Physics in a universe with instant communication

Click For Summary

Discussion Overview

The discussion explores the implications of a hypothetical universe where instantaneous communication is possible. Participants consider how this scenario might alter the laws of physics, including concepts such as the speed of light, time dilation, and length contraction. The conversation touches on theoretical frameworks and the nature of simultaneity in such a universe.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that in a universe with instantaneous communication, the laws of physics would resemble Galilean relativity rather than Einstein's relativity, suggesting no relativistic effects like time dilation or length contraction.
  • Others argue that if the speed of light is not constant, the traditional relativistic equations would not apply, leading to a fundamentally different understanding of motion and interaction.
  • A participant questions the feasibility of such a universe, suggesting that if instantaneous communication were allowed, it could lead to a scenario where "everything will happen all at once," potentially negating the existence of a structured universe.
  • Another participant emphasizes the importance of distinguishing between "allowing instantaneous communication" and "requiring that all communication is instantaneous," indicating a need for clarity in the assumptions being made.

Areas of Agreement / Disagreement

Participants express differing views on the implications of instantaneous communication, with no consensus reached on how such a universe would function or whether it could exist at all.

Contextual Notes

The discussion relies on assumptions about the nature of communication and its effects on physical laws, which remain unresolved. The implications for chemistry and subatomic behavior in a non-relativistic framework are also noted as uncertain.

EnumaElish
Science Advisor
Messages
2,348
Reaction score
124
Faster-than-light communication is not allowed in this universe. Imagine a sister universe that looks much the same as ours but allows instant communication between any two points. In that universe, simultaneity can be established using instantaneous communication. How would that affect our* description of the universe through laws of physics? In such a universe, would speed of light still be constant? Would there be time dilation? Would objects elongate with velocity?
———
*Assuming human-like species would have evolved in such a universe.
 
Space news on Phys.org
That's the Galilean space-time of PHY101.
 
robphy said:
That's the Galilean space-time of PHY101.
What he said.

It's a perfectly consistent physics, basically the state of the art around the middle of the 19th century. There's Galilean relativity instead of Einstein's relativity, so no relativistic effects such as time dilation or length contraction. The speed of light is not constant because the law of addition of velocitiies is the Galilean ##w=u+v## instead of the relativistic ##w=(u+v)/(1+uv/c^2)## - the latter form doesn't even make sense if the speed of light is not constant.

As for what the universe would be like? We really don't know, because all of our theories about the behavior of subatomic particles are relativistic (as well as quantum mechanical). Thus that mid-19th century physics provides no basis for chemistry and many of the physical properties of matter.
 
Last edited:
EnumaElish said:
Faster-than-light communication is not allowed in this universe. Imagine a sister universe that looks much the same as ours but allows instant communication between any two points. In that universe, simultaneity can be established using instantaneous communication. How would that affect our* description of the universe through laws of physics? In such a universe, would speed of light still be constant? Would there be time dilation? Would objects elongate with velocity?
———
*Assuming human-like species would have evolved in such a universe.

In short if instantaneous communication is allowed then the Universe cannot exist because pretty much everything will happen all at once.
 
One should distinguish
"allowing instantaneous communication"
from
"requiring that all communication is instantaneous".
 
  • Like
Likes   Reactions: M Saad

Similar threads

  • · Replies 23 ·
Replies
23
Views
4K
  • · Replies 15 ·
Replies
15
Views
4K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 37 ·
2
Replies
37
Views
6K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 34 ·
2
Replies
34
Views
4K
  • · Replies 4 ·
Replies
4
Views
3K