Established 1961 23 Health Monday, May 7, 2018 After death, Hawking cuts ‘multiverse’ theory down to size

New hypothesis relies on string theory PARIS: With a science paper published and concludes that the cosmos is “clearly after his death, Stephen Hawking has finite”, Hertog said, though still composed of revived debate on a deeply divisive question numerous universes. for cosmologists: Is our Universe just one of many in an infinite, ever-expanding “multi- Fringe idea verse”? According to one school of thought, “It is a debate that touches on the very the cosmos started expanding exponentially foundations of cosmology,” Hertog said. after the Big Bang. In most parts, this “The underlying question is whether we can expansion or “inflation” continues eternally, achieve a deeper understanding of where except for a few pockets where it stops. the laws of nature come from, and whether These pockets are where universes like ours they are unique.” Not everyone likes the are formed-multitudes of them that are new theory. “The idea that we live in a ‘mul- often likened to “bubbles” in an ever- tiverse’ is a fringe idea in a small part of a expanding ocean dubbed the multiverse. subfield of the physics community,” said Many scientists don’t like the idea, theoretical physicist Sabine Hossenfelder of including Hawking, who said in an interview the Frankfurt Institute for Advanced Studies. last year: “I have nev- “Nobody who does er been a fan of the serious science multiverse.” If we do works with the mul- live in an ever-inflat- A complete tiverse because it’s ing multiverse, it utterly useless,” she would mean the laws said. of physics and chem- understanding The main prob- istry can differ from lem, Hossenfelder one universe to of the universe explains, is that any another, a concept multiverse theory is that scientists strug- “underdetermined” gle to accept. In his and “doesn’t contain last contribution to cosmology, Hawking- enough information to make calculations”. with co-author Thomas Hertog from the KU For detractors, a multiverse theory compli- Leuven university in Belgium-does not dis- cates our understanding of our own PARIS: In this file photo renowned cosmologist Professor Stephen Hawking attends a press conference at One World Observatory in New miss the multiverse concept, but proposes Universe. But it has its defenders too. For York, to announce a new breakthrough initiative focusing on space exploration and the search for life in the universe. — AFP dramatically scaling it down. astrophysicist Aurelien Barrau of “We are not down to a single, unique uni- Laboratory of Subatomic Physics and more predictive, a lot... stronger as a scien- who co-authored work on the multiverse The British cosmologist died at the age of verse,” the University of Cambridge quoted Cosmology in Paris, “the concept makes tific theory and therefore ultimately, we concept with Hawking, says the measure- 76 after a lifelong battle against motor neu- Hawking as saying of the paper submitted sense.” hope, testable”, he explains on the UK ment of gravitational waves can help deter- ron disease, which paralyzed him and left before his death on March 14 and published “It is remarkable that today numerous Leuven website. mine whether the theory is scientifically him unable to speak. Hawking, who once this week in the Journal of High Energy types of universe can be envisaged. Several sound Hertog hopes to use gravitational said his life goal was “a complete under- Physics. However, “our findings imply a sig- theories, reliable for some and speculative Assumptions waves, ripples in the fabric of spacetime standing of the universe”, famously over- nificant reduction of the multiverse, to a for others, lead to the prediction of a multi- Hossenfelder disagrees. She described caused by black hole collisions, supernova turned a core tenet of physics by predicting much smaller range of possible universes.” verse,” he said. For Hertog, the new theory is the new theory as just another “variant” of explosions, or the formation of the early that black holes-believed until then to The new hypothesis relies on a branch of a step in the right direction. It “makes the eternal inflation, “with some additional Universe, to test the new hypothesis he cre- devour everything in their vicinity, including theoretical physics known as string theory, cosmology based on our new theory a lot assumptions on top of it.” Thomas Hertog, ated with Hawking. light-leak radiation.—AFP