The Scars of the Last Aeon

This month’s Nobel Prize in Physics went to Francis Halzen, who spent decades turning a cubic kilometre of Antarctic ice into a detector for ghostly particles from deep space. They came. The sky does send messages, and rigour can tell them from noise. Sir Roger Penrose, the 2020 laureate, reads a stranger message there: that the universe never began and will never end. It simply cycles.

Penrose calls his idea conformal cyclic cosmology. Each universe, or aeon, expands for so long that its matter fades and its black holes evaporate, until nothing is left but light. A universe made only of light, which keeps no time and carries no ruler, cannot tell whether it is infinitely large or infinitely small, so the cold, empty end of one aeon becomes the hot, dense beginning of the next. The Big Bang, on this view, was not a birth. It was a handover.

The handover is not clean. As the largest black holes of the previous aeon finally evaporate, over a span of years written as a one followed by a hundred zeros, their last radiation is squeezed by the geometry of the crossing into single points. Those points should show up in our own sky as small warm spots in the cosmic microwave background, the faint afterglow of our Big Bang. Penrose calls them Hawking points. They are scars carried from one era into the next.

Now the fingerprint. Hawking points take their name from Stephen Hawking’s discovery that black holes are not entirely black. That discovery grew out of an argument Hawking lost to a graduate student.

In 1972 Jacob Bekenstein, born in Mexico City to Polish Jewish parents, argued in his Princeton doctorate that a black hole must have entropy, an idea that awkwardly implied it also had a temperature. Hawking thought this was wrong. A black hole emits nothing, he reasoned, so it can have no temperature. At a meeting in France that year he and several colleagues confronted the young man. Two years later Hawking’s own calculation proved Bekenstein right. The formula for a black hole’s temperature, the missing piece that made Bekenstein’s entropy consistent, is now carved on Hawking’s memorial stone in Westminster Abbey.

That same year Bekenstein could have taken a post at almost any leading university. He chose instead the new Ben-Gurion University in Be’er Sheva, then five years old, and stayed in the Negev until moving to the Hebrew University of Jerusalem in 1990. Every Hawking point, if any are real, is also in a sense a Bekenstein point.

The evidence is thinner. In 2020 Daniel An, Krzysztof Meissner, Paweł Nurowski and Penrose claimed to see them in data from the Planck and WMAP satellites, at a confidence they put at 99.98 per cent. Dylan Jow and Douglas Scott reran the analysis, giving the random simulations the same freedom to pick their most favourable scale, and the confidence fell to about 87 per cent, little more than chance. An earlier claim by Penrose and Vahe Gurzadyan, of concentric circles in the same sky, had been picked apart within days. Yet the same maps carry a signal nobody disputes, the kind Halzen would recognise. For its first 380,000 years the universe was a hot plasma through which pressure waves rang like a struck drum, and their notes are frozen into the afterglow, measured precisely by Planck. The universe demonstrably vibrates. Whether it also repeats remains, for now, a set of smudges the eye wants to read as a message.

There is an Israeli thread. In May 1988 President Chaim Herzog presented the Wolf Prize in Physics to Penrose and Hawking, for showing that Einstein’s gravity demands singularities. Israel honoured the two men who proved the universe must have had a beginning. Penrose has spent the past two decades arguing that it never really did.

The physics offers two lessons. From Jow and Scott: a country under strain sees Hawking points everywhere, and a careful citizen, like a careful cosmologist, asks how often a pattern would appear by chance before calling it a message. From the meeting in France: the junior voice can be right, and the senior one must have the grace to be corrected, as Hawking was. The observers on the border had Bekenstein’s nerve. What they lacked was a Hawking above them.

In the nave of Westminster Abbey, a few steps from Isaac Newton and Charles Darwin, Hawking lies under a slab of Caithness slate. Rings surround a dark ellipse, like matter circling a black hole, and the slate carries the formula that a graduate student’s argument led him to. Each evening the doors close and the nave falls dark. The equation stays where it is. So should the memory of the observers, who were right once and were not heeded. The nave is empty. The sky is not.