- #1

- 75

- 0

I don't mean like log10(100)=2, that's obvious I mean like log10(20)~1.301, how does one figure that out, I asked my math teacher and he couldn't tell me..?

By the way, sorry I don't know how to make subscripts, and thanks.

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter Helical
- Start date

- #1

- 75

- 0

I don't mean like log10(100)=2, that's obvious I mean like log10(20)~1.301, how does one figure that out, I asked my math teacher and he couldn't tell me..?

By the way, sorry I don't know how to make subscripts, and thanks.

- #2

berkeman

Mentor

- 62,257

- 13,020

My guess is that they used slide rules. Have you wiki'ed slide rules yet?

- #3

- 1,074

- 1

My guess is that they used slide rules. Have you wiki'ed slide rules yet?

Aren't slide rules based on logarithms? So wouldn't using them to calculate logs be rather circular?

- #4

Integral

Staff Emeritus

Science Advisor

Gold Member

- 7,224

- 63

- #5

- 75

- 0

But how were the tables figured out?

- #6

Integral

Staff Emeritus

Science Advisor

Gold Member

- 7,224

- 63

You asked "how people" calculated logs.

I have told you how PEOPLE did it.

I suspect that that table creators used something like a Taylor series polynomial, and lots of hand work.

EDIT:http://mathforum.org/library/drmath/view/52469.html"

I have told you how PEOPLE did it.

I suspect that that table creators used something like a Taylor series polynomial, and lots of hand work.

EDIT:http://mathforum.org/library/drmath/view/52469.html"

Last edited by a moderator:

- #7

- 13,194

- 764

I don't mean like log10(100)=2, that's obvious I mean like log10(20)~1.301, how does one figure that out, I asked my math teacher and he couldn't tell me..?

By the way, sorry I don't know how to make subscripts, and thanks.

Any logarithm can be computed by hand, using the Taylor series for [itex] \ln(1\pm x) [/itex] which converges for any real [itex] x<1 [/itex] and the logarithm's properties.

For example

[tex] \ln 243.5 =\ln 0.2435 + 3 \ln 10=\ln 0.2435 + 3 \ln 2 +3\ln 5=\ln 0.2435 + 12 \ln 2+3\ln 5/8 [/tex]

- #8

Gib Z

Homework Helper

- 3,346

- 6

- #9

HallsofIvy

Science Advisor

Homework Helper

- 41,847

- 969

- #10

- 123

- 0

John Napier, 1550 and 1617, is credited with the discovery of logarithms

http://johnnapier.com/table_of_logarithms_001.htm"

http://johnnapier.com/table_of_logarithms_001.htm"

Last edited by a moderator:

- #11

Integral

Staff Emeritus

Science Advisor

Gold Member

- 7,224

- 63

The story I heard (Feynman?) is that they had a number crunching program written, but, for reasons I don't recall, the computer was not yet working. So they took the program which consisted of a stack of punch cards each with a single instruction (Some may recall these, I do) and passed it out to a number of people, probably with adding machines, each person did the calculation on their card and passed the result on to the next person.

A human computer.

- #12

arildno

Science Advisor

Homework Helper

Gold Member

Dearly Missed

- 10,025

- 135

The story I heard (Feynman?) is that they had a number crunching program written, but, for reasons I don't recall, the computer was not yet working. So they took the program which consisted of a stack of punch cards each with a single instruction (Some may recall these, I do) and passed it out to a number of people, probably with adding machines, each person did the calculation on their card and passed the result on to the next person.

A human computer.

Couldn't they just have plugged those numbers into von Neumann?

That would have been simpler, faster and more reliable.

But perhaps more expensive..

- #13

- 419

- 14

yeah, i have also read that von Neumann memorized the log tables. but how did he do it?

Share: