Calculateur de Distance Propre
Calculez la distance propre d'un objet dans l'univers en expansion.
Proper Distance
428.0000 Mpc
Proper Distance vs Comoving Distance
Formule
Proper Distance
The proper distance is the physical distance between two objects at a particular moment in cosmic time.
Relation
d_proper = a(t) * d_comoving
At the present epoch a = 1, so proper distance equals comoving distance. In the past (a < 1) the physical distance was smaller.
Exemple Résolu
A galaxy with comoving distance 428 Mpc observed at the present epoch (a = 1).
- 01d_proper = a(t) * d_comoving
- 02d_proper = 1.0 * 428
- 03d_proper = 428 Mpc ≈ 1396 Mly
Questions Fréquentes
What is the scale factor?
The scale factor a(t) describes how distances in the universe have changed over time. By convention a = 1 today; at the Big Bang a = 0.
When would I use a scale factor other than 1?
To find the physical distance at an earlier epoch. For instance, at redshift z the scale factor was a = 1 / (1 + z).
Is the proper distance directly observable?
Not directly. We infer it from redshift and a cosmological model. What we observe is the luminosity distance or angular-diameter distance.