01
Direct observation
A detector record before physical interpretation.
[ Explanatory layer // astronomy-knowledge/0.2 ]
The universe, with the inference chain left intact.
Astronomy begins with recorded signals, not conclusions. This layer shows what was observed, how it was calibrated, which model converts it into a physical claim, and where uncertainty remains.
Layer status: foundational
7 knowledge tracks
25 cited explainers
21 registered sources
6 epistemic states
Astrological interpretation: outside this layer
Epistemic ladder
Every sentence has a type.
02
Calibrated measurement
An observable after instrument and reference calibration.
03
Method basis
A standard, transformation, or measurement procedure.
04
Model-dependent
A parameter or explanation conditional on stated assumptions.
05
Consensus summary
A bounded synthesis supported across established evidence.
06
Open question
A live uncertainty, degeneracy, or unresolved mechanism.
Inference-boundary guides
Ask what was observed before asking what it means.
These guides define measurement, calibration, observable, uncertainty, and inference checks. They report no new observation or model fit.
Bounded method
Active galactic nuclei: inference boundary
What can and cannot be inferred from active galactic nuclei?
Bounded method
Active galactic nuclei: uncertainty
Which uncertainties control active galactic nuclei?
Bounded method
Active galactic nuclei: measurement method
How is a measurement made for active galactic nuclei?
Bounded method
Active galactic nuclei: observable
What is directly observed when measuring active galactic nuclei?
Bounded method
Active galactic nuclei: calibration
What calibration chain is required for active galactic nuclei?
Bounded method
Astronomical time scales: inference boundary
What can and cannot be inferred from astronomical time scales?
Bounded method
Astronomical time scales: uncertainty
Which uncertainties control astronomical time scales?
Bounded method
Astronomical time scales: measurement method
How is a measurement made for astronomical time scales?
Bounded method
Astronomical time scales: calibration
What calibration chain is required for astronomical time scales?
Bounded method
Celestial reference frames: inference boundary
What can and cannot be inferred from celestial reference frames?
Bounded method
Celestial reference frames: uncertainty
Which uncertainties control celestial reference frames?
Bounded method
Compact objects: inference boundary
What can and cannot be inferred from compact objects?
Bounded method
Cosmic distance ladder: inference boundary
What can and cannot be inferred from cosmic distance ladder?
Bounded method
Cosmological redshift: inference boundary
What can and cannot be inferred from cosmological redshift?
Bounded method
Detector calibration: inference boundary
What can and cannot be inferred from detector calibration?
Bounded method
Direct imaging: inference boundary
What can and cannot be inferred from direct imaging?
Bounded method
Gravitational microlensing: inference boundary
What can and cannot be inferred from gravitational microlensing?
Bounded method
Gravitational waves: inference boundary
What can and cannot be inferred from gravitational waves?
Bounded method
Orbit determination: inference boundary
What can and cannot be inferred from orbit determination?
Bounded method
Photometry: inference boundary
What can and cannot be inferred from photometry?
Bounded method
Planetary ephemerides: inference boundary
What can and cannot be inferred from planetary ephemerides?
Bounded method
Point-spread functions: inference boundary
What can and cannot be inferred from point-spread functions?
Bounded method
Precession and nutation: inference boundary
What can and cannot be inferred from precession and nutation?
Bounded method
Proper motion: inference boundary
What can and cannot be inferred from proper motion?
Bounded method
Radial-velocity exoplanet detection: inference boundary
What can and cannot be inferred from radial-velocity exoplanet detection?
Bounded method
Radial velocity: inference boundary
What can and cannot be inferred from radial velocity?
Bounded method
Signal-to-noise ratio: inference boundary
What can and cannot be inferred from signal-to-noise ratio?
Bounded method
Spectroscopy: inference boundary
What can and cannot be inferred from spectroscopy?
Bounded method
Stellar evolution: inference boundary
What can and cannot be inferred from stellar evolution?
Bounded method
Stellar parallax: inference boundary
What can and cannot be inferred from stellar parallax?
Bounded method
Survey selection effects: inference boundary
What can and cannot be inferred from survey selection effects?
Bounded method
Telescope angular resolution: inference boundary
What can and cannot be inferred from telescope angular resolution?
Bounded method
Transit detection: inference boundary
What can and cannot be inferred from transit detection?
Bounded method
Compact objects: uncertainty
Which uncertainties control compact objects?
Bounded method
Cosmic distance ladder: uncertainty
Which uncertainties control cosmic distance ladder?
Bounded method
Cosmological redshift: uncertainty
Which uncertainties control cosmological redshift?
Bounded method
Detector calibration: uncertainty
Which uncertainties control detector calibration?
Bounded method
Direct imaging: uncertainty
Which uncertainties control direct imaging?
Bounded method
Gravitational microlensing: uncertainty
Which uncertainties control gravitational microlensing?
Bounded method
Gravitational waves: uncertainty
Which uncertainties control gravitational waves?
Bounded method
Orbit determination: uncertainty
Which uncertainties control orbit determination?
Bounded method
Photometry: uncertainty
Which uncertainties control photometry?
Bounded method
Planetary ephemerides: uncertainty
Which uncertainties control planetary ephemerides?
Bounded method
Point-spread functions: uncertainty
Which uncertainties control point-spread functions?
Bounded method
Precession and nutation: uncertainty
Which uncertainties control precession and nutation?
Bounded method
Proper motion: uncertainty
Which uncertainties control proper motion?
Bounded method
Radial-velocity exoplanet detection: uncertainty
Which uncertainties control radial-velocity exoplanet detection?
Bounded method
Radial velocity: uncertainty
Which uncertainties control radial velocity?
Bounded method
Signal-to-noise ratio: uncertainty
Which uncertainties control signal-to-noise ratio?
Bounded method
Spectroscopy: uncertainty
Which uncertainties control spectroscopy?
Bounded method
Stellar evolution: uncertainty
Which uncertainties control stellar evolution?
Bounded method
Stellar parallax: uncertainty
Which uncertainties control stellar parallax?
Bounded method
Survey selection effects: uncertainty
Which uncertainties control survey selection effects?
Bounded method
Telescope angular resolution: uncertainty
Which uncertainties control telescope angular resolution?
Bounded method
Transit detection: uncertainty
Which uncertainties control transit detection?
Bounded method
Astronomical time scales: observable
What is directly observed when measuring astronomical time scales?
Bounded method
Celestial reference frames: measurement method
How is a measurement made for celestial reference frames?
Bounded method
Celestial reference frames: calibration
What calibration chain is required for celestial reference frames?
Bounded method
Compact objects: measurement method
How is a measurement made for compact objects?
Bounded method
Cosmic distance ladder: measurement method
How is a measurement made for cosmic distance ladder?
Bounded method
Cosmological redshift: measurement method
How is a measurement made for cosmological redshift?
Bounded method
Detector calibration: calibration
What calibration chain is required for detector calibration?
Bounded method
Detector calibration: measurement method
How is a measurement made for detector calibration?
Bounded method
Direct imaging: measurement method
How is a measurement made for direct imaging?
Bounded method
Gravitational microlensing: measurement method
How is a measurement made for gravitational microlensing?
Bounded method
Gravitational waves: measurement method
How is a measurement made for gravitational waves?
Bounded method
Orbit determination: measurement method
How is a measurement made for orbit determination?
Bounded method
Photometry: measurement method
How is a measurement made for photometry?
Bounded method
Planetary ephemerides: measurement method
How is a measurement made for planetary ephemerides?
Bounded method
Point-spread functions: measurement method
How is a measurement made for point-spread functions?
Bounded method
Precession and nutation: measurement method
How is a measurement made for precession and nutation?
Bounded method
Proper motion: measurement method
How is a measurement made for proper motion?
Bounded method
Radial-velocity exoplanet detection: measurement method
How is a measurement made for radial-velocity exoplanet detection?
Bounded method
Radial velocity: measurement method
How is a measurement made for radial velocity?
Bounded method
Signal-to-noise ratio: measurement method
How is a measurement made for signal-to-noise ratio?
Bounded method
Spectroscopy: measurement method
How is a measurement made for spectroscopy?
Bounded method
Stellar evolution: measurement method
How is a measurement made for stellar evolution?
Bounded method
Stellar parallax: measurement method
How is a measurement made for stellar parallax?
Bounded method
Survey selection effects: measurement method
How is a measurement made for survey selection effects?
Bounded method
Telescope angular resolution: measurement method
How is a measurement made for telescope angular resolution?
Bounded method
Transit detection: measurement method
How is a measurement made for transit detection?
Bounded method
Celestial reference frames: observable
What is directly observed when measuring celestial reference frames?
Bounded method
Detector calibration: observable
What is directly observed when measuring detector calibration?
Bounded method
Compact objects: observable
What is directly observed when measuring compact objects?
Bounded method
Cosmic distance ladder: observable
What is directly observed when measuring cosmic distance ladder?
Bounded method
Cosmological redshift: observable
What is directly observed when measuring cosmological redshift?
Bounded method
Direct imaging: observable
What is directly observed when measuring direct imaging?
Bounded method
Gravitational microlensing: observable
What is directly observed when measuring gravitational microlensing?
Bounded method
Gravitational waves: observable
What is directly observed when measuring gravitational waves?
Bounded method
Orbit determination: observable
What is directly observed when measuring orbit determination?
Bounded method
Photometry: observable
What is directly observed when measuring photometry?
Bounded method
Planetary ephemerides: observable
What is directly observed when measuring planetary ephemerides?
Bounded method
Point-spread functions: observable
What is directly observed when measuring point-spread functions?
Bounded method
Precession and nutation: observable
What is directly observed when measuring precession and nutation?
Bounded method
Proper motion: observable
What is directly observed when measuring proper motion?
Bounded method
Radial-velocity exoplanet detection: observable
What is directly observed when measuring radial-velocity exoplanet detection?
Bounded method
Radial velocity: observable
What is directly observed when measuring radial velocity?
Bounded method
Signal-to-noise ratio: observable
What is directly observed when measuring signal-to-noise ratio?
Bounded method
Spectroscopy: observable
What is directly observed when measuring spectroscopy?
Bounded method
Stellar evolution: observable
What is directly observed when measuring stellar evolution?
Bounded method
Stellar parallax: observable
What is directly observed when measuring stellar parallax?
Bounded method
Survey selection effects: observable
What is directly observed when measuring survey selection effects?
Bounded method
Telescope angular resolution: observable
What is directly observed when measuring telescope angular resolution?
Bounded method
Transit detection: observable
What is directly observed when measuring transit detection?
Bounded method
Compact objects: calibration
What calibration chain is required for compact objects?
Bounded method
Cosmic distance ladder: calibration
What calibration chain is required for cosmic distance ladder?
Bounded method
Cosmological redshift: calibration
What calibration chain is required for cosmological redshift?
Bounded method
Direct imaging: calibration
What calibration chain is required for direct imaging?
Bounded method
Gravitational microlensing: calibration
What calibration chain is required for gravitational microlensing?
Bounded method
Gravitational waves: calibration
What calibration chain is required for gravitational waves?
Bounded method
Orbit determination: calibration
What calibration chain is required for orbit determination?
Bounded method
Photometry: calibration
What calibration chain is required for photometry?
Bounded method
Planetary ephemerides: calibration
What calibration chain is required for planetary ephemerides?
Bounded method
Point-spread functions: calibration
What calibration chain is required for point-spread functions?
Bounded method
Precession and nutation: calibration
What calibration chain is required for precession and nutation?
Bounded method
Proper motion: calibration
What calibration chain is required for proper motion?
Bounded method
Radial velocity: calibration
What calibration chain is required for radial velocity?
Bounded method
Radial-velocity exoplanet detection: calibration
What calibration chain is required for radial-velocity exoplanet detection?
Bounded method
Signal-to-noise ratio: calibration
What calibration chain is required for signal-to-noise ratio?
Bounded method
Spectroscopy: calibration
What calibration chain is required for spectroscopy?
Bounded method
Stellar evolution: calibration
What calibration chain is required for stellar evolution?
Bounded method
Stellar parallax: calibration
What calibration chain is required for stellar parallax?
Bounded method
Survey selection effects: calibration
What calibration chain is required for survey selection effects?
Bounded method
Telescope angular resolution: calibration
What calibration chain is required for telescope angular resolution?
Bounded method
Transit detection: calibration
What calibration chain is required for transit detection?
01
Foundations
Reference systems, scale, evidence, uncertainty, and the distinction between observation and inference.
foundationFOUNDATIONAL
Sky position
Why a celestial coordinate is incomplete without an origin, frame, epoch, time scale, observer, and correction model.
3 bounded claimsOpen explainer →
foundationFOUNDATIONAL
Light-time & distance
Separating travel time, geometric distance, luminosity distance, and model-dependent lookback time.
3 bounded claimsOpen explainer →
foundationFOUNDATIONAL
Evidence & uncertainty
A disciplined chain from detector output to calibrated measurement, inferred parameter, and bounded scientific claim.
3 bounded claimsOpen explainer →
02
Observing
How instruments turn photons, time variation, particles, and spacetime strain into calibrated data.
foundationFOUNDATIONAL
Electromagnetic spectrum
How wavelength, frequency, opacity, emission mechanisms, and detector technology shape what can be observed.
3 bounded claimsOpen explainer →
methodFOUNDATIONAL
Telescopes & detectors
From aperture and point-spread function to sampling, sensitivity, backgrounds, and reconstructed images.
3 bounded claimsOpen explainer →
methodFOUNDATIONAL
Photometry
How brightness is measured through a bandpass and converted into calibrated fluxes, colors, and light curves.
3 bounded claimsOpen explainer →
methodFOUNDATIONAL
Spectroscopy
Turning wavelength-resolved light into evidence about composition, motion, temperature, density, and cosmic redshift.
3 bounded claimsOpen explainer →
methodFOUNDATIONAL
Astrometry
How repeated position measurements reveal distance and motion while preserving covariance and frame dependence.
3 bounded claimsOpen explainer →
methodACTIVE
Time-domain & multimessenger
How cadence, alerts, coincidence windows, and independent messengers reveal changing and violent systems.
3 bounded claimsOpen explainer →
methodACTIVE
VLBI
Time a wavefront across two distant antennas, and get a reference frame out of the difference.
3 bounded claimsOpen explainer →
03
Planetary systems
Orbits, Solar System architecture, and evidence for planets around other stars.
physical processFOUNDATIONAL
Orbits & ephemerides
The difference between measured tracking data, a dynamical model, orbital elements, and a predicted state.
3 bounded claimsOpen explainer →
object systemFOUNDATIONAL
Solar System
Bodies, reservoirs, dynamical structure, compositional gradients, and the evidence used to reconstruct formation.
3 bounded claimsOpen explainer →
methodACTIVE
Exoplanet evidence
How transits, radial velocities, astrometry, microlensing, and imaging become candidates and vetted planetary systems.
3 bounded claimsOpen explainer →
04
Stars & matter
Star formation, nuclear evolution, stellar remnants, and the gas and dust between stars.
physical processFOUNDATIONAL
Star formation
From cold molecular material to protostars, hydrostatic support, fusion, and feedback into the interstellar medium.
3 bounded claimsOpen explainer →
modelFOUNDATIONAL
Stellar evolution
How spectra, luminosity, temperature, mass, composition, and populations constrain a star’s life cycle.
3 bounded claimsOpen explainer →
object systemFOUNDATIONAL
Stellar remnants
White dwarfs, neutron stars, stellar-mass black holes, and the observations used to distinguish compact remnants.
3 bounded claimsOpen explainer →
object systemFOUNDATIONAL
Interstellar medium
Gas, dust, ionization, extinction, shocks, and the cycling of matter between stars and galactic environments.
3 bounded claimsOpen explainer →
methodACTIVE
Asteroseismology
Infer the inside of a star from the pattern of its brightness oscillations, and note what the photometry alone cannot settle.
3 bounded claimsOpen explainer →
05
Galaxies
Bound stellar systems, active nuclei, large-scale structure, and their observable signatures.
object systemFOUNDATIONAL
Galaxies
Stellar populations, gas, dust, dynamics, dark matter, morphology, environment, and evidence for change over cosmic time.
3 bounded claimsOpen explainer →
object systemFOUNDATIONAL
Active galactic nuclei
How luminous nuclei, accretion disks, obscuration, jets, and viewing geometry are inferred across wavelengths.
3 bounded claimsOpen explainer →
06
Relativistic universe
Black holes, gravitational waves, lensing, and measurements that require relativistic models.
modelFOUNDATIONAL
Black-hole evidence
What is actually measured when Astronomy reports a black hole, event-horizon-scale structure, mass, or spin.
3 bounded claimsOpen explainer →
methodACTIVE
Gravitational waves
From calibrated interferometer strain to waveform inference, source localization, and compact-binary populations.
3 bounded claimsOpen explainer →
methodFOUNDATIONAL
Gravitational lensing
Strong, weak, and microlensing as geometry-sensitive evidence for mass and magnification.
3 bounded claimsOpen explainer →
07
Cosmology
Redshift, distance, expansion, relic radiation, and model-dependent reconstruction of cosmic history.
modelFOUNDATIONAL
Redshift & expansion
Separating measured wavelength shift from peculiar velocity, cosmological expansion, and distance-model inference.
3 bounded claimsOpen explainer →
modelFOUNDATIONAL
CMB & ΛCDM
How a nearly uniform microwave sky becomes a model-dependent constraint on the early universe and cosmic parameters.
3 bounded claimsOpen explainer →