Albert Einstein once said, "The important thing is to not stop questioning."
Let's see if you guys can make ol'Albert proud in another edition of Ask Joe Stuff.
[Funky music] I should really learn how to dance.
ckreativity asks: Hey Joe!
Why do humans get the "chill-down-their-spine" feeling when they experience something eerie?
Well, sometimes it happens when you're scared.
And sometimes when you hear that song you love that you feel a rush of joy or sadness.
And sometimes, when you're just plain cold.
But it's all in your head.
Now, whenever we feel threatened or chilly, or when someone touches us in a way that we've
consented to and found arousing or pleasant, a region in our brains called the hypothalamus
sends a signal to our adrenal glands to release wait for it
adrenaline.
Yes, very creative gland name.
Among other things, adrenaline can trigger rapid muscle contractions to create heat by
shivering, or it'll tug on these tiny arrector pili muscles attached to our hair follicles,
which cause them to stand on end.
Now that would have created more insulation back when we had actual fur.
The hypothalamus can also be triggered by rapid changes in emotion, which is also why
you can get chills from that one part from that one song...
You know what I'm talking about.
[Perfect pitch singing] Speaking of hair, calicoat asks: Why does
human hair have no growth limit?
Well, body hair, like the very short hair on our arms, seem to be stuck short while
hair in our heads seems to grow without limits.
And some hair, like pubic hair, is somewhere in between.
No pun intended.
But, it turns out that all hair has a growth limit.
It's just that the limit is different for different types of hair.
Hair grows in three phases.
In the anagen phase, it's actively growing and getting longer.
For an eyelash that might just be weeks, for body hair about a few months, while the hair
on our heads will actively grow for many many years.
Because if we learn anything in this video, it's that I would not look good bald.
Then all types of hair enter a transition phase for several weeks where they grow from
a growing hair to a dormant hair.
And finally they end in their hairy existence in a dormant phase before falling out and
hopefully being replaced by another hair.
thefirststarr says "Saturn is your favorite planet, right?
It's mine too, but what features make it stand out above the others?"
You mean besides these?
And these?
Besides the fact that it has awesome polar auroras just like here on Earth?
Besides the fact that it has a rotating hexagonal vortex on its pole thats wider than the Earth
and formed by these intense atmospheric wind currents that would rip your face off?
Besides the fact that Saturn is only 60% as dense as water and would float in a very very
large swimming pool?
Or that its rings are only ten meters thick despite being 150,000 kilometers across?
Or that it has at least 62 moons, one of which looks like the death star and one of which
is tugged on so hard by Saturn's gravity that it squeezes geysers of water hundreds of kilometers
into space?
I guess, besides that, not much.
janderson9788 says, "I heard you can't see stars in space with the naked eye because
there's no atmosphere to absorb the light for you to see it.
Is this true?"
HECK NO!
Astronauts can't always see stars from orbit, but it doesn't have to do with the lack of
atmosphere.
They can't see stars for the same reason that you can't see stars if you walk outside at
noon.
The sun.
Now, if astronauts are on the sunny side of Earth, a huge amount of light is being reflected
off of Earth's surface.
Way more light than any other stars, our Sun, are giving off.
Staring into the black space around a bright Earth, an astronaut's eyes don't have the
dynamic range to see those dim little specks of light when there are other sources of illumination
around.
It's like how it's hard to look out a window into the dark of night when you're in a lit
room.
And we see this on the moon too.
That's why Apollo pictures are so brilliantly lit but the sky above them is totally black.
(And it's most certainly not because they would take it in a soundstage in Southern
California.)
Now if an astronaut is on the night side of Earth and there's no light from the moon,
they can definitely see stars.
Here is some proof.
prospero101 asks, "Why does root beer fizz so much more than other sodas?"
It does, it's true.
I love this question, and I just so happen to love root beer.
Root beer used to be made of flavor extract that were steeped from roots and barks, like
sassafras, which is why it's called root beer.
These extracts contain various proteins and sugars from plants and when those are mixed
up or experience turbulence, they often form foams.
Now, it's just like how waves at the beach often form foams because they're full of protein
and molecules from dead algae.
Now anyway, the FDA declared those root extracts to be toxic a few decades ago so soda makers
had to replace them with synthetic flavors.
But people were used to having nice foamy root beer that would keep its head just like
a grown up beer.
So soda makers added synthetic foaming agents so it'd keep that slurppy, slurppy slurppitude
everyone knows is the best part of root beer.
karenhart28 asks, "What year is it?
Not in the Gregorian calendar but what actual scientific year for the earth is it?"
Now, if we calculate today's date based on the age of the universe from the Big Bang...
Well, if we average together all the different results of scientific experiments that sought
to calculate that number, we'd get 13.798, plus or minus 0.037 billion years.
Now that's an uncertainty of 37 million years, which is just 0.3%.
Not perfect, but it's pretty good.
But, the whole idea of a year is based on the Earth's orbit around the sun.
And like we talked in this video, we have many ways of defining a year.
You definitely can't have years without Earth.
So how old is this planet?
Based on radiometric dating of ancient meteorites and other really old rocks, scientists have
pegged Earth's age at 4.54 billion years with an uncertainty of 50 million years, which
is like 1%.
That's actually pretty big if you think about it.
That means somewhere between the year 4, 490, 000, 000 and 4, 590, 000, 000.
AKA, 2014 plus or minus 50 million years.
That's kind of a broad estimate.
Let me tell you what.
If you need to turn in your homework late, just tell your teacher you didn't know what
year it was.
I'll write you a note.
Bharat Narang asks, "Can you give some examples where light behaves like waves and where it
behaves like particles?"
Sure, but first I want to remind everybody that you can submit your questions about science
or anything else for the next Ask Joe down in the comments.
Or let me know if you have an idea for a future episode.
You can also follow me on twitter or at itsokaytobesmart.com.
Now check out these videos from our friend Derek at Versitasium, explaining all of the
wave particle goodness that is light.
His videos are... [cue music] illuminating.
Thanks, and stay curious.