This content explains the complex and often counter-intuitive nature of time, calendars, and our movement through the universe, highlighting how human attempts to standardize and measure these phenomena have evolved over centuries.
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hey esauce Michael here do you have a
best friend who is there for you 247
365 sorry that's not really good enough
if your friend truly had your back they
24.6 7 365.
365. 2421
2421
891 also George Washington was born on
February 22nd
1732 at least that's what we're told
however his family Bible says he was
born on February 11th
1731 slash two so which is it Mr I
cannot tell a lie
oh and don't even ask about
1752 in Russia 1752 looked pretty normal
but check out what the British Empire
was up to that year nothing really out
of the ordinary except Ember the second
was followed by the 14th were 11 days just
just
deleted where' they go what happened
then it is time to
to
question time and how the Earth moves
reconciling both of these things has led
to some pretty strange
things we all love time-lapse videos of
the Stars moving across the sky but
really we are the ones who are moving
tumbling Through the Universe on a giant
wet Rock vehicle called Earth with a
windshield called the sky as viewed from
above the North Pole we spin
counterclockwise West chases East I
always remember this by thinking of the
us as a weird main headed animal with
Texas and Florida legs running forward
but we don't just spin we also revolve
around the sun on a plane tilted
23.4 de relative to our spin it's kind
of nauseating at this scale but from
this perspective you can see that the
sun rising and setting is just the Earth
pointing you towards and then away from
the Sun this motion causes your Sunrise
your noon the moment when the sun is
highest in your sky before your Sunset
to more closely investigate this
movement let's talk about
meridians you are on one at this very
moment your Meridian is just align from
where where you are right now straight
towards the North and South Poles it's a
line of longitude as opposed to the
horizontal lines that lay flat when
North or South is up that we call flatitude
flatitude
or actually latitude the sun is highest
in the sky to you your noon when your
Meridian is pointed right at the Sun a
cool thing happens at this moment all
Shadows around you point directly
towards one of Earth's poles
unless you're on the subsolar point the
subsolar point is the point on Earth's
surface directly below the Sun It's
Always Somewhere you can check its
current location online links as always
in the description on The subsolar Point
Shadows Fall straight down so they can
easily disappear twice a year the
subsolar point crosses over Hawaii the
only place in in the US where it hits
land and when it does it is called
lahina noon meaning cruel Sun straight
vertical objects look unnatural during
this brief time like they don't belong
as if they were photoshopped in without
regard for reality in Honolulu a
sculpture by isamu naguchi called
skygate casts a twisted Shadow all day
every day except during lahina noon when
its shadow is a perfect
Circle you may not live in a place where
the sun ever appears directly overhead
but once every earth rotation the
subsolar point Falls somewhere on your
Meridian making it noon for you the
technical name for this noon for you is
local apparent solar noon the clock on
your wrist and the clock on your phone
don't tell you your local apparent solar
time because long ago we realized that
if every Meridian had its own time a
person just a few kilometers away seeing
different shadows than you did would
disagree with you on what time it was so
towns adopted their own time now later
on this trick was standardized and time
zones as we know them today came about
but that's not all we didn't like about
shadow-based sundal time to explore
deeper we have to begin by asking
what's a
day I mean obviously it's just the time
it takes the Earth to turn around once
right but according to what everything
else in space is moving in some way too
the universe doesn't include a
convenient sheet of graph paper at
Absolute rest we can trace paths on the
best we can do on that front is to look
at very very far far far away Stars so
far away like distant features of the
landscape out the window of a moving car
they barely move as Earth does now to
them a Meridian on earth completes a
trip around about once every 23.9
23.9
hours this is called a siderial day
siderial means pertaining to the Stars
even though the siderial day seems
pretty clear it's not what our calendars
and clocks are based on because there's
a near star whose position relative to
us has a bigger effect on our
lives the sun looking down on the North
Pole at Earth's counterclockwise spin
the Earth also moves counterclockwise
around the Sun after a siderial day the
Earth has moved a bit along its orbit so
some more rotation is required for the
same Meridian to point back towards the
sun again this longer definition of one
rotation is what the modern calendar and
clock is based on it is called the solar
day but here's the thing exactly how
long the Earth has to rotate to complete
a solar day changes day to day our
clocks are just based on the average
amount of time this takes so throughout
the year they fall ahead and behind the
sun this is a solar graph a picture of
the sun's path across the sky every
single day if our clocks actually told
us local apparent solar time if you took
a picture of the sky every day at noon
you should get a line of suns but this
is what really happens over the course
of a year it will appear as though your
clock is running slow and then fast and
then slow again and then fast again this
problem was known since at least ancient
times even if its cause wasn't in order
to reconcile the two the equation of
time was constructed in this sense
equation means to
reconcile the equation of time was
applied to what a clock said in order to
compute the real time the solar time a
sundial would show now some fancy clocks
called equation Clocks Were Made that
would do this for you but eventually we
gave up we gave up and just said no the
real time isn't what the sun says it's
what our inventions say now this
transition was a big one it was human
ity growing up it was like the first
time you realize you're stronger than
your parents we realized our time pieces
were more regular and turned our backs
on the time pieces nature had but what
causes this disagreement in the first
place as it turns out the answer
revolves around revolving the way the
Earth revolves around the Sun if the
equator faced the sun all the time and
the Earth always orbited at the same
speed the subsolar point would just stay
right there on the equator throughout
the year and the amount of extra time
spent rotating the Earth needed to do to
finish a solar day would always be the
same but those two things aren't the
case first of all the Earth's orbit is
slightly elliptical so its speed varies
throughout the year when it's moving
around the Sun faster around the
beginning of January
the amount of extra turning time needed
to complete the solar day is longer than
when it's further away from the Sun and
moving more
slowly there's more because the Earth is
tilted the subsolar point is dragged
throughout the year in a circle around
Earth that's not the Equator so it
changes Direction moving Northeast then
leveling out and going Southeast before
leveling out and going Northeast again
during times of the year when the
subsolar point is being dragged by
Earth's orbit mostly East it gains
against Earth's spin faster more time is
required for the day to finish Now by
coincidence we are alive at a time when
both of these phenomena lengthen and
shorten days at roughly the same time so
they add up making September 18th almost
a minute shorter than the longest day of
the year December
22nd for northern hemisphere experience
December has the shortest periods of
daylight but the whole Solar day from
sunrise to Sunrise is for everyone on
Earth the longest of the year on December
December
22nd people in the north just spend most
of it in
darkness Earth's Tilt it doesn't just
affect how long a day is it also affects
how long a year is this is because the
Earth's Tilt is what causes the season
for the half of the earth tilted towards
the Sun the same amount of solar
radiation is spread across less space
than it is on the other half so there's
more heat energy laid down per area this
causes what we call summer and winter
for the other half the amount of time
from one of these seasonal orientations
of the earth to its occurrence again is
called a solar year or a tropical year
it's a very useful way to define a year
because it contains every single season
exactly since it's based on the very
orientations that cause them but the
problem is this the number of solar days
that occur in a solar year is not a
whole number it's almost
365 but after that many solar days about
a quarter of a day more happens before
the solar year starts again this makes
designing a a calendar more like
designing a
calend if your calendar only ever has
365 days in a year over time those dates
will Drift from the seasonal positions
they used to occur during
unless H this extra quarter of a turn
adds up to a full day after 4 years see
March 1st is coming a Day Too Soon now
so if we just delay march by adding an
extra day at the end of February every 4
years a leap day we're back on track
leap days do not add days to your life
you're still going to live the same
number of them they just change what we
call them but really who cares about
being one day earlier every 4 years I
mean one day isn't much you'd hardly
notice it but over time well if
America's Founders had declared not only
independence from Britain but also from
leap days and abolished them from
happening today 240 years later their
calendar would be a full 2 months ahead
of Earth's position putting America's
coldest winter days in April and its
hottest summer days in October adding a
day every 4 years is what the famous
Julian calendar does introduced in 46 BC
by Julius Caesar it was the de facto
standardized West calendar for a very
long time more than a
millennium but it's not perfect look
closely leap days actually move the
calendar just slightly too far each time
because I lied 365 and a quar solar days
don't occur within one solar year the
real number is slightly less and
fluctuates year to year based on on
long-term changes to Earth and the sun's
movements which means adding one day
every four years is just a Teensy wey
too many by 1582 Julian calendar dates
were 10 days behind the seasons compared
to where they used to be now that's not
bad 10 days and more than a millennium
and a half but the Catholic Church cared
because they wanted Easter to occur
exactly when it used to centuries ago
astronomers at the time time realized
that if leap days pushed the calendar
too far behind the seasons we would just
need to celebrate fewer of them to fix
the problem specifically we would need
three fewer leap days every four
centuries the rule they wrote to achieve
this stated that every 4 years would
continue to be a leap year except if it
was divisible by 100 unless it was also
evenly divisible by 400 this removes
three every 400 years on October 4th
Pope Gregory V 13th introduced this new
calendar it took his name the Gregorian
calendar he also undid the drift that
had occurred since the early days of the
Julian and declared on October 4th that
tomorrow would be October
15th October 5th to the 14th never
happened in
1582 in countries that listened to the
pope it took the rest of the world
centuries to hop on board England and
its colonies like the soon to be United
States of America adopted the Gregorian
in September of
1752 by which point their Julian dates
were off from the seasons by 11 days
hence the disappearing of the 3rd
through 13th when adopted the first of
the year was also moved from March to
January 1st this explains why George
Washington's birthday has two answers
although more closely hitched to the
seasons than the Julian the Gregorian
calendar still isn't perfect its
difference causes dates to become one
3,216 years other calendars have been
proposed like the one standup maths
calculated that drifts off even more
slowly his video is a great watch by the
way but enough of all of this let's sit
back and enjoy Earth's movement without
trying to divide it up and name it as a
caveat keep in mind that Earth's oceans
and liquid insides and other celestial
bodies are always pulling and tugging
and sloshing around minutely changing
Earth's movements their effect is
measurable but difficult to notice at
Big scales and also don't look like much
in the short term short like the length
of a human life looking from above the
North Pole the equator SP
counterclockwise at about 1670
kmph relative to the sun earth orbits
counterclockwise at
108,000 kmph along a path tilted 23.4 de
to its spin within our local
neighborhood of stars our entire solar
system is drifting 70,000 km per hour
roughly in the direction of the bright
star Vega in the constellation of lra
and our solar system is part of a giant
Galaxy called the Milky Way on a plane
tilted about 60° approximately like the
windshield of a car looking from above
Earth's north pole our entire solar
system races clockwise around the
galactic center at about
792 th000 km per hour our whole galaxy
is also moving through the universe we
know know this because when the universe
was very young it was so hot electrons
and protons jumped around and photons of
light scattered constantly they couldn't
travel very far before scattering again
so the universe was opaque but then
around 380,000 years after the big bang
the universe cooled just enough for
electrons and protons to form
hydrogen suddenly abruptly
photons decoupled from this obstacle
course and could travel relatively
unencumbered the universe became
transparent to light and since that
moment those early photons have been
propagating through space every day
ancient photons that last scattered off
this opaque fog at the moment of
decoupling a light day further from
where Earth currently is reach us they
are part of the cosmic micro wave
background radiation it is visible in
every direction microwave because
although they used to be more energetic
the universe's expansion has redshifted
them now some parts of this radiation
are more redshifted than others because
of our own movement through the universe
controlling for the movements we've
already talked about relative to this
infinite cooling baby picture of the
universe the first and oldest detectable
light we are headed riding along in the
middle Milky Way in the direction that
the constellations of Leo and Virgo are
to us at a speed of 2.1 million kilm
hour towards a thing we don't fully
attractor this is how you on Earth's
surface are moving through the universe
aboard spaceship earth
okay now stop this is roughly 100 Years
of Earth's movement through space this
path we've traced from where we began
here is the path you will take through
the universe in your lifetime you didn't
buy a ticket for this ride your parents
signed you up without asking but
nonetheless it is quite literally the
ride of your
watching it is now time for a major
Vsauce announcement you know how for the
last couple of years we've released a
holiday box well introducing the
Curiosity Box by Vsauce we created this
thing as a quarterly box this comes to
you four times a year year and it comes
packed with amazing exclusive bauce
merchandise and incredible geeky toys
picked by myself Kevin and Jake plus as
always a portion of the proceeds from
this box goes to funding Alzheimer's
research you can get your own by
subscribing atth curiosity box.com I'm
incredibly proud of this go check it out
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