Now the expansion of the universe is not accelerating

In 2011 the Nobel Prize in Physics was awarded to three astronomers for their discovery, as part of two separate teams which published their results around 1998 that they claimed showed that the Universe is expanding at an accelerating rate. Also they claimed the existence of some sort of mysterious ‘dark energy’ that was driving the expansion at a faster and faster rate.

Hubble image of supernova remnant N 49 in the Large Magellanic Cloud. Credit: NASA and The Hubble Heritage Team (STScI/AURA)

Hubble image of supernova remnant N 49 in the Large Magellanic Cloud. Credit: NASA and The Hubble Heritage Team (STScI/AURA)

The interpretation of the 1998 data depended heavily on the big bang cosmological theory they applied and the assumption that it was the correct theory to describe the structure and time evolution of the Universe. It also depended heavily on the assumption that the type Ia supernova explosions that they used are reliable standard “light bulbs”, i.e. that those stellar explosions all were accurately chosen to have the same characteristic intrinsic absolute brightness.1 The latter, however, we now know is not the case.2

It has been shown that the stellar masses of the stars that result in the type Ia class of supernova are not so well-defined that they all fall within a narrow range as to give a clear standard in terms of the intrinsic brightness of the resulting explosions and hence the type Ia are not a uniform reference. Also as I have previously indicated circular reasoning was employed in the choice of the candidate supernova to be considered.2,3 The cosmology under test was used to choose the candidate Ia supernovae and then those chosen were used to test the same cosmology.

A new study, published in the Nature journal Scientific Reports, on a data set ten times larger than the original studies used (5 years ago) has been carried out.4

Now, a team of scientists led by Professor Subir Sarkar of Oxford University’s Department of Physics has cast doubt on this standard cosmological concept. Making use of a vastly increased data set – a catalogue of 740 Type Ia supernovae, more than ten times the original sample size – the researchers have found that the evidence for acceleration may be flimsier than previously thought, with the data being consistent with a constant rate of expansion. (emphasis added)

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