The Geometry of Causality on HackerTube: recommended by 2 Hacker News commenters across 2 separate months, 2017–2022.
explainer · intro · evergreen
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.
Used as a go-to reference for relativity arguments, such as spacetime intervals being the same for all observers, and as a suggested follow-up for physics fans.
6 Hacker News comments link this video. Each one links back to its thread.
As an aside, the PBS space time video The Speed of Light is NOT About Light : [link] As an aside to the aside - as I rewatch it I quickly notice how young he looks (and then note the date is 2015 on there - one of the early ones and the production is less refined). You may also like The Geometry of Causality ▶ this video
in ““I survived the TCP transition” (2013)” · View on HN
I spend pretty much every weekend watching (super dyslexic) hours and hours of "stuff" about quantum, form quantum biology to physics to astro, here are some good ones around humans and the universe. Some may not seem totally relevant but give foundational knowledge, suggest watching in order: - [link] - ▶ this video - [link] - [link] - [link] - [link] - [link] - [link]
in “Theories about a link between the human mind and quantum physics” · View on HN
PBS Space Time on the same subject: ▶ this video Minute Physics SpaceTime Globe (The best tool for understanding relativity I've ever seen.) [link]
in ““Diagram of All Space and Time” by Carl Sagan (1960s?)” · View on HN
But why do intelligent people want to believe that any such coherent stories can actually be told in real life? We all know it's impossible. Even basic questions such as "How old are you" become unanswerable. Really intelligent informed people know the relative scales involved. So if all of Star Wars were re-imagined to occur using reasonable tech within the several cubic light years around Alpha Centauri, no speeds where severe relativistic time dilation effects are necessary for normal transportation. "How old are you" is readily answerable +/- a month for just about everyone, even most spacefarers. Heck, even the prequel trilogy makes more sense. (As Plinkett puts it, why are people on the planet of Naboo dying because they lack, "Space Supplies?" It would make a whole lot more sense if Naboo were an icy ball in the Oort cloud.) A person gets in a ship and travels at 1 G to another star, then turns around and comes back to Earth, they've aged 20 years, meanwhile on Earth 200 years have passed and all their friends are dead. Which timeline is real? How would any sci-fi tropes play out, in real life, in a universe of such inconsistencies? Another thing: I'm not an expert myself, but I can already tell that you don't even understand the big abstractions of relativity that well. The "Twin Paradox" is not actually a paradox. There is a global set of spacetime intervals which is consistent among all observers. It's only each observer's view of the spacetime interval which disagr
in “Discovered: The Most-Distant Solar System Object Ever Observed” · View on HN
> If there's anything the universe is, it's Eventually Consistent. Please disregard this inconsistency guff! The Universe isn't Eventually Consistent. It's simply consistent. What's really going on, is that some programmers don't understand relativity. Relativity doesn't actually say that everyone gets their own reality. There is a consistent consensual reality. Spacetime intervals are consistent between all observers. The time ordering of events changes depending on the observer's POV and relative motion, but there is an underlying consistent reality that's the same for everybody. [link] ▶ this video The "Spacetime Globe" by Minute Physics is the most helpful thing I've seen, flat out, for understanding relativity. > Knowledge of events in our universe is like an immutable, append-only database This is correct. Relativity just says that different users get different results, depending on how they query. The underlying database is the same for everybody. (Some parts of it are forbidden access, of course.) Programmers have been causing physicists to facepalm since at least the USENET days. I should know. I was one of them!
in “Discovered: The Most-Distant Solar System Object Ever Observed” · View on HN
Good post, I made it a bit more legible Are Space and Time An Illusion? | Space Time | PBS Digital Studios [link] The Geometry of Causality | Space Time ▶ this video The Quantum Experiment that Broke Reality | Space Time | PBS Digital Studios [link] Quantum Biology: An Introduction [link] Quantum Biology: The Hidden Nature of Nature [link] Consciousness: Explored and Explained [link] The Mind After Midnight: Where Do You Go When You Go to Sleep? [link] Rebooting the Cosmos: Is the Universe the Ultimate Computer? [link]
in “Theories about a link between the human mind and quantum physics” · View on HN