01
Direct observation
A detector record before physical interpretation.
[ Explanatory layer // astronomy-knowledge/0.1 ]
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
23 cited explainers
18 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.
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 →
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 →
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 →