Stephen Hawking
Stephen Hawking (1942 to 2018) was a British theoretical physicist who became one of the most famous scientists of his time, renowned for his work on…
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The Hubble Tension
The Hubble tension is a genuine and growing puzzle in cosmology: two careful ways of measuring how fast the universe is expanding give answers that…
Gravitational Lensing
Gravitational lensing is the bending of light from distant objects by the gravity of massive bodies that lie in between, which can magnify and…
The Bending of Starlight
The bending of starlight is the deflection of light by gravity, predicted by Einstein's general theory of relativity and confirmed during a solar…
The Cosmic Microwave Background
The cosmic microwave background is a faint glow of microwave radiation that fills all of space, the leftover heat from the early universe. Its…
Gravitational Waves
Gravitational waves are ripples in the fabric of space and time, set off by some of the most violent events in the universe. Predicted by Einstein a…
Cosmic Inflation
Cosmic inflation is the hypothesis that, in the first tiny fraction of a second after the Big Bang, the universe expanded at an almost unimaginable…
Stellar Evolution
Stellar evolution is the scientific account of how stars are born, live, and die over millions or billions of years. Though no one can watch a single…
The Steady State Theory
The steady state theory was a model of the universe, popular in the mid twentieth century, which held that the universe has always looked roughly the…
The Expansion of the Universe
The universe is expanding: the galaxies are, on average, moving apart, and the space between them is stretching. Once a startling discovery, the…
How the Universe Will End
The ultimate fate of the universe is one of the deepest questions in science. Cosmologists have proposed several very different endings, and which…
The Age of the Universe
The universe is about 13.8 billion years old. Once a matter of wide uncertainty and heated debate, this figure is now known with remarkable…
Planet Nine
Planet Nine is a hypothetical large planet proposed to exist in the far outer reaches of our Solar System, well beyond Neptune and Pluto. It has…
Dark Energy
Dark energy is the name given to an unknown influence that appears to be driving the expansion of the universe to speed up over time. It is thought…
General Relativity
General relativity is Albert Einstein's theory of gravity, published in 1915. It reimagines gravity not as a force pulling objects together but as…
The Fermi Paradox
The Fermi paradox is the puzzling contrast between the high apparent likelihood that alien civilizations exist somewhere in our vast galaxy and the…
The Big Bang
The Big Bang is the prevailing cosmological theory of how the universe began. It holds that the universe started about 13.8 billion years ago in an…