Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience. Time is often referred to as a fourth dimension, along with three spatial dimensions.Time has long been an important subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars.
Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems.Time in physics is operationally defined as "what a clock reads".The physical nature of time is addressed by general relativity with respect to events in space-time. Examples of events are the collision of two particles, the explosion of a supernova, or the arrival of a rocket ship. Every event can be assigned four numbers representing its time and position (the event's coordinates). However, the numerical values are different for different observers. In general relativity, the question of what time it is now only has meaning relative to a particular observer. Distance and time are intimately related and the time required for light to travel a specific distance is the same for all observers, as first publicly demonstrated by Michelson and Morley. General relativity does not address the nature of time for extremely small intervals where quantum mechanics holds. At this time, there is no generally accepted theory of quantum general relativity. Time is one of the seven fundamental physical quantities in both the International System of Units (SI) and International System of Quantities. The SI base unit of time is the second. Time is used to define other quantities – such as velocity – so defining time in terms of such quantities would result in circularity of definition. An operational definition of time, wherein one says that observing a certain number of repetitions of one or another standard cyclical event (such as the passage of a free-swinging pendulum) constitutes one standard unit such as the second, is highly useful in the conduct of both advanced experiments and everyday affairs of life. To describe observations of an event, a location (position in space) and time are typically noted.
The operational definition of time does not address what the fundamental nature of it is. It does not address why events can happen forward and backward in space, whereas events only happen in the forward progress of time. Investigations into the relationship between space and time led physicists to define the spacetime continuum. General relativity is the primary framework for understanding how spacetime works. Through advances in both theoretical and experimental investigations of space-time, it has been shown that time can be distorted and dilated, particularly at the edges of black holes.
Temporal measurement has occupied scientists and technologists, and was a prime motivation in navigation and astronomy. Periodic events and periodic motion have long served as standards for units of time. Examples include the apparent motion of the sun across the sky, the phases of the moon, the swing of a pendulum, and the beat of a heart. Currently, the international unit of time, the second, is defined by measuring the electronic transition frequency of caesium atoms (see below). Time is also of significant social importance, having economic value ("time is money") as well as personal value, due to an awareness of the limited time in each day and in human life spans.
There are many systems for determining what time it is, including the Global Positioning System, other satellite systems, Coordinated Universal Time and mean solar time. In general, the numbers obtained from different time systems differ from one another.
With no applied moments, it is asked to prove that a gyroscope Fermi-Walker transports its spin vector ##S_{\alpha} = - \dfrac{1}{2} \epsilon_{\alpha \beta \gamma \delta} J^{\beta \gamma} u^{\delta}##. In a local inertial frame ##u^{\alpha} = (1, \mathbf{0}) = \delta^{\alpha}_0## and...
I have a graph of mean signal (per pixel) vs exposure time (sec) for 8 different dark frames. I am being asked to find the bias in ADUs/pixel and the dark current in ADUs/sec/pixel and I am very confused on how I could get it. I know that the average of all of the mean signals is a rough guide...
I am a little lost on the last step of this problem. I get that we want to know how much time elapses for the capacitor to reach 2/3 of its final charge. That is why 2/3Qf is equal to Qf(1-e^-t/RC).
I don't understand how we make the jump to e^-t/Tau is equal to 1/3? and then somehow e^-t/Tau...
A rocket of initial mass m0 is launched vertically upwards from the rest. The rocket burns fuel at the constant rate m', in such a way, that, after t seconds, the mass of the rocket is m0-m't. With a constant buoyancy T, the acceleration becomes equal to a=T/(m0-m't) -g. The atmospheric...
Here is something I don't understand which I expect someone here can explain.
If one member of an entangled pair goes on a trip at relativistic speeds, there will be two different frames of observation, with two different elapsed times.
The time frames can get off-set by years, over a long...
Hello everyone,
I wanted to know how speed can dilate time. For example, if there is a star 100 light years away from Earth and I started traveling at light speed, how long would it take for me to get there? I understand that the time differs from the point of reference (ie time from Earth's...
This started from the following post:
We have no idea if we will need to keep boosting every few months. The latest information I am aware of is the following:
https://www.cnbc.com/2021/10/04/pfizer-covid-vaccine-protection-against-infection-tumbles-to-47percent-study-confirms.html
That...
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...
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!
Hello! I saw in many papers people talking about the effects of a time dependent perturbation (usually an oscillating E or B field) on the energy levels of an atom or molecule (for now let's assume this is a 2 level system). Taking about energy makes sense when the hamiltonian is time...
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!
Hey! :giggle:
a) Suppose a binary pick-up adder (carry-select) of $32$-bits, comprising $4$ sub-sections adders spreading carry of range $8$ bits. Show the values obtained internally in the circuit of this adder to perform the addition of the numbers $01011001101100111110110011001101$ and...
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...
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...
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...