relativity

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.

Veritasium explains magnetism as a consequence of special relativity. Length contraction of moving charges makes a current in a wire attract or repel a nearby moving charge.

The first of an eight-part ScienceClic series building general relativity, covering worldlines, proper time and coordinate systems with animated visualizations.

PBS Space Time explains how spacetime geometry and light cones determine the order of events and what can cause what. It visualizes causality in special relativity.

PBS Space Time argues that the speed of light is better understood as the speed of causality, the universal limit on how fast cause and effect propagate. Light travels at that speed because it is massless, but the limit itself is a property of spacetime.

A minutephysics explainer on the twins paradox in special relativity. It shows why the traveling twin ends up younger and how acceleration resolves the paradox.

ScienceClic explains why nothing can go faster than light by treating motion through space and time together, so everything moves at the speed of light through spacetime. It uses animated visuals to cover relativity basics in 12 minutes.

Sabine Hossenfelder explains how special relativity leads to the block universe, in which past, present and future all exist equally, and asks what that means for whether the past still exists.

Veritasium explains why the one-way speed of light has never been measured, only the round-trip speed, since measuring it requires synchronized clocks that assume the answer. It explores the implications for relativity.

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.

Veritasium explores why energy is not conserved in general relativity, using Emmy Noether's theorem linking symmetries to conservation laws. Physicists interviewed explain energy loss in an expanding universe.

Sabine Hossenfelder explains why she thinks faster-than-light travel may not be ruled out. She argues that the standard objections from special relativity are inconclusive.

A PBS Space Time episode explaining why faster-than-light travel is equivalent to travelling back in time, using relativity and Minkowski diagrams for different observers.

PBS Space Time explores whether time causes gravity, explaining that gravity does not truly warp the flow of time but arises from time gradients. It revisits how gravitational time dilation works in general relativity.

Veritasium explores what general relativity says about black holes, white holes and wormholes, with help from physicists Geraint Lewis and Juan Maldacena. It introduces Penrose diagrams and the idea that other universes may be implied.

PBS Space Time explains how general relativity permits warp drive in principle and covers recent theoretical advances toward solving the negative energy problem.

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.

A PBS Space Time episode asking what matter, mass, and energy really are, starting with inertial versus gravitational mass and what mass-energy equivalence means.

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.

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 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.

A Veritasium video touring Relativity Space and explaining why 3D printing whole rockets cuts tooling costs, allows rapid iteration, reduces part count and enables new designs. It includes an interview with Scott Manley on aerospace engineering.

A short clip from an ACM and Computer History Museum interview in which Leslie Lamport discusses writing his paper on time, clocks and the ordering of events. He explains its link to special relativity.

Tom Scott, with linguists Gretchen McCulloch and Molly Ruhl, examines whether the language you speak changes how you think. The short answer is mostly no, with caveats about the weak version of the Sapir-Whorf hypothesis.

AlphaPhoenix builds a scaled-down version of the Veritasium electricity thought experiment using about a kilometer of wire and an oscilloscope. He measures how the signal actually propagates and explains the result.

The first of Richard Feynman's 1964 Cornell Messenger Lectures, The Character of Physical Law, focusing on the law of gravitation. Feynman builds up from planetary motion to the nature of physical laws.

A restored HD upload of the 1983 BBC series Fun to Imagine, in which Richard Feynman talks informally about everyday science. Topics include jiggling atoms, fire, rubber bands, magnets, electricity, mirrors, seeing, big numbers and ways of thinking.

David Tong, a Cambridge theoretical physicist, explains at the Royal Institution that the fundamental building blocks of nature are quantum fields rather than particles. He covers what we know about these fields and how they fit into the Standard Model.

Physicist Carlo Rovelli gives a public lecture at the Royal Institution on how our understanding of time has changed, from Boltzmann and Einstein to quantum theory and loop quantum gravity. He blends physics, philosophy and art to argue that time is stranger than everyday intuition suggests.

Veritasium argues that electric energy is carried by fields around the wires rather than by electrons moving through them, using a thought experiment with a large circuit.

Sean Carroll introduces his video series on the biggest ideas in physics, such as symmetry, space and matter, as informal discussions with follow-up Q&A videos. This is the short opening video of the series.

AlphaPhoenix uses a custom high-speed measurement setup to watch voltage waves travel down wires and split at a fork. It answers how electricity knows where to go and how quickly that process happens.

A 1983 BBC interview in which Richard Feynman is asked how magnets work and explains why 'why' questions are hard to answer in everyday terms. He reflects on what counts as an explanation and the limits of analogy.

Physicist Angela Collier's roughly hour-long video on how string theory was hyped to the public and what that did to science communication. She traces the history of the theory as a narrative and argues it is interesting but was oversold.

3Blue1Brown visualizes Feynman's lecture on the refractive index, explaining why light appears to slow down in glass and why the effect depends on color. It builds the idea from waves produced by oscillating charges in the material.

Veritasium explains how trees lift water from roots to the top of tall trunks, using transpiration pull and the negative pressure that liquid water can sustain. It explains why trees do not need pumps or valves.

PBS Space Time explains Noether's theorem: conservation laws such as energy and momentum are consequences of deeper symmetries. It also covers why those laws hold only under certain conditions.

A short clip of Richard Feynman answering an interviewer's question about why magnets repel, explaining that a 'why' question depends on a shared framework of understanding. It illustrates how hard it is to explain fundamentals to a layperson.