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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Deriving Time from Acceleration, Displacement, and Initial Velocity

I know the equation for displacement as a function of time is $$\vec{s} = \vec{v_i} \Delta{t}+\frac{1}{2}\vec{a}\,(\Delta t)^2$$ I need to solve for $\Delta t$ I'm having problems rearranging to do ...
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3answers
106 views

CPT theorem and annihilation of matter and antimatter after the big bang

Is the hypothesis that antimatter is moving backwards in time compatible with the hypothesis of annihilation of matter and antimatter after the big bang? It is said that the big bang should have ...
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1answer
301 views

Why doesn't light travel instantly? [duplicate]

I've read that the faster you travel in space, the slower you travel in time. And when you reach the speed of light (which we won't be able to) time will stand still. So when light travels at the ...
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1answer
498 views

How much time passed for the passenger traveling with at speed-of-light spaceship? [duplicate]

Let's suppose we have a spaceship with the exact speed of light. If a traveller takes this spaceship to go to proxima centauri (approximately 4 years light away from Earth) and come back, we (as ...
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192 views

Paradox Regarding Time Dilation at the Speed of Light

Consider the following scenario: On earth, I pulse a laser focused at a far away mirror such that the time it takes for the light to reflect off the mirror and arrive back at me is at least a few ...
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1answer
76 views

Muons Internal Clocks and Time Dilation? [closed]

I don't get how time dilation affects the half-life of muons? Time is just a tool that is used by humans how does that affect the internal clocks of elementary particles?
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147 views

Distance travelled in spaceship Newton vs Einstein

If you get in the canonical 1G windowless spaceship and accelerate for 5 years as determined by your trusty wristwatch, then decelerate for 5 years, then decide its time to see where you are would the ...
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234 views

Confusion about time shift in special relativity

I have never really found a way to comfortably comprehend the idea of time shift even though I know its not the hard part of relativity theory. In that light, can someone point out what is wrong or ...
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497 views

Does the Earth's revolution around the Sun affect radioactive decay?

Premises: The radioactivity is either hastened or slowed inside a fast moving aircraft. Speed of fastest aircraft: 3,529.6 km/h. The earth's revolution is: 107278.87 km/h. The earth's ...
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50 views

Time relativity

Lets say that I am on a spaceship moving with the speed of 0,90c and I am looking on my friend who stayed back on earth. My friend is looking on me. From my perspective, my friend is moving 7 times ...
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30 views

On a graph, can the compositions of both the x and y variables involve the unit time?

Time seems to be so fundamental to the calculations that we make, that it seems to be at the core of everything we do. Indeed, this is not just philosophically true, time is very often the x axis, by ...
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53 views

Relationship between gravitational time dilation and energy?

The rate that a stationary clock slows down near a massive object, relative to one far away, can be read off from the Schwartzschild metric: ...
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78 views

A problem on rectilinear motion in a car [closed]

Today, I attempted the third question in the first chapter (Physical Fundamentals of Mechanics) in the book Problems in General Physics by I. E. Irodov. The question goes like this: A car starts ...
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54 views

By what factor would you have to slow down time for water to feel like glass?

I have been told that though glass seems like a solid, it is somehow, in theory, a liquid -- but is just somehow a liquid that is so thick that it appears to be solid. (Of course --- if this premise ...
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1answer
65 views

Time dilation and space time [closed]

I know a little about space time, and I know that space time is adding the time component into the three- dimensional world and creating an abstract universe. But my question is that why time is ...
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1answer
36 views

Observing from a black hole proximity

Suppose that you could get close enough to a black hole that time slowed down significantly for you, and you looked at a giant clock back on earth through a telescope. Would you see the earth clock go ...
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124 views

Understanding gravitational time dilation / Schwarzschild metric

I've had a look at the answers to these sorts of questions already, but feel like I'm still missing something. Starting with this question, and this one and even this one here. I'm looking at this ...
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2answers
63 views

Movement of accelerating points with maximum speed (i.e. running away from tiger) [closed]

I'm walking through a forest and suddenly I see a tiger. And now I have a problem. I want to know how much time I have left but I don't know how to calculate it. Or more formally: Let's ...
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2answers
55 views

What is the correct way to treat operators that has “time” in QM? [duplicate]

I don't know if this question has already been resolved but considering that $i\hbar\partial_t$ is the energy operator, and $\partial^2_t$ is the waves operator (or helmholtz), I can't accept that $t$ ...
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1answer
79 views

What are the effects of increased mass on persons traveling at near light speed?

It's been a long time since I studied physics (and then only very superficially), so please bear with my gross naivete. This question's been running around in my head for about two weeks now, and I ...
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1answer
59 views

How to build a clock? [closed]

You have unreliable clocks that fire in the interval $(t,t+\delta)$ with probability density $f(t;\lambda)=\lambda\exp(-\lambda x)$. How will you build the best clock using these unreliable components ...
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4answers
279 views

Relationship between Energy and Time [closed]

Is there a relationship between energy and time? What is it?
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3answers
94 views

Why there is added a partial time derivative in formula for time derivative of potential energy? [duplicate]

In proving the total energy in conservative field is constant we have this equation(picture) why it added partial derivative? Why? I mean where it did come from?
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112 views

Is proper time an intrinsic value of Minkowski space?

What is proper time? Is it a part of Minkowski space (that is a mere spacetime interval)? Or is it an intrinsic characteristic of massive particles (a sort of "aging")? Example: In the following ...
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4answers
124 views

Would infinite time elapse relative to an outside observer if an object was completely at rest?

Here's my reasoning... time dilation due to velocity: t'=t√(1-v^2) v expressed as a % of the speed of light. If you are moving through distance at the speed of light, to an observer at rest relative ...
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1answer
174 views

Is there no fourth dimension (time) in the universe? [closed]

In this article (and numerous others) http://phys.org/news/2011-04-scientists-spacetime-dimension.html and http://www.rebelscience.org/Crackpots/notorious.htm they suggest that there is no time ...
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77 views

Twin Paradox: Whose time is slow? [closed]

What I understand about the twin paradox is that if a person stays at rest with something lets say the earth and a traveller moves with a great velocity with respect to the firsy person, then the time ...
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3answers
97 views

How can a clock work if the uncertainty principle is true?

If the uncertainty principle and Copenhagen Interpretation are true, then how can a clock tick? Supposedly particles can do all sorts of things when not measured, then how can they be formed into ...
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1answer
116 views

Will we gain some extra hours if we travel in the direction of the rotation of the earth? [closed]

I heard that If we travel for long distances in the direction of the rotation of the earth, we can gain some extra hours in the journey. Is it true? What if we travel in the opposite direction?
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1answer
360 views

If time travel to the past is not possible why is this situation considered in Feynman diagrams?

I recently read R.P Feynman's QED:A Strange Theory of Light and Matter. It is believed that time travel to the past is not possible. Then why is particles going backward in time considered in the book ...
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1answer
106 views

Does time pass fastest in isolated, resting space?

While it is fairly established that both fast movement and the presence of gravity make time pass slower as compared to a system at rest / free of gravity, does that mean that there is no way for time ...
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1answer
382 views

Time travel, is it possible? [duplicate]

I see there are many questions with this title, but this one is different, so please give it due thought: Is time travel possible? If so, Can we go both forwards and backwards in time? Paradox: I ...
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1answer
65 views

Could it be a limit in our measuring the speed of photon, instead of photon having a speed?

Are we (not) limited by our own speed through time (1 sec / sec) to measure highest possible speeds(c)? I fire a laser which hits a mirror and comes back and I precisely measure the time, and knowing ...
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1answer
116 views

I heard that at quantum level the past-present-future is not in order, is this true? Is time really messed up there?

I heard that at Quantum level events can happen out of order making causality invalid. Thus the future can happen in present and the present in the future. Is this true?
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1answer
109 views

How do we know that time and distance are not discrete?

I know that it is believed that energy is discrete, in that it travels in quanta. I was wondering if there is any evidence which either proves or disproves something similar with both time and ...
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1answer
261 views

Time Dilation in relation to Acceleration

What I am looking for is a layman's explanation on the equations required to work out Time Dilation at high speeds including acceleration and deceleration of velocity. Or I would greatly appreciate it ...
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1answer
182 views

Does photon possesses no time to cover any arbitrary distance?

Photon travel 8 minutes (with speed $c$) from the sun to reach the earth. Any particle (or space-ship) with velocity $0.99 c$ covers the same distance (93 millions km) within less than 2 minutes ...
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1answer
303 views

Approximate Time Dilation at Rocket Speeds

How do you calculate the time dilation effect experienced by a traveler traveling at a relatively low speed? Specifically, how much time dilation would a traveller moving at $v=0.0007 c$ (speed of ...
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1answer
203 views

Red shift and time distortion

Superman throws a light emitting object away from himself fast enough to notice a red-shift. The object passes through a region in which time runs more slowly. From Superman's perspective, does the ...
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2answers
92 views

Resources for current thought on time/spacetime?

Are any of the big-name physicists associated with the time in the same way that Hawking and Penrose are associated with black holes? I'm interested in some good books that focus on the topic.
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200 views

Is relativistic motion equivalent to fluctuating gravitational fields?

The theory of relativity makes very precise predictions about how an object's motion through space-time affects the passage of time for both the object and observers in other frames of reference. I ...
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1answer
524 views

When are we now? Time coordinate system [closed]

The Second and the metre are well defined. We have those units available. Of course units are meant to express measurement, tools to compare with precision, and interchange that information ...
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1answer
39 views

What is the difference between the expansion of space and the Alcubierre drive?

The Alcubierre drive violates causality. As far as I know the expansion of space does not. The usual explanation for why space is allowed to go FTL is that the matter doesn't move. The Alcubierre ...
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1answer
66 views

With respect to what does time itself change? [duplicate]

We all have an intuitive notion that time itself "changes" - before it was the past, now it is the present, later it will be the future, and as time "changes" or moves forward what was the present ...
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3answers
130 views

If time is relative, how could time pass? [duplicate]

EDIT: I appreciate people who answered below. But it does not answer the question, so I will clarify my questions: -It seems like everyone is saying that time passing is actualized by physical ...
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1answer
1k views

Does the universe update time in some finite interval? [duplicate]

I was listening to a lecture by leonard susskind and one of the analogies he used was a coin having two states and he "broke" time into intervals. He continued to say that at each interval of time, if ...
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1answer
74 views

Calculate Time travel with Time Dilation [closed]

Does the following hold: If we have: person A moving at a speed of $0$; person B moving at a speed of $xC$ (where $C$ is speed of light, $x$ a fraction) And if time passes for $m$ ...
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1answer
55 views

Is gravitation time dilation simply c/v?

Recently, I've been very interested in forms of time dilation. I'm relatively new to relativity, so I apologize for any stupid mistake I may make. I was messing with the equation for gravitational ...
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1answer
56 views

Has the effect of magnetic fields on time ever been examined experimentally?

Relativity of time can be examined with satellites as gravitational or acceleration. Is there any similar experiment with intense magnetic fields?
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134 views

Naked Time ( Is there such a thing ?) [closed]

I have lately been concerned with time and whether or not it is an illusion. For argument's sake let's assume it is. Then time should stand on its own. Can anyone describe, (or point me to a paper ...