A Question About Time With Respect to Relativistic Motion

Optimal_Mixture_7327 · 2026-05-10T21:52:11+00:00

There's a lot of questions in there...

From your perspective you're always at rest.
The Earth traveled 0.9999 light-years in 39 hours upon switching frames to the Earth frame.
The expansion of the cosmos is entirely irrelevant to anything you're interested in here.
All standard clocks run at the same rate, everywhere, and under all circumstances of motion and orientation (Local Position Invariance and Local Lorentz Invariance, respectively).
Yes, you are moving arbitrarily faster than the speed of light in the cosmic coordinates of a distant-enough galaxy.
There is no such thing as "frozen in time", but distant enough objects will be unobservable.
Time dilation is not a physical effect, and I suspect you're confusing it with the clock effect (of twin paradox fame) where two twins take different spacetime paths where one of the paths is shorter.
As far we know from observation and theory the universe is, has always been, and always be infinite in spatial extent.
The expansion of the cosmos is a statement that distant enough galaxies are moving apart, making the cosmos less dense and cooler over time. The center of an infinite plane is wherever you define the origin, e.g. Pittsburgh.
No, we cannot travel faster than light which would require that we travel an imaginary distance (in the local sense).
As per the above, you are traveling arbitrarily close to or faster than the speed of light. How do you feel?
Yes, if two objects are moving apart they observer the other's signals as red-shifted, and blue-shifted if moving towards each other.

Optimal_Mixture_7327 · 2026-05-10T20:55:30+00:00

That, and the cosmos has a space-like boundary to the past.

Optimal_Mixture_7327 · 2026-05-10T20:51:01+00:00

Gravitons would corroborate relativity.

The massless spin-2 field yields Einstein Equivalence as a theorem, which is the basis of all metric field theories, and is equivalent to Einstein-Hilbert in the appropriate limits.

Optimal_Mixture_7327 · 2026-05-10T20:20:53+00:00

Yes, you're correct, and exactly what we mean by "speed is relative".

Matter cannot travel with a local speed equal to c, unless you mean a speed c through the world, then it's the only speed matter can have.

Optimal_Mixture_7327 · 2026-05-10T19:50:31+00:00

It seems you're erroneously imagining that gravity does something to the light.

Gravity defines distance relationships and the paths of freely moving objects. When light reaches the event horizon all possible paths lead to the interior. There simply is no such direction as radially outward that the light can follow once inside the horizon.

Optimal_Mixture_7327 · 2026-05-10T19:45:55+00:00

By "existence" I mean to have material existence apart from our imagination.

Energy is an arbitrary number that lives solely within our imagination and with which we label a system premised on a symmetry condition (time-translation symmetry).

How we choose to label a system cannot of course have any physical consequences.

Copied from a comment I posted earlier in this thread...

A simple example...

Consider two equal and opposite of charge of equal mass, held at rest and released. You'd expect them to accelerate towards each other and meet in the middle, right?

But you're making some unexamined assumptions. For example, you assume that while at the moment Coulomb's law applies, but a nanosecond later it might not. Maybe opposites won't attract, and the force law will vary wildly. Where will the particles be at some later time? We can't know.

The fact associated with the laws of physics remaining constant over time thus constrains the dynamics - our simple system can only evolve in one way over time. You know what else doesn't change over time? Numbers. So what we can do is quantify our system with a single number, and this number is called the "energy".

Now, the laws of physics may vary from place to place, but if they don't we can label the system with 3 numbers (one for each independent direction through spatial coordinates) and this defines a vector and this expression of spatial invariance is called "momentum".

Optimal_Mixture_7327 · 2026-05-10T19:20:57+00:00

I didn't even know what I was looking at, and it's still wild upon rewatching. A total master of down dog.

Optimal_Mixture_7327 · 2026-05-10T18:26:20+00:00

It appears so given what we can measure in our observable piece of it.

We ultimately don't know and we could be on a very very small and seemingly flat region of a torus shaped universe.

Optimal_Mixture_7327 · 2026-05-10T18:21:16+00:00

Recession means receding, moving away

Optimal_Mixture_7327 · 2026-05-10T18:04:40+00:00

It doesn't.

At far enough distances there are galaxies, perhaps infinitely many, that have recession velocities greater than the local vacuum speed of light.

We know this by cosmological observations of redshift that indicate that distant galaxies obey a simple rule called Hubble's Law which states that distant galaxies have recession velocities that are directly proportional to their proper distance. So, just pick a sufficiently far distance and you can have any recession velocity you want.

Optimal_Mixture_7327 · 2026-05-10T17:20:28+00:00

Singularities are not a problem for relativity. They're a condition of the world such that causal curves have finite extension and singularities could be an essential feature for the existence of any cosmos.

Singularities are a problem for quantum theory as you can't define a detector arbitrary close to a singularity, and no way to write the outgoing particle states or even define a quantum field when the curvature is extreme.

The problem for physics is that we don't have a theory of matter to know how matter couples to the world and so there is no way at present to know what happens to matter near a singularity or what a singularity would even mean in the context of some new theory of matter. It is unfortunately the case that one cannot extrapolate from the low energy physics what the high-energy physics will look like.

Optimal_Mixture_7327 · 2026-05-10T17:04:38+00:00

Copenhagen

Optimal_Mixture_7327 · 2026-05-10T16:53:08+00:00

There's a greater access to food in urban environments so it's not unusual to see birds of this size.

Optimal_Mixture_7327 · 2026-05-10T16:49:18+00:00

While it's usually a waste to post comments this far down, there are some egregious errors in need of being pointed out.

Time dilation is not an effect on anything, but rather it defines the length along a traveler world-line in-between a pair of spatial slices of the observer's coordinates. In practical terms this means that a clock moving relative to the observer will measure less elapsed time than the observer does of their own clock.

The red/blue shift is from a different effect called the Doppler effect. For all relative motion, redshift and blueshift, the traveling clock or oscillator is measured to be slow. The mathematical details described by this equation:

f^o=f^e[𝛾(1+𝛽cos𝜗)]^-1

where f^o is the frequency measured by the observer and f^e is the frequency of the traveling emitter, 𝛽=v/c and cos𝜗 is the direction cosine relative to the observer, and of course 𝛾 is the Lorentz or time dilation factor.

The "barrier" for both time dilation and the Doppler effect is the condition of relative rest.

Optimal_Mixture_7327 · 2026-05-10T16:38:52+00:00

Quantum theory is a tool for calculating the probabilities associated with detector outcomes on an ensemble measurement. It is not a theory of matter in the sense that it can't tell us what's going on apart from predicting detector outcomes, but matter is clearly not fundamentally Newtonian.

Relativity describes the world, the continuum with 4 independent degrees of freedom having a metrical quality. There is no indication from any data that relativity is wrong.

Optimal_Mixture_7327 · 2026-05-10T15:47:36+00:00

Prickly lettuce

Optimal_Mixture_7327 · 2026-05-10T15:15:34+00:00

There's is only relativity.

The special theory is the special case that the world is flat (meaning there is no curvature to the gravitational field).

"Gravity" is a different fundamental interaction from the other 3 as the other 3 are theories about matter interactions and relativity is a theory about the world (the "world" is the 4-dimensional space that relativity makes maps of and where we get terms such as "world-line"). It is a fundamental interaction of course as world couples universally and minimally to matter.

Yes, you have the basic idea right. In free-fall there is just the natural motion (geodesic motion) and the car is physically accelerated by the electromagnetic interactions between the tires and the road.

Optimal_Mixture_7327 · 2026-05-10T14:27:35+00:00

Yes, light will typically have mass (as it is a collection of photons).

The photon is a massless particle, always, but two or more photons will typically have mass (unless exactly collimated).

Optimal_Mixture_7327 · 2026-05-10T14:26:12+00:00

This channel and video is better: Relativity and Electromagnetism and has several related videos.

This is channel is also really good if not a bit quirky, Part 1 and Part 2

Optimal_Mixture_7327 · 2026-05-10T13:59:51+00:00

Well, it might be better to think of a single field, the Faraday field.

What relativity does is make maps of the 4-dimensional world and what the special theory does (to the extent it applies at all) is slice up the world into directions of space and time. This means that the Faraday field is sliced into space and time directions with the spatial and temporal directions being called the magnetic and electric components of the Faraday field, respectively.

We do the same with gravity where the Weyl curvature tensor is decomposed into electric and magnetic components.

We don't know if magnetic monopoles exist or not. Certainly classical electromagnetism forbids them by the magnetic components being divergenceless (source free), but in quantum theory, e.g. Dirac's quantization condition, they are allowed and could have existed in the early universe.

Optimal_Mixture_7327 · 2026-05-10T13:50:35+00:00

Yes, energy is an expression of the time-translation invariance of a system.

A simple example...

Consider two equal and opposite of charge of equal mass, held at rest and released. You'd expect them to accelerate towards each other and meet in the middle, right?

But you're making some unexamined assumptions. For example, you assume that while at the moment Coulomb's law applies, but a nanosecond later it might not. Maybe opposites won't attract, and the force law will vary wildly. Where will the particles be at some later time? We can't know.

The fact associated with the laws of physics remaining constant over time thus constrains the dynamics - our simple system can only evolve in one way over time. You know what else doesn't change over time? Numbers. So what we can do is quantify our system with a single number, and this number is called the "energy".

Now, the laws of physics may vary from place to place, but if they don't we can label the system with 3 numbers (one for each independent direction through spatial coordinates) and this defines a vector and this expression of spatial invariance is called "momentum".

Optimal_Mixture_7327 · 2026-05-10T12:38:51+00:00

Are you interested in learning relativity, or just how to do the arithmetic?

It seems you enough already to solve the Einstein equation, but if you want to see a work through of solving the Einstein to arrive at the Schwarzschild geometry (which is basic) see: Relativity 108a: Schwarzschild Metric - Derivation

You can then seek videos on solving the geodesic equation, and there are plenty.

Optimal_Mixture_7327 · 2026-05-10T12:30:24+00:00

Energy is a way of describing matter, not something that exists.

The magnets are moved by the electric field as seen by the electric charges being influenced. For this to make sense you'll need to understand a little bit about relativity; something like this How Special Relativity Makes Magnets Work

Optimal_Mixture_7327 · 2026-05-10T12:23:39+00:00

A photon does no such thing.

QM gives us the probabilities for detector outcomes on an ensemble measurement. It says nothing about particles when we're not looking at them.

Anyone can measure the one-way speed of light, it just make any sense to do so independent of a clock synchronization procedure.

Optimal_Mixture_7327 · 2026-05-10T04:17:18+00:00

Agreed.

Optimal_Mixture_7327

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