# time dilation

1. ### I Calculation of Time Dilation with Online Calculators

I m a noob, I wanted to figure out the time dilation for an observer on earth who passed 50,000 years, and the Traveler at light speed(99.9%) passed ONE DAY. I mean we pass 50,000 years on earth and the Traveler spends One day.Problem is I tried many online calculator, but each one is giving me...
2. ### B Attribution of reference frame

I can't find an answer on my dilettante question about how we attribute reference frame to complex objects, where different parts move with different velocity or where different parts experience different influence of gravitation. For example, we can take a human's body. If we take the full...
3. ### I Issue With Derivation of Gravitational Time Dilation

Why do we use the equation $\frac {1}{2}mv^2 = \frac {GmM}{r}$ to derive potential velocity, and then put that in the Lorentz factor in order to derive gravitational time dilation? Shouldn't we be using the relativistic definition of kinetic energy -> $mc^2(\gamma - 1)$ to derive the...
4. ### I Time dilation basic understanding from different perspective

So I am having some hard time understanding exactly the effect of moving near light-speed on time. Most of the examples mention clocks as a way of measurement but I can understand why would a clock which is a mechanical or electrical device for measuring time would be effected with motion. That...
5. ### How can the time dilation equation explain faster moving clocks running slower?

Since for the two events of Samir starting the stopwatch, and the stopwatch reaching 10.0s, Samir and his stopwatch are stationary from his own frame of reference, I said it was the proper time and that delta t0 = 10s. Then the speed of the moving frame of reference was 0.6c. I thought placing...
6. ### Effect of time dilation on a satellite

I've got the start of a plot forming in my mind, and I'm wondering if it's likely to be supported by physics at all. My basic understanding: when astronauts go to the International Space Station, due to the speed at which it is travelling, time passes ever-so-slightly slower for them. This...
7. ### I Gravitational time dilation and radius

(Apologies I posted this initially as a conversation. Not familiar with the format) I used the ‘gravitational time dilation’ equation to see how the clock rate varies with distance from the center of an object. I got the opposite result to what I was expecting. From Wikipedia; Gravitational...
8. ### I Calculate mass from time dilation

Based on the exponential growth of time dilation 0.0 - 1.0 if given the radius of an object how do you calculate the mass of the object? Time dilation is a function of gravity. Which can be thought of as escape velocity from a gravitational field. So if you have to achieve .866 c to escape...
9. ### B Time dilation and Einstein's theorem

Hello! Einstein's theorem is in the last sentence of the following quote (bold) [1]: "If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its...
10. ### B I got confused about SR after trying to reply to another

So let us say that there are 3 separate alien species that somehow speak and write the same language. Let us say that 2 of these have always lived and died in their spaceships/asteriod ... going at speeds close to that of light. Alien species 3. A3 leaves behind a message saying that at time t0...
11. ### B Re: Absolute Zero Velocity

You may think you've seen this before, since I've seen similar discussions in the archives of this, but I think I've distilled the thoughts down to a couple of facts that contradict the common beliefs regarding relativity. Let me preface this with a basic observation: Lorenz invariance does not...
12. ### I Questions about gravitational effects on the age of Earth's core

The Wikipedia page on gravitational time dilation (https://en.wikipedia.org/wiki/Gravitational_time_dilation) states: "Relative to Earth's age in billions of years, Earth's core is effectively 2.5 years younger than its surface." A clock subjected to less acceleration (gravitational or...
13. ### B Time Dilation

Assumption: Object 1 is moving and object 2 is static. It is impossible to say which object is moving without any reference object 3. There are three scenarios possible. 1. Reference object 3 is at same position in space time with object 2, then object 1 is moving and object 2 is static. 2...
14. ### B Take on Length Contraction at relativistic speeds

Hello everyone and apologize if my questions seem a bit off, please have patience with me. I want to have the following, rather simple, thought experiment. Let's say that we have a moving object O with the proper length L, when at rest. Let's say that object O starts moving at 0.9c (90% the...
15. ### Time Dilation in a Sci-Fi Novel

Super frustrated English major here trying to do calculus! Please help! I'm in way over my head... So, I'm writing this manuscript that involves humans with genetically inherited teleporting abilities. Near the end of the book, my protagonist wants to fling the antagonist close enough to a...
16. ### I Thinking about time dilation

Feynman Lectures 15-4 Transformation of time first para http://www.feynmanlectures.caltech.edu/I_15.html How is it possible that the moving clock slows down and also shows more time elapsed to the man outside?
17. ### I How can light have a wavelength or change direction in SR?

Hi all, I have two questions about light in Special Relativity. (I'm going to pad these questions out with a few statements about my understanding of length contraction and time dilation, so you can see how I currently think about it and clear up any misconceptions if I've got the basic idea...
18. ### I What is the physical cause behind time dilation?

Time dilation can be shown mathematically but what is the physical phenomenon due to which it occurs?
19. ### I Reconciling two observers in two frames

I am not a physicist—not even close—just a guy who, for some crazy reason, decided to try to understand some of the basics of relativity. I’d like to understand them well enough to be able to explain them (correctly) to another lay person. I’m trying to see how much I could explain without...
20. ### I Differential equation from derivative of time dilation

Hi all! I was messing around with the equation for time dilation. What I wanted to do was see how the time of a moving observer $t'$ changed with respect to the time of a stationary observer $t$. So I differentiated the equation for time dilation $t'$ with respect to $t$: \frac {dt'}...
21. ### I C speed and gravitational time dilation

Hi 1-)If an object's total velocity through space-time(four-velocity)is c, for example even we stand still we move with velocity c (through time) and if mass slows down time, can we say mass also increase our velocity in space? 2-) Is Four-velocity magnitude constant in General Relativity...
22. ### A General relativity: time dilation and speed of light

Hello everyone, I'll go straight to the question. The gravitational time dilation is equal to tearth = tspace*sqrt(1 - rs/r), with rs = 2GM/c2. However, the formula for speed of light in gravitational field is equal to v = c(1 - rs/r). My intuition tells me that these two formulas must be the...
23. ### Time Dilation for Moving Rectangle with Clocks at its Corner

1. Homework Statement A rectangular structure carries clocks at its four corners. The clocks are synchronized in the structure’s rest frame, in which it has length L =4ft and width W = 3ft. In our laboratory frame the rectangle is moving in the positive x direction at speed v = 0.8c. As the...
24. ### B Is it really not possible to tell which object is moving?

The Special Theory of Relativity is based on two principles. The first one is, that if you have two objects, then it is not possible to tell which object is moving, and which object is standing still. So someone moving in a spaceship relative to observer, can't say who is actually moving and who...
25. ### B Traveling to Mars and time dilation

If/when we go to Mars how will we deal with time dilation due to the gravitational differences between the two planets?
26. ### I Time dilation vs the Equivalence principle

Some time ago there was a similar thread https://www.physicsforums.com/threads/clock-hypothesis-gravity-time-dilation-and-equivalence-principle.929838/ but what I want to discuss is similar but not the same and I would like to specify my question in such way, that it hopefully wont go sideways...
27. ### B How can I derive the law of composition of velocities?

How can I derive mathematically law of composition of velocities from time dilation and length contraction But please use only algebra .Don't use four vectors and space time diagrams.
28. ### Small Relativity Problem

1. Homework Statement A man is flying with a speed of 0.7c and at a height 1 km. During his flight, he measures the distance between Toronto and Montreal to be 450 km. What is the real distance between them. I don't think the answers are based on real life, they are just examples of places...
29. ### I Length contraction and mass increase in GR?

In special relativity, an object moving at higher speed experiences time dilation, length contraction, and mass increase, compared to an object moving at slower speed. In general relativity, for an object in stronger gravitational field (i.e., with higher acceleration due to gravity), time runs...
30. ### I Redshift and atomic oscillations

My question is very simple (and I assume it has been discussed before but I cant't find the topic): An atom in the Sun emits a photon detected by an observer on Earth. Disregarding uncertainties and experimental problems relating to the movement of the atom (or assuming we could correct for...