Viewing a single comment thread. View all comments

Grimyak t1_jb26yje wrote

Reply to comment by Anonymous_Otters in Does the age of the universe depends on where you are? by _bidooflr_

I think of the "now" as a kind of unbroken fabric of causality. Although I guess with the universe expansion and stuff there are places that will float past the horizon where anything connected to our specific causality cannot interact.

Anyways in my mind "now" is more tied to cause and effect than it is strictly a time based measurement. As in "now" is simply the period where the "cause" side of cause and effect can be manipulated.

5

Anonymous_Otters t1_jb27sbx wrote

Causality is the reason for there being different nows since if causality existed irrespective of time then things outside of now, from the perspective of an observer, could causes changes too far away to have actually been caused by the observer if, say, information could propagate faster than light. The reason light speed is what it is is because light speed in a vacuum is the speed of causality.

Your definition doesn't make sense as the period where the causes can be manipulated since, for example, my observation of the light from a distant galaxy is completely unaffected by anything happening in my now since the "now" of the galaxy I'm observing occured billions of years ago from my now. Now is entirely relative. The only way I can see the now of the galaxy I'm looking at would be to go there, and by then the now I want to be part of would have passed.

22

Grimyak t1_jb2evbg wrote

I apologize for my poor explanation. I understand that there are regions in our universe where causality cannot apply due to distance and time limitations.

My intention was not to suggest that there is a single shared "now" across the universe. Rather, I meant that the local "now" we experience is the time period where object interactions and state changes occur.

In hindsight, my use of the phrase "unbroken fabric of causality" may have been misleading. What I intended to convey is that within its sphere of influence, causality remains unbroken and could be considered to have one "now" that bends and conforms to the fabric of space/time in that region. However, beyond a certain distance, causality no longer applies, as even light emitted from our location will never reach those areas. In my mind that place would have its own separate discreet "now" to ours.

3

criminally_inane t1_jb2sb76 wrote

But then there is a place in between here and there that shares a "now" with both.

2

Waste_Bin t1_jb3i7wb wrote

I prefer to think of it as three distinct points with three different horizons dependant on relative position and acceleration.

The "now" in-between the two is an artifact.

3

Grimyak t1_jb30k5j wrote

From a technical standpoint, every location has its own distinct area of influence, even if they have points that overlap each other. However, this doesn't contradict my earlier point as far as I can tell.

To illustrate this concept, imagine three circles that overlap in a linear fashion. The outer two circles extend inward, but do not touch. While an outer circle can interact with the portion of the inner circle that it overlaps with, the inner circle cannot transmit this information beyond the point where it is overlapped by the outer circle. Essentially, although each circle has the potential to overlap with another's influence, it is still unable to communicate or affect regions outside of its own radius.

1

OberonsGhost t1_jb3i8rp wrote

Can't causes be interconnected instantaneously due to quantum entanglement?

1