Hi guys! It's Sammy again from the Perot
Museum of Nature and Science. I've been
spending lots of time outside my
backyard as you can see making all kinds
of observations and asking questions. So
my question of the day is: why is the sky
blue and why does it appear to change
color at sunset? Let's do an experiment
at home and find out.
We'll need a rectangular container with
some water in it. A very small amount of
milk, just a few drops, just like that.
We're also going to need a light source.
I'm gonna use a lamp but you can use a
flashlight or your phone. You'll want to
be doing this experiment in a room where
you can turn the lights on and off. Now
before we get started we have to first
talk about light. Did you know that the
light coming from the Sun is actually a
mixture of all the colors of the rainbow?
Together these colors combine to form
white light. We can see all of these
colors separate when the light is bent
or refracted through something like a
prism or in this case my glass cup.
See the rainbow on my wall?
This will be important to remember later.
As sunlight travels from the Sun to the earth it has to pass through our atmosphere.
Look there's you!
Let's see what happens
when the Sun is right above our heads.
What color do you see? It looks blue.
Our atmosphere is filled with air molecules
and they get in the way of the sunlight
causing it to bounce around like our
glass did earlier. Different colors will
bounce around more than others
and blue light bounces a lot.
Now let's do that same experiment but looking at our water
from the other side. Do you see that? Now
the water looks orange and yellow like a
sunset. What's going on here? At the end
of the day or early in the morning
sunlight has a much longer journey
through the atmosphere before it reaches
you and me. By this time most of the blue
light has already scattered away leaving
colors that don't scatter as easily
behind like our vibrant reds and our oranges.
Alright guys we did it! We
figured out why the sky is blue. If you
try this experiment at home, I have one
final thing for you to think about
and that is: why do you think that the
sky is blue but not green or purple?
Something else to think about. So I can't
wait to amaze our brains together at
home next time and I hope you guys had
fun, see ya!
