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ExoticSalamander4 t1_jdyj0u4 wrote

Reply to comment by mperklin in Estimates suggest population growth rate to peak at 8.6 billion by madrid987

This is directly analogous to physics

Population is displacement

Growth rate is velocity

Growth rate peaking means acceleration is 0

So the article *title says acceleration will have fallen to zero by the time displacement is 8.6 billion

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SrpskaZemlja t1_jdz9k83 wrote

You have it off when you're bringing acceleration into this.

That would be the rate of change of the rate of change of population. Aka the rate at which the growth rate itself changes.

This article, beyond the bungled headline, says population will peak at 8.6 billion people.

When the amount of people stops rising and begins falling, at that moment, the growth rate is zero. The headline is totally screwed up and conflicts with the article.

There's no point anywhere here where a second derivative (acceleration) is brought in.

EDIT: Really, downvotes? You guys aren't even gonna try to tell me my math is wrong?

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quokka70 t1_je3hkp5 wrote

You are right. The article is saying that the population will peak in 2050, although its headline, which is gibberish, mentions the growth rate peaking, which is what u/ExoticSalamander4 was talking about.

Many years ago I heard a TV reporter say that inflation was accelerating at an increasing rate of speed. I'm not sure how many derivatives that is, but almost certainly more than intended.

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SrpskaZemlja t1_je3hvip wrote

Relevant funny Wikipedia excerpt:

"When campaigning for a second term in office, U.S. President Richard Nixon announced that the rate of increase of inflation was decreasing, which has been noted as "the first time a sitting president used the third derivative to advance his case for reelection."[2] Since inflation is itself a derivative—the rate at which the purchasing power of money decreases—then the rate of increase of inflation is the derivative of inflation, opposite in sign to the second time derivative of the purchasing power of money. Stating that a function is decreasing is equivalent to stating that its derivative is negative, so Nixon's statement is that the second derivative of inflation is negative, and so the third derivative of purchasing power is positive.

Nixon's statement allowed for the rate of inflation to increase, however, so his statement was not as indicative of stable prices as it sounds."

https://en.m.wikipedia.org/wiki/Third_derivative

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