Definition of Time in Modern Physics

In summary, time is a complex concept in modern physics. In relativity and relativistic theories, time is one of the dimensions but is treated differently from space dimensions. In non-relativistic quantum theory, time is not an operator and remains a numerical value like in everyday life. In classical physics, time is also a number. Despite there being different definitions of time, they all ultimately work together in a unified way. The second law of thermodynamics is linked to time being irreversible and affected by physical forces. Time is not a tangible thing, but its existence can be witnessed through the passing of events. It is similar to how scientists look for evidence of things like gravitons through their effects rather than directly observing them.
  • #1
dwf
6
0
I´d like to know what´s the exact definition of time in modern physics. Is it just a dimension, and nothing else?
 
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  • #2
In relativity, and all relativistic theories like the standard model and string theory, time is one of the dimensions, but treated a little differently from the space dimensions (a change in the sign of some numbers). This is also true in general relativity, though there we find that the time dimension, as well as the space dimensions, can bend.

In non-relativistic quantum theory, which is still used, space position is a mathematical "operator" which chnges the value of a wave function, and corresponds to the physical operation of measuring a position. But time is not an operator for technical reasons, and reamains just a numerical value as in ordinary life - so many nanoseconds or whatever.

In classical physica, like ordinary physics 101, time is a number again, like we usually have it.

Having different time definitions seems confusing at first, and you wonder how unified all these different theories could be, with so many different "times". But you really have only three. All of relativistic quantum theory is consistent, and the older quantum theory is kept around because it works well at low speeds, for example in chemistry. Likewise the General Relativity theory works very well at astronomical distances, but even the GR theorists believe it will eventually be replaced with something that is valid at really short distances too.
 
  • #3
Isn't time defined by the 2nd law of thermodynamics? The tendency to disorder is irreversible, so surely time must be linked to this, rather than any other aspect of Physics.
 
  • #4
Well time isn't really a tangible thing physically, but it can be affected by physical things like gravity and velocity, electromagnatism, strong and weak nuclear force. Time is kind of hard to explain but we can witness it by the passing of events.

It's kind of like how the scientists are trying to find evidence of a graviton by it's absence after a particle collision. You won't actually see it, but you see evidence of it's existence.
 

1. What is the definition of time in modern physics?

The definition of time in modern physics is the numerical measurement of the duration of events. It is a fundamental quantity in the universe and is used to describe the sequence and duration of events.

2. How does modern physics define time?

Modern physics defines time as a dimension that is closely linked to space, forming the fabric of spacetime. It is considered to be absolute and universal, meaning it is the same for all observers regardless of their motion or location.

3. What is the role of time in modern physics?

The role of time in modern physics is to provide a framework for understanding the behavior and interactions of matter and energy in the universe. It is a fundamental aspect of many physical theories and is used to make predictions and calculations.

4. Is time considered to be continuous or discrete in modern physics?

In modern physics, time is considered to be continuous rather than discrete. This means that it is viewed as a smooth and continuous flow rather than being broken up into distinct moments or intervals.

5. How does the definition of time in modern physics differ from our everyday understanding of time?

The definition of time in modern physics differs from our everyday understanding in that it is not just a simple linear progression of moments, but rather a complex concept that is intertwined with space and affected by the laws of physics. It is also viewed as absolute and universal, whereas our everyday understanding may be more subjective and relative.

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