Exploring the Vastness – The Science of Cosmology

The Big Bang Theory

The prevailing cosmological model is the Big Bang theory, which posits that the observable universe originated from an extremely hot, dense state approximately 13.8 billion years ago. This wasn't an explosion *in* space, but rather an expansion *of* space itself.

Evidence supporting this includes the redshift of distant galaxies (Hubble’s Law), the cosmic microwave background radiation (CMB) – a faint afterglow of the Big Bang – and the abundance of light elements like hydrogen and helium.

v = H₀d  (Velocity = Hubble Constant * Distance)

Expansion and Hubble’s Law

Edwin Hubble's observations in the 1920s revealed that galaxies are moving away from us, with their recession velocity proportional to their distance. This relationship is known as Hubble’s Law.

This expansion implies a finite age for the universe and suggests it was much smaller and denser in the past. The rate of this expansion is currently accelerating.

H = 70 km/s/Mpc (Hubble Constant ≈ 70 km/s/Mpc)

Dark Matter and Dark Energy

Observations indicate that the visible matter – stars, galaxies, and gas – accounts for only about 5% of the universe’s total energy density. The remaining 95% is composed of dark matter (approximately 27%) and dark energy (approximately 68%).

Dark matter interacts gravitationally but doesn't emit or absorb light, making it invisible to telescopes. Dark energy is even more mysterious; it’s thought to be responsible for the accelerating expansion of the universe.

ρ_total = ρ_baryonic + ρ_dark_matter + ρ_dark_energy

Future of the Universe

The ultimate fate of the universe depends largely on the nature of dark energy. Current models suggest a ‘Big Rip’ – where the expansion accelerates to such an extent that it tears apart galaxies, solar systems, and eventually even atoms.

Alternatively, if dark energy weakens over time, gravity could eventually halt the expansion and cause the universe to collapse in a ‘Big Crunch’. The most likely scenario remains uncertain.

Frequently asked questions

Try it live

Everything above runs in your browser — open Cosmology: An Introduction to the Universe's Origins and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.