How is a leap year caused
Why Do We Have Leap Years?
hey there welcome to life noggin
February 29th
is a very special day because it only
appears on the calendar once every four
years or so but why does this happen
well of course it all comes down to
astronomy see a year isn't actually 365
days it's just under 365 and a quarter
but what exactly is a day you learned in
school that a day is the time it takes
for the earth to rotate once on its axis
but with respect to what in order to
define something's motion it always must
be measured relative to something else
let's say we measured the Earth's
rotation with respect to the Sun so we
start counting as soon as the Sun is
highest in the sky and then stop
counting when it reaches that point a
second time this 24-hour period is
called a solar day and it's what we base
our clocks offer but what if we measured
the Earth's rotation with respect to
some distant stars instead interestingly
this day which we call a satiereal day
only takes 23 hours 56 minutes and 4
seconds but why the difference well for
demonstration purposes let's leave the
earth for a moment whoa okay now we're
here there is a massive arrow sticking
out of the earth right now how beautiful
for the earth to rotate a full 360
degrees and end up with the arrow
pointing back at those distant stars
it takes one severeal day but during
that time the earth moves a little bit
in its orbit around the Sun so the arrow
is no longer pointing in that direction
for that to happen the earth needs to
rotate a little bit more which takes
about four minutes so a solar day is
about four minutes longer than a
satiereal day and consequently stars
rise four minutes earlier every night so
now we can define the year that we use
for our calendars a tropical year or the
time it takes to go through all the
seasons is 365 point two for two solar
days that means every four years we have
just under one extra day so we simply
add another one at the end of February
but by doing so we added too much time
and now we're a little ahead so every
100 years we don't have a leap year to
make up for us overcompensating but then
that means we're behind again so every
400 years we add another day in to fix
that mistake and meanwhile all the other
leap years are happy
and if we want to get even weirder a
severeal year is 20 minutes longer than
a tropical year that's because the
Earth's access processes meaning it
spins like a top and if we use this for
our calendars eventually all the seasons
would be shifted around a few months and
unless you live in the southern
hemispheres snow in August is not okay
so anyway when in doubt just remember
that every four years it'll probably be
a leap year so just enjoy the extra day
and leave me a comment letting me know
how you're gonna spend it make sure you
come back every Monday for a brand new
video as always my name is Blanco this
has been life noggin don't forget to
keep on thinking
