Time is defined operationally to be that which is measured by clocks. The SI unit of time is the second, which is defined to be

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1answer
14 views

How quickly does the temperature rise in a water container submerged in a hot water bath?

Let's assume I have a small bottle (neglecting any insulation from the walls of the bottle) containing e.g. 150ml water at 4°C and place it in a larger pot with sufficient water at 80°C so that the ...
-5
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0answers
58 views

New time theory? [on hold]

Without having big pretentions, in these few pages I will try to describe my views concerning time, speed, movement and the interesting (to me) conclusions, to which I have come to. First, let us ...
0
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1answer
63 views

Interpretation of time dilation

Is there any interpretiation of time dilation for photons? I mean, how does time work for them? Do photons have any distinction between their own and observer's time? Or is it something like ultimate ...
0
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1answer
55 views

What makes things move in a universe with blocktime? [closed]

In a universe with blocktime the past, present and future all exist at the same time. But what makes it appear that for example my body is going from one movement ...
-1
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0answers
40 views

Find Time it Takes For an Object in Free Fall To Hit Ground With Given Gravity [closed]

Sorry if this seems like a simple question. I'm not that good with physics but I'm willing to learn! So my question is, how can I find the time it takes for an object at "h" height to hit the ground ...
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0answers
38 views

Could time consistently flow in reverse?

Could time consistently flow in reverse? Here is an article about the subject of quantum asymmetry of time and space. Thoughts?
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1answer
37 views

Gravity, Acceleration, Time Dilation and the Equivalence Principle

Three clocks are started at exactly the same time on Earth. The first and second clocks are taken into the vacuum of space. The first clock accelerates until it reaches 100,000m/s, then stays at this ...
1
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1answer
70 views

Does time symmetry still holds when a particle drops into a black hole?

When a particle drops into Earth, it hits the ground and rebounds, if time reverse, it is equivalent to another particle moves with same speed but opposite direction. But at the case that a particle ...
0
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1answer
36 views

Could we recognise if time was running at a different rate for one species than another? I.e a human and an ant

My question is quite simple if time ran at a different speed for smaller creatures, how would we be able to observe this or confirm by experiment?
3
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1answer
62 views

Most efficient speed to travel at, considering the effects of time dilation; according to Special Relativity

I understand that this question has recently been asked, and yet not answered to the greatest and most understandable extent, but I was wondering whether travelling at the speed of light is really the ...
0
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1answer
44 views

How is Zeno's Dichotomy Paradox resolved according to physics? [duplicate]

I always thought of quantum space and quantum time as a solution, but then i figured out that "quantum space-time" is not actually true(yet). I've also heard of the calculus approach and limits, but i ...
10
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3answers
483 views

Age of the universe versus absolute time [duplicate]

In Wikipedia, the age of the universe is defined as the "time elapsed since the Big Bang" while "time" links to "the cosmological time parameter of comoving coordinates" which itself links to "the ...
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3answers
101 views

Observing a point 13.82b ly away, 1b years ago

I understand that we can observe far away galaxies to get an idea how the universe looked like in the past. Assuming the universe is 13.82b years old, would it be correct to say that if we looked at ...
1
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1answer
28 views

Does matter stacks up as it approaches Black hole?

When something approaches Black hole it'll experience time dilation with respect to a frame away from the black hole. So to an observer away from the hole the object would seem to slow down until ...
2
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0answers
30 views

What factors affect decoherence times? [closed]

The question say it all. For example is it the mass of the system? The amount of energy? The species of atom? The electric charge?
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0answers
14 views

Data: decoherence time

Searching for experimental data on decoherence time. For example, this type of data can look like (but is not limited to): atomic species (eg. Carbon) vs. decoherence time. Physics stackexchange ...
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2answers
112 views

Is there an equivalent of the Planck length for time?

Is there an equivalent of the Planck length for time? I'd just like a term I may use (high-level) for a similar "unit of time"? I am not looking for a debate on how discrete time might be, but if ...
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1answer
107 views

Speed of light or speed of time?

Proxima Centauri is about 4.22 Light Years, so if there is anyone that could see us, the image of us would be 4.22 years old, if we depart at 99.99% the speed of light we would arrive almost instantly ...
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1answer
62 views

Theoretical implications of multidimensional Time [duplicate]

While the idea of extra spatial dimensions has been around for quite a while now, is there a possibility or any theory which proposes extra time dimensions? If so, what could be theoretical ...
1
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1answer
48 views

What is the physical significance of taking derivative with respect to proper time?

I would like to know if there is any physical significance associated with the derivative of a quantity with respect to proper time or is it just a mathematical trick. Since proper time is measured in ...
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1answer
77 views

Position from velocity time graph [closed]

I have taken Calculus before but unfortunately no equation is given so I have to do it the old way. An object is at x = 0 at t = 0 and moves along the x axis according to the velocity-time graph ...
4
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3answers
131 views

Is there really a direction of time?

Laws of physics are (almost) time symmetric, so a time-reversed description of a physical process is as qualified as the original one. What's the reason then, that in reality one version seems to ...
0
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0answers
19 views

Time taken to cover a point object in a circular region

I'm assuming a finite width rotating beam with increasing width as it gets closer to the circular edge. I'm trying to find the time it takes the beam to cross a point object at some distance from the ...
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0answers
35 views

Gravitational Time Dilation

In my calculus class (high school), I'm writing an exploration paper on time dilation, specifically gravitational time dilation. One of the scenarios I'm thinking of looking at is the time dilation an ...
3
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1answer
64 views

Ideal shape of a water clock

The ancients undoubtedly discovered the ideal shape of a water clock by trial and error. In examining some ancient water clocks I notice the shape is different depending on the size. For example, a ...
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2answers
109 views

Calculating time from altitude of the sun

If I know the angle between the sun and the horizon, the latitude and longitude of the location, and the day, what equations are needed to calculate the time? I found a website to do it: ...
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0answers
61 views

Does really time exist? [duplicate]

I was wandering whether time really "exists" or is it just a mathematical parameter used to describe how things change.
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1answer
20 views

Time dialation as observed on earth

Probably a silli q but, I wanted to know if someone has taken a wind up clock into space and observed time dialation? If all our observations are by electronic methods, we dont know if ...
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2answers
118 views

Can multiple timelines exist according to theoretical physics? [closed]

Multiple timelines is not a reality yet (as of 2016's science and technology), but exists only in Marvel/DC universe. It is something that is used to explain the paradox of time-travel. If you go back ...
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1answer
84 views

Will physics ever be able to answer the question: “What caused the universe to come into existance”? [closed]

Or is this just the flip side of a metaphysical question "why does the universe not exist", if the opposite was the case and nothing existed i.e. a universe devoid of all energy, matter forces, ...
2
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2answers
81 views

How to describe time-shifts in Noether's theorem in Hamiltonian formalism

As was described in, for example, this post, one can formulate Noether's Theorem also in Hamiltonian Mechanics. Symmetries are then represented by vector fields generated by observables whose Poisson ...
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2answers
51 views

Time dilation and freefall (follow up and simplification) [closed]

A person is four miles up in the atmosphere, and freefalls towards earth. Another person is standing on earth, watching them come down. During this period of freefall, which person experiences more ...
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2answers
50 views

How to interpret irreversibility in time?

I'll quote Feynman's Lectures, chapter 52 (Symmetry in Physical Laws) of volume 1: [...] If we see the egg splattering on the sidewalk and the shell cracking open, and so on, then we will surely ...
0
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0answers
32 views

Is there a fundamental frequency of time? [duplicate]

Our eyes and brains can only perceive frequencies as individual frames up to some limit, after which we perceive the motion to be "continuous." Is there such a frequency of time? Along the same ...
3
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2answers
98 views

How do you think about time as an axis/dimension?

I'm studying mathematics, but (obviously?) have an interest in physics. I've been thinking, how do people in physics think about time as an axis or dimension (as they would be called in mathematics)? ...
2
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3answers
98 views

Is time created by movement through a higher dimensional object? [closed]

In a comment I read on this page, someone mentions a theory where time is created by moving through and slicing "moments" of a higher dimensional object. For analogy, a 2-D creature living on a plane ...
3
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2answers
80 views

Questions regarding the Feynman-Stueckelberg interpretaion

I am studying for an introductory particle physics exam, and I am having some problems with the Feynman-Stueckelberg interpretation of antiparticle states. Background: The course was being thaught ...
4
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0answers
78 views

What determines time flow? (arrow of time) [closed]

I've been reading up on the arrow of time and there is one thing that is being omitted from every explanation that I've found: time flow. I am rewording this question to make it clearer. From the ...
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0answers
34 views

What would you experience if the universe ceased existing whilst you were under extreme time dilation?

Hypothetical situation, if you were in the center of a supermassive black hole (and managed to not be immediately obliterated), time dilation would be so that billions of years may pass outside the ...
1
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1answer
44 views

Can we see ourselves slower due to time relativity?

Please bear with me because I'm noob at physics. Numbers don't have to be calculated, these are just examples, I'm just asking conceptual stuff. Just double check: Objects traveling at $0.99c$ in ...
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2answers
48 views

Question regarding gravity and time

I and my friend (Age 15) were discussing about light and speed of light when we thought of a question. Imagine you are travelling in a spaceship at the speed of 2.9*10^8 m/s circling the earth. ...
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2answers
81 views

Age of universe?

Well relativity teaches us that time interval between two events is a frame dependent quantity, then how can we say that our universe is 13.8 billion years old? Should it not depend on who is asking ...
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1answer
45 views

Reversal of time, an absurd concept? [closed]

Consider a specific case of a hourglass. Here, because of gravity sand flows down and reaches the equilibrium state when all the sand is in the lower half. This way we can keep a measure of time. From ...
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2answers
100 views

Traveling through time, reaching the past - POSSIBLE? [closed]

I was obsessed in studying the "faith" and I've made several great discoveries. I don't want to publish anything yet, but I have a semi-proven (proven partially) / theories / so I am curious on bones. ...
0
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3answers
26 views

Looking at past events by observing sky? [duplicate]

Since solar system (and our galaxy) is constantly in motion at a great speed, is it possible that we can look at our own image as it was sometime ago? Since the light of that age takes sometime to ...
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0answers
29 views

Age difference between hands and feet due to relativity?

According to relativity time passes faster the faster something moves, and gravity slows time. My head is moving faster than my feet (assuming I'm not at one of the poles). My head is further away ...
5
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2answers
161 views

Is there a time operator in quantum mechanics?

The question in the title has been asked many times on this site before, of course. Here's what I found: Time as a Hermitian operator in QM? in 2011. Answer states time is a parameter. Is there an ...
6
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3answers
1k views

Cooling of atomic clocks

I have read of cooling atoms to one-quarter of one-thousandth of a degree above absolutely zero. According to Physicist William Phillips, this improves the measurement of the ticking frequency. I have ...
1
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1answer
104 views

Time Travel: Is it Possible to return to an earlier time? [duplicate]

(Please note: I've seen some other questions asked like the one I myself am asking, I realize that I am indeed late to the party, but I am genuinely curious and none of the previous answers have ...
1
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1answer
79 views

A fast object (0.8c) getting overtaken by another fast object (0.9c): why don't times agree?

I'm trying to work on an exercise in Wolfgang Rindler's book "Introduction to Special Relativity" and I'm stuck on the following exercise: Two particles move along the x-axis of S at velocities ...