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--------------------------- 1870 - Is Gravity a Quantum Force?
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- “There is plenty of room at the bottom”. Meaning when you get to the smallest microscopic structures there is a wide world of diversity and opportunity.
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- Your eye makes visible 10^-3 meters ( a tenth of a millimeter). Using our best technology instruments we can resolve down to 10^-19 meters, that is the wavelength of a proton.
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- The quantum effects of gravity are estimated to be at 10^-35 meters. This length has been given the name “ Planck Length” We have 16 more orders of magnitude to get down to this resolution. From the above paragraph you can see it took 400 years to get the first 15 orders of higher magnitude resolution. How long will it take to get to the next 16 orders of magnitude?
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- The name given to this undiscovered granular gravity is “ gravitons”, a single quantum of a gravitational field.
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- Direct detection of these smallest of small particles may be impossible. But, indirect detection may still work for us to learn more.
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- How to test for Gravitons?
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- There is a technique called “ Lorentz-Invariance” that is evidence of a violation of symmetry. Other tests look for the “ weak field limit of quantum gravity”. In the early Universe quantum fluctuations of space-time would lead to temperature fluctuations appearing in matter. Today we can detect these temperature variations in the Cosmic Microwave Background radiation. Temperature variations of only 1 part in 100,000 around an average temperature of 2.73 Kelvin.
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- LIGO has detected gravity waves for the first time in 2016. ( See Review # 1858 ). Maybe now it is possible to detect these primordial gravitational waves in the CMB. This could become evidence of quantized gravity.
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- The search is on to prove if gravity truly is a “ quantum force”.
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- Our experience is that space-time is a continuous object, without gaps of discontinuities. However, quantum Gravity would have a “ texture”, a granularity at the tiny scale of 10^-35 meters. A texture of a variable mesh of solids and voids, a “ complex foam”.
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- This concept of smallest scale granularity runs contrary to Einstein’s Theory of Relativity. Distance shortens as motion approaches the speed of light and time slows. But, what happens to the shortest unit of measurement in space. By definition it can not shorten even traveling at the speed of light where matter shortens and time stops.
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- This idea is called a violation of the “ Lorentz Invariance”. String Field Theory and Causal Set Theory are trying to find scenarios that are compatible with both Granularity and Special Relativity. The goal is to define the boundary, a transition zone, where space-time becomes “ granular” and physics becomes “ non-local”.
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- The Lorentz Invariance is a little too deep for me to explain. When theories go too deep try something else, that is easier. “ Is the speed of gravity the same as the speed of light?”
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- The Sun is 93,000,000 miles away and it takes light 8 minutes and 20 seconds to reach us. Does gravity get here at the same time as sunlight? Is gravity too moving at 186,282 miles per second? Isaac Newton thought gravity was instantaneous. Einstein thought otherwise.
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- If the Sun instantly winked out of existence would Earth instantly fly off in a straight line, or, would we have to wait another 8 minutes?
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- It is not the mass of the Sun that determines this, it is the mass that is curving space-time that determines this. So, how long will the curvature of gravity last? How fast would space-time go from curvature to flat? Recently discovered, September 2015, and announced, February 2016, gravitational waves were detected by LIGO, Laser Interferometer Gravity-wave Observatory. The snapping motion of the Sun disappearing would send very large gravity ripples propagating across the Universe (at the speed of light?) ( See Review # for more about LIGO)
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- Since gravitational waves are massless., like light photons, with finite energy levels they must move at the speed of light.
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-The other variable for us on Earth is that each planet’s velocity affects how it experiences gravity. However, the two effects of changes in the gravitational field and velocity-dependent interactions observationally nearly cancel out. If something moves at a constant velocity in a constant gravitational field there is no observable affect of time difference of the speed of gravity.
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- To see this affect we need to observe “ massive objects” in “ close orbits” like two Neutron stars. One being a “ pulsar” that allows the time change of orbits to be precisely measured. This measurement was done in 1980 concluding that light and gravity have the same speed to within a 0.2% measurement error. ( the Hulse-Taylor binary).
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- In 2002 Earth , Jupiter, and a radio Quasar lined up. The gravitational bending of Jupiter moving between Earth and the Quasar allowed a measurement of the speed of gravity. The conclusion was gravity’s speed was between 255,000,000 and 381,000,000 meters per second ( The speed of light is 299,792,458 meters per second).
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- February 2016 LIGO concluded that gravity waves could be measured with two observatories located in Washington State and Louisiana. But, the inability to accurately triangulate from where these waves originated, an accurate gravity speed could not be calculated. Ballpark estimates supported earlier results but precision was not good enough to improve on these previous measurements.
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- Now that gravity waves can be detected more measurements are sure to follow. The speed of gravity waves will be accurately measured one of these days. What do you want to bet Albert Einstein was right 100 years ago, light and gravity travel at the same speed?
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- Albert’s ideas are always being tested. Space-time is curved by the presence of matter, energy and momentum. Another attempt to prove this is happening is occurring on a satellite named “Microscope”.
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- The satellite contains two different metals, one titanium, the other platinum-rhodium alloy. Both together in free-fall orbit. Will both move identically. If there is any difference detected then Einstein’s theory needs some modification.
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- Given the theory of gravity and the theory of Quantum Mechanics it is evident that us humans have not yet grasped all there is to grasp about the Universe. Learning something new will propel humanity to the next level. Stay tuned, an announcement will be made shortly.
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- Request these Reviews to learn more:
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- #1858 - Gravity, LIGO, and Gravity Waves. Plus 10 other references about gravity.
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----- 707-536-3272 ---------------- Wednesday, May 11, 2016 -----
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