-
-
-------- - 1858 - Gravity, LIGO, and Gravity Waves.
-
- Detecting gravity waves is no small feat. Gravity by far is the weakest force we know. The other 3 forces electromagnetism, the weak, and strong nuclear forces are millions of times stronger. You can easily pick a book up off the ground with the mass and gravity of the entire Earth pulling the other direction.
-
- Gravity is unique in also always pulling in one direction, it is only an attractive force. There is no “negative” gravity. Unless it could be a form of Dark Energy?
-
- The electric force between the electron and the proton inside the atom is a quintillion times stronger than gravity. (10^ 30). That is a 1 followed by 30 zeros. Gravity is so weak science does not know exactly how weak it is?
- In addition to our inability to measure the force of gravity it is better understood as not a force at all but a natural path of mass following the warped fabric of space-time.
-
- Gravity and weight are not the same thing. Astronauts in the Space Station say they are floating in “ zero gravity”. That is not really true. The force of gravity is there , about 90% the force felt on the surface of Earth. What astronauts feel is they are constantly free-falling, as gravity pulls them around the Earth at a constant velocity making it feel like “zero gravity”.
-
- If you use a bathroom scale in an elevator your “weight” will fluctuate as the elevator accelerates and decelerates while the gravitational force remains the same.
-
- Gravity makes waves that travel at the speed of light. This phenomenon was predicted in Einstein’s Theory of Relativity. Two large masses in binary orbit will slowly get closer together in their orbit as gravity waves carry energy away. Even the Earth is orbiting ever closer to the Sun, but, in this case the mass is so small and the energy loss too tiny to be noticed.
-
- Astronomers have had indirect evidence of gravity waves for 40 years. But, gravity waves were not directly detected until this year (2015). LIGO, the Interferometer Gravitational-Wave Observatory , detected bursts of gravity waves coming from the collision of 2 Blackholes 1.3 billion lightyears away.
-
- Gravity waves traveling at the speed of light means that if the Sun disappeared instantaneously we would not realize it for 8 minutes.
-
- The other three forces have defined quantum force carrier particles , photons, Gluons, and Bosons. However, no force particle has been discovered for gravity. Quantum Theory has given the undiscovered particle a name, the “graviton“.
-
- Loop Quantum Gravity theory proposes that space-time itself is particle-like at the smallest dimensions.
-
- String Theory uses gravitons described as vibrations of strings coiled up in extra dimensions.
-
- However, Quantum Theory has yet to be successful in describing the microscopic behavior of gravity. Stay tuned.
-
- If gravity has force-carrier-like gravitons they would likely be massless like photons. But, an extremely tiny mass can not be ruled out. Stay tuned.
-
- Even though the force of gravity is weak it would become stronger when masses become larger or closer together. Theoretically, it does not reach the strength of the other forces until it reaches distance of Plank Lengths, 1.6*10-35 meters, many times smaller than the nucleus of an atom.
-
- From the smallest scales to the largest scales gravity still serves us some mysteries.
-
- A breakthrough was announced this year (2016) when LIGO detected the merger of two Blackholes that violently shook the fabric of space-time and sent a burst of vibrations traveling to us, and through us.
-
- LIGO detected the ripples in two “L-shaped” mile long detectors in Louisiana and Washington State. This achievement introduces a new field of study in gravitational-wave astronomy.
-
- In addition to the study of Blackholes this technique will allow cosmological distance measurements to be made more accurately.
-
- In 1974 radio astronomers studying a pair of Neutron stars orbiting each other observed indirect evidence of gravity wave radiation. One was a “Pulsar” star that allowed measurements of the loss of orbital energy as the stars inward spiral exactly matched the math in Einstein’s Theory of Relativity.
-
- For the first time, September 14, 2015, direct evidence was observed by LIGO. The gravity waves were being generated by two merging Blackholes. The LIGO interference pattern measured a frequency of 30 cycles per second corresponding to 15 orbits per second for the two Blackholes
-
- In just 0.2 seconds the signal surged to 250 cycles per second then disappeared. The orbiting Blackholes reached velocities half the speed of light before they merged.
-
- The two masses orbited so close to each other they had to be Blackholes. ( not Neutron stars ). The vibrations of space-time created a sine wave with a steadily increasing frequency and amplitude due to their near perfect circular orbits.
-
- Using computer simulations to recreate the data astronomers estimate the Blackholes to weigh 36 and 29 Solar Mass combining into a 62 Solar Mass Blackhole. The energy released was equivalent to 5,000 supernovae explosions. The 3 Solar Mass difference was dispersed as gravitational radiation. Our most powerful thermonuclear bomb was 1,030 times lower in energy. The single Blackhole emerging was spinning at 100 revolutions per second.
-
- How did these binary Blackholes first form?
-
- One theory is that two massive stars were born as a binary-star system formed from interstellar gas like a double-yoked egg. After a few million years the stars went supernova resulting in binary Blackholes.
-
- A second theory has the stars forming independently but in a larger globular cluster. Massive stars sink towards the center of the cluster. Complex interactions at the center form these binary system. By gathering material around the center they transform into Blackholes.
-
- Massive stars are more likely to form at the center of clusters where there are frequent collisions and mergers.
-
- LIGO is hoping for Blackhole collisions closer to home. This one was 1.3 billion lightyears away. Closer and lighter binary Blackholes, or Neutron stars, would chirp with higher amplitudes and would last longer, several minutes. This would provide more data for astronomers to learn more.
-
- The next step is to get more interferometers around the world involved, Japan and India are working on theirs. By timing the single event from different directions astronomers can triangulate and more closely determine the direction to search for Blackholes, or Neutron stars.
-
- Determining direction would allow for the exact amplitude of the signal to be calculated. The perpendicular direction produces the biggest signal. Knowing the amplitude more accurately would allow the distance calculations with higher precision.
-
- Matching gravity wave observations with electromagnetic observations could greatly enhance astronomy studies. A more accurate “Hubble’s Constant” could be measured., the rate of Cosmic expansion, Ho = 72 km/sec/mps = 47,000 miles per second per million lightyears.
-
- Albert Einstein predicted gravity waves would exist like light waves except they would be waves or ripples in space-time. He also predicted they would be too slight to ever be detected.
-
- 100 years later the technology progressed to beyond that which Einstein could have imagined. On September 14, 2015 the first gravity waves were detected just as his math predicted. After 5 months of checking and double checking by the two separate LIGO interferometers the announcement was made in February, 2016. The gravity wave source was the collision of 2 Blackholes 1,300,000,000 lightyears away.
-
- The two interferometers work by shooting infrared lasers breams through 4 kilometer arms in a near-perfect vacuum. Bouncing off quartz mirrors the beams come back to their starting point and merge together into an interference pattern.
-
- The redshift of the source Blackhole merger is between 0.05 and 0.12 through expanding space. This means the waves traveled between 700 million and 1,500 million years before reaching us. 1.3 billion years is a best estimate.
-
- Where the 2 perpendicular laser beams come together a signal above the null is sensitive enough to measure the distance the width of a Hydrogen atom. In effect we are hearing the Blackhole merger, since we can never actually see it.
-
- Today we have finally heard gravity waves, a sine wave chirp. When did the wave concept even begin? In 1865 James Maxwell predicted that light traveled in waves. But, it was not until the radio was invented by Heinrich Hertz that it was realized the light and radio were the same thing, electromagnetic radiation waves.
-
- In 1905 to 1915 Einstein introduced two new theories of gravity to be simply a warping of space-time caused by mass and energy. And, mass was really just concentrated energy according to E= m*c^2. He reasoned at the time that very massive objects moving rapidly would create gravity waves, ripples in space-time.
-
- LIGO was the first to measure these waves as they pass through the Earth at the speed of light. The waves were squeezing one perpendicular arm and stretching the other as the wave passed by. The interference pattern of the 2 laser beams were sensitive enough to hear these changes in distances.
-
- LIGO detection begins as massive orbits spiral and tighten to 5 revolutions per second. At that point the orbiting wave frequency is 10 hertz, 10 cycles per second. The 2 Blackholes merge in 0.2 seconds. At that point the frequency and sensitivity is strong enough for LIGO to detect it.
-
- This detection was possible because of the amazing engineering needed to separate the signal from noise and other interferences. The detection was so sensitive it could hear a car passing by the site at 10 miles per hour. The engineering feat was to pull the “ gravity chirp” out of this extraneous static.
-
- The next technology leap will put these interferometers into outer space where we can find a quieter place to make measurements. This space instrument is under design today. We are beginning a whole new field of gravitational wave astronomy. Stay tuned, more announcements will be made shortly.
---------------------------------------------------------------------------------------
- Request these Reviews to learn more:
-
- #1827 - Gravity Waves discovered using the LIGO telescopes.
-
- #1776 - Gravity Waves using computer simulations.
-
- #1754 - The tides of gravity. The tidal forces of galaxies.
-
- #1751 - Einstein’s Theory of Gravity. A spinning massive body pulls space-time along. It is like a spoon stirring honey. Einstein’s Equivalence Principle has withstood 100 years of challenges.
-
- #1728 - and - #1686 - Measuring the size of the Universe.
-
- #43 - The Gravity of it all. If the Earth were spinning 5 times faster what would happen to gravity? Nothing, gravity is a function of mass and distance, not rotation. If you dropped a bowling ball off a 10 foot ladder and fired a bullet horizontally at the same time which would hit the ground first? They both hit at the same time.
-
- #1534 - Getting used to bending light. Gravitational lensing.
-
- #1470 - Are there atoms in space-time?
-
- #588 - Gravity Probe B to discover the effect of Frame-Dragging.
-
- Matter can barely feel the presence of a gravity wave. Not only is it the weakest of the 4 known forces, its strength falls off sharply as it traverses space. The gravity wave LIGO detected squeezed and stretched the Milky Wave Galaxy that is 100,000 lightyears in diameter the width of your thumb. And, you did not feel a thing. Or, did you?
- --------------------------------------------------------------------------------------
---- 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” -----------
- https://plus.google.com/u/0/ -- www.facebook.com -- www.twitter.com
----- 707-536-3272 ---------------- Thursday, April 14, 2016 -----
------------------------------------------------------------------------------------------
No comments:
Post a Comment