Question Speed of Light and Time Dilation

[CryptoCraig]

The speed of light and time dilation seem to be connected in many texts. In these texts, is time dilation actually infinite at the speed of light, or is this just a reference used for simplification?

If time dilation actually occurs with the speed of an object relative to an observer, why do we not assume that light itself doesn't undergo time dilation effects?

When looking into deep space, we see objects that are billions of LY away. Usually this is followed by a statement similar to, we are seeing these objects as they were, billions of years ago.

But if light experienced time dilation, wouldn't that light reach our instruments in zero time?

 

[Gibsense]

The speed of light and time dilation seem to be connected in many texts. In these texts, is time dilation actually infinite at the speed of light, or is this just a reference used for simplification?

Light does not 'experience' time. There's a thought: Infinite slowing = zero, er not quite.[url=https://postimages.org/][/URL]

OB represents a photon. The horizontal axis is distance. Vertical is Time. All things having a speed must exist on the circumference. Distance OB is 1 Light Year. This is just an expression of Special Relativity. NB all my stuff needs checking as most is ex my imagination and not text book
I think the circumference can be thought of as space. Imagine, as the universe expands per second say the circumference increases at the Hubble constant (If you insert the age of the universe for time OA). Therefore the idea that SR only refers to local stuff doesn't seem correct as the diagram can be extended to represent all current space

 

[CryptoCraig]

All things having a speed must exist on the circumference. Distance OB is 1 Light Year. This is just an expression of Special Relativity. NB all my stuff needs checking as most is ex my imagination and not text book
I think the circumference can be thought of as space. Imagine, as the universe expands per second say the circumference increases at the Hubble constant (If you insert the age of the universe for time OA). Therefore the idea that SR only refers to local stuff doesn't seem correct as the diagram can be extended to represent all current space

Gibsense,

Please, help me understand the diagram better. I have a couple of questions.

"All things having a speed..." meaning all matter as well as photons must reside on the circumference?

...or is the circumference is essentially the "boundary" in which any matter can exist due to light speed being the speed limit and given the number of spacetime intervals?

Let's say that time cannot possibly go in reverse, or there is only the present moment (except for memories), then the horizontal axis line would be the lowest point on the diagram?

 

[Gibsense]

Ok, first thanks for asking -

"All things having a speed..." meaning all matter as well as photons must reside on the circumference?

Correct. The diagram is a 2D illustration of a hypersphere existing in 4D Space. A Sphere would be a cross-section of a hypersphere. To understand better look up Hypersphere on Wikipedia or similar. You will learn that the SURFACE of a hypersphere is 3-dimensional - our sort of space. So that means the circumference of the circle illustrates our space.
Strictly speaking, the hypersphere is the surface of a hyperball.

...or is the circumference is essentially the "boundary" in which any matter can exist due to light speed being the speed limit and given the number of spacetime intervals?

This can get confusing. Imagine you were in that circumference line (just 1 dimension, a line but representing our 3D space) then you could travel around it forever (repeating the same round journey over and over) then you could not find a boundary and you would determine the universe was curved - spherical.

However, let's say you were a superbeing in 4D outside the universe looking at the whole thing you would see that those in it were confined within the circumference. From that perspective, you could consider it a boundary but the word is usually reserved for something that limits from within 3D space

Let's say that time cannot possibly go in reverse, or there is only the present moment (except for memories), then the horizontal axis line would be the lowest point on the diagram

The radius of the circle is (as the diagram shows) both distance and time. But note that any radius can be delegated as time or as distance. That is a light year can be considered as a year and vice versa (check this statement - it is correct!).
But always time runs at 90 degrees to space

This bit is crucial to understand (But is my personal take that I think is obvious). Time is a process, not a dimension. It is an action occurring in 4D Euclidian space within the Ball the surface of which is the sphere. This means it has to be positive as there is no such process as Unaction. Don't confuse this with rewinding stuff like making a broken egg whole - that is not negative time. (according to me)

However, the position opposite A on the diagram but on the circumference has a radius that is pointing down in an opposite direction to the radius at A. Time there is still a positive process but because the direction is opposite it is designated as negative.

The negative in this sense is still a positive process and not a rewinding of events. You should note that it is all relative. If you were a person travelling through 3D space (on the circumference) positive time would rotate with you and you would regard the opposite hemisphere as negative. (and anyone opposite would regard you as negative)

Whilst we are at it it is worth mentioning something I have not ventured into before but it seems to me to be a good 'maybe'. Let's say the universe responds as a hypersphere - mathematically but that it acts out the processes as if projecting the hemispheres onto a plane that devides the hemispheres. That way the processes of anti-particles and particles will act out in time in an everyday way. (the negative time changes an electron to a positron and vice versa). Not only that but the 'relativity rotation' of speeding stuff in space is rotated in situ (it doesn't have to jump to the other side of the universe to match up the rotation angle. It's a subject I have been thinking about how to express. Not doing so well on that so far but its an early shot.