Today's soundtrack is Fear Factory: Genexus.
It is with great sadness that today we bid farewell to one of the greatest minds of our time, Dr. Stephen Hawking. In his honour, I've bypassed the Randomizer and will be reading a Chapter 2 of A Brief History of Time, "Space and Time."
Hawking begins by introducing readers to our modern understanding of the identical fall rates of bodies of different weight, which was given to us by Galileo; prior to Galileo's demonstration that two differently-weighted balls rolling down a smooth slope would accelerate at the same speed, people believed Aristotle's claim that heavier bodies fell faster. Hawking breaks down the concept thus: "A body of twice the weight will have twice the force of gravity pulling it down, but it will also have twice the mass. [...T]hese two effects will exactly cancel each other, so the acceleration will be the same in all cases" (p. 25).
Galileo's experiments proved that force does not simply set a body in motion; rather, the real effect of force is to change the speed of a body; thus, a body not influenced by force will remain moving at a constant speed in a straight line (Newton's first law).
There is no absolute standard of rest, and there is no absolute position in space, and there is no absolute time (as addressed by Einstein's theory, which stated that "the laws of science should be the same for all freely moving observers, no matter what their speed" (p. 31)), explaining why light cannot travel faster than a certain speed, regardless of the observer's movement in relation to the source of light. The theory of relativity also explains that no normal object can reach the speed of light. The theory of relativity not only shows us that there is no absolute space or time, but that space and time are intertwined; birthing the term "space-time."
The number of dimensions simply refers to how many coordinates are required to point to a specific event - "something that happens at a particular point in space and at a particular time" (p. 34) - within it. Space-time requires four coordinates: longitude, latitude, altitude, and time. A map only requires two: longitude and latitude. An appointment on the calendar might use four: time, street, address, apartment number.
Because the speed of light is limited, we can only be affected by events after the light from their source reaches us; if the sun died, we would not be affected by the event until approximately eight minutes had passed - enough time for the light from the sun to stop reaching us. When we look at the stars, we look into the past. One problem to address here is the speed of gravity - Newton believed that gravity's effects would be instantaneous; however, we have found that gravity does have a "speed," and Einstein's theory of relativity shows us that gravity is not simply a pulling force like magnetism; rather, it is a warp in space-time. Einstein's theory also showed that the closer an observer was to a high-density object, the slower time would be for that person; conversely, the further from high-density objects an observer is, the faster that time will be perceived by him. So there is no absolute time: there is only personal time that is dependent on where the observer is and how fast he or she is moving.
Hawking closes by saying that Einstein's theory of relativity "implie[s] that the universe must have a beginning and, possibly, an end" (p. 44).
Rest in peace, Dr. Hawking. A still more glorious dawn awaits...
