The dark energy press conference mentioned a couple of days ago happened yesterday, and is written up in the Times. You can also get information straight from NASA.
The basic result here is that astronomers have made a bunch of measurements of supernovae at extremely large distances, which amounts to looking at galaxies a very long time ago. From those measurements, they have made a rough measurement of the expansion of the universe at that time, and find that the mysterious "dark energy" that appears to be causing the modern universe to expand faster over time was also making the universe expand faster ten billion years ago.
This is useful information because we have absolutely no idea what the "dark energy" is, and when you're in that position, any data are good data. Given that we have no idea what causes the effect, there's no a priori reason why it couldn't change sign, sometimes speeding the expansion up, sometimes slowing it down. The fact that it had the same basic effect in the past that it does today at least limits the possible explanations somewhat.
I'm pretty much with Clifford on this one. It's interesting news, but not as interesting as the Bullet Cluster stuff. I'm not sure it really deserves a splashy press-conference rollout, but then NASA probably feels some pressure to have splashy press conferences on a regular basis, so maybe this is the best they have this month. And it is cool science.
But we don't really know all that much more about dark energy than we did yesterday at this time.
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Au contraire, we know exactly what "dark energy" is. Redshifts are depejdent upon c. The speed of light has been slowing for billions of years, making redshifts appear to accelerate. This predicts supernova, CMB and other data far better than any repulsive energy.
From the press release: "Pinpointing supernovae in the faraway universe is similiar to watching fireflies in your back yard. All fireflies glow with about the same brightness. So, you can judge how the fireflies are distributed in your back yard by noting their comparative faintness or brightness, depending on their distance from you."
When people claim that light from fireflies is constant, it shows who is in the dark.
Heh. You may "know" what dark energy is, but the scientific community as a whole recognizes that it's something that we don't know a whole lot about.
-Rob
If lightspeed were time-dependent, then E=mc^2 so too - as the fractional anomaly squared. Stellar fusion would not work and, if it did from increasingly larger or smaller masses vs. cosmological distance, binary star orbital anomalies would be trivially detectable. Age is not merely distance. Low-metallicity stars are very old indeed and some are local. A vast swath of physical constants plus Special Relativity would be tremendously dinged both there and here.
When theory contradicts observation, theory is wrong. Take a hint from Uncle Al: Being an idiot is not half way to being an idiot-savant.
Dark Energy appears to be an intrinsic property of space not a contained entity subject to dilution with expansion or change over time. The classical vacuum is empty. The quantum vacuum contains Heisenberg Uncertainy measurable as the Casimir effect, Lamb shift, Rabi vacuum oscillations, electron anomalous g-factor... Now we have another vacuum background field to manipulate. What can we do with/to it?
Hi Al: The effect on E=mc^2 on SN luminosity has been factored into a prediction curve which precisely fits the data. It means that, rather than a "Faint Young Sun" solar luminosity has been constant enough for life to evolve on Earth. If c had not changed, we would not be around to wonder about it.
There are c-dependent processes that are linear, quadratic, and of higher powers (e.g., Planck mass, length, time). You cannot make a variable lightspeed fit observation, Lyman Alpha forest to the 16 natural fission reactors in Oklo, Gabon. Spectroscopy and chemical composition won't allow it.
God did it. The Devil did it to confuse us. The universe's physical laws are constantly evolving so observation cannot be relied upon as history. Euler's equation has not been valid over all visible cosmology so mathematics cannot model observation. Maybe it was a variable vacuum permeability constant and lightspeed just played along with the joke. Or space is only recently Euclidean - that allows the Shroud of Turin not to be a transparent fraud... and we are back at the first sentence of this paragraph.
Please check the article on http://www.nowtimesite.com and read with an open mind. It is presented for discussion and if valid presents a vital perspective on the subjects covered here.
"space is only recently Euclidean"
Actually is a subject of serious discussion by theorists and experimentalist on LISA. Gravity wave signature might exist of time very close to Big Bang when dimensions beyond 4 rapidly rolled up into Calabi-Yau manifolds, and space-time became (to first order) Minkowski space. All Reimannian manifolds of dimension n can be embedded in Pseudo-reimannian (first-order Euclidean) manifolds of dimension n(n+1)/2.