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Are two heads better than one?

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Re: Are two heads better than one?

#51

Post by fainpul »

Yodel0914 wrote: post #39
jethro_tell wrote: post #37

Earlier quoted context omitted.

I’ve never heard the bring one or three, I’ve always just heard three. I think that exact saying implies that if you have two and one isn’t working out you’ll go crazy but if you have one you’ll be oblivious until it’s too late. A well serviced rolex in 2026 with laser cut gears drifts +/- 15sec per day. One with hand filed gears is going to be +/- a minute on a good day, and that’s what early navigation was using. I…

> A well serviced rolex in 2026 with laser cut gears drifts +/- 15sec per day. Modern Rolex (and Omega et al) are more like +/-2s.

You would probably use a chronometer:

"The precision of a COSC-certified chronometer must be between -4 and +6 seconds per day."

https://www.cosc.swiss/cosc-faq

Re: Are two heads better than one?

#52

Post by fainpul »

iberator wrote: post #48
jethro_tell wrote: post #37

Earlier quoted context omitted.

I’ve never heard the bring one or three, I’ve always just heard three. I think that exact saying implies that if you have two and one isn’t working out you’ll go crazy but if you have one you’ll be oblivious until it’s too late. A well serviced rolex in 2026 with laser cut gears drifts +/- 15sec per day. One with hand filed gears is going to be +/- a minute on a good day, and that’s what early navigation was using. I…

15s per day sounds EXTREME. Are you even serious? Even the cheapest Chinese hand watch has 50x better precision.

Cheap watches are almost always quartz watches (electronic). Those are much more accurate than even high end mechanical watches.

15s per day is not unusual for a good mechanical watch.

Re: Are two heads better than one?

#54

Post by kmm »

saila wrote: post #16

What happens if Bob lies to Alice 20% of the time and Alice lies to me 20% of the time but I only get input from Alice?

In that case following Alice's input is still the best strategy, but you'll be worse off: you'd only be right if both tell the truth, at 80%80%=64%, or both lie, at 20%20%=4%, for a total of 68%.

In the general case of n intermediate occasional liars, the odds of the final result being accurate goes to 50% as n grows large, which makes sense, as it will have no correlation anymore to the initial input.

Re: Are two heads better than one?

#56

Post by bandrami »

maxbond wrote: post #36
jethro_tell wrote: post #32

Earlier quoted context omitted.

You can definitely average two relatively accurate chronometers but you if you only have two it’s difficult to tell if one is way fast or way slow. In a perfect world they drift less than a minute per day and you’re relatively close to the time with an average or just by picking one and knowing that you don’t have massive time skew. I believe this saying was first made about compasses which also had mechanical failur…

> In a perfect world they drift less than a minute per day... A minute per day would be far too much drift for navigation, wouldn't it? From Wikipedia [1]: > For every four seconds that the time source is in error, the east–west position may be off by up to just over one nautical mile as the angular speed of Earth is latitude dependent. That makes me think a minute might be your budget for an entire voyage? But I don…

> A minute per day would be far too much drift for navigation, wouldn't it?

Even that was much better than the dead-reckoning they had to do in bluewater before working chronometers were invented. Your ship's "position" would be a triangle that might have sides ten miles long at lower latitudes.

Re: Are two heads better than one?

#58

Post by tlb »

thelinesnloops wrote: post #19

Sailors in the past had a similar adage: “Never go to sea with two chronometers; take one or three.” They relied on precise clocks to calculate longitude.

Sailors had a lot of harmful sayings.

It's possible to navigate without being able to measure your longitude. Like if you're looking for an island, you should first navigate to the correct latitude and then sail along that latitude until you hit the island. The route is longer, obviously. But that's what you should do if your chronometers disagree.

Re: Are two heads better than one?

#59

Post by fisian »

This principle is also highly relevant in safety critical systems for using redundant sensors. Just adding a second sensor is often not enough. Because if they disagree, which one do you trust.

One example of this is in airplanes.

Re: Are two heads better than one?

#60

Post by Luc »

thelinesnloops wrote: post #19

Sailors in the past had a similar adage: “Never go to sea with two chronometers; take one or three.” They relied on precise clocks to calculate longitude.

Any navigator worth their salt would take rather take more than fewer chronometers, for various and frankly obvious reasons.

This saying must originate with a landlubber...

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