New Lower Limit for Gravitational Wave Energy Density

New Lower Limit for Gravitational Wave Energy Density

For lay people, gravity is the most familiar of the fundamental forces of physics. Not a moment goes by where one does not feel the strong pull of gravity toward the center of the earth. Nor is there any other force of physics that humans consider more persistent and reliable. From a physicist’s perspective, though, gravity is the least understood of the fundamental forces. Unlike with the other forces, researchers have yet to detect either the waves or the particles associated with the force of gravity.

Gravity’s extreme frailty makes it difficult for physicists to achieve the desired detection. The gravitational force constant measures ten thousand trillion trillion trillion times weaker than the electromagnetic force constant. It is this feebleness that makes gravity waves almost impossible to detect. However, this apparent weakness presents astronomers with a remarkable and unique opportunity to probe the cosmic creation event and cosmic design.

The more weakly a particle interacts, the earlier in cosmic history it detaches itself from the primordial plasma. For photons the detachment time occurs 380,000 years after the cosmic creation event. Thus, photons seen in the cosmic microwave background (CMB) radiation reveal to astronomers a true picture of the universe when it was only 380,000 years old. However, the universe is opaque to electromagnetic radiation during its first 380,000 years. Because the gravitational force constant is so much weaker than the electromagnetic force constant associated with photons, a map of the gravitational wave radiation would give astronomers a true picture of the universe when it was trillions of trillions of trillions of times younger than 380,000 years.

Thanks to several improvements made a little more than two years ago to the Laser Interferometer Gravitational-Wave Observatory (LIGO), detection of gravity waves is coming within reach. To test the efficacy of these improvements, the LIGO team spent an entire month of continuous observations. With these initial observations the researchers demonstrated that the improved LIGO was in good working order. They also determined that the energy density from gravitational waves during the early history of the universe (at most) amounted to no more than 0.000065 of the total density of the universe.1

This initial success motivated the team to conduct a much longer, and hence much more sensitive, observational test. At the same time another opportunity arose. The European Gravitational Observatory (EGO) had also been improved, so the LIGO and EGO teams decided to collaborate. The alliance linked the three LIGO detectors in Louisiana, Washington, and Germany with the EGO detector near Pisa, Italy, to increase the overall sensitivity to gravitational wave detection.

In the August 20 issue of the international science journal, Nature, the LIGO-EGO collaboration reported on their results from a two-year-long observational run.2 They established an upper limit for the energy density from gravitational waves in the universe’s early history that was ten times superior to the earlier result. They showed that this energy density could be no more than 0.0000069 of the total cosmic density.

Such a low limit to the gravitational energy density more firmly establishes the standard big bang creation model in two different ways. First, if the gravitational energy density amounts to no more than about a hundred thousandth of the total cosmic density, then that puts the big bang model’s prediction of an abundance of helium in the universe in excellent agreement with the amount astronomers observe.3 Second, the low limit to gravitational energy density eliminates a whole class of speculated alternatives to the standard big bang creation model, in particular, several conjectured effects of string theory that predict significant pre-big-bang physical events.4

Additional proof for the standard hot big bang creation event yields enormous theological implications. Until the twentieth century, the Bible was the only text teaching all of the fundamentals of big bang cosmology (causal Agent beyond space and time, beginning of space and time, beginning of matter and energy, continuous cosmic expansion, constant laws of physics, matter and energy confined to the cosmic surface and continuous cosmic cooling).5 The Bible’s correctly predicted details of big bang cosmology can only be explained if the Bible’s authors were supernaturally inspired by the One who created the universe.

More opportunities to prove the supernatural inspiration of the Bible lie just around the scientific corner. An upgrade to LIGO and EGO scheduled for completion by 2013 with observations known as Advanced LIGO to begin in 2014 will yield results about a thousand times more sensitive. Cosmologists finally will possess their Holy Grail—a detailed picture of the universe just the tiniest of a split nanosecond after the cosmic creation event and by far the most definitive test of the details of cosmic creation and of the cosmic Creator.

  1. B. Abbott et al., “Searching for a Stochastic Background of Gravitational Waves with the Laser Interferometer Gravitational-Wave Observatory,” Astrophysical Journal 659 (April 20, 2007): 918-30.
  2. B.P. Abbott et al., (The LIGO Scientific Collaboration and the Virgo Collaboration), “An Upper Limit on the Stochastic Gravitational-Wave Background of Cosmological Origin,” Nature 460 (August 20, 2009): 990-94; Marc Kamionkowski, “Gravity Ripples Chased,” Nature 460 (August 20, 2009): 964-65.
  3. D. N. Spergel, et al, “Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Cosmology,” Astrophysical Journal Supplement Series 170 (June, 2007): 384-85.
  4. M. Gasperini and G. Veneziano, “The Pre-Bib-Bang Scenario in String Cosmology,” Physics Reports 373 (January, 2003): 1-212; R. Brustein, M. Gasperini, and G. Veneziano, “Peak and End Point of the Relic “Graviton Background in String Cosmology,” Physical Review D 55 (March 15, 1997): 3882-85.
  5. Hugh Ross, “Big Bang—The Bible Taught It First,” The Creator and the Cosmos, 3rd ed. (Colorado Springs: NavPress, 2001), 23-29.