[verzali]

The question seems to me not why there is a speed of causality, but why the speed has this particular number. And it's not clear we know why that is, any more than we know why the proton mass is about 1836 times greater than the electron mass.

[JdeBP]

It's difficult to say that it has any given number, since our measurement units for both time and space are derived from it (via a short detour to the size of Terra, in the 18th century). It can have any finite number you like, just adjust the metre and second to match.

* 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. (-:

[lordfrito]

> One physics convention just sets its value to 1.

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.

[sroelants]

This convention of units is called "natural units", and it also sets a bunch of other units to be 1, depending on the flavor (planck's constant, boltzmann's constant, etc...)

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".

[linuxdude314]

This is the normal implication with C constant. Nothing is different.

[jzl]

Search YouTube for “universe fine tuning.” Then come back here in a few years when you’ve gotten through everything. :)

[tasty_freeze]

No thanks. Every time I hear the argument brought up, the person putting it forward says it like it is a mic drop moment and they never discuss the counter arguments. It is effective for people who haven't heard the argument before or haven't thought it through.

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.

[GoblinSlayer]

Presumably charge is a property of electromagnetic field, so it's expected that they match.

[jzl]

Fine tuning is a pretty broad concept and is mostly orthogonal to religious beliefs.

[Jsebast24]

If the speed of causality were to suddenly change by whatever factor, would we notice it?

[hinkley]

You know how the OceanGate sub imploded so fast that their brains didn't even have time to register they were dead?

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.

[BurningFrog]

It appears as "c" in the important equation E = mc².

So I expect it would change a lot.

[deniscoady]

If you are willing to accept multiverses then isn't this solved by the Anthropic principle where the speed of causality (or mass of the proton) is what it is, simply because it can sustain the evolution of eventual observers?

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.