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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2answers
60 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 ...
-1
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0answers
24 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
16 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 ...
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1answer
30 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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0answers
75 views

How does time get on our clocks? [closed]

I am referring to the theories of timelessness of the universe. I would like to know if these theories have an explanation how finally something can be read on our clocks which is strongly resembling ...
-1
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0answers
51 views

Relativity of time in regard to speed of light [closed]

Someone stated that if you go on a train for 1 year going 99.999999999% the speed of light 233 year would have passed to those outside the train due to time dilation. So what speed do we perceive time ...
0
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1answer
87 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
votes
2answers
369 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
49 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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2answers
58 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 ...
-1
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0answers
21 views

Deterministic universe vs Law of Conservation of information

Simply put Can Law of Conservation of information hold along side presence of truly random events in the universe? Say for example if event of a particle decay is a really truly random process which ...
-3
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0answers
24 views

What's the consensus on the block universe? Is time frozen? [duplicate]

What's the consensus view on the block universe? Is time frozen? Do the past and future exist? Was Einstein right when he said, “People like us, who believe in physics, know that the distinction ...
-1
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1answer
54 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 ...
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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 ...
0
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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
votes
4answers
189 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
78 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-> ...
0
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0answers
51 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 ...
0
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1answer
29 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
45 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
159 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 ...
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2answers
144 views

Einstein wrote $x^4=ict$, where $c$ is the speed of light. Does this mean the fourth dimension is moving? [closed]

Saw this on a forum: Einstein wrote$x^4=ict$, where $c$ is the speed of light. Does this mean the fourth dimension is moving? We can write $x^4=ict$ as $dx^4/dt =ic$. The fourth dimensions is thus ...
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
120 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
votes
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
votes
0answers
62 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
112 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 ...
0
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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
votes
1answer
161 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
63 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
votes
3answers
140 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
48 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
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1answer
58 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 ...
-8
votes
1answer
78 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
36 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 ...
41
votes
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 ...
1
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0answers
28 views

Can Medium Density Slows down the Time? - Light [closed]

fact : "Light get slow down while travel through Glass (dense medium), when escape glass (dense medium) it get speed up" Isn't above situation is an open example time get slowed down for light ...
0
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0answers
40 views

complete layman trying to understand time relativity [duplicate]

I am trying to understand intuitively why time slows down as speed increases. I have watched many pseudo-documentaries explaining the concept, but I cannot get at the core of the explanation. The ...
4
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0answers
42 views

What ticks in an optical clock?

After reading several articles about current state of the art clocks, I'm still wondering one thing: What ticks? As I understand it, in cesium clocks time is measured in cycles of a microwave ...
2
votes
3answers
116 views

Can there be motion without the flowing of time? [closed]

tldr - Can we reject the notion of the passage of time, but still accept that motion is real? This question is a follow up to comments between myself and the author of this answer to the question, ...
33
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6answers
4k views

What is the proper way to explain the twin paradox?

The paradox in the twin paradox is that the situation appears symmetrical so each twin should think the other has aged less, which is of course impossible. There are a thousand explanations out there ...
0
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1answer
55 views

What dictates the rate in which time passes? [closed]

I understand that special relativity tells us that our perception of the passage of time can change depending on reference frames. But why does time pass the rate at which it does in my reference ...
0
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2answers
78 views
-1
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3answers
88 views

How time dilation happens by velocity?

i got many explanation and proving that relative velocity causes time dilation. Einstein's moving light experiment proves it. but that is a clock works with light detector. as detecting the light gets ...
3
votes
1answer
53 views

Is time a vector in Minkowski space? [duplicate]

I am arguing about this topic with my school teacher in so long time, I want to finish this debate. My teacher's opinion is "Yes, Time is vector" because four-vector has $t$ component, and mine is ...
1
vote
0answers
22 views

Time in the early universe [duplicate]

When it is said, for example, that grand unification took place "Between 10−43 second and 10−36 second after the Big Bang", how are these figures of time derived? Moreover, do these figures have any ...
1
vote
2answers
96 views

Three questions about time [closed]

Since I don't want to abuse to the ASK QUESTION form, and since those questions are all about time, I decided to write them all here. Hope it's ok. First Question Could it be possible (how?) to ...
0
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1answer
58 views

Does time and time dilation exist in a black hole?

Since being near stronger gravitational fields causes time dilation, can this be generalized to the region beyond the event horizon? i.e , is it meaningful to say that someone outside the black hole ...