Since time immemorial, we have been fascinated by the heavens. The sight of the heavenly bodies – the sun, moon and stars – sparked the human imagination. At first, we tried to understand the skies through myths, imagined and developed from generation to generation. In the heavenly constellations we saw chariots, animals, pottery, gods and heroes. Yet alongside our fables and tales, the more scientifically-minded amongst us started to notice how the heavenly bodies moved, and started to use their positions to calculate the days, the months and the seasons. From this, we developed the most basic science of all: mathematics, as the Qur’an testifies to:
He it is Who made the sun radiate a brilliant light and the moon reflect a lustre, and ordained for it stages, that you might know the number of years and the system of calculation. Allah has not created this but in truth. He details the Signs for a people who have knowledge.1
Alongside the myths, scientists and philosophers continuously sought to rationally understand the vault of the heavens above us. Greek philosophers like Pythagoras and Ptolemy were followed by the giants of the Islamic sciences, such as Ibn Al-Haytham, Al-Battani and Al-Khwarizmi, who critiqued and further developed the field with observation and careful measurement. The next window into the heavens opened up relatively recently with the development of radio astronomy. We began to look at the sky using radio waves and microwaves. We discovered what the stars were composed of, through our knowledge of the electromagnetic spectrum, which varied from visible light to beyond the infrared and ultraviolet spectrum. It is during this time that our understanding of the celestial bodies advanced, just as the Holy Qur’an prophesied would happen in the age of the Messiah:
And when the heaven is laid bare.2
We are lucky enough to witness an example of this in our lifetimes with the recent detection of gravitational waves.
What are Gravitational Waves?
Gravitational waves are not electromagnetic radiation. It was Einstein who first predicted gravitational waves with his theory of general relativity in 1915. While Isaac Newton explained gravity in the 17th century as a force that acts between any two objects possessing mass, Einstein believed that gravity is the result of the distortion of the space-time fabric by such objects. While the Newtonian theory of gravity holds good for most common observations with remarkable accuracy, it fails to explain several phenomena associated with very heavy objects like neutron stars and black holes.
The distortions in space-time due to such heavy bodies as described by Einstein are much like how a trampoline or a stretched sheet of fabric deforms when a heavy object is placed upon it. It is interesting to note that though Einstein was the first scientist to theorise the existence of the space-time “fabric,” reference to it can be found in the Holy Qur’an:
Remember the day when We shall roll up the heavens like the rolling up of written scrolls by a scribe. As We began the first creation, so shall We repeat it — a promise binding upon Us; We shall certainly perform it.3
And they do not esteem Allah, with the esteem that is due to Him. And the whole earth will be but His handful on the Day of Resurrection, and the heavens will be rolled up in His right hand. Glory to Him and exalted is He above that which they associate with Him.4
The verses above refer to the universe as a deformable fabric or parchment that can be rolled up, similar to how Einstein conceived of space-time.
A major prediction of Einstein’s general theory was the existence of gravitational waves. While he described the force of gravity as the distortion in the fabric of space-time, gravitational waves were described as the ‘ripples’ in the fabric of space-time caused by massive accelerating objects. These ripples are much like what we see when we throw a stone in water or if a heavy ball were to be bounced on a trampoline.
Gravitational waves have an effect similar to electromagnetic waves. Just as electromagnetic waves carry the electromagnetic force, gravitational waves ‘carry’ energy known as ‘gravitational radiation’. When electromagnetic radiation strikes an object it induces electricity or magnetism, and in a similar fashion, when gravitational waves strike an object, they distort the space around the object, thus changing the actual size of the object. While some of us may wish to blame our ever-increasing weight on passing gravitational waves, unfortunately (or fortunately) the effects of gravitational waves are very small.
Detecting Gravitational Waves
Since the prediction of gravitational waves by Einstein, the scientific community has been working on detecting them. Unlike electromagnetic waves, gravitational waves cannot be ‘seen’ with the naked eye, telescopes or antennas. We can only ‘observe’ them indirectly through their effects. Interestingly, we can find reference to such invisible forces holding the heavens together, in the Holy Qur’an:
He has created the heavens without any pillars that you can see, and He has placed in the earth firm mountains that it may not quake with you, and He has scattered therein all kinds of creatures; and We have sent down water from the clouds, and caused to grow therein every noble species.5
The verse above is sometimes understood to mean that Allah has created the universe without any pillars. However, a more accurate translation is that Allah has created the universe without any visible pillars. This may be pointing towards gravity in general and gravitational waves in particular.
The first observation of gravitational waves came in 1974 when a binary pulsar system, the Hulse-Taylor binary – two extremely dense and heavy stars orbiting around each other – was discovered. It was discovered by Russell Alan Hulse and Joseph Hooton Taylor, Jr., of the University of Massachusetts, Amherst. Their discovery of the system and analysis of it earned them the 1993 Nobel Prize in Physics. The system was observed for eight years and it was determined that the stars were getting closer to each other at precisely the rate predicted by general relativity if gravitational wave emissions were occurring.
The second major observation came in September 2015, despite the immense hurdle posed by the detection of gravitational waves, that is, their extremely weak effect. Passing gravitational waves can easily pass unnoticed because of the very minimal effect they have on objects. The task of detecting the direct effect of gravitational waves on an object was deemed impossible until LIGO was finally built.
LIGO (Laser Interferometer Gravitational Observatory) – another imaginative use of acronyms by physicists – is a pair of observatories in the United States built to detect gravitational waves. Unlike conventional observatories, LIGO does not consist of a telescope or similar devices. The observatory has two large arms, each measuring four kilometres in length, perpendicular to each other.
Laser Interferometers consist of a laser beam that is split into two with a ‘beam splitter’. The two laser beams also run perpendicular to one another, in each of the arms. Any change in the distance travelled by the laser beams results in the two beams no longer being ‘in-step’ with each other, thus creating an interference pattern (hence the term interferometers’). The whole idea is that if a gravitational wave passes through the observatory, the observatory arms will expand and contract, resulting in a difference in the distance travelled by the two laser beams.6
The differences measured are incredibly small. Gravitational waves will cause the observatory arms to change in length by only about a fraction of the size of a proton (0.0000000000000000001 metres). Another way to look at this minute observation and the remarkable accuracy of the LIGO is that it can measure the distance between the sun and the nearest star Proxima Centauri, which is about 4.25 light years away, to a level of about the width of a human hair.7 LIGO is undoubtedly the most precise measuring device ever built by humans.
On September 14, 2015 at 5:51 a.m. Eastern Daylight Time (09:51 UTC), Laser Interferometer Gravitational-wave Observatory (LIGO) detectors picked up evidence of gravitational waves.8 Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second, during the merger of two black holes to produce a single, much bigger, rotary black hole. This collision of two black holes had been predicted but never detected. Based on the observed signals, LIGO scientists estimate that the black holes for this event were about 29 and 36 times the mass of the sun, and the event took place 1.3 billion years ago.
Why Are Gravitational Waves Important?
The discovery of gravitational waves is a very important step in our understanding of the universe. It has opened up a new window which was closed until recently. We can now listen to these waves and thereby expand our understanding of the universe, obtaining insights into the behaviour of massive objects such as black holes and neutron stars.
It is interesting that this discovery comes at a time when the scientific community is realising how little they know about the universe. Over the last 100 years, we have taken giant leaps in our understanding of the universe, how it works, what is it made up of and how it came into being. But it seems that with every new discovery, instead of gaining complete understanding, we simply realise how little we know.
Who has created seven heavens in harmony. No incongruity canst thou see in the creation of the Gracious God. Then look again: Seest thou any flaw? Aye, look again, and yet again, thy sight will only return unto thee confused and fatigued.9
After thousands of years of wondering about the sky, trillions of dollars spent in research and missions to outer space, we still only have a minimal understanding of the universe; since all of the observable objects such as stars, planets, galaxies, etc., account for only 4% of the universe.10 The rest, in an ingenious naming scheme, is referred to as ‘dark matter’ and ‘dark energy’! We know little to nothing about this ‘dark universe’, which makes up the majority of what we call space. The new window opened up by the detection of gravitational waves may provide us further insights into how the universe works and what it is made up of. Or perhaps with this new looking glass, we may simply realise that we know and understand even less.
In our pursuit of complete understanding, we are constantly reminded of our limitations. Thus, the search for a decisive discovery that can finally liberate us from our earthly confines goes on. The quest continues. Little do we realise that the final authority to go beyond rests with the Creator of the Universe:
O company of Jinn and men! If you have power to go beyond the confines of the heavens and the earth, then do go. But you cannot go save with authority.11
1. The Holy Qur’an, 10:6.
2. The Holy Qur’an, 81:12.
3. The Holy Qur’an, 21:105.
4. The Holy Qur’an, 39:68.
5. The Holy Qur’an, 31:11.
6. Barish, Barry C. and Rainer Weiss, “LIGO and the Detection of Gravitational Waves,” Physics Today 52 (10), 1999.
9. The Holy Qur’an, 67:4-5.
10. “Dark Energy, Dark Matter”. NASA Science: Astrophysics. 5 June 2015.
11. The Holy Qur’an, 55:34.