It feels more intuitive to me when thinking about it as causality always unfolding around you at the same speed, no matter your own frame.
The constant c was not named for causality, but it is a nice coincidence.
If a neutron disappeared, you'd NEVER noticed that causality.
* https://www.youtube.com/watch?v=ZbGxXyqlhbU (FloatHeadPhysics on this)
One physics convention just sets its value to 1. All of those Minkowsky diagrams that we see are measured in light seconds on the space axis, in order to make c have the value of 1 space unit per time unit; so all of the graphical sheep, spaceships, cats, people, torches and stuff that are placed upon them are very much not to scale. (-:
Interesting. So c² would also equal 1. Which (in those scaled units) implies E = m.
This not only greatly simplifies the relationship but actually makes much more sense that way.
Not only does this clarify the relationships, but in many ways, these "natural constants" are an artifact from our past ignorance. Boltzmann's constant, in a way, is nothing more than a "conversion factor" that we hold over from the time when we believed temperature and energy to be two separate concepts. In the same way, the speed of light is an artifact from a time when we considered time and space to be distinct concepts, measuring them in distinct units, and needing a conversion factor (in units of distance/time) to map between them.
It's as if we would all collectively agree that the "up" direction, from now on, would be measured in floops, and the slope of a hill would be measured in floops/meter.
From a philosophical point of view, it's not just saying "measure time in units such that c = 1". It's saying "let's consider time to be a distance, and measure it in the same units as we do the other ones".
So I expect it would change a lot.
If the basic laws of the universe change, we'll be disincorporated before we have a chance to know it's happening, because it will happen at whatever the speed of light is in the new balance, and the chemical processes that make us tick will change to other chemical processes that don't actually work anymore.
In the new universe silicon based life might function. Or stars might not work anymore.
Here is an example. The charge of an electron is exactly the opposite of the charge of a proton, to within measurement error (like ten digits). This is simply something which has been measured, but physics has no explanation for why they are the same. Getting to the point, what is more likely: that a God created it that way in order to achieve His goals, or that there is some reason connecting the two charges such that they must be of exactly the same magnitude but we just haven't figured it out?
I'm putting my money on the latter. If there is an all-powerful creator, there is no reason to have fine tuning at all -- He could just force the desired behavior and outcome.
I don't think the numbers independently are valuable, but together the constants of physics are tuned to support life. To be honest, I dislike the Anthropic principle as a generalizable cop-out, but it nonetheless works.
The fact that time even exists is implied by / a result of causal actions having some finite propagation time.
Imagine a universe simulated in a computer with “ticks” where the entire state is updated.
It would be different to ours, but it would work just fine.
The fact that causal effects happen in the next tick means some minimal time has passed. So in your definition causality can cover the entirety of a finite universe in an incredibly short amount of time (one tick). But it seems like that's not the same as covering the entirety of a finite universe in zero time. In that case, every result would happen within the same tick as its cause.
A simulation could use particles with attributes like position, velocity, and also a "sum of forces". Then each update has the following steps:
1. Reset the sum of forces for all particles to zero.
2. For all particles, add the contribution to the forces on it from all other particles.
3. For all particles, update the next particle position based on the collected forces.
In the above, there's no intermediate state between updates, everything moves to the next position synchronously from the perspective of in-universe observers. (The external simulation can update particles one-at-a-time, but this is not an "observable" inside the simulation.)
I think I know what you're getting at, but somehow the phrasing bothers me, as if there is meta-time or as if cause and effect have time between them... for the photon at light speed, time isn't passing, it's emitted and then zero "time" later it hits something very far away.
It's more like we somehow need to think of cause and effect chains that have orderings without time.
I wonder if future generations will ever look back and casually quip something about "well they believed X existed, that was their problem, it all makes intuitive sense if you just..."
So what exactly are you talking about?
he’s talking about the photons frame of reference
However, you have to be careful with terminology. There is no inertial frame co-moving with the photon. All we can say is: as a massive particle gets faster relative to an observer's frame, the time it experiences relative to the observer's frame becomes shorter, and in the limit, as it approaches the speed of light (but never reaches c), the experienced relative time approaches zero (but never reaches 0).
This is well explained by Don Lincoln on the Fermilab YT channel:
Do photons experience time?
If there’s some universal limit for causality itself, then light just happens to be the fastest thing among all the other things subject to causality.
Other similar particles, like the W and Z bosons, are manifestations of the weak field. Since that field breaks the symmetry, those particles have mass and move slower.
BTW, that symmetry breaking is the very same one that physicists talk about when we discuss the Higgs boson.
Can you unbox this a little? I think I may just have Friday brain, but I'm having some difficulty convincing myself in the moment that infinite-speed causality development would prevent time.
The best definition I think I've seen is to view the universe as a partially ordered set of events, meaning that you can only order events (in time) if they're within each other's cones of causality. Outside of that you cannot say which happened first. That's the partially ordered part.
But even that is incomplete and arguably even self-referential. What's a "cone of causality" (without relying on causality)?
Also, there's the issue of what exactly time is and whether events are time-symmetric or not. Many physicists seem to view time as an emergent rather than fundamental property of our Universe.
Time is a relationship between clocks.. beyond that, yes, it's hard to say exactly.
Time seems to be what prevents everything from happening at once.
I can't even describe 'happen' without using verb tenses, which represent time.
If you want to simulate a giant world with millions of players, you either have to slow down the frequency at which you update the world to give the computer enough time to do the computation, or you have to introduce some sort of speed of causality in the game in order to be able to distribute the computation across multiple nodes.
If you have an infinite speed of causality, a server may need to receive data from all the servers. In the worst case, all servers will need to receive data from all the servers.
With finite speed of causality, a server only needs to receive data from the servers that simulate parts of the world that are nearby.