There is no way to draw a single 17:33 consistent line across spacetime that all observers agree separates has happened from hasn't happened yet. The failure parade. Some physicists argued this was a mathematical convenience with no ontological weight. But no experiment has ever found a preferred frame that would let now become absolute again.Not correct. Such a frame is given by the Cosmic microwave background.
This video is AI generated, so should not be taken too seriously. It is a common error, so I point it out.
No, Roger, there isn't. Two frames $\Delta t$ apart show two (slightly) different pics, as I pointed out a while ago right on your blog. ... Do you now need an AI for locating such things too? on your own blog? ... Are you rich enough? ... is that why?
ReplyDelete--Ajit
Two frames may show different pics, but they agree on whether the CMB is stationary.
ReplyDeleteNope. They don't. Study the experimental observations. And, even the public opinions of the man (Nobel?). I did, before my first reply that bit ago.
ReplyDelete--Ajit
(Nobel -> Nobel laureate)
DeleteIf you have a citation to prove me wrong, go ahead and post it.
ReplyDeleteProving someone else wrong isn't so attractive a purpose; spelling out one's own position is .
DeleteSince I even today cannot upload _anything_ to arXiv, I only can (and am happy to) provide a citation to the following document:
https://drive.google.com/file/d/1xhm23COdHSjQxWKK4fsHRENJRiT4SOa2/view
--Ajit
From Google AI:
ReplyDelete**Roger is correct regarding the physics**, though the disagreement mostly comes down to semantics and what is meant by a "preferred" or "stationary" frame.
Here is how physics views the Cosmic Microwave Background (CMB) frame:
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## 1. Why Roger is Right: The CMB Frame Exists
There **is** a unique, physically defined reference frame in which the Cosmic Microwave Background radiation appears isotropic (the same temperature in all directions).
* **Measuring Motion:** If you travel relative to this frame, you observe a **Doppler dipole**—the CMB looks slightly warmer (blueshifted) in the direction you are moving and slightly cooler (redshifted) in the direction you are moving away from.
* **Cosmological Standard:** Because this frame exists everywhere in the observable universe, cosmologists use it as a standard "co-moving" rest frame to define cosmic time and measure the motion of galaxies.
---
## 2. Why It Doesn't Violate Relativity
Ajit's skepticism (and the AI video's point) usually stems from a common misconception about Special Relativity:
* **Special Relativity's Core Principle:** The laws of physics (like $E=mc^2$ or the speed of light $c$) are identical in **all** inertial reference frames. There is no "absolute" frame where the laws of physics behave differently or where you can perform a local experiment to determine absolute rest without looking outside.
* **Frame of Reference vs. Physical Matter:** The CMB is a physical background of photons filling the universe, not a property of spacetime itself. Measuring your velocity relative to the CMB is no different from measuring your velocity relative to the air inside an airplane cabin or the water in an ocean—it provides a convenient **material rest frame**, not an absolute coordinate system that changes fundamental physics.
---
## Summary
| Concept | Status | Explanation |
| --- | --- | --- |
| **Is there a frame where the CMB is at rest/isotropic?** | **Yes** | Roger is correct. We can measure our exact speed relative to it (~370 km/s) via the Doppler dipole. |
| **Is it an "absolute" frame that breaks Relativity?** | **No** | Physics equations and local laws remain identical in any inertial frame regardless of motion relative to the CMB. |