bottomlesspit
Member
Interesting read.... prompts more googling...
. The Cornish hut that gave rise to sea level benchmark
. The Cornish hut that gave rise to sea level benchmark
I'm left wondering whether that surface is flat or curved and if curved whether its curvature varies with the proximity of large masses or is fairy constant and equal to the curvature of the earth's surface."local gravitational equipotential surface "! I am not sure you should be using that sort of language like that on the ECF!
I'm left wondering whether that surface is flat or curved and if curved whether its curvature varies with the proximity of large masses or is fairy constant and equal to the curvature of the earth's surface.
Peter.
Would you prefer it if I said Geoid? That's the local gravitational equipotential surface at mean sea-level. Some quite nice pictures of EGM96 (I think that's the most recent) here: Geoid - Wikipedia"local gravitational equipotential surface "! I am not sure you should be using that sort of language like that on the ECF!
I should have said that SMALL variations are caused by things like mountains (see the Schiehallion Experiment), and somewhat larger variations by deeper geology. But the major influences are much deeper in the Earth. Basically, the greater the extent of an anomaly, the deeper the cause. Deep ocean bathymetry can be derived from very precise measurement of the sea-level (sorry, no simple explanation, but see bathymetry by inversion of satellite altimetry - Google Search and take your pick!). I am proud to say that I was part of this (Greenland Gravitational Experiment), and my part was to derive the topography of the rock beneath the ice to account for its effect on the gravitational force being measured.I'm left wondering whether that surface is flat or curved and if curved whether its curvature varies with the proximity of large masses or is fairy constant and equal to the curvature of the earth's surface.
Peter.
Would you prefer it if I said Geoid?
PS, I'm assuming that people on here aren't NFN!
Normal for Norfolk?
i AP,I should have said that SMALL variations are caused by things like mountains (see the Schiehallion Experiment), and somewhat larger variations by deeper geology. But the major influences are much deeper in the Earth. Basically, the greater the extent of an anomaly, the deeper the cause. Deep ocean bathymetry can be derived from very precise measurement of the sea-level (sorry, no simple explanation, but see bathymetry by inversion of satellite altimetry - Google Search and take your pick!). I am proud to say that I was part of this (Greenland Gravitational Experiment), and my part was to derive the topography of the rock beneath the ice to account for its effect on the gravitational force being measured.
That would be an ecumenical matter.i AP,
Thank you for that explanation, Was the influence of these geological anomalies on gravity best explained by Newtonian, Einsteinian or quantum mechanics?
Peter.
Normal for Norfolk?
Newtonian. Because a) the effects are on timescales and velocities too low for relativistic effects, b) too large a scale for quantum mechanical effects and c) the Schiehallion Experiment took place to verify predictions of Newtonian theory.i AP,
Thank you for that explanation, Was the influence of these geological anomalies on gravity best explained by Newtonian, Einsteinian or quantum mechanics?
Peter.
Does NFN include putting the Newlyn Datum in the East Coast Forum?