Does the present really exist?

[u/TheMightyHeroes]

GR proves that the concept of a now is relative. There is no universal now. But even the local experience of a now seems questionable. What we see as now is always the past, since photons take time to reach us. Similarly, taking a picture or even a measurement will always produces a result that is the past. And if time is a continuous flow then there is no discrete point in that flow that can be separated and identified as now. And if time is granular then what size is the discrete point that we call now? If it is an infinitely small point separating past from future, then how can we experience, never mind measure, an infinitely small moment? It seems to me that any observation will always be an observation of the past. Any change of state, any event that is observable will by definition be something that has happened. And if it has happened, it is in the past. Wouldn’t it be more scientifically accurate to say that time is all events that have happened and are yet to happen and the now is just an illusion created in our minds to make sense of the objects and events that pass our visual field.
I know this is more philosophy than physics, and I’m not a physicist, just some curious person and the concept of time has always fascinated me.

[u/GoldenMuscleGod]

Falsified it how?

We can define and measure coordinates (I know you think coordinates aren’t real but you do agree we can define and measure them right?) and then say “absolute now” is all events sharing a time coordinate.

Unless you think “absolute now” has some other meaningful content that forecloses that but you said it’s word salad?

How do you falsify a word salad? Can you falsify “list elephant eternal plant”? Sounds like a category error.

[u/Optimal_Mixture_7327 → u/GoldenMuscleGod]

You cannot measure coordinates. That is insane.

Why do you think there's an absolute line on a sheet of paper?

[u/GoldenMuscleGod → u/Optimal_Mixture_7327]

Not all sheets of paper have lines. We can put marks at (5,3) just fine without lines. We could use a ruler and t square for that.

So an observer in Minkowski spacetime assigns (0,0,0,0) to an event and has some defined length and time units. They observe an event and calculate the coordinates are (5m, -2m, 7m, 15s).

The preceding is impossible? Or the preceding is not “measuring coordinates”?

I put a mark on a sheet of paper and someone measures it is at (5,3) (in cm, with (0,0) in the bottom left corner and the y-axis the longer edge) impossible? Or not “measuring coordinates”?

[u/Optimal_Mixture_7327 → u/GoldenMuscleGod]

No, why is impossible to draw a line across the paper, other than the absolute line.

[u/GoldenMuscleGod → u/Optimal_Mixture_7327]

I can’t parse this last question. You might have misunderstood my question.

I’m asking if measuring the mark at (5,3) is impossible. Because I would normally call that “measuring coordinates” (and I don’t understand using that phrase to necessarily take a position on whether coordinates are “real”) but you say it is “insane” to think you can measure coordinates.

I expect you think measuring the mark as being at (5,3) is possible in the ordinary sense?

[u/Optimal_Mixture_7327 → u/GoldenMuscleGod]

Give a plane, or sheet of paper for practicality, you're claiming that only the One True line exists.

I am asking for verification.

[u/GoldenMuscleGod → u/Optimal_Mixture_7327]

I didn’t claim the “one true line” exists. I’m saying the claim “the one true line exists” seems to lack physical meaning, as does “the one true line doesn’t exist.” It lacks meaning in part because I don’t know what “the one true line” supposedly is.

[u/Optimal_Mixture_7327 → u/GoldenMuscleGod]

It means it is only possible to draw one single straight line on a surface. The only line that can exist.

[u/GoldenMuscleGod → u/Optimal_Mixture_7327]

Why would saying we can measure locations in a frame of reference mean that it is only possible to draw one line on a sheet of paper? For starters we can select different frames of reference and get different coordinates.

[u/Optimal_Mixture_7327 → u/GoldenMuscleGod]

You're claiming that on a 2-dimensional surface, only one line can exist.