- 2881 - GRAVITY - prove it travels at light speed? We can prove that light travels at 670,633,500 miles per hour. See my other reviews that cover LIGHT. This review, on GRAVITY, is about the speed of gravity. How do we prove that it to travels at the same light speed?
-
--------------------------- 2881 GRAVITY - prove it travels at light speed?
- Europe's “Galileo satellite navigation system” has now provided the physics community worldwide, the most accurate measurement ever made of how shifts in gravity alter the passing of time which is a key element of Einstein's Theory of General Relativity.
-
- The challenge here in physics is measuring with accuracy of the gravity-driven time dilation effect known as 'gravitational redshift.'
-
- The Galileo satellites carry the very high stabilities of onboard atomic clocks, the accuracies attainable in their orbit determination and the presence of laser-retro reflectors, which allow for the performance of independent and very precise orbit measurements from the ground are key to disentangle clock and orbit measurement errors.
-
- Galileo satellites 5 and 6 were delivered into faulty elongated orbits by a faulty Soyuz upper stage during their launch in 2014. This left them unable to view the entire Earth disc during the low point or perigee of their orbits, rendering their navigation payloads unusable, because they use an Earth sensor to center their signal beams.
-
- Subsequent orbital maneuvers succeeded in making their orbits more circular and their navigation payloads useable because they retained views of the entire Earth disc through each orbit. However their orbits remain elliptical compared to the rest of the Galileo constellation.
-
- These findings are the happy outcome of an unhappy accident: back in 2014 Galileo satellites 5 and 6 were stranded in incorrect orbits by a malfunctioning Soyuz upper stage, blocking their use for navigation. ESA flight controllers performed a daring salvage in space to raise the low points of the satellites' orbits and make them more circular.
-
- Once the satellites achieved views of the whole Earth disc their antennas could be locked on their earth antennas and their navigation payloads could be switched on. The satellites are today in use as part of Galileo search and rescue services while their integration as part of nominal Galileo operations is currently under final assessment by ESA and the European Commission.
-
- However, their orbits remain elliptical, with each satellite climbing and falling some 8,500 kilometers twice per day. It was these regular shifts in height, and therefore gravity levels, which made the satellites so valuable to gravity measurements.
-
- Albert Einstein predicted a century ago that time would pass more slowly close to a massive object, a finding that has since been verified experimentally several times, most significantly in 1976 when a hydrogen maser atomic clock on the Gravity Probe-A suborbital rocket was launched 10,000 kilometers into space, confirming Einstein's prediction to within 140 parts per million.
-
- Atomic clocks aboard navigation satellites must take into account the fact that they run faster up in orbit than down on the ground, amounting to a few tenths of a microsecond per day, which would result in navigation errors of around 10 kilometers daily, if uncorrected. Your location maps in navigation would be nearly worthless without these corrections.
-
- Periodic modulation of the gravitational redshift is created for one day's orbit of these eccentrically-orbiting Galileo satellites. Timekeeping of the passive hydrogen maser ,PHM, clocks aboard each Galileo are stable to one second in three million years and are kept from drifting by the worldwide Galileo ground constellation of atomic clocks.
-
- Observations focus then on the periods of time when the satellites were transmitting with PHM clocks and assess the quality of these precious data very carefully. Ongoing improvements in the processing and in particular in the modeling of the clocks might lead to even tightened results in the future.
-
- A key challenge over three years of work was to refine the gravitational redshift measurements by eliminating systematic effects such as clock error and orbital drift due to factors such as Earth's equatorial bulge, the influence of Earth's magnetic field, temperature variations, and, even the subtle but persistent push of sunlight itself, known as 'solar radiation pressure.'
-
- Careful and conservative modeling and control of these systematic errors has been essential, with stabilities down to four picoseconds over the 13 hours orbital period of the satellites; this is four millionth of one millionth of a second.
-
- It is not just the speed of gravity. We also had to learn how gravity affects the speed of light. Observations in astronomy are based on light emitted from stars and galaxies and, according to the general theory of relativity, the light will be affected by gravity.
-
- All interpretations in astronomy are based on the correctness of the theory of relatively, but it has never before been possible to test Einstein's theory of gravity on scales larger than the solar system.
-
- Now astrophysicists have managed to measure how the light is affected by gravity on its way out of galaxy clusters. The observations confirm these theoretical predictions. Observations of large distances in the universe are based on measurements of the redshift, which is a phenomenon where the wavelength of the light from distant galaxies is shifted more and more towards the red with greater distance.
-
- The redshift indicates how much the universe has expanded from when the light left until it was measured on Earth. Furthermore, according to Einstein's general theory of relativity, the light and thus the redshift is also affected by the gravity from large masses like galaxy clusters and causes a gravitational redshift of the light. But the gravitational influence of light has never before been measured on a cosmological scale.
-
- Measurements have been completed of light from galaxies in approximately 8,000 galaxy clusters. Galaxy clusters are accumulations of thousands of galaxies, held together by their own gravity. This gravity affects the light being sent out into space from the galaxies.
-
- The researchers have studied the galaxies lying in the middle of the galaxy clusters and those lying on the periphery and measured the wavelengths of the light. They measured small differences in the redshift of the galaxies and see that the light from galaxies in the middle of a cluster had to 'crawl' out through the gravitational field, while it was easier for the light from the outlying galaxies to emerge".
-
- Until now, the gravitational redshift has only been tested with experiments and observations in relation to distances her on Earth and in relation to the solar system. With this research the theory has been tested on a cosmological scale for the first time by analyzing galaxies in galaxy clusters in the distant universe.
-
- It is a large scale which is a factor 10^22 times greater (ten thousand billion billion times larger than the laboratory test). The observed data confirms Einstein’s general theory of relativity.
-
- The entire galaxy cluster's total mass gave the gravitational potential. By using the general theory of relativity calculations were made for the gravitational redshift for the different locations of the galaxies.
-
- The theoretical calculations of the gravitational redshift based on the general theory of relativity was in complete agreement with the astronomical observations. The analysis of observations of galaxy clusters show that the redshift of the light is proportionally offset in relation to the gravitational influence from the galaxy cluster's gravity, confirming the theory of relativity.
-
- In addition to the visible celestial bodies like stars, planets and galaxies, the universe consists of a large amount of matter, which researchers can work out that it must be there, but which cannot be observed as it neither emits nor reflects light.
-
- It is invisible and is therefore called ‘dark matter“. No one knows what dark matter is, but they know what the mass and thus the gravity must be. The new results for gravitational redshift do not change the researchers' modeling for the presence of dark matter.
-
- Another of the main components of the universe is ‘dark energy‘, which according to the theoretical models acts like a kind of vacuum that causes the expansion of the universe to accelerate.
-
- According to the calculations, which are based on Einstein's theory of relativity, dark energy constitutes 72 percent of the structure of the universe.
-
- Now the general theory of relativity has been tested on a cosmological scale and this confirms that the general theory of relativity works and that means that there is a strong indication for the presence of dark energy.
-
- The new gravitation results thus contribute a new piece of insight to the understanding of the hidden, dark universe and provide a greater understanding of the nature of the visible universe as well as our car navigation systems here on Earth.
-
- October 28, 2020 2881
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to whomever is interested. ----
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
--- to: ------ jamesdetrick@comcast.net ------ “Jim Detrick” -----------
--------------------- --- Friday, October 30, 2020 ---------------------------
No comments:
Post a Comment