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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17 views

Why capacitor charging is taken from negative infinity?

Why in Engineering disciplines, when finding voltage across capacitor the time as limit of integral is taken from negative infinity to $t$ and not zero? The same can be seen for signals, Laplace ...
0
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0answers
44 views

Has Rovelli proven that time doesn't exist? [on hold]

Has Rovelli proven that time doesn't exist? See this paper on the Arxiv for a description of his ideas. I am reading some people argue at length, and inauspiciously, that he has. I am entirely ...
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0answers
35 views

Are we approaching Bremermann's Limit, or running from it? [on hold]

Is computational density increasing, or decreasing? Or, more generally, is the computational density of a given region of space know to strictly to increase with time? (Is it linked with entropy and ...
2
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1answer
30 views

Is Entropy Maximized, or Just Increased?

Do different real processes involve different rates of change of entropy? (Is the rate of change of entropy constant with time throughout all regions of space, or perhaps in other words, constant with ...
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0answers
29 views

What is the speed of time between bodies? [on hold]

I'm guessing the speed of time is 1 sec per sec on the surface of earth? If so, what is the speed of time on the surface of the sun? What is the speed of time 100,000 miles off the surface of earth? ...
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0answers
164 views

Is the “time remnant” theory (explained in The Flash Tv Series) a real theory? [closed]

I don't know if someone of you does follow the Tv Series: THE FLASH, but since sometimes some fascinating physical theory jumps out, I thought that would have been the rightest place in which to ask ...
1
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1answer
40 views

Reference for Reichenbach synchronisation and non-standard special relativity

My professor introduced in the last lesson a new method for clock synchronisation, which he called "Reichenbach synchronisation". In this new method, two clock A and B synchronise themself with the ...
0
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0answers
25 views

Does photon experience time? [duplicate]

According to the special theory of relativity, for all observers the speed of light is c. Any observer travelling at the speed of light c does not experience time. Hence even protons shouldn't ...
0
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0answers
7 views

Power scaling behavior in Detrended Fluctuation Analysis

I am trying to apply DFA in my time-series, however, remain the the determination linear relationship of the log fluctuation vs. log scale plot i.e. slope which indicates to the power scaling behavior ...
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1answer
95 views

Calculating speed in four dimensions [closed]

If you are moving at $c$ in 3D space and $c$ in time axis too, What would be your total speed? Edit: Since question has been voted to be closed, I shall make an Edit. In 4D world all objects move ...
1
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1answer
89 views

Period of a pendulum [closed]

In the book 'Calculus the Early Transcendetals' at page 776 (7th edition) they give that the period of a pendulum with length $\text{L}$ that makes a maximum angle $\theta_0$ with the vertical is: ...
4
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4answers
162 views

Is time an observable in Relativistic Quantum Mechanics?

Relativistic Quantum Mechanic is based, as far as I know, in the Dirac Equation. Now, the Schrödinger equation, in the abstract state space takes the form: $$i\hbar ...
0
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3answers
83 views

What does it mean that the laws of physics are time reversible?

The Universe, as far as we can tell, only operates according to laws of physics. And just about all of the laws of physics that we know are completely time-reversible, meaning that the things ...
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1answer
27 views

Is the time for light to go a certain distance the same amount of time sped up through relativity?

If you were to stand on the tower of my Lemmon and had an atomic clock that was exactly synchronized with one at tucson, (6734 feet difference) for 24 hours, it was shown to be roughly a 20 nano ...
0
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0answers
23 views

Special Relativity and its relation to refractive index [duplicate]

As is known, light slows down (compared to vacuum) whenever it enters a medium. Also, Special Relativity effectively puts a limit on the max. speed of any body. So is it possible for a body (in a ...
1
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1answer
41 views

Traveling slower by traveling in opposite direction as the Earth rotates

I know that if I were to travel fast, the time would pass by fast for me. But if I were to travel fast in the opposite direction of the earths rotation while I'm still on earth, would the time pass by ...
0
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1answer
49 views

How does pressure change over time in an open box?

Imagine that you have a 1 cubic meter metal box with two 20 mm diameter holes. One of them is connected to an air-compressor that constantly pressurizes the inside of cube. Let's say 5 atm. The other ...
0
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2answers
66 views

Is time a coordinate or a parameter in Newtonian mechanics?

In classical (Newtonian) mechanics we only ever seem to consider 3-dimensional space, with physical quantities being represented by 3-vectors. My understanding for this is because in classical ...
0
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0answers
26 views

How much time a ball stays at rest when throw up?

You throw a ball straight up in the air. The ball attains its maximum height when it is momentarily at rest,(v=0). How mutch time is this moment? If we take time has continuous it is an infinitesimal ...
0
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0answers
19 views

Are there any specific examples of the application of Lewis-Riesenfeld procedure to time dependent Hamiltonians in QM?

Lewis-Riesenfeld invariant theory is a theory applicable to solve time-dependent Schrodinger equations. I have always encountered the theory related to the procedure, however never encountered any ...
0
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1answer
45 views

What is the best way to calculate impact time with collisions?

I've been teaching myself physics and I've been wondering about the impact time in collision calculations. The scenario I've been using to learn is an object with a mass of 4000 kilograms colliding ...
0
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1answer
102 views

How can Big Bang happen without time?

I had recently watched a video and he says big bang could have happen by the slow collision rather than a fast collision. But I know that there was no time before the big bang and fast and slow are ...
2
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2answers
390 views

Stanford: “Objects in spacetime all move at constant speed $c$.” Are they right? [duplicate]

In this Stanford University lecture on Relativity, it is stated: Likewise, objects in spacetime all move at constant speed c in spacetime but if you change its direction, say by moving at speed v in ...
0
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1answer
56 views

Did time also began from big bang?

Did time began from big bang? If not then what existed before big bang? If time had a beginning, then does it have a end, or pause because if time had a pause then we would not have known about it, ...
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1answer
61 views

How time and speed of light are related? [closed]

I want to know how speed and light and time are related? How will motion with highspeed effect time? I am not a physics student. I want an answer which is free of mathematical relations. I want an ...
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1answer
55 views

Equation for everything?

Suppose, I throw a ball and it bounce. If we observe it from the time of it hitting the ground, we can see it moves due to the initial velocity it had and the interaction it had with the ground. We ...
0
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1answer
22 views

What does Time tells about mass of an object? [closed]

According to theory of relativity Time becomes slower in presence of an heavy object. And In theory on concentration it is said when we are in deep concentration our perception of Time changes and it ...
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0answers
44 views

Gravity's effects on time

So, in the movie Interstellar they say that one year by the black hole is about 35 years back on Earth (excuse any lack of accuracy in the numbers, I haven't seen the movie in over a year). Now, the ...
4
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4answers
190 views

Distance in General relativity

I read a few lines about general relativity and one of the first equations is the one defining the eigentime of a time - like curve. But observers should also be able to measure length, right? So is ...
1
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2answers
86 views

Atomic Clocks: How is time measured?

I am trying to understand atomic clocks better. I am not getting HOW the cesium oscillation is actually being counted. So from my understanding of an older atomic clock: cesium gets heated-> ...
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0answers
77 views

Calculating travel time based on distance, velocities, acceleration, and jerk

Not much physics background so please bare with me. Say we have an object traveling on a straight line going from x to y. We know the starting velocity at x, the velocity when y is reached, the max ...
1
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2answers
43 views

Infinitesimal time intervals use

I've a question, that maybe will sound obvious, on the use of infinitesimal quantities. Consider the expression for the acceleration in non inertial frames. ...
2
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2answers
46 views

Can only one now imply every future? [closed]

In logic, A implies B, if B is always true in instances where A is true. Obviously, there can only be one possible future, for every potential now, that is, in all instances where a certain now is ...
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2answers
172 views

Presentism: doesn't everything exist at the same moment? [closed]

It seems self-evident that everything exist in the Now. Notwithstanding time-dilation and different rates of the passage of time and entropy, doesn't this all still happen in the same universal ...
20
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3answers
9k views

Oh-my-god particle: How can it get through Milky way in 10 seconds?

My question is concerning wikipedia article on Oh-my-God particle, to be precise, this paragraph: This particle had so much kinetic energy it was travelling at 99.99999999999999999999951% the ...
1
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3answers
121 views

What would happen if you went back in time to get a random number?

For example, you go to a website that generates a random number. You get the number 8. What would happen if you went back in time a few minutes, and repeated the same actions. Would you get the same ...
2
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2answers
106 views

Is acceleration relative in relativity?

Suppose a box A is moving relative to a Box B, then by time dilation equation if I take 1 sec passed for an observer in A then for an observer in B will be little longer. Now if I suppose that the box ...
2
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0answers
70 views

Should we consider space and time as separate entity?

In general relativity, we think of space and time in spacetime framework. As some people say, metric tensor sign difference, along with our inability to go backward in time suggests that space and ...
1
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1answer
135 views

Does antimatter travel faster than light

I have read in the answers here that an electron traveling backwards in time would behave as a positron. I also read in another there that antimatter is matter traveling backwards in time As far as I ...
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1answer
55 views

How to measure size of x in time (“time thickness” and not “lifetime”)? [closed]

My question is a consequence of a personnal hypothesis which might be wrong. Everything which exists has a size mesurable in 3D space with different size of rulers. This stands for any particle, ...
0
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0answers
35 views

Time. Is it really a dimension? [duplicate]

I have trouble accepting that time is a dimension, in the same way that space has three dimensions. Wherever there is space and matter, it has spatial properties. You can move back and forwards in ...
0
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1answer
174 views

Does Inertial time dilation demonstrate that Time is not a dimension? [duplicate]

If time is a dimension and 'now' simply an expression of your position with respect to that dimension, the progress of any object along that dimension should remain in step with all other objects. By ...
2
votes
3answers
71 views

Can the passage of time be measured in the absence of motion? [duplicate]

All of the ways I have heard of to measure the passage of time involve measuring some sort of motion (e.g. vibrations of a cesium atom, movement of the hands on a clock, etc.). Can the passage of ...
-1
votes
1answer
27 views

Is there any naturally occurring light wave with a constant frequency that has a terminable decimal. [closed]

I was wanting to think of a natural unit of time, if one exists, that is known exactly. I started thinking about it with the Voyager plaque and the 21 cm Hydrogen line (HL). When I looked into the HL, ...
0
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3answers
145 views

Is time unidirectional because of 4th spatial dimension? [closed]

We heard about an expanding universe. Consider an expanding sphere. Consider the surface of the sphere as our 3 dimensional universe. Can time dimension be the radius $R$ of this sphere? And because ...
0
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2answers
50 views

How Can a Singularity contain different things? [closed]

According to the Big Bang model, space and everything in it was squeezed into a infinitely small point which subsequently expanded. But if everything is squeezed into a point of zero size than there ...
1
vote
1answer
59 views

Does travelling towards something at relativistic speed cause it to appear to speed up?

If one were to travel towards a giant TV floating in space, at a fraction of the speed of light, would a video playing on the TV appear to play faster? I'm guessing the answer is no. From what I ...
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votes
1answer
80 views

Explaining The Quantum Mechanics Weirdness [closed]

Academic replies only; I would like feedback on this, so yes i am asking you to poke holes in it, it is about explaining the time weirdness of quantum mechanics and how particles behave. When the ...
1
vote
1answer
40 views

Scientific definitions of “moment (of)” and “instant”? [closed]

What are the scientific definitions of "moment (of time)" and "instant"? Are they different with their definitions in everyday language? I also don't know the definitions in everyday language, of ...
42
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3answers
8k views

Why is second the duration of exactly 9192631770 periods of radiations?

Why is a second equal to the duration of 9192631770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the caesium-133 atom? Why is the number of ...