SPACETRC / RESEARCH CONTEXT
SPACETRC / A JOURNEY THROUGH SCALE
Begin with one world.
Rethink distance.
Move continuously between thirteen sourced stations. Separate size, distance and unit definitions; calculate what a light-travel interval actually describes.
Original SpaceTRC schematic. The spheres, stars and filaments are not a measured complete 3D universe map; the numerical lengths are tied to the sources below.
No journey starts automatically. Motion is enabled only by your choice; reduced-motion preferences make changes immediate.
Diameter / size
Earth · mean diameter
Twice the 6,371 km volumetric mean radius. We begin with an object’s size.
This is neither equatorial diameter nor distance to Earth.
- Source value and unit
- 12.742 km
- Compared length
- Light interval · stated model
- Ratio to Earth’s mean diameter
Additional conversion digits do not increase the source measurement’s precision.
A station does not automatically determine a research target’s distance.
Numerical facts and sources remain readable below without JavaScript.
Which question does this length answer?
Size
An object’s diameter is not its distance from us. Earth’s diameter, lunar distance and solar diameter are compared as lengths, not placed in one spatial position sequence.
Logarithmic scale
Equal slider intervals represent equal factors, not equal additions of length. View width is a length reference; not every illustrated object’s diameter follows that same ratio.
Light interval and cosmology
In a local static model t=L/c. For a diameter this is a crossing interval. At cosmological distances, observed lookback time, comoving distance and current proper distance differ; this tool does not integrate a cosmological model.
Thirteen stations · value, meaning and source
01 / Diameter / size
Earth · mean diameter
Twice the 6,371 km volumetric mean radius. We begin with an object’s size.
This is neither equatorial diameter nor distance to Earth.
12742 km · Derived from a rounded source
Source: NASA/NSSDC · Earth Fact Sheet ↗
02 / Distance between locations
Earth–Moon · mean distance
Approximate mean centre-to-centre distance of the lunar orbit.
Not an instantaneous lunar position or the surface-to-surface gap.
384400 km · Rounded source value
Source: NASA Science · Moon Facts ↗
03 / Diameter / size
Sun · approximate diameter
NASA’s rounded solar diameter illustrates why size and distance are separate quantities.
Measured radius depends on definition and wavelength; this is a rounded educational scale.
1400000 km · Rounded source value
Source: NASA Science · Sun Facts ↗
04 / Defined length unit
One astronomical unit
One au is exactly 149,597,870.7 km, a length unit useful for comparing Solar System scales.
An exact unit does not make the Earth–Sun distance constant.
1 au · Exact unit definition
Source: NASA/JPL SSD · Astronomical unit definition ↗, IAU · Measuring the Universe ↗
05 / Distance between locations
Sun–Jupiter · orbital scale
Rounded semimajor-axis scale of Jupiter’s orbit.
Not Earth–Jupiter separation or an ephemeris for a particular date.
5.2 au · Rounded source value
Source: NASA Science · Jupiter Facts ↗
06 / Distance between locations
Sun–Neptune · orbital scale
Neptune’s approximate 30 au orbital scale makes interplanetary separation tangible.
Rounded mean, not the Solar System’s boundary or a current position.
30 au · Rounded source value
Source: NASA Science · Neptune Facts ↗
07 / Defined length unit
One light-year
Distance travelled by light in vacuum during one Julian year: a length, not a time.
One Julian year is 365.25 days; c=299,792.458 km/s.
1 ly · Exact unit definition
Source: BIPM · SI base unit: metre ↗, IAU · Measuring the Universe ↗
08 / Distance between locations
Sun–Proxima Centauri
NASA’s rounded distance to the Sun’s nearest stellar neighbour.
A sourced scale for a nearby star; this panel does not fit a parallax.
4.24 ly · Rounded source value
Source: NASA Science · Sun Facts ↗
09 / Distance between locations
Earth–Galactic centre
About 26 thousand light-years to our galaxy’s centre, a new interstellar scale.
Rounded source value, distinct from the Milky Way’s diameter.
26000 ly · Rounded source value
Source: NASA Science · Compass/Scale Annotated Image of the Center of the Milky Way ↗
10 / Diameter / size
Milky Way · disk-diameter scale
A conventional approximately 100-thousand-light-year disk scale; the chosen component matters.
The stellar disk has no sharp edge; gas, stellar and dark-matter haloes have different extents.
100000 ly · Rounded source value
11 / Distance between locations
Earth–Andromeda
About 2.5 million light-years to a nearby large galactic neighbour.
Approximate intergalactic distance; no merger time is predicted.
2500000 ly · Rounded source value
12 / Distance between locations
Earth–Virgo Cluster
HEASARC’s approximate 16 Mpc distance scale for the Virgo Cluster.
The cluster has depth. At this cosmological scale d/c is not presented as observed lookback time.
16 Mpc · Rounded source value
Source: NASA HEASARC · The Virgo Cluster ↗, IAU · Measuring the Universe ↗, IAU · 2015 Resolution B2, note4: exact parsec definition ↗
13 / Selected reference length
Cosmic web ·100 Mpc reference
A selected 100 Mpc reference length for thinking about clusters, filaments and voids.
Not the measured length of one filament, the Universe’s diameter or an observable boundary. The drawing is conceptual.
100 Mpc · Selected illustrative reference
Source: NASA Science · Galaxies and the cosmic web ↗, IAU · Measuring the Universe ↗, IAU · 2015 Resolution B2, note4: exact parsec definition ↗