Gravity and Temperature, gravity and pressure
Shawn,
What I am saying is that the energy density of the radiation field of the earth, which you can map by mapping the temperature is just “gravitational field stuff”. The magnetic field of the earth which you can convert to magnetic energy density is also made of “gravitational field stuff”. The gravitational field of the earth is “gravitational field stuff”.
They are all made of the same material. The only reason we call them different things is the same reason “magnetism” and “electricity” were considered different things.
I am just adding “gravity” to the bottom of the electromagnetic spectrum, and clarifying exactly what sensors are picking up.
So the noise at the gravimeter (good stuff about the character and composition of the earth interior and the universe too) – whether you are using a “gravimeter” or “electric field sensor” or “magnetic sensor” is only one field made of “gravitational field stuff”.
And because they share the same energy density and that is limited to C^2 (the speed of light squared in Joules/kg which is the potential in our part of the universe). If you increase the energy density, you change the rate of clocks and all processes. If you increase the energy density in a finite volume of space you get “gravitational waves”. If you change it at “optical” or “infrared” or “x-ray” or “gamma ray” frequencies you get “electromagnetic waves”.
But there is only one vacuum — made up of “gravitational field stuff”. If you have a good suggestion for a name, I am happy. Dirac described it, and some people call it the “Dirac sea”. Other people call it “the physical vacuum”. Other call it the “ether”. But the single property they all have is they are fields that have value in every tiny or large volume of the universe.
The temperature variations in the atmosphere and inside the earth mean different parts of the atmosphere and inside the earth are at different temperatures. And the slow signals depend on the thermal conductivity and the movement of materials. But the high frequency parts depend on the time dependent temperature changes and that depends on the gradients of the Stefan-Boltzmann temperature flux. Which is a T^4 dependence.
For “your” gravimeter, the variations in the temperature of parcels in the atmosphere gives a signal at the detectors that is transmitted as “electromagnetic gravitational stuff”. The earth below you is not changing temperature fast, except in small locations. So “temperature” processes will tell you a lot about the atmosphere. The “magnetic” variations are bound by the gravitational field.
You could say that the gravitational field is like an atmosphere made up of tiny atoms, tiny bundles of energy. I was describing to my son yesterday. I told him to visualize a cloud of red particles in the shape of a cube. Then another cloud of blue particles also in a cube. Then “push them together”. There is no resistance at all. They intersect without touching (for the most part). Imagine a cloud of red magnetic field rushing toward you. Most of it goes right through. But there is no difference between red and blue particles, between magnetic and gravitational – except the 3D spectrum (3D FFT) of the source.
My excitement is that it gives me a way, finally, to link ALL the sensor networks together with gravity as the basis. A magnetic network picks up the gravitational changes. An electric field network picks up gravitational field changes. Most particularly they all have sun and moon tidal variations that can be pulled out as the largest slow changes embedded in all the network, and the conversions between fields are based on fundamental constants and relations from Maxwells equations and special relativity and gravitational groups.
I dearly wish that company you want to buy your gravimeter from would let me change their instrument. it has many good pieces. But i think it is easier to just make a new gravimeter from scratch – except many of the parts are now available off the shelf. The “atom interferometer” sensors are good resolution, but they are all using photons for querying, control and sensing. The “atomic force” (I should call it “atomic scale”) sensors can measure down to fractions of an Angstrom. They mostly use photon lasers for querying and monitoring.
The “electron interferometer” methods are the finest and most universal, but they get called lots of different things. When people do “electronics” they are moving electrons. it is only now that the energy resolution is fine enough that they can pick up the variations because of alignment of the electron magnetic moments, and it is routine to deal with magnetic dipole bound electron pairs for superconductivity and much of chemistry.
So while lasers are often attractive, they can get really expensive. That Mount Etna atom interferometer gravimeter. It is using metal vapors as the target masses, exciting them with lasers, waiting for them to fall, and then querying with lasers. They mark them at a certain height or location then test them at a different location and the distance and speed and acceleration are in the electronics of the photodetectors after they have been amplified and ADCed. (just made up that word) “to ADC something” “to analog to digital measure something”.
Yes, it needs permanent networks – because the slow variations over decades and years and months cannot be predicted that well yet. The one per second superconducting gravimeter signal is very very very predictable. But that is only because the “gravitational field stuff” diffuses at the speed of light and gravity. It can flow faster, and in shock waves and travelling waves it can go almost any speed. But for everyday things if you are at a point on the earth you get the exact Newtonian acceleration at the station that comes to you at the speed of light and gravity. And it is very much in equilibrium.
But go to 40 sample per second and higher and the region sampled in 1/40 second is the whole earth. At 10,000 sps the gravitational potential field sources that are going to be possible or likely, are going to be no further than C/10000 or 30 Kilometers. To image the atmosphere (a high value target because the global climate models, regional and local atmospheric models need to be calibrated in near real time over very long period). [I will see if I can run the climate models and use the gravitational field to work out the pattern. ]
10 meter cubes would be a good place to start. But the ADCs are now in Gsps (Giga samples per second).
If you subtract out the sun moon signal from the gravimeter – its residual correlates closely with atmospheric temperature and pressure field.
I started checking where the pressure variation comes from. It is partly from the pressure variation are also temperature variations.
Remember PV = nRT? The pressure “admittance” is -0.356 microGal/milliBar from this old paper. That is 28.09 Pascal/(nm/s2). Or 0.0356 (nm/s2)/Pascal. And the normal variations over short periods are 10 Pascal to 100 Pascal. So these show up at about 1 nm/s2 level. The radiation field effects from temperature look identical to gravity. The pressure effects are atoms and molecules. Need some time to do the numbers, and check the sensors. But it is the right order of magnitude. i will try to think of a good test. I want to upgrade ALL the meteorology sensors to three axis, high sampling rate. Then the pressure changes can be tracked at high tempos, high sampling rates. I have been teasing out the properties of the microbarograph networks, and trying to find microphone networks, and doing a few experiments myself. The detectable sound pressure level is 20 microPascal for humans. That can be a 5.71 mm/second “wind” or 7089.8 nanoTesla or 183 nm/s2. So humans probably cannot hear normal magnetic and gravitational changes. LOL!
Two years of continuous measurements of tidal and nontidal variations of gravity in Boulder, Colorado by Tonie M. van Dam and Olivier Francis – NOAA/NGS and CIRES, University of Colorado, Boulder
It is fun when some of the pieces fit together. I work on these things for decades almost continuously, and never think too much if I have to take an extra ten or 20 years to figure something out. But I am getting older and seeing the end a bit closer, so I don’t have many decades to work with. Either I have to get a lot smarter, or a lot faster, or add a LOT of external memory, or get anyone to help.
Reading over this, I see that the pressure in the atmosphere can be corrected a bit.
Richard
