# What is Galilean: Definition and 154 Discussions

Generically, a Galilean (; Hebrew: גלילי‎; Ancient Greek: Γαλιλαίων; Latin: Galilaeos) is an inhabitant of Galilee, a region of Israel surrounding the Sea of Galilee (Kinneret). The New Testament notes that the Apostle Peter's accent gave him away as a Galilean (Matthew 26:73 and Mark 14:70). The Galilean dialect referred to in the New Testament was a form of Jewish Palestinian Aramaic spoken by people in Galilee from the late Second Temple period (530 BCE) through the Apostolic Age (c. 100 CE). Later the term was used to refer to the early Christians by Roman emperors Julian and Marcus Aurelius, among others.

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1. ### I Fuel paradox arising from Galilean transformation?

I have encountered a problem related to the Galilean Transformation. Let's consider two observers who will be referred to as ##O## and ##O^{'}##, with their corresponding coordinates ##(t,x,y,z)## and ##(t^{′},x^{′},y^{′},z^{'})## respectively. They are initially at the same location, at time...
2. ### I The Hamiltonian and Galilean transformations

In a classical example, for a system consisting of a mass attached to a spring mounted on a massless carriage which moves with uniform velocity U, as in the image below, the Hamiltonian, using coordinate q, has two terms with U in it. But if we use coordinate Q, ##Q=q−Ut##, which moves with the...
3. ### A Ballentine on construction of the (Galilean) symmetry generators

In Problem 3.7, Ballentine says: The unitary operator ##U(v) = exp(iv·G)## describes the instantaneous ##(t = 0)## effect of a transformation to a frame of reference moving at the velocity ##v## with respect to the original reference frame. Its effects on the velocity and position operators are...
4. ### I Can time be another basis vector under Galilean relativity?

I refer to the video of this page, where there is a description of Galilean relativity that is meant to be an introduction to SR, making the comprehension of the latter easier as a smooth evolution from the former. All the series is in my opinion excellent, but I think that this aspect is...
5. ### Does the Galilean transform rely on 2 events?

From my limited understanding the Galilean transform has 2 frames but 4 four perspectives. For example x is the stationary frame when using ## ∆x = ∆x′ + v ∆t ## and x' is moving. When using ## ∆x' = ∆x - v ∆t ## and x' is stationary and x is moving. Now lets use the example of ## ∆x = ∆x′ + v...
6. ### I Follow Up on M. LeBellac & J.M. Levy-Leblond's "Galilean Electromagnetism

In https://www.physicsforums.com/threads/what-assumptions-underly-the-lorentz-transformation.1015982/post-6657920 a discussion evolved from the basic assumptions of the Lorentz transformations, to a paper M. LeBellac, J. M. Levy-Leblond, Galilean electromagnetism, Nuovo Cim. 14B, 217 (1973)...
7. ### Galilean transform and Lorentz transform questions

I have a quick question about the Galilean transform. If I have Alice running and Bob stationary. The Galilean transform will tell me the position of Alice from Bob's stationary position. Also if I have Alice's position which is moving it will tell me Bob's stationary position. If I want Bob...
8. ### B Galilean vs Lorentz Transformations: Correct Understanding?

In the frame of Observer C standing by the side of the road, the speed of Car A with respect to Car B = v1 + v2. (Galilean Transformation). In the frame of Car A, the speed of Car B < v1 + v2 (Lorentz Transformation). Please tell me if this understanding is correct.
9. ### I Galilean transformation of non-inertial frame

It's frequently discussed Galilean transformation brings one inertial frame to another inertial frame, and such a transformation leaves Newton's second law invariant (of the same form). I wonder what happens for non-inertial frame? If we start with a non-inertial frame, and Galilean transform...
10. ### I Proving Galilean Transformation for Inertial Frames

I know we can prove that a Galilean transformation sends one inertial frame to another inertial frame, by proving ##\frac{d^2 f(\vec{r})}{d(f(t))^2} = \frac{d^2 \vec{r}}{dt^2}##, but can we prove the reverse? Can we prove that if the acceleration seen in two frames are the same, then the...
11. E

### B Understanding the Galilean transformation

I got a bit confused, and hoped someone could clarify a few things. As far as I am aware, a change of basis is an identity transformation ##I_V## on the vector space (pg. 113) and we can write the relationship between the components of some vector ##v## in the different bases ##\beta## and...
12. ### Transformation law of momentum under Galilean transformation

I'm reading the article https://www.researchgate.net/publication/267938119_ON_THE_GALILEAN_COVARIANCE_OF_CLASSICAL_MECHANICS (pdf link here), in which the authors want to establish the transformation rule for momentum, assuming only that ##\vec{F}=d\vec{p}/dt## and notwithstanding the relation...
13. ### Covariance of Newton's 2nd Law under Galilean boosts

I'm reading a section in a textbook on the explanation of covariance of Newton's 2nd law under Galilean boosts. It's explained that ##\mathbf{a}=\mathbf{a'}## (where we're considering two frames ##S## and ##S'## moving inertially w.r.t. each other). Mass is assumed to not vary across the frames...
14. ### Does Galilean relativity imply infinite propagation speed?

Without assuming a universal speed that is constant in all inertial reference frames, is it a necessary consequence of Galilean symmetry that interactions are instantaneous? If this is the case how can we prove this?
15. ### I Does Galilean symmetry imply that all systems are monogenic?

The equations of motions for a closed system consisting of ##N## particles are: $$m_i \vec x_i'' = \sum_{j \neq i}^N \vec F(\vec x_i, \vec x_i', \vec x_j, \vec x_j')$$ $$i = 1,..., N$$ Now if we impose the requirement that this closed system be symmetric under Galilean transformations, do we...
16. ### I Galilean spacetime as a fiber bundle

Hi, reading the book "The Road to Reality" by Roger Penrose I was a bit confused about the notion of Galilean spacetime as fiber bundle (section 17.2). As explained there, each fiber over absolute time ##t## is a copy of ##\mathbf E^3## (an instance of it over each ##t##), there exist no...
17. ### Question about the Galilean transform in classical physics

Shouldn't the equation be x' = x + (v')(t) instead of x' = x + (v)(t)?
18. ### I Explanation of Galilean transformations

Hi everyone, We've just started special relativity and I'm just wondering if you'd mind clarifying something for me. The transformation is described as x'=x-vt, where x' is moving relative to x. However, in the diagram I've attached, x' is ahead of x ; so why is the transformation described...
19. ### I Lorentz Boost & Galileo Speed: Exploring Relationship

What about if the speed parameter in a Lorentz boost were in fact related nontrivially to a Galilean speed ? More formally ##L(v_L)=G(v)\circ F## where L is a Lorentz boost with Lorentz speed ##v_L##, G is a Galileo transformation with speed ##v## and ##F## is still an unknown linear...
20. ### Classical Book suggestions on Galilean Transformations

Hi, I'm looking for books with a really good explanation on Galilean Transformations. I find the books and/or sections where only the theory of how to convert from one to another inertial system is mentioned, but nothing with concrete examples and additional exercises. Any suggestions are...
21. ### B Energy as a non relativistic scalar and Galilean invariance

Summary: Why is there no contradiction between energy as a non relativistic scalar and Galilean invariance? If energy is a non relativistic scalar, doesn't it mean that there is a contradiction with Galilean invariance? What i mean is that if i try to accelerate an object within the Galilean...
22. ### I Derivative operators in Galilean transformations

I'm studying how derivatives and partial derivatives transform under a Galilean transformation. On this page: http://www.physics.princeton.edu/~mcdonald/examples/wave_velocity.pdf Equation (16) relies on ##\frac{\partial t'}{\partial x}=0## but ##\frac{\partial x'}{\partial t}=-v## But this...
23. ### I Galilean Invariance and constraints on Forces.

Let's say we have a system of two point particles that can interact with each other by forces that are position and velocity dependent. The forces might or might not be derivable from a generalized potential. Assuming Isotropy of space and homogeneity of space and time, what are the constraints...
24. ### I Galilean transformations x Galilean Group

It seems that there is a difference between Galilean transformations and (the transformations of the) Galilean group, for one thing: rotations. The former is usually defined as the transformations ##\{\vec{x'} = \vec x - \vec v t, \ t' = t \}##, where ##\vec v## is the primed frame velocity...
25. ### Reference frames and Galilean transformation

Homework Statement I am having a issue relating part of this question to the Galilean transformation. Question Relative to the laboratory, a rod of rest length ##l_0## moves in its own line with velocity u. A particle moves in the same line with equal and opposite velocity . How long dose it...
26. ### Derivative for a Galilean Tranformation

Homework Statement Using the chain rule, find a, b, c, and d: $$\frac{\partial}{\partial x'} = a\frac{\partial}{\partial x} + b\frac{\partial}{\partial t}$$ $$\frac{\partial}{\partial t'} = c\frac{\partial}{\partial x} + d\frac{\partial}{\partial t}$$ Homework Equations Chain rule...
27. ### I ##F=\dot{p}=\dot{m}v+m\dot{v}## and Galilean invariance

Hi. In Newtonian physics, total mass is conserved, but open systems can obviously gain or lose mass, such as a rocket. But how can the term ##\dot{m}v## be Galilean invariant?
28. ### I Prove that TDSE is invariant under Galilean Transformation.

I want the proof for a general wavefunction Ψ(x,t).
29. ### Galilean Transformations Problem: Two moving Rockets+Missile

Homework Statement Mary and Frank are each in their own rocket ships moving along the x-axis. Mary's ship passes Frank's ship at t0=t0'=0 with a speed "v" to the right. When t=t1 in Frank's frame, Frank shoots a missile with a speed "u" where u>v in the direction of Mary. At time t=t2 in...
30. ### What are the speeds of P and M while riding Ents and playing catch with rings?

Homework Statement P and M are each riding Ents while playing catch with two rings. P throws his gold ring with a speed relative himself that is twice the speed that M throws his silver ring relative to himself. P and M start off going with the same speed and direction, 30m apart with M in...
31. A

### Heisenberg algebra Isomorphic to Galilean algebra

Homework Statement Given for one-dimensional Galilean symmetry the generators ##K, P,## and ##H##, with the following commutation relations: $$[K, H] = iP$$ $$[H,P] = 0$$ $$[P,K] = 0$$ Homework Equations Show that the Lie algebra for the generators ##K, P,## and ##H## is isomorphic to the...
32. ### I Proof that Galilean & Lorentz Ts form a group

The Galilean transformations are simple. x'=x-vt y'=y z'=z t'=t. Then why is there so much jargon and complication involved in proving that Galilean transformations satisfy the four group properties (Closure, Associative, Identity, Inverse)? Why talk of 10 generators? Why talk of rotation as...
33. C

### Conservation of Linear Momentum and Covariance

Homework Statement Assume two masses m1' and m2' are moving in the positive x-direction with velocities v1' and v2' as measured by an observer in S' before a collision. After the collision, the two masses stick together and move with velocity v' in S'. Show that if an observer in S' finds...
34. ### Galilean Relativity (Invariance) Problem

Homework Statement Imagine two inertial frames, S and S'. Inertial frame S' moves with velocity v0 = 5 m = s in the upward (positive y) direction as seen by an observer in frame S. Now imagine that a person at rest in frame S throws a ball with mass m straight up into the air with initial...
35. ### Prove equation of motion is unchanged under Galilean transformation

Is the attached solution complete? In particular, do we need to prove that ##V'(r_{12}')=V(r_{12})##, where ##V'(r_{12}')## is the potential energy function in the reference frame ##S'##, moving at a uniform velocity with respect to the reference frame ##S##, and ##r_{12}'## is the distance...
36. ### Variance of the EM wave equation under Galilean transformation

For using Galilean transformation, I have to assume that speed of light w.r.t. ether frame is c. W.r.t. ether frame, E = E0 eik(x-ct) W.r.t. S' frame which is moving with speed v along the direction of propagation of light, E' = E0 eik(x'-c't') Under Galilean transformation, x' = x-vt, t' = t...
37. ### Trouble with Galilean transform problem heat equation

Homework Statement 1. The common form of the heat-diffusion equation governing the temperature distribution $$\rho C_p \frac{\partial T}{\partial t}=k\nabla^2T$$ Is this equation valid in any inertial frame of reference? (i.e. does it have the property of Galilean invariance?) If not, can it...
38. ### B Regarding the Galilean transformation of x'=x-vt

Hello everyone, I am confused with the minus sign of x'=x-vt. When there are 2 references frames called K and K' which K is at rest and K' moves to right with velocity V with respect to K. Let there is another frame which is my frame of reference called O. The vector sum of the displacement...
39. ### Generalized Galilean transformation

Homework Statement Write the Galilean coordinate transformation equations for the case of an arbitrary direction for the relative velocity v of one frame with respect to the other. Assume that the corresponding axes of the two frames remain parallel. (Hint: let v have componentsvx, vy, vz.)...
40. ### Galilean invariance: Newton's 2nd Law of motion

Consider a frame S' moving with speed u along +ve x direction with respect to another frame S. Consider a body moving with speed v along +ve x direction with respect to frame S . Both frame are inertials. here,force acting in S frame on the body is $$F\hat x=\frac {dp} {dt}\hat x,$$...
41. ### Lorentz Transformations vs Galilean Transformation

Homework Statement 2. The attempt at a solution 3. Relevant equations In the first problems of that book i was using the Galilean transformations where V1 = V2 + V But if i use that then V1 = 0.945 - 0.6 V1 = 0.345 Is not the same result, so I am confused. In this new problems we are...
42. ### I D'Alembert equation and Galilean transformation

The D'Alembert equation for the mechanical waves was written in 1750. It is not invariant under a Galilean transformation. Why nobody was shocked about this at the time? Why we had to wait more than a hundred years (Maxwell's equations) to discover that Galilean transformations are wrong...
43. ### I Galilean Vs. Lorentz Transformations

I was reading my textbook for my elementary modern class and the author said that a pulse of light from a light bulb would be spherical and could be expressed as x2 + y2 + z2 = c2t2 and x'2 + y'2 + z'2 = c2t'2. Then the author goes on to say that this cannot happen for both reference frames in a...
44. ### Magnification formula for a Galilean telescope

Homework Statement I am asked to draw the ray diagram for an incident plane wave whose rays are at an angle α with respect to the optical axis of the telescope. I have done this, but I need to find an expression for the angle between the outgoing rays and the optical axis, in terms of f1, f2...
45. ### Galilean and Lorentz invariant

Homework Statement Professor C. Rank claims that a charge at (r_1, t_1) will contribute to the air pressure at (r_2, t_2) by an amount B \sin[C(|r_2 − r_1|^2− c^2|t_2 − t_1|^2)] , where B and C are constants. (A) Is this effect Galilean invariant? (B) Is this effect Lorentz invariant...
46. ### B Is Energy Galilean Invariant?

As the title says, is energy Galilean invariant? I'm fairly sure it isn't, since if one considers the simple case of a free particle, such that its energy is ##E=\frac{p^{2}}{2m}##, then under a Galilean boost, it follows that ##E'=...
47. ### I Galilean transformation paradox help

I'm getting quite stuck on this problem here. Galileo said that Xb = Xa - V*Ta. (This follows from dv = dx/t --> Xa - Xb = t*dv --> the above formula) Thus, it is concluded Xa = Xb + V*Ta, but why? In my thought experiment the objects are moving relative to each other, thus if A is moving away...
48. ### A problem regarding Galilean relativity

Homework Statement Two bodies are moving on the same line. When they move away from each other the distance between them changes for 16m in a time interval of 3 s (Δd1 = 16 m ; Δt1 = 3 s). When they move towards each other the distance between them changes for 3 m in a time interval of 3 s (Δd2...
49. ### I Galilean Relativity: Can Experiments Tell Motion Relative to Other Frames?

In Galilean Relativity, laws of mechanics are invariant across frames. In all the frames they are the same. So, in Dynamics and Relativity by W.D.McComb, it is written that this implies you cannot perform any experiment in an inertial frame that can tell whether an inertial frame is moving or...
50. ### I Galilean Equivalence Principle: Extended Objects

The Galilean equivalence principle (or weak equivalence principle) is the statement of the universality of free-fall under gravity. For example, according to Wikipedia, it can be stated as follows My question regards the limitation of the principle to point masses. Does universality of...