Is light necessary for the existence of spacetime?

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Discussion Overview

The discussion revolves around the relationship between light and spacetime, exploring whether spacetime can exist independently of light and how the presence of light influences our understanding of spacetime. Participants raise questions about the nature of spacetime, the role of light, and the implications of black holes in this context.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants question whether spacetime can exist without light, suggesting that spacetime is the medium through which light travels.
  • One participant proposes that a black hole could be considered a spacetime without light.
  • There is a discussion about whether spacetime can be accurately modeled without including the effects of light from the outset.
  • Another participant asserts that light does not affect spacetime significantly since it has no mass, but acknowledges that light has a small effect on the curvature of spacetime due to its energy.
  • Questions are raised about the production of photons and their relationship to the physical universe, including whether light is the most abundant substance or if it relates to the concept of grains of spacetime.
  • Some participants clarify that the presence of light is not particularly special, and that the maximum speed for all objects in the universe coincides with the speed of light.
  • There is a mention of the complexities involved in discussing properties of distant objects in relation to spacetime.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of light for the existence of spacetime, with some arguing that light is not essential while others explore its implications. The discussion remains unresolved with multiple competing perspectives on the relationship between light and spacetime.

Contextual Notes

Participants highlight limitations in understanding the effects of light on spacetime, including the need for clarity on which effects are being referenced and the challenges of discussing distant objects in a local frame.

dubmugga
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...there is darkness and spacetime

but there is still light...

In a semi dark room there is light and i can make the shape of objects out. I turn the switch on and the room is flooded with light but what happened ? Did the energy levels of the existing photons in the semi dark room just get boosted ?

With that in mind...

...is it possible to extricate spacetime without light given that spacetime is the medium through which light travels. Is a black hole spacetime without light ?

What does the presence of light suggest then about the relationship between spacetime and light ?

Is spacetime merely the effect of photonic mass and gravity traveling in 3+1d ?

Is it possible to accurately model spacetime without including the effect of light from the outset ?

If spacetime is inflating at faster than lightspeed from the inside. How do we ever manage to see light from vast distances given the the distance needed to travel is always increasing ?

...just some random questions i been thinking about I hope someone can help me with
 
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dubmugga said:
...there is darkness and spacetime
but there is still light...
In a semi dark room there is light and i can make the shape of objects out. I turn the switch on and the room is flooded with light but what happened ? Did the energy levels of the existing photons in the semi dark room just get boosted ?
No, the light bulb produces new photons in vastly greater quanities than existed in the room before you threw the switch.
Boosting the energy of the existing photon would result in the shifting of their frequencies (they would shift to the blue end of the spectrum).
 
dubmugga said:
...is it possible to extricate spacetime without light given that spacetime is the medium through which light travels. Is a black hole spacetime without light ?
I don't think the word 'extricate' makes sense in your sentence. A non-spinning uncharged black hole (commonly called the Schwarzschild solution) is a spacetime described by the Schwarzschild metric.

What does the presence of light suggest then about the relationship between spacetime and light ?
The presence of light is nothing special really, not even that light travels at the speed c is too special. What is remarkable is the fact that there is a maximum speed for all objects in the universe. This happens to match the speed of light since the quanta of the electromagnetic field is massless and therefore moves at that speed.

Is spacetime merely the effect of photonic mass and gravity traveling in 3+1d ?
No.

Is it possible to accurately model spacetime without including the effect of light from the outset ?
Which effect of light?

If spacetime is inflating at faster than lightspeed from the inside. How do we ever manage to see light from vast distances given the the distance needed to travel is always increasing ?
The most accurate model of spacetime is a "4-dimensional pseudo-Riemannian manifold." One consequence of this is that it doesn't make too much sense to speak of properties of objects that aren't in your local frame; i.e. the energy-momentum of a photon that is many light-years away.
...just some random questions i been thinking about I hope someone can help me with

I hope I have been of some help.
 
why yes, thank you masudr...

...so light in no way affects spacetime given that it has no mass and gravity

but if it did then ?

Is light as a particle the most abundant substance in the universe or is it possibly grains of spacetime or something else ?
 
thank you too Janus...

so do we know how photons are produced from non existence to visibly physical ?
 
dubmugga said:
why yes, thank you masudr...
...so light in no way affects spacetime given that it has no mass and gravity
but if it did then ?
Is light as a particle the most abundant substance in the universe or is it possibly grains of spacetime or something else ?

Light has a small effect on the curvature of space-time, because it has energy - just not very much energy compared to matter. Light is in no way necessary to have space-time.
 

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