# What is Special relitivity: Definition and 13 Discussions

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1. ### Special relativity and standard configuration

1. list three events and determine position and time of three events in planets frame of reference I think the 3 events are: E1- Spaceship is at planet A and sends the light pulse E2 - light pulse arrives at planet B E3- spaceships arrives at planet B 2.create a diagram showing planets frame...
2. ### B Is velocity the reason for the time dilation effect?

Hello! I try to understand how in different frames clocks tick and stop simultaneously but show different time? I suppose that velocity is reason of time dilation effect but I'm not sure. Thanks.
3. ### I Calculate Length Contraction for Accelerated Motion to Proxima Centauri

Let's assume a spaceship traveling from the Earth to the Proxima Centauri with constant acceleration g = 9.81 m/s2. The ship is accelerating the first half of the trajectory and decelerating the second half. I calculated the velocity profile from the Earth reference: The travel time on...
4. ### I Twin paradox for (accelerated) dummies?

Applying the Lorentz transformation to velocity and acceleration, we can easily obtain that Aγ3 = α, where A is the acceleration measured by the stationary observer and α is the proper acceleration of the relative moving object. From this point, the equations for a constant accelerated motion...
5. ### I When and how can I apply Born rigidity condition?

Hello, I try to better understand how and when I can apply the Born rigidity condition. So, for the following example: We've two space probes (Pa and Pb), that travel at an exact equal and same proper acceleration. At a given time tb0 in Pb, and as measured by Pb, the distance is Lba0 (it's...
6. ### The binding energy per nucleon of tritium

Hi, I know from conservation of energy that ##E_i = E_f## Thus, ## M_h c^2 + binding energy = M_{he}c^2+ M_e c^2 + K = M_{he}c^2 + 0.5 MeV + 0.0186 MeV## If I'm right I have to find ##M_{he}c^2##, but something is missing in my understanding, since I don't see how to find that mass energy...
7. ### A Thought experiment in relativistic quantum mechanics?

Background --- Consider the following thought experiment in the setting of relativistic quantum mechanics (not QFT). I have a particle in superposition of the position basis: H | \psi \rangle = E | \psi \rangle Now I suddenly turn on an interaction potential H_{int} localized at r_o =...
8. ### I Energy Density & Mass Density: Explained

Hi everyone! I'm currently strudying some astrophysical equation of states, some stuff about Fermi's gas and I'm kinda confused about the relation between the energy density and the mass density, $$\frac{\epsilon}{c^2}=\rho.$$ I don't get why they do not use whole ...
9. ### B Special relativity - frame of reference

This must be a basic question. :) Bob and Alice have the same age. So in special relativity Bob leaves Alice and travels at very high speed and when it returns is younger than Alice. Bob's time is dilated and his space is contracted from Alice frame of reference. But now, if I take Bob's frame...
10. ### I A question about invariant mass

A question of invariable mass. In a inertial system, the invariable mass of a system never change with time. This system may not be an isolated system. Whether in any inertial system, the invariant mass of the system remains unchanged.Or, in a certain inertial system, what is the necessary and...
11. ### On the relativity of time and speed

Speed can only be measured relative to some other object, like the speed of a tennis ball during a match at Wimbledon can only be measured relative to the ground, or a cloud, or the planet Mars. On the other hand, time is relative. An object traveling at speeds approaching the speed of light in...
12. ### Solve Relativistic Momentum PROBLEM - Extra Factor of u Explained

PROBLEM SOLVED - the worked example I was referring too was wrong :/ ---------------------------- Hello, I've been stuck on a question in one of my SR problem sets for some time now, and managed to find a worked solution to a similar problem online. I've attached an image of the problem (the...
13. ### Can Anna Reach Planet 2 in 30 Years?

Homework Statement It takes light 40 years to get from planet 1 to planet 2 anna who was just born leves planet 1 to go to planet 2. can she make it to planet 2 in 30 years? Homework Equations L=Lo/Yv V=Dist/Time Yv=1/(1-V^2/c^2)^(1/2) The Attempt at a Solution I know the anwser is...