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Comment by ginko | Hacker News Reader

>In fact, it takes 4,184 joules to raise the temperature of 1kg of water by 1 degree. Or 313800 joules to raise 1kg of water by 75 degrees. That means JET could have boiled about 188 kg of water.

This is missing the heat of vaporization[1] needed to actually boil the water though, i.e. to turn 100C liquid water to 100C steam. That's another 2250kJ/kg on top of the 313.8kJ/kg you've mentioned.

It's why steam is such a great carrier of energy for industrial applications.

I guess you could argue that you wouldn't evaporate all water in the kettle, but then you do want a rolling boil. It's probably a bit up for discussion at which point you'd stop heating the kettle.

[1] https://en.wikipedia.org/wiki/Enthalpy_of_vaporization

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> I guess you could argue that you wouldn't evaporate all water in the kettle...

One does not have to argue for that interpretation - raising the temperature to boiling point, not boiling it dry, is indisputably the accepted and intended meaning of the phrase wherever English is spoken... though it would fit with a certain stereotype of scientists if a bunch of plasma physicists did not know how to make a pot of tea!

Start by assuming a spherical teapot in a vacuum...

indisputably the accepted and intended meaning of the phrase wherever English is spoken

Not exactly. In American English "bring a pot to a boil" is much more common. When I read "enough energy to boil 60 kettles of water" I thought "vaporize".

Point taken - I can't dispute the fact that you read it this way!

> Not exactly. In American English "bring a pot to a boil" is much more common. When I read "enough energy to boil 60 kettles of water" I thought "vaporize".

Disagree that this is a) a much more common phrasing or b) that your interpretation would be the common one. I've yet to run into a situation where somebody asked me to "boil some water" and intended for me to vaporize all the water in some vessel.

It's entirely disputable as evidenced by this conversation.

It's also an incredible waste of time to argue over definitions. They're always disputable because they always arise in response to two people using a word differently. Maybe they're wrong and you're right, or maybe others also use the word that way—it doesn't matter. Humility and aiming at mutual understanding is far more worthwhile.

This issue is indeed trivial, but I don't know how, in general, we are going to achieve mutual understanding without establishing an agreed-upon semantics.

It's not possible to fix a particular semantics outside a particular time and context, and certainly not possible to do so in general.

Here, as soon as someone recognizes that the amount of energy cited is way higher or lower than would be implied by their own definition, they should 1) identify the difference ("Boil here means 'boil n kettles dry' rather than 'bring n kettles to boil'") and 2) in most cases, avoid the wasted debate by adopting the other person's language if further conversation using the concept is needed.

Indeed - so it is clear what one should do here, which is to begin by assuming the author is adopting a well-established meaning within the relevant context. For this, we have a couple of clues: one is British English usage, given that this is a press release from a British laboratory, and the other is that there is a meaning in which the calculation works out correctly.

In the light of this, what is your objection to my comment? As far as I can tell, it is in conformance with your numbered principles.

Saying "X is indisputably the accepted and intended meaning of the phrase wherever English is spoken" is not in conformance with those principles at all.

There appears to be a certain irony in how, in your rather sanctimonious posts here, you seem to have generally failed to act in accordance with the very principles that you accuse me of violating.

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