It is often said that the the phrase "before the BIG BANG" is meaningless because the BB is the beginning of things, time included. My question is "Is the phrase truly meaningless?" I take it as axiomatic that a real event occurs only if it were already a possible event. If the BB did indeed happen then it must have been the fruition of an antecedent possibility - some entity 'before the BB'. ERIC STOCKTON, ORKNEY UK

I, too, have heard it said that the phrase "before the Big Bang" is meaningless. One analogy I have heard drawn is between the phrase "before the Big Bang" and the phrase "more northerly than 90 degrees north latitude". Just as the latter phrase refers to no real location on Earth, so the former phrase is supposed to refer to no real location in time. According to cosmology's current picture of the Big Bang (as I understand it), the analogy is apt. (Of course, that doesn't rule out the possibility of further scientific developments resulting in corrections to the theory of the Big Bang.)

It may seem unsatisfying to you that a scientific theory could just rule out as "meaningless" a notion that seems pretheoretically to be perfectly sensible. Intuitively, it seems like the question "What happened before the Big Bang?" ought to have an ordinary answer, rather than a cop-out answer like "There is no such time." However, the history of science is full of examples of questions that were once thought to have ordinary sorts of answers but later were discovered not to do so. These were not cop outs. Rather, they were consequences of well-confirmed scientific theories. For example, it was once believed that in order for a body to keep moving at a constant speed in a constant direction, something must continually be acting upon it; otherwise it would slow down and eventually stop. That seems like a sensible idea, based on our everyday experiences. However, Newton discovered that the question "What keeps this body moving in a constant speed in a constant direction?" has no answer because it is based on a mistaken view. According to Newton's first law of motion, a body that is acted upon by no force at all will keep moving uniformly; forces cause accelerations, and motion in a constant speed at a constant direction involves no acceleration. Consequently, that motion could be maintained indefinitely, and would be in the absence of anything acting to change it. Perhaps science has discovered that the question "What happened before the Big Bang?" is in this respect like the pre-Newtonian question "What's keeping this body moving in a constant speed in a constant direction?"

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