Un modelo sin principio ni fin

Desde los rastros conservados de las sociedades neolíticas, pararse de noche y mirar al cielo ha abierto interrogantes irresueltos. En cierto modo, las sociedades antiguas, tan pronto alcanzaron la escritura, o alguna forma de transmisión del conocimiento, nos legaron un espectro de postulados no muy lejanos de lo que astrónomos, físicos y matemáticos proponen hoy. Tanto el modelo hindú de un universo que se expande y se contrae, como el bíblico con un comienzo, han tenido a través del tiempo contínuos refinamientos. La explosión de la observación astronómica y la capacidad de cómputo, la observación de fenómenos inesperados, la ratificación de la infinita fragilidad de nuestro pequeño ecosistema, sólo han ahondado la radical ignorancia sobre el alcance, orígen y destino de nuestro universo común. Sólo es posible postular modelos, y ajustarlos a la cada vez más controversial observación.

En las últimas décadas estos modelos se orientan a considerar casi como un hecho que el universo físico tiene un comienzo, y que vive una expansión que parece tender hacia el infinito, con variantes que proponen una contracción (big bang/big crunch). Teorías basadas en la observación y el cálculo matemático, mucho más rigurosas y apoyadas en mejores intrumentos que los que Demócrito, Parménides, Thales o Copérnico pudieron disponer, pero, como ellas, sólo teorías que proponen una explicación a la observación real, realizada en un período de tiempo que parece ser sólo un infinitesimal momento en el transcurso de fenómenos de una potencia que todavía tratamos de imaginar.

En este escenario, Wun-Yi Shu, de la Universidad Tsing Hua de Taiwan, ofrece otro modelo cosmológico, uno que cuestiona la idea de un principio (¿y un fin?). Sus afirmaciones son difíciles de aprehender bajo las condiciones de nuestro entorno natural, pero los números, como remotamente Pitágoras ya supiera, pueden explicar mejor las cosas. Technology Review, en sus notas de difusión, comenta:

As one of the few astrophysical events that most people are familiar with, the Big Bang has a special place in our culture. And while there is scientific consensus that it is the best explanation for the origin of the Universe, the debate is far from closed. However, it's hard to find alternative models of the Universe without a beginning that are genuinely compelling.
That could change now with the fascinating work of Wun-Yi Shu at the National Tsing Hua University in Taiwan. Shu has developed an innovative new description of the Universe in which the roles of time space and mass are related in new kind of relativity.
Shu's idea is that time and space are not independent entities but can be converted back and forth between each other. In his formulation of the geometry of spacetime, the speed of light is simply the conversion factor between the two. Similarly, mass and length are interchangeable in a relationship in which the conversion factor depends on both the gravitational constant G and the speed of light, neither of which need be constant.

So as the Universe expands, mass and time are converted to length and space and vice versa as it contracts.

This universe has no beginning or end, just alternating periods of expansion and contraction. In fact, Shu shows that singularities cannot exist in this cosmos.
It's easy to dismiss this idea as just another amusing and unrealistic model dreamed up by those whacky comsologists.
That is until you look at the predictions it makes. During a period of expansion, an observer in this universe would see an odd kind of change in the red-shift of bright objects such as Type-I supernovas, as they accelerate away. It turns out, says Shu, that his data exactly matches the observations that astronomers have made on Earth.
This kind of acceleration is an ordinary feature of Shu's universe.
That's in stark contrast to the various models of the Universe based on the Big Bang. Since the accelerating expansion of the Universe was discovered, cosmologists have been performing some rather worrying contortions with the laws of physics to make their models work.
The most commonly discussed idea is that the universe is filled with a dark energy that is forcing the universe to expand at an increasing rate. For this model to work, dark energy must make up 75 per cent of the energy-mass of the Universe and be increasing at a fantastic rate.

But there is a serious price to pay for this idea: the law of conservation of energy. The embarrassing truth is that the world's cosmologists have conveniently swept under the carpet one the of fundamental laws of physics in an attempt to square this circle.

That paints Shu's ideas in a slightly different perspective. There's no need to abandon conservation of energy to make his theory work.

Cuatro características del modelo de Wun-Yi Shu:

• The speed of light and the gravitational “constant” are not constant, but vary with the evolution of the universe.
  
• Time has no beginning and no end; i.e., there is neither a big bang nor a big crunch singularity.
  
• The spatial section of the universe is a 3-sphere, ruling out the possibility of a flat or hyperboloid geometry.
  
• The universe experiences phases of both acceleration and deceleration.
  

Los modelos cosmológicos lindan con la literatura y la filosofía. Sólo modelos, proponen una explicación, aunque al nivel actual de discusión, escapan a nuestra "razonabilidad".

El papel completo de Wun-Shi Yu se puede leer en ArXiv.org. 
La fotografía, proviene del NASA Goddard Space Flight Center, en Flickr.