detecting ripples in space-time, with a little help from einstein

by:UMeasure     2020-04-14
Marco Cavaglia is an assistant professor of physics and astronomy at the University of Mississippi and a member of the LIGO team.
Kai Staats is a filmmaker at the University of Cape Town and a master\'s student in applied mathematics.
Shivaraj Kandhasamy is a postdoctoral researcher working with Cavaglia in his lab.
The author contributed the article to Space.
Expert voice of Com: Op-Ed & Insights.
We look at the universe with optical and radio telescopes and see distant star systems and more distant galaxies.
We can tell to varying degrees how these systems are formed and how they evolve over time. High-
The Energy Astrophysical Observatory provides another revelation for these topics, providing a further understanding of their related physical phenomena.
But so far, science has yet to explore the internal structure of a neutron star, and no one has seen the last moments of the collision between the two black holes.
With gravitational waves, we have a unique opportunity to look at the universe in a new way. [
LIGO Trailer]
Gravity-laser interferometer
Wave Observatory (LIGO)
Designed to provide a new perspective.
LIGO recently installed detectors in Washington state and Louis Anna State, completing a major upgrade.
In the next few years, advanced LIGO instruments are expected to make gravitational wave detection a regular phenomenon.
In 1915, Einstein published the theory of gravity that is now widely accepted: general relativity.
General relativity is an extension of special relativity, which predicts large mass objects.
The time around them.
A common analogy is the ball sitting on the stretched rubber film.
The ball produces a lower point (a depression)
On the membrane, the beads so close to the ball rolling no longer move in a straight line, but along a curved path --
The beads were \"caught\" by the gravity well of the ball.
\"One can relate this analogy to our solar system, where the ball is the sun and the bead is the planet,\" said Hunter Gabat . \" Research Assistant at the University of Mississippi gravitational wave astronomy center.
\"Since Newton\'s first law of motion links changes in speed and direction to forces, the Earth\'s response to space --
The temporal curvature produced by the sun can be interpreted by the Observer as gravity.
If the ball is removed from the membrane, the bead will roll on the straight line at a constant speed, and of course the friction is ignored.
Similarly, if the sun suddenly disappears, the planets in the solar system will move straight away from the sun\'s gravitational well and enter interstellar space at a constant speed.
\"Both Newton and Einstein\'s theories explain how planets rotate around the sun and tell us that if the sun disappears, the planets will fly in a straight line.
Newton theory, however, describes space as immutable, and all forces, including gravity, act in an instant.
General relativity describes space and time as two dynamic aspects of the same entity, as space changes
Travel time at the speed of light.
Einstein\'s explanation of gravity has interesting results.
For example, if the sun disappears now, the planets will not fly away immediately.
Due to the limited speed of gravity propagation, it takes a limited period of time for the planet to feel the gravitational effect of the Sun\'s disappearance.
The Earth will continue in its current orbit for about 8 minutes.
The time it takes from the center of the solar system to the gravity of the Earth\'s orbit.
Another result of general relativity, perhaps the most surprising prediction of this theory, is the existence of gravitational waves.
According to Einstein\'s theory, any accelerating object will produce a dynamic propagation disturbance of space. time.
Just as you can stir a cup of coffee with a spoon and create waves on the surface of the coffee, the equation of general relativity says that matter can move in space --
If it is the acceleration time.
The concept of acceleration associated with wave generation is not a novelty of Einstein\'s theory.
Half a century before Einstein, physicist James Clark Maxwell has explained how to produce sound waves through the acceleration of charge.
The difference in general relativity is that gravitational waves transmit \"space-
Time, not the waves in the \"in\" space.
Like all waves in nature, gravitational waves carry energy from the sound waves of long numbers to the waves of your favorite radio stations.
However, they interact very weakly with other forms of energy, so they do not lose a lot of energy in their journey from the distant source of the universe.
Once they are produced, they will travel through the universe forever. well, almost . . . )
Precious information about their origins
Information that cannot be obtained by other means because the signal is very weak.
LIGO is the first instrument designed for this detection.
How to capture gravity waves, how to detect gravity waves?
Hulse-observation of orbital changes
Taylor binary system is the first binary system found, which provides indirect evidence for gravitational waves.
Similar to a satellite in orbit around our planet, sinking to Earth due to atmospheric friction losing energy, Hulse-Taylor (neutron stars)sink together.
Like two stars in the Hulk.
The Taylor system is getting closer and they release energy by stirring space
The time around them.
This energy is lost in the form of gravitational waves.
By monitoring the motion of this double-star pulse Beacon, scientists are able to test whether the speed of energy loss matches what is expected to happen due to the launch of gravitational waves.
The rate predicted by gravitational wave emission and the rate measured by monitoring the pulsating signal agree very accurately during 30 years of observation.
Joseph Horton Taylor, Jr. At 1993
Russell Huls won the Nobel Prize in Physics for his work at the Arecibo telescope observatory in 1974. The Hulse-
The Taylor pulse system provides indisputable evidence for the existence of gravitational waves.
But this is not direct evidence.
No one observed the real gravitational waves.
After more than ten years of design, development and planning, with the strong support of the United StatesS.
National Science Foundation, laser interference gravity-
Wave Observatory (LIGO)began in 1999.
LIGO\'s function is to directly detect gravitational waves from distant galaxies.
LIGO facilities include two \"L \"-
A structure of shapes separated by hundreds of miles, each with two 2. 5-mile-long (4 kilometers)arms.
One of them is located in Kensington Hanford, and the other is in Livingston Parish, Louis Anna.
The \"L\" shape is determined by the detector, laser interference meter of each facility.
The degree of precision required to \"capture gravitational waves\" is really hard to imagine.
Einstein did not believe such a measurement could be made.
To detect a typical cosmic gravitational wave on Earth, the distance must be measured at a distance of less than 10-19 meters (
About 1/10 of the diameter of the proton)!
Three LIGO detectors (
2 Hanford, 1 Livingston)
Launched on 2002.
After years of hard adjustment and improvement, they operate with design sensitivity between November 2005 and September 2007.
In 2010, additional data operations for the enhanced version of the two detectors were completed.
The upgrade is called Enhanced LIGO, providing higher laser power, frequency
Modulation radiation detection, output mode cleaning and input
Vacuum read out hardware.
The main purpose of the initial LIGO project was to demonstrate that researchers could build and operate instruments that were sensitive enough to detect gravitational waves.
Never tried using big before LIGO-
Scale interference meter.
When LIGO started construction, the technology needed did not exist.
The LIGO project is equivalent to building a new scientific instrument.
Not something you can order on Amazon!
Although the original LIGO was not detected, the first-
The production of LIGO instruments proves that the goal of directly detecting gravitational waves can be achieved.
Even if it is not found, LIGO\'s data results in many astrophysical results.
An example of this is related to the brief intense burst of energy gamma rays detected by Konus in the direction of Andromeda galaxies
Wind, points, Messenger and Swift gamma-
Lei satellite February 1, 2007
While observing this gamma-ray burst known as GRB070201, LIGO instruments at Hanford facility are collecting scientific data.
Such a huge cosmic event in a nearby galaxy should produce gravitational waves easily measured by LIGO. The non-
Observation of gravity
The wave signal after the explosion means that GRB070201 is not from Andromeda.
Other reasons for the event, such as soft gamma-
Binary merge of light repeater or more distant is the most likely cause of the event.
In 2010, engineers and technicians from Handford and Livingston facilities are engaged in the task of fully dismantling the Enhanced LIGO instrument in order to upgrade to a more powerful configuration: Advanced LIGO.
A few weeks ago, on May 19, when LIGO\'s two advanced detectors were put into use at a ceremony in Hanford, the journey ended.
Advanced LIGO will begin collecting astrophysical data later this year.
Eventually, these machines will become 10 times more sensitive than their first.
A generation of predecessors, far beyond our local Virgo Supercluster, opened a thousand
The volume of space that LIGO can measure has doubled.
How does the interference meter use an optical instrument for the interference properties of light?
Specifically, small differences in the distance between the two light paths are measured.
Due to their high accuracy, they are widely used in science and other industries and can be measured very precisely for very small and very large distances.
The basic mechanism of gravity-
The wave interference method is simple: divide a laser beam into two beams that propagate on different paths, then reflect by the mirror, and then restructure into a beam that impacts the detector.
When the beam is regrouped, the beam is carefully arranged outside the phase to offset each other.
Two beams of \"destructive interference\"
Therefore, the word \"interference.
If a gravitational wave is distorting space
Over time and the length of the beam path, the two beams will no longer be completely absent.
Even small changes in space
Time will release the light from the phase, producing a small amount of light, hitting the detector of the interferometer.
Of course, things are not that simple in real life.
Because of gravity
Optical recognition wave signal-
The output strength change of the detector with ultra-stable laser is very important.
Input optical system (IO)
When the laser enters the interferometer, a stable initial stage is provided.
In the input optical system, the input mode cleaner (IMC)
Reduce the fluctuation of light entering the interferometer and provide frequency stability by filtering out unwanted laser modes.
Then send the beam to the beam splitter (BS)
Divide the beam into two beams, each along the L-Shape detector.
Beam reflection from the end mirror (ETMs)
, Returns the splitter that redirects them last time, and finally combines at the output photo-detector (
Marked \"GW reading \").
Two input mirrors (ITMs)
Keeping the laser in the arm for a period of time effectively increases the length of the arm, thus increasing the sensitivity of the detector.
If the laser takes twice as much time on each arm, the arm will appear (to the laser)
Twice the time.
As a result, the sensitivity is doubled.
If the laser crosses a total length of 100 times, about 1 millisecond, it will move 400 km times and increase the sensitivity by 400 times.
Power Recovery (PR)
Including the cavity of the mirror (
PRM, PR2 and PR3)
Reflect the beam toward that part of the laser back to the beam splitter.
To clear the signal from the interferometer and select only the mode sent in the signal recovery (SR)cavity (
Includes mirror SRM, SR2, and SR3)
Clean the cavity using output mode.
Most of these mirrors are placed in vacuum chambers and suspended in very complex multi-stage pendulum to reduce their coupling to ground motion.
Working on a noisy planet, because LIGO detectors are such sensitive instruments, they are easily affected by external interference, or what scientists have cumulatively called \"noise \".
\"The main source of noise is caused by the quantum properties of light, the thermal vibration of the atoms that make up the optical system and the suspension of their support, from the seismic noise that continues to vibrate on the Earth\'s surface.
Other various effects that can be coupled to various parts of the interferometer and reduce the sensitivity of the instrument are artificial
Do ground Sports (e. g.
Trains, cars and trucks);
Sound signal from the planepower-
Fluctuations in supply; weather-
Temperature changes, strong winds, storms and other related events;
As well as many other sources of instrument and environmental noise.
Stabilizing an instrument for finding a 1/10 diameter proton motion is not a simple task.
At each site of the LIGO observatory, there are a large number of environmental sensors (
Radio, microphone, earthquake meter
Frequency Receiver and temperature sensor)
Constantly monitor the surrounding environment.
Thousands of other sensors monitor the state of the instrument and remain stable (\"locked\')
Through the computeractuated, real-
Time feedback loop and control mechanism (servo-
Actuators that maintain the Mirror\'s relationship with each other).
Data from components are transmitted to the control room in real time, and LIGO researchers work with operators to monitor and maintain the entire system.
Louisiana aria Effler, a graduate student at Luanna State University, is working with Advanced LIGO instruments as it is already online.
\"Due to the amazing sensitivity of LIGO, the source of noise will never be considered in other experiments,\" Effler said . \".
\"We have to think about what these sources are, try to find the coupling mechanism, measure the effect, decide if it is a restricted noise source, create a model to explain it, then the noise of the source is reduced or the coupling with the detector is reduced.
It requires a deep understanding of many aspects of physics and engineering, so we are always learning.
\"There are obstacles to building the world\'s most advanced astronomical observatory.
\"I\'m afraid of the wind,\" said Sheila Dwyer, a postdoctoral fellow at the Massachusetts Institute of Technology in LIGO, who works with the commissioning team at the Hanford Observatory.
\"The wind can move the ground and make things quite difficult.
We need to do a lot of work to reach the same level as the ground [when]is]quiet.
This is a necessary job because we want to be able to observe in bad weather and good weather.
\"Now, after nearly 30 years of its establishment, how does LIGO know if it has succeeded?
After several months of installation, the Advanced LIGO installation has succeeded in exceeding its predecessor in sensitivity.
\"We will continue our work to achieve the sensitivity we want in the design of the instrument, enabling us to\" see \"up to 0. 6 billion of the light
A few years later, \"adds everler.
Of course, the biggest success will be when we detect gravitational waves directly for the first time in human history.
\"In a great leap forward before 1887, Albert Michael son and Edward Moley overturned the existence of the ether using a desktop interferometer at the Case Western Reserve University in Cleveland, Ohio (
For the intangible medium that spreads light, this is a concept that was popular at the time). This Michelson-
The Moley experiment laid the foundation for Einstein\'s special theory of relativity and general theory of relativity.
Now LIGO is using kilometers
A prophecy that directly measures Einstein.
Isaac Newton wrote in a 1676 letter to scientist Robert hook, \"If I look further, it is standing on the shoulders of giants.
\"Scientific Achievement is never the brain of a person, a\" lonely genius \".
\"Instead, they stem from the joint efforts of generations of men and women who are committed to pursuing knowledge through scientific methods.
The concept of LIGO is simple, but it has been made for nearly 30 years and is based on a fundamental principle: interference of light.
But it was the work of generations of scientists, researchers and engineers that made this incredible instrument possible and quickly provided us with a new way to observe the universe.
For more information on premium LIGO, see the movie LIGO generation by Kai Staats.
The two films combine \"passion for understanding\" to provide LIGO experiments with insight into dedication, passion and incredible challenges.
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This version of this article was originally published on Space. com.
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