
Astronomy experiments could soon test an idea developed by Albert Einstein almost exactly a century ago, scientists say.
Tests using advanced technology could resolve a longstanding puzzle over what is driving the accelerated expansion of the Universe.
Researchers have long sought to determine how the Universe's accelerated expansion is being driven. Calculations in a new study could help to explain whether dark energy- as required by Einstein's theory of general relativity - or a revised theory of gravity are responsible.
Einstein's theory, which describes gravity as distortions of space and time, included a mathematical element known as a Cosmological Constant. Einstein originally introduced it to explain a static universe, but discarded his mathematical factor as a blunder after it was discovered that our Universe is expanding.
Research carried out two decades ago, however, showed that this expansion is accelerating, which suggests that Einstein's Constant may still have a part to play in accounting for dark energy. Without dark energy, the acceleration implies a failure of Einstein's theory of gravity across the largest distances in our Universe.
Scientists from the University of Edinburgh have discovered that the puzzle could be resolved by determining the speed of gravity in the cosmos from a study of gravitational waves -space-time ripples propagating through the universe.
The researchers' calculations show that if gravitational waves are found to travel at the speed of light, this would rule out alternative gravity theories, with no dark energy, in support of Einstein's Cosmological Constant. If however, their speed differs from that of light, then Einstein's theory must be revised.
Such an experiment could be carried out by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US, whose twin detectors, 2000 miles apart, directly detected gravitational waves for the first time in 2015.
Experiments at the facilities planned for this year could resolve the question in time for the 100th anniversary of Einstein's Constant.
The study, published in Physics Letters B, was supported by the UK Science Technology Facilities Council, the Swiss National Science Foundation, and the Portuguese Foundation of Science and Technology.
Dr Lucas Lombriser, of the University of Edinburgh's School of Physics and Astronomy, said: "Recent direct gravitational wave detection has opened up a new observational window to our Universe. Our results give an impression of how this will guide us in solving one of the most fundamental problems in physics."
Explore further:
Violations of energy conservation in the early universe may explain dark energy
More information:
Lucas Lombriser et al, Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure, Physics Letters B (2017). DOI: 10.1016/j.physletb.2016.12.048
Seeker2
Important difference between the speed of gravity and the speed of gravitational waves. Newtonian gravity is instantaneous because the gravitational fields of the gravitating bodies follow right along with the bodies.
manfredparticleboard
Do try to keep up and stop staring out the window.
Whydening Gyre
Seeker2
Seeker2
Whydening Gyre
It's a field generated by matter (which, in almost all cases, has differing momentum within space/time).
humy
Seeker2
Static gravitational fields don't logically imply gravity is instantaneous and doesn't travel at the speed of light.
The solar constant is also like a static field in the very narrow sense it is fairly constant. Does that imply light from the Sun is instantaneous and doesn't travel at the speed of light?
also see
https://en.wikipe...Graviton
-point; don't gravitons travel at the speed of light?
Why would they be the exception to the rule?
Seeker2
How can light not travel at the speed of light? Gravitons propagate gravitational radiation, not gravitational fields.Actually per Erik Verlinde gravitons are really phonons.
adam_russell_9615
Seeker2
TimLong2001
AmritSorli
CMBR has orgin in space where is always NOW
http://article.sc....11.html
antialias_physorg
Tired light hypothesis. Look it up. Doesn't work (even its inventor came to the conclusion).
Seeker2
antialias_physorg
He knew about spectroscopy. If tired light were true spectroscopic lines wouldn't be shifted, They are shifted. Hence: tired light doesn't work.
It didn't agree with observation. There's a name for theories that don't agree with observation: Failed theories.
Seeker2
Whydening Gyre
Light in a vacuum pretty much travels at the speed of light, regardless of wavelength (frequency)...
Therefore, these will not change the true speed of light in a vacuum. Photons travelling between 2 electrons is at the true speed of light in a vacuum.
I actually believe many scientists would think that same thing if the evidence supporting anything else could be shown with any sufficient verity.
However, it doesn't, so...
Doesn't mean that they aren't actively pursuing other potentials. That's what science is.
Whydening Gyre
Pretty close to a vacuum, in my book...
Anybody else?
Whydening Gyre
Bschott,
I believe the disconnect is in how one views the mechanism of speed of light.
At it's very core (kinda like electricity), it is photon (energy packet) xchange between mass bodies. This exchange is what actually occurs at C. Only the frequency at witch it "rotates" is is diminished as a result of a new larger number of photons now travelling together.
(I hope I am explaining this clearly enough, as i am not that experienced in relaying actual "details"...)
Seeker2
Whydening Gyre
Mass being a measure of velocity of motion, yes... And also, it happens on a scale we are not yet technologically sufficient to see... And that velocity a derivative of kinetic "charge" (spin).
Just cuz we can't see it, doesn't mean it isn't there. All a matter of scale...
It's so simple and fractal, I can hardly believe it, m'self...
Whydening Gyre
Actually, no photons, no exchange, no mass...
Bear with me, still trying to figure out what might cause the initial photon to start the reaction... The fact that they all work in concert is what's puzzling... SOMEthing had to go first.
Seeker2
Da Schneib
baudrunner
Replace all references of "gravitational waves" to "shock waves". Now picture gravity as analogous to the silk strands of a spider web. Pull one node on the perimeter of that web and the entire web accommodates the stress placed on it immediately. Now consider the web as universal in scope, and the light from that node (star) taking millions of years to get to that node's opposite perimeter.
Calculations of dark matter are done by plotting celestial bodies' motion over time. Now, those stars are definitely not where they appear to be at the present time, but their gravitational influence interacts with the other celestial bodies in real time.
Astronomers are basing their DM conclusions on calculations that are actually based on this instantaneous behavior of gravity via this snapshot process, but continue to describe "gravity waves" and DM in the context of "gravity at the speed of light". Big conundrum.
nikola_milovic_378
Mar 05, 2017