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Hey everybody!
It is deep in the heart of summer deep in the heart of Texas here.
As much as I’d love to be inside watching YouTube videos with all of you, I had to get
outside and enjoy this day.
Now that we’re out here, why don’t we check out some summer science.
We can start with all this sweat.
Sweat glands come in primarily two forms: eccrine and apocrine.
Apocrine glands are mainly found in places like armpits, and places that contribute to
body odor.
Eccrine glands are distributed throughout your whole body, and those are the ones that
most of the cooling, and the shirt soaking.
You’ve got between 1.5 and 4 million eccrine sweat glands distributed throughout your skin.
When your body’s thermostat, in the hypothalamus region of your brain, detects a rise in body
temperature or emotional changes or stress, special nerve impulses turn on your dermal
waterworks.
Sweat glands work a lot like a well.
Cells at the bottom release little packets of water, salt and other molecules into the
duct, and it rises to the surface., where the cooling happens.
Inside of a liquid, molecules are shaking around, some a bit faster than others.
Every so often one of them breaks free of the attractive forces of its neighbors and
flies off into the vapor phase.
Over time, the molecules that are left in the liquid phase are jittering less on average,
and the liquid is cooler than it was before
That cools the blood near the surface, so it flows back into your core and cools you
off as a whole.
And that might actually work if you live somewhere less humid than here in Austin.
Our bodies can make a max of 3 liters of sweat an hour, and I think I might be getting there.
I need another way to cool off.
Now that I’m chilling out off in this 70 degree spring-fed water, something else cool
is happening.
My fingers are getting all pruney.
Scientists used to think that our fingers and our skin were actually soaking up water,
but it turns out, it’s an active process.
If we sever the nerves to the hand, then…
no more pruney fingers.
There must be a good reason for it, right?
Last year, neuroscientists tested people's grip: people with pruney fingers versus people
with dry fingers, in wet conditions.
It turns out the people with pruney fingers had better grip, just like the treads of a
tire on a wet road.
As you can tell I tan extensively, but I've probably had enough sun for one day.
A sunburn is most definitely an actual burn, only instead of fire, it comes from radiation.
Our atmosphere and ozone layer absorb different wavelengths of UV light to varying degrees,
but a good amount makes it down to Earth.
When those UV rays hit your skin cells, they can damage nucleic acids, either killing the
cells, or engaging an immune system emergency response… a lot like if you cut yourself.
To repair the damage, cells release inflammatory chemicals that make your skin painful to touch.
And your skin turns red thanks to swollen capillaries that are delivering white blood
cells to the damaged area.
Those damaged cells might die and peel away, or they might respond by producing melanin,
a natural sun protectant.
But even with a tan, and whether they come from the sun or a tanning bed, UV rays can
fry your DNA into these thymine dimers, which, when repaired by your cells, introduce genetic
mutations that can cause cancer.
Ever wonder what those SPF numbers mean?
Sun Protection Factor measure how much of the UVB rays the chemicals in this sunscreen
happen to block.
Unfortunately that scale tops out around 50, so don't be fooled into paying more for higher
numbers.
Unfortunately there’s no precise measure of protection for UVA, the other UV component
in sunlight.
Bill McElligott drove a truck for 28 years, and this incredible photo shows how those
UVA rays, beaming through his driver’s side window, can age skin.
When you’re done watching YouTube for the day, grab yourself a sweet treat, head outside,
and try to find some summer science of your own.
Stay curious… and don’t forget your towel.