(From a friend one mine; I'm just hosting this here.)

Issue 1: Relativity of Simultaneousness:

Your buddy Einstein is riding the interstellar express train. All the lights are off, but just as it passes your observation platform, he turns on a lamp in the middle of the train. You and he have taken bets on which end of the train, front or back, will light up first. As expected, your video cameras on the platform record the rear of the train lighting up first, since, as the light spreads out from the original location of the lamp, the rear of the train moves slightly closer to the source, while the front end is moving away. However, Einstein reports that his equipment shows both ends lit up simultaneously.

Both of you are correct. In your reference frame the events "light reaches front of train" and "light reaches rear of train" are not simultaneous, even though in Einstein's they are are.

Issue 2: Superluminal Travel

View overconstrainederror.js
(function (global, binding, v8) {
const captureStackTrace = global.Error.captureStackTrace;
const defineProperty = global.Object.defineProperty;
const setPrototypeOf = global.Object.setPrototypeOf;
const Error = global.Error;
function OverconstrainedError(constraint, message = undefined) {
const obj = new Error();
// This complicated dance is necessary to emulate
View call-graph.svg
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Sorry, we cannot display this file.
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View to-run-2.yaml
DIR: dom/collections
HTMLCollection-as-proto-length-get-throws.html: [fail,]
HTMLCollection-supported-property-indices.html: [fail, Named versus indexed properties trickiness]
HTMLCollection-supported-property-names.html: [fail, Names vs. ids priority and effect on enumeration order]
domstringmap-supported-property-names.html: [fail, DOMStringMap not implemented]
DIR: dom/events
View promise-finally-observability.js
// Current spec
function finally(onFinally) {
let C = SpeciesConstructor(this);
return this.then(
x => new C(r => r(onFinally())).then(() => x),
e => new C(r => r(onFinally())).then(() => { throw e; })
// Proposed, but rejected (potentially because of a miscommunication) spec


async function* f() {
  const x = Promise.resolve(1);
  const y = Promise.resolve(2);
  const fromX = yield x;
  return y;
View URL.js
"use strict";
const conversions = require("webidl-conversions");
const utils = require("./utils.js");
const Impl = require(".//URL-impl.js");
const impl = utils.implSymbol;
function URL(url) {
if (!this || this[impl] || !(this instanceof URL)) {
View 1-service-worker.js
"use strict";
const worker = new Worker("worker.js");
self.onfetch = e => {
e.respondWith(new Promise(resolve => {
const guid = generateGUID();
worker.addEventListener("message", function messageListener({ data: { readableStream, messageId } }) {
if (messageId !== guid) {
View 1-service-worker.js
"use strict";
const worker = new Worker("worker.js");
self.onfetch = e => {
const transform = TransformStream.identity();
e.respondWith(new Response(transform.readable));
// Give the worker the writable end. An identity transform stream will just shuffle
// bytes written there into transform.readable.

Redirecting GitHub Pages after a repository move

The problem

You have a repository, call it alice/repo. You would like to transfer it to the user bob, so it will become bob/repo.

However, you make heavy use of the GitHub Pages feature, so that people are often accessing GitHub will helpfully redirect all of your repository stuff hosted on after the move, but will not redirect the GitHub Pages hosted on

The solution