According to the Lambda Cold Dark Matter (Lambda-CDM) model, which is the current accepted standard for how the universe began and evolved, the ordinary matter we encounter every day only makes up around five percent of the universe’s density, with dark matter comprising 27 percent, and the remaining 68 percent made up of dark energy, a so-far theoretical force driving the expansion of the universe. But a new study has questioned whether dark energy exists at all, citing computer simulations that found that by accounting for the changing structure of the cosmos, the gap in the theory, which dark energy was proposed to fill, vanishes.
Published in 1915, Einstein’s general theory of relativity forms the basis for the accepted origin story of the universe, which says that the Big Bang kicked off the expansion of the universe about 13.8 billion years ago. The problem is, the equations at work are incredibly complicated, so physicists tend to simplify parts of them so they’re a bit more practical to work with. When models are then built up from these simplified versions, small holes can snowball into huge discrepancies.
“Einstein’s equations of general relativity that describe the expansion of the universe are so complex mathematically, that for a hundred years no solutions accounting for the effect of cosmic structures have been found,” says Dr László Dobos, co-author of the new paper. “We know from very precise supernova observations that the universe is accelerating, but at the same time we rely on coarse approximations to Einstein’s equations which may introduce serious side effects, such as the need for dark energy, in the models designed to fit the observational data.”
Dark energy has never been directly observed, and can only be studied through its effects on other objects. Its properties and existence are still purely theoretical, making it a placeholder plug for holes in current models.
The mysterious force was first put forward as a driver of the universe’s accelerated expansion in the 1990s, based on the observation of Type Ia supernovae. Sometimes called “standard candles,” these bright spots are known to shine at a consistent peak brightness, and by measuring the brightness of that light by the time it reaches Earth, astronomers are able to figure out just how far away the object is.