How Ancient People Kept Time

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From sundials to crystals-how did early humans keep time, and what exactly is a "leap second?" Join Michael Aranda on SciShow as we dive into the long and strange history of timekeeping. Let's go!
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Опубликовано:

29 июн 2024

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Комментарии : 976

@Peanutbetter27 9 лет назад

Nice! I can get an extra second of sleep on June 30th! I knew Earth's rotation was good for something!

@ruchikabiswal3632 3 года назад

That's my birthday 😅😂

@hookbeak3516 3 года назад

ol' father time can offer a milli-second, & that's being generous.

@icycitrusful 3 года назад

@@ruchikabiswal3632 omg sameeee twinsiesss. I love that we got that extra second good for us

@Curly4000 2 года назад

Technically .9 second

@bobdotexe 9 лет назад

I want a smell clock. "smells like 4pm" "...wait...4...30"

@aphrog649 9 лет назад

you missed the chance to say 420 and have the perfect pun

@-KILLBOY 9 лет назад

Lily R And the microwave had 4:20 on the clock =]

@vincentmiller9714 9 лет назад

***** the microwave was set to 4:20

@jishb2505 9 лет назад

BOBdotEXE CAN YOU SMELLLLLLLLL when The Rock is cooking?

@borisrivas2929 9 лет назад

jish b i was born on april 20th the year 420 at 4:20 AM

@geoffreybrunell5592 9 лет назад

So if humans went back in time to the big bang and they left an optical clock behind, it would only be off by one second as of now? Damn that's accurate.

@dalleth 9 лет назад

Geoffrey Brunell Well... kinda. Depending on where that clock is, if it travels or had traveled, where we are in relation to it and other space timey wimey things. Time is relative to your location, and in the big bang the area of space wouldn't have existed at the beginning.

@geoffreybrunell5592 9 лет назад

Joel Crawford True, but it could be possible assuming it had not moved and had not been influenced by any outside forces or celestial bodies. But I guess that would be impossible anyways.

@FuckItSnoopy 9 лет назад

Geoffrey Brunell I have that same picture as the background on my phone.

@benoitg6933 9 лет назад

Lucian Willi the space clock would actually be late and it feels almost the same g as the earth clock, it's not related to this. what happens is the space clock travels way faster than the other which makes its relative time "dilates", making it late compared to the earth clock.

@benoitg6933 9 лет назад

***** yes you're right to notice it, however in the case of gps satellites, their speed is approximately constant so it's really the speed that dilates time in this case.

@KajsarTitus 9 лет назад

The stock market already sets billions of dollars on fire.

@kaiwenhe4677 9 лет назад

Lol

@boldjawad 9 лет назад

Titus Fridell one lol for your comment and one more lol fir your profile pic...!!

@AustiuNoMatterWho 9 лет назад

Titus Fridell yeah they don't need the wrong time, they do what they want

@glorvalmacglorvas171 7 лет назад

The people who loose money on the stock market give their money to people that are smarter than them.

@chaosdweller 6 лет назад

That's because it was hacked, atleast once.

@EvilSl0th 9 лет назад

"10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 1, happy new year." i dont know... just doesnt sound the same.

@flyingsky1559 4 года назад

@alisoncircus 4 года назад

That's why they add the second at the end of June, not December.

@ExistentialNathan 4 года назад

It was added literally in the middle of the year

@Blubb5000 4 года назад

Nobody will notice. They are all drunk already.

@user-zm5sk4ht9c 4 года назад

@@ExistentialNathan it's to remember the fallen... (second)

@bogdansonnenwirth5609 9 лет назад

I love these videos that last more than 7 minutes. They are very fun, informative and they are well made. Thank you!

@ugoleftillgorite 9 лет назад

So are we just going to ignore the hourglass?

@Xenro66 9 лет назад

***** The hourglass is a very inaccurate method of keeping time because it has to be reset every hour... It's also dependant on humidity, local gravity, temperature, etc...

@ugoleftillgorite 9 лет назад

Jordan O'C Regardless of how well they worked, they were still a big part of our time keeping history. Also, they were fairly accurate for their time period, wouldn't freeze in the winter, and were generally cheap enough for anyone to own. They also worked great at sea.

@venkatchait007 9 лет назад

***** I'm not sure about your last point, i think the constant motion and high humidity would screw with a hourglass.

@ugoleftillgorite 9 лет назад

Yijuwarp Let me rephrase that: they were popular at sea when the only other options were no clock at all or a pendulum clock. Ferdinand Magellan had 18 of them on his trip around the world.

@AngieMyst 9 лет назад

***** There was a designated person to turn it every hour, right? They work well for short-term time measurement

@kapilesh14 9 лет назад

I thought that this video could have proved very difficult to host, for any host but fantastic job done by Michael Aranda. Thank you for immaculate and accurate hosting and explanation, just like an optical clock.

@danielmartinez-wd8ov 9 лет назад

This is awesome, I've been trying to figure out this stuff on my own and here you go making a video for me, thanks guys.

@ze_rubenator 9 лет назад

Why is it so funny that the microwave is at 4:20?

@ZigZagPaddyWag 9 лет назад

Ze Rubenator 420, 4:20, or 4/20 is a code-term that refers to the consumption of cannabis and by extension, as a way to identify oneself with cannabis subculture or simply cannabis itself. Observances based on the number 420 include smoking cannabis around the time 4:20 p.m. and a.m. everyday, as well as smoking and celebrating cannabis

@52BLUE 9 лет назад

William Johansen It's 10:47am here in Australia. This theory must be flawed because I'm already celebrating cannabis.

@spacemonster7051 9 лет назад

***** well, i mean, don't let a clock tell you what to do

@52BLUE 9 лет назад

A Giant Space Monster hahaha. It's always 4:20 somewhere, I guess :)

@GarethField 9 лет назад

420 hype!

@jeffhodge7333 2 года назад

Sharp, articulate, and concise. Love it.

@NessaOfDorthonion 8 лет назад

I love scishow so much. I'm a visual learner and you guys are endlessly entertaining

@--sql 9 лет назад

So we have clocks that are more accurate than Earth itself. SCIENCE!

@davidhernandez1502 9 лет назад

Butt Poopington That is not true.

@davidhernandez1502 9 лет назад

Butt Poopington As clocks revolve around earth.

@--sql 9 лет назад

Tony joe uhhhh, what?

@MrQwerty2524 9 лет назад

Tony joe Did you watch the video?

@Twas-RightHere 9 лет назад

Tony joe Did actually watch the video? He said that we have clocks that are more accurate than the Earth, because the earth is inconsistent. That was the whole point of the leap second!!!

@joaoa13portugal 4 года назад

This got recommended to me in 2020 After 5 long years

@user-xy6eb1em9z 9 лет назад

This channel is amazing. Thank you SciShow!

@jippy33 9 лет назад

I learn so much from this channel (as well as Crash Course and SSS), I can't believe it's free:-)

@Enigmorus 9 лет назад

That 4:20 on the microwave, thanks for reminding me of the most important time

@ridered300 9 лет назад

Enigmorus yolo420 propaganda strats bro

@MinecrafterPiano 9 лет назад

Enigmorus I'm guessing that you're going to be baked by the end of the video.

@eastportland 3 года назад

Happy Hippie Christmas, today!

@RainaRamsay 9 лет назад

"If the stock market is off by 15 seconds, you might as well set billions of dollars on fire."

@someperson5506 9 лет назад

***** The value of money goes up and down. If a Canadian dollar is worth half a penny less, and you american money to switch to 20 000 000 Canadian dollars, then it goes back up (half a penny more) then you got the money at 100 000 $ less than it's worth. You've made 100 000 from a half-penny difference. These values can go up and down really quickly.

@someperson5506 9 лет назад

***** No problem. Glad I could help :)

@pzyckox 9 лет назад

some person Very informative, I was wondering about this as well. Thanks!

@someperson5506 9 лет назад

Christian Kjeldbjerg Kristensen :)

@tygrahof9268 9 лет назад

Raina Ramsay LOL That is why we need to get computers out of the equation. Trades should not be made by machines.

@bunnybabybevytv6434 4 года назад

Marvelous! The later half really kicks up the knowledge

@Alexaflohr 9 лет назад

This is a good baseline. It's sometimes difficult to find what clocks would be allowed in which periods, so this is helpful. Thanks, scishow!

@edwardneal4819 8 лет назад

"Time is an illusion. Lunch time doubly so." Douglas Adams

@diceman199 8 лет назад

The first billion years were the worst.....

@ChocolatesAfterDark 9 лет назад

An episode on the exact definition of the standard units as they are defined today would be awesome.

@shanebowden8143 9 лет назад

You people are amazing . Keep doing what you're doing

@lupiloxo2798 3 года назад

this is very educational it blows my socks off!!!!!!

@CoreyAnton 9 лет назад

Great video, but much more should have been said about the telegraph, the establishment of time zones, and the implication of clocks being synchronized with each other.

@DemPilafian 2 года назад

Covering all that would have taken too much time.

@MrT------5743 2 года назад

It was actually the railroad is the reason time was synchronized. Telegraph helped to make it possible to communicate across the distances needed to sync the clocks.

@jakefromstatefarm6969 9 лет назад

China really is the most technologically advanced country. Even thousands of years ago, they had a way to freeze time. 2:35.

@MitzvosGolem1 4 года назад

Song Su water clock they had gears chains machinery long before Europe.

@yiman7370 4 года назад

In ancient Egypt the 1st clocks appeared, not in China

@naiaddore1797 3 года назад

That was so bad it hurt my brain. 😔😂

@c.i.demann3069 9 лет назад

An excellent and very thorough explanation. Thank you.

@zacgrey6385 8 лет назад

Thanks Man. Provides Just What I Needed.

@Aramis7 3 года назад

Good video and explains a few things that other similar videos avoid. Have one question though. For mechanical watches / clocks, what did they use as reference time. E.g. John Harrison's watch had an accuracy of 1 sec/ day (pretty impressive!). How did they know that? How did they know that the watch was off by that much time? What was the reference marker or baseline against which they compared it? thanks!

@presto709 Год назад

I think they were measuring the clock against itself. Several clocks of the same time would vary over time. If they were perfectly accurate they wouldn't vary at all.

@Carlos-ln8fd 9 лет назад

Michael Aranda has the single weirdest youtube trajectory I've seen. It started in that charlieissocoollike video where he was a funny guy and his thing was being American. Then all youtubers had him like some kind of guru, the guy that made music and edited videos and knew about writing. Now he does scishow? (Well he has being doing so for a while but still. Just who is Michael Aranda?

@Tmanaz480 2 года назад

He looks like he could be the son of Seth Mcfarlane.

@BSokler1 7 лет назад

Good on you Michael Aranda! Excellent Presentation 😎😎😎. Nice to know about Timekeeping.

@theshadowtz 9 лет назад

Very interesting episode. Thanks! I especially enjoyed the title :) Nice little parody of Hawking's.

@EugeneKhutoryansky 9 лет назад

Nice episode. Thanks.

@autumnagates 9 лет назад

♡♡♡♡ Love Sci Show! ♡♡♡♡♡

@GM2k11 9 лет назад

I've been waiting for this video for so long!

@jamesjames1364 Год назад

You guys are amazing! Thank you.

@Alpha1200 9 лет назад

So if an optical clock had been activated at the beginning of the universe's existence it'd only be off by about one second now? Damn, that's pretty freaking accurate.

@dg-hughes 7 лет назад

No hourglass?

@tekman2000 2 года назад

Cool, thank you so much for this detailed explanation. It was clear and concise 😀

@gmpgreen 9 лет назад

one of the best episodes in a long time

@vorkvoyd 8 лет назад

You forgot RC oscillators. My company can use quarts crystals or a low power RC oscillators. They use the time it takes for a capacitor to charge given a certain resistance. This goes into and inverting opamp and causes oscillations. They are stable, just not always very accurate(but cheap). Quarts crystal oscillators are accurate, but can change with temperature making them less stable.

@Qermaq 9 лет назад

How do you determine how accurate a clock is? Unless you have something more dependable to measure it to??

@AnimefreakHQ 9 лет назад

***** So time in which we use is in relation to the Earth's orbit around the sun. What about in a galactic scale? How would . let's say, a person on this solar system convert a time of alpha centauri?

@cyrus9210 9 лет назад

Qermaq There is a standard atomic clock somewhere in the UK. Might be some other atomic clock, there arent that many en.wikipedia.org/wiki/List_of_atomic_clocks

@InterrobangActivate 9 лет назад

Qermaq my guess is you make many identical clocks time the same thing and the amount it varies is the accuracy

@Tha1337er 9 лет назад

Qermaq Usually by how long it takes to be off by whatever amount of seconds.

@r3d0c 9 лет назад

Qermaq clock's based on the internet use a few common servers that keep up to date with the most accurate clocks

@billswingle2672 9 лет назад

Excellent job guys!!

@thebravesirrobin. 9 лет назад

This is going to make me seem like a massive nerd but I've wanted to see a video about timekeeping and it's history for while now. It's just something I thought about one day-"How did we keep the time in the past?"-but I was too lazy to actually research it myself. Thank you, SciShow!

@ragmondead 9 лет назад

hmm I will just use the good old mississippi approach. It hasn't failed me yet.

@jaaasgoed 9 лет назад

ragmondead I know, right? We do the same here with the justice system. Paper covers rock, you hang. Non of that "DNA profiling" rubbish.

@TheVaxruo 9 лет назад

jaaasgoed yeah or like if a baby laughs it wants attention but if it cries u kill it because euthanasia

@Gruggo 9 лет назад

You know what really boggles my mind, how do we know how long it takes for any given time keeping technology to lose time. If we invent a new time keeping tech, how do we measure it's rate at which it will slow if we don't have anything more accurate to compare it to? *mind asplodes*

@sidmarx7276 2 года назад

Shadow pin "heliochronometers" were used in the 1800's along with the nautical almanac to find mechanical chronometer error.

@LemonadeMouthSomebod 9 лет назад

Great episode! I've always been boggled by the measurement of time.

@sophiemck1367 9 лет назад

The atomic clock is mind-bending to me! That's so cool.

@EATSxBABIES 9 лет назад

Man, RU-vid is not having a good time trying to render your shirt buddy, the artifacting is pretty brutal today.

@teseting 9 лет назад

EATSxBABIES Isn't that just the green screen?

@coreylando6608 9 лет назад

His face is worse. It keeps getting deathly pale and then saturating to normal levels again.

@General12th 9 лет назад

Corey Lando That's not RU-vid. That's just how his face naturally is.

@Sparagas 9 лет назад

But how they know, when atomic/optical clock will not be accurate, or that Earth orbit is off to a second etc.? How do they know the absolute time?

@user-hq5fn6yv2v 4 года назад

Well, atomic clocks are better synchronized with each other than any known periodic processes.

@error2k2 9 лет назад

It'a amazing how the time between leaps of progress keep getting smaller and smaller. We make more advancements in 100 years than humanity took in 500 to 1000.

@nuyel 9 лет назад

Thanks for this episode, best thing I've seeing all week, fascinating topic. Does anyone knows about a good book on this subject?

@lasarousi 8 лет назад

lol the microwave 420

@kylehocquard 7 лет назад

did anyone else notice the time on the microwave clock is 4:20? (6:44)

@daveylevsonart 9 лет назад

best sci show video yet!

@Actheman1978 9 лет назад

Great episode !

@landonkryger 9 лет назад

He keeps saying the leap second is about the Earth moving around the Sun. Am I missing something or did he mess up and it's about the Earth spinning on its axis?

@LordDragox412 9 лет назад

Landon Kryger Clearly, it's the Sun moving around the Earth, not the other way around, you filthy heretics! #Kappa

@aliasmask 9 лет назад

Landon Kryger - I think he's right. We measure time by distance traveled around the sun (360 degrees = 1 year) and that actual time can vary. I'm surprised it isn't more than a second off.

@landonkryger 9 лет назад

Chris Randall I don't think so. We add leap days to keep the calendar in sync with the seasons. We add leap seconds so that the sun is directly up at noon.

@Bolt2strike 9 лет назад

Yes, I believe you are correct. He did mention somewhere that the second used to be defined as a very small fraction of a day. Of which the length is determined by earths rotation.

@aliasmask 9 лет назад

Landon Kryger - Yep, you're right. Time is determined by the spin of the Earth rather than it revolving around the sun. Earth's spin is slowing down, so we need to update with leap seconds. I was thinking more about leap days.

@Lot7ix 9 лет назад

The irony is that I watched this video and missed my bus...

@curious6190 3 года назад

Excellent explanation Michael 👍

@oxymoron0o 9 лет назад

Neat! I'm so glad I watched this one!

@Bram06 9 лет назад

Question: if timekeeping were more precise accurate back in the days, would it still be June 26 2015 as I'm commenting this? (Because of inaccuracy)

@666Tomato666 9 лет назад

Bram06 no it wouldn't be 26th of June 2015 the calendars were redefined multiple times, just Gregrian vs Julian calendar differences account for over 10 days alone

@Bram06 9 лет назад

666Tomato666 From now on I'm going to assume that I live in 2100 because why the fuck not.

@666Tomato666 9 лет назад

Bram06 in Hebrew calendar it's already AM 5775

@Bram06 9 лет назад

666Tomato666 On my calendar its Jan 1 0000 0:00:00 Starting now!

@larryscott3982 6 лет назад

Bram06 Yes it would. Dates are number of whole days. And since about 1585, ties to equinox. Which doesn’t creep with tiny fractions. It’s whole days regardless if it’s a few extra seconds long.

@FuckItSnoopy 9 лет назад

This is cool and all, but why do we break up the day and time measurements into 12ths and 60ths? Why not use tenths?

@baydood510 9 лет назад

Sketchy Fella It's conventional. For most of humanity, we counted using base 12 number system, not the decimal system. A Dozen = 12, time is broken up by 12. 12 hrs, 24 hrs. 12 has much more factors : 1, 2, 3, 4, 6, and 12. 10 has less factors: 1, 2, 5 10. 1/3=.3333 In base 12 that's 1/3=4/10/=0.4 It doesn't go on forever. 12 inches = 1 foot

@thebravesirrobin. 9 лет назад

Sketchy Fella The layman's explanation is that we use those numbers because many integers divide into them. You can easily divide a quantity of 12 or 60 into halves, thirds and fourths (even more for 60) without having to deal with remainders/decimals.

@nomenomen28 9 лет назад

Sketchy Fella Every day is 24 hours long and every hour is 60 minutes. 24*60 = 1,440 minutes. If you were to divide the day into blocks of 100 minutes, and not 60, there would be 14.4 Hours in a day. If you were to divide the day into blocks of 10 minutes, and not 60, there would be 144 hours in a day. Honestly a tenths/hundredths system seems rather fitting, as it fits in with our usual way of counting things like money. We don't say $1 is ¢60, we say it's ¢100. :)

@Prismatic_Rain 9 лет назад

TheTaleOfSirRobin Sounds like just as good of an argument for keeping the imperial system of length measurement. Look at that 12 inches to a foot is best because it can easily be divided by 3.

@unvergebeneid 9 лет назад

Ghost Yeah, and somehow it's _always_ the inch-to-foot ratio that gets mentioned in this context. I wonder why that .... oh, right. Because it's the _only_ damn twelve in the whole imperial system!

@sidmarx7276 2 года назад

Mentioning the vernier-scaled heliochronometer and the armillary sphere would've been nice, as well as the folding universal latitude sundial watch. This historical stuff is the most esthetically pleasing.

@RainbowPowerRangerX 9 лет назад

Can we get a Crash Course episode talking about the social impacts of changes in timekeeping? Because it's just fascinating.

@CassesVultus 9 лет назад

Is there a standard for how far the cesium clock needs to be from the Earth's center of gravity? Because relativity is a thing.

@larryscott3982 6 лет назад

CassesVultus International Atomic Time is a very high order array of clocks all over the world. And gravity corrections are in there somewhere.

@JonathanDumeer 9 лет назад

when is the second happening?

@Dogewowm8 9 лет назад

Any second now.

@ABitOfTheUniverse 9 лет назад

Bread Bro 403,736 seconds from now

@ABitOfTheUniverse 9 лет назад

Bread Bro In other words 4 days, 16 hours, 7 minutes and 11 seconds, from ...now.

@ryanventira4286 9 лет назад

Nilguiri Ooñllñññññjii

@Snaperkid 9 лет назад

A leap second is inserted between 23:59:59 on December 31st and 00:00:00 on January 1st (thus it is 23:59:60 on December 31st) Or Between 23:59:59 on June 30th and 00:00:00 on July 1st (thus it is 23:59:60 on June 30th)

@marcusgames4518 9 лет назад

my head hurts from this SCI SHOW video

@ghostlightinthegreenroom 9 лет назад

So amazing.

@michaelkossivas7530 9 лет назад

thank god you fix that hair

@jonathanseamon9864 9 лет назад

First?

@djw11111 9 лет назад

Great videos! Fast, informative, and egotism-free yet still entertaining.

@RMoribayashi 9 лет назад

If you want to celebrate the leap second it will be at 23:59:60 Jone 30, 2015 *_UTC_* (7:59:60 EDT). You can listen to it if you have a shortwave radio (or know a ham radio operator). WWV in Colorado and WWVH in Hawaii broadcast the time on 2.5, 5, 10 and 15 MHz. At one time almost every major country had similar stations but most are gone.

@phoenixcynch9792 4 года назад

Well done Michael.

@kevinlivingston9563 6 лет назад

Damn I'm late I didn't know about this. Come to think of it. I do recall feeling extra rested that day. Must've been that extra second I slept.

@daverodick4508 9 лет назад

Awesome vid

@roccovitiello7031 8 лет назад

Very good clip

@Psyriusmusic 9 лет назад

This was really interesting :)

@surfclimbcycle 4 года назад

Cool video, thanks

@rchandraonline 9 лет назад

Just to be clear, leap seconds are added on 30-Jun or 31-Dec at 24:00:00 UTC, not at midnight in whatever local time. For example, the 30-Jun-2015 leap second was at 20:00:00 EDT (or it would likely be 19:00:00 EST during Dec).

@matteopennacchietti9831 9 лет назад

This is awesome

@stephenparallox 4 года назад

Fun Fact: Not only have clocks got more accurate, but also a lot more expensive. It started with a stick in the ground (cheapest), now to atomic and optical clocks (a LOT more expensive)

@Hubs88 9 лет назад

The leap second is going to happen in a few days, *l'm SO excited!*

@emanminus 9 лет назад

Interesting episode.

@Charles-ig6fr 9 лет назад

Around 2:45 : "Incense that changed smells every so often..." Interesting. I never heard of that one before, but it could have resulted in some interesting conversations: "What time is it?" "Cinnamon:45." "Huh?" "You know: Quarter to patchouli." "What?" "Never mind."

@urmorph 7 лет назад

Don't forget Immanuel Kant as a timepiece; it was said that his neighbors in Koenigsberg set their clocks by his daily walks at 5:00 pm.

@guilemaigre14 9 лет назад

I made a school presentation on that subject while i was still at school, few years ago. Such memories.

@joshuarieder2865 8 лет назад

+CrashCourse Through a bit of research (and taking a bit of interest since my birthday was on that day), I found the element you were looking for was Aluminum-27 in an optical clock.

@SnoopyDoofie 9 лет назад

You should have mentioned that on September 6, 1522, 18 survivors of Ferdinand Magellan's original crew of 237, were the first to circumnavigate the globe and upon arriving home in Sanlúcar de Barrameda, Spain, and shocked the world that an entire day was missing, even though they kept track of time every day since they left.

@SpawnofHastur 9 лет назад

I quite like the Clock Of The Long Now. It's not exactly as precise as a caesium clock or an optical clock, but it can run for ages without maintenance. Pretty cool.

@larryscott3982 6 лет назад

Dave Ellis The long now will be sun based time. Independent of atomic time.

@I_am_Lauren 9 лет назад

THis was beautifully structured like a well written thesis paper.

@Chocolateleg0Ofcl 9 лет назад

Sweet video

@grene1955 Год назад

I highly recommend the book (and documentary) Longitude, by Dava Sobel... the story of Harrison's invention is fascinating!

@atheryne 9 лет назад

So my birthday this year will be an extra second longer! Yay!

@Imedge6 9 лет назад

Mind blown ! Next step : the habitlity to travel in time.

@Halberdin 6 лет назад

SciShow videos run fast, too fast for me to actually understand. I think this earns them more views. 😌 One remark on the stock market example: if you need exact synchronization, you do it by (series of) events, communicated via a protocol. Such one has timers, too, but does not depend on extremely precise clocks, which can't help because there is always a delay in transmission and processing, which also can vary. One of the participants would pace the message exchange and also translate the events' point in time for external use and recording of transactions.

@lemonadeisyum 9 лет назад

Very cool! I will celebrate leap second! :)

@SuperDiablos2010 9 лет назад

All those babies born on leap second :O they will never be 1 year old ever...

@pablopicassbro9705 9 лет назад

Jesus Hernandez their corpses will

@arthurthegreat216 9 лет назад

Fantastic video! And thanks for the 420 microwave, SciShow!

@mikes246 9 лет назад

This was a clever one.

@margakis 7 лет назад

The history or keeping history? What a moment in history.

@Carnochan87 9 лет назад

I love the daylight divided by twelve is an hour... Where I live (far north) an hour in the summer would be 90 minutes. In winter it would be around 25...