If only you guys could scan that book and make the PDF available online. I would happily get my book binding stuff out and make a copy or three. Almost begs for a final resolution and a chance to be read.
We know know that you cannot compare two pendulums mounted that close; one on the wall the other standing on the floor next to it. The vibrations from each through the wall will affect the other. Actually both Huygens and Harrison already had encountered this effect. Two pendulum clocks have been shown to affect one another along 13 feet of concrete wall. Kater went slightly mad trying to construct a free pendulum clock, but only using mechanical means, in this he eventually failed, after struggling for many years.
Cool idea: if you're ever in London and fancy perusing the 'sad' object.. You could always visit the Royal Society library and ask Keith to retrieve it for you! :)
As someone who has built a galvanometer based on a torsion pendulum, I would love to read that manuscript. (I read about a lot of pendulum based electrical measurement equipment from the late 1800s) I wish they had a scan of it. I can't see myself making it across the pond anytime soon. Thanks for another great Objectivity!
Phil P, yes! Hello Internet needs to tackle the scanning and publication of this manuscript as a special project. I'm sure CGP Grey would allow an "Old Documents Publication Corner" :-) Whadda' you say Dr. Haran?
You say that now, when everything is still new and exciting for you. After a few years, you get to know the history and context of each artefact/document, and it loses a lot of its wonder. You will automatically start filtering stuff and have a more selective interest.
Keith is back!. Fabulous tie.Wait, they were measuring the local gravity with a pendulum whilst measuring time with a pendulum driven clock. That seems a bit redundant
I hope they weren't using pendulum clocks to time this, because then the clock would be affected just the same way as the pendulum, making it impossible to get any useful data out of the experiment.
Alistair Shaw The time period squared is directly proptional to the length of a pendulum. Such that the constant of proportionality is (4pi^2/g). So you measure the time period of an oscillation of a pendulum for multiple lengths in order to determine a value for g.
My problem with this is that the device used to measure the time period is itself a pendulum, making _its_ measurements dependent on what the local gravity is.
Just a bit curious: ALL the clocks shown today (live or in pictures) are ... Pendulum Clocks... therefore... if they are being used for timing purposes to reference Pendulums... in various places... how are those Clocks Regulated? Has someone carried about a Harrison Chronometer between these places, or have they been adjusted to local mean solar over the course of a year, or ... ???
Given how easy it is to put things out on the internet, and the nearly 8,000,000,000 there are in the world, you'd might find a few people interested enough in this research to download it. The data inside could be used for other thing than trying to measure a yard. Determining whether there's been any change in Earth's gravity at the locations where the measurements were originally taken to determine if there's been any change in the density of the underlying crust or mantle over time comes to mind.
Defining a yard based on the length of a pendulum which swings two seconds... in a pendulum clock which gets its timing from the pendulum. CIRCULAR LOGIC!
No, the clock gets its timing from the sun (or other astronomical observations). The separate pendulum is used so that its effective length can be easily measured.
If it was circular logic the yard would be undefined. Two seconds was already defined in terms of the sun, as opposed to our current Cesium definition. All pendulums of the same length should have the same period, but that is not perfectly true. (The amplitude of oscillation matters a little because the small angle approximation breaks down for larger amplitudes. Air resistance and gravity variations also matter.) The "unique" length that provided an oscillation of 2 seconds was defined to be the yard.
No, I believe he is the guy who sold the Germans on the idea that a hangover the morning after the gathering is mandatory. 😁 (In German "Kater" can mean male cat or hangover.)
Well, much the same thing was said about the writings of a teenage girl when her father tried to have them published. Frankly, (pun intended) I think Anne would have been horrified to learn her diary was going to be published and read by millions of people, beyond 70 years after they were written.
Would someone be able to shed some light on why Brady notes that the image through the telescope appears "upside down of course"? Was the ability to rotate the image from a telescope a later development?
A smple refractive telescopes will flip the image. There were upright refractive telescopes before this time but I'd guess the quality of the image wasn't as good, or cost was a factor. Considering they are just looking at a pendulum swing past a point it being upside doesn't matter.
This is science even though it was wrong he still tried to make constant. I respect you sir even your bones are dust your knowledge helped us forge the modern age
