From Eurekalert:
The team, led by UA astronomer Peter A. Milne, discovered that type Ia supernovae, which have been considered so uniform that cosmologists have used them as cosmic “beacons” to plumb the depths of the universe, actually fall into different populations. The findings are analogous to sampling a selection of 100-watt light bulbs at the hardware store and discovering that they vary in brightness.
“We found that the differences are not random, but lead to separating Ia supernovae into two groups, where the group that is in the minority near us are in the majority at large distances — and thus when the universe was younger,” said Milne, an associate astronomer with the UA’s Department of Astronomy and Steward Observatory. “There are different populations out there, and they have not been recognized. The big assumption has been that as you go from near to far, type Ia supernovae are the same. That doesn’t appear to be the case.”
The discovery casts new light on the currently accepted view of the universe expanding at a faster and faster rate, pulled apart by a poorly understood force called dark energy. This view is based on observations that resulted in the 2011 Nobel Prize for Physics awarded to three scientists, including UA alumnus Brian P. Schmidt. More.
Rob Sheldon kindly writes to say,
The 2011 Nobel prize in physics was awarded to Perlmutter, Schmidt and Riess for “proving” that the universe was accelerating. Since the Big Bang happened 13.7 billion years ago, the only thing that might account for this acceleration was a larger volume. Another way to say it is that if spacetime has a pressure then the bigger it got the more it expanded. Yet another way to view this term is as a “anti-gravity” term to balance gravity. That’s why Einstein put it into his equation–because he wanted the universe to be unchanging, eternal and static. DeSitter proved that this was unstable to collapsing at the slightest perturbation, but Hubble showed that the galaxies were moving away from each other–e.g., not static at all. Einstein removed the term, supposedly calling it “his greatest mistake.” But by the 1970’s, theorists were putting it back in. For one thing, the galaxies were distributed unevenly throughout the sky like a lace tablecloth, and no one knew why there were these gigantic holes or voids with no galaxies. Only by putting back in some “anti-gravity” was it possible to simulate the voids in the cosmology models. Therefore when Perlmutter and colleagues used the “calibrated” Type Ia supernova to estimate distances–since every SNIa was supposed to be the same intrinsic brightness–then they could map distance (red shift) with brightness, and see what the universe had been doing. Sure enough, the most distant, red-shifted galaxies were also the faintest by <1% or so, and Perlmutter argued that this could only be caused by the acceleration of the universe and anti-gravity.
Now many people asked. What about dust? How about variations in SNIa brightness? How about magnetic field? Maybe stars were less “metallic” in the distant past and this made them fainter? “No,” said Perlmutter, “we took all that into account and it doesn’t explain it. The only alternative is anti-gravity.”
This is argument by exhaustion. This is why Global warming is true, because “We took into account all other natural forms of warming, so the remainder must be anthropogenic.” This is why Darwin is true, “We took into account all other explanations of change over time, and the remainder must be evolution.” This is why there are no man-eating tigers in my town, because I have a lucky charm that prevents them from coming within 10 miles of me.
Anyway, after awarding the Nobel prize about ten years after Perlmutter’s paper was peer reviewed, we now have evidence that all SNIa are not created equal, but some are intrinsically more bright than others, and the ones that he was looking at were intrinsically fainter.
Thoughts?
Note: Man-eating tigers in the Ottawa, Canada region had better have several really heavy winter coats of hair. Nothing else will save them.
See also: Dark Energy Mission
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