I really like the idea of parallel universes. Due to the recent events in the world related to the CoVID-19 pandemic, I especially often think about how events would develop in a parallel universe without a pandemic, or in a universe in which this pandemic is the fifth in a row, and so on. But what I definitely didn't think about was a parallel universe in which time goes backwards. Agree, what is the point in the existence of such a universe? However, we sometimes forget that we ourselves endow certain events with meaning, and the Universe owes us nothing. She doesn’t care what we thought of for ourselves, she simply exists and can be as crazy and meaningless in our understanding as possible. So, a few years ago, a series of amazing discoveries led physicists to the conclusion thatthat our Universe was born simultaneously with another Universe - which is an exact reflection of ours, but that time in it goes back. But how is this possible?
Does time exist?
In 2016, two different groups of physicists studied the passage of time in the universe and suggested that the Big Bang, which occurred about 14 billion years ago, in addition to our universe, could have spawned a mirror universe in which time moves in the opposite direction: backward, not forward. In principle, if you look closely at the mirror universe, you can see that time moves from the future to the past at the same speed. However, from the point of view of this universe, everything would look as if this is our time moving backward, not forward. But what do we know about time? Physicists have been wrestling with the fact for decades that none of the fundamental laws of the Universe states that time must necessarily move forward.
In simple terms, despite the fact that every moment of time in which we are carries us forward, in fact, time - at least as the laws of physics and equations describe it - does not matter which direction to move. In 1927, British astrophysicist Arthur Eddington proposed that there is an “arrow of time” that acts as a fundamental property of a field of physics called thermodynamics. According to the second law of thermodynamics, in any isolated system - such as the universe - entropy (or disorder) should increase. For this reason - whether the arrow of time is moving backward or forward - the universe will always move towards a higher state of entropy.
Our version of the universe and its thermodynamic arrow of time is that when the Big Bang occurred, the universe emerged as a new, whole egg with low entropy. Pretty soon this "egg" was broken and mixed almost beyond recognition, which made everything around him come to a chaotic, high-entropy state. The problem with this assumption is that it does not allow the backward motion of time that the fundamental laws of physics allow. Thus, a broken egg cannot be reassembled into a single whole, and the milk that you poured into your coffee in the morning cannot be separated from this aromatic drink. But what does this mean?
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As New Scientist writes, we define the future as the direction of time in which entropy increases. By studying the movement of distant galaxies, we can predict the future development of space. In this case, we can kind of rewind time back and approach the Big Bang - the moment when there was much less entropy in the Universe. But once we do this, we will inevitably face a cosmic conundrum: Was the Big Bang really the beginning of time? And if so, why does this event have such a low entropy? As you can see, this is a whole series of incredibly interesting questions, the answers to which scientists have yet to find. But how did physicists come to the conclusion that a mirror universe exists?
Does a parallel universe exist?
Six years ago, during an experiment in Antarctica, researchers discovered strange particles that may indicate the existence of a parallel reality. For a month, the authors of the paper, published in the journal Physics, observed a giant hot air balloon carrying a set of antennas floating high over the ice, scanning over a million square kilometers of frozen landscape for signs of high-energy particles arriving from space. When the balloon returned to Earth after its first flight, there was nothing in the data collected except for a strange burst of background noise. The same story happened after the second flight more than a year later.
However, during the third launch, the researchers decided to re-examine the previously obtained data and especially those signals that were identified as noise. On closer inspection, one of the signals turned out to be the signature of a high-energy particle - a neutrino. But this seemed impossible and was clearly not what the specialists were looking for, since instead of falling from above, this particle burst out of the ground.
It is important to understand that since this amazing discovery, all kinds of assumptions have been put forward to explain the existence of the mysterious particles, but they have all been ruled out. But the remaining hypothesis is really shocking, since the explanation is the existence of an upside-down universe that was born at the time of the Big Bang - like our universe - and exist in parallel with it. In this mirror world, everything positive is negative, left is right, and time is running backwards. In fact, physicists believe that the “other” universe is created from antimatter and is expanding in the opposite direction (on the time scale) from the point of the Big Bang. Agree, this is clearly the most mind-blowing idea that you have ever met, and besides, it may turn out to be true.
Of course, this does not compare with my favorite hypothesis of time, which was invented by the famous science fiction writer Kurt Vonnegut in the novel "Slaughterhouse Five or the Children's Crusade." According to the plot of the protagonist Billy Pilgrim, aliens are abducted from the planet Tralfamador, who, unlike you and me, are able to see the entire arrow of time at once and can move along it as they want. One way or another, our Universe is very strange and to understand how everything works and whether parallel worlds exist, we will need a lot of time.
Lyubov Sokovikova