The inexorable arrow of time: why time only moves forward

Неумолимая стрела времени: почему время движется только вперед

The past is gone, future has not yet arrived, and only the present is with us in the same moment. But why is the order of events is like this? Why shed tomorrow tea yesterday will not leave a stain on the carpet?

Every moment in which we find ourselves, carries us from past to present and then to future. Time always moves in one direction. It never stops and never moves back. For us the arrow of time always points forward. However, if we look at the laws of physics – from the provisions of Newton to Einstein, from Maxwell to Bohr, Dirac to Feynman, they look time-symmetric. In other words, the equations that govern reality, there is no preference of the direction of time. Solutions describing the behavior of any system obeying the laws of physics as we understand them, is equally effective as for time moving in the past, and for a time directed to the future. But experience tells us that time moves only in one direction – forward. So, where does the arrow of time?

Many believe that between the arrow of time and entropy have a connection. While most people usually equate entropy to “disorder” is lazy and not entirely accurate description. On the contrary, the entropy should be thought of as the measure of how much thermal energy potentially can be converted into useful mechanical work. If you have a lot of this energy is potentially able to do the job, it is a system with low entropy, whereas if you do little, your system has high entropy. The second law of thermodynamics is an important ratio in physics States that the entropy of a closed system can either not change or increase over time, i.e. it cannot decrease. In other words, over time the entropy of the entire universe must increase. This is the only law of physics that has a preferred direction of time.

So, does this mean that we perceive time because of the second law of thermodynamics? Whether this is due to the fundamental relationship of the arrow of time with entropy? Some physicists believe this is so. In the project in 2016, held at the YouTube channel MinutePhysics and physicist Sean Carroll, author of several popular science books, whose interview you can read in issue number 39 of the magazine Naked Science, an attempt was made to answer the question, why is time not moving backward. In the end, physics came to the conclusion that this is due to entropy.

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