Time Definition and 1000 Threads

When analysing the time-complexity of an algorithm I was told to assume that a hash map is ##0(1)##. A cursory google search afterward revealed that this is true because the time complexity of the hash function is independent of the size of the hash table. That seems alright but if you have a...

Viruses become less deadly/virulent over time?

Find the question below; For part (a), i used the graph to find ##t=22## For part (b), i considered the points; ##(8,20)##, ##(13.333,20)## and ##(0,0)## it follows that, Area=##\sqrt {25.454(25.454-21.54)(25.454-24.036)(25.454-5.333)}## ##\sqrt {2842.58}##=##53.31## There may...

This is the problem; I tried using; ##s##=##ut##+##\frac {1}{2}####at^2## and ended up with, ##240## =## 12t -1.5t^2## clearly we have an imaginary solution here and therefore this may not be correct? My wild guess is that the least time (Without deceleration) should take at least...

Now this is a textbook example with solution. I understand working to solution...my only reservation is on how they used acceleration. The cyclist, i understand was traveling at a constant acceleration of ##2## ##m/s^2## before reaching the top part of the slope. Now, if he is descending...

Hey! :giggle: The burning time of an electric candle is between $60$ and $80$ hours. It is considered to be continuously uniformly distributed over this period. A Christmas tree with $12$ candles (independent of the burning time), only lights up as long as all candles are working. Determine...

By definition of the vector potential we may write \nabla \times A =B at least in flat space. Does this relation hold in curved space? I am particularly interested if we can still write this in a spatially flat Friedmann-Robertson-Walker background with metric ds^2=dt^2-a^2(dx^2+dy^2+dz^2) and...

I averaged the masses and times (which i took the time given and divided by 10 because in the problem it says you measure the time it takes to complete 10 oscillations) then plugged them directly into the T=(2(pi)((m/k)^1/2) and got the wrong answer. This is really confusing me because I don't...

Hello everyone, I have a hard time to conceptualize the case of a moving black hole. We know from SR that time slows down for moving objects; but time dilation at the event horizon is already equal (tends) to zero. It seems that it can create some sort of conflict for the black hole movement...

I don't know where. to even begin inserting numbers here. I know the Temperature would be -5 for the first T and 36 for T sub zero but I do not know how to solve this. I never had Calculus.

Hi, searching on PF I found this old post Global simultaneity surfaces. I read the book "General Relativity for Mathematicians"- Sachs and Wu section 2.3 - Reference frames (see the page attached). They define a congruence of worldlines as 'proper time synchronizable' iff there exist a...

If gravity is the affect of time dilation because of the distance from the bottom of an object to the top then wouldn’t that mean that gravity doesn’t exist at the quantum level?

Summary:: Averaging (a power of) semimajor axis to position ratio wrt to time - celestial mechanics I evaluated it this far, but i don't know how to change the dt to d theta ... the final solution is supposedly (1-e^2)^-(3/2) . Any help will be appreciated. [Image re-inserted with correct...

My interest is only on Example 6; part c only, see the problem below and the solution from textbook. is the time calculated correctly? I thought we need to use the approach shown below; my thoughts, but of course i may be missing something here, The time taken from points ##A## to ##B## is...

Assume that three boats, ##B_1##, ##B_2## and ##B_3## travel on a lake with a constant magnitude velocity equal to ##v##. ##B_1## always travels towards ##B_2##, which in turn travels towards ##B_3## which ultimately travels towards ##B_1##. Initially, the boats are at points on the water...

I was trying to further look into the fact as to why photons don't experience time and I came across this amazing forum! Planning to indulge in discussions in my free time. I am a software professional by trade. I have to admit, I'm not good at math. I resented math classes in school and...

Is the highest frequency possible the inverse of Planck time? Separate or connected question, what's the highest frequency achievable practically today?

Does time dilation in Special Relativity relate to the Doppler effect? If you move near the speed of light you experience time differently and the sound is stretched. Are these similar phenomenon?

I am just wondering if placing the Earth equidistant from 3 black holes that are spinnng would slow down time on the Earth, due to the time dilation effect. Would that give us more time to live?

Assumptions: There is no "absolute" time, time is all relative. Taking the twins paradox as an example, both twins measure a different proper time when they re-unite due to each twin taking paths of differing lengths through spacetime. Conclusion: Time Travel itself is a completely...

r = 0.25m I = 7.14kgm^2 h = 6.01m Ei = Ef mgh = 1/2mv^2 + 1/2Iw^2 2mgh = mv^2 + I(v^2/r^2) 2(35.8)(9.81)(6.01) = 35.8v^2 + 114.24v^2 v = 5.304 m/s v = d/t 5.304 = 6.01/t t = 1.133 (The correct answer is 2.2673. What did I do wrong?)

I ask this question as a follow-up of an already answered one (about the effect of velocity on time). I'm looking for the effects of SR and GR on a clock's seconds hand. The effect is very tiny though, as you can imagine. Instead of making the size of the clock vary, we can vary c, the speed of...

[Moderator's note: Thread spun off from previous thread due to topic/forum change.] Time dilation sounds really weird, can i assume it has a logical explanation?

Why is time = ct and not t in special relativity? I just started reading the book I was recommended. Maybe I missed it but as stated in the title why is time = ct and not t in special relativity? I understand they want distance/space = time. Just how do they go about doing that mathematically...

assuming initial velocity is 0 and we have the value for acceleration I'm unsure how to still use any of those equations because you must have a time value at least or a final velocity

Everything is in the photo

If I plug the solution into the Schrodinger equation I get $$(i \hbar \partial_t - H)\ket{\psi} = 0$$ Since I know that the zeroth-order expansion is lambda is already a solution I think this is equal to $$(i \hbar \partial_t - H)e^{i\phi} e^{-i\gamma}\ket{\delta n} = 0$$ If now I carry on with...

I recently had a discussion with my brother, about what it means to "move through time". His opinion is, that physicists cannot take this literally. His opinion is, that time is just an expression for change that takes place at different rates for different observers depending on their speed...

With no applied moments, it is asked to prove that a gyroscope Fermi-Walker transports its spin vector ##S_{\alpha} = - \dfrac{1}{2} \epsilon_{\alpha \beta \gamma \delta} J^{\beta \gamma} u^{\delta}##. In a local inertial frame ##u^{\alpha} = (1, \mathbf{0}) = \delta^{\alpha}_0## and...

I have a graph of mean signal (per pixel) vs exposure time (sec) for 8 different dark frames. I am being asked to find the bias in ADUs/pixel and the dark current in ADUs/sec/pixel and I am very confused on how I could get it. I know that the average of all of the mean signals is a rough guide...

I am an amateur in physics and I have a question. How does speed of an object affect time?

I am a little lost on the last step of this problem. I get that we want to know how much time elapses for the capacitor to reach 2/3 of its final charge. That is why 2/3Qf is equal to Qf(1-e^-t/RC). I don't understand how we make the jump to e^-t/Tau is equal to 1/3? and then somehow e^-t/Tau...

A rocket of initial mass m0 is launched vertically upwards from the rest. The rocket burns fuel at the constant rate m', in such a way, that, after t seconds, the mass of the rocket is m0-m't. With a constant buoyancy T, the acceleration becomes equal to a=T/(m0-m't) -g. The atmospheric...

I always find voltage vs time majorly in case of AC current. What about current V time in AC current cases?

Here is something I don't understand which I expect someone here can explain. If one member of an entangled pair goes on a trip at relativistic speeds, there will be two different frames of observation, with two different elapsed times. The time frames can get off-set by years, over a long...

Hello everyone, I wanted to know how speed can dilate time. For example, if there is a star 100 light years away from Earth and I started traveling at light speed, how long would it take for me to get there? I understand that the time differs from the point of reference (ie time from Earth's...

This started from the following post: We have no idea if we will need to keep boosting every few months. The latest information I am aware of is the following: https://www.cnbc.com/2021/10/04/pfizer-covid-vaccine-protection-against-infection-tumbles-to-47percent-study-confirms.html That...

For a particle moving in a straight line, if the velocity is zero for a time interval, the acceleration is zero at any instant within the time interval. I am told the above statement is true. If I look at the equations v = dx/dt a = dv/dt It looks like if the velocity is zero for a time...

Equation for the tide: $$y=-\cos \left(\frac{2 \pi}{6}t\right)+2$$ When ##y## = 1.5 m : $$1.5=-\cos \left(\frac{2 \pi}{6}t\right)+2$$ $$-0.5=-\cos \left(\frac{\pi}{3}t\right)$$ $$\frac{\pi}{3}=\frac{\pi}{3}t$$ $$t=1$$ But the answer key is t = 2. Where is my mistake? Thanks

Hi, Just opened some .xml file in which time is given as a 10 digit number starting with 1570. I assume it represents the number of seconds from some baseline date. Anyone know if this is it and if so, the baseline date? Thanks.

I want to develop a 2D random field and its change with time with constant velocity. My process: 1. Define a 2D grid [x, y] with n \times n points 2. Define 1D time axis [t] with n_t elements 3. Find the lagrangian distance between the points in space with the velocity in x and y ...

It came to my attention yesterday this, from my ignorant point of view, amazing paper that describes what it looks as another Theory of Everything: https://arxiv.org/abs/2110.02062 If I didnt understand incorrectly, from first principles / a pre quantum theory (Trace Dynamics, 8D octonionic...

PBS Eons on KCTS https://www.kcts9.org/show/eons/episode/that-time-the-mediterranean-sea-disappeared-esieyi https://en.wikipedia.org/wiki/Messinian_salinity_crisis https://en.wikipedia.org/wiki/Zanclean_flood https://en.wikipedia.org/wiki/Messinian https://en.wikipedia.org/wiki/Miocene

Because of the wind, airplane was shifted to the east. Assume airplane is shifted D units long from B. When airplane turnaround, the wind shifted airplane to the east again as far D and to the south as far as L to the A'. Therefore, $$2D = (v - v') t_{AA'}$$ But, $$D = v'(t_{a}/2)$$ Thus...

Hi Guys Sorry for the rudimentary post. I am busy with a numerical solution to a mechanics problem, and the results are just not as expected. I am re-checking the mathematics to ensure that all is in order in doing so I am second guessing a few things Referring to the attached scan, is the...

AFAIK there is no cosmological principle formulated about space and time. If it would be formulated, it would more or less state that spacetime is an interconnected whole, and has no gaps, edges or boundaries. It doesn't need to state wether spacetime is finite or infinite, that is an open...

Hello, I am a 15 year old who has done research around the topic of why the universe is expanding at an accelerating rate, and how it will come to an end. After years of thought (since I was 11) I have come up with my hypothesis that time itself is accelerating and slowing down, and has been...

I'm trying to understand what the time dilation looks like when moving through space and then approaching a planet's gravity field. So I have the broad understanding that if you are moving near the speed of light in a spaceship, your clock ticks normal but the clocks on other stationary objects...

Hi! I am really stuck on the concept, wouldn't we not have enough variables? I tried equation the equation for the y of the object to the slope of the hill, but I am missing several variables. Any help is greatly appreciated :) thanks!