Cosmology
The origin, structure, evolution, and eventual fate of the universe as a whole.
💥 The Big Bang
About 13.8 billion years ago, the universe began in an extremely hot, dense state and has been expanding ever since. The evidence is overwhelming: the cosmic microwave background (CMB), the abundance of light elements, and the observed expansion of the universe all confirm it.
📡 Cosmic Microwave Background
The CMB is the afterglow of the Big Bang, emitted about 380,000 years after the event when the universe cooled enough for atoms to form. First detected in 1965 by Penzias and Wilson (Nobel Prize 1978). The WMAP and Planck satellites mapped it in exquisite detail, confirming standard cosmology.
⬛ Dark Matter
Galaxies rotate in ways that cannot be explained by visible matter alone. Something unseen provides extra gravity. Dark matter makes up about 27% of the universe's energy content. Leading candidates include WIMPs and axions. Despite decades of searching, no dark matter particle has been directly detected.
🔮 Dark Energy
In 1998, two independent teams discovered that the expansion of the universe is accelerating, driven by a mysterious dark energy making up about 68% of the universe. It may be the cosmological constant Einstein originally proposed (and then called his biggest blunder). We do not know what it is.
🎈 Cosmic Inflation
A period of exponential expansion in the first 10-36 seconds after the Big Bang, proposed to explain the uniformity of the CMB and the flatness of the universe. The universe expanded faster than light during inflation (this does not violate relativity, which only limits local motion).
🔚 Fate of the Universe
If dark energy continues to accelerate expansion, the universe ends in a Big Freeze: all matter becomes cold and dark after all stars burn out in roughly 10100 years. Alternative scenarios include Big Rip (if dark energy intensifies) and Big Crunch (if expansion reverses). Current data strongly favors Big Freeze.