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Fun Fact:-) - 40 C = - 40 F


Pawelk198604
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With curiosity, I noticed that - 40 C equal to equal to - 40 F

I wonder where it comes from

Easy.

The relation between celsius and fahreneit degrees follows this consideration: ice point for water (1atm) is 0 celsius, that is by definition of fahreneit degrees 32F; boiling point is at 100C or 180F (by definition of F).

So, relation is cel=1.8*far+32, that is a linear law of conversion. You find for this line a fixed-point (cel=far) near (-40, -40).

http://www.wolframalpha.com/input/?i=y%3D1.8x%2B32%2C+y%3Dx

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As the poster above me said, they're both linear scales with different slopes. So they need to meet somewhere. Fahrenheit has always seemed a bit of an arbitrary rollercoaster though. Picking 32 for freezing water and 0 for a 1:1:1 mixture of ice, water and ammoniumchloride seems so random to me.

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As the poster above me said, they're both linear scales with different slopes. So they need to meet somewhere. Fahrenheit has always seemed a bit of an arbitrary rollercoaster though. Picking 32 for freezing water and 0 for a 1:1:1 mixture of ice, water and ammoniumchloride seems so random to me.

Well, as I recall, when the scale was being made, that 1:1:1 solution was an easy laboratory method to make a consistent, cold temperature. Subsequently pinning the freezing point of water at 32 degrees makes the gradiations easy to mark, because 32 = 2^5 power, so you bisect the distance along your thermometer between those two pinned points five times, and you've got a length that will match up to 1 Fahrenheit degree of temperature on your homemade thermometer, and you can start scribing the lines on. Take that 32-degree length, measure it out twice more, and 32 + 64 = 96, which is where Fahrenheit pinned human body temperature.

It is the 17th century. It's going to be some time before you can go to the store and buy a thermometer.

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Von Braun designed in metric, so ...?

Yes, the entire measurement was done in Metric internally in the AGC but converted to Imperial for easy readings.

Edited by MK3424
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As the poster above me said, they're both linear scales with different slopes. So they need to meet somewhere.

They do meet, obviously, but not necessarily. Theoretically there could be two temperature scales with different slopes that have an intersection at, say, -200K. In that case scale "A" and scale "B" do not meet somewhere as that temperature doesn't exist.

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I am a service engineer in Europe. My service case is twice as big and heavy as it needs to be, because I need to carry two sets of every tool - normal and american. I just laugh it off, but my hands hurt :)

Why do you carry imperial tools? I thought every country in Europe uses the metric system.

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Easy.

The relation between celsius and fahreneit degrees follows this consideration: ice point for water (1atm) is 0 celsius, that is by definition of fahreneit degrees 32F; boiling point is at 100C or 180F (by definition of F).

So, relation is cel=1.8*far+32, that is a linear law of conversion. You find for this line a fixed-point (cel=far) near (-40, -40).

http://www.wolframalpha.com/input/?i=y%3D1.8x%2B32%2C+y%3Dx

Thanks very much

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Fahrenheit has always seemed a bit of an arbitrary rollercoaster though. Picking 32 for freezing water and 0 for a 1:1:1 mixture of ice, water and ammoniumchloride seems so random to me.

That's because it is arbitrary. Fahrenheit based his scale on the work of a Dane called Ole Romer. Romer chose 0ºF as the point which it never went below in Denmark, based on the records he had available. So it wasn't really based on anything scientific at all.

Fahrenheit, like most legacy Imperial units, is a silly system. The sooner it's completely gone the better. The world has moved on.

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Well there is one argument for imperial. It is a lot easier to design a house with feet being divisible by 3, 4, and 2 opposed to the meter being divisible by 10. It's just that threes pop up a lot more often than 5's

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Well there is one argument for imperial. It is a lot easier to design a house with feet being divisible by 3, 4, and 2 opposed to the meter being divisible by 10. It's just that threes pop up a lot more often than 5's

That's just an environment bias. You are used to measurements that are a whole number of feet, so yeah, it's easy to divide by 3. What if I gave you a plank that's 120cm long. Is that any harder to divide by 3 than a 4-foot long one? But I can divide that by 5 as well. Or by 10. Working in metric, you aren't going to have things that are just 1m long even. If it's necessary to make something for construction that's easily divided by some number of pieces, lengths can be easily adjusted to have these numbers built in already.

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Well there is one argument for imperial. It is a lot easier to design a house with feet being divisible by 3, 4, and 2 opposed to the meter being divisible by 10. It's just that threes pop up a lot more often than 5's

Houses are usually constructed with cm as unit. I'm not sure what you want to achieve with rule of thumb measurements when you build a house like this.

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