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.
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...
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?
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...
I have heard from a knowledgeable physics proffessor, time exists independently and it is not a consequence of arrow of time. Could some body explain this?
If time slows down for an observer traveling at some speed relative to your proper time, shouldn't the traveling observer also see your time slow down relative to his proper time? Or does the observer see your time speed up relative to his proper time.
Also, is dilation exactly the same in...
If the universe were to re-collapse, the Hubble constant would increase over time. Since the age of the universe is the inverse of the Hubble constant, the age of the universe will decrease. Does that mean time reversal?
We study metrics, in them, we take time as a coordinate. I mean to say that if time is a coordinate then in normal mathematical language, we can have negative coordinate values as well. This confuses me a lot as I want to see and understand the concept from the true physicist's perspective...
Consider an observer on Earth (Neglect any effect of gravity). Call him A. Let 2 rockets be moving in opposite direction along x-axis (x-axis coincides with the x-axis of A) with uniform velocities. Call them B and C. At t=0, in A's frame, the rockets are separated by length ##l## . Let ##V_a##...
Summary:: what do 12:00 AM and 12:00 PM really mean.
How do you say the time at at noon. is noon 12:00 AM or 12:00 PM? 12:00 AM means 12 hours before meridian or before noon so 12:00 AM should mean 12 hours before noon or midnight.
12:00 PM means 12 hours past meridian or 12 hours...
I mean, as a simple example, vector analysis involves the study of higher-dimensional objects in Euclidean space, objects that are downright impossible to visualize using simply pencil and paper. When my professor taught it, he often explained the topics using analogies that tied into vector...
Hello All
The Hafele-Keating experiment in 1971 confirmed measurable time dilation effects on atomic clocks flown around the Earth on aircraft.
Presumably clocks aboard the International Space Station suffer worse time dilation because of their greater speed in orbit. How often are corrections...
Write a linear equation.
A school district purchases a
high-volume printer, copier, and scanner for $24,000. After 10 years, the equipment will have to be replaced. Its value at that time is expected to be $2000. Write a linear equation giving the value V of the equipment
during the 10 years it...
Did some searches through these forums but didn't find this exact question. I'm sure it's already been asked, but I just missed it, my apologies. Please link.
I’ll try and ask this question in 3 different ways, and maybe the idea behind it will become apparent. I know that semantics can really...
Homework Statement:: This isn't a homework but more of a conceptual question.
Relevant Equations:: Proper time, ##\tau##
Simply put, the proper time between two events as observed in an unprimed frame is calculated along the timelike worldline between the two events. This implies that the...
the calculation 6C4 shows 15 but what if all sets are to be distinct? meaning 1,2,3,4 is the same as 4,3,2,1. I made a tree diagram and i get 10... assuming i did that correctly...?
I want to simulate the time domain data for a rotating radar. I assume that the space around the radar is filled up with a very big extended object and it moves with a constant speed in one direction. Picture attached.I don't take range information here. I am only concerned about the velocity as...
Just as the time dilation formula for the Schwarzschild metric in terms of the position ##r## away from center of mass for a gravitational body and the Schwarzschild radius ##r_s = {2GM}/{c^2}## is given by
$$ \tau = t \sqrt{1 - \frac{r_s}{r} } $$
so I'd like to know the corresponding...
According to Relativity, any object traveling at c will not experience time, because of time dilatation. It will seem to the object that it has traveled instantly while ages may pass outside. Further, an object without rest mass will always travel at c. Therefore, if there were no objects with a...
So my idea is: Let's say you are in a room, that is 10km in the ground (so its closer to the center of gravity of earth) and made of Osmium.
Could it be that the room, because of its mass, actually bends the space time with the Earth's help more so time could be running slower for you?
If it is...
I am trying to simulate and process the Doppler signals. My main problem is a little more complex so I am only posting a simple version of it. Task1: I have a time-domain signal with the velocity of the target as mu. I need to change the velocity to mu cos(theta) where theta is a vector from 0...
Since the time like spacetime interval is equal to proper time for stationary or traveling observers, then it seems time dilation (proper time) seen with traveling clock is necessarily frame invariant. Then the so called time between ticks of both identical clocks, with stationary and traveling...
In derivation of relation for pressure of Gas ,(see pic below) the time for rate of change of momentum of molecules should be the time for which the wall of the vessel and the molecules kept interacting with each other, not the time between successive collisions. As circumscribed below, my...
hi users, I'm a new member of the forum. My question is about time travel in the quantum world. I am aware of the enormous limitations, but my topic is about individual particles and their ability to travel through time, is that possible for them? My question comes from a speech by an important...
Is it possible for me to get a PhD in electrical engineering while going part time, one class at a time? The college I'm thinking of going to has a 8 year time limit for PhDs before credits expire. 8 years seems like a long time. This would allow for 16 different classes, not sure if summer term...
Is there a constant for the rate at which time slows relative to the amount of mass? If so would there be a base measure eg time being present with 0 mass
So if I have a tubular reactor for nanoparticle synthesis (PTFE tubes ID:2mm). The tubes are heated in a furnace. liquid Reagents at room temperature are pumped by a syringe pump and directed toward the furnace. The reagents decompose to form nanoparticles once they reach the steady-state...
Hello: Let's say you have a string and get data by changing the frequency a transverse wave in the string to get different standing modes. You measure the wavelength of each mode for each frequency. That is, the data you get are frequency and wavelength. Now, you are trying to find the...
Maybe we could use
(1) uncertainty principle
$\Delta E \Delta t = \hbar$
and get $\Delta E$ from the spetrum.
Or
(2) forced vibration model, then get the damping factor $\gamma$,
and get $Delta t = frac{1}{\gamma}$
1) -|2x-3|+|5-x|+|x-10|=|3-x|
2) |2x-3|-|5-x|-|x-10|-|3-x|=28
3) -|2x-3|+|5-x|+|x-10|≥|3-x|
How can we solve these problems?
The method I know is to plug in the critical values to see which modulus becomes positive and which one becomes negative. Then find out the values of x for which the...
My country has been hard hit by second wave of covid, so bad that the colleges that were conducting classes online had to be paused for two weeks. So since i have time, i am thinking of using it properly.
I was wondering should i pursue how to proof in maths since i have linear algebra in my...
Another member and I, in private conversations, have been discussing the time average tension in a pendulum string. He has done a numerical analysis of the problem, and his calculations indicate that the time average tension is less than mg. I have analyzed the problem analytically by...
A long time ago, I was very impressed by a lecture on elementary special relativity which showed in simple math how the correct conclusion to the null results of the Michelson-Morley experiment were obtained by concluding a constant c but then adding a length contraction and time dilation. I...
This is just something unexpected that I noticed recently, and I hadn't heard anyone mention it before.
The relativistic Lagrangian for a particle moving under a scalar potential ##\Phi## is this:
##L = \frac{1}{2} m g_{\mu \nu} \dfrac{dx^\mu}{d\tau} \dfrac{dx^\nu}{d\tau} - \Phi##
This leads...
(a) I imagine there are several rectangles to represent the area under graph of p vs t then I try to make equation for the total area. Since the question asks about time when the container holds 22 fewer liters than it does at time t = 9, I think the total area of rectangles starting from t = b...
I don't have much knowledge on general and special relativity except what I watch on youtube and read, btw.
Edit: In addition, is traveling through a geodesic in spacetime relativistic between the object and spacetime itself? In other words, if I was traveling through a geodesic deep in space...