Time Definition and 1000 Threads

For example, things are caused by things, things move or don't move, there are big movements and small movements.

According to the General Theory of Relativity, time does not pass on a black hole, which means that processes they don't work either. As the object becomes heavier, the speed of matter falling on it for an observer on Earth will first increase, and then slow down, due to the effect of time...

If we don't multiply time by the speed of light C, in Lorentz transformation equatins, the invariant tensor of U.U will not be equal to c^2. So it seems the coefficient of C is an obligation for parameter t. I thought it's just for visual convenience in graphs, besides C is not dimensionless.

Answers to questions like this assume that the quantum state in a Hilbert space is only a function of time, that is ##\partial_i\vert\psi(t)\rangle\neq0## only when the variable ##i## is ##t##. Is this a postulate of standard quantum mechanics, that in Schrödinger's equation the state in...

I was watching a video from Neil DeGrasse Tyson on time travel. He said you can’t travel back in time to meet yourself. Is this correct or am I misunderstanding this? Explanations would be greatly appreciated. I know it’s only a hypothesis, but I was wondering about the answer in terms of the...

Hello, everyone! I’ve been thinking about time and how it’s perceived across different regions of space, and I wanted to share an idea I’ve been considering. As we know, time is relative, particularly when we factor in gravitational fields or objects moving at high velocities. This led me to...

I need help on an idea I have had for the last couple of months. I am not an astrophysicist so I am here to get some direction on whether this makes sense or not. It is well known that the fabric of space can ben bent by the objects in it. Planets and astreoids can only bend the space-time so...

I tried out this free fall calculator, and it says that it would take 4.3 minutes to fall to Earth from 200 miles up. (The altitude of the space shuttle, but no horizontal velocity.) This intuitively seems very fast to me, even assuming no atmosphere. Am I using it wrong? It also gave me a...

I try to figure out how to calculate the proper time between two events for a moving frame of reference. Knowing that the proper time is: ##(d \tau)^2 = \frac{- (ds)^2}{c^2}##, and thus it is the same for all frame of reference. Following This example from wikipedia, we have an observer A who...

If time dilates differently for two observers in relative motion, how is this possible when both observers can claim that it is the other's time that is passing more slowly? Doesn't this create a contradiction? And how does the famous twin paradox explain or complicate this issue?

According to Einstein's relativity, all intertial frame of motion is relative and time is also relative. Let's consider Person A is sitting on a chair and is at rest with respect to surface on Earth and Person B is travelling in 80 percent speed of light with respect to planet Earth and Person C...

Two relativistic spaceships, A & B, are launched simultaneously from Earth towards Kepler 22b, 640 LY away. Ship A is a lighter ship, has no life support as all it carries is some powered-down androids, and it can accelerate at a constant 3g. Ship B is a more massive ship, it carries human crew...

So let me ask a question about the speed of light. Why can't we go faster than the speed of light? I understand the idea with the photon clock — the clock slows down as you move faster because the photon has to travel a longer distance. But theoretically, if we throw a rock at a wall, it would...

We have 2+1 spacetime (x,y,t) and objects a) and b). The velocity of the object a) is greater than the velocity of the object b), so, according to special theory of relativity the time passes for the object a) slower than for object b) (t_2 is greater than t_1). So is the pinned picture correct...

What if we could see the past, not just through history books, but in real-time? Imagine placing a mirror on the Sun, reflecting its light, and using a super-powerful microscope to observe Earth’s past. It sounds like a science fiction dream, but it’s a mind-bending thought experiment that could...

Please clear any misunderstanding I have and if I am correct, kindly give me some more details and depth of SR time dilation which I am missing.

In relation to travel back in time, we've all heard of the grandfather paradox, whereby killing your grandfather before they sired offspring would preclude your future existence. This contradiction leads to the conclusion that time travel to the past must be impossible. But it doesn't quite end...

The picture of the question and my try: Would it be possible for someone to double-check my answer for accuracy? I would greatly appreciate any feedback or guidance on this matter.

It is common to say that ##t## and ##-i\hbar\partial_t## are not operators in quantum mechanics. But I haven't seen a satisfying justification. As an example of the precision of our discourse, someone has said that ##-i\hbar\partial_t## satisfies the definition of Hermicity, but it is not an...

(Yes, I'm guilty of passing along something incomplete and of utterly unknown provenance that someone saw somewhere and didn't understand. I feel dirty.) ∀t(T(x,t)⟹(¬H(x,t)∨H(x,t+Δt))) Certainly, without specifying any of the variables, it's got to be useless. At least we can assume t and Δt...

Reading Griffiths book on electromagnetics I stumbled upon his analogy to Newton and acceleration. Author claims that the formula for time when acceleration and distance are given is: $$t= \sqrt{\frac{2\lambda}{a}}$$, all is clear beside 2 in the nominator. My calculations goes as follows: $$a =...

Talking to my AI assistant about the Double-slit experiments that have been conducted many times, I was interested in whether anyone had conducted experiments that would reveal unusual properties of the particles being experimented on from the point of view of time. For example, place one slit...

Hello everyone, I would be thankful ir someone explained where I am mistaken in this reasoning on Einstein’s mental experiment on Special Relativity. Taking the railway as K reference frame, a light beam is thrown in the x positive direction the moment the train passes in the same positive...

Comparing "in a couple of weeks" and "in a couple of weeks' time", are there situations where one or the other would be slightly more suitable by way of more nuanced meaning?

I wrote a homage to Asimov's story "The Last Question". I tried to use modern insights on the topics that were touched upon in the original story. Those are, amongst others, Pernrose's CCC, Carols's suggested related relation between entropy and time and several others. I wonder if I...

My wife read a bit of this book and lost interest :cry:. The condition is excellent, hardly used, and it looks new, with no creased pages. I'm willing to give this away to someone in North America who hasn't read this all-time classic yet.

Hi I’m new to this site as well as physics. But it fascinates me. Is time the creation of movement?

Section 3.3 titled 'Solutions of the time-dependent Schrödinger equation' states in its 1st line that the time-dependent solution is not an eigenvalue equation: The same section ends with a comment on eigenstates: How do you reconcile this: are solutions to the time-dependent equation...

So in the model of Special Relativity, an object which is in motion is time-dilated. And let's say that we're trying to measure the kinematic time dilation of a moving clock. So an atomic clock is placed on a dolly on a track and its sped along the track. And due to the curvature of the Earth's...

A clock is set up to continuously broadcast its indicated time via radio waves to non accelerating observers in different inertial frames of reference. The clock is accelerated and its tick rate is observed to decrease by all observers relative to the tick rates of their local clocks. Its...

In special relativity, is the derivative with respect to coordinate time of relative position equal to relative velocity? Does it matter if constant velocity is used?

According to the problem statement: $$a = \frac{dv}{dt} = const \implies dt = \frac{dv}{a} \implies \int_{0}^{T} \,dt = \frac{1}{a} \int_{0}^{v_f} \,dv \implies T = \frac{v_f}{a}$$ Now, the distance covered is given by, $$L = \int_{0}^{T} v \,dt \implies L = \frac{1}{a} \int_{0}^{v_f} v \,dv...

Hi all, I'm having a discussion with a friend. I hope this is the right forum. My friend's first issue: He believes in science, but does not believe in time-dilation. He thinks that, in the atomic clocks at altitude experiment, the clocks just work differently because of less gravity, like...

So this may be a very simple problem to answer or a very stupid problem to even ask, but it’s something that I thought about and can’t quite figure it out. So my made up scenario is this. Say we have a normal sized man, and when he throws a punch it takes him one second to complete the act of...

Hello everyone, In light of this recent paper, I have some questions. I'm trying to deepen my understanding of information loss in the contexts of time dilation and quantum decoherence and would appreciate some insights grounded in established physics theories. Time Dilation and Information...

I conceptually know how to solve this problem, what I struggle with is the direction of the acceleration. For example to solve the first question I need to find the horizontal displacement when the ball hits the ground. Therefore ##l_0= x(t_1)= x_0 + v_0 t_1##, where ##t_1## is the moment the...

To find the time of this problem, I used the equations 3 + (10 * x ) = 13.5 *x. 3 = 3.5*x. Therefore x was 0.857. To start off with child A was already three feet above ground and I got the answer to the time. However I couldn't find the height.

What is the consensus on how long it would take for a galaxy to form similar to the ones which I am reading about here with Z=20? Galaxy formation time is probably of much interest right now. Perhaps formation was much quicker shortly after the BB with higher gas densities...

Next, we assume a solution in this form: Which simplifies (according to my notes) to this: In the middle equation, we have factorised out the F(t). My question is why is it wavefunction(x,t) rather than wavefunction(x). I first thought it was a mistake in the notes, but it uses the same...

I remember one of the Ant-Man movies had time travel enabled by shrinking down to an incredibly small size. This seemed silly to me at first but then I realized that a second is much closer to the age of the universe than a Planck time is to a second. This is mind-boggling and the human brain...

I had an idea about a spacetime drive that *seems* as though it is an FTL drive while trying to outline a plot for a series of sci-fi short stories set in the late 22nd-early 23rd century (possibly later as well). Instead of working with warping space ala Star Trek or utilizing a hyperdrive to...

Towards the end of proving Birkhoff's theorem, you have a line element of the form $$ds^2 = -b(t) \cdot (1 - a/r) dt^2 + (1 - a/r)^{-1} dr^2 + r^2 d\Omega^2$$where ##a## is some constant and ##b## is a (positive) function of ##t##. We are free to define a new coordinate ##t'## such that ##dt' =...

Hello, In this study https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9784821/, the distance the punch travelled from start to impact is 0.49 meters and the time taken from start of punch (that's it, they define the start of punch as the moment the elbow first start to extend) to impact is 0.1...

Attempt : I start by compying and pasting the problem as it appeared in the text. Please note that for reasons of clarity, I replaced landing station ##\text{K}## with station ##\text{N}##. Let me draw a picture of the problem situation. The landing stations M and N are shown in red and the...

my answer was D, which is correct considering the motion downwards eg, object thrown from a cliff but what if an object is moving up?like a football being kicked? i cant understand how this graph applies to that...

How can time dilation, lets say 500000 km inside the sun be calculated ?

So I have the solution here and trying to understand what happened at the beginning of the second row! How did we get the exponential $$e^{i(\omega_m - \omega_0 ) t' }$$ ?

As far as I know a field is spatial&time region in which each point has a physical quantity associated with it (vector or scalar). We know from GR that in the case of the gravitational field it is due (only?) to a curvature of space. But what about the other fields? What gives the value...

Why is it 10.92 seconds and not 10 Cars displacement = 30*t +1/2(0)t^2 police displacement = 0*t + 1/2(6)(t)^2 30t = 3t^2 t = 10 seconds ???

Will post a question and view responses