Spacetime as a dynamic object, and the unfinished attempt to quantise it.
12 topics · 15 curated works
No prior grounding assumed.
What do gravitational waves sound like?
Tessa Baker (The Royal Institution) · 2023
Explains that a merger's waveform encodes the masses and spins of the objects that produced it, so gravitational waves are a measurement channel…
Assumes you know the vocabulary.
What Is String Theory?
Joseph Polchinski · 1994
Introduces string theory to physicists outside the field, arguing that requiring a consistent quantum theory of one-dimensional objects forces…
+2 more at this level
Primary sources and full treatments.
On the Electrodynamics of Moving Bodies
Albert Einstein · 1905
Special relativity derived from two postulates, dissolving absolute time without introducing a single new force.
+10 more at this level
12 of 15 works
Tessa Baker (The Royal Institution)
Explains that a merger's waveform encodes the masses and spins of the objects that produced it, so gravitational waves are a measurement channel rather than a curiosity.
link checked 17 Sept 2026Joseph Polchinski
Introduces string theory to physicists outside the field, arguing that requiring a consistent quantum theory of one-dimensional objects forces general relativity and gauge symmetry to appear together.
link checked 17 Sept 2026Notes on this copyPBS Space Time
Shows that gravity in general relativity is not a force but the shape of spacetime, so a freely falling body is travelling the straightest available path through a curved geometry.
link checked 17 Sept 2026Notes on this copyJerome Gauntlett (The Royal Institution)
Argues that black holes are where general relativity and quantum mechanics contradict each other, and that their entropy is the most concrete clue to whatever theory reconciles the two.
link checked 17 Sept 2026Albert Einstein
Special relativity derived from two postulates, dissolving absolute time without introducing a single new force.
Assumes Maxwell's equations and ordinary algebra — famously no tensors, which is why it is still readable
31 pageslink checked 17 Sept 2026Notes on this copyAlbert Einstein
Replaces the flat, fixed spacetime of special relativity with a curved spacetime whose geometry is itself shaped by matter and energy.
46 pageslink checked 17 Sept 2026Notes on this copyLeonard Susskind
Argues that the entropy bound on black holes implies all the information inside any region of space can be encoded on its boundary, so the interior is in some sense redundant.
14 pageslink checked 17 Sept 2026Notes on this copyJuan Maldacena
Conjectures an exact equivalence between a gravitational theory in a curved space and an ordinary quantum field theory living on its boundary, one dimension down.
20 pageslink checked 17 Sept 2026Notes on this copyCarlo Rovelli
Argues that quantising general relativity directly, without first fixing a background spacetime, gives a theory where space itself is woven from discrete loops.
75 pageslink checked 17 Sept 2026Notes on this copySaul Perlmutter et al.
Uses distant exploding stars as standard candles to show the universe's expansion is speeding up, requiring a cosmological solution with a dominant dark-energy term.
37 pageslink checked 17 Sept 2026Notes on this copyMatthias Bartelmann & Peter Schneider
Shows that the faint, coherent distortion of background galaxy shapes by foreground mass can map the universe's dark matter directly, without assuming it emits light.
196 pageslink checked 17 Sept 2026Notes on this copySteven Carlip
Surveys the competing programmes for reconciling general relativity with quantum mechanics, and argues the shared open problems matter more than any single approach.
60 pageslink checked 17 Sept 2026Notes on this copy