3 ms·

I've often thought about this myself. I'm sure scientists involved are aware of the compounding errors with each step and build that in, but I'd love to see an

I've often thought about this myself. I'm sure scientists involved are aware of the compounding errors with each step and build that in, but I'd love to see an analysis that breaks that down. When I first saw it I thought the errors due to cephids must be a large component of uncertainty, but really I've no idea how well contained that is.

sanxiyn 3y ago
Error analysis of cosmic distance ladder is fiercely technical subject. https://arxiv.org/abs/1103.2976 https://arxiv.org/abs/1103.2976 Table 5 is titled "H0 Error Budget for Cepheid and SN Ia Distance Ladders". (It is old and the field is moving fast, but this is what I happened to remember.) Among total error of 3.1%, Cepheid reddening is 1.4% and the second largest source of uncertainty. SN Ia statistics is the largest with 1.9%. Rarely discussed in popular treatment is anchor distance, the third largest source with 1.3%. It is uncertainty of bottom lungs of the ladder, eg the distance to Large Magellanic Cloud before Cepheid and SN Ia are involved.
- raattgift 3y ago
  > Rarely discussed in popular treatment is anchor distance Yes, and I'm sad that it's so rare. The Megamaser Cosmology Project is incredibly awesome; combining line of sight acceleration, velocity, velocity gradient, and observer angle on the sky is very "anchor". https://safe.nrao.edu/wiki/bin/view/Main/MegamaserCosmologyProject https://safe.nrao.edu/wiki/bin/view/Main/MegamaserCosmologyP... Gaia seems to be making good progress on direct parallax up to kiloparsecs. And always happy to plug ASAS-SN <https://www.astronomy.ohio-state.edu/asassn/index.shtml https://www.astronomy.ohio-state.edu/asassn/index.shtml> (The deleted @SuperASASSN was one of the best astro follows on twitter some years ago), who have found an awful lot of detached eclipsing binaries: <https://academic.oup.com/mnras/article/517/2/2190/6695108?login=false https://academic.oup.com/mnras/article/517/2/2190/6695108?lo...>.

sanxiyn 3y ago

Error analysis of cosmic distance ladder is fiercely technical subject. https://arxiv.org/abs/1103.2976 https://arxiv.org/abs/1103.2976 Table 5 is titled "H0 Error Budget for Cepheid and SN Ia Distance Ladders". (It is old and the field is moving fast, but this is what I happened to remember.) Among total error of 3.1%, Cepheid reddening is 1.4% and the second largest source of uncertainty. SN Ia statistics is the largest with 1.9%. Rarely discussed in popular treatment is anchor distance, the third largest source with 1.3%. It is uncertainty of bottom lungs of the ladder, eg the distance to Large Magellanic Cloud before Cepheid and SN Ia are involved.

raattgift 3y ago
> Rarely discussed in popular treatment is anchor distance Yes, and I'm sad that it's so rare. The Megamaser Cosmology Project is incredibly awesome; combining line of sight acceleration, velocity, velocity gradient, and observer angle on the sky is very "anchor". https://safe.nrao.edu/wiki/bin/view/Main/MegamaserCosmologyProject https://safe.nrao.edu/wiki/bin/view/Main/MegamaserCosmologyP... Gaia seems to be making good progress on direct parallax up to kiloparsecs. And always happy to plug ASAS-SN <https://www.astronomy.ohio-state.edu/asassn/index.shtml https://www.astronomy.ohio-state.edu/asassn/index.shtml> (The deleted @SuperASASSN was one of the best astro follows on twitter some years ago), who have found an awful lot of detached eclipsing binaries: <https://academic.oup.com/mnras/article/517/2/2190/6695108?login=false https://academic.oup.com/mnras/article/517/2/2190/6695108?lo...>.