Quote:
Originally Posted by Cougar
Thanks, Fortunate. I suppose that explanation makes sense and is well accepted, but it sure sounds tenuous!
In a simple expansion of the universe, without dark energy, photons approaching a large mass -- such as a supercluster of galaxies -- pick up energy from its gravity. As they pull away, the gravity saps their energy, and they wind up with the same energy as when they started.
But photons passing through matter-rich space when dark energy became dominant don't fall back to their original energy level. Dark energy counteracts the influence of gravity and so the large masses don’t sap as much energy from the photons as they pull away. Thus, these photons arrive at Earth with a slightly higher energy, or temperature, than they would in a dark energy-free Universe.
Conversely, photons passing through a large void experience a loss of energy.
I understand the expansion would be greater after the photons have passed by a large mass, but it seems this would be an extremely small effect. Besides, this would not be true for photons traveling through regions of space that are 7 or 8 billion lightyears away, when dark energy had yet to become dominant over gravitational slowing. |
I had some of the same reservations that you express, Cougar. I look forward to more comments from the astrophysicists. Not only is the void's spatial alignment with the cool spot intriguing, but also, the question of how the size of this object (I suppose this might actually be termed a nonobject) can be so far removed from the statistical grouping of the sizes of the other known voids. The article doesn't give many numbers but leaves me with the impression that, in statistical terms, the deviation is of a completely prohibitive number of sigmas, leading one to at least entertain the notion of a new mechanism.