Until the End of Time: Mind, Matter, and Our Search for Meaning in an Evolving Universe

by Brian Greene

Imagine you see the car’s sleek red exterior, feel the smooth ergonomic shape of the door handles, smell the unmistakable new car aroma, and so on. Intuitively, we think of these as direct experiences of an external reality, but as we have known for centuries they are not. Modern science makes this explicit. Red light reflecting off the Ferrari’s surface is an electric field that oscillates at roughly four hundred trillion times each second at right angles to a similarly oscillating magnetic field, all traveling toward you at three hundred million meters per second. That is the physics of red light, and that is the stimulus your eyes encounter.30 Notice that there is no “red” in the physics description. Red happens when the electromagnetic field enters your eyes, tickles light-sensitive molecules in your retina, and generates an impulse carried to your brain’s visual cortex, which specializes in visual information processing and interprets the signal. Red is a human construct that happens deep inside your head. And that new car smell? A similar story. The seats, carpet, and plastic wrap off-gas molecules that permeate the car’s interior. There is no new car smell until those molecules waft into your nostrils, brush up against receptor neurons on your olfactory epithelium, and generate an impulse that fires along your olfactory nerve toward your olfactory bulb, which relays the processed signal to various neurological structures for interpretation. As with red, the only pla...