What is Relativity: Definition and 997 Discussions
The theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity, proposed and published in 1905 and 1915, respectively. Special relativity applies to all physical phenomena in the absence of gravity. General relativity explains the law of gravitation and its relation to other forces of nature. It applies to the cosmological and astrophysical realm, including astronomy.The theory transformed theoretical physics and astronomy during the 20th century, superseding a 200-year-old theory of mechanics created primarily by Isaac Newton. It introduced concepts including spacetime as a unified entity of space and time, relativity of simultaneity, kinematic and gravitational time dilation, and length contraction. In the field of physics, relativity improved the science of elementary particles and their fundamental interactions, along with ushering in the nuclear age. With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves.
Hello everyone, I am preparing to write an exam project in college about special relativity, however i am missing the critical experiment to prove that it is true. I thought about using the life time of muons, but i don't have a scintillator to detect them, so unless a standard geiger counter...
I made an exercise whose question is like that:
A spacecraft moves with speed v at the axis x. There are two target at the axis x, in which the distance between them is L at the ground frame. Suppose that the spacecraft shoot the target simultaneously when it passes by the target. A|so...
My answer is (A) since I think the motion of the spacecraft will alter the length of the spacecraft (length contraction) but not changing the orientation so the angle will stay the same
But my teacher said my answer is wrong. What is my mistake?
Thanks
I was doing a exercise which considerst he time it takes for light travels a glass with thickness proper D and velocity v. The speed of light is c/n inside the glass.
Now, my approach was to go to the glass frame, take the relative speed between the glass and the light using the trivial formula...
Ok, so basically: There is a frase with a particle moving horizontally with velocity v and a rod parallel to the ground, with rest length L, falling with speed u vertical constant. The rod bounces off on the ground. Describe what happens in the particle frame and find the angle the rod makes...
hello
it is well known that gravitationl force is actually a fictitious force
generally speaking,are fictitious forces still necessary in general relativity ?
the fictitious forces which we experience on a bus or on a car can also be understood as due to the spacetime distortion ?
I want to learn special relativity.I have read a tiny bit of 2nd edition of Spacetime Physics: Introduction to Special Relativity and am liking it. Is it a good book? I also want problems to solve. I tried Special Relativity: For the Enthusiastic Beginner but found it to difficult. Does anyone...
i am having some hard time thinking about this problem:
It is basically this:
Imagine a bulb and a receptor distant L from each other (at the same axis x) inside a room, the roof of the room is at a height d from the bulb and receptor. Now you are at a train moving horizontally, parallel to...
Consider a far-away galaxy that is considered to be currently receding from Earth at 2x the speed of light. (With this 2x c recession velocity, we are speaking of the Vnow, the imputed relative velocity of the galaxy compared to Earth now, not the velocity of the galaxy relative to Earth at the...
I found an interesting list of "must-read" papers in the field of general relativity compiled by Emanuele Berti:
https://pages.jh.edu/eberti2/posts/must-read-paper-list/
Are there any notable exceptions, or other "classic" papers that - in your view - every relativist ought to have read?
While learning about Special Relativity I learned that we use the Transformation matrix to alter the space .This matrix differs for Contravariant and Covariant vectors.Why does it happen?,Why one kind of matrix (Jacobian) for basis vectors and other kind(Inverse Jacobian) for gradient...
Assume that space is a three-dimensional torus ( a 3D donut) . If there is a clock traveling at a CONSTANT speed in a direction parallel to the torus (inside out of the hole) and one clock that is still. Which clock ticks faster and why?
I know that the clock rotating will tick slower, but I...
I'm watching this minutephysics video on Lorentz transformations (part starting from 2:13 and ending at 4:10). In my spacetime diagram, my worldline will be along the ##ct## axis and the worldline of an observer moving relative to me will be at some angle w.r.t. the ##y## axis.
When we switch...
Which is the mathematical procedure to obtain ##\delta r = \frac{GM}{3c^2}## from ##\nabla^2 V = R_{00} = 4\pi G\rho## where ##\nabla^2 V## is volume contraction of a spherical mass of density ##\rho## and ##R_{00}## is the 00 component of Ricci tensor ##R_{ij}##?
A particle is moving along the x-axis. It is uniformly accelerated in the sense
that the acceleration measured in its instantaneous rest frame is always g, a constant.
Find x and t as functions of the proper time τ assuming the particle passes through
x0 at time t = 0 with zero velocity.I
n...
(excuse me for my english, but I'm studying physics and I am not a native English speaker)
One observer OE, is on the ground, we take him as the fixed frame of reference.
The other OT is on the train that is moving relatively to the OE at a costant velocity ( they are both inertial frame of...
If there is a spaceship traveling at 0.999c, the time to reach a star 100 lyr away would be approx 100 yr (assuming no accel and decel). But on the spaceship, It would be 100 yr * sqrt(1-0.999^2) = 4.5yr.
Why do we take 100 yr as the time seen on Earth and not the time on the spaceship?
Summary:: Require confirmation regarding answers to a question posed by the book "Basic Relativity" by Richard A. Mould.
Here is a problem which I encountered while going through Basic Relativity by Richard A. Mould-
I'd like to receive a confirmation regarding the answers I've come up with to...
From the michelson-morley experiment, if a clock were to measure the time period of light hitting the mirror and returning back, it would be 2L/c, where L is the distance between the laser nd the mirror. For a moving observer, the time period would have a factor of *gamma*, the boost factor...
I came across an interesting question in the Hartle's textbook, "An Introduction to Eisntein's General Relativity". The question is as follows:
Explain why a photograph of an object moving uniformly with a speed approaching the speed of light, parallel to the plane of the film appears not...
For a observer on Earth, a rocket takes Mike from Earth to Pluto with a speed of 0.82 c for 33.72 yr. Find the space-time interval for the two events such as Mike leaving the Earth and reaching Pluto considering Pluto is at rest relative to Earth for the observer on Earth.
I confess that i am...
There are several theoretical analyses of 2 dimensional or of multi-dimensional universes.
Now, we live in a special universe that follows Newton's first law (A body at rest or a body in motion shall continue to be at rest or in motion till acted upon by an external force), and consequently...
Is mass relative? does the faster you go change your mass? Because according to the Energy calculations E = ymc^2 at speed and mc^2 and since the speed of light is constant, does that mean that mass changes?
[Thread edited by a Mentor to remove personal speculation]
Hi All,
I've been doing some reading on the above but having some problems understanding certain parts of it (maybe it's wrong from Wikipedia!) To simplify it for me I will first pose a simple scenario where we are not factoring in speed yet, then go from there.
Say we have two planets A and B...
Hi,
I've a doubt about the application of the principle of relativity as follows.
Assume as principle of relativity the following statement: It is impossible by any experiment performed inside a "closed" laboratory to say whether we are moving at constant velocity or staying at rest.
Consider...
Time when the left beam hits the left wall in the ground frame
##vt_1-x = c t_1##
##t_1 = \frac{x}{c+v}##
Time when the right beam hits the right wall in the ground frame
##ct_2 = vt_2 + y##
##t_2 = \frac{y}{c-v}##Setting the times equal to each other with the constraint x+y=L to find x and...
Assumptions
1. General Relativity is the modern and most complete widely accepted theory of gravitation, formulated in a background independent, geometric way.
2. General Relativity is formulated in a manner consistent with Special Relativity and I could imagine that it might be possible to...
We study metrics, in them, we take time as a coordinate. I mean to say that if time is a coordinate then in normal mathematical language, we can have negative coordinate values as well. This confuses me a lot as I want to see and understand the concept from the true physicist's perspective...
Sine-Gordon model is looking trivial 1D model: just
$$\phi_{tt} = \phi_{xx}-\sin(\phi)$$
which has physical realization as lattice of coupled pendulums, e.g. nice video:
Despite looking so trivial, it e.g.:
has analogues of massive particles ("kinks") corresponding to complete rotation -...
If the statement above is correct, I do not understand this concept. I guess by charging my phone I am not producing matter. Does it mean in this case, energy converts to mass (not matter)? Can someone please explain this?
First I wrote in ##S'##, by using Gauss theorem
$$
\int_{\Sigma} \underline E' \cdot \hat n d\Sigma = \frac Q {\varepsilon_0} \rightarrow E'(r)2\pi rH=\frac{\lambda'H}{\varepsilon_0}
$$
$$
\underline E'(\underline r)=\frac{\lambda'}{2\pi\varepsilon_0r}\hat r
$$
Its components are...
Homework Statement:: This isn't a homework but more of a conceptual question.
Relevant Equations:: Proper time, ##\tau##
Simply put, the proper time between two events as observed in an unprimed frame is calculated along the timelike worldline between the two events. This implies that the...
The only way I know of to derive special relativity is to start with the two postulates, derive the Lorentz transformations, and rewrite the laws of physics consistent with those transformations.
Are there alternative ways to derive special relativity?
Thank you.
Does $$\partial^\beta(g_{\alpha\beta}A_\mu A^\mu)$$
mean the same as $$\frac {\partial (g_{\alpha\beta}A_\mu A^\mu)}{\partial A^\beta} ?$$
If not could someone explain the differences?
a) We use the definition of speed:
v = delta_L/delta_t
delta_t = delta_L/v = 45000 m/(0.99540*3*10^8 m/s) = 1.55*10^-4 s
b) We use the length contraction equation:
delta_L = L_0*sqrt(1-v^2/c^2)
L_0 = delta_L/sqrt(1-v^2/c^2) = 45000 m/sqrt(1-0.99540^2) = 469698 m
However, the solution shows...
Does the law of conservation of mass fail to meet the first postulate of the special theory of relativity(the laws of physics are the same in all inertial frames of reference)?
It would be wholly exaggerative for me to say that I have this story "in the works", so "I have an idea for a story" would be far more fitting!
This story involves a method of terraforming which requires manual control of robotic drones from a high-speed orbital ring, made from unobtainium and...
I am doing a project where the final scope is to find an extra operator to include in the proca lagrangian. When finding the new version of this lagrangian i'll be able to use the Euler-Lagrange equation to find the laws of motion for a photon accounting for that particular extra operator. I...
How does general relativity shows the conservation of energy. Because I was reading and listening to something today that touched on this subject. It almost seems as though if you scale GR to larger sizes it stops working and turns into an incomplete law of nature like Newton's laws of gravitation.
It is an electron initially pushed by the action of the electric field. The vectors of force and velocity are parallel to each other.
Here's the questionA possible expression of speed as a function of time is the following:
$$v(t) = \frac{At}{\sqrt{1 + (\frac{At}{c})^2}}$$where is it $$A...
It is an electron initially pushed by the action of the electric field. The vectors of force and velocity are parallel to each other.
Here's the questionA possible expression of speed as a function of time is the following:
$$v(t) = \frac{At}{\sqrt{1 + (\frac{At}{c})^2}}$$where is it $$A...
I stumbled across a cheap copy of Synge’s Special Relativity. I know that it was an important book, but there is an undercurrent in the comments that it is now dated. Is it still worth spending time with?
I have been looking through some of the threads about the twins paradox in relativity. It’s clear there’s a lot of confusion on this, and I am yet one more person very confused on this.
So I was thinking about a hypothetical experiment, and I will lay out my hypothesis of what might...
Can someone give a meaningful explanation that the relative speed of two oppositely directed light beams is why only one light speeds?
I understand that based on the Einstein relativity theory, the relative speed of two beams is C, because nothing can be quicker than light speed. However it is...
As widely separated particles within a large enclosed space are differently affected by the nonuniform gravitational field of Earth, to use the Newtonian way of speaking, two particles released side by side are both attracted toward the center of Earth, so they move closer together as measured...