Time Definition and 1000 Threads

For a particle moving in a straight line, if the velocity is zero for a time interval, the acceleration is zero at any instant within the time interval. I am told the above statement is true. If I look at the equations v = dx/dt a = dv/dt It looks like if the velocity is zero for a time...

Equation for the tide: $$y=-\cos \left(\frac{2 \pi}{6}t\right)+2$$ When ##y## = 1.5 m : $$1.5=-\cos \left(\frac{2 \pi}{6}t\right)+2$$ $$-0.5=-\cos \left(\frac{\pi}{3}t\right)$$ $$\frac{\pi}{3}=\frac{\pi}{3}t$$ $$t=1$$ But the answer key is t = 2. Where is my mistake? Thanks

Hi, Just opened some .xml file in which time is given as a 10 digit number starting with 1570. I assume it represents the number of seconds from some baseline date. Anyone know if this is it and if so, the baseline date? Thanks.

I want to develop a 2D random field and its change with time with constant velocity. My process: 1. Define a 2D grid [x, y] with n \times n points 2. Define 1D time axis [t] with n_t elements 3. Find the lagrangian distance between the points in space with the velocity in x and y ...

It came to my attention yesterday this, from my ignorant point of view, amazing paper that describes what it looks as another Theory of Everything: https://arxiv.org/abs/2110.02062 If I didnt understand incorrectly, from first principles / a pre quantum theory (Trace Dynamics, 8D octonionic...

PBS Eons on KCTS https://www.kcts9.org/show/eons/episode/that-time-the-mediterranean-sea-disappeared-esieyi https://en.wikipedia.org/wiki/Messinian_salinity_crisis https://en.wikipedia.org/wiki/Zanclean_flood https://en.wikipedia.org/wiki/Messinian https://en.wikipedia.org/wiki/Miocene

Because of the wind, airplane was shifted to the east. Assume airplane is shifted D units long from B. When airplane turnaround, the wind shifted airplane to the east again as far D and to the south as far as L to the A'. Therefore, $$2D = (v - v') t_{AA'}$$ But, $$D = v'(t_{a}/2)$$ Thus...

Hi Guys Sorry for the rudimentary post. I am busy with a numerical solution to a mechanics problem, and the results are just not as expected. I am re-checking the mathematics to ensure that all is in order in doing so I am second guessing a few things Referring to the attached scan, is the...

AFAIK there is no cosmological principle formulated about space and time. If it would be formulated, it would more or less state that spacetime is an interconnected whole, and has no gaps, edges or boundaries. It doesn't need to state wether spacetime is finite or infinite, that is an open...

Hello, I am a 15 year old who has done research around the topic of why the universe is expanding at an accelerating rate, and how it will come to an end. After years of thought (since I was 11) I have come up with my hypothesis that time itself is accelerating and slowing down, and has been...

I'm trying to understand what the time dilation looks like when moving through space and then approaching a planet's gravity field. So I have the broad understanding that if you are moving near the speed of light in a spaceship, your clock ticks normal but the clocks on other stationary objects...

Hi! I am really stuck on the concept, wouldn't we not have enough variables? I tried equation the equation for the y of the object to the slope of the hill, but I am missing several variables. Any help is greatly appreciated :) thanks!

Hi Guys I just want to make sure that I am on the right track, with regards to time derivatives. I have been out of university for many years and I have become a bit rusty. Please refer to the attached image and let me know if I am on the right track.

I have video data that shows an object moving up and down. I'd like to extract the frequency the object moves. Following the given example here (scroll down to "Examples"), am I correct in assuming Fs would be camera frame rate and L would be the total number of frames? Thanks so much!

Proper time (to) is the time interval between two events measured by an observer who sees the events occur at the same point in space. I am confused how to determine which one is proper time for this question. How to know which events occur at the same point from the question sentence? Thanks

Hello everyone - The gravitational force near the edge of the galaxy at point A (see attached image) can be calculated by assuming that all the galactic mass is located in the center of the galaxy. - In order to calculate the gravitational force in the middle of the galaxy (point B) we take...

As an object approaches a black hole’s event horizon, it experiences increasing gravitational time dilation, causing it to appear to an outside observer to slow down, until, at the event horizon, it appears to stop. An object traveling in space that increases its velocity from one...

I have an experimantally obtained time series: n_test(t) with about 5500 data points. Now I assume that this n_test(t) should follow the following equation: n(t) = n_max - (n_max - n_start)*exp(-t/tau). How can I find the values for n_start, n_max and tau so as to find the best fit to the...

Since my understanding of these geometries is wrong, I'll do this in numbered steps - the easier to correct my logic. I think the big problem I have is with the time dimension. There seems to be a presumption that the time vector will drive a falling object into a central singularity. But how...

I was working on plotting fidelity with time for two quantum states. First I used discrete time( t= 0,1,2,3...etc) to plot my fidelity. I got constant fidelity as 1 with continuous value of time. Next I used discrete set of values ( t=0 °,30 °,60 °,90 °). Here I saw my fidelity decreases and...

In my search about time travel for Is it possible or just a fictional thing as many of our estimed scientists and researchers have theoreticalize the time travel some how possible I have found some interesting information and articles regarding the the possibility of time travel and enlisting...

Hello, Just for fun - I am trying to go through The Feynman’s Lectures: Lecture #26 – Volume 1: The Principle Of Least Time. I am stuck on Figure 26-4 and specifically showing the two angles with the “double arcs” are equal. The angle of reflection BCN’ and XCF. Maybe I am just that rusty on...

Summary:: Is there time? Is there time? Or is it just an illusion !? I read somewhere that there is no time like right and left or west and east that do not exist in space and are only man-made. But in general, I believe in something that time is nothing more than repetitive movements ! For...

If there is a spaceship traveling at 0.999c, the time to reach a star 100 lyr away would be approx 100 yr (assuming no accel and decel). But on the spaceship, It would be 100 yr * sqrt(1-0.999^2) = 4.5yr. Why do we take 100 yr as the time seen on Earth and not the time on the spaceship?

Given that we know experimentally that time slows and space bends in the presence of matter, what is the actual physical mechanism that enables matter to bend space and slow time?

Paul Steinhardt: Time to Take the ‘Big Bang’ out of the Big Bang Theory? Paul Steinhard, who co-founded inflationary cosmology, is working on alternatives for inflation in the form of a cyclic, bouncing universe model. In this lecture he compares his model with the inflationary model, and...

The universal speed limit is c, and as a consequence light is confined to that limit. I was thinking about the time dilation in SR and was wondering if this is result of reaching speeds close to the speed of light or because of reaching speed close to c? For example, let's say light could be...

Summary:: We conducted the Marble Race experiment but the data of the time was lost. So I'm wondering if there's a workaround to at least put a rough estimate on it. How long it would take for the marble that weights 6g with a density of 3.4 to cover a distance of 5.8cm passing through a...

If I'm standing on Earth, is my time dilation actually greater than if I was in a rocket accelerating at 9.8m/s^2 in deep space due to me being in a gravitational field on top of the acceleration? Geodesics experience time dilation in gravitational fields, so it seems like there is an additive...

When something is described as say 7 billion light years away would't it be more accurate to 7 billoin years ago?

Let us denote the events in spacetime before the trip has started by subscript 1 and those after the trip is over by subscript 2. So before the trip has begun, the coordinates in spacetime for A and B are ##A = (t_{A_1},x,y,z)## and ##B = (t_{B_1},x,y,z) = (t_{A_1},x,y,z)##. After the trip is...

To my understanding any quantum system can be describes as a linear combination of eigenstates or eigevectors of any hermetian operator, and that the eigen values represent the observable properties. But how does the system change with time? I suppose big systems with many particles change with...

I'm doing a simple RL Circuit Lab where students use 800- and 1600-turn air core coils to measure the time constant. Experimental results very nicely agree with predicted results. However, when students insert a steel (or iron) core in the coils, experimental results are far different than...

In Sean Carroll's lectures Mysteries of Modern Physics: Time, he talks about the the CPLEAR experiment, which showed that the weak interactions are different going forward and going backwards in time. But it seems like there is a big assumption: reversing a particle interaction means that it is...

I am an Engineer, so I have some knowledge about physics and calculus. I've seen relativity in university years ago but only briefly. The majority of my knowledge in SR and GR, which isn't much, are from reading, studying and searching online myself. I have seen some definitions that I am not...

Is there anyone out there who can help a newbie understand how to deal with Berry phase dipole moment data? I ran a simulation to calculate dipole moments over time using the Berry phase method. The problem is that there are jumps in my data. There is an example at the end of this post (part...

I have attached my work here. I don't know how to proceed further?

1.One can now see why all bodies fall at same rate: A body of twice the weight will have twice the force of gravity pulling it down, but it will also have twice the mass. According to Newton’s second law these two effects will exactly cancel each other, so the acceleration will be same in all...

I am trying to find the equations of motion of the angular momentum ##\boldsymbol L## for a system consisting of a particle of mass ##m## and magnetic moment ##\boldsymbol{\mu} \equiv \gamma \boldsymbol{L}## in a magnetic field ##\boldsymbol B##. The Hamiltonian of the system is therefore...

It is said that: It is not possible to write a position vector in a curved space time. What is the reason? How can one describe a general vector in a curved space time? Can you please suggest a good textbook or an article which explains this aspect?

During time evolution of one photon with vacuum state with hamiltonian as a^†b+b^†a, the answer is cos(t/ℏ)|0,1⟩+isin(t/ℏ)|1,0⟩. But i don't know how to do calculation to get this answer. Can someone please help me? I tried to do this calculation: |0⟩|1⟩(t)=e−iHtℏ|0⟩|1⟩...

I consider three material points O, O', M, in uniform rectilinear motion in a common direction, so that in relation to the point O, the points O' and M move in the same direction with the constant velocities v and u (u>v>0). Assuming that at the initial moment (t0=0), the points O, O', M were in...

I was just looking up at the stars wondering how long they have been visible for. I started wondering if any of them might have been around this galactic neighbourhood long enough and long lived/old enough that the dinosaurs could have seen it. Do you think they’d be any? If not what might be a...

Can time dilation vary without a gravity well or accelerating a viewer towards light speed? Are there other variables that affect the flow of time?

A BH can't touch another hole's horizon for the same reason nothing else can: time drags the object to a halt for a distant observer. Right? Manifestly not. So are we wrong about gravitational time dilation, or what?

So I drew the problem and tried to derive t1 for an external observer by making the following assumptions. Inside observer sees light travel a distance of d0 meters in t0 seconds at a speed of c m/s. Bus moved Δd meters in t1 seconds at V m/s. Outside observer sees light travel a distance of...

I came across the term scattering time in Simon's "The Oxford Solid State Physics". Apparently it's supposed to be obvious because I can't find a definition anywhere but what is it? Why is so much stuff left undefined in solid state physics?

I wonder how physicists who support this theory explain the increase of entropy?

Since it asks for the time evolution of the wavefunction in the momentum space, I write : ##\tilde{\Psi}(k,t) = < p|U(t,t_{0})|\Psi> = < U^\dagger(t,t_{0})p|\Psi>## Since ##U(t,t_{0})^\dagger = e^{\frac{i}{\hbar}\frac{\hat{p^2}t}{2m}}##, the above equation becomes ##\tilde{\Psi}(k,t) =...

hi guys I am trying to implement the a second order differential equation tat contains a time dependent term, the equation looks something like r'' = -\mu/r^3+(g/g^3-m/m^3) the idea is that i want to calculate 'r' the position vector of a point, that is dependent on vectors g and m, I tired to...