Time is the apparent progression of events from the past to the future. While it is impossible to fully define the nature of time, we all share many common experiences tied to time: causes naturally lead to effects, we remember the past but not the future, and the evolution of time appears to be constant and unchanging.
Is time relative?
Einstein’s special theory relativity It turns out that the experience of the flow of time is relative to the observer and their position. Earlier, the work of Isaac Newton assumed the existence of a “master clock” that synchronized time throughout the universe. This clock did not actually exist, but the concept allowed Newton’s equations to work. The main idea was that all observers could agree on the exact same time, According to the Internet Encyclopedia of Philosophy (opens in new tab),
However, building on the work before him, Einstein It turns out that the passage of time is relative. In special relativity, moving clocks move slower; The faster you move through space, the more slowly you move through time. The closer you get to the speed of light, the greater this effect becomes.
In the decades since Einstein first proposed the concept, physicists have made a number of measurements that demonstrate this effect. An atomic clock on a jet airplane will tick slower than one on the ground. A subatomic particle called a muon does not exist long enough to travel through the atmosphere, where it is produced when cosmic rays Strike the air molecules on the ground. But since muons travel at close to the speed of light, they exist longer than our point of view, allowing them to complete their journey.
When Einstein developed his theory of general relativity, he put forward the concept, which is known as “time dilationfor the conditions involved gravity, The presence of strong gravity also slows down the passage of time, so a clock in a strong gravitational well (for example, on Earth’s surface or near a black hole) slows down compared to a clock in the middle of space. will last, According to physicist Christopher S. Bairdow (opens in new tab),
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Is time travel possible?
Time travel is not allowed in the future – it is mandatory. Actually, with every passing second we are all moving towards our respective future. The future is inevitable, and it is impossible to escape. But the reality of relativity makes it clear that “jumping” with time is perfectly acceptable.
If a twin sets up in a rocket ship and spends a few years traveling at close to the speed of light, then when they return to Earth, their age will be less than that of their Earth-bound twin. Although only a few years would have passed on the spacecraft, decades or even centuries could have passed on Earth, depending on how quickly the rocket travels, According to Cosmos magazine (opens in new tab), In a real-life example, NASA astronaut Scott Kelly has experienced a few milliseconds less time than his twin Mark (Scott is also six minutes younger), thanks to spending more time in space, at about 17,500 mph. traveling at a speed of (28,100 km/h), According to Live Science sister site SPACE.com (opens in new tab),
But time travel in the past seems to be taboo – at least in all the experiments and observations that have been done so far. For one, the prospect raises all kinds of uncomfortable issues, like the famous grandfather paradox Joe asks what if you went back in time and killed your grandfather: you wouldn’t exist, so you wouldn’t be able to travel back in time to perform the act.
Second, there is no known mechanism in physics that allows time to travel backwards. While some time-travel conditions can be created in general relativity, those conditions require entities that do not exist in our universe (such as matter with negative mass, or infinitely long cylinders).
However, physicists currently do not have a complete understanding of why time travel is forbidden in the past.
Can time be reversed?
Almost all laws and equations used by physicists to understand the natural world are symmetric in time. This means that they can be reversed without changing the outcome. For example, if you watch a video of a ball rising and falling again in the air, without any other context, you won’t be able to tell whether the video was being played forward or backward.
However, there is one aspect of physics that seems to respect the flow of time: the concept of entropy, which is a measure of disorder in a system. according to second law of thermodynamicsEntropy always rises in a closed system, and this growth cannot be reversed.
Physicists do not know whether the increase in entropy gives rise to the “arrow” of time or is it just a coincidence, according to Stanford Encyclopedia of Philosophy (opens in new tab),
Is time discrete or continuous?
Almost all physical theories treat time as a continuum, which is how we see the flow of time as well. There is no small “unit” of passage of time. All events flow smoothly without any interruption or next blockage.
However, a theory of quantum gravity, called loop quantum gravity, envisages the existence of a smaller possible unit of space time, This unit would represent the smallest possible extension of space and period of time. In this theory, what we see as spontaneous, continuous time is actually a stuttering, stalemate progression from the past to the future. But because it occurs for such an incredibly brief period, it appears to be continuous, as if the frames of a film are blending together, according to a 1998 article in the journal by physicist Carlo Rovelli. Live Review of Relativity (opens in new tab),
Is the time real?
Scientists, philosophers, and others have pondered over the nature of time. And although we have learned much about time, such as the reality of time dilation and the possible relationship between time and entropy, we have not been able to give a full account of time.
Some philosophers and physicists have argued that what we perceive as time is just an illusion, an artifact of our consciousness. From this point of view, the passage of time is not real; The past and the future already exist in their absolute limits, just as the entirety of space already exists. What we perceive as time flows is a byproduct of the way our brains work as we process sensory information from our environment, According to physicist Sean Carroll (opens in new tab),
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