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Having a look on Wikipedia I noticed the following values (of the last 6 years) for the Hubble constant:

  • 67.6±0.7 SDSS-III Baryon Oscillation Spectroscopic Survey
  • 73.00±1.75 Hubble Space Telescope
  • 67.80±0.77 Planck Mission
  • 69.32±0.80 WMAP (9-years)
  • 70.4±1.3 WMAP (7-years)

Most of experiments exclude the values of the others so that WMAP excludes the values of SDSS and from Hubble, while Hubble excludes Plank Mission's values, SDSS and WMAP 9. Can anybody tell what's the problem here and which one is the more reliable source for $H_0$?

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  • $\begingroup$ This is more a guess, so I haven't put as an answer, though I'm fairly certain it is very close to the truth: measuring the Hubble shift of nearby objects gives you a less model-dependent way of measuring H, but the measurement of the Hubble shift is more error-prone. Measurement of the Hubble shift of further away objects is less error-prone, but using them to measure H is much more model-dependent. $\endgroup$
    – John Davis
    Commented Jan 6, 2017 at 18:31
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    $\begingroup$ I can assure you, from my many years of experience in this, that the answer to your question is unequivocally -- No. Some may have strong opinions on this, but scientists differ on this and no one knows for sure. However, the situation now is better than it was before. $\endgroup$
    – eshaya
    Commented Jan 6, 2017 at 22:15
  • $\begingroup$ I was afraid that was exactly the case... thank you eshaya $\endgroup$
    – Dac0
    Commented Jan 6, 2017 at 22:19
  • $\begingroup$ There's some controversy over the constant: arxiv.org/abs/1512.07364 and en.wikipedia.org/wiki/Hubble_Bubble_(astronomy) $\endgroup$
    – Wayfaring Stranger
    Commented Jan 7, 2017 at 15:46
  • $\begingroup$ illustration of this phenomenon cfa.harvard.edu/~dfabricant/huchra/hubble/h1920.jpg $\endgroup$
    – samcarter_is_at_topanswers.xyz
    Commented Jan 11, 2017 at 17:16

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