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.
There are many examples where physics explains why sensations of the same phenomena (e.g. lightning) affect senses at different times ( flash of thunder vs sound of thunder). What are notable examples where it's mainly the speed at which the brain processes sensations that explains a time...
For case B-
Conditions:
1. The observer was observing since the time they were in contact.
2. There are only 2 directions for motion: back and forward.
3. Relative velocity is not equal to zero.
4. Bodies are moving away from each other
Time difference = t
Relative velocity = v
Distance between...
I’m trying to come up with a term to describe how time moves slower or faster in different places of a galaxy. I’m trying to explain how in Star Wars, things seem to move differently for different characters in separate locations. I’m trying to argue that Han limping to Bespin took “longer” than...
probably a daft question asked before, but.
if space is expanding at an accelerating rate would that mean time is accelerating too?.
after all Einstein* claims and the maths seems to say that space and time are the same thing, ie space-time.
so if space is expanding faster and faster shouldn't...
Here is my not particularly well thought out Earth Day Proposal for your collective consideration.
The building of palm oil plantations is often cited as a driver of tropical rainforest deforestration (which is thought to contribute to climate change in a variety of ways (I'm not providing...
Hi,
I am trying to understand the running time of FF both the original and improved version. For the original version book says:
What I understand from this that before placing the items, FF traverses all the bins from beginning to end i.e. n bins.
Now each bin can have n items, because of...
Hi guys,
i hope i find the right Sub-Forum. Can you please tell me if i calculated it right.
A car speed's up with 5 m/s² to a speed limit of 50Km/h. After it arrived the speedlimit it drives for 30s with the speed of 50km/h. After that it break with a negative acceleration 3.0m/s² to stop...
Could I please ask for help with the following question (the second part):
A cruiser sailing due north at 24 km/h sights a destroyer 48 km due east sailiing at 56 km/h on a course (360-a) degress where cos(a)=11/14.
Show that the destroyer's course realtive to the cruiser is on a bearing of...
I've been trying to understand gravitational time dilation by considering a light-clock of length ##l## undergoing an equivalent acceleration ##a## from rest along the direction of the bouncing light pulse.
I find that the time ##t## that the light pulse takes to travel to the forward receding...
I try to justify time-reversal symmetry in a very simple classical problem; Free Fall. The position, ##x##, and the velocity, ##v## are obtained versus time from the equation ##-g=\ddot x##. So, if we consider the primary conditions as ##t_0,x_0,v_0## it is clear that...
It is fairly trivial to do this with a circular orbit: $$(x,y) = (cos(\omega t),sin(\omega t))$$
where t is time, and $$\omega = \sqrt{GM/r^3}$$
How this parametric equation look for an elliptical orbit?
Hello. I am a filmmaker writing a screenplay and I am in need of technical support to validate a method being used in the film.
I am going to post this in the Earth Science forum but I'll copy it here, in case anyone reading this might know.
Thank you all!
"I am wondering if shadows cast...
I'm not sure about my proof. So please check my step. I used log as a natural log(ln).
Specially, I'm not sure about "d/dt=dρ/dt d/dρ=i/ħ [ρ, H] d/dρ" in the second line. and matrix can differentiate the other matrix? (d/dρ (dρ lnρ))
Given initial displacement ##X_0## and displacement at any time ##t## as ##x##.
Where ##x(t)=f_t(X_0)## where the functional dependence of ##x## upon ##X_0## changes with time.
For exm ##X_0=2## and ##x(t_1)=X^2_0=4,x(t_2)=X^2_0+1=5,x(t_3)=X_0^3+3=11...##and so on.
From this, is there any method...
I am including a link to a B level discussion of this I found on-line to try and anchor my question, not because I think the below article is good or poor - I am not able to assess that.
https://www.einstein-online.info/en/spotlight/changing_places/#The_analogy
In particular I am asking about...
I was told to solve the second equation above for x to get l2 and l2, but that only gets me those in terms of other unknowns. I'm assuming I just need to solve t for my knowns, but I keep getting caught up by my unknowns. i.e., solving for x gives x = (l2*L*v2)/(l1*v1+l2*v2). Please note "l" is...
If a black hole experiences infinitely slow time (IE time stops) due to their singularity, how are they able to move/orbit?
If supermassives occupy the centre of most/all galaxies. How are the galaxies moving if the black holes can't?
Applying the time reversal operator to the plane wave equation: Ψ = exp [i (kx - Et)]
T[Ψ ] = T{exp [i (kx - Et)]} = exp [i (kx + Et)]
This looks straightforward as I have simply applied the 'relevant equation' however my doubt is in relation to the possible action of operator T on the i...
U=-∫F*v*dt= -∫(m*g/3)*cos(ω*t) dt = -(m*g/3 )* (v/ω )* sin(ω*t)
except that according to the official solution, I should be getting positive sign instead of negative. Am I doing something wrong?
And also an answer to 'where are the future time travellers?'. Let's say hypothetically that in the future time travel into the past is invented. To me many worlds looks like metaphysics, but it appears to be taken seriously by physicists, therefore, what if after traveling backwards in time as...
Hello all:
I hope all are fine and well in their houses
As I am looking into ways to fill my empty time other than reading undergraduate physics books I start to look around and wonder about giving online lessons for public school students , which they are now without a school , but I found...
Ok so here's my idea,it came to me while watching a record album spin on my turntable(I believe it was Dark Side of the Moon). Technically this exp. could be done now but the results would take a while.
You take a disc of some super strong material attach it to a ultra high RPM motor and put...
Assumption: Screen detector is much closer to the slits than in "standard experiment" and the small angle approximation can't be used to determine the interference fringe maxima, but the interference pattern still occurs.
Is it possible to measure the time of detection in such setup accurately...
I conducted a mass-sprig experiment to see how stiffness of a spring and mass affect the frequency of oscillation. In addition to this to this i have to plot a graph to show displacement,velocity and acceleration of the mass as a function of time.From my research online
For the displacement as...
Unfortunately, the only source I could find on the internet is the one I cited in the summary. This source has the date and GMT time for the two annual equinoxes and the two solstices for a hundred years: 2001-2100.
The 99 time difference values, Ai, shown in the graph below were calculated as...
Can someone simply explain to me what are the time crystals? What are they built from (matter, do they have mass)? I cannot find a clear explanation of them. I just know that ordinary crystals are 3d, time crystals - 4d.
Hi,
starting from this very interesting thread
I'm still a bit confused about the conclusions.
The main point, as far as I can understand, is all about conditions for a quadrilateral to be considered a parallelogram.
My first basic doubt is: the concept of 'parallel' applies just to geodesic...
According to the theory, every mass has a Schwarzschild radius associated. Any object whose radius is smaller than its Schwarzschild radius is called a black hole.
So in principle is possible to create mini-black holes, it is just a fact of matter condensed.
Those mini black holes have their...
Could I please ask for help regarding my answer to the following question?
I've done the first part and get the answer of 500 seconds.
I anticipated no problem with the second part, it is the same problem with different inputs, but I have disagreed with the provided answer of 1754 seconds. I...
If Planck length is 10^-35 of a meter and Planck time is 10^-43 of a second, doesn't that mean that as the relative speed gets closer to the speed of light and time acceleration and length contraction are happening, they are happening at a different rate, since length contraction has to reach...
Hi,
I want to know if the algorithm to find prime number has running time O(sqrt(N)) or O(log^2N). log^2N is better than sqrt(N). Also for large values can it become a pseudo polynomial algorithm?
Zulfi.
Sean Carroll gives the Planck's set of four dimensioned quantities: Planck's mass, length, time and energy. I wanted to compare them with actual things.\begin{align}
m_p=\sqrt{\frac{\hbar c}{G}}&=2.18\times{10}^{-8}\rm{kg}&\rm{{10}^{7}\ E. coli}\phantom {100000000000000000000}&\phantom...
I get two different answers even the area of the graph.
I think there is something wrong with the equation I constructed for average speed part.
I know the method 1 is correct. But I'd like to know why the average speed cannot be used. And why I get two different areas for the graph
Thank you
[Moderator's note: Thread spun off from previous discussion due to topic change.]
Does the observed quadrapole moment change over time when considering a relatively moving object, for certain choices of observer coordinates?
My suspicion is that it does (Terrell-Penrose rotation implies...
I need to perform a phase shift for a measured time domain signal. The signal consists of around 1000 points. I wrote an algorithm for this in Python a while ago and it seems to work as intended, but now I noticed that the algorithm is actually unexpectedly slow.
Is it so that phase shifting is...
I have attempted to draw a sketch of this but can't see how the data they gave me help to find time period
This is what value I have ended up getting but I believe is wrong
Much appreciated for any help!
If a proper time measuring clock goes along for the ride between events, then is such a clock physically possible as the scale factor changes / increases in the Friedman metric? How could any clock have zero spatial changes for that situation?
Summary:: Linear Quantum harmonic oscillator and expectation value of the potential energy (time dependent)
Hello, I have attached a picture of the full question, but I am stuck on part b). I have found the expectation value of the <momentum> and the <total energy> However I am struggling with...
Let us suppose we have a functional of f such that ##f=f((\vec{r}(t),t)## where ##\vec{r}(t) = a(t)\vec{x}(t)##.
I am trying to derive an equation such that
$$\left.\frac{\partial}{\partial t}\right|_r = \left.\frac{\partial }{\partial t}\right|_x + \left.\frac{\partial \vec{x}}{\partial...
Do photons, I'm not sure how to express this, "experience" time? Since they move at the speed of light does time not exist for them? If time does not exist, how is it possible for anything to happen to them. If interacting with matter requires a change in their condition, how can a change in...
I tried finding a.a (four vector inner product) and I got to γ4{(v.a)2(1-γ4v.v - 2γ2) - a.a}, where again a and v are three vectors on the rhs (sorry to be confusing). a.a = g2 since it's a constant.
I have no idea where to go from here to find the time and position. Please help!
Why for some systems (such as the electron or neutron) the presence of an electric dipole moment (EDM) implies time reversal violation, while for others, such as water molecule, this is not the case? Thank you!
MY CONFUSION (WHICH IS WHAT THIS POST IS ABOUT):
* The reason why c is not the correct answer is because unitasking just means a system that has one simulatenous user, right? In other words, a unitasking system can still be a multiprogramming system, such that one simultaneous user has the...