a few questions for relativity

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    Jerry
    Participant

    The first postulate of Einstein’s Special Relativity was at first known as the Principle of Relativity. This discovery was attributed to Galileo a few centuries before, that “the laws of physics are the same in all inertial frames“, or worded differently, that “all inertial frames of reference are equally valid“. This means there isn’t a universal frame of reference with which to measure the velocity of objects, that all objects exist and travel relative to all other objects, and any point of reference could arbitrarily be considered “stationary”. Actually, this is quite possibly the only truth found in Special Relativity.

    So how to know how fast a given object actually travels? According to what frame? This seems initially easy to choose, since we live on the earth’s surface, this is the frame we almost always consider. Why would we choose any other frame? It’s the “obvious choice”. However, if we observe the positions of objects without the frame of earth, such as in outer space, the velocity of everything seems unclear.

    How could we know the velocity of any one object in outer space? Understanding the implications of this simple question seems to “delve into” one of the original problems Galilean Relativity (which was Einstein’s first premise of Special Relativity) was thought of to solve. Whether that object is a planet, a star, a meteor, atom, particle, spacecraft, or anything else that physically exists within reality.

    There seem a few ways to disprove Special Relativity. One way is to simply try to find the velocity of a given object. How difficult is that though? If we think we’ve found the velocity of an object, we could always ask, “what is that object’s velocity relative to?” We’ll find that there isn’t a “one and only” valid frame of reference. Any velocity of something is a velocity that is relative to something else.

    This one simple consideration or question seems to illustrate the impossibility of how to know the position or velocity of a given object without direct reference to another object or frame. If a spacecraft is within highly minute decimal places away from reaching the velocity of light, traveling at a constant velocity, why isn’t the spacecraft essentially just as stationary as every other object that doesn’t accelerate within a given inertial frame? That a given object is also relative to literally all objects within every other perspective?

    The “velocity of light” is often expressed through the use of the symbol “c”. So what if there’s a spacecraft traveling near c, almost reaching c, and while almost there, it simply starts to somewhat “coast” at a constant velocity? How is this spacecraft experiencing a “coasting effect” within an inertial frame, different from how another object in outer space may exist, through its own inertial frame traveling at a constant velocity, of which we could theoretically say is just as “stationary”? What could prevent the spacecraft from existing and traveling within other different, yet valid, inertial frames? Throughout the universe, a given object that travels at a constant velocity is essentially just as “stationary” as any other object that doesn’t accelerate.

  • a few questions for relativity

    Jerry updated 3 weeks, 6 days ago 2 Members · 7 Replies
  • Ken

    Member
    January 6, 2022 at 3:24 pm

    Jerry,

    Concerning your question about “How can we determine the velocity of an Inertial Frame”,

    let us consider the 1905 SRT function called “The Law of Aberration” that predicts the “true declination” (∠φ’) of any star in the inertial frame of local stars as a function of the “observed declination”(∠φ) and orbital velocity (v) of the Earth’s inertial frame. For example:

    1905 SRT Law of Aberration: ∠φ’ = Acos[(Cos(φ) – (v/c)) / (1 – (Cos(φ) * (v/c)))] where for a “Wave Normal” observation of a star made by an Observer on Earth is seen to have a declination (∠φ) = 90° wrt the velocity vector (x-axis) and where ∠φ must be smaller than the “true declination” (∠φ’).

    In this example, the prediction of the “true declination” (∠φ’) is determined to be reliable within one milliarc second(0.001 arcsec.) for all local stars in the Earth’s orbital plane at the time of year when its observed location (∠φ) is “Wave Normal” (i.e. is perpendicular = 90°) to the Earth’s velocity vector.

    I will argue that the validity of this prediction of ∠φ’ based upon a clearly defined relative velocity (v) is not important to an engineer or scientist who is responsible for prediction of the observed or true declination or position of the star. It is only important for that scientist to be able to understand how to support proactive management through the practical use of “best practices” and available predictive models to make reliable predictions. Thus, it is more important to be a Critical Thinker who is able to evaluate evidence of the heuristic significance, reliability, capability and limitations of available predictive models.

    • Jerry

      Organizer
      January 7, 2022 at 1:30 am

      Hi Ken. Please forgive my mathematical ignorance. 🙂 I have to admit that most of what you wrote I didn’t understand. Perhaps I could if I were to learn the definitions to the technical terminology and symbolism, and how they correlate with each other within the scientific and mathematical “framework”.

      I had asked a slightly different question that is added in italics, of “How can we determine the velocity of an object within an inertial frame?”

      Here’s a similar question, that seems to answer the first, “How to know the position or velocity of a given object without direct reference to another object or frame?”

      Aren’t all inertial frames equally valid? If a given object travels at a constant velocity at almost the velocity of light, couldn’t we technically consider it just as “stationary” as all other objects throughout the universe that don’t accelerate?

      Thanks for responding, Ken.

      Did you agree with much that I had written at the top of this conversation?

  • Ken

    Member
    January 7, 2022 at 1:54 pm

    Jerry,

    You inquired: “How to know the position or velocity of a given object without direct reference to another object or frame?”

    My answer is “You unequivocally cannot determine your velocity in outer space if you are not within range of another object (such as a star or another light source) that is in another inertial frame”.

    However, I believe it would be more useful for the Relativity group to spend it’s time on critical analysis of existing predictive models that attempt to predict the velocity (v) or declination (∠φ or ∠φ’) of a space ship that probably will be traveling between the stars that include our sun during this third millennium.

    • Jerry

      Organizer
      January 8, 2022 at 4:36 am

      Thanks, Ken.

      The first answer you provided for my inquiry, seems to agree with the same view I had previously expressed with what seems my “rhetorical question”. That is, (in statement form), “to know the position or velocity of a given object, requires a direct reference to another object or frame.”

      To consider your answer a bit further though, if a spacecraft were in outer space, far away from anything observable, such as planets or stars, to know its position or velocity definitely is impossible to know. At least, it could appear that way, since there isn’t anything else around to compare it to. If the spacecraft isn’t accelerating, it could seem to exist as “stationary”, or it could travel at almost the velocity of light at a <i style=”background-color: transparent; font-family: inherit; font-size: inherit;”>constant velocity. That each scenario is virtually indistinguishable to the other. This, of course, is essentially the truth that Galilean Relativity (and the first postulate of Special Relativity) states.

      <font face=”inherit”>I would definitely endorse the view that critical analysis is most valuable and necessary to advance the sciences. Of course, physics is a vast field, with countless interconnected instances of accurate knowledge. However, theoretical physics, over at least the last century, </font><font face=”inherit” style=”background-color: transparent; font-family: inherit; font-size: inherit;”>has often accepted multiple </font>unverifiable<font face=”inherit” style=”background-color: transparent; font-family: inherit; font-size: inherit;”> hypotheses, many of which there isn’t any possible way of which to provide adequate evidence. </font>

      <font face=”inherit” style=”background-color: transparent; font-family: inherit; font-size: inherit;”>Of course, mathematics is highly necessary within the field of physics. I personally tend towards the idea that words and concepts have also had the capacity to convey accurate ideas, and to increase our understanding of our world and universe. </font>

      <font face=”inherit” style=”background-color: transparent; font-family: inherit; font-size: inherit;”>Just a few thoughts. </font>

  • Ken

    Member
    January 8, 2022 at 2:26 pm

    Jerry,

    I agree: “physics is a vast field, with countless interconnected instances of accurate knowledge. However, theoretical physics, over at least the last century, <font face=””inherit”” transparent;=”” font-family:=”” inherit;=”” font-size:=”” inherit;”=”” style=”background-color: transparent; font-size: inherit;”>has often accepted multiple </font>unverifiable<font face=””inherit”” transparent;=”” font-family:=”” inherit;=”” font-size:=”” inherit;”=”” style=”background-color: transparent; font-size: inherit;”> hypotheses, many of which there isn’t any possible way of which to provide adequate evidence”.</font>

    <font face=””inherit”” transparent;=”” font-family:=”” inherit;=”” font-size:=”” inherit;”=”” style=”background-color: transparent; font-size: inherit;”>However, I believe we should concentrate on solving one issue in one theory such as “1905 SRT” at a time. For example, how can you determine the velocity (v’) of your space craft if you are on a voyage from our home solar system to another local solar system? My answer is you can use a “best practice” SR model that predicts stellar aberration and / or frequency shifts of starlight from a star in that other solar system. In this context, you will measure your velocity (v’) as change in distance (dl’) divided by change in time (dt) = dl’ / dt’ and an observer that is “stationary” in the inertial frame of the local stars will measure your velocity as dl / dt. In special relativity, your velocity v’ = dl’ / dt’ is defined as dl / dt. In other words, velocity cannot be defined without reference to another inertial frame that measures your velocity as the same as you measure it. Thus, asking the question “what is your velocity” without reference to another reference frame is nonsense because you cannot define velocity in this scenario. Also in this scenario, you cannot just assume that you are not moving and are “stationary in your universe” just because you cannot detect EMF signals (e.g. light or radio signals) from your universe. This assumption in 1905 SRT “IS WRONG” and has led to the “TWIN PARADOX”. Another version of reciprocity is needed that does not assume that your space ship is stationary (v = dl/dt = 0 km/sec) and the local stars are moving at velocity (v’ = dl’/dt’ = c/2 km’/sec’). This other version by definition must measure your velocity as (v’ = dl’ / dt’ = c/2 km’/sec’) = (v = dl / dt = c/2 km/sec) as measured by an observer that is “stationary” in the inertial frame of your local stars.</font>

    <font face=””inherit”” transparent;=”” font-family:=”” inherit;=”” font-size:=”” inherit;”=”” style=”background-color: transparent; font-size: inherit;”>
    </font>

    <font face=””inherit”” transparent;=”” font-family:=”” inherit;=”” font-size:=”” inherit;”=”” style=”background-color: transparent; font-size: inherit;”>P.S. I would not take this same position concerning the definition velocity in other fields of physics such as quantum mechanics. </font>

    • Jerry

      Organizer
      June 5, 2022 at 9:44 pm

      Hi Ken.

      Much of what you’ve said, when it hasn’t been what seems quite complex math, is what one of my main points was, that you mentioned above there, “asking the question “what is your velocity” without reference to another
      reference frame is nonsense because you cannot define velocity in this
      scenario. Also in this scenario, you cannot just assume that you are
      not moving and are “stationary in your universe” just because you cannot
      detect EMF signals (e.g. light or radio signals) from your universe
      “.

      I have a question for you that I’m surprisingly unclear about. Is Special Relativity a theory you accept as accurate at any level?

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