Light-travel delay

You are seeing the past.

Light does not arrive instantly. Choose a real Earth–object snapshot, then compare where the object was when its light left with where it was when that light arrived.

t = d c
EARTH / LIGHT ARRIVES
ACTUAL POSITION NOW
Choose an object
Choose a distance
Distance from Earth d d ∝ t
near · far
How far into the past
Relative position changed
Try

Distances come from NASA/JPL Horizons geometric Earth-centred vectors sampled daily from 2000 through 2050. The selected date is the moment the light arrives at Earth; the page calculates when it left the object. Shortest and longest dates were refined hourly; average is the arithmetic mean of the daily distances, represented by the nearest sampled date. “Relative position changed” compares the Earth-to-object vector at those two moments — it is not the object's path length. The upward movement uses JPL mean diameters; sub-pixel changes are enlarged and very large changes are compressed, with either adjustment labelled. Download the 149,024-row dataset or view the calculated summary. Horizontal distances are compressed.