WHY do we blow to cool something down but breathe to warm it up?
-It's not just a psychological trick - it really works.
Try it on your hands and you'll see - your breath is warm, but when you blow it feels
cold.
When you blow, the air feels cold because of the surrounding room air that gets dragged
along.
Your breath itself remains warm.
Don't believe it?
Put your hand up against your mouth and blow, it's warm, it only gets colder as you move
your hand away.
Blowing creates a jet of fast-moving air that carries the cooler surrounding air with it,
enhancing the cooling effect.
Additionally, fast-moving air increases the rate of heat loss as heat is convectively
transferred from an object to the air and whisked away!
That's why we use fans, they're not creating cold air, they're just moving the air around
- physics does the rest!
WHY shouldn't you put your hands in wet cement?
-Apparently not a lot of people know this, but cement burns!
When cement powder is mixed with water, it produces calcium hydroxide, which is highly
alkaline (pH of ~12) and thus highly caustic.
The term "caustic" means it's capable of burning, corroding or otherwise destroying living tissue
upon direct contact.
Dry cement is fine, but touching wet cement can give you cement burns, and they can be
very nasty!
If you've ever seen a celebrity set their handprints in cement, be aware that they're
using a mixture specially formulated for this purpose - you don't want to try this with
regular cement.
WHY do we get goosebumps?
-Goosebumps occur when tiny muscles called arrector pili contract, causing the hair follicles
on our skin to stand upright.
There's an arrector pili muscle for every hair follicle on the body.
They contract and make the hair stand up in response to various stimuli, like cold temperatures,
or intense emotions such as fear or excitement.
Some people even get goosebumps when listening to music they like.
In animals, the same process allows them to keep warm, or appear larger and more prickly
when they're threatened, but for us humans who aren't as furry, it's just an evolutionary
holdover, and it doesn't serve much purpose.
WHY is yawning contagious?
-Unfortunately, the exact science behind this isn't fully understood, but our current best
guess is contagious yawning is a marker of social empathy.
Studies have shown yawning is more contagious across people with strong social bonds like
friends or family than it is across strangers.
It's apparently less contagious for people who struggle with empathy or social skills,
and psychopaths who lack empathy may be largely immune to it.
It's been observered in other primates too, so it may be an instinctual non-verbal cue
a group uses to communicate to eachother that they are aware of their surroundings, promoting
others to do the same, like a survival mechanism.
WHY do birds suddenly appear every time you are near?
-Just like me, they long to be, close to you.
That's the Title of that song, if you didn't know.
WHY do we have leap years?
-Usually a year consists of 365 days, but every forth year we add an extra day to the
calender and call it a leap year, consisting of 366 days.
This is because it doesn't take the Earth 365 days to orbit the sun, it takes approximately
365 and a quarter days (365.25).
Every four years this quarter accounts for a full day, so if we don't add it to the calender,
what we consider a year would be out of sync with the Earth's rotation, and every four
years our calender would drift another day away, until eventually the seasons of the
year would be occurring in months we don't expect them to.
The extra day we add to each leap year to correct for this is February 29th - and people
who are born on this day age four times slower than the average human.
Ok I made the last part up.
WHY is it called Bluetooth?
-Bluetooth is a strange name for a short-range wireless technology.
It was developed by Ericsson, a Swedish telecommunications company, which then worked with Intel and
Nokia to standardize the technology.
They adopted "Bluetooth" as a temporary codename for this project, naming it after Viking Harald
"Bluetooth" Gormsson.
They named it after him because he united Denmark as its king, just as they were trying
to unite the PC and cellular industries with a short-range wireless link.
It's thought Harald gained the nickname "Bluetooth" because he had a tooth that was blue, surprise
surprise, probably due to dental rot.
When the time came to give the wireless technology an official name for release, the launch date
was too close to do full trademark searches for other names, so Bluetooth stuck.
The Bluetooth symbol is a bind of the viking's initials in Scandinavian runes.
Harald Bluetooth.
I wonder what he'd think about that.
That's all for today but be sure to give me your "why's" in the comments, and subscribe
for more answers.