On Returning to the Moon

Interesting to see that the recent debate in the pages of The Economist on whether or not we should return to the Moon has reference to the outer Solar System. The debate pits Gregg Maryniak (James S. McDonnell Planetarium, St. Louis) against Mike Gold (Bigelow Aerospace). Normally the Moon is off our agenda in these pages because of our focus on the outer system and beyond, but my friend Frank Taylor noticed that among Maryniak’s arguments for a return to the Moon was its utility as a staging point.

Specifically, Maryniak argues that in addition to its other uses, the Moon lets us get our ‘space legs’ by learning about shielding human crews and ‘living off the land’ in a deeply inhospitable place. All of this may well lead to lunar power stations or the collection of Helium-3 for fusion projects, a developing technology with profound implications. Writes Maryniak:

Once we have the ability to capture and transmit energy at the megawatt and gigawatt levels we will see fast solar system travel. By beaming power to future space travelers we can free them from the intrinsic limitations of the chemical energies embedded in their propellants. Having both abundant energy and materials available in free space will also enable such useful things as cleaning up orbital space debris and mitigating the threat of Earth impact from asteroids and comets. The use of lunar materials and later asteroid and comet resources will ultimately enable probes beyond our solar system.

The whole debate, won by Maryniak by a vote of 61 to 39 percent, is well worth reading, and is particularly worth considering in light of recent arguments by Buzz Aldrin and others that Mars is the preferable next step.

Alien Worlds on the TV

A quick note that the National Geographic Channel will be offering two shows of interest this weekend. Alien Earths is a look at exoplanet possibilities with astrobiological implications, including exotic places like those shown in the accompanying video that find ways to support life in the absence of a star.

The other show is Naked Science: Hawking’s Universe, a look at the many contributions this extraordinary physicist has made to our understanding of the universe. Check local listings for Sunday, August 23rd for these.

Dark Energy or Spacetime Waves?

I’ve been working my way through a preprint of a paper arguing that dark energy is not what many scientists think. Joel Smoller (University of Michigan) and Blake Temple (UC-Davis) believe that an expanding wave moving through spacetime could be the reason why distant galaxies appear to be accelerating as they move away from us. The dark energy debate centers on the idea that dark energy fuels the acceleration, but Smoller and Temple will have none of it. Quoted on Space.com, Temple notes:

“We’re saying there isn’t any acceleration. The galaxies are displaced from where they’re supposed to be because we’re in the aftermath of a wave that put those galaxies in a slightly different position.”

What’s interesting about this is that it allows us to explain the anomalous acceleration with the confines of classical general relativity, seeing the anomaly as not an acceleration at all, but what the authors call a ‘correction to the Standard Model due to the fact that we are looking outward into an expansion wave.” Here’s more (note that I’m quoting from the preprint, not the published paper):

Unlike the theory of Dark Energy, this provides a possible explanation for the anomalous acceleration of the galaxies that is not ad hoc in the sense that it is derivable exactly from physical principles and a mathematically rigorous theory of expansion waves. In particular, this explanation does not require the ad hoc assumption of a universe filled with an as yet unobserved form of energy with anti-gravitational properties in order to fit the data.

Those possible ‘anti-gravitational’ properties naturally arouse the interest of propulsion-minded people, implying exotic new forms of transportation. But only if the enigmatic dark energy actually exists to serve as a model. Clara Moskowitz’ story in Space.com notes how may tests the new theory will need to pass before it will become convincing. Thus Mario Livio (Johns Hopkins University), who says that a model like this must be able to predict properties of the universe that astronomers can measure, and adds “To only produce an apparent acceleration is in itself interesting, but not particularly meaningful.”

The paper is Smoller and Temple, “Expanding Wave Solutions of the Einstein Equations that Induce an Anomalous Acceleration into the Standard Model of Cosmology,” Proceedings of the National Academy of Sciences, published online August 17, 2009 (abstract). A preprint is available.