How Science Defines A Year


[music] It’s my birthday! [cheering] It’s been a year since we uploaded the very
first video to It’s Okay To Be Smart, and a lot has happened in the meantime. I got
a PhD, I met Bill Nye, I even Neil deGrasse Tyson, I uploaded 2 hours, twenty two hours
and twenty two hours of video and I made a lot of new YouTube friends in the process. I even beat Derek from Veritasium in an epic
YouTube arm-wrestling match. A lot can happen in a year, yet it can seem like no time has
passed at all. Time’s weird like that, it’s kind of like a river, the past keeps floating
away behind us, and the future keeps rushing towards us, yet we’re stuck here paddling
our little boats in the moment we call now. Except as it flows by, each of those nows
becomes a then, you can never quite grab on to them. Instead we must mark our journey with mileposts
of our own invention, seconds minutes, hours, days, weeks, months, and years. How do you measure a year? In daylights, in
sunsets, in midnights, or cups of coffee? I’ve had about 620 cups this year, and since
coffee’s a diuretic, that means I’ve made about 550 liters of urine. I’ve also left behind 325 kilograms of poop,
4 kilograms of skin cells, and 27,000 hairs, most of which I’ve replaced, hopefully. I’m
made a lot more than just YouTube videos this year too, including 3.5 centimeters of fingernails,
15 centimeters of hair, 73 trillion red blood cells, 1400 liters of sweat, 360 liters of
saliva, and 80 liters of tears. A year can also be a distance, the light from
the very first view of my very first video would have traveled 9.5 trillion kilometers
by now, if you and your brain hadn’t gotten in the way first. We’ve also come a long way,
together. Our galaxy is 9.5 billion kilometers closer to our neighboring galaxy, Andromeda,
and our solar system has traveled 7.2 trillion kilometers around the Milky Way. Closer to
home, our moon is 3.8 centimeters farther away from our revolving Earth, which has spun
me around 12.7 million kilometers from here at my latitude in Austin, TX. Earth itself
has traveled 940 million kilometers around the sun. During our trip around the sun, the position
of the stars in the sky changes from night to night. The amount of time it takes a star
or constellation to reach the same point in the sky at the same time of day is 365 days
6 hours 9 minutes 9.76 seconds, or a sidereal year. For most of human history, with people farming
their farms and churches doing their churching, seasons have been the best way to mark a year.
The word “year” actually shares a root with the Greek word “hora” which means “season”.
The tilt of the Earth is what gives us those seasons. Here’s where things get a little complicated.
As Earth spins on its axis, it wobbles a bit like a top. Right now, the north pole points
toward Polaris, but one day in the future, because of that wobble wobble, we’ll have
to pick a new North Star. Of course the universe doesn’t care what we
call winter or summer, and that wobble is out of sync with our trip around the sun.
That means if we based our calendar on sidereal years, the seasons would quickly get out of
sync, Christmas would end up in July, dogs and cats, living together, mass hysteria! Let’s try something different. if we track
the position of the sun in the sky every day, it makes this awesome shape called an analemma,
with two solstices at the top and bottom, and two equinoxes. If we measure the amount
of time between two equinoxes, it ends up being 21 minutes shorter than a sidereal year.
We call that a tropical year, and that’s what we base our calendar on, at least here in
the west. Of course, no one was around in the beginning
to plan any of this planet/solar system stuff, and even a tropical year doesn’t divide up
evenly into days, so we have to correct it with a complex system of leap years, which
CGPGrey explains really well in this video. And that’s even the only way to define a year,
you can find out more about thatin this video from minutephysics. Time is so familiar, but it’s so hard to describe.
Whether we call it a day, a year, or nothing at all, one thing’s for sure, it marches on,
and thanks to entropy, in one direction: forward. Who knows what the next year will bring, or
even tomorrow? I can’t wait to find out. Thanks everybody! Stay curious! Why don’t you take a minute, or an hour, and
take a look back at the past year before it floats too far away.

99 thoughts on “How Science Defines A Year

  1. Since Daft Punk just won all them grammys, I think it would be cool for you to do a video on the science and history of synthesizers!  They are very interesting and the science behind the soundwaves they produce as well as how they produce them is a very cool topic!

  2. 3:02 "the word 'year' actually comes from the Greek word 'hora' which means season."

    Sorry to do this, but the word "year" in no way "comes from" Greek. It comes from Old English ġēar, which comes from Proto-Germanic *jērą, which comes from Proto-Indo-European *yeh₁r- which means year (the meaning stayed intact all the way to Modern English!)

    This Proto-Indo-European root, finally, is where the Ancient Greek ὥρα ("hōra").

    "year" and "ὥρα" come from the same Proto-Indo-European word, but that does not mean that, as you said, "the word 'year' actually comes from the Greek word."

    (As for the word "hour," that is borrowing from French "houre" ultimately derived from Latin "hora," which was a borrowing of the Ancient Greek "ὥρα")

  3. Congratulations on your Ph.D! That's great that you know Michael and others on youtube who actually expand their viewers' knowledge.

  4. Your channel is amazing 🙂 I'm so glad I found it. Here's for another good year with lots of viewers and subscribers to come.

  5. I know it's pedantic, but it really bothers me in the video that Orion at 2:41 is both moving the wrong direction and at the wrong angle to the horizon.

  6. I kinda zoned out the video the. Heard one d then i reap,wyed the while video over again i realized he ddint mean the band

  7. Wait, is that Vi Hart wearing a normal outfit? 😮 
    >_>
    <_<
    Anyway, your video with Emily Graslie brought me here, and I love your videos so far!

  8. However, don't we have the exact definition of a second with the oscillations of Caesium-133? So 1 second*60*60*24*365. I also see the problem here though, but leave some thoughts on this.

  9. Has anyone noticed the different kinds of science these sciency youtubers do? I mean Vsauce has a mixture of plain old science and philosophy where as Think Fact has science elements but is a more cultural side to science, and then of course there are Youtube Channels like SciShow that only ever show things that everyone would first think about when you hear science (Chemistry, Astronomy etc etc).

  10. a year and a lightyear are not the same thing, one measures time the other measures space -_- They just happen to share 4 letters

  11. Hello? This is Younggill from Korea. I am so glad to know you, Joe! Your show, 'It's OK to be smart' is really educational and very informative. I should say, very scientific literally. I totally enjoy watching every episode. Thank you very much for making that much great show! I am so much appreciative. It's that time again, Merry Christmas and a Happy New Year! You always say at the end of show, 'Stay Curious!.' Where does time go, anyway?

  12. at 3:20: That graphic is misleading. it seems to imply that our rotational axis oscillates catastrophically more than it really does.

    Seasons are not due to the rotational axis changing throughout a year. In fact, our rotational axis hardly changes at all. Because it doesn't change, we have different hemispheres tilted towards the sun depending on whereabouts we are in our orbit.

  13. @0:12 – Or it just turned 6am.
    Congratz, you survived! :]

    (1 free Internet, or Cookie of your choosing for whoever gets this painfully obvious reference.)

  14. Please and thank you to answer this question. What if the earth spins the other way around instead of the way it's spinning now.

  15. You beat Derek?! DEREK FROM VERITASIUM?! Well that's a feat of strenght! I once saw a vídeo of Derek doing a chin-up contest with some other dude in the subway and Derek pulled like more than 20 chin-ups in a row! MADNESS! 😀

  16. Joe, I must disagree with you about the English word "year" coming from the Greek word "hora". Hora and geār are both words and they come from languages. I'm also going to become a linguist. I study words often so I believe I know my stuff.

    I believe "geār is related to "hora", and they most likely share a common Indo-European, (or, Proto-Indo-European, whichever you prefer saying), ancestor because of this portion of relation. I believe "year" does not come from Greek though.

    This is why: it comes from the Old English word, "gēar", (or, geār, [I can't remember for certain what the spelling is]). I find that you have provoked uncertainty in my mind though, so in a short while I will out the dictionary to make sure which one of us is communicating truth.

    I hope I wasn't harsh. If I was harsh, then I hope I wasn't too harsh.

    Happy birthday! I like your channel.

  17. If time is exact using any simple method, then why do we see the sun at noon every day of the year? If we mark a point in time, where at noon we see the sun, say Jan01, then wait 4380hrs at July01 why does the sun appear at noon? Shouldn't it be midnight?

  18. 525,600 minutes,
    525,000 moments so dear,
    525,600 minutes,
    how do you measure, measure a year?
    In daylights,
    In sunsets,
    In midnights,
    in cups of coffee
    In inches,
    In miles,
    In laughter, and strife
    In… 525,600 minutes how,
    Do you measure
    A year in the life?
    KEEP IT GOING!

  19. This is very well done and I thank you for presenting real science. However, there is one possible point of confusion. At about 4:00 it is implied that the Sun is at the cross-over point of the analemma on the Equinoxes. It is not. The cross-over point is in April and August. http://en.wikipedia.org/wiki/File:Analemma_Earth.png

  20. In one year, the solar system travels 7.2 trillion meters, not kilometers. Otherwise, that would be insanely close to the speed of light!!

  21. 4:01 The equinoxes are not where the line(s) of the analemma cross but a bit further down half-way between the solstices. Additionally, since 1955 the tropical year is not the average distance between two spring equinoxes, and the distance between two spring equinoxes is different from the distance between two autumn equinoxes.

  22. Yet the North and South Poles (Should be having the exact exposer to the the Sun, but every 6 months from each other) and are TOTALLY Different. Be Smart, The Earth isn't a Ball.

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