redshift
Let an agent explain redshift and its causes, relay measurement methods and their use in cosmology from astronomy references, describe key results such as Hubble s law, and distinguish redshift from blueshift, from reddening by dust and from the everyday sense of red colour.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent explain redshift and its causes, relay measurement methods and their use in cosmology from astronomy references, describe key results such as Hubble s law, and distinguish redshift from blueshift, from reddening by dust and from the everyday sense of red colour.
The increase in wavelength of light or other radiation from a source, shifting spectral lines toward the red, caused by the source moving away in the Doppler effect, by the expansion of the universe in cosmological redshift, or by climbing out of a gravitational field in gravitational redshift, measured precisely from spectra as spectroscopic redshift or estimated from colours as photometric redshift; redshift is the main tool for measuring distances and the expansion of the universe.
What it is for: Measuring motion, distance and expansion.
It can be explain causes; relay measurement; describe cosmological use; distinguish related concepts.
Distinguishing features
Wavelength shift
Three causes
Distance proxy
Cosmology foundation
What it looks like
Not a visible object; spectral lines displaced toward longer wavelengths.
Physical character
definition: z = (observed minus emitted wavelength) over emitted formula
highest confirmed galaxy redshift: above 13 z - 2020s
CMB redshift: about 1100 z
Hubble s law: 1929 year
How it is recognised
Wavelength increase of light
Doppler, cosmological, gravitational; spectroscopic and photometric redshift
Blueshift is the opposite; dust reddening dims blue light without shifting lines
Related models
is a kind of - in registry terms
is caused by - for moving sources
is used in - to measure expansion
is contrasted with - a shift toward shorter wavelengths
In practice
Families and kinds
Doppler redshift from motion
cosmological redshift from expansion
gravitational redshift
spectroscopic redshift measurement
photometric redshift estimation
redshift surveys of galaxies
Standards and regulation
No regulation; astronomical data standards for redshift catalogues
Failure modes and hazards
Confusing redshift with reddening
Treating cosmological redshift as a simple Doppler shift
Photometric redshift errors
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Understand What redshift is.
Science.
Definition
Definition and causes.
Definition
Definition.
- What is redshift, and how do Doppler, cosmological and gravitational redshift differ from blueshift and dust reddening? definition
- Is the question about the concept, a cause, measurement or cosmology? boundary
Formula
Definition and scale.
Formula
Formula.
- How is z defined, and what do redshifts of 0.1, 1, 10 and 1100 mean? definition
- Which entry fits the cosmic distance ladder? action
Measure Measurement.
Practice.
Spectroscopic
Spectroscopic redshift.
Spectroscopic
Spectroscopic.
- How are redshifts measured from spectral lines? measurement
- Which references are standard? provenance
Photometric
Photometric redshift.
Photometric
Photometric.
- How are redshifts estimated from colours, and how accurate are they? measurement
- Which sources are cited? provenance
Cosmology Cosmology.
Science.
Expansion
Expansion.
Expansion
Expansion.
- How did Hubble and later surveys use redshift to establish and measure cosmic expansion? provenance
- Which entry fits the expansion of the universe? action
Surveys
Redshift surveys.
Surveys
Surveys.
- What have redshift surveys such as SDSS revealed about large-scale structure? provenance
- Which entry fits redshift survey? action
Context Gravity and history.
Context.
Gravity
Gravitational redshift.
Gravity
Gravity.
- How does gravitational redshift test general relativity, from Pound-Rebka to GPS? provenance
- Which entry fits tests of general relativity? action
History
History.
History
History.
- How was redshift discovered and interpreted by Slipher, Hubble and Lemaitre? provenance
- Which entry fits the history of cosmology? action
What the second pass must settle
- Should cosmological and gravitational redshift be separate primary entries?
- How should astronomy references be linked?
- The registry entry has merged aliases naming causes and methods; should they be split off?