⭐ Starlight Tools / Cosmology Calculator

Understanding the Calculator

This calculator uses the Friedmann-Lemaître-Robertson-Walker (FLRW) metric to model a homogeneous and isotropic universe. By providing the key parameters of this model, you can determine various properties of the universe at a specific redshift (z).

This tool is a modern implementation based on the foundational equations from the original JavaScript Cosmology Calculator created by Prof. Edward L. (Ned) Wright, whose work has been a valuable resource for the astronomical community for many years.

Key Cosmological Parameters

• Hubble Constant ($H_0$): The current rate of expansion of the universe, measured in km/s/Mpc. It tells us how fast galaxies are moving away from us.
• Omega Matter ($\Omega_M$): The density of all matter (both normal and dark matter) in the universe, relative to the critical density needed to halt expansion.
• Omega Vacuum ($\Omega_\Lambda$): The density of dark energy (cosmological constant) in the universe, relative to the critical density. This component is responsible for the accelerated expansion of the universe.
• Redshift ($z$): A measure of how much the light from a distant object has been stretched by the expansion of the universe. Higher redshift means the object is farther away and its light was emitted earlier in cosmic history.

Calculated Cosmic Properties

• Age of the Universe: The total time elapsed since the Big Bang, based on the input parameters.
• Age at Redshift z: How old the universe was when the light from the object at redshift 'z' was emitted.
• Light Travel Time: The time it took for light emitted from an object at redshift 'z' to reach us. This is also known as the "lookback time".
• Comoving Radial Distance: The distance between us and an object at redshift 'z' that remains constant over time if both we and the object are moving with the Hubble flow (i.e., it accounts for the expansion of the universe).
• Angular Size Distance ($D_A$): A distance measure used to relate an object's physical size to its apparent angular size in the sky. Due to cosmic expansion, objects can appear larger than expected at very high redshifts.
• Luminosity Distance ($D_L$): A distance measure used to relate an object's intrinsic brightness (luminosity) to its observed brightness (flux). Objects at high redshift appear dimmer than their physical distance would suggest. It is related to the angular size distance by the formula $D_L = D_A (1+z)^2$.