Today’s New Reason To Believe

by Dr. Jeffrey Zweerink

“Test everything. Hold on to the good.” This biblical passage underscores a central principle of the scientific enterprise. Any successful model must undergo testing that will either affirm or falsify its validity. Many scientists work diligently to provide such tests for a popular (though virtually untested experimentally) model known as string theory.

Astrophysicists Rishi Khatri and Benjamin D. Wandelt of the University of Illinois at Urbana-Champaign seek to develop an observational test for the cosmic strings (not to be confused with the strings of string theory) that result from incorporating a popular form of inflation—brane inflation—into string theory. They outline the test in a recent Physical Review article (a more lay-accessible description appears in Science Daily).

The abundant neutral hydrogen that fills the universe emits electromagnetic radiation with a specific wavelength: 21 cm. Astronomers have mapped this radiation as a function of position in the sky as shown below (see the description at the Astronomy Picture of the Day). All the structure in the image arises from material within the Milky Way Galaxy.

The hydrogen in the early universe would have produced evenly distributed 21-cm radiation (similar to the cosmic microwave background radiation). According to the research of Khatri and Wandelt, the cosmic web of strings produced during inflation will leave a signature in the 21 cm wavelength radiation which would be detectable with future instruments. However, the expansion of the universe will have redshifted the radiation roughly one hundred times to a wavelength around 21 meters. To make measurements precise enough to detect the cosmic string signature would take a square array of radio telescopes more than 100 kilometers on a side!

This daunting technical challenge demonstrates the difficulty in testing string theory. However, the rewards are worth the effort because the detection of cosmic strings would reveal to scientists the energy where gravity and quantum mechanics unify. While these tests may lie far in the future, RTB anticipates that the outcome of such tests will further demonstrate the fine-tuning (necessary for life) in the fundamental laws of physics that govern our universe.

by Dr. Jeffrey Zweerink

NASA scientists recently published a stunning reproduction of the Milky Way Galaxy using data taken with the Spitzer telescope. As seen in the image below, two large spiral arms emanate from a central bar and encompass a number of smaller arms and substructure.

The fact that the Sun resides in a spiral galaxy instead of the more common elliptical galaxies highlights a number of design characteristics essential to life.

First, stars in elliptical galaxies generally have more radial orbits that frequently take the stars in close to the center of the galaxy. The density of stars in galactic centers causes large gravitational disturbances to any putative planetary system around such stars. In contrast, spiral galaxy stars exhibit more circular orbits that significantly decrease the possibility of gravitational disturbances from other stars.

Second, the spiral structures reflect regions of higher density stars and the region between the spiral structures exhibits a lower density. The Sun’s orbit in the Milky Way minimizes the number of passages through the spiral arms which, in turn, minimizes the chance for gravitational disruption of the planetary orbits.

Third, and perhaps most importantly, the existence of the spiral arm structure goes hand-in-hand with ongoing star formation. However, for a galaxy to continue forming new stars for more than ten billion years, it must continually receive new supplies of gas to replenish the gas used up by previous stars.

A paper published in the Astrophysical Journal found evidence that shows where the Milky Way received its supply of fresh gas. Using a detailed study of the stars in the halo around the Milky Way, a team of astronomers discovered that the halo exhibits a high degree of “clumpiness.” This clumpiness provides strong evidence that the Milky Way absorbed a large number of smaller dwarf galaxies during its history. The dynamics of these collisions would transfer the gas from the dwarf galaxies into the disk of the Milky Way, providing fuel for more star formation. In fact, it appears that such a process is occurring now in a location called the Virgo Stellar Stream.

Evidence consistent with the idea that Earth was designed to support life continues to mount. Not only does Earth orbit the right distance from a just-right star, it also resides in a just-right galaxy that collides with enough dwarf galaxies to continually form new stars and maintain its spiral structure. But, the collisions are not so frequent that they disrupt the planets orbiting around the sun.

by Jeff Zweerink

One biblical message Reasons To Believe consistently echoes is the mandate to weed out false ideas by testing everything. Jeremiah 33:25 makes a testable statement about the laws which govern heaven and earth, namely that they do not change. Two teams of scientists have developed the most precise clocks to date. In doing so, they have provided a powerful way to test for any variation of one of those physical laws, the electromagnetic force.

For years, atomic clocks that used a transition in cesium atoms stood as the best time-keeping devices available. However, the precision of atomic clocks depends on the size of the transition, with larger transitions giving better precision (assuming all other effects remain equal). Two papers recently published in Science describe new atomic clocks based on optical transitions five orders of magnitude larger than the microwave transitions in cesium.

The clock from one group uses neutral strontium atoms and checks the precision of the clock with another clock that uses calcium atoms. The other group built their clocks from single aluminum and mercury ions. Both clocks exceed the precision of the best cesium clocks.

All atomic transitions depend on the fine-structure constant, which also determines the strength of the electromagnetic force. Repeated tests over one year of observations with the single-ion clocks constrain variations in the fine-structure constant to less than two parts in one hundred million billion per year.

Other groups have used black holes to constrain variations in the fine-structure constant and have achieved similar results. Furthermore, observations of distant quasars (described in the 2006 Breakthroughs booklet) demonstrate that the value of the fine structure constant early in the universe matches today’s value.

Thus, continued testing affirms one critical aspect of RTB’s cosmic creation model. We live in a universe governed by constant laws of physics.