Q:
If today the termometer outside shows 0 (zero Celsius) and tomorrow is going to be twice as hot as today (If I could say today is a pretty damn hot outside), what will my termometer show when I check it ?
My answers to this question were:
1- 0 Celsius = 32 Fahrenheit, so… 32*2=64 Fafrenheit = **17.777778 *Celsius:dubious:
2- 0 Celsius = 273.15 Kelvin, so… 273.152=546.3 Kelvin = **273.15 Celsius (that’s HOT)
3- 20 Celsius=… leave me the fuk alone… how the hell should I know…:mad:
The only sensible meaning is in absolute temperature. So answer 2. Zero Celcius = 273 Kelvin. So twice as hot is 546 Kelvin = 273 Celcius. If you define “hot” as a measure of heat content, then this is the correct definition of “twice as hot”.
When the weather guy says “twice as hot” it is mostly meaningless. No matter what the weather.
We could perhaps allow for a human perception of temperature. Where “twice as hot” is measured on a perceptual scale and related to measured temperature. The problem here is that 0 Celcius isn’t perceptually hot at all, and we would not have a value. It wouldn’t be double anything. We could however have a “twice as cold” metric. Although “totally numb” probably provides an absolute lower limit on such a scale.
The only way words like twice apply to temperature is when you are using absolute measurements, i.e. Kelvins. Therefore answer 2 is correct.
ETA: Aaargh … nipped by Vaughan
Degrees Celsius and Fahrenheit are interval scales of measure and do not have real zero points. Degrees Kelvin is a ratio scale with a non-arbitrary zero point. So you can’t talk about “twice” with [sup]o[/sup]C and [sup]o[/sup]F, but you can with [sup]o[/sup]K. Read up on “levels of measurement” or “scales of measure”.
Yes, occasionally you hear especially dumb weather forecasters talk about it being “twice as hot”; it does annoy me. A while ago during an unseasonably warm spring spell one of the BBC forecasters said something like “temperatures could hit 29C, that’s almost twice the seasonal average”. :smack:
I ran into this with my son’s summer take-home math packet for 6th grade.
A graph was supplied with temperature on the y-axis, and dates on the x-axis. Two points were graphed: 20 deg F for day 1 and 40 deg F for day 2. The students were asked if the temperature had doubled. (The “correct” answer was yes. :rolleyes: )
I thought this was a lousy question for sixth-graders who had never been exposed to the concept of absolute temperatures. It was a classic example of an ignorant teacher writing a poor question about something that they should have known. (I’m quite confident that anyone teaching middle school has had a chemistry course in their life. Any chemistry course includes a thorough discussion of absolute temperature when you go over the gas laws.)
What made it worse was this was a packet prepared for the whole school.
My wife convinced me not to complain to the teachers or the principal, but I did attempt to explain to my son why the question was meaningless as posed. Unfortunately, my explanation pretty much went over his head.
Writing this, I’m now I’m getting all ticked off at the school again. :mad:
Why? This is something worth complaining about. We’re all about fighting ignorance here, and here your school is busy promoting it. If you find them teaching something demonstrably incorrect, call them on it.
This one should be pretty easy to demonstrate as wrong, without bringing Kelvin into it. First, show your son a dual-scale thermometer, one that shows both centigrade and Fahrenheit. Explain that the scales are pretty arbitrary, chosen for convenience. And then have him work the problem using both scales, and he should see for himself that the answer for one doesn’t line up with the answer for the other. Then send him back to the teacher armed with the question “Why don’t they line up?” I’d be very interested in hearing the teacher’s answer.
I’d be very interested in hearing the teacher’s answer.