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Anonymous_Otters t1_jb1crzq wrote

Reply to comment by pepe_silvia_12 in Does the age of the universe depends on where you are? by _bidooflr_

The flow of time is relative, so time is flowing at different rates at different places depending on the curvature of the universe in respective locations and on relative velocity. Only when you get into the same gravity well in the same place can two objects be considered to be more or less at the same time. As soon as they leave the same gravity well or travel at different relative velocities, they are technically now in different times until they meet up again. That said, every single molecule, atom, subatomic particle is technically running at slightly different times even within the same object. Space and time are, under general relativity, considered inextricably linked, so can be thought of as the same thing. Changing space changes time, so being in even a slightly different spaces means you are in a slightly different timr. This is why the cosmic microwave background radiation is used as a universal resting position to make some sort of standard time.

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Melkor15 t1_jb2286m wrote

This is truly amazing, thanks for your time explaining it.

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JasonDJ t1_jb30ffx wrote

So, wait a tick…

If you’ve got two watches in perfect sync on earth, and one leaves at a low rate of speed (well below speed of light), where is “out” of our gravity well that they are significantly losing sync, and would that still hold true with atomic clocks?

Assuming we had some sort of hypothetical instantaneous radio communication, would the communications be distorted once one side were in a different gravity well?

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Anonymous_Otters t1_jb313dn wrote

Atomic clocks are routinely used to measure the time difference between things on the surface of earth and things in orbit. The difference of the flow of time needs to be calibrated or else things like GPS wouldn't work right.

If communication were instant, how it would work would I guess depend on what you were using, since that isn't supposed to be possible.

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Hapankaali t1_jb70cm0 wrote

Instantaneous communication leads to quite a few problems of the "grandfather paradox" type. For example, the relativity of simultaneity means that according to some observers, the response to a query will be given before the query itself.

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Grimyak t1_jb26yje wrote

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.

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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.

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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.

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criminally_inane t1_jb2sb76 wrote

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

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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.

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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.

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OberonsGhost t1_jb3i8rp wrote

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

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SewFine69420 t1_jb3yev6 wrote

This time stuff has been gnawing on my brain for years, as a fiction writer. In my writing I have beings that were born in different parts of the galaxy, some born on things that weren’t even planets or near a star, so I have a hard time trying to put forth how old they are, except to say they are ancient or ageless or something vague like that. If I try to put a number of years on them I immediately think “okay well they aren’t from earth nor are they on earth, so what exactly is a year in this context”. I have yet to settle on a solution.

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andreasbeer1981 t1_jb24q7l wrote

So if a tree falls and there is noone to hear, it doesn't make a sound.

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Anonymous_Otters t1_jb274k3 wrote

So, what I described it the opposite of that assertion. No one has to be around to observe difference in time, it is inherent to the fabric of reality.

Also, if a tree falls in the woods and there is no one to hear it, it still makes a sound as sound is the propagation of a fluid compression wave, which occurs regardless of an observer. What it doesn't make is a noise, since noise is the conscious experience constructed by the brain using the stimulus of sound.

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