The earth actually completes a rotation in less than 24
hours! It's part of what I learned a
couple nights ago.
I read the other night that Tycho Brahe didn't think the
earth could be rotating because if it did, a cannonball fired in the direction
of the earth's orbit should go further than one fired in the opposite direction
- but it doesn't.
First of all, I was confused with Brahe's confusion. If I were going to be confused about why cannonballs
don't travel further fired in one direction, I would have been thinking the one
fired in the opposite direction of the earth's rotation would have travelled
further. However, I spent some time a
while back thinking about Galilean relativity, so I was able to understand why
there is no difference between the cannonballs being fired in these directions
whether or not the earth is rotating.
As is often the case with these types of things, there is a
group who does not believe the earth rotates.
I stumbled onto this site: http://www.atlanteanconspiracy.com/2011/11/earth-is-not-moving.html Google "the earth is not moving"
and you get all sorts of fun. Most of us believe the genuineness of videos seen
from space which show the earth is spinning...nope...conspiracy.
While I can shrug off this skepticism as likely nonsense, I
was curious. If there is no physical
differences between the ideas of the earth moving around the sun or the sun
moving around the earth, how do we know the earth is moving? I had to spend
most the day pondering that and did some research on it. What a fun time.
I learned about Foucault's pendulum. Cool experiment that is. I've seen it in the science museum before,
but I never understood it. That big swinging ball hanging from the ceiling that
eventually knocks over dominoes if you have the patience to watch it
happen. This thing actually performs
differently at different latitudes. On
the equator, the pendulum has no change, at the poles it spins completely in 24
hours.
It also turns out there is a difference in the direction of
cannonballs being fired North and South (assuming they were fired far enough
for a difference to be noticed - which wasn't possible during Brahe's time). This idea is called the Coriolis effect. Paths veer right or left (from our
perspective) depending on whether we do this in the Northern or Southern
Hemisphere. This is even seen in the
direction of the rotation in storm systems of earth. Pretty cool stuff.
I also learned about the difference between a solar day and
a sidereal day. It turns out the earth
actually spins on its axis in 23 hours 56 minutes and 4 seconds. However, it takes another 4 minutes for the
sun to return to the same spot in the sky it was the day before. This is because we've moved on the earth's
orbit a bit in that time period. This
website has a good explanation of that: http://howdoweknow.org/index/twodaytypes.txt I found that very interesting.
So, some fun stuff I thought I'd pass along.
