Is the entire universe really no more than a hologram?
Stephen Hawking explained how, thanks to quantum physics, time in a sense runs backwards
ON THE ORIGIN OF TIME: STEPHEN HAWKING’S FINAL THEORY by Thomas Hertog 352pp, Torva, T£16.99 (0844 871 1514), RRP£20, ebook £9.99
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“Who knows where the time goes?” asked Sandy Denny, though as good a question is where it came from in the first place. According to the standard picture of modern cosmology, we are encouraged to think that the Big Bang, roughly 13.7 billion years ago, created time itself along with space, so that it is meaningless to talk of what came before it.
In this sense, time is like a compass direction. Once you are at the South Pole, you cannot walk any further south. Similarly, once you’ve journeyed back in time to the Big Bang, there is no further left to travel. It’s the beginning of the idea of beginning.
This answer has not always satisfied scientists, some of whom prefer to think of our cosmos bubbling into existence from elsewhere and elsewhen. This idea, however, requires a multiverse – a higher sphere of many (perhaps infinitely many) universes, constantly being born from a seething quantum sea – a concept toyed with in the Oscar-winning, universe-hopping romp Everything Everywhere
All at Once.
It’s an idea to which our very own celebrated black-holebotherer Stephen Hawking was hostile. The multiverse, he once remarked to his protégé and collaborator Thomas Hertog, was “outrageous”.
As Prof Hawking noticed, the notion of an infinite number of universes seems to violate Occam’s Razor, which states that entities should not be needlessly multiplied just to prop up an explanation. In his view, the idea shouldn’t even count as real science, on the grounds that it’s unfalsifiable: evidence of other universes completely inaccessible to our own would be impossible to come by. Not mentioned in this book, however, is the idea promoted by the AlbanianAmerican cosmologist Laura Mersini-Houghton that the birth of our universe from the multiverse might have left visible “scars” on the so-called “cosmic microwave background” – the fossil echo of the Big Bang that still permeates the sky.
So, On the Origin of Time gentle polemic, selling a particular theory, but no less rich and fascinating for that. The Belgian cosmologist Hertog, a theoretical physicist at KU Leuven university, draws a vivid and philosophical picture of the evolution of beginning-times theorising in the latter half of the 20th century, including the changing opinions of Hawking himself. It alternates between gnomic conversations over tea with Hertog’s famous late mentor and deliciously mind-bending ideas, such as that time itself stops inside a black hole, meaning that to enter one (if that were possible before you were torn apart by gravitational forces) would be to experience the last moment.
In the intriguing cosmological picture that emerges here, joint brainchild of Hawking and Hertog,
what we call the “laws of physics” themselves evolved and changed as the early universe cooled. They are therefore, as Hertog puts it poetically, simply “frozen accidents”, not amenable to any more fundamental explanation. So much for the kind of “Grand Unified Theory” of physics that Hawking had looked forward to in A Brief History of Time (1988) but then later abandoned.
What’s more controversial is the view that time must be thought of in some ways as running backwards. Science, you see, is the name we give to the activity of some bits of the universe (the ones we call “human scientists”) looking at other bits. According to Hertog and Hawking, what we observe today retrospectively calls into being the universe’s whole past, because of the quantum rule of indeterminacy (that being the rule that things are not definitively one way or another until measured). It’s a form of cosmological idealism in which fuzziness increases with distance: as we look ever further back in time, the universe becomes, as it were, more and more lowresolution, until we arrive at the singularity of the Big Bang, where information runs out.
Most striking, perhaps, is how willing Hertog is to bite the bullet of backwards causation, in which, as he explicitly says, “the past [is] contingent on the present”. He does not even shy away from accepting that this view is teleological, implying as it does that the universe was always somehow aiming at the glorious bio-friendly present, so that there could be theoretical physicists in Leuven to study it.
It can all sound quite hippyish in précis, and often in detail too, especially when Hertog asserts that the entire universe is also a holographic projection. In that case, it turns out, we don’t need to worry about the origin of time because time itself is “illusory”. This recalls Einstein’s picture of the “block universe”, in which there was no flow of time as we seem to experience it.
It also furnishes a kind of cosmic therapy: picturing ourselves as essential enablers of the evolution of the universe, or so Hertog argues, “counters the relentless alienating forces of modern science”. I’m not sure that comforting thought alone will be sufficient to persuade the antivaxxers and the Flat Earth crew.
Eccentrically inspirational as it may be, Hertog’s peroration also shows how difficult it is for us to let go of time as a fundamental concept. Shortly after he declares that time is in some sense not real, he’s seen continuing to use time-based vocabulary such as “when” and “become” and “gradually” to describe the goings-on down there in the quantum realm. It’s not so easy, after all, to get rid of the old “first this, then that”.