Matter outside of the territory under consideration. Where are we?

[Serge58]

After an analogy with air and water waves, which are limited in speed by the density of the medium in which they travel, I was wondering if there were variations in the "density" of the vacuum of space which might cause light, or any electromagnetic waves for this matter, to vary in speed.

In reply to this comment harrylin cleverley quoted Einstein from 1920:

Einstein phrased it in 1920 as follows: "the metrical qualities of the continuum of space-time [..] are partly conditioned by the matter existing outside of the territory under consideration."

Therefore, Where are we today with the understanding of this matter outside of the territory under consideration?

 

[Nugatory]

Therefore, Where are we today with the understanding of this matter outside of the territory under consideration?

There's no great mystery here. Suppose that the "territory under consideration" is the space near a massive body; the massive body produces gravitational effects within that area. A near-trivial example would be the Schwarzschild solution - it's a vacuum solution so applies in the empty space around the matter that's responsible for the gravitational field.

 

[bcrowell]

After an analogy with air and water waves, which are limited in speed by the density of the medium in which they travel, I was wondering if there were variations in the "density" of the vacuum of space which might cause light, or any electromagnetic waves for this matter, to vary in speed.

The equivalence principle basically says that this can never be the case.

What Einstein probably had in mind was spacetime curvature, not the speed of light. (But it would be helpful to have some more context.)

 

[Serge58]

I think i didn't write my question properly. I'll try again on a new tread.

 

[sardar]

I can say that our understanding of the matter outside of the territory under consideration has greatly advanced since Einstein's time. We now know that the density of the vacuum of space is not uniform and can vary due to the presence of matter and energy. This concept is known as the "quantum vacuum" and is a fundamental aspect of modern physics.

The quantum vacuum is not completely empty, but rather is filled with virtual particles that constantly pop in and out of existence. These particles can affect the properties of space-time, such as its curvature and the speed of light. This has been confirmed by various experiments, such as the Casimir effect, which demonstrates the influence of the quantum vacuum on the behavior of two closely spaced metal plates.

Furthermore, our understanding of the matter outside of the territory under consideration has also been greatly enhanced by the development of general relativity and quantum field theory. These theories have allowed us to better understand the relationship between matter, energy, and the fabric of space-time.

However, there is still much to be explored and understood about the matter outside of the territory under consideration. The concept of dark matter and dark energy, which make up a large portion of the universe, is still a mystery to scientists. These substances have a significant influence on the behavior of the universe, and their exact nature is still being studied.

In conclusion, our understanding of the matter outside of the territory under consideration has greatly advanced since Einstein's time, but there is still much to be discovered and understood. As scientists continue to study and explore the complexities of the quantum vacuum and the universe, we will gain a deeper understanding of the matter outside of the territory under consideration.