This is what the project managers say ahead of the re-opening of the two observatories which together enable the discovery of gravitational waves. Mitzpe Virago in Italy will also be back in operation, also after a renovation that allowed them to increase the sensitivity. A Japanese telescope will also be put into operation soon, and a combination of the four observatories will allow for accurate localization of the source of the gravitational waves
In February 2016, scientists at the Gravitational Wave Observatory (LIGO) made history when they announced the first detection of gravitational waves. These ripples in the fabric of the universe, caused by mergers of black holes or dwarfs, were first predicted by Einstein's theory of general relativity about a century ago.
About a year ago, two LIGO facilities were shut down to perform hardware upgrades to the detectors. These upgrades have been completed and LIGO has announced that the observatories will resume operations on April 2. The scientists expect that the increased sensitivity of the facilities will allow the detection of gravitational waves every few days, that is tens of years.
So far, 11 gravitational wave events have been detected over about three and a half years. Ten of them were the result of black hole mergers, while the remaining discovery is of a neutron star collision event (kilonova event). By studying these events, the scientists actually started a new era in astronomy.
Now that LIGO's upgrades are complete, scientists hope to at least double the number of events detected in the coming year, said Gabriela Gonzalez, a professor of physics and astronomy at Louisiana State University who has spent years searching for gravitational waves.
"Galileo invented the telescope or used the telescope for the first time for astronomical observations 400 years ago. And today we build better telescopes. I think this decade is the beginning of gravitational wave astronomy, so we will continue to move forward with better detectors and adding detectors.
LIGO's facilities are located in Henfield, Washington and Livingston, Louisiana. They consist of two concrete pipes connected at the base point and make up the shapes of the letter L. Each pipe is 4 km long. Inside the tubes, two powerful laser beams pass through a series of mirrors and are used to measure the length of each arm with extreme precision.
When the gravitational waves pass through the detectors, they distort the space and cause the length of the tubes to change at very tiny distances (that is, at the subatomic level). According to Joseph Gaima, head of the LIGO observatory in Livingston, Louisiana, the latest updates include improvements in optics that will allow for increased laser power and reduced noise in their measurements.
For the rest of the year, gravitational wave research will also be strengthened by the fact that a third detector (Virgo Interferometer in Italy) will also be ready to retake observations after being upgraded to take observations. During LIGO's last observing run, which lasted from November 2016 to August 2017, Virgo only became involved towards the end and collaborated on some of the discoveries.
Also, Japan's KAGRA Gravitational Wave Observatory is expected to become operational in the near future, and will enable the establishment of an even stronger detection network. Having multiple observatories separated by vast distances around the world not only allows for a greater degree of verification of discoveries, but also helps narrow down the area in space from which the signal is coming.
From the following observation, astronomers working in the field of gravitational waves will be able to take advantage of a public alert system, which has been a permanent feature of modern astronomy. And so when LIGO detects a gravitational wave event, the team will send an alert to stargazers all over the world, so that they turn their telescopes towards the source and learn more about the event by chance and it creates observable phenomena.
Such was the case with the 2017 kilonova event (also known as GW170817). The two neutron stars whose merger caused the gravitational wave event left a bright glow for a long time. The collision led to the release of fast jets of matter and the creation of a black hole.
According to Nergis Mavalvala, a gravitational wave researcher at MIT, observable phenomena associated with gravitational wave events are rare, but there is always a chance that something completely unexpected will be discovered that will leave scientists amazed.
"This is how discovery happens. We activate a new device, point it at the sky and see something we had no idea about before"
The study of gravitational waves is just one of the revolutions taking place in astronomy these days. Similar to other fields of research (such as the study of extrasolar planets and observations of the early universe), it will benefit from the introduction of improved instruments and methods in the coming years.
16 תגובות
Conan,
You asked a very good question. I found this article that answers her:
https://www.forbes.com/sites/startswithabang/2019/03/02/ask-ethan-why-dont-gravitational-waves-get-weaker-like-the-gravitational-force-does/#7ed9dafc2f58
Miracles,
You're right! I just didn't read your answer correctly. Gravitational waves do move at the speed of light, but tectonic noises (footsteps, earthquakes and other seismological disturbances) do move at a lower speed (not necessarily at the speed of sound, but sometimes in the form of faster shock waves - but still terrifyingly slow than the speed of light in a vacuum).
Regardless of the gravitational waves, you will surely agree with me that the currently accepted astrophysical estimate holds that the expansion of the universe (= "the fabric of space") is higher than the speed of light, and even continues to accelerate during the last 7 billion years.
Thanks to you, I finally understood that it doesn't matter where the LIGO and similar devices are located - the daily noises shouldn't interfere with its activity, and it doesn't matter how "noisy" the environment is.
On the other hand, environmental noises - although not at the frequency and speed of gravity waves - still affect the measurements of gravity waves, since the optical devices move slowly due to vibrations in the ground - and therefore change over time the length of the optical path of the lasers, so that the instruments must be calibrated frequently if you want correct measurements.
The last question I have left is why the gravitational waves weaken during their movement in the fabric of space-time (so, for example, violent events such as the merger of two supermassive black holes, or even the merger of two neutron stars - which release enormous amounts of energy - weaken so much during their movement, and reach us at a very low intensity)? Do gravitational waves have some kind of energy loss such as friction during their movement, or perhaps it is simply an effect similar to the weakening of light intensity from a point light source, which weakens according to the square of the distance from the observer - due to anisotropic propagation in three dimensions?
Nissim - thanks again for the clarification, you made my day! ?
Conan
I was not wrong.
I never said anywhere that gravitational waves are waves in matter.
Gravitational waves travel at the speed of light.
If you don't believe me - here is a link:
http://blogs.discovermagazine.com/d-brief/2017/12/08/speed-of-gravity-light/#.XJ8On5hKhhE
Miracles,
In my opinion, you are confusing and wrong in a big way: gravitational waves are not movements of matter! During the motion of gravitational waves, the medium of any substance expands and contracts, but this is not an effect in which nearby atoms hit and move each other - such as the movement of sound waves in a solid, liquid, gas or plasma. Gravitational waves are oscillations of the fabric of space-time itself.
What is interesting is that, according to modern theories, the "fabric of space" (which is synonymous with the concept of "space-time texture") - in the past (around a second after the big bang, during the "inflation" phase of the universe) and now (for about 7 billion the last few years) - spreads at a speed higher than the speed of light! Beyond that, there is evidence that only in the last 7 billion years the rate of expansion of the fabric of space began - and still continues - to accelerate, which astronomers attribute to some force called "dark energy" - which is a force whose origin and properties are unknown, and no astrophysicist today has a clue About this repulsive force and why it started to act and influence only about 7 billion years ago, when it seems that it did not exist before - but this mysterious force corresponds to astrophysical measurements and calculations and astrophysical findings.
It turns out, according to the theory of relativity, that ordinary matter cannot reach the speed of light and certainly cannot exceed it in our universe, but the space-time fabric has no maximum speed at which it can move (the space-time fabric is not matter!!!), and therefore we see that even in the inflation phase of the universe (as mentioned, around a second after the big bang) and also during the last 7 billion years, the speed of expansion of the space-fabric is higher than the speed of light and now even continues to accelerate.
According to what I have learned and taught myself, gravitational waves are slightly slower than the speed of light, and weaken the further their source is from the observer (as if the vibrations in the space fabric have some kind of "friction").
Conan
Gravitational waves travel at the speed of light, while vibrations of various kinds travel at the speed of sound.
The difference is huge, even though the speed of sound in rock is 10-15 times higher than the speed of sound in air.
Giulio Andreotti,
I am amazed at your response. Overall, the discourse here is rational. Conan asks logically, and some try to answer fairly. "The comments here are dumb" - is that what you have to say, instead of writing something intelligent? And what about the bad and irrelevant comment about religion?
"Power weakens those who have no power." Remember who said that?
On the same weight, I tell you:
Intelligence fails those who do not have intelligence.
The heart denies those who have no heart.
What's the deal with religious hatred?
gift,
Your argument, according to which the measurement is very short and therefore natural (e.g. tectonic, footsteps of animals, etc.) and artificial (e.g. cars driving nearby) noises will not interfere with the measurement - sounds convincing and very true to me. Thanks for drawing attention to this point.
On the other hand, the duration of a significant event, which produces measurable gravitational waves, is not that short, but lasts several minutes to hours (correct me if I'm wrong) - so it is possible to detect the existence of the event, but the results that will be measured will not be correct and consistent.
Even a comparison between 2-3 detectors spread around the earth will not correct the noise and inaccuracies, since in any scientific measurement - and here too - statistics must be relied on, meaning that results from a large number of detectors are needed (and not just the 3-4 that exist today).
The comments here are stupid.
Ignorant people try to bring their opinion without any scientific basis and without learning anything.
And religion - the source of evil and ignorance. The reason that religion brings only the thought of people from hundreds and thousands of years ago who really, really knew nothing, maybe only what was beyond their noses.
Conan
If you calculate how long it takes for light (a laser beam) to travel a distance of 4 km - the length of the tunnel - you will find that during this time any disturbance such as an earthquake or the steps of a spider as you say are completely negligible. There is a video on YouTube that explains the measurement process, watch and learn the subject, then doubt
If you write an application that will work correctly with accelerometers and a camera, you can, under specific conditions, have smartphones all over the world measure gravitational waves!
Without all the noise and ringing
The problems raised by the previous writer are indeed difficult to solve. That's why they place the device on shock absorbers and try to dampen the vibrations. But the most important thing is that the identification that this is a real event is by the fact that it happened in 2 or more detectors and the further they are from each other - the better.
Avi,
What is important is the total distance that the laser beams travel; As you mentioned, the distances change when gravitational waves hit them - but even when there is an earthquake the entire optical equipment moves (for example the mirrors shake), and this in a significant way (much more than a subatomic order of magnitude) - therefore the optical path will change. Determining when it's gravitational waves and when it's optical distance changes from another source (like the steps of a spider a few meters away from the facility) - becomes (in my opinion) more of a gamble and less of a science.
For those who asked about how to recognize that it is not an earthquake.
Gravitational waves actually change the length of the tube, it becomes shorter and then lengthens again, earthquakes do not do that but just rock it from side to side.
At the beginning of the seventh paragraph in the publication here it is explained that the gravitational waves create a displacement on a subatomic scale when they reach the detectors (Virgo and/or Ligo). If so, how can such a sensitive detector work in Japan? After all, there is tectonic movement there all the time - that is, there is always noise that is not even constant and actually changes all the time - so how will they know if gravity waves really reach the detector or if it is actually just a mild earthquake (for example, 1.2 on the Richter scale)? The incessant noise of the earth's movements will not allow measurements of subatomic displacements! Beyond that: stronger earthquakes will distort the arms of the Japanese facility - therefore, after a moderate earthquake - in the best case the detector will need extensive calibration and renovation, and in the worst case the detector will be deformed in a significant and irreversible way, then it will not be possible to use it and the Japanese will have to build a detector New!
And regarding the Virgo and Ligo detectors in the USA and Italy - they are built on the surface of the earth, so that every gust of wind and even steps of any animal (small or large) in a wide area around the detectors will cause subatomic movements that may be considered as gravitational waves (the so-called False Positive). How do you overcome that too?
It is interesting that no ultra-Orthodox source has yet found that in the book of Genesis there are jumps every 16 letters diagonally, so we will immediately discover the sentence "Gravitational waves are created by the merging of black holes"