Tiny, Old Black Hole Shrinks the Braneworld

In previous centuries, headhunting tribes used exotic techniques to shrink the severed heads of their victims. In this century, four astronomers from the United States and Britain, led by Oleg Gnedin, have found a way to use observations of a rare astronomical body to shrink down braneworld speculations.

Branes are dimensional surfaces. [Braneworlds](https://en.wikipedia.org/wiki/Brane_cosmology) are models of the universe incorporating large extra dimensions of space. In the standard big bang creation model there are four large dimensions—length, width, height, and time. There are five or more large dimensions in the braneworlds. Some braneworld models permit alternatives to the biblical cosmic model of the universe arising from a single beginning caused by an Agent operating beyond or outside of matter, energy, space, and time, making them popular with atheists, agnostics, Hindus, and Buddhists.¹

Until recently, torsion balance laboratory experiments were the only way braneworld speculations could be tested.² Gnedin’s team showed that with the right kind of black hole a much more restrictive limit could be placed on the maximum sizes of the extra dimensions making up the conjectured braneworlds.

As Stephen Hawking proved some three decades ago, black holes eventually become white holes by shrinking under their own gravity. After enough time a black hole becomes so tiny that quantum mechanical effects dominate the gravitational forces. At that instance all matter and energy that was trapped inside the black hole quantum tunnels out. The black hole completely evaporates in a sudden, intense flash of light. The smaller the black hole, the faster it reaches the white hole evaporation event.

In the standard big bang creation model, stellar mass black holes take more than 10⁶⁰ years (more than a quadrillion quadrillion quadrillion quadrillion years) to evaporate, that is, to become a white hole. Whereas in braneworld models black holes evaporate much, much faster. The discovery of a sufficiently small, sufficiently old black hole can place severe constraints on possible braneworlds.

Astronomers recently made the first ever robust identification of a stellar-mass black hole in a globular cluster. In 2007, an astronomy team led by Thomas Maccarone discovered a compact object in the globular cluster RZ2109, which is located in the giant elliptical galaxy NGC 4472 in the Virgo cluster of galaxies.³ Based on the object’s x-ray luminosity and variability, Maccarone’s team concluded that it must be a black hole. In 2008, another astronomy team, led by Stephen Zeph, used their detailed optical spectrum of the compact object to confirm that it is indeed a black hole and that its mass is about ten times that of the Sun.⁴ Gnedin’s team took advantage of this discovery and identification to place the strongest limit to date on the size of the extra dimensions in braneworld models.⁵

Stars in globular clusters all form at about the same time. The age spread among them is no more than one billion years. Gnedin’s team determined that RZ2109 is ten billion years old. Thus, they showed that the compact object in RZ2109 is a ten-billion-year-old black hole whose mass is no more than about ten times the Sun’s mass.

These calculations allowed Gnedin’s team to establish that the maximum possible size for the extra dimensions in the hypothesized braneworlds could be no larger than 0.003 millimeters. This limit is fifteen times smaller than the best limits established by torsion balance laboratory experiments. It is small enough to eliminate any concerns that Christians might have that non-theists could exploit braneworld speculations to develop reasonable alternatives to God creating our universe independent of matter, energy, space, and time.