Supernova Observations Show Strength of Gravity Unchanged Over Cosmic Time

Supernovae Observations Show Strength of Gravity Unchanged Over the Last Nine Billion Years

Artist impression of Type Ia supernovae. Credit: CAASTRO/Swinburne Astronomy Productions

In a newly published study, researchers at Swinburne University of Technology in Melbourne analyzed the light given off by 580 supernova explosions in the nearby and far Universe, revealing that the strength of gravity has remained unchanged over cosmic time.

Australian astronomers have combined all observations of supernovae ever made to determine that the strength of gravity has remained unchanged over the last nine billion years.

Newton’s gravitational constant, known as G, describes the attractive force between two objects, together with the separation between them and their masses. It has been previously suggested that G could have been slowly changing over the 13.8 billion years since the Big Bang.

If G has been decreasing over time, for example, this would mean that the Earth’s distance to the Sun was slightly larger in the past, meaning that we would experience longer seasons now compared to much earlier points in the Earth’s history.

But researchers at Swinburne University of Technology in Melbourne have now analyzed the light given off by 580 supernova explosions in the nearby and far Universe and have shown that the strength of gravity has not changed.

“Looking back in cosmic time to find out how the laws of physics may have changed is not new” Swinburne Professor Jeremy Mould said. “But supernova cosmology now allows us to do this with gravity.”

A Type 1a supernova marks the violent death of a star called a white dwarf, which is as massive as our Sun but packed into a ball the size of our Earth.

Our telescopes can detect the light from this explosion and use its brightness as a ‘standard candle’ to measure distances in the Universe, a tool that helped Australian astronomer Professor Brian Schmidt in his 2011 Nobel Prize winning work, discovering the mysterious force Dark Energy.

Professor Mould and his PhD student Syed Uddin at the Swinburne Center for Astrophysics and Supercomputing and the ARC Center of Excellence for All-sky Astrophysics (CAASTRO) assumed that these supernova explosions happen when a white dwarf reaches a critical mass or after colliding with other stars to ‘tip it over the edge’.

“This critical mass depends on Newton’s gravitational constant G and allows us to monitor it over billions of years of cosmic time – instead of only decades, as was the case in previous studies,” Professor Mould said.

Despite these vastly different time spans, their results agree with findings from the Lunar Laser Ranging Experiment that has been measuring the distance between the Earth and the Moon since NASA’s Apollo missions in the 1960s and has been able to monitor possible variations in G at very high precision.

“Our cosmological analysis complements experimental efforts to describe and constrain the laws of physics in a new way and over cosmic time.” Mr Uddin said.

In their current publication, the Swinburne researchers were able to set an upper limit on the change in Newton’s gravitational constant of 1 part in 10 billion per year over the past nine billion years.

The ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) is a collaboration between The Australian National University, The University of Sydney, The University of Melbourne, Swinburne University of Technology, the University of Queensland, The University of Western Australia and Curtin University, the latter two participating together as the International Centre for Radio Astronomy Research. CAASTRO is funded under the Australian Research Council Centre of Excellence program, with additional funding from the seven participating universities and from the NSW State Government’s Science Leveraging Fund.

Publication: Jeremy Mould and Syed A. Uddin, “Constraining a Possible Variation of G with Type Ia Supernovae,” 2014, Astronomical Society of Australia; DOI:10.1017/pasa.2014.9

PDF Copy of the Study: Constraining a possible variation of G with Type Ia supernovae

Source: Swinburne University of Technology

Image: CAASTRO/Swinburne Astronomy Productions

1 Comment on "Supernova Observations Show Strength of Gravity Unchanged Over Cosmic Time"

  1. Madanagopal.V.C | March 25, 2014 at 10:14 am | Reply

    The fact that gravitational constant ‘G’ is invariant over cosmic time throws some interesting inferences. The electronic constants for the charges of electron, positron,and quarks like e-1, e+1, e+2/3, e-2/3,e-1/3, e+1/3 etc and color charges or strong forces unit constants like Red, anti-red, green, anti-green, blue, anti-blue and weak forces Bosons , show that Bosons which don’t occupy volume or space, and which can overlap one over the other HAVE GOT A BASIC CURRENCY IN EACH OF ITS KIND. While G and electro-weak forces of W+,W-and Z are basically indivisible units, and for electro-magnetic force carriers they are either e+1/3, or e-1/3 taken as a unit. The force carriers ‘G’ overlaps over one another in proportion to the square of the distance producing a strong field very near the object and weak field over large distances. The electro-magnetic forces e-1/3 or e+1/3 are already very strong units and they die out in a short distance square measurements.For Strong forces single units of Red,Blue and Green, only if they overlap in threes shows strong force for very ultra-short nuclear distances. The same is true for Weak forces dipoles and they stretch to slightly bigger Angstrom distances. The lesson is that at the time of Big Bang nearly 10^19Gev got disseminated into these currency units. The other strange but very important counterpart, viz., Higgs Boson, combined only with two types of Bosons like electro-magnetic, and strong forces to MATERIALISE into visible universe. Their association with ‘G’alone, viz., gravity would have probably created the evading DARK MATTER. The birth of Lepton (visible particle) from Boson (invisible overlapping particle)from Big Bang birth is evident. But you cannot rule out invisible universe of Dark Matter and Dark energy making (96%)which wields very strong gravity of gravitons on the(4%) real universe – So apart form unification of four forces, the dissemination of forces into their unit parts is also important in the future STANDARD MODEL OF PARTICLES- LEPTONS. The conversion of Mass to Energy in Einstein’s mass-energy relation like E=mc^2 speaks of releasing locked energy only. But there is a coversion factor for leptons to Bosons also and the equation should be of very high order at the time of Big Bang. Even our CERN is inadequate to get that force. Thank You.

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