A "Still Small Voice" from the Beginning of Time: A Jewish View on the Discovery of Gravitational Waves.
In the Beginning, on a scientific timescale of more than a billion years ago, at the very far edge of the universe more than a billion light years away, two black holes collided and fused in a tremendous explosion. A miniscule echo clothed in the form of a gravitational wave traversed the universe, finally reaching our galaxy about 100,000 years ago.
On the first day of Rosh Hashanah, September 14, 2015 at 12:50 in the afternoon (Israel time), when all created beings stood in judgment before the King of Kings, a [10.sup.-18] meter disturbance, less than 1/100th the size of a single proton (the smallest particle currently known to mankind), was registered by two separate experimental systems in the USA. This disturbance was translated by the measuring systems of the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Louisiana into a tiny fragile sound. The publication of the first confirmation of this discovery on February 2, 2016 rocked the scientific community. Many proclamations were made heralding a new window being opened up into space research. Just under two years later, three of the project's founders were already awarded the Nobel Prize in Physics: half to Rainer Weiss for his conceptualization and initial design of the experiment, the other half jointly to Barry Barish and Kip Thorne for their later contributions enabling and facilitating the discovery.
Since the initial discovery, at least six additional sightings have been confirmed so far. A third experimental complex in Europe recently completed its construction and promptly joined forces with its two counterpart facilities in the United States. This provides not only an increased reliability in the signal measurement and verification, but also the additional advantage of more than a tenfold increase in our capability of pinpointing the exact direction from which the signal emanated. Periodic phases of maintenance, calibration, and upgrades to all three systems have now given the network enhanced sensitivity as well, hopefully increasing the chances of even more sightings in the near future.
In order to start to understand the full significance of this discovery, we should briefly consider four questions:
1. What are gravitational waves?
2. Why is it so difficult to "feel" them?
3. What is so special about them?
4. What conclusion should scientists make?
WHAT ARE GRAVITATIONAL WAVES?
What would happen if our sun were to suddenly disappear? Outside of the fact that we would not have light, the orbit of the Earth (influenced by the gravitational force between the sun and the Earth) would go off course. Considering that it takes a little more than eight minutes for light rays from the sun (electromagnetic waves) to reach us, after the sun disappeared, we would still continue to receive light for a full eight minutes without yet knowing what had happened. The same thing pertains to the Earth's orbit. The Earth would continue in its orbit unaffected for eight minutes as if the sun were still there, not yet feeling the change in the gravitational field. It is the gravitational waves that would transmit the "information" to the Earth and signal the new gravitational reality.
Gravitational waves do not appear in Newton's equations (in which the reaction is considered to be immediate). Our knowledge of gravitational waves comes from Einstein's General Theory of Relativity. Although the equations are complex and can only be solved with the help of computerized simulations, the idea itself is rather simple. According to Einstein's theory, the gravitational field that we feel is actually the curvature of the space-time continuum surrounding us. A "wave" means a periodic disturbance. A gravitational wave is a periodic disturbance in the gravitational force that we feel. A moving disturbance of this force would then translate into an actual change in the space-time structure surrounding us. In this scenario, when a gravitational wave passes by us, the space around us in which we exist and function contracts ever so slightly for just a fraction of a second and then immediately expands back, without us feeling a thing.
WHY IS IT SO HARD TO SEE OR FEEL GRAVITATIONAL WAVES?
The reason this disturbance is not felt in our daily life is because it is very, very small. It is so miniscule and insignificant that it is hard to even imagine. It does not matter what example or analogy our brain uses, the size of the disturbance will simply be classified under the heading of "small." It is the same as when we try to consider the size of an atom or a proton; our brain cannot fathom the miniscule dimensions. Alternatively, trying to magnify the size of the disturbance, comparing it to a single hair's breadth along the path to our nearest neighboring galaxy, would be equally useless, as our brain would still struggle to comprehend the enormous difference in scale between the two different sizes.
Thus it is difficult for us to appropriately marvel at the mind-boggling engineering achievement accomplished by the LIGO observatory measurement. To try to provide some perspective, two more things can be mentioned to hint at how tiny this disturbance really is. First, in order for the experiment to succeed, it must take into account tiny movements caused by the miniscule physical pressure exerted by the laser light on the mirror. This ordinarily negligible phenomenon cannot be overlooked here. Secondly, even movements created by random quantum tremors on the atoms of the mirrors must be taken into account.
PRECISELY THE SIGNIFICANCE OF NOT FEELING THEM
If we do not feel them, what is nevertheless interesting about these waves? The answer lies in their lack of interaction with the environment. Almost nothing in the universe can stop them. They pass without change through everything that stands in their way. After billions of years, when they finally reach Earth, they simply continue onwards as if nothing happened. They do not move through a material medium, but through the space-time continuum itself. To a certain extent, it could be said that the waves themselves are part of the space-time continuum. They are almost not absorbed or dispersed along their journey, and therefore theoretically it should be possible to sense them from one end of the cosmos to the other. In this lies hidden their great untapped potential.
WHY IS THIS SO IMPORTANT?
True, these waves do not impact us directly, but this discovery opens a new era for astronomy. Up until now we were "deaf" to these sounds whispering the secrets of the universe. There are at least three important areas of investigation in which gravitational waves can greatly help us in space research. We can now understand more about black holes, dark matter, and the Big Bang. Up until now, with the instruments available to us, it was impossible to directly observe black holes. No drop of light can escape the inside of a black hole in order to come back and tell us of its presence. The discovery of gravitational waves is one of the most direct signs that we have currently received that clearly point to the existence of these "creations."
The second area of study is connected to the structure of the universe and dark matter. A detailed explanation of dark matter is beyond the scope of this article, but it, too, is an element with physical properties difficult to study with our standard instruments of measurement. Radiation and absorption of light are not the strong sides of dark matter, as its name suggests. Perhaps its interaction with gravitational waves will be more significant, thus allowing us to detect the effects of gravitational waves on dark matter.
The third area of study is help in deciphering the Big Bang. When we observe radiation emanating to us from the Big Bang, our research is limited to a point in time 300,000 years after the initial event. It is impossible for us today to see the radiation absorbed prior to this point in time, as it is completely absorbed in an impenetrable plasma screen. Gravitational waves, on the other hand, are indeed capable of penetrating this screen. Assuming we shall be able to see such waves emanating directly from the Big Bang, perhaps we may be able to receive insights from points in time closer to the very first moments after the Big Bang.
In addition to all these new directions, having a new means for studying the universe is a boon to science and especially astrophysics in and of itself. Additional new discoveries and intriguing, previously unimagined phenomena can be expected. In fact, the first incredible example of this has just surfaced.
In October of 2017, the LIGO project together with astronomers from over 70 observatories worldwide (including a handful of spacebased telescopes) announced the first sighting of a neutron star collision, observed two months prior in mid-August. The gravitational wave emitted in the process was first detected by LIGO and its origin point was accurately pinpointed immediately. This allowed numerous astronomers worldwide to point their own instruments at the exact location and witness a wide array of light signals along with many other types of other radiation.
The combination of both classical astronomical data and gravitational-wave data provided scientists with a stunning picture, telling a complete scientific story. This new observation has far-reaching implications for our understanding of the universe--from providing insight into how the elements on the periodic table were formed, to confirming long-standing predictions regarding the radiation emitted in such stellar collisions, and finally providing independent confirmation on the nature and speed of gravitational waves themselves.
Still, this is but one example of an unpredictable advance from this exciting new frontier. The scope of the scientific collaboration achieved in this one small astronomical observation is almost unprecedented. The multi-sensor picture pieced together from all the telescopes and detectors working in synergy truly dazzles the mind, increasing our wonder and curiosity for what is yet to come.
Without a doubt, the scientific discovery of gravitational waves is worthy of the Nobel Prize that has been announced to Weiss, Barish, and Thorne, not only for its confirmation of Einstein's theory and for the ingenious engineering skills involved, but mainly for the window it is opening for the future.
WHEN WE SHALL BUILD THE NEXT OBSERVATORY
From a faith-based point of view this event reverberates on a number of levels. First of all, we can marvel at and praise the wonders of Creation. If upon hearing thunder Jews bless "that His power and might fill the world," then how much more so should this be true for an event of this type. Although relative to the boom of thunder the sound that reached us was a "still small voice," smaller than small, it nevertheless "filled the world" on an unprecedented scale, touching all of the cosmos, in space and in time, from beginning to end. It is at the very least worth keeping in mind in our morning prayers as we recite the blessing praising the "Creator of the shining stars."
The second level is praise and thanksgiving to G-d that we are able to succeed at all in understanding the universe. In the spirit of the blessing formulated by our sages (upon seeing an outstanding secular scholar): "He Who gave from His wisdom to flesh and blood," we are talking here about events that occurred in the past too distant to perceive, well beyond our wildest imagination. The fact that we are able to plan such a sophisticated experiment and on the basis of its results to make such far-reaching conclusions is indeed a great wonder.
This story serves as a wonderful analogy to the role of the Tabernacle. The LIGO observatory, as we have said, is amazingly sensitive and precise, planned in excruciating detail. It has an extraordinarily precise and stable laser, round mirrors polished to one-hundredth hair's breadth accuracy, a four-kilometer length of clean pipes with pure vacuum space (requiring forty hours of suction to reach the desired level), and mechanical systems sensing every movement or tremor on the ground. Every grain of dust influences the result. Repair and calibration of the system are done only in special sterile "white suits." Any change whatsoever, no matter how small, from the plan is liable to damage signal reception and ruin the entire experiment. This is similar to what is written in Yehuda Ha'Levi's Kuzari (article 3: 23) about the precision of the details in the Tabernacle described in the Torah portions of Trumah, Tetsaveh, Va'Yak'hel, and P'kudey:
We have, however, said that one cannot approach G-d except by His commands. For He knows their comprehensiveness, division, times, and places, and consequences in the fulfillment of which the pleasure of G-d and the connexion with the Divine Influence are to be gained. Thus it was in the building of the Tabernacle. With every item it is said: "And Bezalel made the ark... the lid... the carpets..." and concerning each of them is stated: "Just as the L-rd had commanded Moses." This means neither too much nor too little, although our speculation cannot bear on works of this kind. Finally it is said: "And Moses saw the whole work, and behold they had performed it just as the L-rd had commanded, thus they worked, and Moses blessed them." (Exodus 39:43) TRANSLATED BY HARTWIG HIRSCHFELD, 1905
The Tabernacle is the "sacred observatory" that shows us in a palpable form the reality of the Sh'khinah (G-d's presence) in the world. Just as the LIGO observatory is designed in detail, so was the Tabernacle. Moreover, one hundred years ago Albert Einstein sat in an office or library laboring over the equations of the Theory of Relativity. Relying on intellectual investigation alone, he became convinced of the existence of gravitational waves, without any chance to detect them (and it's doubtful if he believed that it would ever be possible to detect them). Thus it is also with holiness. The Torah is our "book of theory." We believe that there is holiness in the world even when there is no Tabernacle or any other experimental system capable of showing us holiness. Even when we do not see the high priest exit the Holy of Holies and the ten miracles that were performed for our forefathers in the Temple, we are convinced that the Sh'khinah is found within us.
This leads to my final conclusion. For one hundred years we were not able to detect gravitational waves. Scientists throughout the world racked their brains again and again trying to come up with original ideas, some more far-fetched, some less so, in tireless pursuit of any lead at all on how to reveal this phenomenon. The recent successful experiment is the fruit of more than forty years of toil, an investment of more than a billion dollars, and countless hours of work by thousands of scientists from dozens of different countries. It stems from many previous less successful experiments trying to achieve the same result. Some of these attempts were intentionally destined for failure from the start, and they were only conducted for the purpose of learning how to do better in the future. Hundreds of articles and dozens of doctoral theses were written to try and imagine what the signal might look like, should we ever be privileged to see it. We should feel challenged to match this level of passion in our desire to see, and our efforts to bring about, the revelation of holiness in the world. We must not rest until we see eye to eye "where is the place of His glory."
Translated from Hebrew by Ilana Attia
SHIMON LERNER, PHD
ABOUT THE AUTHOR
SHIMON LERNER teaches physics at the JCT Lev Academic Center. Born in New York, he moved with his family to Israel while he was a young boy. Upon graduating high school, he entered the Atudah program of the IDF, studying for a degree in electro-optics at Machon Lev and afterwards serving as an officer.
He received his PhD from the Hebrew University of Jerusalem in the field of condensed matter physics, under the supervision of Professor Yuri Feldman. During his formative years he studied Torah with Rabbi Natan Bar Haim of JCT and with Rabbi Aharon Lichtenstein, of blessed memory. Residing in Jerusalem with his wife and children, he regularly teaches a variety of topics in both halakhah, and Torah and science in his local synagogue. He now teaches at the JCT Lev Academic Center, where he sees it as both a mission and a privilege to impart to his students the methods of critical scientific thinking.
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|Date:||Jan 1, 2017|
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