Our perception of time is quite simple: past actions are the past, what we live is the present, and the things we have not lived are the future. Practically, time in our brain has only one direction.

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According to the physical laws governing the Universe, things are not like that. Most natural laws are "reversible" in relation with time, which means they would work well even if time goes backwards.

Physicists suggest that gravity is not strong enough to force each object to move in one direction.

Stephen Hawking called this phenomenon "the psychological arrow of time", and he assumes that the present becomes past, after it was once the future.

Einstein's time

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For millennia, the brightest scientists have tried to solve one of the greatest enigmas of humanity, the nature of time.

"Does Time Have a Beginning?"
"Will it ever end?"
"Why is it just moving in one direction?"
"What is actually the time?"

Albert Einstein overturned all existing theories when at the beginning of the 20th century he demonstrated that time is relative and depends on motion and gravity. Its revolutionary theory opened the way for studying black holes, wormholes, and travel over time.

Psychological time is not as objective as physical time. Albert Einstein said that "an hour spent in the company of a cute girl goes much faster than an hour spent in a dentist's chair." That's why watches came. The scientific way of measuring objective time, outside of personal experiences.

Aliens have a different life, and that's why we can not see them

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With a different gravity, a different life can generate a different time. And this would make those aliens look very different at Cosmos. Since we only look at the Cosmos with our time, we can only see a small part of the Universe. Similarly, aliens, can see another small part of the Universe.

Let's get out of this chronocentrism.

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In this way we could see extraterrestrial life. Let's put this in a historical context.

• Over 2,000 years ago, we thought that Earth was at the center of the Universe, we had a geocentric vision.
• After the Middle Ages (in 1543) we realised that the Earth is not at the center of the Universe, but the Sun is, so we got a heliocentric vision.
• Around 1900, we learned that the speed of light is constant, so we put our time in the center.

Time accompanies us everywhere, reminding us of the uniqueness of every moment of our passage through the Universe. Could Einstein be right when he said that time is relative? Could we travel in time?

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Sources:
2 Futures can Explain Time's mysterious Past?
Time Might Only Exist in your Head
The Arrow of Time
Photos Sources

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Let me know your opinion about this topic, your comments and upvotes are appreciated, @jwolf.