#NASA, #Space, #astronomy, #διάστημα,
That's a beautifully articulated summary of one of the deepest ongoing debates in modern physics: the arrow of time and why it points relentlessly forward in our everyday experience, despite most fundamental laws being http://time-reversible.You're spot on with the key points:At the microscopic level, the equations of quantum mechanics, electromagnetism, and the strong nuclear force are time-symmetric (invariant under time reversal, or "T-symmetry"). If you watch a video of elementary particles interacting (without weak interactions), you couldn't tell if it's running forward or backward.
The weak nuclear force mildly breaks this symmetry, but not enough to explain the macroscopic arrow.
The dominant explanation for the one-way flow of time is thermodynamic: the second law of thermodynamics and the increase of entropy. The universe started in a highly ordered, low-entropy state shortly after the Big Bang, and statistical mechanics dictates that systems evolve toward higher entropy—giving us the psychological and physical distinction between past (low entropy) and future (high entropy). Memory, aging, and cause preceding effect all emerge from this.
Recent quantum explorations—particularly in quantum information theory, quantum gravity approaches (e.g., AdS/CFT correspondence), and experiments with entangled particles—have revived interest in alternative views:Some frameworks (like the two-state vector formalism or retrocausal models) allow descriptions where quantum states are constrained by both past and future boundary conditions. These aren't "sending signals backward" or changing history, but rather the mathematics treats past and future measurements symmetrically.
Ideas from Wheeler's delayed-choice experiments (and modern quantum eraser variants) show that decisions made "now" can influence how we interpret past events, without violating causality.
In certain interpretations, time's arrow may emerge from decoherence and the amplification of quantum effects into classical behavior.
Ultimately, as you said, time may be more like a fixed, four-dimensional block (as in Einstein's spacetime) in which the "flow" is an illusion created by our embedded, entropy-increasing perspective—much like how a static landscape appears to move when you're driving through it.These ideas don't enable time travel or reverse causation in the sci-fi sense, but they profoundly challenge our intuitive notions of past, present, and future, and continue to blur the line between physics and philosophy.
Source: Physical Review Letters; Nature Physics; Scientific American
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