A reference frame is a particular coordinate system chosen to represent physical entities. The notion is most often used in special and general relativity to dentoe particular coordinates chosen on the spacetime manifold.

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In relativity theory could we talk energy rather than frames of reference? [on hold]

In relativity theory, the space geometry, of space and time, is no longer absolute, if one observer is accelerating compared to the other. Could I say in other words that space geometry is changed if,...
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104 views

Does the factor $k$ in Hooke's law change in special relativity? [on hold]

let's say an object is tied to a spring and it's oscillating. But this system is moving in 0.5c. Then, the period of this oscillation increases. But the problem is $k$. I think the $k$ increases ...
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32 views

Rolling Coin (Old Physics Quals Exam) derivation help [duplicate]

I am trying to understand the derivation for the angular velocity of a rolling coin in the problem given on this website: http://functionspace.com/question/27/answer/121 How does one find angular ...
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1answer
20 views

Is the motion of rotation perfectly symmetrical? [duplicate]

Scientifically, can we say that one of these assertions is more "correct" than the other? (philosophically we can say that the first one is more correct because it makes the motion of other planets "...
2
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89 views

Foucault pendulum, where did I go wrong?

I wanted to approximate the number $N$ of periodes needed, such that the foucault pendelum turns one time. Though my result is off by the factor 2 of the results I found. What I did: I assume the ...
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3answers
66 views

How high do you need to be so as to not rotate along with Earth?

So, I saw this meme about some minister commenting that the Earth doesn't rotate, for if it did then planes only need to be in the air and the destination city would come to it. I know this is absurd ...
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53 views

Can an object take off from A, do not move (in the air) but land at a different place? [closed]

Can an object take off at a point A on the surface of the Earth and then land after some time only to land at a different place where it initially took off (because in the mean time the Earth has ...
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56 views

How can I slow down? Or, How can I speed up time? Reverse twin paradox

Everyone know the standard Twin Paradox. I have my clock synchronized here on Earth with my twin. I leave Earth, Travel for a time at 0.9c, turn around, come back at .9c and then my clock is slow ...
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38 views

Total Linear Momentum Conserved for Earth-Sun System? [closed]

According to 'Introductory Astronomy and Astrophysics' by Smith and Jacobs the total linear momentum of an isolated system is constant which they choose as zero, so they get (mv)1 = (mv)2. When I ...
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41 views

Frames of reference vs Coordinate systems and the meaning of “inertial” [closed]

Wikipedia provides the following definition for inertial frames:(the reference given is to Landau's Mechanics book) In physics, an inertial frame of reference (also inertial reference frame or ...
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59 views

Synchronization of clocks using material waves

I am not a physicist by training, but I have studied special relativity enough to understand why simultaneity is a relative concept, and so why if you synchronize clocks in one inertial frame, an ...
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17 views

The “force” of gravity is an illusion: things follow geodesics in space-time warped by mass-energy - can other forces be explained by similar models? [duplicate]

As I understand it, the force of gravity between two objects is not really a force, but appears to be so. It behaves in such a way that the Newtonian force explanation works in many cases, but the ...
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3answers
38 views

Momentum and relative motion

To calculate momentum, $p=mv$, you must know the value of $v$. However, since all motion is relative, there is no abslute value for $v$. So, what is it you are actually calculating? It seems like the ...
2
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0answers
93 views

Determination of Euler angles from known angles between the axes of two coordinate systems

Suppose there is a unprimed coordinate system XYZ, tilted w.r.t. a primed coordinate system but their origins coincide. Let the angle between $X,X^\prime$, $Y,Y^\prime$ and $Z,Z^\prime$ are ...
9
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5answers
806 views

With respect to what can't we travel at the speed of light? [closed]

According to theory of relativity the speed of light in vacuum is ultimate. But since objects move relative to each other, with respect to what can't we travel at the speed of light?
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5answers
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What does the Moon's orbit around the Sun look like?

I'm curious as to what the Moon's orbit around the Sun looks like. If there's an answer, what's the intuition for it? Here are some things I'm assuming when trying to tackle this question: The Moon'...
5
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80 views

What is the resolution of this Lewis-Tolman like paradox?

Though my question stands on its own, here is a brief overview of a well-explored question which I think might be helpful in finding the resolution to my question. The Lewis-Tolman Lever Paradox has ...
2
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1answer
35 views

How to determine my position using Coriolis effect?

The Coriolis effect is the effect that causes wind and water and moving objects to curve clockwise in the northen hemisphere and anticlockwise in the southern hemisphere, so how to determine my ...
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2answers
42 views

Reference frame for the Cosmic Neutrino Background

It is well known that there exists a reference frame where the total momentum of the Cosmic Microwave Background is zero (a basic fact of special relativity applied to a collection of massless ...
5
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1answer
141 views

What is the difference between active and passive transformations in Quantum Mechanics?

I am trying to understand what each transformation means and what their differences are but many books that don't state which transformation they are referring to make it a bit confusing to understand ...
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1answer
50 views

Confirmation of a concept under General Relativity and Frames of Reference

I would like to preface this by saying that this isn't necessarily meant to be a full question, though it may become that, but it rather a confirmation of my understanding of a concept. Newton would ...
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79 views

What happens if you fly a drone inside moving passenger airplane? [duplicate]

I have a little question. If I mark an X in the center of a passenger airplane, and try to fly a drone from the X mark in the moving passenger airplane (800-900 km/h), what will happen to the drone? ...
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22 views

Is mass relative? [duplicate]

This question has to do with the relativistic mass of an object. I have been reading that as energy increases, so does mass to a much lesser extent, and that this applies to kinetic energy as well. ...
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2answers
99 views

Why do Newton's laws hold in a normal and tangential coordinate system?

In my book it says: When applying the equations of motions, it is important that the acceleration of a particle be measured with respect to a reference frame that is either fixed or translates ...
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82 views

Imagine I'm on a spacecraft that was accelerated to 1.0$c$ could I only move backwards? [duplicate]

Imagine I'm in a sapcecraft1 that is moving with 1.0$c$ or at least is so close to that speed that a few miles per hour would just be left to reach $c$. So when I'm traveling now in the direction ...
3
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3answers
107 views

Why must $v$ be $< c$ in the Lorentz transformations? Do these equations not apply to light? [duplicate]

I was trying to understand how things look from the perspective of light. Looking at the Lorentz transformations, it seems that the universe would contract along the direction of movement into a plane,...
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2answers
119 views

All reference frame are inertial? Where is the flaw in reasoning?

This is my first post here. I have a line of thoughts which might be wrong but I couldn't find the error. Suppose we have a point mass subjected to an arbitrary force $F$. In the lab reference frame ...
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1answer
81 views

Why cannot Paul be the observer? (Questions about Twin Paradox)

Here is the explanation to the Twin Paradox in Feynman's Lecture on Physics 16–2. we consider a famous so-called “paradox” of Peter and Paul, who are supposed to be twins, born at the same time. ...
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126 views

Special Relativity - oscillator paradox

I am reading about the Special relativity and the original Einstein papers from 1905 and 1920 where he derives the Lorentz transformation and the effects of the time dilation and space contraction ...
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1answer
45 views

Symmetry, Space-Time interval, and Coordinate Time

I had the following question I was working from a book: Question: A physics professor runs across the hallway covering 120 ns of distance in 150 ns of time as measured in the frame of the earth....
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2answers
78 views

Frame of reference in elevator

I have a conceptual question that I have trouble understanding. An object at the end of a rope is attached to the ceiling of an elevator. If the elevator is allowed to free-fall and hit the ground, ...
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3answers
98 views

Why does the period of a pendulum decrease in an accelerating frame? [duplicate]

If there is a simple pendulum in a non-accelerating frame with period $T_1$, it will have period $T_2 < T_1$ when placed in a frame accelerating perpendicularly to the direction of gravity. Why?
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44 views

Notations used to express direction [closed]

We express direction relative to a reference point and call a certain direction positive and it's direct opposite direction negative, by convention. But, what notation should we use to express a ...
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58 views

Lagrangian of an effective potential

If there is a system, described by an Lagrangian $\mathcal{L}$ of the form $$\mathcal{L} = T-V = \frac{m}{2}\left(\dot{r}^2+r^2\dot{\phi}^2\right) + \frac{k}{r},\tag{1}$$ where $T$ is the kinetic ...
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1answer
131 views

Is conservation of momentum and energy valid for non-inertial frames?

Conservation laws of momentum and energy are said to be the most basic principles of physics. Are they also valid for non-inertial frames, and in what way?
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55 views

Locally remove a gravitational field

Let $K$ be an inertial frame of reference on $\mathbb{R}^3$ and $g=g(t,x)$ a nonuniform and nonstatic gravitational field. How I can choose a system of reference $\bar K$ such that mechanical effects ...
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63 views

Speed and motion

If you your traveling in a forward motion at a certain speed and throw an object in the opposite direction at the same speed shouldn't it fall straight down to the ground.
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4answers
110 views

Does the $t = 0$ hypersurface of simultaneity constitutes the universal present?

Does the hypersurface of simultaneity in the diagram below represent the universal present moment? Source: Einstein for Everyone - Spacetime
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100 views

What is meant by rest in rest-mass?

As far as I know only photons are considered to have no rest-mass. In common words when it doesn't move it 'disappears'. Electrons and quarks should have a rest-mass. But are they really at rest? ...
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111 views

Is the speed of light constant in all directions?

Consider the shape of the waveform emitted by a moving source: (with the horizontal axis "x" and the vertical axis "y"). According to the stationary observer, the wavefront of a short pulse ...
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1answer
20 views

Heliocentric to barycentric coordinates

I have a system with a central body and "particles" orbiting around it. The system is described in heliocentric coordinates. I am trying to obtain the velocity of the central body in barycentric ...
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39 views

A photon lives life as a flat-lander? [duplicate]

Think length contraction... I was thinking about going close to the speed of light the other day, and I was thinking about the idea that, if you went close to the speed of light, time would slow down ...
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2answers
58 views

Rotating Frames of Reference: Doubt while deriving the velocity

I am following an online Chapter on Coriolis force, where the author develops the equations for a rotating frame of reference. The Figure and most of the notation used in the derivation can be ...
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2answers
96 views

Can't reach speed of light, but relative to who?

Imagine a stationary person (with respect to a spaceship) floating in space and looks at a clock on the spaceship going 0.5c and sees it's clock ticking slower than his own, and concludes that it is ...
0
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1answer
46 views

How to measure time in presence of a strong gravitational field? [duplicate]

I need an operative definition of "measuring time in general relativity" that takes in consideration also the presence of strong gravitational fields between me and clock, able to deviate the light ...
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1answer
72 views

“Measure of time in general relativity” [duplicate]

Suppose to be in an arbitrary gravitational field and you are moving in it arbitrarily with a clock in your hand. In this general situation I ask: if I read the positions of the hands of the clock, ...
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2answers
53 views

Difference between space of reference and system of coordinates

In the book "The meaning of the relativity" by A. Einstein, it is referring to two different concepts: space of reference and system of coordinates. What it is the difference? It says: "we ...
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1answer
94 views

How much Gravity is required to stop time?

Clocks free of gravitational influence run faster than those experiencing gravity. Is it possible for gravitational influence to bring time to a stop? Additionally can acceleration affect clocks in ...
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77 views

Why does the centrifugal term involve a vector originating from the center of Earth? [closed]

Why in every mechanics/dynamics book I look the centrifugal force due to Earth's rotation is measured from "the center of Earth"? For example in Marion's dynamics, the fixed inertial axes are placed ...
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2answers
69 views

Is there a way to make atom move faster without heating them?

The more heat you add the faster the atom will move. This is something that is common knowledge. My question is it possible to make the atoms in let's say a gas move faster without adding heat of a ...