# So how often does atmospheric pressure drop below 26 anyway?
**URL:** https://boards.straightdope.com/t/so-how-often-does-atmospheric-pressure-drop-below-26-anyway/618377
**Category:** Factual Questions
**Created:** [April 10, 2012, 4:28pm UTC](https://boards.straightdope.com/t/so-how-often-does-atmospheric-pressure-drop-below-26-anyway/618377 "2012-04-10T16:28:42Z")
**Posts on this page:** 4
**Page:** 2
### Author:  [@Chessic\_Sense](https://boards.straightdope.com/u/Chessic_Sense)
#### Post date: [April 11, 2012, 1:45pm UTC](https://boards.straightdope.com/t/so-how-often-does-atmospheric-pressure-drop-below-26-anyway/618377/21 "2012-04-11T13:45:14Z")
> [@Nava](#):
>
> Uh, no. By that reasoning, the gas/plasma (I’ve heard it called both) inside a fluorescent tube would be at high pressures. Those are vacuum tubes… low pressure.
>
> The pressure being measured is linked to density, not to kinetic energy. As **Colophon** explained, cold air is denser than hot air - this is why hot air rises, such as in balloons.
I know that it’s denser, but I’m saying there’s not more of it. You have to think of it as a constant volume of air, not a constant volume of space. PV=nRT, where V, n, and R are constant yields lower pressure at lower temperatures.
I’m not sure what that has to do with vacuum fluorescent tubes, though. That has to do with getting the mercury (or whatever) to evaporate in the tube.
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### Author:  [@ftg](https://boards.straightdope.com/u/ftg)
#### Post date: [April 11, 2012, 1:50pm UTC](https://boards.straightdope.com/t/so-how-often-does-atmospheric-pressure-drop-below-26-anyway/618377/22 "2012-04-11T13:50:25Z")
Why rescaling is a bad idea:
A change from 26 to 27 is a about a 4% increase. If you changed the scale so that 25 becomes 0, etc., then a change from 1 to 2 sounds like a 100% increase in pressure. Even worse, going from 0 (25) to 1 (26) is an infinite percent increase. This would confuse things.
It also would create problems for the ideal gas law: PV = nRT. So Scientists would stick with a suitable “0 = a vacuum” scale and regular folk would have a different scale. And there’s already too much of that nonsense.
It’s bad enough that you meet people who think 100 degrees is “twice as warm” as 50 degrees (C or F but not K). We don’t need to add to the confusion.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [April 11, 2012, 8:40pm UTC](https://boards.straightdope.com/t/so-how-often-does-atmospheric-pressure-drop-below-26-anyway/618377/23 "2012-04-11T20:40:22Z")
> [@](#):
>
> It’s bad enough that you meet people who think 100 degrees is “twice as warm” as 50 degrees (C or F but not K). We don’t need to add to the confusion.
Personally, in regards to weather, I think of “twice as hot/cold” as meaning “twice as far from optimal comfortable temperature”. You wouldn’t say “It was perfect out yesterday, and twice as cold today”, but you might say “It was uncomfortably cold yesterday, and twice as cold today”.
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### Author:  [@Enginerd](https://boards.straightdope.com/u/Enginerd)
#### Post date: [April 11, 2012, 9:58pm UTC](https://boards.straightdope.com/t/so-how-often-does-atmospheric-pressure-drop-below-26-anyway/618377/24 "2012-04-11T21:58:46Z")
> [@ftg](#):
>
> Why rescaling is a bad idea:
>
> [snip]
>
> It also would create problems for the ideal gas law: PV = nRT. So Scientists would stick with a suitable “0 = a vacuum” scale and regular folk would have a different scale. And there’s already too much of that nonsense.
>
> [snip]
Meh, it happens all the time. No scientist I know works in inches of mercury (I had to look up the conversion before my first post). Scientific work is mostly in hPa or millibars.
> [@Chronos](#):
>
> Personally, in regards to weather, I think of “twice as hot/cold” as meaning “twice as far from optimal comfortable temperature”. You wouldn’t say “It was perfect out yesterday, and twice as cold today”, but you might say “It was uncomfortably cold yesterday, and twice as cold today”.
I’ve never heard of this, but it’s an elegant and meaningful way to think about “twice as hot (or cold).” I love it!
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