cosmology

PBS Space Time explains the Hubble constant tension, in which two precise, independent methods of measuring the universe's expansion rate disagree. It covers why this calls some standard cosmology into question.

Astrophysicist Dr. Becky explains the Hubble tension, the disagreement between expansion-rate measurements from the cosmic microwave background and the distance ladder, and what early JWST Cepheid observations add.

PBS Space Time explains Roger Penrose's conformal cyclic cosmology, in which the far future of our universe becomes the big bang of the next. It explores what could come after the universe ends.

A PBS Space Time episode asking whether our universe could sit inside a black hole. It covers what physicists think happens inside black holes and the arguments for and against this idea.

Kurzgesagt explores the idea that black holes could create universes and that we might live inside one. It builds up the physics of how density falls as black holes get larger.

Kurzgesagt explains why, even with science-fiction technology, most of the universe is permanently out of reach because of cosmic expansion and finite resources.

A PBS Space Time episode asking whether time began at the Big Bang. It explains that the Big Bang is not what most people were taught and what 'start' of the universe really means.

Physicist Angela Collier argues that dark matter is not a theory but a set of observations, covering rotation curves, the CMB and why modified gravity struggles to explain them.

Sabine Hossenfelder explains how her opinion on dark matter has shifted, weighing the evidence for and against it and the case for modified gravity. It runs through what dark matter is and why it has not been detected.

A PBS Space Time episode on how gravitational wave observations of a neutron star merger, GW170817, can limit the number of spacetime dimensions. It is based on a 2018 paper.

A short Nature video on the discovery that our home supercluster is Laniakea, redefined by mapping the flow of galaxies rather than their density. It names the structure with a Hawaiian word meaning 'immeasurable heaven'.

PBS Space Time asks whether dark matter could be made of primordial black holes. It walks through the observational constraints that limit this idea.

Explains the proposed NASA JPL plan to use the Sun as a gravitational lens, sending solar sail craft to its focal region to image an exoplanet's surface. It covers the distances involved, how imaging with the Sun would work and the mission design.

ScienceClic explains why the rubber sheet analogy for general relativity is misleading and offers a new visualization that includes the curvature of time and shows gravity as motion through curved spacetime.

PBS Space Time explains the proposal to use the Sun's gravity as a giant lens, sending a train of small light-sail spacecraft to the focal point roughly 550 AU out. It covers how such a telescope could image exoplanets in surprising detail and the engineering challenges involved.

A visual scale comparison of stars and cosmic objects, from planets up to some of the largest known stars, set to music. It is meant to convey the vastness of the universe.

Veritasium explains, with expert input, that in general relativity gravity is not a force and objects follow straight paths through curved spacetime, including why standing on the ground means you are accelerating.

Cody's Lab builds a 200-billionth-scale model to show how far away the nearest stars are, using parallax and light speed. A short astronomy explainer on interstellar distances.

An Isaac Arthur episode on civilizations in the far future, past the Black Hole Era. It covers iron stars, Boltzmann brains, reversible computing and the idea of reversing entropy.

David Kipping presents his proposed Terrascope, a telescope that uses Earth's atmosphere as a lens to achieve enormous magnification. He covers the history of telescopes and his path to the idea, plus Sol-scope and Jupiter-scope variants.

Kurzgesagt's hour-long animated film that compresses Earth's 4.5 billion year history into one hour, roughly a million years per second. It follows the evolution of life through to humanity's tiny final stretch.

Kurzgesagt explains stellar engines such as the Shkadov thruster and Caplan thruster, which could move the Sun and solar system across the galaxy over millions of years to avoid hazards and reach new regions.

A PBS Space Time episode explaining how space and time swap roles inside a black hole's event horizon. It is part of the channel's black hole series.

An Isaac Arthur episode on civilizations in the dark, post-stellar universe, including black hole farming, accretion disks and the Penrose process as energy sources.

Veritasium explains what a black hole should look like, using J.P. Luminet's 1979 work and a cardboard 3D model to show how light bends around it. It was made just as the first black hole image was released.

Kurzgesagt lays out a speculative plan to terraform Venus, covering its hostile atmosphere and how it might be made Earth-like, with a sources page linked.

A minutephysics explainer showing that the Moon's path around the Sun is not a spiral but closer to a 12-sided polygon with curved corners. It argues the Moon arguably orbits the Sun rather than the Earth.

A PBS Space Time episode asking whether Venus would be a better colonization target than Mars. It covers Venus's habitable altitudes, floating balloon habitats, and the term surfacism.

Isaac Arthur surveys the popular proposed solutions to the Fermi Paradox in a 71-minute compendium. He weighs the strengths and weaknesses of each argument.

PBS Space Time introduces Miguel Alcubierre's warp drive, explaining how spacetime itself could be warped rather than moving a ship through it, and whether it is physically possible.

A PBS Space Time episode hosted by Gabe Perez-Giz on the nature of spacetime and whether space and time are fundamental. It builds up reference frames and causality in a short, dense format.

PBS Space Time explains what happens as you approach and cross a black hole's event horizon, using Penrose diagrams and light cones as the tool for understanding spacetime there.

PBS Space Time explains Stephen Hawking's prediction of Hawking radiation and how black holes can emit radiation and slowly evaporate. It goes beyond the common particle-antiparticle analogy.

Astrophysicist David Kipping presents the halo drive, a proposed way to propel a starship to a good fraction of light speed by gaining energy from a black hole. The video is based on his peer-reviewed paper and explains why energy is the main obstacle to interstellar flight.

A minutephysics explainer on why the planets orbit in a flat plane. It shows how conserved angular momentum flattens a collapsing cloud of matter into a disk.

A PBS Space Time episode asking what black holes really are and whether events can happen inside them. It covers event horizons, time dilation and common misconceptions about black holes.

PBS Space Time examines the interstellar object 'Oumuamua and the popular theories about it, including the light-sail hypothesis. It argues that a natural rock is the likeliest explanation.

Isaac Arthur examines the Dark Forest theory, Cixin Liu's proposed solution to the Fermi Paradox in which civilizations stay silent and may destroy any that reveal themselves. He tests the theory's underlying assumptions and arguments.

An Isaac Arthur episode on arcologies, self-sufficient habitats that could house whole cities, on Earth or on harsh worlds. It covers how such structures might work and what limits their size.

A short Kurzgesagt animation explaining the Great Filter, the idea that finding alien life might be bad news because it implies something usually destroys civilizations. It connects the concept to the Fermi paradox.