## Solar day sidereal day

so this video is about the solar day

versus the side eerie all day so the

earth we're looking from the top that

will be the north pole is spinning on

its axis in this direction and so as it

rotates the sum will appear to pass

overhead from east to west during each

day and the solar day is the time it

takes for the Sun to appear overhead so

mid day from one day to the overhead mid

day the next day

that's called a solar day that takes 24

hours and as I said it's the time it

takes for the Sun to appear overhead one

day overhead next day now sidereal day

is slightly shorter sidereal day is 23

hours and 56 minutes now a side aerial

day is not based on the Sun but based on

distance stars so that from one day to

the next is not when the Sun is overhead

or when a distant star is in the same

place so we imagine a distant star over

here we see it here and then after one

complete rotation we would see it again

in the same position that takes 23 hours

and 56 minutes so the day is longer

because we are in orbit around the Sun

so if we take some here and the Earth

orbiting so time dot there is the earth

as the earth is rotating on its axis

it's also following on its path around

the Sun so as the Sun rotates it will

also move along its axis a little way so

from one day to the next the Sun the

it rotates it moves on its path and move

to say

year now that tiny movement among the

axis makes a big difference because the

Sun appears roughly at that position but

you can see that some is now slightly

further back so this amount of time is

the time it takes for the earth to do

one complete rotation on its axis this

amount of time is one complete rotation

plus a tiny bit more to account for the

fact that as its passing around it needs

to pass it needs to rotate a tiny bit

more in order for the Sun to be in the

same place so ideal is shorter because

it's the time for one complete spin

Solar is longer because it's one spin

plus a little extra bit to get the Sun

round into the same position relative to

the earth