WHERE DOES TIME COME FROM?
How black holes will shed light on the fourth dimension and the various theories about time
“IT OCCURRED TO ME THAT THE FLOW OF TIME WAS REALLY A GRADUAL ADDITION OF NEW MOMENTS OF TIME, NEW ‘NOWS’”
As science stories go, it was huge in every sense: the first-ever detection of gravitational waves, ripples in the very fabric of space and time, triggered by the collision of two black holes far beyond the Milky Way.
Gravitational waves were predicted by Einstein a century ago and picked up in September 2015 by colossal laser detectors in the United States. Now, they are being hailed as a whole new way to observe the Universe. And one physicist believes they may soon allow scientists to witness a truly mind-boggling event: the emergence of time.
According to Prof Richard Muller of the University of California, Berkeley, when black holes collide they do more than disrupt the space around them. They also create what he calls “nows”: brief new instants of time.
It’s an astonishing idea, but according to Muller it’s no sci-fi fantasy. Within a few years, he says, the same detectors that discovered gravitational waves may provide hard evidence of instants of time being created in deep space.
Such claims put Muller at the forefront of research aimed at understanding this most ineffable component of our Universe. From Aristotle to Einstein, some of the most brilliant minds in history have pondered the nature of time, only to come away baffled. Around 1,500 years ago, the philosopher Augustine captured the views of many scientists, and his words continue to resonate today: “What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know.”
Muller believes recent advances in physics make it possible to cut through the confusion to reveal the truth. At present, that truth is based on Einstein’s relativity. According to this, the common-sense view that we inhabit a Universe with three dimensions of space, with time flowing from past to future, is an illusion. Einstein insisted that space and time are just different aspects of one unified whole that he called ‘space-time’.
While Einstein was in his twenties, he went on to show that this leads to a host of unexpected effects. Objects that zip past at close to light speed will appear distorted, and compressed in the direction of travel. Clocks moving at such speeds will appear to run slow.
Despite their outlandishness, the predictions of relativity have all been tested – and all have proved correct. Yet there remains something odd about the supposed ‘oneness’ of space and time. As Muller points out, there’s a simple experiment anyone can perform: “We can stand still in space – but not in time”.
There are other puzzles too. The fundamental laws of nature take no account of the flow of time, giving the same answer whether time flows forwards or backwards. Yet we’re surrounded by events that seem to show that time really does have an ‘arrow’ pointing from the past to the future, from the erosion of mountains to the decay of all living things.
Muller started pulling together all his thoughts on this, in order to write a book. He then had a flash of inspiration. “As I wrote and continued to think… it suddenly occurred to me that the flow of time was really a gradual addition of new moments of time, new ‘nows’.”
But what could possibly create packets of time? Muller found the answer in the fundamental unity of space and time. Ever since the discovery of the
expansion of the Universe more than 90 years ago, scientists have had to accept that space really can be created out of nowhere. And as space and time are just different aspects of the same thing, that means time can be created as well.
“Every moment the Universe gets a little bigger, and there is a little more time,” explains Miller.
That, in turn, provides a stunningly simple explanation for the supposed flow of time: “The forefront, expanding edge of time is what we refer to as now, and the flow of time is the continual creation of new nows,” he says. “It all fits together.”
Muller wasn’t content to stop there, with just an intriguing idea. He wanted to find a way of putting it to the test. And he could see no way to do it. “I had some ideas based on cosmology, but I couldn’t figure out how to actually perform the tests, at least within my expected lifetime.” So Muller pressed on with writing his book, which appeared last year as
Now: The Physics Of Time.
But just as he was finishing his book, he learned of the discovery of gravitational waves by the scientists at the Laser Interferometer Gravitational-wave Observatory (LIGO). That changed everything.
One of LIGO’s mirrors, which are used to detect gravitational waves
Prof Richard Muller thinks black holes could hold the secret to detecting the creation of time
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Sky map of the southern hemisphere, revealing the location of the source of the gravitational waves detected by LIGO
Wavelet graph of two black holes merging, as detected by LIGO in 2015