At -40°C temperature, the Fahrenheit scale also shows -40°F.

But how is this ever possible? They are two different scales! What's the intuition behind this?

This is the image


closed as off-topic by WillO, user191954, stafusa, ZeroTheHero, Jon Custer Sep 16 '18 at 3:41

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  • 5
    $\begingroup$ Everyone who is zero inches tall is also zero feet tall. But how is this ever possible? Feet and inches are not the same thing! $\endgroup$ – WillO Sep 15 '18 at 4:06
  • 1
    $\begingroup$ Similarly how can two cars travelling at different velocities be at the same point? $\endgroup$ – Mohammad Zuhair Khan Sep 15 '18 at 4:41

The intuition I use is basically something like the following graph.Temperature intuition graph

They are different scales but they are both linearly proportional to the temperature and they must cross somewhere because they are not parallel. The lines would be parallel if one degree difference in fahrenheit was the same as one degree difference in celsius but this is not the case (it is actually the case with celsius and kelvin, which means there is no such temperature for those scales).

The formula to convert from celsius to fahrenheit is:

$$F^{\circ} = 1.8C^{\circ} + 32 $$

and you can just use algebra to work out the value at which they are equal.


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