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

learn more… | top users | synonyms (2)

-1
votes
0answers
14 views

What does gravitational lensing equal in time diolation to gravity?

How close does a person need to get in a black hole in orbit to get 2x speed in time and what would that equal in g force?
-3
votes
0answers
45 views

Twin paradox without gravity [on hold]

Suppose we have 3 people Person1 was already born on a spaceship that travels in the speed of 0.5c toward person2 Person2 was born in a point in point in the space also in the exact time of person1 ...
2
votes
1answer
58 views

Is the age of the Universe relative to where you are within it? [duplicate]

The accepted age of the Universe is 13 billion years give or take. If you were a super space being and hypothetically had spent a large portion of this time sitting next to a black hole then your ...
-1
votes
0answers
32 views

How to find the Average Speed in this question? [on hold]

If the average speed of a spaceship is 32,000 km/h, how long would it take to travel the 80 million km from Earth to Mars? I applied the S = D / T Formula and got 0.0004 h Because this is a ...
0
votes
1answer
44 views

Is this possible to create a 1D or 2D thing in real? [on hold]

We are living in the fourth dimension(time).So we can now travel through the third dimension. Now just imagine to make a 1 dimension thing, A line in real world. If I draw a line in paper with a ...
-1
votes
2answers
31 views

Lagrangian mechanics not relying on time or independent of time [on hold]

If neither the potential energy nor kinetic energy depends on time, then Lagrangian is explicitly independent of time I find this statement a little bit odd because velocity is distance over time or ...
-1
votes
1answer
21 views

Water Boiling Time Calculator

Is there a way to calculate out how quickly a body of water will boil? My primary concern is to measure in relationship to different temperatures. For example, heat at 100 degrees Fahrenheit versus ...
0
votes
0answers
76 views

What would a universe with 2 time dimensions be like? [duplicate]

In a universe with 2 dimensions of time, and 3 spatial dimensions, the equation for finding the change in time is: $\Delta T= \sqrt{(\Delta \alpha_1)^2+(\Delta \alpha_2)^2} \geq 0$ Where $T$ is the ...
-7
votes
1answer
50 views

About Time - Its Direction, dimensions, light cones, effect of gravitation on time [closed]

Does time have a center? Maybe a point where past, present, & future interchange?
3
votes
1answer
86 views

Is there any Hamiltonian that contains time derivative? [duplicate]

Quantum mechanics is governed by Schrodinger's equation: $$\hat{H}\psi=i\hbar\partial_t \psi$$ It seems that Hamiltonian acts on wave functions like a time derivative. Just out of curiosity, is ...
0
votes
1answer
53 views

What is Hawking's, “No Boundary Conditions”? [closed]

In his "No Boundary Conditions", is Hawking stating that time is eternal? And what is the difference between Real Time and Imaginary Time? Is he saying there are two different arrows of time, and ...
-1
votes
0answers
37 views

Gravitational time distorting waves [duplicate]

I have got a very interesting question to ask: We receive not only a space distortion (what LIGO has measured) but also a time distortion. I can just imagine how would it look like a time distortion ...
23
votes
3answers
2k views

Is there an actual proof for the energy-time Uncertainty Principle?

As I understand, the energy-time uncertainty principle can't be derived from the generalized uncertainty relation. This is because time is a dynamical variable and not an observable in the same sense ...
-4
votes
3answers
81 views

How can time be a dimension when it is relative? [closed]

I understand that by definition dimension is defined by just another coordinate to pin-point something in space-time. Therefore we need to know not only where but when. At the same time, this somehow ...
-4
votes
3answers
81 views

Is “time” a singular dimension or multiple dimensions? [closed]

We know of x, y, and z dimensions. We also know of "time"... Another dimension we are aware of, which is a "non-physical dimension" called a "temporal dimension". Now, we all look at "time" as a "...
2
votes
1answer
34 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 ...
1
vote
1answer
41 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
votes
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
votes
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 ...
-3
votes
1answer
97 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
vote
1answer
90 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
votes
4answers
170 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 \dfrac{d|\psi(t)\rangle}{dt}=H|\...
0
votes
3answers
118 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 they ...
-1
votes
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
votes
0answers
25 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
vote
1answer
43 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
votes
1answer
61 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
votes
2answers
69 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
votes
0answers
29 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
votes
0answers
21 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
votes
1answer
71 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
votes
1answer
108 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
403 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
votes
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, ...
-4
votes
1answer
62 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
votes
1answer
58 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
votes
1answer
23 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
votes
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
192 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
vote
2answers
96 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
votes
0answers
107 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
vote
2answers
58 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. $\frac{d\vec{v}}{dt}=\frac{d\vec{v'}}{dt}...
2
votes
2answers
49 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 ...
-9
votes
2answers
193 views

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

The Help Center recommends I 'fix' this question: (original question) "It seems self-evident that everything exist in the Now. Notwithstanding time-dilation and different rates of the passage of ...
20
votes
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
vote
3answers
125 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
75 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
vote
1answer
154 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
votes
1answer
57 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, ...