Astronomy Lesson of the Day: Time Zones

just so were clear, I am 8 hours ahead of all of you on the american continent. and this isn't due to hocus pocus, or anything else, but science. astronomy, to be more precise.
Rarotonga was appropriated a wonky time zone for politics. that's different.

Michelle
bonjour
2:03pmVeronica
bonsoir
2:04pmMichelle
how is paris today?
2:04pmVeronica
rainier, but not as cold
today was a nice day
tonight it's FREEZING
i am 8 hours in the future
2:04pmMichelle
what a weird idea. time difference.
i bet it's cold. brrr
it's cold here and i imagine it's comparably colder where you is
2:05pmVeronica
why is that weird?
according to the earth, my day started before yours
not that much colder,bout the same.
winter in france is much like bc
2:07pmMichelle
it's just a funny thought. i like time differences. it's like sci-fi, and it seems pretty arbitrary.
2:07pmVeronica
it's not arbitrary! it's science! astronomy!
2:08pmMichelle
it's not scientific. rarotonga is two hours behind bc but like 10x further away than saskatchewan, which is two hours ahead.

++++++++++++

Veronicahhh in Paris says:
hey- the fact that i am 8 hours ahead, that is all due to astronomy and the earth and sunrise, right?
Jon - almost... says:
yup
Jon - almost... says:
sidereal days and whatnot
Veronicahhh in Paris says:
can you briefly explain that whole mecanism to me
Jon - almost... says:
yes
Jon - almost... says:
k so
Jon - almost... says:
first just start imagining the earth rotating, but without the whole orbit thing
Jon - almost... says:
so a 24hr day is when any point on the equator gets back to straight at the sun
Veronicahhh in Paris says:
keep going, it's going to be published
Veronicahhh in Paris says:
michelle thinks it's all hocus pocus
Jon - almost... says:
k well its real
Jon - almost... says:
so the clock is roughly based on position of the sun, so at noon, the sun is directly overhead
Jon - almost... says:
but 1/4 way around the equator, it is either sunrise or sunset
Jon - almost... says:
now you have to factor in the planets orbit....
Jon - almost... says:
now... if you imagine the same thing that you did before, the planet rotating until a point hits the same spot
Jon - almost... says:
but now move it slightly around the orbit
Jon - almost... says:
that same line actually has to turn slightly more than 360deg to point back at the sun
Jon - almost... says:
thus it is 365.4 or whatever days, instead of an even 360
Jon - almost... says:
therefore... we actually measure the year by the sidereal year, which is , you know how the planet is actually slightly off axis, we measure it by when the axis comes back to flat
Jon - almost... says:
okay
Jon - almost... says:
thats your astro lesson today

3 comments:

Ian said...

JUST LIKE THE DELTA CHELSEA!

Ish said...

Ha. It may be real but it's still based on silliness. I point you to Newfoundland's 1/2 hour time zone and the way in which the international date line snakes around the Pacific:
http://www.worldatlas.com/aatlas/infopage/dateln.gif

love love

vaughn said...

I'm gonna make Jon explain that to me again.

-V