OT: I'm confused about gravity

Its the same with a water level. But upside down That follows the curvature of the earth

For a bit read 'within a tenth of the wavelength of light' i.e piss all in the big scheme of things

And surely if they were "critical" you wouldn't be using a piece of string to position them. Even my wife's phone has a laser on it that would be more precise than a piece of string

Supposedly :- Talking, after a lecture, with an old lady, of an earth supported by a giant turtle(the old ladies idea), so Mr Russel asks what's supporting that turtle OL "it's another turtle". BR "so what supports that turtle"? OL "Obviously, Mr Russel, it's turtles all the way down".

Pratchett's disc world was supported by a four elephants standing on a singular turtle (The great A'Tuin)

It's going to droop unless somehow you can manage to apply an infinite pull. If you pull hard enough the droop may not be obvious, but it will be there.

It's much more severe. And water levels are rubbish if you're near a mountain. I have a mountain of paperwork here and it's completely upset my water level.

Bill

OK I've got off my arse. I clamped a 2m steel straightedge in the vice. I suspended a piece of string of the type used by bricklayers between the ends, just to one side. Even with as much tension as I could reasonably give it it sagged about 1mm. That's a lot more than a tenth of the wavelength of light.

That's exactly what I said. Don't do it. You've lost the plot.

I'm sure you're right.

Bill

og course it did.

Naaah. Small, very small, but eminently measurable.

Look up the Eötvös balance. Folks would carry them around and measure the horizontal components of gravity. See, a large block of underground ore deposit is similar to a mountain in its sideways pull, only less visible. But the sideways pull allows it to be detected. And a lack of pull is a sign of a less dense underground i.e. possible oil. So it is very useful in prospecting...

The Eöt-Wash group says the can measure to 1:10^13.

Thomas Prufer

In one of his excellent Youtube lectures, Susskind defines infinitesimal as " something small but non-zero whose square is zero".

OK. The why does 0!=1?

This Wikipedia page gives Newton's argument:

-- Richard

'Virtually ' I learned a long time ago never(

Try this for size:

part of the usual defintion of n factorial: n! = n*(n-1)! and at n=1:

OK I'll buy that. (No wonder mathematicians avoided zero altogether for a long time.)

I think that's sort of similar to the YouTube explanation.

When I was talking to one of the lectures explain to him how I helped a stu dent calculate power disapation in a resistor I said I asked him what 6 X 1 was and he went to his calculator, the lecture said to me oh I'm a mathema tician I don't do arithmetic and he walked off smiling.

At least you can write the algebra into a Usenet post!