Maartenn100

Certainly, one can view four-vectors as elements of an algebraic vector space equipped with a bilinear form (the Minkowski metric). From a pure math standpoint, that is an algebraic description of a set of vectors and their inner products. However, this algebraic structure also defines a specific kind of geometry—namely Minkowski geometry. In other words, once you endow a vector space with a metric, you move from “just algebra” into the realm of geometry—because that metric tells you how to measure intervals between vectors. Minkowski’s great insight was that this geometric viewpoint (treating time and space as a unified four-dimensional manifold) elegantly explains the relativistic effects of length contraction and time dilation as straightforward geometric consequences of that metric, rather than mere algebraic manipulations. So yes, four-vectors live in an “abstract multidimensional space,” but that metric is what allows us to interpret it geometrically. The geometry may differ from our usual Euclidean intuition—it’s a pseudo-Riemannian or Lorentzian geometry—but it is still very much a geometry. Thanks for your comment. Let me clarify a couple of points: First, regarding the idea that “Einstein said time is an illusion”: The commonly cited phrase comes from a letter Einstein wrote after the death of a friend, where he remarked something along the lines of “For us believing physicists, the distinction between past, present, and future is only a stubbornly persistent illusion.” It’s often paraphrased or taken somewhat out of context. Einstein was referencing the notion that in a four-dimensional spacetime picture, all events exist “at once” in the block-universe sense, so the usual way we divide events into past, present, and future can be seen as partly a feature of human perception. While he did say something close to “time is an illusion,” it wasn’t meant as a casual denial of time’s physical reality but rather an expression of how relativity treats all of spacetime as one geometric whole. Second, about “observing” the (3+1)-dimensional world: I agree that every real measurement inherently involves time. We always observe phenomena through a window of duration, however brief. What I’m emphasizing is that although our measurements happen in (3+1) dimensions, we don’t get to see the entire 4D spacetime manifold “all at once.” Instead, we experience one slice of it at a time and infer the rest from theory and indirect measurement. “Manifold,” as you say, is indeed a mathematical model. We can’t literally place it under a microscope. Yet it’s precisely that model (the 4D metric plus our experimental data) that unifies the separate measurements we take over time. This is why I referred to the 4D geometry as abstract and not directly visible in one go, because our sensory experience and measuring apparatus only ever sample events sequentially. So yes, we inevitably measure and perceive reality in (3+1)D segments, but that doesn’t mean we can lay out the entire 4D manifold in one visual scene. The manifold remains a powerful conceptual framework allowing us to interpret our sequential observations in a consistent, relativistic whole.

There is nothing morally wrong with it. But it tells you something about the true nature of it. Is it conceptual, this 4D geometry, or is it directly observable as a 4D manifold? The fact is, the 4D geometry not directly accessible when we are in our bodies. As Einstein said, time is an illusion, created by our brain and senses. Once we are out of body (see NDE's, deep meditation, or deep mystical psychedelic experiences) we experience 'all at once', 'all information immediately accessible', etc. We will experience the block universe, in my opinion.

I think what I mean is: you cannot observe the 4D metric directly as one 4D geometry. As this manifold. You can only observe and measure in 3D. This whole 4D geometry as a whole is not visible to us. It's an abstract geometry. You can't see the block universe. You can only see an unfolding of events moment by moment. You can't see the whole sequence at once. But in this 4D-geometry, all the events are accessible at once. as human observers, we perceive time in a sequential manner: one “now” after another. We don’t see the entire 4D structure at once; we only see slices of it in three dimensions, unfolding in what we call “the present moment.” Our senses are adapted to detect 3D space plus the passage of time. There’s no direct way to view or navigate the time dimension the way we do spatial dimensions. You can measure intervals and record events, allowing you to infer aspects of 4D geometry (such as proper time, spacelike separations, etc.), but you never literally “see” all four dimensions together. Abstract Geometry vs. Physical Observation The 4D metric (the mathematical description of spacetime distances) is an abstract object. It unifies space and time into a single geometric framework. Physically, you measure distances and durations in 3D space plus time. That’s why we say the 4D manifold is not directly visible: it’s a model capturing how these measurements fit together across all possible reference frames. we can only observe and measure slices of reality in 3D, one moment at a time, even though the underlying spacetime structure may be “there” in four dimensions all at once. I’d like to suggest a possible connection between the four-dimensional “block universe” of physics and those states sometimes described as timeless or eternal, especially in near-death experiences, deep meditation, or psychedelic journeys. In the relativistic block-universe view, spacetime is treated as a four-dimensional manifold where all events, past, present, and future, are laid out in a single, unchanging geometry. From our usual perspective, however, we perceive only one instant at a time, as though we’re watching individual frames of a film. We can never simultaneously witness the entire “reel.” That sequential flow is simply how our consciousness, anchored in a body, processes the dimension of time. Yet individuals who have undergone especially profound experiences—such as near-death states, intense meditation, or psychedelic visions—often report something radically different: a vivid sensation that time has dissolved, a feeling of union with everything, and a sense that all events and information are equally accessible “at once.” Some describe this as seeing beyond the linear progression of moments into a realm that contains all possible points in time. Philosophically, it’s easy to see how this might echo the block-universe idea. If time is a dimension woven together with space, then in principle, past, present, and future could coexist in a single geometric structure, even though we only experience them sequentially in our day-to-day lives. From this perspective, being embodied may act like a perceptual filter, limiting us to a 3D slice plus the passing of time. In extreme or altered states of consciousness, perhaps that filter loosens, letting us momentarily intuit something more akin to the four-dimensional reality underneath. Naturally, mainstream physics distinguishes between the mathematical framework of spacetime and the subjective realms of experience. Still, there is plenty of room in philosophy, metaphysics, and personal belief to explore whether these transcendent episodes are glimpses of the block universe or simply separate phenomena altogether.

Yes, that’s correct, but those spacetime distances are not directly visible. They can only be calculated. They do not belong to the immediately observable or measurable 3D reality of observers. It's an abstract distance. More absolute than our relative observable 3D observations of space and time. The true nature of these proper distances is conceptual. But more real, then our relativistic observations of space (and time).

But a reference frame is always required in order to talk about time and space coordinates; in that sense, the 'observer' is inevitably present.

(additional thoughts to the Timescape model of scientist David Wiltshire ) Did you know that we, as observers of space and time, have not only our own particular clock ‘(time is relative) , but we also have our own particular idea of what ‘standing still’ in non-moving uncurved flat spaces, means from our location in space (and time). In some sense, the flat Earthers are partly right… We have a particular local idea of what ‘standing still’ in flat unmoving spaces means and that’s our reference point for for seeing curved rotating objects and expanded spaces elsewhere. Wherever you are, you have a particular idea of straight uncurved spaces, that stands still. And that idea determines what you will observe outhere in space, moving, rotating, expanding And your local idea of a straight line that is not moving differs from the straight line that stands still of other observers with different clocks. You have not only a different clock (time is relative) you also have a differen ruler. (your local idea of unmoving eucledean space is relative) Let me explain with a well known example: You feel that you stand still in space on Earth, right? That’s your referenceframe right there, as an observer in space. When you start escaping Earth with your spaceship and reach escape velocity, you will see the curved space of Earth more and more under you, relative to your timestretched new environment in space you are now entering with your spaceship. You will see the Earth turning around more and more from your new point of view. If you escape gravity of the solar system, you will see the Earth and moon wobbling together and moving in the solar system around the sun more and more from your new perspectives. Because you have a new ‘idea’ of what ‘standing still’ means and a new idea of a flat space. And: the duration of your actual moment is the same for you, wherever you are. It is not stretched in your experience as an observer of time. Even if there is grafvitational timestretch when you leave the fields of gravity, you experience the same actual moment duration. Your actual moment is not stretched or dilated in the fields of gravity. So, you will see rotating and curved objects all around you further away from you. Your clock and your ruler are the standards for observing spaces further away from you. (f.e. intergalactic space). Why is your clock always ticking ‘normal’ in your experience, wherever you are, even near the vicinity of a black hole of near to the speed of light? Because to every observer, the duration of the actual moment is the same, wherever he is. The duration of the actual moment is the same, for every observer, wherever he of she is. Therefore: he will always measure ‘deformations of space’ elsewhere’. (expansions of spaces, curvatures of massive objects, rotations of massive curved objects, lengthcontraction, lengthstretch relative to him/her). Outthere, there is spacetime. A 4D geometry where past, present and future events exist simultaneously. (Einstein) But an observer exists only in the actual moment. That’s why he or she can only experience an unfolding of events, moment by moment. While in spacetime, all events exist simultaneously. Only living beings can exist in the actual moment. Objects are events existing simultaneously in spacetime in different moments in time. An observer always has a local idea of a straight line, that is not moving. (a reference frame for spaces and massive objects). You have your own clock, and your personal measurement of the timeflow, locally, is connected to your local idea of a straight line, that is not moving. Earth stands still, relative to you. Same clocks. Same timeflow. Locally, your idea of a eucledean space that is not moving is here on Earth. That’s an inertial frame of reference for an observer. In the world there are only these observers of time and space and no chosen coordinate systems. A reference frame randomly chosen by a mathematician is therefore something different from a physical observer with an actual moment experience who experiences the unfolding of the events moment by moment (and not simultaneously like in spacetime) in a 3D-world, with its own idea of standing still in unmoving straight spaces. The Observer cannot be found in material reality. The observer is a blind spot. A blind spot while measuring. It’s not measurable, but it is deducibly present, which is reduced to a zero point in mathematics Introducing a vague term such as ‘observation’ into science could meet resistance within physics because it falls outside the domain of what is considered ‘material or measurable reality’. But this difference in perspective makes a world of difference with regard to what kind of explanations you get for the observed phenomena, such as the observed expansion of space. (see timestamp model with ‘expanded space’ as relativistic space, depending on our experience of time) An observer always uses his own standards for space and time (his own frame of reference, as it is called) to measure a ‘length contraction’ or ‘time distortion’ elsewhere. Wherever he or she is. Genesis of this world? First there was spacetime. An invisible (pure non-material?) 4D geometry where all events exist or are accessible simultaneously. (people in near-death experiences talk about this timelessness experience and accessibility to all events simultaneously…). Then the first observer came into being and he or she experienced a 3D-world from his of her perspective with a particular clock (a local duration) and a particular ruler (a local particular idea of eucledean spaces that stands still, locally). Then he or she observed the curved and expanded spaces, rotating or not, elsewhere, with his or her clock and his or her ruler as the standard for these measurements. So, no Big Bang needed. Maarten Vergucht 24/12/2024 Antwerp, Belgium

This timescape model says exactly what I'm saying: the observed relativistic expansion is because of a relativistic timestretch. Not only the time on your clock is relative, but you also have a particular ruler... Your local ruler and your clock are the standard for measurements elsewhere.

I think my theory is been (partly) proven by scientists: Dark energy doesn't exist, according to new NZ study | University of Canterbury "the “timescape” model of cosmic expansion, which doesn’t have a need for dark energy because the differences in stretching light aren't the result of an accelerating universe but instead a result of how we calibrate time and distance. It takes into account that gravity slows time, so an ideal clock in empty space ticks faster than inside a galaxy."

Traveling at speeds close to the speed of light does introduce significant time dilation, meaning that while less time passes for the traveler, more time passes for those who remain behind on Earth. However, this doesn't necessarily mean it's only a one-way trip where "one just flies away and gone." While traveling at relativistic speeds, the astronaut's experienced time (proper time) is much shorter than the time elapsed on Earth. This means that a round trip is possible from the traveler's perspective within their own lifetime. Example Suppose an astronaut travels to a star 10 light-years away at a speed close to c.For the astronaut, due to length contraction and time dilation, the journey might take only a few years each way. However, from Earth's frame of reference, decades might have passed. :The traveler can return to Earth, but they would find that much more time has passed on Earth than they have experienced. and family may have aged significantly or passed away, and society could have changed drastically. Not Just "Gone": The traveler isn't lost or unable to return; they can physically come back. The key issue is the asymmetry in experienced time between the traveler and those on Earth. Practical Considerations: Relativity of Simultaneity: Events that are simultaneous in one frame of reference are not necessarily simultaneous in another moving at a high relative speed.This affects synchronization of time between Earth and the spacecraft. Communication Delays: Even at light speed, messages would take years to travel between distant points, complicating real-time communication. Conclusion: Not Necessarily One-Way: While the social and personal implications are significant due to time dilation, the journey isn't strictly one-way.The traveler has the ability to return, but must be prepared for the changes that have occurred during their absence. Future Possibilities: Advances in technology and understanding of physics might offer solutions to mitigate these issues, such as:Cryogenic Sleep: Extending the life of travelers to better align with Earth's time frame. Warp Drives or Wormholes: Hypothetical methods that could allow for faster-than-light travel without violating relativity. Summary: Traveling at relativistic speeds allows for round trips within the traveler's lifetime, but significant time will have passed on Earth due to time dilation. While this presents emotional and social challenges, it's not accurate to say the traveler is simply "gone." The possibility of return exists, but it comes with the understanding that the world they return to may be vastly different from the one they left.

It is true that accelerating an object with mass to the exact speed of light c would require infinite energy, and that this is physically impossible. However, it is not necessary to reach the speed of light to experience significant relativistic effects such as length contraction and time dilation. Length Contraction: The distance to your destination becomes significantly shorter in your own frame of reference. This makes it possible to bridge enormous cosmic distances within a human lifetime without needing to reach the speed of light. Energy Requirements: While it is true that the energy needed to get closer to the speed of light increases exponentially, this energy remains finite as long as the velocity is below c. The energy E required for acceleration is given by: E = (γ - 1) * m * c^2 where: m is the rest mass of the spacecraft. γ (gamma) is the Lorentz factor, defined as: γ = 1 / √(1 - v² / c²) Although E becomes large at high γ, it is not infinite as long as v < c . Practical Approach: Constant Acceleration: If we maintain a constant acceleration of, for example, 1g (9.81 m/s²), we can reach very high speeds within a reasonable proper time without overburdening the human body. Travel Time to Nearby Stars: To Alpha Centauri (4.37 light-years away): The travel time in proper time (your experienced time) would be only a few years with constant acceleration and deceleration. Technological Advancements: Although our current technology does not yet allow for this, it is theoretically possible that future technologies could provide the necessary energy—through means such as antimatter propulsion, nuclear fusion, or other advanced methods. Conclusion: Theoretical Possibility: According to the theory of special relativity, it is possible to traverse enormous distances in the universe within a finite and practical time span in your own frame of reference, without requiring infinite energy. Practical Challenges: While there are significant technological and energy challenges remaining, this does not exclude the possibility that such journeys could become feasible in the future. In summary, while it is physically impossible to reach the speed of light due to the infinite energy that would be required, it is not necessary to reach c to benefit from the relativistic effects that make interstellar travel within a human lifetime possible. By traveling at speeds close to, but below the speed of light, we can theoretically bridge any distance in the universe thanks to length contraction and time dilation, without the need for infinite energy.

According to Einstein's theory of special relativity, when traveling at speeds close to the speed of light, you experience a significant shortening of distances in the direction of your motion. This phenomenon is known as length contraction. This means that any distance in the universe is reachable as long as we can travel close enough to the speed of light, because as v approaches c, γ\gamma becomes very large, and thus L becomes very small. For an observer who is stationary relative to your motion (an "outsider"), your clock seems to run slower; this is called time dilation. But from your own perspective inside the spaceship, time proceeds normally, and it is the distance to your destination that becomes shorter. This can be expressed using the following formulas from special relativity: L = L₀ / γ Where: Lo is the rest length (the length measured in the reference frame where the object is at rest), γ\gamma (gamma) is the Lorentz factor, defined as: γ = 1 / √(1 - v² / c²) v is the speed of the moving object, c is the speed of light. Time Dilation The dilated time Δt measured by the stationary observer is given by: Δt = γ * Δt₀ Where: Δt₀ is the proper time (the time measured in the reference frame of the moving observer). Explanation For you in the spaceship: The distance to your destination L is smaller than the rest distance L₀ due to length contraction. Time passes normally for you; you don't notice any difference in the flow of time in your own reference frame. For the outsider: Your clock seems to tick slower due to time dilation. The distance between the starting point and the destination remains L₀. There is no length contraction in their reference frame. These effects become significant at speeds that are a substantial fraction of the speed of light. They result from the way space and time are interwoven in the theory of relativity. Conclusion Any distance becomes reachable once you travel close to the speed of light.

Think about it: the brain is nothing different than electricity flowing through wires. The brain is an electricity-producing machine. That's what we are. And electricity flowing through wires produces magnetism. And maybe, magnetism = consciousness.

The brain is nothing more than an electronic device. So, every electronic device with a lot of interconnected wires should be conscious too while switched on. We can use a bunch of steel wool and run electricity through it and we should have recreated a small artificial brain. The question is: how do you ask questions to it.

Time is relative, depending on the opinion of an observer. An observer who went a few times in the neighborhood of a black hole and returned back to Earth has another idea of the age of Earth and the decay rate of these radioisotopes, than an observer who stayed on Earth. Time is relative. No absolute property of the universe in itself. Since Einstein there is no universe with absolute time properties (and absolute space properties).

Is yesterday still here? Does the past exist? Is the future already here? Does the future exist? No, there is only the 'now'. And what is the duration of 'the now'? The 'now' cannot have any duration because otherwise it would have a past and a future, which is not 'the now'. So the duration of the now must be zero. No past, no now (zero) and no future = no time. So time does not exist.

What follows is what I believe to be a simple logical mathematical reasoning that explains why time cannot exist in the 'outside world', but that the experience of time is a property of a consciousness interacting with this 'timeless' outside world. The assumption is that if duration actually existed 'out there', you would have to go back infinitely to get to the beginning. Possibly involving multiverses and so on. You would have an infinite past. Because even if there was nothing in the universe, there would still be a duration. That is my assumption. When you do x "minus infinity", you have the idea that you have moved x infinitely downward, towards an infinitely negative value. To return to x by adding numbers, you would theoretically need to add an infinite amount. With respect to time, this would mean that; When you go back to minus infinity in time and then let time pass to the now, it would take an infinitely long time to reach the now. In other words: the 'now' could never be reached. Because it would take an infinitely long time to reach the now from an infinitely distant past. Therefore, duration cannot be something of the reality 'out there', but duration is something that we experience or measure as a result of the interaction of a consciousness with the reality outside that in itself does not know a sequential order of events in time, as we experience it. As Immanuel Kant formulated it: the passage of time belongs to the phenomena not to the noumena.

The comoving observer. Ok, thanks.

Give me some time. I will try to study first GTR better. Later I will answer when I understand it better.

Psychedelics show that brain activity reduces, the more intense the psychedelic experience. See the research of Robin Carhart Harris of Imperial College London of the brain on psilocybin. (magic mushrooms). see here: Neural correlates of the psychedelic state as determined by fMRI studies with psilocybin | PNAS The remarkable effect was: the more intense the experience, the less brain activity was seen. A negative correlation between consciousness and the amount of brain activity. This, and many other phenomena, confirm the 'filter theory' of consciousness, where at a certain point, we get access to Mind at Large or 'the block universe' or 'the universe as a whole'. This is the unity experience of mystics where there is no time. This correlates with a bad working brain, with no or less oxygen indeed. The more damaged the brain is, the more people experience Mind at Large and 'all events simultaneously'. This is a hypothesis, but this 'no time experience is another piece of the puzzle to see that time is an illusion of a mind connected to a body. Or to an observer in time and space.

Imagine a world without observers. Even you, observing your own body in time are not attached to this body anymore. Everything exists simultaneously (Einstein) in the block universe. We know from NDE-ers who ar not attached to their body anymore that they can confirm that they experience 'everything at once'. They experience no time. A place where everything is accessible in the present. There is no time. Many observers who are not attached to their bodies during a near-death experience can confirm this. They experience the block universe as it is in itself, without them observing it attached to a body in time and space.

In my opinion, what's common in general relativity theory and quantum theory = observers. Einstein talked about observers and in quantum theory 'the observer effect' plays a role. So, to unite both theories, we have to look at the world with observers versus the world without observers. In my opinion: in quantum theory 'everything is in superposition' when there are no observers. In relativity in the block universe: everything happens simultaneously when there are no observers. I think that the difference between a world with observers versus a world without observers is a world where events happen sequentially versus a world where everything happens simultaneously. When the scientist (and all other observers) isn't there, all the steps to execute the experiment are all together existing in spacetime simultaneously. When there is a scientist, this is been observed as sequential order of events through time.

My point is that you can not make statements about the duration since the socalled big bang (the age of the universe), because different observers will disagree on this idea. And even if the differences are small, the fact that there is a difference makes a big difference for in what kind of universe we live. A universe with a relative time where there can be no statements about age or time or a universe with absolute time or space.

But if you now travel close to a black hole for a few months and return to Earth, your perception of the elapsed time since the Big Bang will differ from that of other observers. Thus, your method of reckoning time violates the principle of relativity of time in my opinion.

Indeed: we measure with our clock. You say: 'Most clocks in galaxies run at about the same rate unless you're near a black hole or moving at a significant fraction of c'. The distinction between a universe where time, or age, is relative, and one where the universe's age can be precisely defined, is critical. Even minor discrepancies in time measurements suggest significant differences in our understanding of the universe: one with a definite age versus one without a measurable timescale.

I follow simple logical deduction from true premises: True premise: Space and time are no longer absolute as in the time of Newton. They are relative, since Einstein. Valid logical conclusion: There is no preferred reference frame for space. Supporting (thought) experiments: Observers can be conceived who measure a different space. (a photon, a hypothetical observer close to the speed of light approaching Proxima Centauri). Valid conclusion: Every observation of space is relative. THUS ALSO the observation of expanding space, as an interpretation of the observation of the Doppler effect of light emitted from distant galaxies, by 'expansion of space' moving away from us. True premises, logical reasoning, valid conclusion. And there is not only no preferred reference frame for space where every observation of space is relative, so also the observation of expanding space. There is also no preferred reference frame for time. Therefore, (elapsed) time since the so-called Big Bang is also relative. Different observers with their own clocks will measure a different duration since the Big Bang. So, the so-called age of the universe depends on which clock? Which preference do you give to which reference frame for (elapsed) time since the so-called Big Bang?