XPost: sci.physics.relativity, sci.math
From: nospam@de-ster.demon.nl

Physfitfreak  wrote:

> On 4/21/25 4:43 AM, J. J. Lodder wrote:
> > Bertitaylor  wrote:
> >
> >> On Sun, 20 Apr 2025 20:10:53 +0000, J. J. Lodder wrote:
> >>
> >>> fBertitaylor  wrote:
> >>>
> >>>> On Sun, 20 Apr 2025 12:53:58 +0000, J. J. Lodder wrote:
> >>>>
> >>>>> The Starmaker  wrote:
> >>>>>
> >>>>>> At Charles Darwin's time the age of the Earth was thought to be
> >>>>>> about 75,000 years old.  (you won't believe how someone else came
> >>>>>> up with that number)
> >>>>>>
> >>>>>> He was in a rush to publish his book and noticed the numbers were
> >>>>>> wrong...
> >>>>>> ...he knew
> >>>>>> eventually somebody would have
> >>>>>> figured out you cannot change a fish to a man in 75,000 years.
> >>>>>>
> >>>>>> So he, 'made up a number'!
> >>>>>>
> >>>>>> Then when he published his book, (origin of species 1859) he wrote the
> >>>>>> age of the earth to be
> >>>>>> 306,662,400 years old.
> >>>>>
> >>>>> You are quote-mining.
> >>>>>
> >>>>> In reality Darwin wrote:      (second edition)
> >>>>> ===
> >>>>> Hence,
> >>>>
> >>>> Huh?
> >>>>
> >>>> under ordinary circumstances, I should infer that for a cliff 500
> >>>>> feet in height, a denudation of one inch per century for the whole
> >>>>> length would be a sufficient allowance.
> >>>>
> >>>> 500*12*100 is 600000 years.
> >>>>
> >>>>
> >>>>
> >>>> At this rate, on the above data,
> >>>>> the denudation of the Weald must have required 306,662,400 years;
> >>>>
> >>>> Whatever the Weald is, *hence* its height gotta be
> >>>
> >>> There you have it, talking again without understanding
> >>> of what it is all about.
> >>> You should have looked up 'The Weald' before shooting your mouth off.
> >>>
> >>>> 306662400/100 inches or 3066624 inches or 3066624/12 feet or 255552 feet
> >>>> or about 8 times the height of Mount Everest was the height of the
> >>>> Weald, whatever that may have been.
> >>>
> >>> FYI, 'The Weald' is the region between the 'North Downs'
> >>> and the 'South Downs'. (so near where Darwin lived)
> >>> The height of the original mountain that was eroded away
> >>> can be estimated from the distance betwen the North and South Downs,
> >>> which is 22 miles. (the Downs are the remains of the original slopes)
> >>>
> >>> And yes, doing the sum with 22 miles to erode gives you Darwin's
> >>> estimate of about 300 000 000 years.
> >>
> >>
> >> Erosion or height reduction is in the vertical plane. Not horizontal.
> >>
> >> Erosion of 255552 feet in the vertical plane gives us in miles
> >> 255552/(3*1760) or 255552/5280 or a bit over 48 miles.
> >>
> >> Not 22 miles which is beyond the limit of jet engines.
> >>
> >> So according to Darwin and his followers there was a mountain in the
> >> Weald whose height was in near space.
> >>
> >> Point is, what could erode that much height with no wind or water for
> >> that purpose.
> >>
> >> Not that certain physicists need be bothered by such pesky issues.
> >
> > You are both blundering idiots, with feet in mouth,
> > by pontificating on subjects you don't know the first things of.
> > Why for heavens sake?
> > Is it that important to you to belittle a genius?
> >
> > For the possibly misled kiddies who might stray into here here:
> > Mountain building, and erosion, are continuing processes.
> > Mountain ranges are more or less in quasi-static equilibrium,
> > with the continuing uplift and the erosial breakdown
> > balancing, more or less.
> > A mountain range that is no longer uplifted disappears.
> > (in some tens of millions of years)
> >
> > So 'The Weald' never was a 22 mile high mountain.
> > That 22 miles is a reasonable estimate for the amount of material
> > that was removed from it by erosion, over geologic time.
> > (from identifying continuing layers on both sides)
> >
> > So Darwin was completely right here:
> > erosion is of order of a few centimeters/century,
> > total hight of material removed by erosion
> > is of order tens of kilometers,
> > So typical ages of old mountain ranges
> > can be estimated to be in the hundreds of million of years old.
> >
> > Jan
>
> I think Darwin meant one inch of horizontal _recession_ rather than
> vertically downward erosion, for both the cliff and the Weald. And the
> funny thing about this whole thread is that probably even him, but
> certainly nor Hendry (author of that funky book you pointed at), and
> certainly nor you clarified it. So I'm left with only guesses on how
> careless some cro-magnons are, possibly including Darwin.

Horizontal or vertical doesn't matter.
No matter how, the matter covering The Weald
(tens of kilometers in both width and height)
has been removed over geological time by erosion.
That involves both horizontal and vertical transport.

An order of magnitude estimate for the time that must take
yields a time scale in the hundreds of million years,

Jan

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