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.
in special relativity we have moving reference frames resulting in a different flow of time in each reference frame. This we can explain because we use the fact that the speed of light is the same in all reference frames, leading to the Lorenz transformation giving the amunt of slowdown of time...
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cannot understand this deadtime compensation method. So I have provided the whole cut out of the section of this book.
BOOK: Control of Electric Machine Drive Systems Book by Seung-Ki...
Some BSM theories, often but not exclusively string theory inspired, have an extra time dimension, as well as extra spatial dimensions.
I'm trying to make sense of what it even means to have more than one time dimension, ideally, with a concrete example that illustrates how the second time...
I put the net charge density ##\rho_q = e\delta## so that ##\nabla \cdot \mathbf{E} = e\delta / \epsilon_0##, then I tried Maxwell IV:\begin{align*}
\dot{\mathbf{E}} + c^2 \mu_0 \mathbf{J} &= 0 \overset{\mathrm{div}}{\implies} e\dot{\delta} + \nabla \cdot \mathbf{J} = 0
\end{align*}but this...
Using the above formula I get that the time goes 6.5∗10−86.5∗10−8 percent faster in ISS. Thus, this is approximately 2 seconds in a year. But the answer is much lower. Where am I making a mistake?
Hi everyone,
After completing high school, I will enroll this fall at a 3 year technical school in China studying industrial robotics, but I still plan on getting into an undergrad physics program at a later time. (Some colleges can allow a transfer to their undergrad program after technical...
I tweeted this on a Sabine Hossenfelder’s Twitter thread:
Is there an example, definition, explanation of time that is not derivative of a physical system like a clock, e.g., that's based on the rotation of the earth? If not. If time is not a stand-alone definable entity how can it qualify as a...
The FLRW metric has been introduced to characterize the homogeneity and isotropy of the Universe and accordingly to obtain "easy" manageable solutions in Friedmann equations.
The FLWR metric is
where the LHS can be written as where is the proper time (despite we know that time is...
I'm interested in chemistry but it's all new for me and I'm just starting out. I tried to do some calculations but got stuck...
I was wondering, for example a supplement has the following values:
Molar mass: 306.247 g mol-1
Tmax 2-4 hours
Cmax 363.3 ng / ml
Half life: 11.21 hours
How do...
I tried using the 109 J to convert to seconds but that didn't work. I also looked through the energy equations but nothing worked. I am not sure how to find time.
Suppose you have the following situation:
We have a spacetime that is asymptotically flat. At some position A which is in the region that is approximately flat, an observer sends out a photon (for simplicity, as I presume that any calculations involved here become easier if we consider a...
This statement got me thinking, would it be possible for 1 universe (out of the infinite collection of universes) to be stationary infinitely alternating between state A & B, or using the dice analogy throwing a 1 and a 2 over and over effectively making this universe appear looped in time...
This is a basic question, in the sense that it is simple but could be also considered as fundamental.
It has been stated on this forum, that time is what we read on the clock. It is mentioned that this was also a statement by Einstein himself (Zeit ist das, was man an der Uhr abliest).
This...
In this picture it shows a light clock. Let's use the moving light clock example.
Am I essentially calculating the b component of moving clock.
Assume the moving frame is the B frame.
Assume the stationary frame is the A frame
https://simple.wikipedia.org/wiki/Light_clock
Or essentially the b...
I tried very hard studying calculus before my semester started. I self-taught myself for months and realized that I was actually good at it. I felt very confident, so I decided to take a online summer class. This was my first calculus class ever. Rather than a 15 week semester, the class is only...
Hi,
For years I wanted to understand why we have a 3 phase supply and not a 2 phase supply in AC. In Quora I found an interesting answer and was convinced about the purpose mentioned:
Answer to Why there is no two phase electrical inputs instead of three phase and single phase? by Paul...
What is the prerequisite of "the length of world line equals proper time"?C=i?orC=1?If metric is-+++:
##ds^2=-c^2d\tau^2\Rightarrow whenC=i,s=\tau##
If metric is +---:
##ds^2=c^2d\tau^2\Rightarrow whenC=1,s=\tau##
So,which one?
I've been thinking about gravity. If mass contracts spacetime, can the warping effects be measured in time as well as spatial distance?
For example -- say you had some matter that suddenly disappeared (please ignore the "how"). Measured in a fixed position, would the gravitational effect drop...
Hello,
My name is Dave and I'm a physics major at UIUC. It looks like I will be taking the special relativity course (phys 225) this fall. I've always been fascinated by the theory so I decided to get a head start with Lenny and Art's perspective on it.
My first head-scratching moment came in...
Hello! I am generating electrons from a 3D gaussian source. The electrons all have the same energy, but the direction is isotropic. The electron source is in between 2 plates that act as a capacitor, and one of them acts as a time of flight (tof) detector. I know the voltage on the plates very...
I'm fairly certain that the first one is marked correctly.
Should the second one be where there are red marks or is it correct as it was marked previously? Any advice with graph reading?
Halves-lives and average lifetimes, when studying nuclear decay, are often expressed in years even though years are not standarized, at least in SI (as far as I know). Borrowing the convention from astronomy and astrophysics, I usually take 1 \mathrm{yr} to be equal to 365.25 days of 86400...
Hopefully the answer on this question is positive.
This forum has a very good reference about the Experimental Basis of Special Relativity. The tests of the Twin Paradox conclude that faster moving clocks tick/run slower, however this seems to be an 'absolute' fact. They do not show symmetry or...
In the table of nuclides, it shows that Ag 108 can go through either electron capture or beta- decay (though the branching ratio for electron capture decay is much lower). What determines that? Do nuclides try to maximize binding energy or binding energy per nucleon? And is decay into Palladium...
Hello everyone! I was doing some dimensional analysis to find an equation that gives a acceleration as a function of time, using constant power. I came up with the equation $$a = k\sqrt {\frac P {mt}}$$ I differentiated velocity with respect to time in order to check my work and also checked out...
Hello, I'm not sure if this is the right place to post my question, however I still want to know. Recently, my teacher asked me the following question:
"In which of the cases will the cooling time be the least:
1. the ball is suspended from the ceiling
2.the ball lies on a stand with a thermal...
Summary: Trying to differentiate with respect to ## \theta ## is entangling me in cos and sec terms.
A simple problem I found, while looking for calculus practice. Roads between home and main road are 30 mph, main road is 60mph:
What is the optimum ## \theta ## to minimise journey time?
## t...
THe question is pretty simple. I was doing an exercise, in which $$p = \lambda P, Q = \lambda q$$ is a canonical transformation.
We can check it by $$\{Q,P \} = 1$$
But, if we add $$t' = \lambda ^2 t$$, the question says that the transformation is not canonical anymore.
I am a little...
I've been trying some online projectile problems. Specifically, I was using this one on master difficulty, looking at row e. It uses a random number generator; I shared the data I received in the Homework Statement above.
According to the help section, you can solve this with the formula...
hello i would like to get some help with this problem.
At first it try to calculate the impulse by the area but i found it too difficult
Then i try to solve it by the forumla J= F(t-t0), but the problem is that i don't know what F is so i try to solve it like this
F10) = 8
F(33) = -13
so
EF =...
I understand it's experimentally verified muons traveling at relativistic speeds relative to an observer will be observed to have longer half-life than would be observed in the rest frame of the muons, which is explained theoretically by a relativistic time dilation effect. Does this correspond...
According to a video I watched recently 'time' allegedly runs a tad slower in places on the Earth where the magnetic field is stronger. No doubt that has been tested and confirmed by atomic clock experiments.. to my simple mind that just suggests a timing error caused by the difference in...
Obviously, a third observer who is at rest with respect to the disk will see that the clock on the outside has a much faster velocity than a clock on the interior of the disk, so clearly the outside clock will show that it has measured less time.
But that's one question. What about looking at...
I am looking for an equation that I can use to compute L/min or mL/min for a 480cc vessel going from 150bar to 250bar with a fill time of 6min. Sensors for flow rate at these pressures are hard to find, but I thought there might be a way to work this out with the parameters known. An equation...
Not sure what I'm doing wrong...
Problem:
Sisters Helen and Anne live 332 miles apart. For Thanksgiving, they met at their other sister’s house partway between
their homes. Helen drove 3.2 hours and Anne drove 2.8 hours. Helen’s average speed was four miles per hour faster than
Anne’s. Find...
New member here; just a physics hobbyist. There is probably a simple answer to this question but I could not find it. We know time flows faster on mountaintops relative to sea level due to gravitational time dilation. Over millions of years, wouldn't there be a cumulative effect making the...
I was wondering if anyone could walk me though a better explanation on how to get the given results for these two questions. The solutions posted by my professor aren't really clear to me so if anyone is able to better explain how to get the solution it would be much appreciated!
From our local paper here in Brisbane yesterday (behind a paywall, so precis follows)
'Almost half the 35 Queenslanders who have contracted flurona since January 1 have been admitted to hospital. There have been 35 confirmed cases of people infected with both the Covid-19 and influenza viruses...
I found a website (link listed below) that gives date and time of the Winter Solstice of 1980. The date (12/21/1980). The time (UT 16:52).
Being that the Sun stays in the same position for 3 days, what is the exact day & time it starts to move again? Anyone know where to find this information...
I'm quite aware that according to Einstein light is a particle and a wave at the same time.
However, I try to imagine how exactly would light expand. A photon must likely have a certain timing for expansion. I mean, after a photon is originated it immedialy multiplies itself into many other...
These are all the chapters for introductory mechanics in my textbook. What I have been doing is reading the chapter then following it up with watching a tonne of lectures and worked examples on that topic and attempting to do the problems.
I’m on Applying Newton’s laws and I’ve been studying it...
I have read that nothing in math makes time having more than 1 dimension impossible. But if time had 2 dimensions or even 3 dimensions on its own, what would that mean? Could time travel and time travel paradoxes be allowed without destroying the universe or creating branch realities?
I think...
A science teacher ask if I could help one of her students build a "Time Dilation Clock"
so, at launch the Ships chronometer and the local time are in sync. with a 3g continuous thrust, at some point the time, the time at the launch site will be going twice as fast as the ships chronometer.
so...
I'm trying to make sure I understand how the traveling twin tracks the time of his stationary earthbound sibling and the time of another stationary observer who's farther away. From what I've understood until now, it's pretty straightforward with the earthbound twin: In the traveler's frame, the...
Homework Statement:: The SI definition of unit of time says the following.
"The second is the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom."
Relevant Equations:: None
I know an...