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New Hubble data baffles cosmologists about universe’s expansion rate

The uncertainty of science: New and very firm data from the Hubble Space Telescope on the universe’s expansion rate conflicts with just-as-firm data obtained by Europe’s Planck astronomical probe.

According to Planck, the present universe should be expanding at a rate of 67 kilometers per second per megaparsec. According to Hubble, the actual expansion rate is 74 kilometers per second per megaparsec.

And according to the scientists involved, both data sets are reliable and trustworthy, leaving them baffled at the difference.

“This is not just two experiments disagreeing,” explained [lead researcher and Nobel laureate Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University, in Baltimore, Maryland.] “We are measuring something fundamentally different. One is a measurement of how fast the universe is expanding today, as we see it. The other is a prediction based on the physics of the early universe and on measurements of how fast it ought to be expanding. If these values don’t agree, there becomes a very strong likelihood that we’re missing something in the cosmological model that connects the two eras.”

Ya think? Any cosmologist who claims we really understand what is going on, based on our present fragile and very limited knowledge, is either fooling him or herself or is trying to fool us.

I should note that there seems to be an effort, based on the press release above as well as this second one, to downplay the amount of uncertainties that exist in this cosmological work. Both releases fail to note that when scientists announced their first expansion rate estimate from Hubble’s first data back in 1995, those scientists claimed with absolute certainty that the expansion rate was 80 kilometers per second per megaparsec. At the time some scientists, led by the late Allan Sandage of the Carnegie Observatory, disputed this high number, claiming the number could be as low as 50. Some even said it could be as low as 30 kilometers. Sandage especially found himself poo-pooed by the cosmological community for disputing that the 80 number pushed by Hubble’s scientists in 1995.

In the end, the Hubble scientists in 1995 were closer to today’s Hubble number than Sandage, but his estimate was not wrong by that much more, and he was right when he said the number had to be lower. Either way, Hubble’s modern estimate of 74 for the present expansion rate is very well constrained, and is a far more trustworthy number than previous estimates.

However, do we know with any reliability what the expansion rate was billions of years ago? No. Cosmologists think it was faster, based on supernovae data, which is where the theory of dark energy comes from. It is also where Planck’s predictions come from.

That early expansion rate, however, is based on such tentative data, containing so many assumptions and such large margins of error, that no serious scientist should take it too seriously. It suggests things, but it certainly doesn’t confirm them.

This is why their faith in the numbers derived from Planck puzzles me. It is based on a “prediction,” as Riess admits in the quote above, which means it is based on a theoretical model. It is also based on that very tentative early supernovae data, which makes it very suspect to me.

The Hubble data is real data, obtained by looking at nearby stars in a very precise matter. Its margin of error is very small. It contains only a few assumptions, mostly involving our understanding of the Cepheid variable stars that Hubble observed. While skepticism is always called for, trusting this new Hubble data more is perfectly reasonable.

In the end, to really solve this conflict will require better data from the early universe. Unfortunately, that is not something that will be easy to get.

Pioneer cover

From the press release: From the moment he is handed a possibility of making the first alien contact, Saunders Maxwell decides he will do it, even if doing so takes him through hell and back.

Unfortunately, that is exactly where that journey takes him.

The vision that Zimmerman paints of vibrant human colonies on the Moon, Mars, the asteroids, and beyond, indomitably fighting the harsh lifeless environment of space to build new societies, captures perfectly the emerging space race we see today.

He also captures in Pioneer the heart of the human spirit, willing to push forward no matter the odds, no matter the cost. It is that spirit that will make the exploration of the heavens possible, forever, into the never-ending future.

Available everywhere for $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from the ebook publisher, ebookit. And if you buy it from ebookit you don't support the big tech companies and I get a bigger cut much sooner.


  • Gary

    Touting a prediction (model) over confirmed evidence is a sure sign of an ulterior motive. Climate Science is the poster child for that.

  • wayne

    Dr. Roger Penrose,
    “Aeons before the Big Bang”
    (Copernicus Center Lecture 2010)

  • m d mill

    Actually the theory and observations are not that far off(~10%), considering the uncertainties…If only Climate Science were any where near this certain….The “best” Climate models give a 200% variation in theoretical sensitivity values.

  • m d mill

    correction: I should have said a 2 to 1 variation not “200%”

  • wayne

    Highly recommend any of the Conformal Cyclic Cosmology lectures by Penrose. It’s one of the few cosmological theories that actually addresses the laws of thermodynamics, and he has little use for the concept of “inflation.”

  • wayne

    Prof. Sir Roger Penrose
    “Are we seeing Hawking Points in Cosmic Microwave Background Radiation?”
    [Quantum Spacetime 2019 Conference– public lecture speech]
    March 2019

  • wayne

    on the other hand…..

    “Space-time and Quantum Mechanics are the pillars of our modern understanding of fundamental physics. However, there are storm clouds on the horizon indicating that these principles are approximate and must be replaced with something deeper. The union of quantum mechanics and gravity strongly suggests that “space-time is doomed”.”

    “The Doom of Space Time: Why It Must Dissolve Into More Fundamental Structures”
    Dr. Arkani-Hamed
    Philosophical Society of Washington (PSW) meeting #2384, December 2017

  • Edward

    wayne wrote: “It’s one of the few cosmological theories that actually addresses the laws of thermodynamics, and he has little use for the concept of ‘inflation.’

    The idea of dark energy is attractive. It means that there is a free energy source just laying around waiting for us to tap into it. Who needs fossil fuels, wind turbines, or solar panels when all you have to do is plug into the dark energy outlet.

  • wayne

    “Mr. Fusion”
    (Back to the Future II )

  • John

    Wayne- Watching Penrose lecture with old school slides and projectors was awesome. He conveys ideas with that method better than any power point. Thanks for posting the aeons before big bang link.

    They’re really analyzing that CMB radiation for all it’s worth, and the wikipedia on conformal cyclic cosmology hints that there may be circular imprints.

    Still doesn’t cover the tension between Hubble and Planck data posted here ;)

  • wayne

    Dr. Penrose is the Master of the overhead projector! (he doesn’t like the ‘camera’ type projectors)
    He uses the same set of transparencies’ for most all his “C.C.C.” type lectures.

    from his new book—

    “Fashion, Faith and Fantasy in Physics”
    Sir Dr. Roger Penrose
    March 2017, Royal Institution lecture

    “With a focus on string theory, quantum mechanics, and cosmology, Sir Roger Penrose looks at how physicists are just as susceptible to flights of fantasy, fashion and blind faith as anyone else.”

  • Snailmailtrucker

    Confused ? Here’s why !

    NASA = Never A Straight Answer !

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