Science NewsCurated by RSF Research Staff Home > Science News > Investigation of the gravitational property of the quantum vacuum may explain the accelerating expansion of the universe. The source of dark energy is a long-standing mystery that ranks among the most enigmatic of outstanding questions in science. Since it was determined that the expansion of the universe appears to be accelerating, there has been an ongoing effort to determine the source of this expansive force. Before it was even known that the universe appears to be expanding, Einstein understood that his gravitational solution of general relativity would require some counteracting force to keep the universe from collapsing in on itself (assuming a static-state universe). Einstein introduced the cosmological constant, a term with an undefined source but which counteracts large-scale gravitational attraction that would otherwise cause a steady-state universe to collapse. With Edwin Hubble's discovery of an apparently expanding universe, the cosmological constant was dropped. However, this idea has seen a recent revival in order to explain the accelerating expansion, yet the source of the force remains undefined and the constant itself must be fine-tuned to an extreme accuracy in order to give the correct values for what is observed. Given the seeming contrived mechanism of the cosmological constant (which is one reason it was abandoned by Einstein in the first place), and the peculiarities of other potential explanations, such as scalar fields with a negative pressure, many have sought to explain the source of the accelerating expansion using principles that are already relatively known in physics but that may require a fresh new appraisal. One such method has been undertaken by the physicist William Unruh, renowned for his work describing the thermal properties of the vacuum in non-inertial frames -- whereby an observer in an accelerating frame will detect a non-zero temperature of the ambient space as the accelerating frame causes the quantum vacuum to appear to emit black-body radiation. Unruh and his doctoral students have shown that the extremely large energy density expectation value of the quantum vacuum, which is several orders of magnitude larger than the sum of the energy of every particle in the universe, is not as catastrophic as has been largely presumed. The extremely large energy density of the vacuum has lead many physicist to assume that the calculation must somehow be fallacious, although no one has been able to determine why or how this is so. Now, Unruh and his research team have shown that the spacetime fluctuations of the vacuum are almost completely balanced between expansive and contractive fluctuations of the gravitational field. There is however a slightly greater degree of the expansive fluctuations that result in a net force favoring expansion at the cosomological scale. The results suggest that there is no need for the cosmological constant and that so called dark energy may indeed be sourced in the gravitational effects of the ubiquitous energy of space -- the quantum vacuum. If free space has a net expansive force, it is interesting to speculate what spacetime geometry and torque associated with elementary particles may have on the vacuum fluctuations, whereby they result in a net quantum gravitational attractive force between matter. If it is large enough to drive apart galaxies at the cosmological scale, perhaps it is strong enough to bind subatomic particles and nuclei together at the atomic scale? Article: https://phys.org/news/2017-05-nature-great-puzzles-expansion-universe.html?utm_source=menu&utm_medium=link&utm_campaign=item-menu Detecting the space-memory signal of past gravitational wavesMay 26, 2017Bioelectrical patterns shown to be instrumental in regeneration and complex morphogenesisMay 25, 2017Astronomers Create the Largest Map of the UniverseMay 23, 2017Mysterious star resumes anomalous dimming; astronomers world-wide set to measure light coming from the systemMay 22, 2017Detection of a coherent magnetic bridge between galaxiesMay 19, 2017 Sharing is caring - please share this with your friends: Facebook Twitter If you like this content, you will love the Resonance Academy.