Why Do I Shiver When I'm Cold?

Chloe Effron
Chloe Effron

WHY? is our attempt to answer all the questions every little kid asks. Have a question? Send it to why@mentalfloss.com.

When we get cold, sometimes our bodies start moving—even if we don't mean for them to. Our teeth chatter, and different parts of our bodies shake and quake, no matter how still we try to stay. Brr! 

Shivering is one of several ways the body tries to keep warm when it's cold out. It’s part of a process is called homeostasis, which means that your body wants to keep things consistent. In other words, your insides need to stay about the same temperature, no matter how hot or cold it is outside, and shivering helps make that happen. 

When your warm body (which is about 98.6° Fahrenheit) is exposed to cold air, the heat from your body flows into the air. This is because heat always flows from a hot object to a cold object, as a way of balancing out the differences in temperature. It’s like when you put a pot of water on the stove, and the hot fire warms the cold water. Only in this case, you’re the fire, and the heat from your body is warming up the air around you. If the air is cold enough to steal your body heat, you feel cold. To make up for all the heat you’re losing to the cold air, your body shivers to try to produce even more warmth. 

If you can’t keep your body warm enough by wearing warm clothes or moving closer to the heater—say, if you go outside in a t-shirt on a snowy day—your body will try to make as much heat as it can on its own. When you shiver, your muscles tighten and relax over and over again in a short amount of time. The energy that it takes to make your muscles do that gives off heat, keeping your body a little warmer than it would otherwise be—although you might still feel chilly standing in the snow in your t-shirt. You'll warm up much quicker if you put on a coat than if you expect your body to do all the work by itself!

A Simple Skin Swab Could Soon Identify People at Risk for Parkinson's


More than 200 years have passed since physician James Parkinson first identified the degenerative neurological disorder that bears his name. Over five million people worldwide suffer from Parkinson’s disease, a neurological condition characterized by muscle tremors and other symptoms. Diagnosis is based on those symptoms rather than blood tests, brain imaging, or any other laboratory evidence.

Now, science may be close to a simple and non-invasive method for diagnosing the disease based on a waxy substance called sebum, which people secrete through their skin. And it’s thanks to a woman with the unique ability to sniff out differences in the sebum of those with Parkinson's—years before a diagnosis can be made.

The Guardian describes how researchers at the University of Manchester partnered with a nurse named Joy Milne, a "super smeller" who can detect a unique odor emanating from Parkinson's patients that is unnoticeable to most people. Working with Tilo Kunath, a neurobiologist at Edinburgh University, Milne and the researchers pinpointed the strongest odor coming from the patients' upper backs, where sebum-emitting pores are concentrated.

For a new study in the journal ACS Central Science, the researchers analyzed skin swabs from 64 Parkinson's and non-Parkinson's subjects and found that three substances—eicosane, hippuric acid, and octadecanal—were present in higher concentrations in the Parkinson’s patients. One substance, perillic aldehyde, was lower. Milne confirmed that these swabs bore the distinct, musky odor associated with Parkinson’s patients.

Researchers also found no difference between patients who took drugs to control symptoms and those who did not, meaning that drug metabolites had no influence on the odor or compounds.

The next step will be to swab a a much larger cohort of Parkinson’s patients and healthy volunteers to see if the results are consistent and reliable. If these compounds are able to accurately identify Parkinson’s, researchers are optimistic that it could lead to earlier diagnosis and more effective interventions.

[h/t The Guardian]

World’s Oldest Stored Sperm Has Produced Some Healthy Baby Sheep

A stock photo of a lamb
A stock photo of a lamb

It’s not every day that you stumble across a 50-year-old batch of frozen sheep sperm. So when Australian researchers rediscovered a wriggly little time capsule that had been left behind by an earlier researcher, they did the obvious: they tried to create some lambs. As Smithsonian reports, they pulled it off, too.

The semen, which came from several prize rams, had been frozen in 1968 by Dr. Steve Salamon, a sheep researcher from the University of Sydney. After bringing the sample out of storage, researchers thawed it out and conducted a few lab tests. They determined that its viability and DNA integrity were still intact, so they decided to put it to the ultimate test: Would it get a sheep pregnant? The sperm was artificially inseminated into 56 Merino ewes, and lo and behold, 34 of them became pregnant and gave birth to healthy lambs.

Of course, this experiment wasn’t just for fun. They wanted to test whether decades-old sperm—frozen in liquid nitrogen at -320°F—would still be viable for breeding purposes. Remarkably, the older sperm had a slightly higher pregnancy rate (61 percent) than sheep sperm that had been frozen for 12 months and used to impregnate ewes in a different experiment (in that case, the success rate was 59 percent).

“We believe this is the oldest viable stored semen of any species in the world and definitely the oldest sperm used to produce offspring,” researcher Dr. Jessica Rickard said in a statement.

Researchers say this experiment also lets them assess the genetic progress of selective breeding over the last five decades. “In that time, we’ve been trying to make better, more productive sheep [for the wool industry],” associate professor Simon de Graaf said. “This gives us a resource to benchmark and compare.”

[h/t Smithsonian]