Trouble for discrete space-time?

In summary: So if we could just probe sufficiently small, we would be able to detect these fluctuations.In summary, the article discusses an experiment that failed to detect a supposed blurring of light, and suggests that this may be due to new unified field theories being ruled out by the experiment. However, String Theory suggests that the fluctuations described in QM may actually be detectable at very small scales, and so this issue may still be unresolved.
Astronomy news on Phys.org
  • #2
One must first explain the disagreement between the theoretical energy density of spacetime, 1093 gm/cm3, and the measured value, 10-28 gm/cm3.
 
  • #3
The cited reference is not the article. It is a paraphrase of the paper, and the paraphrasing is not accurate at all.

Quantum mechanics (QM) does not predict any kind of blurring of light as described in the article. Relativity does not make that prediction either. So failure to detect the "blurring" experimentally is not a problem for existing accepted theory.

On the other hand, such blurring may be a prediction of some of the new classes of unified field theories which are being floated. If so, such theories might be ruled out by this experiment.

Essentially, QM has managed to fend off 75 years of attacks from all quarters. Current theory is remarkably consistent with all experimental evidence. As to the comment about energy density being off by 135 powers of 10, I don't think this is a disparity that everyone agrees even exists. But I guess it is open to debate.
 
  • #4
The vacuum energy problem is more of a desire than a fact. Physicists would like to think that they can compute vacuum energy density, so they devised a heuristic argument from QM and got that huge number... so the question is "is there really a huge vacuum energy we haven't detected", "does the idea of vacuum energy even make sense", or "what is the missing piece to the argument that gives reasonable results".


In all likelyhood, the "yes" answer goes to the last of those 3 questions, since it seems reasonable that an accurate vacumm energy theory would require general relativity which has resisted integration with quantum theories, so the heuristic argument breaks because it is based on a realm where we have no consistent theory.

Hurkyl
 
  • #5
I haven't read the whole article, but String Theory could explain this. You see, Quantum Mechanics does predict powerful fluctuations of spacetime, but these occur at sizes smaller than a Planck's size. String Theory dictates that - while this would happen, at sizes smaller than a Planck's size - there is nothing smaller than a Planck's size.
 

1) What is discrete space-time?

Discrete space-time is a concept in physics that suggests that space and time are not continuous, but rather made up of individual units or "chunks". This is in contrast to the traditional view of space and time as continuous and infinitely divisible.

2) What is the significance of discrete space-time?

The idea of discrete space-time has significant implications for our understanding of the fundamental nature of the universe. It could help explain certain phenomena, such as the quantization of energy in quantum mechanics, and provide a foundation for theories of quantum gravity.

3) How is discrete space-time related to quantum mechanics?

Quantum mechanics is based on the idea that energy is quantized, or exists in discrete units. This aligns with the concept of discrete space-time, as it suggests that space and time are also quantized in a similar way. This connection has led to the development of theories such as loop quantum gravity and causal set theory.

4) Can discrete space-time be tested or observed?

Currently, there is no experimental evidence for discrete space-time. However, there are ongoing efforts to test this concept through experiments such as high-energy collisions and gravitational wave observations. These experiments could potentially provide evidence for the discrete nature of space and time.

5) What are the potential challenges or limitations of discrete space-time?

One of the main challenges of discrete space-time is reconciling it with the theory of general relativity, which describes gravity as a continuous curvature of space-time. There is also the question of how to merge discrete space-time with other fundamental theories, such as quantum mechanics. Additionally, there is currently no consensus among scientists on whether space-time is truly discrete or continuous, and further research and evidence is needed to fully understand this concept.

Similar threads

  • Astronomy and Astrophysics
Replies
10
Views
2K
  • Astronomy and Astrophysics
Replies
28
Views
2K
Replies
2
Views
222
  • Astronomy and Astrophysics
Replies
4
Views
1K
  • General Engineering
Replies
0
Views
682
  • Astronomy and Astrophysics
Replies
1
Views
1K
  • Quantum Interpretations and Foundations
Replies
29
Views
3K
Replies
12
Views
731
  • Quantum Physics
Replies
19
Views
1K
Replies
12
Views
1K
Back
Top