Wikipedia:Reference desk/Archives/Science/2023 August 22
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August 22
[edit]How is the distance from the James Webb Space telescope to the most distant galaxies measured?
[edit]The distances from our Solar system to the closest stars can be measured by triangulation. Cepheid are used for more remote objects, but how about the galaxies at the edge of the cosmos? Thanks, AboutFace 22 (talk) 20:39, 22 August 2023 (UTC)
- it's not easy! See Cosmic distance ladder. That is used to calibrate Hubble's law which is the main way to estimate the distance to very distant galaxies. NadVolum (talk) 21:26, 22 August 2023 (UTC)
- Maybe it should be noted that at these distances, the estimates are so rough that "from the JWST" is functionally the same as "from Earth", "from the Sun", or even "from the Milky Way". --Stephan Schulz (talk) 12:41, 29 August 2023 (UTC)
- Reminds me of the joke of the guard in the natural history mueum when asked when a dinosaur on display died said sixty six million and four years and three months ago. He'd been told the date when he joined. ;-) Actually when the meteor fell is known fairly accurately, but the distance to distant galaxies is probably a couple of percent off. NadVolum (talk) 17:55, 29 August 2023 (UTC)
- Maybe it should be noted that at these distances, the estimates are so rough that "from the JWST" is functionally the same as "from Earth", "from the Sun", or even "from the Milky Way". --Stephan Schulz (talk) 12:41, 29 August 2023 (UTC)
Distilling slowly from a bottle in the sun?
[edit]You know those chemical bottles with connectors in the lids to connect tubing? If one was filled with dirty isopropanol and placed in the sun and another was connected to it but placed in the shade, would, over a period of months, you expect the isopropanol to slowly distil from the sun-exposed one to the shaded one? 92.2.123.86 (talk) 23:34, 22 August 2023 (UTC)
- In principle, yes -- however, this will not work if the impurities have a lower boiling point than isopropanol, and/or if they form azeotropes with it. 2601:646:9882:46E0:7C19:FF2A:2EEF:9C07 (talk) 03:34, 23 August 2023 (UTC)
- In particular, methanol: boiling point 64.7 °C (isopropyl alcohol: 80.37 °C). cmɢʟee⎆τaʟκ 14:31, 24 August 2023 (UTC)