Slide rules

ISTR we used 22/7 in simple calculations at school. At university, my slide rule had a pi mark.

Useful for a 16 bit computer that doesn't do decimals. BBC Micro Forth used 355/113.

You can, but it depends on how accurate you want it to be. You don't sound like an engineer.

If you can find an application where you need more accuracy please do let us know.

GPS: it mandates 3.1415926535898 - neither more nor less accurate

More than 'good enough' for most things, certainly any Nav than most people will be doing. In the pre-GPS days of Transat, one of the calculations I used to do involved checking positions from the raw time data*. I can't recall the exact number of decimal points I used but it wasn't huge.

It's good to 7 digits IIRC

I regularly calculate the circumference of the universe given its radius.

Does a hypersphere have a circumference?

You both seem to be making the assumption that the universe is finite, not to mention that since spacetime is not flat, the relationship between circumference and radius is not necessarily so straightforward.

#Paul

What is 'Transat' in this context?

The Germans in WWII could locate a <100 yard wide radio beam over a target at >200 miles range, to give their bomber force a bombing accuracy rather better than could be achieved with daylight methods, using seven-figure logs to set up the beams over the target.

They had published the tables prior to WWII, with a prize for anyone who discovered an error. The Brits were very good at this, winning a number of prizes...

Perhaps I should have said, circumference of the known or visible universe.

Frequency?

Knickebein was ~30 Mc/s, but I was referring to X-Gerate aka the 'Rivers' beams on ~70 Mc/s.

Transat was was the name of the satellites and they were provided the signals for the Transit Nav system. (Not sure why there were two names although the satellites had (at least) two roles from memory so perhaps that is the reason.

It was the first sat based nav system. Mainly used by the US but the UK used it, especially the Royal Navy. It was used until the 1990s as I recall although it was in the 80s I was using it.

I studied Engineering to degree level in the late 60's and a slide rule was an essential and indispensable tool. I still have mine. It's a Thornton P201. Two sided with 3 "Log Log" scales (LL1, LL2 and LL3) which I never did find a use for. Still has a silky smoooth action. Talk in earlier posts about the accuracy of calculations made me smile - we used to call it a "guessing stick". Nothing annoys me more these days than football commentators who refer to an accurate pass as a "slide rule pass"! Pete

I have a Thornton AA010. Also two sided, LL1, LL2, LL3 (and inverse LL1,LL2,LL3). And lots of other scales I don't remember! I don't know where the manual went.

Ah. It seems that mine has: LL1-3, LL1-3 reciprocal, Reciprocal C and D, Pi-displaced C and D (conventional multiplication), cube roots, logarithms, orthodox trigonometric, vector analysis ...

Bloody clever these things were!

Just dug out of the drawer.. mine is an Aristo scholar with more scales than I ever found useful. Because it does not have a solid spine, gripping the sides locks the slider which, once you have practiced, avoids movement errors.