**Our Universe At Home Within A Larger Universe**

Einstein-Rosen bridges like the one visualized above have never been observed in nature, but they provide theoretical physicists and cosmologists with solutions in general relativity by combining models of black holes and white holes.

by Staff Writers

Bloomington IN (SPX) Apr 07, 2010

Could our universe be located within the interior of a wormhole which itself is part of a black hole that lies within a much larger universe? Such a scenario in which the universe is born from inside a wormhole (also called an Einstein-Rosen Bridge) is suggested in a paper from Indiana University theoretical physicist Nikodem Poplawski in Physics Letters B. The final version of the paper was available online March 29 and will be published in the journal edition April 12.

Poplawski takes advantage of the Euclidean-based coordinate system called isotropic coordinates to describe the gravitational field of a black hole and to model the radial geodesic motion of a massive particle into a black hole.

In studying the radial motion through the event horizon (a black hole's boundary) of two different types of black holes - Schwarzschild and Einstein-Rosen, both of which are mathematically legitimate solutions of general relativity - Poplawski admits that only experiment or observation can reveal the motion of a particle falling into an actual black hole.

But he also notes that since observers can only see the outside of the black hole, the interior cannot be observed unless an observer enters or resides within.

"This condition would be satisfied if our universe were the interior of a black hole existing in a bigger universe," he said.

"Because Einstein's general theory of relativity does not choose a time orientation, if a black hole can form from the gravitational collapse of matter through an event horizon in the future then the reverse process is also possible. Such a process would describe an exploding white hole: matter emerging from an event horizon in the past, like the expanding universe."

A white hole is connected to a black hole by an Einstein-Rosen bridge (wormhole) and is hypothetically the time reversal of a black hole. Poplawski's paper suggests that all astrophysical black holes, not just Schwarzschild and Einstein-Rosen black holes, may have Einstein-Rosen bridges, each with a new universe inside that formed simultaneously with the black hole.

"From that it follows that our universe could have itself formed from inside a black hole existing inside another universe," he said.

By continuing to study the gravitational collapse of a sphere of dust in isotropic coordinates, and by applying the current research to other types of black holes, views where the universe is born from the interior of an Einstein-Rosen black hole could avoid problems seen by scientists with the Big Bang theory and the black hole information loss problem which claims all information about matter is lost as it goes over the event horizon (in turn defying the laws of quantum physics).

This model in isotropic coordinates of the universe as a black hole could explain the origin of cosmic inflation, Poplawski theorizes.

source: Space Daily: http://www.spacedaily.com/reports/Our_Universe_At_Home_Within_A_Larger_Universe_999.html

**Abstract - Radial motion into an Einstein–Rosen bridge**

Nikodem J. Popławski

Department of Physics, Indiana University, Swain Hall West, 727 East Third

Street, Bloomington, IN 47405, USA

Received 12 May 2009; revised 8 March 2010; accepted 9 March 2010. Editor: S. Dodelson. Available online 11 March 2010.

We consider the radial geodesic motion of a massive particle into a black hole in isotropic coordinates, which represents the exterior region of an Einstein–Rosen bridge (wormhole). The particle enters the interior region, which is regular and physically equivalent to the asymptotically flat exterior of a white hole, and the particle's proper time extends to infinity. Since the radial motion into a wormhole after passing the event horizon is physically different from the motion into a Schwarzschild black hole, Einstein–Rosen and Schwarzschild black holes are different, physical realizations of general relativity. Yet for distant observers, both solutions are indistinguishable. We show that timelike geodesics in the field of a wormhole are complete because the expansion scalar in the Raychaudhuri equation has a discontinuity at the horizon, and because the Einstein–Rosen bridge is represented by the Kruskal diagram with Rindler's elliptic identification of the two antipodal future event horizons. These results suggest that observed astrophysical black holes may be Einstein–Rosen bridges, each with a new universe inside that formed simultaneously with the black hole. Accordingly, our own Universe may be the interior of a black hole existing inside another universe.
**Keywords:** Black hole; Isotropic coordinates; Wormhole

Physics Letters B

Volume 687, Issues 2-3, 12 April 2010, Pages 110-113

paper in pdf: "Radial motion into an Einstein–Rosen bridge", by Nikodem J. Poplawski