Calculateur de Paramètre de Décélération
Calculez le paramètre de décélération cosmologique.
Deceleration Parameter (q0)
-0.535000
Deceleration Parameter (q0) vs Matter Density Parameter (Omega_m)
Formule
The Deceleration Parameter
The deceleration parameter q₀ tells us whether cosmic expansion is speeding up or slowing down.
Formula (matter + Lambda)
q0 = Omega_m / 2 - Omega_Lambda
Current values give q0 ≈ -0.535, confirming accelerating expansion.
Exemple Résolu
Standard cosmology: Omega_m = 0.31, Omega_Lambda = 0.69.
- 01q0 = Omega_m / 2 - Omega_Lambda
- 02q0 = 0.31 / 2 - 0.69
- 03q0 = 0.155 - 0.69
- 04q0 = -0.535
Questions Fréquentes
What does a negative deceleration parameter mean physically?
It means the expansion of the universe is accelerating. Dark energy dominates over the gravitational pull of matter.
Was q0 always negative?
No. In the early universe matter density was much higher, and q0 was positive. The transition to acceleration occurred around 5 billion years ago.
How is q0 measured observationally?
Primarily through Type Ia supernovae, which serve as standard candles to map the expansion history.