0:12 hey esauce Michael here do you have a
0:17 best friend who is there for you 247
0:21 365 sorry that's not really good enough
0:23 if your friend truly had your back they
0:31 24.6 7 365.
0:32 365. 2421
0:35 2421
0:40 891 also George Washington was born on
0:43 February 22nd
0:48 1732 at least that's what we're told
0:50 however his family Bible says he was
0:53 born on February 11th
0:59 1731 slash two so which is it Mr I
1:01 cannot tell a lie
1:04 oh and don't even ask about
1:08 1752 in Russia 1752 looked pretty normal
1:10 but check out what the British Empire
1:13 was up to that year nothing really out
1:19 of the ordinary except Ember the second
1:22 was followed by the 14th were 11 days just
1:24 just
1:28 deleted where' they go what happened
1:30 then it is time to
1:31 to
1:36 question time and how the Earth moves
1:39 reconciling both of these things has led
1:42 to some pretty strange
1:45 things we all love time-lapse videos of
1:48 the Stars moving across the sky but
1:52 really we are the ones who are moving
1:54 tumbling Through the Universe on a giant
1:57 wet Rock vehicle called Earth with a
2:00 windshield called the sky as viewed from
2:03 above the North Pole we spin
2:06 counterclockwise West chases East I
2:08 always remember this by thinking of the
2:11 us as a weird main headed animal with
2:14 Texas and Florida legs running forward
2:18 but we don't just spin we also revolve
2:22 around the sun on a plane tilted
2:27 23.4 de relative to our spin it's kind
2:31 of nauseating at this scale but from
2:32 this perspective you can see that the
2:35 sun rising and setting is just the Earth
2:38 pointing you towards and then away from
2:42 the Sun this motion causes your Sunrise
2:44 your noon the moment when the sun is
2:48 highest in your sky before your Sunset
2:50 to more closely investigate this
2:53 movement let's talk about
2:56 meridians you are on one at this very
2:59 moment your Meridian is just align from
3:01 where where you are right now straight
3:04 towards the North and South Poles it's a
3:07 line of longitude as opposed to the
3:09 horizontal lines that lay flat when
3:12 North or South is up that we call flatitude
3:13 flatitude
3:18 or actually latitude the sun is highest
3:21 in the sky to you your noon when your
3:23 Meridian is pointed right at the Sun a
3:25 cool thing happens at this moment all
3:28 Shadows around you point directly
3:31 towards one of Earth's poles
3:36 unless you're on the subsolar point the
3:38 subsolar point is the point on Earth's
3:41 surface directly below the Sun It's
3:43 Always Somewhere you can check its
3:45 current location online links as always
3:49 in the description on The subsolar Point
3:53 Shadows Fall straight down so they can
3:56 easily disappear twice a year the
3:59 subsolar point crosses over Hawaii the
4:00 only place in in the US where it hits
4:03 land and when it does it is called
4:08 lahina noon meaning cruel Sun straight
4:10 vertical objects look unnatural during
4:12 this brief time like they don't belong
4:15 as if they were photoshopped in without
4:18 regard for reality in Honolulu a
4:20 sculpture by isamu naguchi called
4:23 skygate casts a twisted Shadow all day
4:27 every day except during lahina noon when
4:30 its shadow is a perfect
4:33 Circle you may not live in a place where
4:36 the sun ever appears directly overhead
4:39 but once every earth rotation the
4:42 subsolar point Falls somewhere on your
4:46 Meridian making it noon for you the
4:49 technical name for this noon for you is
4:53 local apparent solar noon the clock on
4:55 your wrist and the clock on your phone
4:58 don't tell you your local apparent solar
5:01 time because long ago we realized that
5:04 if every Meridian had its own time a
5:07 person just a few kilometers away seeing
5:09 different shadows than you did would
5:12 disagree with you on what time it was so
5:15 towns adopted their own time now later
5:18 on this trick was standardized and time
5:21 zones as we know them today came about
5:23 but that's not all we didn't like about
5:27 shadow-based sundal time to explore
5:30 deeper we have to begin by asking
5:32 what's a
5:34 day I mean obviously it's just the time
5:37 it takes the Earth to turn around once
5:41 right but according to what everything
5:44 else in space is moving in some way too
5:45 the universe doesn't include a
5:48 convenient sheet of graph paper at
5:51 Absolute rest we can trace paths on the
5:53 best we can do on that front is to look
5:57 at very very far far far away Stars so
5:59 far away like distant features of the
6:02 landscape out the window of a moving car
6:05 they barely move as Earth does now to
6:08 them a Meridian on earth completes a
6:11 trip around about once every 23.9
6:13 23.9
6:17 hours this is called a siderial day
6:21 siderial means pertaining to the Stars
6:23 even though the siderial day seems
6:26 pretty clear it's not what our calendars
6:29 and clocks are based on because there's
6:31 a near star whose position relative to
6:34 us has a bigger effect on our
6:37 lives the sun looking down on the North
6:40 Pole at Earth's counterclockwise spin
6:42 the Earth also moves counterclockwise
6:45 around the Sun after a siderial day the
6:48 Earth has moved a bit along its orbit so
6:50 some more rotation is required for the
6:52 same Meridian to point back towards the
6:56 sun again this longer definition of one
6:59 rotation is what the modern calendar and
7:03 clock is based on it is called the solar
7:06 day but here's the thing exactly how
7:08 long the Earth has to rotate to complete
7:13 a solar day changes day to day our
7:15 clocks are just based on the average
7:18 amount of time this takes so throughout
7:21 the year they fall ahead and behind the
7:24 sun this is a solar graph a picture of
7:26 the sun's path across the sky every
7:28 single day if our clocks actually told
7:31 us local apparent solar time if you took
7:33 a picture of the sky every day at noon
7:36 you should get a line of suns but this
7:38 is what really happens over the course
7:40 of a year it will appear as though your
7:43 clock is running slow and then fast and
7:46 then slow again and then fast again this
7:48 problem was known since at least ancient
7:52 times even if its cause wasn't in order
7:55 to reconcile the two the equation of
7:58 time was constructed in this sense
8:00 equation means to
8:02 reconcile the equation of time was
8:04 applied to what a clock said in order to
8:08 compute the real time the solar time a
8:11 sundial would show now some fancy clocks
8:14 called equation Clocks Were Made that
8:17 would do this for you but eventually we
8:20 gave up we gave up and just said no the
8:23 real time isn't what the sun says it's
8:27 what our inventions say now this
8:29 transition was a big one it was human
8:32 ity growing up it was like the first
8:33 time you realize you're stronger than
8:38 your parents we realized our time pieces
8:42 were more regular and turned our backs
8:46 on the time pieces nature had but what
8:49 causes this disagreement in the first
8:53 place as it turns out the answer
8:56 revolves around revolving the way the
8:58 Earth revolves around the Sun if the
9:01 equator faced the sun all the time and
9:03 the Earth always orbited at the same
9:06 speed the subsolar point would just stay
9:07 right there on the equator throughout
9:10 the year and the amount of extra time
9:12 spent rotating the Earth needed to do to
9:14 finish a solar day would always be the
9:17 same but those two things aren't the
9:20 case first of all the Earth's orbit is
9:24 slightly elliptical so its speed varies
9:26 throughout the year when it's moving
9:28 around the Sun faster around the
9:29 beginning of January
9:32 the amount of extra turning time needed
9:35 to complete the solar day is longer than
9:37 when it's further away from the Sun and
9:38 moving more
9:41 slowly there's more because the Earth is
9:44 tilted the subsolar point is dragged
9:46 throughout the year in a circle around
9:48 Earth that's not the Equator so it
9:51 changes Direction moving Northeast then
9:54 leveling out and going Southeast before
9:57 leveling out and going Northeast again
9:58 during times of the year when the
10:00 subsolar point is being dragged by
10:04 Earth's orbit mostly East it gains
10:08 against Earth's spin faster more time is
10:11 required for the day to finish Now by
10:13 coincidence we are alive at a time when
10:15 both of these phenomena lengthen and
10:18 shorten days at roughly the same time so
10:22 they add up making September 18th almost
10:25 a minute shorter than the longest day of
10:27 the year December
10:29 22nd for northern hemisphere experience
10:32 December has the shortest periods of
10:35 daylight but the whole Solar day from
10:38 sunrise to Sunrise is for everyone on
10:40 Earth the longest of the year on December
10:41 December
10:45 22nd people in the north just spend most
10:47 of it in
10:50 darkness Earth's Tilt it doesn't just
10:53 affect how long a day is it also affects
10:56 how long a year is this is because the
11:00 Earth's Tilt is what causes the season
11:02 for the half of the earth tilted towards
11:04 the Sun the same amount of solar
11:07 radiation is spread across less space
11:09 than it is on the other half so there's
11:12 more heat energy laid down per area this
11:16 causes what we call summer and winter
11:18 for the other half the amount of time
11:21 from one of these seasonal orientations
11:24 of the earth to its occurrence again is
11:29 called a solar year or a tropical year
11:31 it's a very useful way to define a year
11:33 because it contains every single season
11:35 exactly since it's based on the very
11:38 orientations that cause them but the
11:41 problem is this the number of solar days
11:44 that occur in a solar year is not a
11:48 whole number it's almost
11:52 365 but after that many solar days about
11:55 a quarter of a day more happens before
11:58 the solar year starts again this makes
12:01 designing a a calendar more like
12:04 designing a
12:07 calend if your calendar only ever has
12:11 365 days in a year over time those dates
12:13 will Drift from the seasonal positions
12:16 they used to occur during
12:20 unless H this extra quarter of a turn
12:23 adds up to a full day after 4 years see
12:26 March 1st is coming a Day Too Soon now
12:29 so if we just delay march by adding an
12:32 extra day at the end of February every 4
12:36 years a leap day we're back on track
12:39 leap days do not add days to your life
12:40 you're still going to live the same
12:42 number of them they just change what we
12:45 call them but really who cares about
12:48 being one day earlier every 4 years I
12:50 mean one day isn't much you'd hardly
12:54 notice it but over time well if
12:57 America's Founders had declared not only
12:59 independence from Britain but also from
13:01 leap days and abolished them from
13:06 happening today 240 years later their
13:08 calendar would be a full 2 months ahead
13:10 of Earth's position putting America's
13:14 coldest winter days in April and its
13:18 hottest summer days in October adding a
13:20 day every 4 years is what the famous
13:25 Julian calendar does introduced in 46 BC
13:28 by Julius Caesar it was the de facto
13:32 standardized West calendar for a very
13:34 long time more than a
13:38 millennium but it's not perfect look
13:41 closely leap days actually move the
13:46 calendar just slightly too far each time
13:52 because I lied 365 and a quar solar days
13:54 don't occur within one solar year the
13:57 real number is slightly less and
13:59 fluctuates year to year based on on
14:01 long-term changes to Earth and the sun's
14:04 movements which means adding one day
14:06 every four years is just a Teensy wey
14:11 too many by 1582 Julian calendar dates
14:14 were 10 days behind the seasons compared
14:16 to where they used to be now that's not
14:18 bad 10 days and more than a millennium
14:23 and a half but the Catholic Church cared
14:25 because they wanted Easter to occur
14:28 exactly when it used to centuries ago
14:29 astronomers at the time time realized
14:31 that if leap days pushed the calendar
14:34 too far behind the seasons we would just
14:36 need to celebrate fewer of them to fix
14:39 the problem specifically we would need
14:42 three fewer leap days every four
14:44 centuries the rule they wrote to achieve
14:47 this stated that every 4 years would
14:49 continue to be a leap year except if it
14:53 was divisible by 100 unless it was also
14:56 evenly divisible by 400 this removes
15:00 three every 400 years on October 4th
15:04 Pope Gregory V 13th introduced this new
15:07 calendar it took his name the Gregorian
15:10 calendar he also undid the drift that
15:12 had occurred since the early days of the
15:15 Julian and declared on October 4th that
15:18 tomorrow would be October
15:22 15th October 5th to the 14th never
15:24 happened in
15:26 1582 in countries that listened to the
15:29 pope it took the rest of the world
15:32 centuries to hop on board England and
15:35 its colonies like the soon to be United
15:38 States of America adopted the Gregorian
15:40 in September of
15:43 1752 by which point their Julian dates
15:46 were off from the seasons by 11 days
15:47 hence the disappearing of the 3rd
15:50 through 13th when adopted the first of
15:53 the year was also moved from March to
15:55 January 1st this explains why George
15:59 Washington's birthday has two answers
16:01 although more closely hitched to the
16:04 seasons than the Julian the Gregorian
16:06 calendar still isn't perfect its
16:09 difference causes dates to become one
16:17 3,216 years other calendars have been
16:19 proposed like the one standup maths
16:21 calculated that drifts off even more
16:24 slowly his video is a great watch by the
16:28 way but enough of all of this let's sit
16:31 back and enjoy Earth's movement without
16:34 trying to divide it up and name it as a
16:36 caveat keep in mind that Earth's oceans
16:39 and liquid insides and other celestial
16:41 bodies are always pulling and tugging
16:44 and sloshing around minutely changing
16:46 Earth's movements their effect is
16:48 measurable but difficult to notice at
16:50 Big scales and also don't look like much
16:53 in the short term short like the length
16:56 of a human life looking from above the
16:59 North Pole the equator SP
17:03 counterclockwise at about 1670
17:07 kmph relative to the sun earth orbits
17:09 counterclockwise at
17:14 108,000 kmph along a path tilted 23.4 de
17:17 to its spin within our local
17:20 neighborhood of stars our entire solar
17:23 system is drifting 70,000 km per hour
17:25 roughly in the direction of the bright
17:29 star Vega in the constellation of lra
17:32 and our solar system is part of a giant
17:36 Galaxy called the Milky Way on a plane
17:39 tilted about 60° approximately like the
17:41 windshield of a car looking from above
17:44 Earth's north pole our entire solar
17:47 system races clockwise around the
17:50 galactic center at about
17:56 792 th000 km per hour our whole galaxy
17:58 is also moving through the universe we
18:00 know know this because when the universe
18:04 was very young it was so hot electrons
18:07 and protons jumped around and photons of
18:10 light scattered constantly they couldn't
18:12 travel very far before scattering again
18:16 so the universe was opaque but then
18:20 around 380,000 years after the big bang
18:23 the universe cooled just enough for
18:26 electrons and protons to form
18:29 hydrogen suddenly abruptly
18:31 photons decoupled from this obstacle
18:33 course and could travel relatively
18:36 unencumbered the universe became
18:39 transparent to light and since that
18:42 moment those early photons have been
18:46 propagating through space every day
18:49 ancient photons that last scattered off
18:51 this opaque fog at the moment of
18:53 decoupling a light day further from
18:56 where Earth currently is reach us they
18:59 are part of the cosmic micro wave
19:01 background radiation it is visible in
19:04 every direction microwave because
19:05 although they used to be more energetic
19:08 the universe's expansion has redshifted
19:10 them now some parts of this radiation
19:13 are more redshifted than others because
19:16 of our own movement through the universe
19:17 controlling for the movements we've
19:20 already talked about relative to this
19:22 infinite cooling baby picture of the
19:25 universe the first and oldest detectable
19:28 light we are headed riding along in the
19:31 middle Milky Way in the direction that
19:33 the constellations of Leo and Virgo are
19:39 to us at a speed of 2.1 million kilm
19:42 hour towards a thing we don't fully
19:52 attractor this is how you on Earth's
19:55 surface are moving through the universe
19:59 aboard spaceship earth
20:05 okay now stop this is roughly 100 Years
20:08 of Earth's movement through space this
20:10 path we've traced from where we began
20:13 here is the path you will take through
20:16 the universe in your lifetime you didn't
20:19 buy a ticket for this ride your parents
20:21 signed you up without asking but
20:25 nonetheless it is quite literally the
20:27 ride of your
20:42 watching it is now time for a major
20:44 Vsauce announcement you know how for the
20:46 last couple of years we've released a
20:49 holiday box well introducing the
20:54 Curiosity Box by Vsauce we created this
20:57 thing as a quarterly box this comes to
20:59 you four times a year year and it comes
21:02 packed with amazing exclusive bauce
21:04 merchandise and incredible geeky toys
21:08 picked by myself Kevin and Jake plus as
21:10 always a portion of the proceeds from
21:11 this box goes to funding Alzheimer's
21:14 research you can get your own by
21:17 subscribing atth curiosity box.com I'm
21:20 incredibly proud of this go check it out
