## LOG#043. Tachyons and SR.

“(…)Suppose that someone studying the distribution of population on the Hindustan Peninsula cockshuredly believes that there are no poeple north of the Himalayas, because nobody ca pass throught the mountain ranges! That would be an absurd conclusion. The inhabitants of … Continue reading

## LOG#042. Pulley with variable mass.

This interesting problem was recently found in certain public examination. I will solve it here since I found it fascinating and useful, since it is a problem with “variable mass”. A pulley with negligible mass is given (see the figures … Continue reading

## LOG#041. Muons and relativity.

QUESTION: Is the time dilation real or is it an artifact of our current theories? There are solid arguments why time dilation is not an apparent effect but a macroscopic measurable effect. Today, we are going to discuss the “reality” … Continue reading

## LOG#040. Relativity: Examples(IV).

Example 1. Compton effect. Let us define as  “a” a photon of frequency . Then, it hits an electron “b” at rest, changing its frequency into , we denote “c” this new photon, and the electron then moves after the … Continue reading

## LOG#039. Relativity: Examples(III).

Example 1. Absorption of a photon by an atom. In this process, we have from momenergy conservation: If the atom is the rest frame, before absorption we get Description: an atom “a” at rest with mass absorbs a photon “b” … Continue reading

## LOG#038. Relativity: Examples(II).

Example 1. Completely inelastic collision of 2 particles . We will calculate the mass and velocity after the collision, when a cluster is formed. From the consevation of momentum in the collision, we get Then, Squaring both sides: In the … Continue reading

## LOG#037. Relativity: Examples(I)

Problem 1. In the S-frame, 2 events are happening simultaneously at 3 lyrs of distance. In the S’-frame those events happen at 3.5 lyrs. Answer to the following questions: i) What is the relative speed between frames? ii) What is … Continue reading

## LOG#036. Action and relativity.

The hamiltonian formalism and the hamiltonian H in special relativity has some issues with the definition. In the case of the free particle one possible definition, not completely covariant, is the relativistic energy     There are two others interesting … Continue reading

## LOG#035. Doppler effect and SR.

The Doppler effect is a very important phenomenon both in classical wave motion and relativistic physics. For instance, nowadays it is used to the detect exoplanets and it has lots of applications in Astrophysics and Cosmology. Firstly, we remember the … Continue reading

## LOG#034. Stellar aberration.

In this entry, we are going to study a relativistic effect known as “stellar aberration”. From the known Lorentz transformations of velocities (inverse case), we get:             The classical result (galilean addition of velocities) is … Continue reading