Quantized space-time and redshift.

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Discussion Overview

The discussion revolves around the implications of quantized space-time as proposed in Loop Quantum Gravity and Spin Foam theories, particularly in relation to the redshift of light from distant astronomical objects. Participants explore how the quantization of space-time might affect the energy and frequency of photons as they traverse expanding space-time, raising questions about the nature of light, energy conservation, and the effects of mass on light propagation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that if space-time is quantized, then photons from distant stars, which originated in younger domains with smaller units of space-time, must traverse larger units as they approach us, leading to redshift.
  • Others argue that if the speed of light is invariant, then photons must decrease in energy (and thus increase in wavelength) to maintain this speed across expanding space-time.
  • A participant suggests that the stretching of space-time could explain cosmological redshift without relying solely on the Doppler effect or "tired light" theories.
  • One participant extends the discussion by proposing that if space-time can modify the energy of light, then mass could affect light's properties without invoking gravitational effects, suggesting a model of gravitational lensing based on space-time density gradients.
  • Another participant questions the notion of space being quantized in discrete Planck-scale steps, indicating uncertainty about this aspect of Loop Quantum Gravity.

Areas of Agreement / Disagreement

Participants express a range of views on the implications of quantized space-time and its effects on light and energy. There is no consensus on the validity of the proposed ideas, and multiple competing interpretations remain present throughout the discussion.

Contextual Notes

Some claims depend on specific interpretations of Loop Quantum Gravity and the nature of space-time, which may not be universally accepted. The discussion includes speculative ideas about the relationship between gravitational and inertial mass, which are not resolved.

  • #31
turbo-1 said:
Here's a link to an article about a bright young Greek Physicist working in Canada. There are still experiments in the works that might probe the fine structure of spacetime...GLAST (scheduled for 2006) may be able to detect whether gamma rays of very short wavelength can be slowed by interference with space-time at very small scales.

http://www.greece.gr/GLOBAL_GREECE/SPOTLIGHT/thinkingatthespeedoflight.stm?content_ID=16
One piece of good news - for some of us! - is that the only likely accessible* regime where LQG, String/M Theory, whatever, may be tested (in the next century or three) is high energy astrophysics (and gravity wave detectors) - GLAST, AMANDA, the various cosmic ray observatories (including the gamma ones); LISA, LIGO, ... If history is any guide, anyone of these will quite likely turn up quite unanticipated phenomena (and maybe also constrain some 'unified physics' out of the ballpark), showing yet again that the universe is richer, more complex, more wonderful than we puny Homo sap. mammals can even imagine.

*some possible 'local' ones: investigations into short-range deviations from inverse square for gravity, something unexpected from the LHC, even a 'routine' two-more-decimal-points study of something already 'well known'
 
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