Physics often times does not align with what we expect. But really, there is no reason that the physics we experience here on our planet with our limited senses should lead us to perfectly predict how physics and reality play out across the universe. Trespassing on Einstein’s Lawn is an excellent physics book because it takes readers with little scientific background through the complex paradoxes and challenges of physics to explore the furthest reaches of our scientific thought. Author Amanda Gefter herself is not a physicist, and learned to understand physics first as a hobby, and later (as detailed in her book) as a bit of an obsessive search for the universe’s ultimate building block.
Along her journey, Gefter introduces us to John Wheeler, a physicist who wrote with an almost poetic style when describing the complex science that he worked on. Wheeler helps us understand that one of the things within human experience that is so fundamental to how we view reality, is not quite as solid as we would expect. He is quoted by Gefter writing, “We used to think that the world exists ‘out there’ independent of us.” When we study physics we are actually adjusting and changing the past. We are not looking at an independent system that existed before us a certain way. When we measure and observe the past, we actually can change it from the present. This is explained by Gefter with further help from Wheeler by describing experiments with photons to measure how sub-atomic particles travel. Light is made of photons, but it acts as a wave, with probabilities based on the wave function determining where the photons of the light will be. Once, however, we make an observation of a single photon, the probabilistic wave function ceases to exist, and the photon acts as a particle, and not as a wave. Up until we make our measurement however, the photon is a series of probabilities and behaves as a wave, the same way a wave behaves in the open ocean, and not as a particle on a direct path.
Gefter writes, “Delayed-choice experiments have been carried out in laboratories, and each time they’ve worked just as wheeler suggested. It’s an established scientific fact: measurements in the present can rewrite history. No, not rewrite. Just write. Prior to observation, there is no history, just a haze of possibility, a past waiting to be born. ‘There is no more remarkable feature of this quantum world than the strange coupling it brings about between future and past,’ Wheeler wrote. If observations we make today can create a billion-year-old past, so, too, can observations made in the future help build the universe we see today.”
In the quote above Gefter is describing the same experiments with photons, but looking at photos billions of light years away from us that had to travel across the universe and split on one side or another of a black hole, universe, or other star to reach one of our telescopes. The path taken by a given photon is best described by the probabilistic wave function with all the features, such as frequency and amplitude, of physical waves that we can observe on earth. But once we make an observation in a telescope to measure the path the photon took around a galaxy, black hole, or star, the wave function no longer describes the photon, and the photon has to have followed a set pathway, a pathway that was not determined until it reached our planet, billions of years after it was emitted from its original source.
The physics is beyond my ability to describe, but the key point is that we are human and have limited brain space and experiential ability. We can only experience first hand so many sensations and realities. More possibilities exist than we can experience and understand. Thinking that we can ever describe reality in the most comprehensive manner is a great dream for scientists and physicists to work toward, but we will always be limited by the fact that we are human and can only experience the world in so many ways. Things that we take to be so certain, like history and the passage of time, seem to be interconnected with the present and the future in ways that we can’t quite explain right now.