Thank you all for your thoughtful rebuttals, which eventually convicted me of the non-contradictory nature of a small velocity for the tiniest body or even at rest (zero velocity) unless the body is not completely converted and disappears, together with the hypothetical contradiction.
I have...
Replying to Ibix and Dale.
You should consider this as a "gedankenexperiment", as was the one of Einstein.
Then, what is strange, or paradoxical, is what concerns the remaining energy-mass, which is "slow".
Let's take another, simpler, case. The body has a dynamite charge which explodes sending...
After emitting two photons (or any other kind of energy) in the direction of motion and in the opposite direction, the velocity of the body (a big charged and unstable particle) remains unchanged, while the kinetic energy decreases. This entails a decrement of the rest mass, or of the inertia of...
A possibility is that, together with many other articles that have been translated from English in that magazine issues, also Liuzzo's one was originally in English and, as often occurs, badly translated (without her checking!)
I wanna try to ask to the redaction, on the behalf of the Principle...
This is an extract from Liuzzo’s article “L’ombra del buco nero e la foto del secolo”, published on Magazine Micromega, 4/2019. I copied it from the ebook I’ve bought today. It is not available online. She is speaking about the famous photo...
“L’immagine ci dà inoltre un’altra informazione...
Problem Statement: It is possible to describe synchrotron radiation as caused by a loss of electrical charge of relativistic particles that are moving in a magnetic field?
Relevant Equations: E = mc2
An Italian expert of black hole M87 (Elisabetta Liuzzo) explains that the expected axial...
Thank you Ibix and Dale. Absolute circularly accelerated motion here is specular to relative uniform motion (in a qualitative Galileian sense of having or not having a velocity, that is just a matter of reference systems, not of invariance).
If the reference system O' associated with the probe...
I refer to the second paragraph of 1916's book, "Die Grundlage der allgemeinen Relativitätstheorie", translated here.
First issue
There are two distant stellar bodies, with unchanging shapes: S₁ (spherical) and S₂ (ellipsoidal), made of the same amount and kind of matter. Their centres of mass...
This is true, of course, because further reflections would convict us that mass and internal energy should be invariant (substantially the same invariant).
The reader of Einstein's paper only understands what he wrote: that the observer in motion calculates a decrease in kinetic energy not due...
Thank you very much Fresh_42 for your in-depth exam. Along with this translation, we could reason that Einstein's calculation would hold for any kind of transition from any kind of emitted energy (included thermal) even though it is not eventually converted in radiant energy.
So, E = mc² is...
At the end of the (fourth), 1905’s E=mc² paper Einstein claimed: “The fact that the energy withdrawn from the body becomes energy of radiation evidently makes no difference”. This sounds odd to me, given that the change L(γ-1) in kinetic energy resulted from calculating radiation energy. Light...
The reference system of the “fast” object Measures a velocity c respect to the photon. It’s time is relented only if watched by another reference system, but it’s own time “proper time” is unchanged and its “perceptions” are unchanged. Given that a photon don’t have a reference system, we can’t...
Thank you Dale and Orodruin. I see now there is no paradox given that a single photon can’t undergo pair production. The paradox would have been of events (pair production) occurring for an observer but not for another one with only a slow motion. I was aware that energy of photons depend from...
A monochromatic gamma light source S emits photons with spherical symmetry. These photons have a little less energy than necessary to permit formation of particle - antiparticle couples (electron-positron couple) or “EPCs”. An inertial observer O moves towards S with a small fraction of light...
I don't understand what actually this sentence implies:
1. anisotropic respect to the Jupiter--> Earth and Earth --> Jupiter directions? This is totally arbitrary to me given that absolute space doesn't exist. Any anisotropy could be used to establish preferential landmarks or directions.
2...
I can't read the tons of posts and replies about one-way light speed in this forum. I was criticised once for sustaining light speed should be equal in both outward and return trips and Einstein's method of syncing clocks as the only reasonable one. Then I studied some scientific articles gently...
The trouble is the following: nobody was yet able to measure the one way travel time of flight and the light speed because this kind of time synchronisation requires apriori assumptions on the speed which ought to get measured.
Don't know who has a wrong idea of an event. Time and space in the...
Exactly, the spark-event occurs at the same time in the same X position where M° is sitting, but there is an offset in the Y axis: M is at +Δy° whereas M' is at -Δy° with Δy° << Δxₘ (distance between mirrors). M and M' have zero speed in the y° direction, from the POV of M°'s frame. So they...
Absolutely YES: we are not talking of the same scenario. My scenario is the following (perfectly symmetric): 2 spaceships, four mirrors, two detectors (one for each spaceship and observer)
M and M' are sitting in the middle of two transparent spaceships. The two spaceships are equal and are...
This could be true only if referred to the evaluation of one's and other's detector: M and M' both say their own detector receive two light signals simultaneously, coming from their own mirrors, provided they hear two simultaneous chimes (and see two simultaneous LED blinkings into their own...
I want to propose a more symmetrical setting. A single event "Spark" is caused by friction in the same time and place: when M and M' are passing in front of each other and sratch two flints, causing a single spark. Both M and M' stand in the middle between two hyperbolic mirrors which reflect a...
So it is the time of passenger - as evaluated by a platform observer - which slows down (and vice versa); not the time as evalued by the passenger himself.
Nobody experiments a change in his local-personal-time. In the inertial motion the two observers can evaluate each other's clock only during...
Thank you PeterDonis. This is the kind of answer I hoped. Rotational effects are not due to far Universe-stars. It is a local effect. Thus, what holds for the true Universe is presumably or reasonably valid for a flat & empty universe, in contrast with Mach's principle. Furthermore rotation and...
Is there any physics approach useful to establish what should happen to a Newton's water bucketful rotating in a hypothetically empty universe (but for the bucket)? What the bucket would be rotating respect to in that one-bucket-universe? Everything rotating seems to have absolute (not relative)...
I'm not sure they can ignore a series of frames S'B & S'C given their velocity is increasing at constant rate.
Everything about B and C is contracted, but just from the point of view of A in S. As long as B & C were flying at the same and constant speed v respect to A, they wouldn't see nor...
Obviously! I grasped the necessity that there are as many instantaneous S's as many velocities acquired respect to S due to acceleration (these velocities are the same from the POV of S in every S time).
To imagine how this tenet works I think to how B and C evaluate (from S') their velocity...
So in different times during acceleration B and C remain in the same frame S' at any moment. So, why aren't their clocks anymore synchronised, given they were synchronised before, in the inertial system S? Why they get farther? Why they don't accelerate in the "same instant"? How is treated...
Thanks Advisor.
Reading the sentence "the rest length between the two has increased in the frames in which they are momentarily at rest (S′)" (underlined bold mine) I have to deduce that B and C are flying in two different frames, first because their distance is increasing (even though I don't...
Okay. The mirror can be considered as a second source, then the radio signal repetitor devise is only to synchronize clocks at very great distances. But Ockham razor's rule plus symmetry of space prevent me to consider different speeds for the +x and -x directions. Consider that which is the +x...