Galaxy-sized lenses confirm it: the Universe is expanding faster than we ever expected

By measuring the way light bends around distant galaxies, a group of astronomers have verified earlier findings that our Universe is not only getting bigger, but expanding at a rate much faster than previously thought.

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Tau.Neutrino said:

Galaxy-sized lenses confirm it: the Universe is expanding faster than we ever expected

By measuring the way light bends around distant galaxies, a group of astronomers have verified earlier findings that our Universe is not only getting bigger, but expanding at a rate much faster than previously thought.

More…

> But there’s a problem with the Hubble constant – physicists can’t quite agree on a number.

I agree. Calculations based on the age of the universe have been merging together with calculations based on the ages of the oldest stars. But although the error bars overlap, there isn’t exact agreement.

> astronomers from the wonderfully named H0LiCOW collaboration

LOL.

> So as the brightness of the quasar shifted, astronomers could use the multiple images to calculate the Hubble constant – how rapidly the galaxies were moving away from us. Our method is the most simple and direct way to measure the Hubble constant as it only uses geometry and General Relativity, no other assumptions.

There is one other assumption, the assumption that the quasar’s intrinsic brightness stays constant with time. But the quasar’s brightness is proportional to the mass of material falling into the galactic black hole, which can vary randomly on short timescales.

There has to be at least one other uncertainty, the actual location of the quasar, ie. where it would be if there was no intervening gravitational lens.

So I don’t see how this can be considered an accurate calculation of the Hubble constant. Combining the two above, a change in the intrinsic brightness of the quasar would always lead to an overestimate of Hubble constant, and this method is indeed finding a higher Hubble constant. If they haven’t taken the intrinsic quasar variability into account then they’ve overestimated the accuracy of this method.