Category Archives: Space & Time

Explorations of multidimensional space and time with linear and angular motion.

Basic definitions

May 21, 2019 2:52 pm ⋅ rag

Independent variable is a quantity that is not dependent on another quantity, which is either (a) a quantity chosen before an experiment or race, or (b) an ever-increasing quantity. Dependent variable is a quantity that whose value is a function of another variable.

Space is (1) length; (2) a 3D differentiable manifold of length; (3) the order of events on a stance line; (4) the stance, the reading on an arcloge.

Time is (1) duration; (2) a 3D differentiable manifold of duration; (3) the order of events on a time line; (4) the time, the reading on a clock.

Length is measured by a rigid rod. 3D space is length measured in three directions of motion.

Duration is measured by a stopwatch, timer, or clock. 3D time is duration measured in three directions of motion.

Spacetime is the 6D manifold formed from 3D space and 3D time. Worldline is the path in spacetime traced out by an object in motion.

Displacement is the vector between two points (events) on a worldline. Distance is the magnitude of a displacement.

Dischronment is the vector between two points (events) on a worldline. Distime is the magnitude of a dischronment.

Reference frame (or frame) is an abstract coordinate system and set of reference points in 3D space that uniquely fix the coordinate system and standardize measurements. Rest frame of a body is the reference frame in which the body is moving at zero speed, which is the time conversion pace.

Reference timeframe (or timeframe) is an abstract coordinate system and set of reference points in 3D time that uniquely fix the coordinate system and standardize measurements. Freeflow frame of a body is the reference timeframe in which the body is moving at zero pace, which is the stance conversion speed.

Proper length is the length of a body measured by a rigid rod moving with it. Proper time is the time of a body measured by a clock moving with it.

Lorentz transformation is a set of equations that relate space and time coordinates of reference frames moving at a constant velocity relative to each other.

Dual Lorentz transformation is a set of equations that relate space and time coordinates of reference timeframes moving at a constant legerity relative to each other.

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time

From racing to relativity

May 20, 2019 1:17 pm ⋅ rag

There are three different contexts for 3D time, depending on whether stance is continuously increasing and, if so, whether there is a conversion factor between space and time:

(A) Stance is not continuously increasing. This is the situation of a race or sport in which game time has a definite beginning and ending. For example, in many sports the game lasts a specific time. In a race, the length of the course is set and the time for each contestant ends when they cross the finish line. The average pace of a contestant is their race time divided by the course length.

(B) Stance is continuously increasing and there is a general conversion factor between space and time. This is the situation of the special theory of relativity and some transportation settings in which the conversion pace is the minimum pace (and maximum speed).

In this case, there is an increasing stance whether or not a positive time interval is measured. Without a time interval increase the pace is at a minimum (or the speed is a maximum). As the amount of time measured increases, the pace increases (or the speed decreases). Remember that a small amount of time per unit distance is a fast motion, whereas a large amount of time per unit distance is a slow motion.

In this way, the pace increases indefinitely. A pace of infinity would be at rest. A pace of zero is the minimum pace, which in relativity is the speed of light. That is, the speed counts down from the speed of light. This has been misinterpreted as a transformation with superluminal speeds, but because speed decreases as pace increases, object speeds are subluminal.

The dual Lorentz transformation (see here) is

$x'=\lambda (x - ur);\; y'=y;\; z'=z;\; r'=\lambda (r - c^2ur) \; \textup{with}\; \lambda = 1/{\sqrt{1-cu}}$

with the understanding that c represents the inverse of the pace of light. The cu in λ is the pace of the object divided by the pace of light, with the stance increasing at the conversion rate. As the time of motion increases, the pace increases (and the speed decreases) from that of light toward the pace or speed of rest. So, the square root never becomes negative here.

(C) Stance is continuously increasing but there is no general conversion factor between space and time. This is the situation of general relativity and transportation in general. Conversion of space and time are local, not global, and the optimal route depends on whether space or time are optimized.

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time, transportation

Invariant intervals

May 8, 2019 11:01 am ⋅ rag

The spacetime interval is invariant over the Lorentz transformation (LT). The following is a proof of this for the inverse LT with spatial axes x, y, and, z; temporal axis t (time line), velocity v, and maximum velocity c, along with β = v/c and γ = 1/√(1 − β²):

$\Delta x=\gamma (\Delta x'+\beta c\Delta t');\; \Delta y=\Delta y'\; \Delta z=\Delta z';\; c\Delta t=\gamma (c\Delta t'+\beta \Delta x').$

The invariant interval is

$(\Delta s)^2 = (c\Delta t)^2 -(\Delta x)^2 -(\Delta y)^2 -(\Delta z)^2$

$=\gamma ^2(c\Delta t'+\beta\Delta x')^2 -\gamma ^2(\Delta x'+ \beta c\Delta t')^2 -\Delta y'^2 -\Delta z'^2$

Expand the squares and cancel the middle terms to get:

$=\gamma ^2(c^2 \Delta t'^2(1-\beta ^2) -\Delta x'^2(1-\beta ^2)) -\Delta y'^2 -\Delta z'^2$

$=\gamma ^2(c^2 \Delta t'^2(1/\gamma ^2) -\Delta x'^2(1/\gamma ^2)) -\Delta y'^2 -\Delta z'^2$

$=(c\Delta t')^2 -(\Delta x')^2 -(\Delta y')^2 -(\Delta z')^2.$

The spacetime interval is invariant over the dual Lorentz transformation (DLT). The following is a proof of this for the inverse DLT follows with temporal axes x, y, and, z; spatial axis r (stance line), legerity u, and maximum legerity κ, along with ζ = u/κ and λ = 1/√(1 − ζ²):

$\Delta x=\lambda (\Delta x'+ \zeta \kappa \Delta r');\; \Delta y=\Delta y'\; \Delta z=\Delta z';\; \kappa \Delta r=\lambda (\kappa \Delta r'+\zeta \Delta x').$

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time

Symmetric transformations

May 3, 2019 2:06 pm ⋅ rag

What follows are Lorentz and Ignatowski transformations and their duals with symmetric and vector forms for reference.

For the (3+1) Lorentz transformation there are spatial axes x, y, and, z; temporal axis t (time line), velocity v, and maximum velocity c, with β = v/c and γ = 1/√(1 − β²):

$x'=\gamma (x - vt);\; y'=y;\; z'=z;\; t'=\gamma (t - vx/c^2).$

The symmetric form is

$x'=\gamma (x -\beta ct);\; y'=y;\; z'=z;\; ct'=\gamma (ct - \beta x).$

The symmetric Lorentz transformation for vectors is

$\mathbf{r'}_\perp = \mathbf{r}_\perp;\; \mathbf{r_\parallel }'=\gamma (\mathbf{r_\parallel } - \boldsymbol{\beta } ct);\; ct'=\gamma (ct - \boldsymbol{\beta } \cdot \mathbf{v}),\; \textup{with } \boldsymbol{\beta } =\mathbf{r_\parallel }/c.$

For the (1+3) dual Lorentz transformation there are temporal axes x, y, and, z; spatial axis r (stance line), legerity u, and maximum legerity 1/c, with ζ = cu and λ = 1/√(1 − ζ²):

$x'=\lambda (x - ur);\; y'=y;\; z'=z;\; r'=\lambda (r - c^2ux).$

The dual symmetric form is

$x'=\lambda (x - ur);\; y'=y;\; z'=z;\; \frac{r'}{c^2}=\lambda (\frac{r}{c^2} - ux).$

The dual symmetric Lorentz transformation for vectors is

$\mathbf{t'}_\perp = \mathbf{t}_\perp;\; \mathbf{t_\parallel }'= \lambda (\mathbf{t_\parallel } - \boldsymbol{\zeta }\frac{r}{c});\; \frac{r'}{c}=\lambda (\frac{r}{c} - \boldsymbol{\zeta } \cdot \mathbf{u}),\; \textup{with } \boldsymbol{\zeta }=c \mathbf{t_\parallel }.$

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time

Ignatowsky relativity

April 27, 2019 2:05 pm ⋅ rag

Vladimir Ignatowski (1875-1942) was a Russian physicist. “In 1910 he was to first who tried to derive the Lorentz transformation by group theory only using the relativity principle (postulate), and without the postulate of the constancy of the speed of light.” K M Browne gave a simplified derivation in the European Journal of Physics, 39 (2018) 025601, from which the key steps are presented below, followed by the corresponding steps for a dual transformation, switching space and time.

This is a derivation of the Ignatowsky transformation in which the axes x, y, and z are taken to represent space axes r_x, r_y, and r_z with time t. The relativity postulate is taken to be: a valid relativistic transformation must be identical in all inertial frames.

Step 1. To find a valid transformation, we take the usual inertial reference frames S and S′ (the latter moving at velocity v in the +x direction relative to the former) for which intra-frame space is Euclidean but inter-frame space (measured from one frame to the other) may be non-Euclidean. Linear equations are necessary so that an event in one frame appears as a single event, without echoes, in the other. Initial conditions are x′ = x = 0 when time t′ = t = 0. We expect the generalised x equation to be the Euclidean equation x′ = x − vt with an added multiplier, and if time is the fourth dimension, then the time equation will be similar but with two additional multipliers. The second of these, n, having the dimension of inverse velocity squared, is required to make the equation dimensionally correct. The y and z coordinates are not expected to be affected by x and t. The generalised transformation and its inverse are then

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time

Length contraction and time dilation

April 9, 2019 11:03 am ⋅ rag

These derivations follow that in ‘Hyperphysics’ here.

Length Contraction

The length of any object in a moving frame will appear foreshortened in the direction of motion, or contracted. The length is maximum in the frame in which the object is at rest.

If the length L₀ = x₂´ − x₁´ is measured in the moving reference frame, then L = x₂ − x₁ in the rest frame can be calculated using the Lorentz transformation.

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time

Length and duration in space and time

April 8, 2019 7:56 pm ⋅ rag

The following derivations are based on the exposition by G. G. Lombardi here.

Time Dilation

A clock is made by sending a pulse of light toward a mirror at a distance L and back to a receiver. Each “tick” is a round-trip to the mirror and back. The clock is shown at rest in the “Lab” frame in Fig. 1a, or any time it is in its own rest frame. Consequently, it also represents the clock at rest in Rocket #1. Figure 1b is the way the clock looks in the Lab when the clock is at rest in Rocket #1, which is moving to the right with velocity v and legerity u, hence speed v and pace u.

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time

Linear clocks and time frames

April 2, 2019 2:37 pm ⋅ rag

The idea of a linear clock was mentioned before here, here, and here.

Consider two bars or rods, one on top of the other (left), each with a zero point aligned at first. The top one moves at a constant rate relative to the other, which is at rest. After a time T, the top bar has moved an interval measured by the difference between the zero points of the bars (right). The length that B moved relative to A measures the time of motion.

Side note: a 12-inch ruler turned into a circle would form the markings for a 12-hour clock. The hours of time would correspond to inches of length.

A time frame of reference (TFR), or time frame, is a frame of reference for time. Like a space frame of reference (SFR) it is composed of rigid bars or rods that can in principle be extended indefinitely.

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time

Observers in motion

March 18, 2019 6:30 pm ⋅ rag

A rigid rod or other device that measures length is at rest relative to itself, even if part moves such as a measuring wheel, because it moves relative to other objects, not relative to itself. A concept of simulstanceity enables an observer to determine length at other times (e.g., they are the same point on the stance line).

A clock measures time, but what is a clock? It is a device with a part that moves relative to a part that is at rest. So a clock is an object in motion relative to itself (yes, this is possible). The part that moves indicates the time. A concept of simultaneity enables an observer to determine time at other places (e.g., they are the same instant on the time line).

Let there be a rigid reference frame associated with each observer or object (e.g., they are attached). An observer may be at rest or in motion relative to their frame. If the observer is at rest, then their frame is a length frame and what they observe is in space. Time is the independent variable and length in three dimensions is the dependent vector variable.

If the observer is going somewhere, they are not at rest but in motion. Their reference frame for rest is not their own frame but a different frame, such as one located on the surface of the earth. In this case the observer and rest frame system are like a clock, that is, a clock frame, and what is observed is in time. A clock frame is moving in the opposite direction of a rest frame. Length is the independent variable and time in three dimensions is the dependent vector variable.

For Galilean inertial frames the observer is at rest and the moving frame transmits the current stance in an instant of the time line, instantaneously. For dual Galilean inertial frames the observer is in motion and the rest frame transmits the current time in a point of the stance line, punctstanceously.

The rest frame observer has three dimensions in space. The observed frame in motion is effectively reduced to the one dimension of its motion in time. The moving frame observer is like a clock with space and time exchanged: the dimensions of the observer’s frame are in motion so the three dimensions are in time. The rest frame that is observed appears to move and is effectively reduced to the one dimension of its path in space.

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time, transportation

Time and simultaneity

March 7, 2019 2:55 pm ⋅ rag

There are several ways of understanding the time of remote events. What follows is a summary of the basic ways of determining simultaneity.

As a way of comparing the different ways consider transmitting a light signal to a remote location where it is reflected back. What is the time when the signal is reflected back?

Observation time is an extension of ordinary perception. When we observe an event, we say that it is happening at the time of observation. So when a light signal is reflected and received back, the reflection observed is considered to have happened when it was observed. In effect the light observed is instantaneous. By implication the one-way speed of light transmitted is c/2 in order for the two-way speed of light to equal c.

Observation time is thus the projection of the time of observation to the entire observable universe. This way of understanding time is characterized by the Galilean transformation.

Transmission time is an extension of the ordinary transmission of light. When we shine a light on an event, we say that it is happening at the time of transmission. So when a light signal is aimed toward a reflector, the event of reflection is considered to have happened when the light was transmitted. In effect the light transmitted is instantaneous. By implication the observed one-way speed of light is c/2 in order for the two-way speed of light to equal c.

Transmission time is thus the projection of the time of transmission to the entire transmittable universe. This way of understanding time is characterized by the dual Galilean transformation.

Probe time is an extension of measurement by a probe (a “small, unmanned exploratory craft”) to the entire probeable universe. See previous post here. An event is said to occur when intersected by a probe that measures the duration of probe movement since a reference event. So when a probe comes upon the reflection of light, the probe measures the time of reflection as the time of the probe. If the probe is not moving at the speed of light, there may need to be multiple probes.

Consider a series of probes moving at a speed v over a distance d to the reflection event. The probe that leaves at time (d/c) – (d/v) is the probe that intersects the reflection event. If v = c, then the time is zero.

Because probes can measure the length or duration of motion, probe time is characterized by the Lorentz or dual Lorentz transformation.

Reference frame time measures time by a rigid reference frame that has clocks which were previously synchronized spread throughout. See the Relativity of Simultaneity and Einstein Synchronisation. These synchronizations are characterized by the Lorentz transformation.

Posted in: Knowing, space & time ⋅ Tagged: physics, space & time

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Category Archives: Space & Time

Basic definitions

From racing to relativity

Invariant intervals

Symmetric transformations

Ignatowsky relativity

Length contraction and time dilation

Length and duration in space and time

Linear clocks and time frames

Observers in motion

Time and simultaneity

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