# Contraintes de la perception et la cognition en physique relativiste

 The following sections (and figures) have been abridged out of this post. La version complète de l'article est disponible sous forme de fichier PDF. ()

#### 4. Explanations Based on LTT Effects Figure 2. Illustration of the traditional explanation for the observed superluminal motion. An object expanding at a speed ratio = 0.8, starting from a single point S. The solid circle represents the boundary one second later. The observer is far away on the right hand side, La (at infinite distance). The dashed ellipse is the apparent boundary of the object, as seen by the observer. Figure 3. The radio jet and lobes in the hyperluminous radio galaxy Cygnus A. Les points chauds dans les deux lobes, la région de noyau et les jets sont clairement visibles. (Reproduced from an image courtesy of NRAO/AUI.) Figure 4. The top panel (un) shows an object flying along $A_-BA$ at a constant superluminal speed. The observer is at $O$. The object crosses $B$ (the point of closest approach to $O$) au moment $t=0$. The bottom panel (b) shows how the object is perceived by the observer at $O$. It first appears at , then splits into two. The two apparent objects seem to go away from each other (along $J_1$ et $J_2$) as shown. Figure 5. The apparent angular positions of an object traveling at different speeds at a distance $y$ of one million light years from us. The angular positions ( $\phi$ in radians) are plotted against the observer’s time $t_O$ in years. Figure 6. Time evolution of the redshift from a superluminal object. It shows the redshifts expected from an object moving at $\beta = 300$ at a distance of ten million light years from us. The X axis is the observer’s time in years. (Since the X axis scales with time, it is also the redshift from an object at 116 light days –ten million light seconds–with the X axis representing $t_O$ in seconds.)