Do We Know where We Are Standing?
Someone in Manhattan, quite full of alcohol, approached a police officer and asked: "Where am I, sir?" "You are on Fifth Avenue at 34th Street; this is the Empire State building, and in that direction..." "No details, please", interrupted the drunk. "Just tell me, what country?" Does this happen only to drunk people? Although not in the same way, astronomy and physics are also altering our understanding of location and time.
When someone asks us where we are, we respond with an address or a reference to a familiar place. A prankster might say 'I am here'. "Where is here?" could replicate an astronomer. "Planet Earth turns around our Sun at eighteen miles per second and the whole solar system moves around the center of the Milky Way at a speed seven times faster. When you finished pronouncing 'here', your location was already quite far away from the place where you were when you thought to say it".
Even at such speeds, the notions of distance between two points and the time to cross it were quite clear by simply applying Isaac Newton's motion laws, regardless we were referring to the gigantic cosmos out there or to the park at the corner: Distance is speed multiplied by time; walking five thousand feet, at one thousand feet per minute, takes five minutes.
In our high school physics, space had three dimensions: length, height and depth. Quite simple! We had difficulties, of course, with psychological time -a minute of love is shorter than a minute under water- but a second was equivalent to one sixtieth of a minute; this, one sixtieth of an hour; and this, one twenty-fourth of a day.
From 1967 on, it is no longer so simple: A second is “the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom approaching the theoretical temperature of absolute zero” Come on! You don’t believe this? Check it in Wikipedia.
We used to have a notion, mostly intuitive but reliable, of what both one yard and one second were. But then Albert, this is how his admirers call Einstein, came up with the idea that space and time were an inseparable continuum, a stretchy, 'bendable' medium... Spacetime was the name they gave to this 'plastic', ethereal entity, home of all existing stuff. It was at this point that the subject became indeed intricate.
In this space-time there are singularities, hypersurfaces, black holes, wormholes and other phenomena whose implications only gifted minds understand. Supposedly, wormholes are some kind of tunnels, not yet observed by any telescope but mathematically demonstrable, that we could enter at one end from the 'here' and the 'now', the conventional side, and come out the other end to a different place and a different time age. Hypothetically, we could enter a wormhole on a cosmic bus at one end and come out at the other at a time prior to the beginning of the trip. This matter can be grasped only by the prominent guys at the very best universities; the rest of us, mortals, must believe in St. Albert and entertain us with 'Interstellar', the celebrated movie.
The curved space-time is the cause of gravity, the force discovered by my also admired Isaac in the seventeenth century. As in a curved spacetime, it is impossible to move in a straight line, Isaac had gone mad with Albert’s theories: There is no 'here' without 'now' anymore, and as the ‘now’ just passed, we cannot say with certainty that we are ‘here’.
Returning once more this note’s initial question, do we know where we are standing now? I think so: Right here, I insist. If I am not within somebody’s eye sight, I will send her the exact coordinates that the global positioning system (GPS) on my phone provides.However, Don Marolf, a theoretical physicist at the University of California, Santa Barbara, is not so sure. “To ask a question about here, we should know what we mean by ‘here,’ and that's not so easy to do,” Marolf says. Was not the world simpler with Newtonian physics? For one thing, I know that we are on planet Earth. On the other hand, I have my doubts if I can make fun of the drunkard of Manhattan.
Atlanta, November 20, 2015