# Tagged Questions

Time is defined operationally to be that which is measured by clocks. The SI unit of time is the second, which is defined to be

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### Time dilation and space time [closed]

I know a little about space time, and I know that space time is adding the time component into the three- dimensional world and creating an abstract universe. But my question is that why time is ...
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### What perpetuates change? [duplicate]

People say that our notion of "time" comes from entropy which in turn is just a large scale effect of the laws of physics, but what is it that perpetuates the laws of physics from one state into the ...
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### If time somehow went backwards would this violate one of the laws of thermodynamics?

If time somehow went backwards and all the physical events that had occurred in a sequence , would some of the events occurring 'backwards' or in the reverse order violate the principle of entropy or ...
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### Are we traveling through time at the speed of light? [duplicate]

In the image below the y axis represents time and x represent velocity. Point D represents velocity c, point E represents 1 second per stationary observers second. What this chart is showing is as you ...
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### Standardising shadow length on sundials

The sundial is fundamentally flawed in that the length of each hourly shadow changes with the seasons. If the base of the sundial was engineered to move cyclically on an anual basis however, the ...
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### Can I sum-up time?

If a kinetic process takes 1 second to complete(reach a point), and that process is repeated $n$ number of times, is this formula correct $t_t$=$n\times 1$ = total time in seconds? It's similar to a ...
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### Time dilation: reference frame [closed]

So I'm calculating how long it will take for half of some muons to decay for in a stationary observers frame of reference. They have a half life of 2.2 * 10^-6 and are moving at a speed of .98c ...
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### How can we be sure that a new frequency standard is better than the old one?

Lets assume for this question that at one point in scientific history everyone was running along well with their cesium frequency standards, and someone has a brilliant idea and builds an active ...
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### Understand the relation of time and the space dimensions of spacetime?

I assume the relation of the three spacial dimensions and the time dimension is handled purely in the mathematical domain, usually. But is there any intuitive description of this relationship, how ...
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### Why does time exist? [closed]

So I have been thinking about some subjects and one of it involves time. And I tried writing a story/question on here to summarize the bigger picture but it's not going to happen it's too complicated ...
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### How much is time slowed down inside a planet or star?

An answer to What would be the rate of acceleration from gravity in a hollow sphere? states "that according to General Relativity time passes more slowly inside a hollow massive sphere than it does ...
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### Has the effect of magnetic fields on time ever been examined experimentally?

Relativity of time can be examined with satellites as gravitational or acceleration. Is there any similar experiment with intense magnetic fields?
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### Does Time change over temperature? [duplicate]

I am not a physicist, I am just an engineer. But I dared to ask whether the temperature changes the perception of time. Let's consider a particle that "stops" at absolute zero. I was thinking as a ...
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### How come the concept of an instant of time is such a controversial topic with relativity, but with entanglement it's completely acceptable?

When talking about relativity most people say that a universal instant of time doesn't exist, but when talking about entanglement most will say that the particles are both measured instantaneously. ...
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### Observing from a black hole proximity

Suppose that you could get close enough to a black hole that time slowed down significantly for you, and you looked at a giant clock back on earth through a telescope. Would you see the earth clock go ...
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### Can photons decay without interaction?

Can photons decay like other particles without interacting with other particles or fields, i.e. by just "being"? In case the answer is "no" - does this have anything to do with them travelling at c, ...
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### Understanding gravitational time dilation / Schwarzschild metric

I've had a look at the answers to these sorts of questions already, but feel like I'm still missing something. Starting with this question, and this one and even this one here. I'm looking at this ...
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### Is there a “framerate” for the universe? [duplicate]

I've been wondering this for quite some time. I just can't wrap my head around the idea of truly continuous time. If time is truly infinitely divisible, then how can any object in the universe move? ...
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### Does time freeze at Absolute Zero? [closed]

Time has many definitions per se, but the basic idea being it's "the measurement of change" so as we know, all matter looses it's ability of changing with the loss of kinetic energy. and the where it ...
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### Time relativity / paradox [duplicate]

After watching the movie Interstellar, the theory of time relativity / paradox really mind-boggles me. If it is true that gravity controls everything even to the extent of time, then it might as well ...
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### Theory of relativity. Relative to what? [duplicate]

If I properly understand relativity, time ticks faster for an object sitting still than for an object passing by. So, in a universe with only two objects which have the same "age", object A is ...
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### Doesn't the Big Bang negate the law of conservation of matter? [duplicate]

I was watching Hawking (2004 film) and in the movie, Hawking has a sudden insight that all the matter and energy observed in the known universe may, in fact, have sprung out from nothing (singularity) ...
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### Eulerian mass conservation on a stream line to Lagrangian mass conservation

if the density of a fluid particle is conserved on a streamline, $$\frac{d\rho}{dt}=0.$$ Why does this mean $$\frac{\partial \rho}{\partial t}+(\mathbf{v}\cdot\nabla)\rho=0$$ is true everywhere? Why ...
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### Would Special Relativity Predict Time Dilation of a Geostationary Satellite Compared to an Observer on Earth?

Consider a geostationary satellite at some arbitrary distance above the Earth's equator and consider a person directly below it, standing on the Earth's equator. Both satellite and person exist on the ...
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### Why do I different values compared to my theoretical time?

I'm having an experience about time needed to charge the capacitor to the 63.2% voltage of the batteries. There are resistance, capacitor and batteries in the circuit. When I calculate the ...
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### Formation of the event horizon seems impossible with singularity inside seems impossible [duplicate]

According to what I was reading, the formation of an event horizon appears if the mass becomes compact enough. Unfortunately, due to time dilation the time for mass to fall into the event horizon ...
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### How can we justify dropping the absolute time hypothesis?

In some approaches to Special Relativity the theory is motivated talking about the Michelson-Morley experiment and how this relates to the postulate that the speed of light is the same in every ...