- 3393 - EINSTEIN - relativity tested by pulsars? A 16-year long experiment to challenge Einstein's theory of general relativity. A pair of extreme stars called pulsars were studied through seven radio telescopes across the globe. This experiment reveals new relativistic effects that have now been observed for the first time.
--------------------- 3393 - EINSTEIN - relativity tested by pulsars?
- More than 100 years later, scientists around the world continue their efforts to find flaws in his theory. And , Einstein had pencil and paper with no experiments to even work with. Just his imagination and critical thinking.
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- His theory of General Relativity is not compatible with the other fundamental forces, described by quantum mechanics. It is therefore important to continue to place the most stringent tests upon general relativity as possible, to discover how and when the theory breaks down.
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- Finding any deviation from general relativity would constitute a major discovery that would open a window on new physics beyond our current theoretical understanding of the Universe.
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- A “pulsar’ is a highly magnetized rotating compact star that emits beams of electromagnetic radiation out of its magnetic poles. Pulsars weigh more than our sun but they are only about 15 miles across. They are incredibly dense objects that produce radio beams that sweep the sky like a lighthouse.
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- Astronomers studied a double pulsar that presents the most precise laboratory to test Einstein's theory. The double pulsar consists of two pulsars which orbit each other in just 147 minutes with velocities of about 1 million kilometers / hour.
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- One pulsar is spinning very fast, about 44 times a second. The companion is young and has a rotation period of 2.8 seconds. It is their motion around each other which can be used as a near perfect gravity laboratory.
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- Astronomers conducted a 16-year long experiment to challenge Einstein’s theory of general relativity. This was a system of compact stars to test gravity theories in the presence of very strong gravitational fields. The energy carried by gravitational waves was measured with a precision that is 25 times better than previous measurements.
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- The double pulsar system presented astronomers with the only known instance of two cosmic clocks which allow precise measurement of the structure and evolution of an intense gravitational field.
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- They followed the propagation of radio photons emitted from a cosmic lighthouse, which is a pulsar, and tracked their motion in the strong gravitational field of a companion pulsar.
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- Astronomers could see for the first time how the light is not only delayed due to a strong curvature of spacetime around the companion, but also that the light is deflected by a small angle of 0.04 degrees.
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- These fast orbital motion of compact objects are about 30 percent more massive than the Sun but only about 24 km across. Their precision measurements allows them to measure the effect of "time dilation" that makes clocks run slower in gravitational fields.
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- They needed to take Einstein's famous equation E = mc^2 into account when considering the effect of the electromagnetic radiation emitted by the fast-spinning pulsar on the orbital motion. This radiation corresponds to a mass loss of 8 million tons per second!
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- The researchers also measured with a precision of 1 part in a million, that the orbit changes its orientation, a relativistic effect also well known from the orbit of Mercury, but here 140,000 times stronger.
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- This level of precision also needed to consider the impact of the pulsar's rotation on the surrounding spacetime, which is "dragged along" with the spinning pulsar. This is the “Lense-Thirring effect” or “frame-dragging‘.
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- The technique of pulsar timing was combined with careful interferometer measurements of the system to determine its distance with high resolution imaging, resulting in a value of 2,400 light years with only 8 percent error margin.
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- In addition to pulsar timing and interferometer measurements also the information gained from effects due to the interstellar medium were carefully taken into account. The calculations was involving physics from many different areas, nuclear physics, gravity, interstellar medium, plasma physics and more.
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- For more than a hundred years have passed since Einstein formalized his theory of General Relativity, the geometric theory of gravitation that revolutionized our understanding of the Universe.
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- Any indication of physics beyond Relativity would open new windows onto the Universe and help resolve some of the deepest mysteries about the cosmos
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- Using seven radio telescopes from across the world, observing a unique pair of pulsars for 16 years observed effects predicted by Relativity for the first time, and with an accuracy of at least 99.99%!
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- “Radio pulsars” are a special class of rapidly rotating, highly magnetized neutron stars. These super-dense objects emit powerful radio beams from their poles that when combined with their rapid rotation create a strobbing effect that resembles a lighthouse.
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- This rotating system is the only radio pulsar binary ever observed and was discovered in 2003. The two pulsars that make up this system have rapid rotations, 44 times a second , and once every 2.8 seconds, and orbit each other with a period of just 147 minutes. While they are about 30% more massive than the Sun, they measure only about 15 miles in diameter. This creates their extreme gravitational pull and intense magnetic fields.
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- The observatories covered different parts of the radio spectrum, ranging from 334 MHz and 700 MHz to 1300 – 1700 MHz, 1484 MHz, and 2520 MHz. They were able to see how photons coming from this binary pulsar were affected by its strong gravitational pull.
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- By following the propagation of radio photons emitted from a cosmic lighthouse, a pulsar, and track their motion in the strong gravitational field of a companion pulsar. Astronomers for the first time had the light that is not only delayed due to a strong curvature of spacetime around the companion, but also that the light is deflected by a small angle of 0.04 degrees.
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- The fast orbital motion of compact objects like these allowed astronomers to test seven different predictions of Relativity. These include gravitational waves, light propagation (“Shapiro delay and light bending), time dilation, mass-energy equivalence (E=mc2), and what effect the electromagnetic radiation has on the pulsar’s orbital motion.
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- We have reached a level of precision that is unprecedented. Future experiments with even bigger telescopes can and will go still further.
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January 3, 2022 EINSTEIN - relativity tested by pulsars? 3386
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