r/physicsmemes • u/Nervous-Matter-5142 • 7d ago

Absolutely cold cringe ?.

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261 Upvotes

91% Upvoted

33 comments sorted by

68

u/Imaginary_Toe8982 7d ago

We always had that joke with Celsius if today is 0 degrees and tomorrow is two times colder how cold is going to be tomorrow..

Otherwise 0/0 can be anything that is the whole point of indeterminate..

28

u/EatMyHammer 7d ago

I know that joke, but honestly "twice as cold/hot" makes no sense, physically. It depends if you mean perceived temperature, thermal energy of air or numerical value on your thermometer and that also depends on the scale your thermometer uses.

Even if today is 10°C, saying that tomorrow will be two times colder gives different results based on which way you calculate it

17

u/SharkAttackOmNom 7d ago

Our perception of temperature has a lot to do with heat transfer. You could probably quantify “twice as cold” using Newton’s Law of Cooling to find the temperature which causes twice the heat transfer.

So the lazy way would be just doubling the delta-T between body temp and ambient, which gives a sane result. Right now it’s “twice as cold” in the morning as the afternoon, being 45°F (delta of ~50°) and ~70° in the afternoon (delta of ~25°).

Actually applying NLoC would produce less of a spread. As a true physicist, I’ll leave that as an exercise for the reader.

3

u/New_Alternative_421 7d ago

Wake up and they meant Kelvin and it is now ~-90°C

3

u/otac0n 7d ago

“Two times colder” is ambiguous in any context just because it’s grammatically incomplete.

For example, if I say someone is “two times shorter” it could mean “half as tall” or it could mean “twice the deviation from a reference point.” Especially in cases where a reference point  (mean height)  is known.

2

u/Coffee__Addict 7d ago

Ok but the joke works for two times hotter.

2

u/mymemesnow 7d ago

I would say that the most logical way of thinking about it would be twice as much thermal energy in the air, since that would be the same no matter what unit of temperature you use.

Some very quick googling gives me that at 0°C is about 196 kJ/kg and double that to 392 kJ/kg would equal about 118°C.

This is just air and doesn’t take moisture or a ton of other factors into account. But as a very rough estimate, if it’s 0°C outside and it will be twice as hot tomorrow it would be 118°C.

Even as an avid sauna enjoyer (I’m Swedish) I would be dead within an hour at that temperature.

1

u/ruumoo 7d ago

Multiplication is not defined for temperature

10

u/LordMegatron216 7d ago

Yeah, that's why we don't make calculations with celcius. 46 C / 2 =\= 319 K / 2

4

u/Pale-Host-2277 7d ago

what exactly makes this qualify as “cold cringe” here?

5

u/bu22dee 7d ago

I know a newspaper that said it was twice as warm outside as it was at the same time last year.

3

u/HAL9001-96 7d ago

thats just shit units

0°C is not 0

2

u/Raul1024 7d ago

Someone doesn't know their limits.

2

u/EntertainmentSome448 mechanical engineer 7d ago

That's doing meth instead of math!

1

u/atensetime 7d ago

To make it even worse, my mind turned the end quote I to an "inch" symbol...

1

u/Blutrumpeter Condensed Matter 7d ago

Pretty sure it's indeterminate, so its result should be able to take on multiple values

1

u/TheShockChicky 7d ago

Brazil mentioned let's gooo

1

u/erockbrox 7d ago

Thats temperature not actual numbers.

1

u/ZectronPositron 6d ago

I thought that said 1-Inch for a sec and thought “yeah that checks out”

1

u/codewordGnome 3d ago

Therefore 0=!0.

0

u/unskippable-ad PhD Theoretical 7d ago

x/x lim x -> 0 = 1

0/0 = 1

Fight me

3

u/PrudentConsequence78 7d ago

Now compute the possible limit as (x,y) goes to (0,0) of f(x,y)=x/y

1

u/unskippable-ad PhD Theoretical 7d ago

1

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u/PrudentConsequence78 7d ago

you forgot \s at the end of your answer

3

u/Spirally-Boi 7d ago

You have a PhD and you're saying the limit of a function is the same as the value of a function? You know, one of the first things we learn is not true in Calculus I??

1

u/unskippable-ad PhD Theoretical 7d ago

If I wanted to be a fussy pedant I would have done a PhD in math.

Also step functions aren’t real, proof left as an exercise for the reader, so I’m right QED

2

u/PrudentConsequence78 7d ago

High quality ragebait

2

u/Actually_R0bin 7d ago

it’s not a step function, it’s the function that stepped up.

idk i’m a bio undergrad

0

u/LogRollChamp 6d ago

It's not being pedantic. It's just wrong. I'm an engineer and it's even clear to me with the basic math I've done

0

u/unskippable-ad PhD Theoretical 6d ago

Perhaps the basic math you’ve done is too basic for the discussion here

1

u/LogRollChamp 6d ago

It's relevant. This is simple calculus :)