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Supernovae May Not Be Standard Candles; Is Dark Energy All Wrong?
StartsWithABang writes: The accelerated expansion of the Universe — and hence, dark energy — was discovered by taking the well-understood phenomenon of type Ia supernovae and measuring them out to great distances. The results indicated that they were fainter than expected, and hence more distant, and hence the Universe's expansion must be accelerating. But new results have just come out, showing that supernovae may not be standard after all. Does this mean dark energy may not be real, or that it may just be slightly weaker than we previously thought?
even the big bang theory, commonly accepted, was formulated by a belgian priest: it's basically genesis from the bible. someone stuck abrahamic religion in the middle of "science" and no one seems to question the shaky foundations.
Unlike politics where you need to reject ideas because it came from an opposing group, science doesn't care where the idea comes from if it works. The foundations of the Big Bang theory is not its history, but general relativity and the observations that back up things like the FLRW metric. History is only indirectly important in science, in that it is a great pedagogical tool for showing how an idea developed, why some ideas worked and why others failed, for teaching students the process.
Dark Energy is not a cheat, it is a placeholder. Assuming our measurements are correct, which the discussion of standard candles is challenging, some unknown source of energy is causing our Universe to expand, and that takes a lot of energy. It takes so much energy, that this energy needs to represent 80% of the Universe's total energy.
Unless you plan on challenging the First Law of Thermodynamics.
The summary has a link to a paywalled article (silly Ethan). The full article is freely available to all on the arXiv preprint server:
http://arxiv.org/abs/1408.1706
I'm peripherally involved with the supernova field, though I study only the nearby examples. There has been for years the understanding that IF a difference should arise between the nearby events that we can study well, and the distant events which appear dimly and vaguely, AND if we did not realize that such a difference existed, THEN we could reach incorrect conclusions.
Scientists in the field have worried about this for years. It's not a sudden new realization.
It's very pleasant to see that a space telescope -- SWIFT -- which was built to study one type of object (gamma ray bursts) has turned out to provide vital information on a different type (supernovae). Since it is in space, it can detect ultraviolet light, and so show us that some nearby supernovae emit different amounts of ultraviolet light, even though they appear similar in the optical region. This UV difference hints at differences in chemical composition between supernovae, which may indeed be significant when we try to study very distant events with other telescopes.
Fortunately, light from those distant events is redshifted into the optical regime, so we can use very large ground-based telescopes to see the same UV light and compare it to the nearby events.
It's a very interesting field to follow: things change on timescales of 3-5 years. And yes, we are more aware of the uncertainties in the business than some news articles might imply.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
*If* this result holds up, it doesn't sink dark energy - it will only be a small correction to the measured value using this particular probe. We have multiple, independent measurements of the existence of dark energy, from the early-universe Cosmic Microwave Background, to the late-universe feature in the galaxy distribution called the Baryon Acoustic Oscillation. In fact, for quite a few years supernova haven't been the principle method of measuring dark energy, because we've suspected issues such as this.
*If* this result hold up, and corrected measurements of dark energy from supernovae are in tension is all other measurements, then that will be interesting and require further study. However, despite having the confirmation of the existence of dark energy for several years, we haven't measured its exact properties very well yet. These corrections will probably shift things around inside known error bars.
For all the aether-claimers: we don't know what dark energy is. We've observed an acceleration to the expansion of the universe and called it "dark energy". This is a name given to an observed phenomena. The Nobel Prize was awarded to the original supernovae groups because it has been *repeatedly, independently* verified, using completely different sets of cosmological probes. This is like observing and measuring the observational reality of gravity without having a theory to explain it, but that doesn't mean that gravity doesn't exist.
The neutrino was in the same state for a while -- a hypothesized, unobserved entity needed to make the equations balance. Now we have three different neutrinos plus their antiparticles.
The aether theories made some specific predictions, and even after several revisions to that, every single one was found to disagree with observation. Even if you attempt to rebrand some different new concept as an aether theory, that is just a semantics trick and doesn't change that original set of theories were found wrong.
That link starts off interesting, and by about the 5th or 6th page becomes just polemic. You need to rewrite every page after the 1st, giving more attention to your theory and less attention to lambasting others.
I *am* of the opinion that when you do this you will end up with many fewer pages, but quite possibly with some decent questions that need to be addressed. E.g., how does your theory account for the proportions of Hydorgen and Helium in the universe. Etc. Don't concentrate quite so much on problems that current theories have trouble with, and pay more attention to deriving the solutions that the current theories have apparently valid answers for. Yes, you need to point out places where your theory is better, but it's even more important to show that you can answer correctly everything that the current theories have correct.
I think we've pushed this "anyone can grow up to be president" thing too far.