Why Do We Still Use 'Knots'?

What is a knot? Neil deGrasse Tyson and comedian Chuck Nice break down how we measure nautical speed. Learn about latitude and longitude and whether aliens know about the prime meridian. How has ocean navigation changed since the age of the pirates?

Timestamps:
00:00 - Introduction: Knots
00:38 - Latitude & Longitude
03:15 - Dividing Longitude Into Arcminutes
07:34 - Airspeed & GPS
8:14 - Closing: What is a Knot?

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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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[StarTalk]

Pop Quiz Time! Convert 100 knots into km h? (let's see how the Americans fare)

[noisycarlos]

I'm surprised it didn't come up, but we do have a name for one arc minute which is nautical miles. So a knot is one nautical mile per hour.
These are used because it does make things much easier to calculate in a map, and it's used not only in ships but also in aviation.

[bestsnowboarderuknow]

The term "knots" originates from an old maritime practice. Sailors used a device called a log line to measure the speed of their ship. The log line was a rope with knots tied at regular intervals. They would throw the rope overboard and count the number of knots that passed through their hands in a specific amount of time, usually measured with a sandglass. This method allowed them to determine the ship's speed in nautical miles per hour, which is why we still use the term "knots" today

[RK-zdtf]

Neil should have started by saying a minute of latitude is one nautical mile.

[tragicgarlic]

Chuck Nice is hilarious and it's great how much he makes Neil chuckle

[StaceyGarcia-kh]

I enjoy listening to Neil talk about subjects because he is so passionate about them, and it inspires me to learn new things too.

[lucasowen]

This is the best youtube channel in the history of Youtube channels

[timh]

As someone who still knows how know to use a sextant, knots/nautical miles make sense as they are measurements of angle and it’s all spherical trigonometry.

[TheSportFlyer-xysn]

Aviation uses a complex mix of metric, imperial, and nautical measurements worldwide. We measure altitude in thousands of feet (imperial), speed in knots (as defined in this video), and temperature in Celsius (because you always want to know how close you are above or below the freezing point, ice on the wings is bad).

[nilsosinga]

Fun fact: When the Brits and French were arguing over who got to be the prime meridian, the Brits ended up winning it in exchange for changing over to the Metric system (which they didn't for a long time and still haven't *fully* done)

[lazyhoundracing]

I navigated in the US Navy in the late 70's. We had what we called "SatNav" back then primarily for position locating. We still did all of our course and speed and set and drift calculations by hand. A standard mile is 1760 yards. A nautical mile is 2000 yards. It made the math much easier. We also had to shoot the stars for I guess an emergency back up and to check our equipment to a point. Thanks for the great explanation and thank you for your time.

[welvendagreat]

I love hearing neil talk about stuff hes so passionate about things so it makes me passionate to learn new stuff aswell

[dmac]

A knot is one nautical mile per hour. The SI definition is one arcminute per hour along a line of longitude. The comes out to 2000 yards or 1850 meters and a little change.
If you work out distances on a nautical chart, the utility of the nautical mile make distances easy to measure. Aviation uses many of the same terms (port, starboard, knot and even cockpit) because they are useful for navigation. Early aviators used charts in the same way mariners use them.
The term has its origins in the age of sail where navigators would use rope with "knots" tied into it. And at the end of it is a weight. The knots are spaced at even intervals and when the rope was dropped into the water, the number of knots going in the water would be counted to get the ship's speed.

[RichardSchmidt-vg]

Originally knots were tied in a rope regular intervals and they would throw the rope over the side of the boat and count the number of knots that would pass in a certain length of time

[hadtopicausername]

While we're on the subject of navigation, the story of John Harrison, who created the first chronometer accurate enough to be used when determining longitude on sea voyages, is absolutely fascinating.

[twintailsandribbon]

Rabbit: tie them together Piglet, can you tie a knot?

Piglet: I cannot

Rabbit: Uh, so you can knot

Piglet: no, I cannot knot

Rabbit: not knot?

Pooh: who's there?

Rabbit: Pooh!?

Pooh: Pooh who?

[RobertFromEarth]

I'm french and I love it when Chuck does its french impersonation!

[ericvanvlandren]

“One at a time”
I fricken love Chuck.

[theharper]

Neil said early on the the video that although degrees were divided into minutes and seconds, there's no connection with time (apologies if I'm misquoting, I'm paraphrasing). It's true that there isn't an obvious relationship between degrees and time, but 360 degrees of longitude equates to a full day of 24 hours. Navigation by latitude and longitude requires an accurate clock. One reason why James Cook's maps were so accurate was because he had a new type of ship's clock, which enabled him to calculate longitude accurately. He was also an excellent navigator and cartographer as well. Observatories in cities like London (well, Greenwich) and Sydney had a ball on a pole on the roof which gave the crews on ships a visual indication of time by which to set their clocks. This was essential in order for them to navigate safely. I'm glad that someone else in the comments also mentioned the origin of "knots" originally being literal knots in a cord attached to a sea anchor fed over the stern. I was really surprised that these things weren't mentioned.

[darcynog]

A knot is one mile per hour, but just not the mile measured on land. They did not mention the nautical mile which is the length of an arc-minute measured along a meridian. Sailors used to measure nautical miles using a drawing compass on the nautical chart. I learned this ancient technique to obtain my boat pilot licence before GPS was widely available.