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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Estimating the present state of stars [duplicate]

Many time while reading through astronomy articles on the stars most of then thousand of light years away from earth. I have wondered how do astronomer know about the present state of star if we are ...
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34 views

What is the formula for calculating the length of any given day (sunrise to sunset)? [duplicate]

In a specific date what law gives us perfect measurements and how will we measure if latitude is given?
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2answers
86 views

How was time defined before we knew the speed of light was constant or in classical physics? [closed]

Nowadays, we now about $c$ the universal speed of light. This lets us define the notion of distance in terms of time (despite the fact that it works the opposite way for our common units.) Before ...
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1answer
71 views

How do we presently understand time?

How do we presently understand time? Can a second be related directly to physical phenomena? What is a second really? Why are we sure that time is linear?
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2answers
161 views

How could mass exist before Big Bang?

I heard that before Big Bang the temperatures were so high that mass and energy constantly converted to each other. After big bang the temperature became less and the conversion stopped that is what ...
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3answers
246 views

According to relativity, can a statement be true and false in same time?

Say I write following statement on a paper: It's year 2014 at earth. Then I give it to my friend. My friend then starts to leave me and earth to outside with velocity of light. Einstein says the ...
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2answers
76 views

are clocks always wrong? [on hold]

So I was sitting thinking earlier and I remembered an experiment that I heard a couple days back about how scientists put a stop watch on a jet and it had a different time then one on earth because ...
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2answers
49 views

Relativity asymmetry?

If you have two bodies that move towards each other at a constant velocity, each body will observe the other body experience time faster. This does not make sense to me because if you had a person ...
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1answer
73 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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1answer
166 views

US time zones and Daylight saving time, energy efficient? [closed]

As a foreigner, United States has a very complex time system for me. Central Time Zone, North American Eastern Time Zone, ...
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1answer
149 views

Determine the distance from time-velocity graph [duplicate]

A small car that we made in class was travelling and its time was recorded at 1,2,3, and 4 meters. The points in the form (seconds, meters) are as follows: ...
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2answers
129 views

Backward Time Flow?

Physicists say that time is moving foward because entropy always increases. But have physicists considered that we might be mistaken? Since there is no ultimate reference frame, it could be possible ...
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1answer
75 views

Is the universe we know just shaped due to time? [closed]

Call me a daydreamer, but I could not stop myself for asking this question. I was idle when something ticked me and struck my head. I was thinking about universe, speed of light, and how time works. ...
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1answer
205 views

Calculate time to go from one point to another point [closed]

in a 2D football game I want to calculate cycle(time) until ball go from one point to another point. in this link exist all fomulas that we need for my problem but anyone does not have any parameter ...
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1answer
73 views

Does the movement of things in the universe will cease one day?

To start or change the movement, we need a force. This force, according to Newton's second law, is variation of quantity of motion from the object per unit of time.Therefore, if the variation does not ...
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1answer
227 views

length, width, and time

is it possible to have length, width and time. A 2D or 1D object with the 4th dimension (although then there would not be 4 dimensions so would it b 3D?) .
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0answers
46 views

Is there an absolute scale of time?

If two rockets depart from planets A and B in order to visit the respective planet which is moving relative to the one from which it departs. And then return home to compare clocks on their home ...
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2answers
135 views

Proof that time exists [duplicate]

Is time just an axiom? Or can it be proven to exist? Correct me if I'm wrong, but our whole understanding of the universe is based on directly observing the world and building out axioms that are ...
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1answer
874 views

Why does time dilation cause you to age slower? And is time considered relative to the observer?

I understand that the higher your velocity the slower light will move. But how does time itself slow down while you are moving faster?
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2answers
145 views

I understand the Big Bang Theory (BBT), but how was the matter in the BBT created?

I understand the Big Bang Theory to consist of all of the matter being pulled into one great gravitational pull. such a great force that it expelled the matter out causing the idea of Red-Shift and ...
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1answer
126 views

General Relativity and Time Dilation [duplicate]

Is time affected by the gravitational force? If so, what might be the effect on time at the centre or near centre of earth ?
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1answer
561 views

How do photons experience time? [duplicate]

I know that as velocity approaches the speed of light the time dilation shoots to infinity as shown below. 1)So I want to know how time is perceived from the point of view of the photon? 2)Since ...
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1answer
113 views

Existence of time in some other universe [closed]

Is it necessary that time should exist in another universe if it (universe) is there? How do we perceive timelessness?
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4answers
1k views

Relativity in Real Life

I have no formal training at all in relativity. But I was just wondering if our perception of time is altered by different events. Here are some examples I had in mind: If I touch a stove for 10 ...
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5answers
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2 balls falling hit the ground at the same time

There are 2 balls in a vacuum, next to each other but not touch. They are on the edge of a surface they will both leave the table at exactly the same time. One gets pushed harder than the other. The ...
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3answers
269 views

How can we be sure about the constancy of atomic clocks as in the Hafele and Keating time dilation test?

Atomic clocks were used in Hafele and Keatings experiment which supposedly helped to prove time dilation. Time Dilation Proof - Hafele and Keating How can we be sure other forces didn't act upon the ...
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2answers
298 views

Gravity vs. Velocity Time Dilation [closed]

Can some one give me the unified formula for Gravity Time Dilation and Velocity Time Dilation.
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3answers
1k views

How does Time traveling work in practice?

There are multiple theories about time traveling. One is "proven": The time slows down according to your speed. The satellites in space are traveling faster than us, thus their clocks slows down a ...
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1answer
119 views

Quantum entanglement and special relativity PARADOX

Imagine two entangled atomic clocks. After we entangle them, we measure the time: it does has to be the same , right ? Now lets suppose that we entangle them , but don't measure them, then we plant ...
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3answers
177 views

Is it possible to defy time using speed? [closed]

I have always wondered if we were to travel at past the speed of light (even beyond the current capability) would we be able to slow down time around us? I have asked my teacher at school and he has ...
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1answer
779 views

What is the difference between UT0, UT1 and GMT time?

Every reference I find says that they are "essentially" the same, which we all know really means that they are not the same, but different only by a some small amount that someone else other than me ...
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1answer
141 views

The time is a type of energy ?

You know energy is necessary for the occurrence of an event . Time is also exactly neccessary for the occurrence of an event. If there is no time , there will be no event. I mean time is a type of ...
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1answer
172 views

Could time be changing without us knowing? [closed]

I've been wondering about relativity for a while now. We seem to measure time by using the speed of light. Light can be slowed down or stopped We assume light doesn't change in a vacuum - yet, how ...
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1answer
24 views

Find Distance with Acceleration and Time

I'm working on Physics homework and have run into a problem I can't figure out. Any help would be much appreciated! Problem: Allison exerts a steady net force of 50N on a 22-kg shopping cart ...
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1answer
76 views

Gravitational Time Dilation Formula? [closed]

What is the equation for calculating the dilation of time at different levels of gravitational force?
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1answer
84 views

What is the formula for determining time dilation (as the object in motion)? [duplicate]

The formula for calculating how much time passes for a still observer is T=TO/(1-v^2/c^2)^1/2. How do I calculate what TO is?
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1answer
96 views

attaining the speed of light?? [duplicate]

WHY our time would run slow if we move with the speed close or equal to the speed of light, and is that time dilation restricted to only just '' time' ' or it affects our biological time also (does ...
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1answer
43 views

How to find time taken for a spinning top to stop? [closed]

The angular position of a spinning top is given by $\theta = t^3 - 72t$, where $t$ is in seconds and $\theta$ in "radian".
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1answer
59 views

Problem related in relative motion [closed]

The speed of a boat is 1.5 m/s in still water. One needs to cross a river of width 500 m with this boat. Along the direction of the river a strong wind is blowing with a speed of 0.9 m/s. The boat is ...
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2answers
800 views

Why does time slow down when traveling at high speeds [duplicate]

One of the effects of traveling at high speeds is slowing down of clocks. I can understand gravity time dilation effect but not how would velocity affect clock speeds. How correct it is, if I say ...
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1answer
117 views

Why is it legitimate to only observe motion, but call it time, such that concepts like “the relativity of simultaneity” are seen as possibly genuine? [duplicate]

My question is asking for evaluation of a new concept or paradigm within the framework of the current mainstream physics understanding of Relativity. Specifically, that concept or paradigm being that, ...
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3answers
128 views

Can it be considered as time travel?

India is about 8.5 hours ahead of US. If some person starts from India at 9 pm(according to his wrist watch) and reaches US in 2 hours(just assume),at that time his wrist watch will b showing 11 pm ...
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1answer
93 views

Displacement inside the moving Object

Suppose say a person is standing over the moving bike and he jumps while bike is moving, bike will move forward & person will land in same point at which he jumped, relative to earth position ...
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1answer
136 views

Combined speed of Earth in Space is 1.5 million mph - how much slower is time for Earthlings as a result?

Theres a problem for intergalactic astronauts which is finding their way back to Earth. Combining all the rotational speeds, we are spinning and orbiting the sun, in our solar system which is spinning ...
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2answers
272 views

Why do we feel the passing of time?

Why do we feel the passing of time? Why do we feel the time is changing with increasing speed $d\tau=\gamma^{-1}dt$? In other word why Lorentz factor (or scientifically relativistic velocity function ...
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3answers
177 views

Is Space conserved [closed]

Can space be created or destroyed? Is space conserved? I am not asking for matter,energy and time. Its just a question about conservation of space PS: I am asking for what was there before big bang. ...
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3answers
2k views

How accurate is the time on a digital clock versus the time on internet clocks? [closed]

How accurate is the time on a digital clock versus the time on internet clocks? The internet clocks seem slower than internet clocks. So which is the correct time? What are the most accurate clocks?
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2answers
291 views

Is this a great flaw in big bang theory? [duplicate]

Einstein said that, Time & Space cannot exists without one another. Big bang says, time didn't exist before the big bang. So the Primordial ball referred in the Big Bang theory didn't had any ...
-4
votes
3answers
228 views

How could we define speed without time?

This is a bit of a brain twister but it's a very serious question. Please be precise in your answer. I do not believe time exists. I believe it is simply an illusion of our perception, the ...
-4
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1answer
281 views

Does time really exist? [duplicate]

Does time really exist? or is it a human invention and convention? What is the truth? are there time particles? please remember, I'm looking for constructive answers, not condescending and void ones.