We decided to explain the principle of how a mirror reflects objects to aliens.
First, we’ll take a mirror with us to meet the aliens, and show them the phenomenon in the mirror – the equal true reflection of objects can be seen from the mirror. Then we’ll use the Pioneer Plaque to explain the principle of the mirror to aliens. On the plaque, we would draw a human figure on the left side with solid lines, and an equal human figure on the right side with dashed lines; in the middle of the two figures, there would be a vertical solid line representing the mirror. There would also be two straight solid lines on the left side to repent the incident light and reflected light; on the right side, we would draw a dashed line whose track is symmetrical with the solid reflected light and centered on the middle line, connecting the solid incident light and dashed human figure. As we already know from the reading, the aliens can understand the chemical symbols, so we would write the chemical formula of the mirror under the middle line which represents the mirror.
The discussion above gives the basic idea of how a mirror is going to be presented in front of aliens. We have to go a little further into how it works in the way aliens think. From the book, we have already understood that aliens know that lights only go in straight lines between two points because lights choose the line with the smallest distance and time. The law of the mirror is that when lights hit the mirror, they bounce off the mirror into a new straight line. Lights that strike the mirror travel in a way that the two angles between each beam are equal. Suppose there are two points on one side of the mirror; one is an eye and the other one is an object. If there is a beam from the object and aim to travel and go into the eye with the help of striking the mirror, the shortest distance contains two parts, one before the striking and one after the striking. When there is an artificial point of the object constructed on the other side of the mirror, the shortest distance will be a straight line with the same distance on both sides. Again, the shortest way to make the eye see the artificial object on the other side is still a straight line that connects the eye and the artificial object, which makes the statement that the angle of incidence and the angle of reflection are equally true and understandable for aliens. The artificial object is what the eye perceives in the mirror. Though the aliens may not know how to distinguish the meaning of solid lines and dashed lines, as we already show them the real phenomenon in a real mirror at the beginning, we suppose they can understand what each line is representing to on the Pioneer Plaque. Therefore, this is how aliens would understand lights go to the mirror in such a way that they come into the eye at least time and shortest distance.
Co-written with Joy, Zhu