable and a potato shed, and if I had not seen the worktable and items of chemical apparatus, I would have thought that I was been played a practical joke."


Marie Curie's journals
Hulton Archive, Getty Images

When Marie was performing her most important research on radiation in the early 20th century, she had no idea the effects it would have on her health. It wasn't unusual for her to walk around her lab with bottles of polonium and radium in her pockets. She even described storing the radioactive material out in the open in her autobiography. "One of our joys was to go into our workroom at night; we then perceived on all sides the feebly luminous silhouettes of the bottles of capsules containing our products[…] The glowing tubes looked like faint, fairy lights."

It's no surprise then that Marie Curie died of aplastic anemia, likely caused by prolonged exposure to radiation, in 1934. Even her notebooks are still radioactive a century later. Today they're stored in lead-lined boxes, and will likely remain radioactive for another 1500 years.


Marie Curie had only been a double-Nobel Laureate for a few years when she considered parting ways with her medals. At the start of World War I, France put out a call for gold to fund the war effort, so Curie offered to have her two medals melted down. When bank officials refused to accept them, she settled for donating her prize money to purchase war bonds.


Marie Curie circa 1930
Marie Curie, circa 1930.
Keystone, Getty Images

Her desire to help her adopted country fight the new war didn't end there. After making the donation, she developed an interest in x-rays—not a far jump from her previous work with radium—and it didn't take her long to realize that the emerging technology could be used to aid soldiers on the battlefield. Curie convinced the French government to name her Director of the Red Cross Radiology Service and persuaded her wealthy friends to fund her idea for a mobile x-ray machine. She learned to drive and operate the vehicle herself and treated wounded soldiers at the Battle of the Marne, ignoring protests from skeptical military doctors. Her invention was proven effective at saving lives, and ultimately 20 "petite Curies," as the x-ray machines were called, were built for the war.


Following World War I, Marie Curie embarked on a different fundraising mission, this time with the goal of supporting her research centers in Paris and Warsaw. Curie's radium institutes were the site of important work, like the discovery of a new element, francium, by Marguerite Perey, and the development of artificial radioactivity by Irène and Frederic Joliot-Curie. The centers, now known as Institut Curie, are still used as spaces for vital cancer treatment research today.

Big Questions
Where Did the Myth That Radiation Glows Green Come From?

by C Stuart Hardwick

Probably from radium, which was widely used in self-luminous paint starting in 1908. When mixed with phosphorescent copper-doped zinc sulfide, radium emits a characteristic green glow:


The use of radioluminescent paint was mostly phased out by the mid-1960s. Today, in applications where it is warranted (like spacecraft instrument dials and certain types of sensors, for example), the radiation source is tritium (radioactive hydrogen) or an isotope of promethium, either of which has a vastly shorter half life than radium.

In most consumer products, though, radioluminescence has been replaced by photoluminescence, phosphors that emit light of one frequency after absorbing photons of a difference frequency. Glow-in-the-dark items that recharge to full brightness after brief exposure to sunlight or a fluorescent light only to dim again over a couple of hours are photoluminescent, and contain no radiation.

An aside on aging radium: By now, most radium paint manufactured early in the 20th century has lost most of its glow, but it’s still radioactive. The isotope of radium used has a half life of 1200 years, but the chemical phosphor that makes it glow has broken down from the constant radiation—so if you have luminescent antiques that barely glow, you might want to have them tested with a Geiger counter and take appropriate precautions. The radiation emitted is completely harmless as long as you don’t ingest or inhale the radium—in which case it becomes a serious cancer risk. So as the tell-tale glow continues to fade, how will you prevent your ancient watch dial or whatever from deteriorating and contaminating your great, great grandchildren’s home, or ending up in a landfill and in the local water supply?

Even without the phosphor, pure radium emits enough alpha particles to excite nitrogen in the air, causing it to glow. The color isn’t green, through, but a pale blue similar to that of an electric arc.


This glow (though not the color) entered the public consciousness through this early illustration of its appearance in Marie Curie’s lab, and became confused with the green glow of radium paints.

The myth is likely kept alive by the phenomenon of Cherenkov glow, which arises when a charged particle (such as an electron or proton) from submerged sources exceeds the local speed of light through the surrounding water.

So in reality, some radionuclides do glow (notably radium and actinium), but not as brightly or in the color people think. Plutonium doesn’t, no matter what Homer Simpson thinks, unless it’s Pu-238—which has such a short half life, it heats itself red hot.


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