Time : what it really is

[KJW]

22 hours ago, geordief said:

Is it possible for the rate of nuclear decay to be any way affected by external circumstances?

There is the quantum Zeno effect where the rate of decay is affected by the frequency of measurement.

 

[swansont]

2 hours ago, KJW said:

There is the quantum Zeno effect where the rate of decay is affected by the frequency of measurement.

 

Has that ever been observed in nuclear decay?

[KJW]

35 minutes ago, swansont said:

Has that ever been observed in nuclear decay?

I don't know. I assume the quantum Zeno effect to be quite general. I have even simulated the effect on an Excel spreadsheet.

 

 

[swansont]

1 hour ago, KJW said:

I don't know. I assume the quantum Zeno effect to be quite general. I have even simulated the effect on an Excel spreadsheet.

I’ve only seen it in terms of atomic de-excitation and tunneling 

[julius2]

On 7/1/2024 at 11:30 PM, Phi for All said:

This is always a big red flag for me. Theory is the strongest explanatory mechanism science has. Are you looking for "proof"? Proof is for maths, but you don't want to do the maths. Rejecting the foundations of spacetime is going to be an uphill battle all the way. Astrodynamics uses those foundations to land a spacecraft on an asteroid millions of miles away. Without them we miss. How does this match up with your observation that time doesn't exist?

It is interesting to see others delving with the fundamentals. Having read quite a few posts I still find it hard to grasp the concept of spacetime.

Space is pretty obvious with the three dimensions of length, width and height.

The concept of time I can "understand". E.g. The "time" it takes from one end of the road to the other. Or the "time" it takes to boil an egg. In other words you "feel" the time and thus have a concept for it. Or for clocks, it is the count of a pendulum swinging back and forth.

I have faith in the concept of spacetime since the empirical evidence is consistent with the theory. And it is used to explain gravity (general relativity). Special relativity is consistent with GPS navigation system operation. So all good there.

Combining space AND time is confusing however.

[Mordred]

Simple way to understand spacetime is to treat time as the Interval using (ct).

So your spacetime becomes (ct, x,y,z) this gives time dimensionality equivalence to length. Ps you will also find that works with the four momentum equations.

Edited 21 hours ago by Mordred

[Genady]

4 hours ago, julius2 said:

It is interesting to see others delving with the fundamentals. Having read quite a few posts I still find it hard to grasp the concept of spacetime.

Space is pretty obvious with the three dimensions of length, width and height.

The concept of time I can "understand". E.g. The "time" it takes from one end of the road to the other. Or the "time" it takes to boil an egg. In other words you "feel" the time and thus have a concept for it. Or for clocks, it is the count of a pendulum swinging back and forth.

I have faith in the concept of spacetime since the empirical evidence is consistent with the theory. And it is used to explain gravity (general relativity). Special relativity is consistent with GPS navigation system operation. So all good there.

Combining space AND time is confusing however.

The length, width, and hight are spatial intervals rather than spatial points. Similarly, "time it takes to boil an egg" is a temporal interval rather than a point in time. The spacetime concept does not combine such intervals. It combines the points. For example, "7 pm on the corner of 5th Avenue and 24th Street in NYC" is a point in spacetime.

Edited 20 hours ago by Genady

[swansont]

35 minutes ago, Genady said:

The length, width, and hight are spatial intervals rather than spatial points. Similarly, "time it takes to boil an egg" is a temporal interval rather than a point in time. The spacetime concept does not combine such intervals. It combines the points. For example, "7 pm on the corner of 5th Avenue and 24th Street in NYC" is a point in spacetime.

And relativity recognizes that the distances between points - including the time interval - is important, because relative motion affects the distance interval or time interval, such that the total is the same for both stationary and moving observers.

[julius2]

1 hour ago, Genady said:

The length, width, and hight are spatial intervals rather than spatial points. Similarly, "time it takes to boil an egg" is a temporal interval rather than a point in time. The spacetime concept does not combine such intervals. It combines the points. For example, "7 pm on the corner of 5th Avenue and 24th Street in NYC" is a point in spacetime.

So, if I understand correctly, "7 pm on the corner of 5th Avenue and 24th Street in NYC" is a point in spacetime, that will never happen again?

[Genady]

2 minutes ago, julius2 said:

So, if I understand correctly, "7 pm on the corner of 5th Avenue and 24th Street in NYC" is a point in spacetime, that will never happen again?

It is a point. A point at a different time or in a different place, is a different point.

[swansont]

3 hours ago, julius2 said:

So, if I understand correctly, "7 pm on the corner of 5th Avenue and 24th Street in NYC" is a point in spacetime, that will never happen again?

Yes. The time coordinate can’t be repeated.

[Markus Hanke]

16 hours ago, julius2 said:

Combining space AND time is confusing however.

Note that you don’t necessarily have to do this - in many cases, it’s quite possible to work with space and time as separate (but interdependent) entities. For example, there’s nothing wrong with using the original 3-vector based formalism of Maxwell’s equations, rather than tensors or differential forms on spacetime. The problem is just that you often sacrifice physical intuition when you do this, because the maths tend to become less transparent.

And sometimes you realistically can’t do without spacetime - for example, writing down the Standard Model without using tensors, spinors, or any other object that requires a concept of spacetime, would be a straight-up nightmare, if it is possible at all.