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mangaroosh
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Just a quick question.
I know that it is pretty much taken to be axiomatic, but is time a testable dimension?
I know that it is pretty much taken to be axiomatic, but is time a testable dimension?
jtbell said:What is a "testable dimension?"
Time is measurable.mangaroosh said:would measurable be a better way of stating it?
A.T. said:Time is measurable.
With a clock.mangaroosh said:how is it measured?
A.T. said:With a clock.
Why?mangaroosh said:is that not circular reasoning though?
A.T. said:Why?
EvilTesla said:Not really.
Becouse IF you are correct, and we are using time to prove that time exists. Then if time DIDN'T exist, then we wouldn't have it to prove that it exists.
If you see what I am saying.
Time undeniably exists. We measure it ever day. We experience it every day.
Take velocity, distence devided by time. If there is no time, there is no velocity.
Why time is so differnt from space, and what its underlying properties are is anouther matter.
Fredrik said:These old posts should be useful:
https://www.physicsforums.com/showthread.php?p=1944107
https://www.physicsforums.com/showthread.php?p=1925822
No, it is using a clock measure time.mangaroosh said:is it not using time to prove that time exists?
A.T. said:No, it is using a clock measure time.
You asked if time is a measureble dimension, not to prove that time exists (whatever "exists" might mean). Physics is not about proving that something exists, but about defining how to measure and predicting what you will measure.
No, how would you show that anyway? In physics, if something can be measured it "exists", just like numbers "exists" in math.mangaroosh said:Ok, but before something can be measured does it not have to be shown to exist first?
Yes it is, per definition. A clock is defined as something that measures time.mangaroosh said:a clock essentially isn't really a measurement of time though is it?
You can use any process where measurable quantities change as a clock. Just a matter of conventions and practical considerations.mangaroosh said:It is more a measurement of the Earth's rotation, with a year being a measurement of the Earth's orbit around the sun. Does this mean that time is an intrinsic function of these two things?
James Leighe said:No, a clock just measures time... and has nothing to do with the Earth's rotation.
As a matter of fact, a second (as an example) is defined as 'the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.'. So we can define time using periodic events in elementary particles.
Fredrik said:The concept of time (and any other measurable quantity really) has to be defined twice. You need to define it operationally, i.e. by describing the equipment you intend to use to measure it, and you need to define it mathematically so that you have something in your mathematical model that represents the real-world concept. By using the same word for both things, you're implicitly saying that theoretical results about "mathematical" time should be interpreted as statements about "actual" time in the real world.
So operational definitions should be thought of as axioms of the theory. They are the statements that tell you how to interpret the mathematics as predictions about the results of experiments.
However, I think this is a pretty awkward way to state the axioms of the theory. I prefer to be more explicit. For example, I would take one of the axioms of special relativity to be "A clock measures the proper time of the curve in Minkowski space that represents its motion". This is more explicit than just using the same word for two different things.
A.T. said:No, how would you show that anyway? In physics, if something can be measured it "exists", just like numbers "exists" in math.
Yes it is, per definition. A clock is defined as something that measures time.
You can use any process where measurable quantities change as a clock. Just a matter of conventions and practical considerations.
There is nothing different about time than about anything else in science. You propose a theory which contains some concept, you design an experiment to test the theory, you carry out the experiment, and you see if the results match the theory. So far all experimental results can be explained by theories which include time.mangaroosh said:What equipment would be used to measure time? If we assume that it is to be a scientific test for the existence of time.
A clock. I don't agree with AT's definition of a clock as something that measures time. That would make the definitions circular. When I say "clock" it refers to what we all think of as a "clock". We can be a bit more precise by describing how to build one of these clocks, but the definition can never be as exact and unambiguous as the definitions in mathematics.mangaroosh said:Ok, just with regard to stating the equipment that you are going to use. What equipment would be used to measure time?
That doesn't really make sense. The term "existence" is surprisingly useless in physics. The only thing experiments can tell us is how accurate a theory's predictions are, so the only meaningful definition of what it means for something to "exist" is that it's a concept that's used in a theory that makes good predictions. So the only way to interpret the claim that time exists is that it has a mathematical definition in a few theories (Newtonian mechanics, special relativity, general relativity) that make good predictions. Clocks are of course absolutely essential when we test the accuracy of those predictions.mangaroosh said:If we assume that it is to be a scientific test for the existence of time.
Science doesn't really answer questions like that. Theories make predictions. Experiments test how accurate those predictions are. The more accurate they are, the stronger we feel that we can understand something about how the universe works by understanding the theory. That's all. Science can't ever answer a question like "What is time really?".mangaroosh said:in what way can time can be said to make up the "fabric of reality",
I'd say that your question is based on a (very common and understandable) misconception of science. But you're on to something. All the theories that define the concept of time are making predictions that are less than perfect. So it clearly isn't the case that any of those models includes a perfect representation of time. This problem isn't unique for the concept of time. The same can be said about any observable.mangaroosh said:does it actually make up the fabric of reality or is the notion that it does, based purely on an assumption, that is inherent in mankind, based on a misperception of reality.
My point was that "existence" is not clearly defined in physics, and not really part of physics but rather philosophy.mangaroosh said:saying that something "exists" (in inverted commas), suggests one of two things, either that it really does exist and there is an emphasis on the word exist, or that it doesn't really exist.
This is true for all physical quantities: forces, energy... they all are abstract concepts invented by humans.mangaroosh said:If time exists in the same sense that numbers exist in maths, then that suggests that it is purely in the human mind, as opposed to in reality.
"The nature of the thing" is not a physical quantity that I know of. Why invent so complicated names, if we have a simple on already: "time".mangaroosh said:Indeed a clock is, per definition, something that measures time, however it is the nature of the "thing" that it measure.
In physics quantities are defined by defining how you measure them.mangaroosh said:What is time defined as?
Claims like that are fine, because they describe the mathematical spacetime that's used in general relativity, which is by far the best theory of time (and space, motion and gravity) that we have. I think people should understand that the mathematical concept isn't the same as the real-world concept, and that the relationship between the two is specified by an axiom of the theory, but I don't think we can change the way we talk to reflect that fact every time we say something about time. That would make any statement about physics really awkward. So we'll just continue to say things that seem to confuse the model with the real world, and some of us will try to spread the word about what statements like that really mean.mangaroosh said:In most documentaries that I have come across, time, in particular spacetime, is portrayed as the fabric of reality, which could, potentiall be manipulated. I suppose in a sense, it is portrayed almost as though we, the planets etc. are almost like particles in a suspension tank, that work based on the laws of nature (of which we have a certain, developing understanding), but that that "material" that we are suspended in, can potentially be warped and manipulated.
I am not.mangaroosh said:Is anyone familiar with that lecture and the conclusions or outcomes?
Fredrik said:Claims like that are fine, because they describe the mathematical spacetime that's used in general relativity, which is by far the best theory of time (and space, motion and gravity) that we have. I think people should understand that the mathematical concept isn't the same as the real-world concept, and that the relationship between the two is specified by an axiom of the theory, but I don't think we can change the way we talk to reflect that fact every time we say something about time. That would make any statement about physics really awkward. So we'll just continue to say things that seem to confuse the model with the real world, and some of us will try to spread the word about what statements like that really mean.
Time as a testable dimension refers to the concept of time being treated as a measurable and quantifiable variable in scientific experiments and studies. It involves exploring the effects of time on various phenomena and using it as a tool for testing hypotheses and theories.
Time can be measured in various units such as seconds, minutes, hours, days, and years. In scientific research, time is often tested by manipulating the duration of an experiment or by observing changes over a specific period. It can also be measured using specialized equipment such as clocks, timers, and chronometers.
Considering time as a testable dimension allows for a deeper understanding of the relationship between time and various phenomena. It also allows for the development of more accurate and precise theories and models. Additionally, it can lead to practical applications in fields such as medicine, engineering, and technology.
Some examples of experiments that explore time as a testable dimension include studies on the effects of time on human memory, the rate of chemical reactions over time, and the growth and development of organisms over a specific period. Other examples include analyzing the impact of time on climate change, the aging process, and the evolution of the universe.
One limitation is that time is a relative concept and can be influenced by factors such as perception and measurement error. Additionally, some phenomena may have a complex relationship with time, making it difficult to isolate its effects. Furthermore, the manipulation of time in experiments may not always be ethical or practical.