For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.
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Tomi Engdahl says:
A Century Ago, Einstein’s General Relativity Solved an Orbital Measurement Discrepancy
http://www.eetimes.com/author.asp?section_id=36&doc_id=1328887&
The now well-known theory was used to explain a tiny discrepancy between Newtonian equations of Mercury’s orbit versus observed data.
The year 2016 is the centennial of the second of Albert Einstein’s relativity papers. In 1905, he published his paper on what we now call Special Relativity, which accounted for the properties of bodies moving at constant velocity
Eleven years later, Einstein drastically increased the envelope of relativity’s reach with the General Theory which encompassed bodies which were accelerating, rather than restricted solely to constant velocity. This theory was far more difficult to prove than the special theory, for many reasons.
What Einstein did was both significant and impressive: he used general relativity equations to calculate what the variation in the observed motion of Mercury would be, and showed that the entire discrepancy could be explained by it; thus, planet Vulcan was unneeded.
Tomi Engdahl says:
Related posting: http://www.epanorama.net/newepa/2015/12/01/gravitational-wave-mission-blasts-off-tomorrow/
Tomi Engdahl says:
About Those Gravitational Waves
http://hackaday.com/2016/02/17/about-those-gravitational-waves/
It was the year of 1687 when Issac Newton published “The Principia“, which revealed the first mathematical description of gravity. Newton’s laws of motion along with his description of gravity laid before the world a revolutionary concept that could be used to describe everything from the motions of heavenly bodies to a falling apple. Newton would remain the unequivocal king of gravity for the next several hundred years. But that would all change at the dawn of the 20th century when a young man working at a Swiss patent office began to ask some profound questions. Einstein had come to the conclusion that Newtonian physics was not adequate to describe the findings of the emerging electromagnetic field theories. In 1905, he published a paper entitled “On the Electrodynamics of Moving Bodies” which corrects Newton’s laws so they work when describing the motions of objects near the speed of light. This new description became known as Special Relativity.
Newton’s laws describes the motions of the planets perfectly, but he never was able to say exactly what gravity was, where it came from, or what it was made of.
Einstein realized that all physical laws were true despite their frame of reference.
Gravitational Waves
Now we know what would happen if the Sun were to suddenly vanish. The curvature of space-time caused by the Sun would spring back and ripple outward. It would send a gravitational wave moving at the speed of light barreling towards the planets. Each planet would keep moving along steadily in their orbits following the still present curvature from the Sun, blissfully ignorant of the incoming doom. Once the wave hits, the curvature is gone. Without the curved space-time to follow, the planets would follow Newtonian mechanics and head out into deep space.
This is all hypothetical of course, and so was the idea of a gravitational wave. Einstein had predicted them, but thought they would be too small to measure here on Earth. This all changed just a few days ago, when two facilities in the US managed to record the merging of two black holes that happened a billion years ago. The merge set off a cascade of gravitational waves, and we were listening.
Tomi Engdahl says:
Einstein’s gravitational waves: what are they, and what does their discovery mean?
http://www.abc.net.au/news/2016-02-11/einstein's-gravitational-waves:-what-do-they-mean/7159238
Scientists have finally found direct evidence of gravitational waves — a feat Albert Einstein never thought we would manage. But what does this discovery actually mean?
For starters, it opens a new field of astronomy — gravitational wave astronomy — that will let us see everything from the heart of a black hole, to the moments after the Big Bang.
Tomi Engdahl says:
LIGO Laboratory mathematics: detecting gravitational waves
http://www.edn.com/electronics-blogs/math-is/4441420/LIGO-Laboratory-mathematics–detecting-gravitational-waves?_mc=NL_EDN_EDT_EDN_analog_20160218&cid=NL_EDN_EDT_EDN_analog_20160218&elqTrackId=db17e3555a4f48d5a89867f1b9c245a0&elq=585f63ce10014054ba3001eee3f28b1a&elqaid=30884&elqat=1&elqCampaignId=27023
When I first heard of gravitational waves being detected a billion light years away from Earth—I must say that I was quite skeptical. A NY Times article explained the event very well and I did some more research because I thought, “What if an alien just coughed or sneezed (do they have noses or mouths?), or there was a minor explosion on some planet or star in a nearby galaxy or maybe a major seismic event on a nearby world?” Here is what I found out which amazed me and piqued my interest in the incredible technology that detected two black holes colliding around 1.2 billion years ago.
The state-of-the-art instrument that sensed this event is called LIGO (Laser Interferometer Gravitational-Wave Observatory), the largest gravitational wave observatory in the world. It is constructed with two huge laser interferometers in the shape of an L, separated by more than 3,000 kilometers (one is located in Washington State and the other in Louisiana). This system uses the physical properties of light and space in order to detect and study the origins of gravitational waves.
Gravitational Waves Detected, Confirming Einstein’s Theory
http://www.nytimes.com/2016/02/12/science/ligo-gravitational-waves-black-holes-einstein.html?emc=edit_th_20160212&nl=todaysheadlines&nlid=74307160&_r=0
Tomi Engdahl says:
The age of gravitational wave astronomy has begun
http://www.edn.com/electronics-blogs/test-voices/4441489/The-age-of-gravitational-wave-astronomy-has-begun?_mc=NL_EDN_EDT_EDN_today_20160301&cid=NL_EDN_EDT_EDN_today_20160301&elqTrackId=27ce05f478b44060a21dd7e29d5c35f9&elq=9ecaebaecbc244f9973d4c37df576fe0&elqaid=31095&elqat=1&elqCampaignId=27188
The LIGO (Laser Interferometer Gravitational-Wave Observatory), is the most precise instrument ever built. It’s basically a Michelson interferometer with two, 4-km long arms at right angles, shown in Figure 1. A frequency stabilized, 1.06 micron, 220 W laser bounces 400 times back and forth between the mirrors before recombining with the beam in the other arm.
One challenge is to isolate mechanical vibrations of the mirrors from environmental and thermal noise low enough to see motion that is smaller than a millionth the diameter of a proton. A combined passive and active suspension system isolates each of the mirrors.
LIGO consists of two identical interferometers, one in Hanford, WA and the other in Livingston, LA. While a local seismic disturbance would be seen at one location and not the other, a gravitational wave disturbance in space-time would be seen by both detectors, delayed by up to 10 ms, the light travel time between the two observatories.
“In that brief, final flash of intense gravitational radiation, as much as three solar masses were converted into pure gravitational energy,”
“The peak gravitational radiation had more power than 50 times the total power emitted by all the power output of all stars in the universe. It was a violent storm in space-time and we heard the ripples passing by the Earth.”
“This detection is the beginning of a new era: The field of gravitational wave astronomy is now a reality,” González concluded.
Tomi Engdahl says:
Resume of Albert Einstein By Physicist & 30 Best Quotes
http://godofsmile.com/resume-of-albert-einstein-scientist-physicist-1879-1955/
Tomi Engdahl says:
Detecting gravitational waves: Why did it take so long?
http://www.edn.com/electronics-blogs/all-things-measured/4441504/Detecting-gravitational-waves–Why-did-it-take-so-long-?_mc=NL_EDN_EDT_EDN_today_20160303&cid=NL_EDN_EDT_EDN_today_20160303&elqTrackId=650fdf456746469280bb134e5f23778b&elq=dbfa4215f1d04cbcac2e5d7095349c28&elqaid=31145&elqat=1&elqCampaignId=27227
Recently, the scientific community was rocked by the announcement of the detection of gravitational waves as predicted by Albert Einstein. In November 1915, Einstein presented a series of lectures before the Prussian Academy of Sciences on his General Theory of Relativity, in which he contended that space and time form a continuum that is influenced (distorted/warped) by anything possessing mass. The effect of that influence he declared is gravity.
Einstein’s final lecture ended with his introduction of a series of equation that replaced Newton’s law of gravity known as Einstein’s Field Equations. These ten equations describe the fundamental interaction of gravitation as a result of space time being influenced by mass. Gravitational waves, which Einstein proposed in 1916, are something of a corollary to his General Theory of Relativity.
The detection of gravitational waves was made by the LIGO (Laser Interferometer Gravitational Wave Observatory) facilities in Livingston, Louisiana and in Richland, Washington on 14 September 2015, at 9:50:45 universal time (4:50 a.m. in Louisiana and 2:50 a.m. in Washington).
In layman’s terms, when a gravitational wave passes an observer, that observer will find their space time immediacy distorted to some degree. LIGO researchers detected a gravitational wave that stretched space by 1 X 10-21, making the entire Earth expand and contract by 1/100,000 of a nanometer (one nanometer is one billionth of a meter equivalent to 3.937 X 10-8 inch).
Why did it take 100 years from the time Einstein predicted the existence of gravitational waves as a consequence of his theory of general relativity to the recent announcement of their detection? Read on to appreciate what it takes to measure this elusive phenomena.
When I heard about the LIGO announcement, I was immediately curious as to what technologies were used in detecting gravitational waves. From my previous readings on space-time continuum, I knew gravitational waves are very difficult to detect and measure, owning to their extremely small amplitudes requiring very sensitive, state of the art detectors. Not only must these detectors be very sensitive, but they also must be able to cancel out other sources of noise that can easily overwhelm them.
The two LIGO facilities are located 3000 km (1864 mi.) apart and operated in unison as a single observatory. Having two separate facilities spaced far apart allows detected gravitational waves to be triangulated in order to determine their origin.
Each LIGO facility has two tunnels known as light storage arms that are 4 km (2.485 mi.) long. The arms are so long that the curvature of the Earth must be taken into account in designing the arms (there is a 1 m vertical drop over the 4 km length of each arm).
At the heart of LIGO’s gravitational wave detection system are state-of-the-art Michelson interferometers. A Michelson interferometer produces interference fringes by splitting a beam of light into two paths; one path has a fixed length of travel, the other path susceptible to length variations. When the reflected beams are brought back together, an interference pattern is created symptomatic of the length of travel difference between the two beams. The LICO detection system uses a pre-stabilized laser emitting a beam with a power of up to 200 W that passes through a beam splitter, which splits the beams into two paths, one for each of the light storage arms.
This incredible measurement capability is the equivalent of measuring the distance to the nearest star to within the width of a human hair (Proxima Centauri, the closest star to us is 39.9 × 1015 m away).
Tomi Engdahl says:
How the Bits of Quantum Gravity Can Buzz
By
THOMAS LEWTON
July 23, 2020
https://www.quantamagazine.org/gravitons-revealed-in-the-noise-of-gravitational-waves-20200723/
New calculations show how hypothetical particles called gravitons would give rise to a special kind of noise.
If gravity plays by the rules of quantum mechanics, particles called gravitons should gingerly jostle ordinary objects.