Posts Tagged ‘BOSS’

An infinite and timeless universe measured with an accuracy of 1%!

January 10, 2014

A new paper has been capturing some headlines. It is all completely beyond me and while the Abstract – written presumably in English – may be perfectly intelligible for an astronomer or a physicist, it is totally incomprehensible for me. But some of the quotations in the accompanying press release – which were picked up and reported widely in the mainstream media (here and here for example) – sounded strangely illogical.

from the Press Release

  • Today the Baryon Oscillation Spectroscopic Survey (BOSS) Collaboration announced that BOSS has measured the scale of the universe to an accuracy of one percent.
  • “One-percent accuracy in the scale of the universe is the most precise such measurement ever made,” says BOSS’s principal investigator, David Schlegel, a member of the Physics Division of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). 
  • … the BOSS results suggest that dark energy is a cosmological constant whose strength does not vary in space or time. 
  • …. the BOSS analysis “also provides one of the best-ever determinations of the curvature of space. The answer is, it’s not curved much.”
  • “One of the reasons we care is that a flat universe has implications for whether the universe is infinite,” says Schlegel.
  • … “That means – while we can’t say with certainty that it will never come to an end – it’s likely the universe extends forever in space and will go on forever in time. Our results are consistent with an infinite universe.”
  • … By 380,000 years after the big bang, however, the temperature of the expanding mixture had cooled enough for light to escape, suffusing the newly transparent universe with intense radiation, which in the 13.4 billion years since has continued to cool to today’s faint but pervasive cosmic microwave background.
  • … BOSS collaborator Beth Reid of Berkeley Lab translates the two-dimensional sky coordinates of galaxies, plus their redshifts, into 3-D maps of the density of galaxies in space. “It’s from fluctuations in the density of galaxies in the volume we’re looking at that we extract the BAO standard ruler,” she says.
  • …. The universe’s expansion history has been measured with unprecedented accuracy during the very stretch of ancient time, over six billion years in the past, when expansion had stopped slowing and acceleration began. …

At this point I gave up.

My knowledge of physics and astronomy is sadly lacking and I cannot be reconciled to a universe which is

  • an expanding universe, where
  • the expansion is accelerating, and where
  • the university is infinite, and
  • timeless, and 
  • has been “measured” to an accuracy of 1%

1% of an infinite universe ought to be infinity in my boggled mind!  Is the “ruler” expanding as well? And did time exist before the Big Bang? And if the universe is “timeless”, is time just an artificial construct? And can infinity expand without having a larger infinity?

Oh well! I’m afraid I cannot picture this universe – but I am only an engineer.

Lauren Anderson et al, The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the Data Release 10 and 11 galaxy samplesMonthly Notices of the Royal Astronomical Society, 2014.

Abstract: We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey III (SDSS-III). Our results come from the Data Release 11 (DR11) sample, containing nearly one million galaxies and covering approximately 8500 square degrees and the redshift range 0.2the baryon acoustic oscillation (BAO) feature. The acoustic features are detected at a significance of over 7σ in both the correlation function and power spectrum. Fitting for the position of the acoustic features measures the distance relative to the sound horizon at the drag epoch, rd, which has a value of rd,fid=149.28Mpc in our fiducial cosmology. We find DV=(1264±25Mpc)(rd/rd,fid) at z=0.32 and DV=(2056±20Mpc)(rd/rd,fid) at z=0.57. At 1.0 per cent, this latter measure is the most precise distance constraint ever obtained from a galaxy survey. Separating the clustering along and transverse to the line-of-sight yields measurements at z=0.57 of DA=(1421±20Mpc)(rd/rd,fid) and H=(96.8±3.4km/s/Mpc)(rd,fid/rd). Our measurements of the distance scale are in good agreement with previous BAO measurements and with the predictions from cosmic microwave background data for a spatially flat cold dark matter model with a cosmological constant.


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