Time Definition and 1000 Threads

Diagram : I draw a picture of the problem situation and paste it to the right. Attempt : Let me assume that the position of the smaller mass ##m## at a given instant of time ##t## is ##x(t)##. (1) Gravitational potential energy ##\frac{GMm}{x} = \frac{1}{2}mv^2(x)##, where ##v(x)## is the...

How long does it take water ice H20 in space in our solar system to sublimate, say a basic ice cube? It starts as a solid cube at the temperature of whatever space is above Earth and then completely turns to vapor. Just looking for ballpark situation here. Does anyone know of a table or place...

Vix=Vcosθ Vix=0.76604*V Xf=Vixt Xf=0.77604V*2 V=Xf/1.55208

Hi, This is my first post on PF. I am engaged in a project seeking to find a simple way to reduce ethanol content in wine for those wishing to minimize alcohol intake for health or personal reasons. The alcohol-reduced wine will be used for cooking. Seems heating would do the trick however, the...

Hi, i am not a physicist but i have the intuition that time dilation is just slow in the movement of particle's and causality instead of slow in time itself and that this does not affect photons. I understand that there is no way to distinguish between a slow in time and a slow in movement and...

I understand people collapse multi dimensional functions to make simpler visualisations, eg if you have a 500 dimension objective function in machine learning you can collapse it to 2D or 3D to get a visual idea of the objective-space.is this why Einstein did it as well? to make simpler...

(I use +3 as the cutoff as that seems to be the limit of easily visible stars.) Yes, I know that Betelgeuse could go up in a < -10 blaze of glory, but I wonder what other ones are out there. On a side note, how fast could the big observatories move to it to observe it? And how quickly would...

I’ve been trying to solve this for ages. Would really appreciate some hints. Thanks

I would appreciate knowing if there is any error in the mechanics illustrated in this animation with respect to phase change in the signal reflections shown at A and B, or in the description accompanying it. I have embedded the description with the animation and included it in this post for...

Hmmm, , Does gravitational time dilation (speed up) cancel out earth orbit time dilation (slow down) for astronauts, , , it must do, to a certain extent Hmmm, , ,Mick's been thinking = the present is a continuous but fleeting moment, that allows the future to flow into the past, , ,so does the...

This might sound as a dumb and silly question but if you think about it, it makes sense. If we wrongly assume that gravity is a force just like any other, and given the fact that time is closely related to gravity and that gravitational time dilation is a thing, wouldn't reverse time travel...

Question: Suppose I have a data file for the acceleration of an object after every ## \Delta t_i##, how do I obtain the displacement of it? Context: Integral in a PID loop, although not exactly what I am asking as one is sum of error: $$\int_0^T \int_0^T \ddot {\vec \theta(t)}dtdt$$ the other...

I have a cube with a volume of 1000m3 at an initial temp of 290K. The bottom side (10m by 10m) is open to the ambient air. I put this cube into a huge fridge and cool the whole volume by 5K. I close the open side by placing a cover on it. This cube has now got a volume of air at a temperature of...

Yet no-one has been able to provide any formulae etc to expand the topic further. A lot is said about house construction (high mass vs low mass) but that doesn't take the discussion any further. I think the key question is if your house is badly insulated then it's losing heat all the time...

Answer to 1. Answer to 2. How would you answer rest of the questions 4 and 5 ?

Raquel Welch, a longtime actress, international sex symbol and Golden Globe winner, has died, PEOPLE confirms. She was 82. https://www.yahoo.com/entertainment/raquel-welch-one-million-years-200425372.html https://www.cnn.com/2023/02/15/entertainment/raquel-welch-death/index.html

Warning: Long post, apologies beforehand. So science/physics isn't my field of study or work, but am always fascinated by it (looking back, perhaps I should have went down that route). In any event, a few months ago I went to finally learn more about relativity after reading a discussion of...

Let's say there is an audio oscillator on earth sending a 440 Hz audio tone over radio to a spacecraft. There is also an audio oscillator on the spacecraft sending a 440 Hz audio tone over radio to earth. Time is slower in the high gravity of earth than the weak gravity in space. Is the 440...

I have been trying to make sense of the derivation of pressure under Kinetic Theory of Gases chapter, but it's not making sense to me when the impulse momentum equation is used for the collision between a gas molecule and the wall of the container. The book says that for the elastic collision...

Mine is a simple question, so I shall keep development at a minimum. If a particle is moving in the absence of a potential (##V(x) = 0##), then ##\frac{\langle\hat p \rangle}{dt} = \langle -\frac{\partial V}{\partial x}\rangle=0## will require that the momentum expectation value remains...

This is the question; I made some math error...then i just realised this is an easy problem...anyway, i know you guys may have an alternative approach to this; kindly share... For part (a) i have; ##a=\dfrac{10}{t_1}## and ##2a=\dfrac{20-10}{(t_1+t_2)-t_1}##...

Time moves faster when higher above the earth. Time move slower the faster you are moving. A geosynchronous satellite has to be very high to be geosynchronous so it's time should be fast, but it also has to be orbiting the earth extremely fast to keep up with a geosynchronous position, so it's...

I was watching a video on GR by mathematician Matt Parker (he of the Parker Square) where he corrected some general misconceptions about GR. Most of the video wasn't anything special but there was one concept that stood out to me: the time-dilato-pause. The idea behind it is quite simple: for...

I suppose this question ultimately boils down to: when we speak of a time translation (in nonrelativistic mechanics, so that the Galilean group is the apporpiate symmetry group under which the physics of a system must not change) what do we mean? In particular, do we mean that the value we...

Hi! Say I have a electric signal that has an RMS noise value of 10uV, I would calculate peak noise by multiplying by 6.6, so 66uV. I am looking for an equation that describes the probability of seeing a noise voltage that reaches 66uV in a given viewing time window. For example if I look at the...

what is time according to string/M-theory do objects in string theory also have temporal parts? and how does the debate of Three vs Four-dimensionalism apply to string theory which posits 10/11 dimensions?

1. How much is acceleration of light? 2. Why is speed of light constant if time is relative, to keep speed constant distance must be changed as well? 3.What is time by Einstien? If we state it is not absolute, it is illusion, dont exsit? 4. Can we say ratio between distance and time is...

Hello, Could someone please help me understand how to approximate how long it will take for liquid nitrogen in a room temperature container to completely evaporate. Here's the scenario: I have a metal container (41x13x15") filled with 5.5" of liquid nitrogen (just released from a Dewar ~ 320F)...

Will humans ever be able to travel forward in time faster than the ordinary speed? According to relativity if someone were traveling at speeds close to the speed of light they would jump some years into the future. The question however is will this ever be possible? Can humans survive at such...

I refer to the video of this page, where there is a description of Galilean relativity that is meant to be an introduction to SR, making the comprehension of the latter easier as a smooth evolution from the former. All the series is in my opinion excellent, but I think that this aspect is...

I am working on a project on vacuum drying vegetables using IR heaters. Before winter batch time was around 3 to 4 hours now it has increased to 6 hours. Any logic behind this as though the temperature drops and RH also drop so why has the time increased?

Hello everyone, I've been learning about special relativity, and so far I believe based on what I read that if you are traveling at a velocity of .6c, you will experience time 20 percent slower than people on earth. Each second in the spaceship will be 1.25 earth seconds. Each second on earth...

Good morning sirs, I have a standard bottle of wine made by glass, 0.75l. I suppose it's 20deg and I'd like to know how much time I need to lower the temperature of 4deg, considering outside it's winter, no wind, simple convection. I read some theory and I discovered some reference to Nusselt...

The Maxwell wavefunction of a photon is given in [here] as follows: Because the curl operation mixes 3 different components, this wavefunction only works for a minimum of 3 space dimensions, with each grid point having 6 component numbers ##{E^1, E^2, E^3, B^1, B^2, B^3}##, and with the...

Hi everyone I'd like to show an interstitial ad while going from MainActivity to Activity2. Instead, the ad only shows when clicking back from Activity2 to the MainActivity (using the system back button. Activity2 doesn't have its own back button). Does anyone know what I've done wrong? I...

I like time travel for entertainment purposes in books/movies but there’s one fundamental flaw I haven’t seen discussed. Any time travel example without the use of a ‘gate’ or wormhole (Star Gate SG1 for example) focuses on time only. The problem with these is you need to firstly travel in time...

Hello everyone, I am now doing experiment related to quantum erasure. After plotting the correlation measurement with and without blocking one of the polarization from the SPDC source (say, V polarization), I do not know how to work further on the gating time from the rate of the random...

Consider the interaction of a two level atom and an electric field (semiclassically, we treat the field as 'external' i.e. not influenced by the atom; the full quantum treats the change in the field as well) Electric field in semiclassical Hamiltonian: plane wave ##H_{int,~semiclassical}=-\mu...

A basic example to explain what brings about my question is when considering two objects moving away from each other with an object at rest in the middle. In all 3 objects' frames of reference they are going through their respective time axises at the speed of light. It would appear that time...

So the pattern goes: x(t) v(t) a(t) jerk(t) You can keep taking slopes of lines, and slopes of slopes - my questions is, what happens in the other direction- areas under curves and more areas under curves. What is the area under the x(t) curve? x*t, what is position multiplied by time?

As a child I have always wondered, as I used to watch a lots of sci-fi cartoons, if it's ever possible to time-travel. It has always been like a fairy tales to me until a friend of mine passed a magazine to me. It was Einstein's 100th birthday, and the headline of the weekly science magazine was...

This is both a biomechanical and sociological question. There is a planet. It orbits around a large star whose goldilocks zone is significantly far from the star that the orbit is measured in thousands of Earth-years1. The planet is tide-locked2. The planet is otherwise the same size and...

My approach; ##v=u+at## ##0=12-3t## ##t=4## i.e at point when deceleration starts up to the point cyclist stopped (point ##B##). Therefore, distance travelled in the ##4## seconds is given by, ##s=(12×4)+(0.5×-3×16)=48-24=24##m ##⇒240-24=216##m ##t=\dfrac{216}{12}=18 ##seconds...

For part(b), The solution is, However, where did they get the formula shown in red from? Many thanks!

I've been thinking about how rotational speeds don't fall off high distances from galactic centers, for which dark matter is generally an explanation for the increase in acceleration Speed = distance / time But time is relative What "time" is used in these calculations? Wouldn't time be...

The recent threads about relativity and the (ersatz) twin paradox got me flummoxed (again). I referenced a story (A World Out of Time) where the man character came back to an Earth that was 3 million years older than when he left. The reason is that he journeyed to the galactic centre and back...

If I understand it well, 10 s did really passed in the rocket, it is according to the observer on the Earth, but if the man in the rocket measured the time, he would measure 10 s. But when we say that the man in the rocket is in an inertial frame of reference as well, he can claim that because...

Hello! I am reading this paper and in deriving equations 6/7 and 11/12 they claim to use second oder time dependent perturbation theory (TDPT) in order to get the correction to the energy levels. Can someone point me towards some reading about that? In the QM textbooks I used, for TDPT they just...

Is it possible to have a universe with only space and time but no mass ? I ask this question because a friend told me that time is an illusion. In fact, time does not exist. Because of the existence of matter, time can be felt through the movement of matter. If matter does not exist, time does...

Hello! If I have an ion which can be treated as a 2 level system, in a time varying electric field (the variation of the field doesn't need to be on or close to resonance, but for simplicity we can assume it is an oscillatory field) can I simply separate the problem into a center of mass motion...