Neil deGrasse Tyson Explains The International Date Line

What is the International Date Line? Neil deGrasse Tyson and comedian Chuck Nice break down the history and purpose of the IDL. How do we know we needed a date line? Find out how the need for an international date line was discovered and why it was an accident. Where did we decide to put the date line? Plus, Chuck questions the existence of Mountain Time.

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Science meets pop culture on StarTalk! Astrophysicist & Hayden Planetarium director Neil deGrasse Tyson, his comic co-hosts, guest celebrities & scientists discuss astronomy, physics, and everything else about life in the universe. Keep Looking Up!

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00:00 - The international date line is weird
02:00 - Circumnavigation & Time
08:07 - Observer Bias
11:40 - IDL Placement

[celsopinheiro]

The passenger steamer SS Warrimoo was quietly knifing its way through the waters of the mid-Pacific on its way from Vancouver to Australia. The navigator had just finished working out a star fix and brought Captain John DS. Phillips, the result. The Warrimoo’s position was LAT 0º 31’ N and LONG 179 30’ W. The date was 31 December 1899.

“Know what this means?” First Mate Payton broke in, “We’re only a few miles from the intersection of the Equator and the International Date Line”. Captain Phillips was prankish enough to take full advantage of the opportunity for achieving the navigational freak of a lifetime.

He called his navigators to the bridge to check & double check the ship’s position. He changed course slightly so as to bear directly on his mark. Then he adjusted the engine speed.

The calm weather & clear night worked in his favor. At mid-night the SS Warrimoo lay on the Equator at exactly the point where it crossed the International Date Line. The consequences of this bizarre position were many:

The bow of the ship was in the Southern Hemisphere & in the middle of summer.

The stern was in the Northern Hemisphere & in the middle of winter.

The date in the aft part of the ship was December 31, 1899.

The date in the forward part of the ship was January 1, 1900.

The ship was therefore concurrently in:

two different days,

two different months,

two different years,

two different seasons

and in two different centuries.

Euller, John (Sept.1953). "A freak of navigation". Ships and the Sea. 3. p. 18

[BSaunders]

Chuck is freaking hilarious. Adds just the right amount of levity to what is already a really interesting piece of science. Thanks both!

[matikassantos]

I'm from the Philippines and I'd like to add that Ferdinand Magellan died in the Philippine islands when he was trying to convert the native Filipinos to Christianity and got involved in the rivalry between two tribal kings. Magellan tried to convert one of those tribal chiefs by force. He had around 60 troops while the resisting natives numbered 1, 500 in the Battle of Mactan.

[gabecrigger]

You guys have shown me how much I truly love science. You have taught me so much in the recent years. I have decided to quit my factory job and go back to college to pursue a science degree. Thanks for all you do, and inspiring me to pursue something I love!

[wahn]

I appreciate Chuck so much in these episodes. In addition to his quick wit I love his intellectual curiosity, which brings out the joy in Dr. Tyson, who is an incredible science educator. Chuck sets a great example for laypeople like me who are interested in science and willing to learn many new things.

[jamescpotter]

When I was a young kid my father told me a story about the international dateline. Dad served in the 13th Army Air Corp in the South Pacific. In one of his many bombing missions (he was a tail gunner in a B-24 Liberator), the squadron took off late on a Tuesday night, bombed their target on Thursday, and returned to base on Wednesday.

[AmbrishSaxena]

Neil is one of the real messenger of the universe.

[Silvia]

Once again an interesting topic explained in an entertaining and informative way. Thanks very much.

[boryslebeda]

Well there are at least few mistakes:
1. Fernando Magellan spelled without D at the end
2. He didn't make it: dead somewhere near Indonesia.
3. They traveled westwards, not as it shown in the video
4. They actually should have gained a day and thought it was Monday instead of Tuesday, not Wednesday

[pragmaticcrystal]

Thank you for your time and effort you are much appreciated 💛

[Mikaci_the_Grand_Duke]

Sorry guys but this time you made a misstake. They thought it was Wednesday but it was Thursday. They "lost a day"! 😉

I also missed a bit more explanation this time, beacuse I think many would ask, how is it, that Magellan's ship lost a whole day, was the time passing faster for them?

Here is my explanation for those, who don't understand how it works. If you travel towards west, your days are going to be longer, beacuse you travel in the same direction as the sun goes (opposit way of the earth rotation). You are going to see the sun longer every day, because you travel "togeher" with the sun, so as a result your days are going to be longer than 24 hours. The sunset is also happening somewhat later for you, and the the sunrise too.

Here is an example. Lets assume we have a time period of 10 days that means 240 hours to travel around the world towards west. But as I said for those who are travellig, the days are going to be longer, for exampe instead of 24 hours 26.67 hours in average. Now if you divide that original 240 hours (10 normal days) with 26.67 you get 9 nine days instead of 10. That is how for Magellan's crew seemingly passed 1 day less, because their days were longer than 24 hours, still the time was passing the same way for everybody.

[pbible]

This is the most entertaining science channel ever. Neil and Chuck are quite funny, and you learn something in the process. Who could ask for more?!

[mannym]

Honestly you guys are the best! Thank you both so much for your highly entertaining explainers and the humour you both inject into them makes learning so much more fun 😂😂😂. You are the perfect combo! Thank you, thank you, thank you!

[OnLee_Quality]

There is a logical error Neil made: Magellan’s scolar would have believed he was in the past compared to the people who stayed home. So he would’ve thought it was Tuesday while the people said it was already Wednesday.

[jaredmgrant]

I have to say as someone who grew up in mountain time. It was amazing. Could catch an east coast mlb game by running home early and could catch pst games and not be tired the next morning. In Central time now and miss the BEST sports timezone for American sports.

[fc-qrcy]

this was a great episode plus more than likely factual humor..

[curtissschneider]

I think Neil has it backwards. If you travel west chasing the sun, you'll experience one less day as you will have revolved around the earth's axis one less time than everyone else. That's why you have to add 24 hours when you travel west across the international date line.

[darcioehler]

Did Neil just say " see you next Tuesday"? And did you hear Chucks omg love the two

[ktina]

I'm in the part of Florida that is in the Central Time Zone. My family on the East Coast are still confused because they continue to think all of Florida is in the Eastern Time Zone! Also, telemarketers mess this up too, not realizing that the Florida panhandle is in the Central Time Zone

[Akroness]

Love you guys I learn so much from you two!!!