Do graphite whiskers in meteorites require shaving dark energy out of cosmological models?
Consider a familiar scenario. Your child lies on the couch acting unusually calm. You touch your their forehead and it feels warm. The insta-thermometer gives a reading of 101.2oF from the child’s ear. The traditional thermometer in the mouth gives a reading of 101.4oF. Without question, your child has a fever.
But does your conclusion change if you discover that the batteries in your insta-thermometer are dying?
Graphite whiskers may represent dying batteries among the evidence for dark energy in the universe. Astronomers use the brightness of Type Ia supernovae to measure the expansion rate of the universe. Because these supernovae each emit the same amount of light (after some straightforward calibrations), astronomers use the measured brightness to determine the distance to each galaxy containing the supernova. Comparing the distance with the redshift provides the expansion history of the universe. Because distant supernovae have appeared dimmer than expected, astronomers concluded that dark energy pervades the universe, causing its expansion to accelerate for the last 5 billion years.
One alternative explanation is that a “grey dust,” proposed to populate intergalactic space, absorbs the supernovae light in a way that mimics the effects of dark energy. By carefully analyzing the oldest remnants of the early solar system—namely carbonaceous chondrite meteorites—scientists from the Carnegie Institution have discovered one potential grey dust candidate. Specifically, the researchers found graphite whiskers in three different parts of the meteorite (see here).
Graphite absorbs light that is characteristic of distant supernovae very efficiently. Thus, if enough graphite whiskers were ejected from star-forming nebulae and/or supernovae out into the intergalactic medium, they might explain the dimness of Type Ia supernovae without needing to invoke dark energy. Much work remains to check the validity of this explanation, but finding the graphite whiskers was a critical first step.
In the bigger picture, the possibility of these results removing the necessity of dark energy remains small. Type Ia supernovae are not the only indicators of dark energy. Data from both the WMAP and the SDSS both provide compelling evidence for dark energy, independent of the supernovae data.
Dark energy stands as the strongest single piece of evidence for fine-tuning in the universe—evidence that effectively argues for the intervention of a supernatural Designer. While scientists may have discovered some dying batteries (the graphite whiskers), rather than shaving dark energy out of the cosmological models, this phenomenon remains charged for the long haul.