Recent research has uncovered a startling fact—the universe appears to be expanding 9% faster than it should be. The European Space Agency’s Gaia mission has produced a figure for the Hubble constant (the rate at which the universe is expanding) by observing the flickering of a specific type of star and so deducing their original luminosity, which then allows scientists to calculate how far they have travelled since their birth. This new data has produced a Hubble constant value of 73, which means that galaxies are travelling away from us 73km per second faster with each extra megaparsec (roughly 3.3 million light-years) of distance between us.
However, scientists have also calculated the Hubble constant from observations of the Cosmic Microwave Background—lingering radiation from the Big Bang—arriving at a Hubble value of 67. This discrepancy has proved a puzzle for physicists, as the Hubble constant is meant to be a cornerstone of cosmology. Adam Riess, who led the latest analysis of the situation, commented, “if this continues to hold up we may be dealing with what we call new physics of the universe.” So what’s the answer to this conundrum? One suggestion is that so-called dark energy, which is believed to speed up the expansion of the universe, is exerting more and more power. Others propose that a new, unknown type of neutrino may be interfering with calculations. As yet, however, the question mark remains.
Applicants for Physics or Natural Sciences, especially those interested in cosmology and astrophysics, should be aware of established theories underpinning our understanding of the universe as well as recent developments and unanswered questions. They should think about what current scientific issues interest them in particular, and be prepared to talk about them in an interview.