Read about time | 265 Discussions | Page 1

  1. N

    Position vs Time graphs

    The graph: 1) $$v_1 = \frac{\Delta{x}}{t} = \frac{5 - 3}{3} = \frac{2}{3}$$ $$2 = \frac{\Delta{x}}{t} = \frac{4 - 0}{5 - 1} = 1$$ $$\frac{v_2}{v_1} = \frac{1}{2/3} = \frac{3}{2} = 1.5$$ 2)Points of intersection of the lines with the x-axis: ##I## (0; 3) and ##II## (0; -1), thus $$\frac{2}{3}t...
  2. AlfSalte

    B What happens to time as space is expanding?

    I have one question I hope someone here can answer for me. Relativity theory tells us that space and time are sort of the same thing, as a spacetime. So when space is expanding, what happens to time? I find it hard to believe that time is somehow unaffected by the expansion of space, so while...
  3. M

    Please help me understand time dilation

    Good day. I have read many books, forums, and articles, and watched many youtube videos, all in an effort to understand special relativity and time dilation. Or rather, more precisely, trying to find a valid explanation that does not result in contradictions and paradoxes, and if it does, one...
  4. adafus

    B Are time and light at the same speed?

    I'm probably am wrong in this but i guess you guys could light me in this one
  5. thegroundhog

    B “Direction” of time

    I've seen a lot of Youtube clips and listened to podcasts recently on cosmology and quantum physics and something that has come up frequently that I don't understand is descriptions of time. Specifically Sean Carroll on various podcasts and Carlos Ravelli (when he finally got to the point). 1...
  6. VarnaiKristof

    B Can our movement in time be decelerating?

    Is it theoretically possible that the whole universe is decelerating in time? My question originates from the discovery, that objects further away accelerates away faster. Is that acceleration measured from us or from the center of the big bang?
  7. M

    What’s a good name for a phenomenon where time moves differently?

    I’m trying to come up with a term to describe how time moves slower or faster in different places of a galaxy. I’m trying to explain how in Star Wars, things seem to move differently for different characters in separate locations. I’m trying to argue that Han limping to Bespin took “longer” than...
  8. E

    Question about variations of the Sun's path over long periods of time

    Hello. I am a filmmaker writing a screenplay and I am in need of technical support to validate a method being used in the film. I am going to post this in the Earth Science forum but I'll copy it here, in case anyone reading this might know. Thank you all! "I am wondering if shadows cast...
  9. L

    Which way is correct and why?

    I get two different answers even the area of the graph. I think there is something wrong with the equation I constructed for average speed part. I know the method 1 is correct. But I'd like to know why the average speed cannot be used. And why I get two different areas for the graph Thank you
  10. TammyTsang

    Engineering Scaling of units for equations of motions

    In the picture, there is a problem where the t is in units of square root(l/g), and V in square root(gl) I am wondering 1. What it means when time is in units other than time? Does it mean that when solving I have to take time/squareroot(l/g) 2. How did they get square root(l/g). Thank you...
  11. M

    A Vast distances=Time travel?

    If you could instantaneously teleport from Earth to a planet in the Andromeda galaxy; when you arrive, would you be in what to Earth would be the distant past? Meaning that when you looked at Earth, you would be seeing what it looked like millions of years ago?
  12. D

    Getting Force with distance, mass and time

    I'm sorry but I can't even attempt this question since I'm pretty much clueless, I got the notes but I don't understand them.
  13. velocityoverrtime2

    Pendulum projectile problem

    Tried to find time in seconds in order to use the formula d=vt and find the distance in the x plane in which the target must be placed, to no avail.
  14. S

    Battery Charge and Discharge Time Calculations

    I am performing some calculations but struck with confusion whether I am doing it correct or wrong due to contradictions of these calculations on different calculators websites. I hope here someone will help me with the validation of my calculations. Battery Capacity = 150 Ah Battery...
  15. entropy1

    Is the past in MWI unambiguous?

    I couldn't match this question with another topic, so I made a new topic. Suppose we have past H and present P at a certain moment. In present P a measurement is made. For matter of speaking we adopt MWI, so we have the two measurement outcomes A and B diverging in two realities A and B in...
  16. Prabs3257

    Kinetic energy as a function of time

    I got acceleration by dividing force by m then replaced a by dv/dt and then integrated it to get velocity as a fxn of time and hence got kinetic energy but problem is my ans does not match with any option can someone please compare their ans
  17. W

    I Entanglement/correlations in time

    From what I know about (bi-partite) entanglement, we write the combined Hilbert space as a tensor-product of Hilbert spaces for a particle at ##A## and a particle at ##B##, ie ##\mathcal{H} = \mathcal{H} ^{A} \otimes \mathcal{H} ^{B}##. If the particles share a non-separable state, they are...
  18. menniandscience

    B Retarded and advanced potentials

    "of the two types of solutions which the Maxwell equations yield for the wave equation, the retarded and advanced potentials, only the retarded field seems to have a physical meaning," let's start please with basic (and detailed as possible for the knowledgable layman! p.s-which equation is...
  19. W

    I Time-reversal symmetry in QM

    I've bumped into a few interesting papers talking about time-reversal symmetry in QM (eg: but I can't seem to wrap my head around the concept. 1) What does it mean for one to say that standard QM isn't time-reversal symmetric? Does this have to do with the...
  20. A

    Time it takes to swim across a river

  21. R

    I Frequency to temporal period conversion

    I am working with signals that look like the following. The curve has the same form in both frequency and time domain. I am trying to calculate the ratio of two distances: The distance between two adjacent red "x"s (known as the free spectral range (FSR)). The distance between two adjacent...
  22. Samwell

    Force as a function of time

    Hello, I have the force defined as a function of time, where F=A-Bt and A=100N, B=100Ns-1. I have to determine, how long it will take for object to stop, if t0=0s and v0=0,2ms-1 and mass of the object is m=10kg. Can somebody please help me with this, because I'm having hard time with this task.
  23. J

    B How physics equations transform under inverse of parameters

    It is obvious that there is a one-to-one relationship between real numbers (defined to include infinity) and their multiplicative inverses (assuming we map the inverse of zero to infinity and vice versa). Thus, one should be able to replace the distance between two points in space with it's...
  24. mousheng xu

    I Is time bidirectional in a black hole?

    I just watched a youtube video saying that somewhere in a blackhole, time is bidirectional (can go to the future and can go to the passed), but space is one-directional. Any introduction material on this subject? Thanks in advance!
  25. Abhishek11235

    Calculating elapsed time in different frames

    The attempt is above
  26. Ryu

    Theoretical Higher spatial dimensions question

    So I had a topic which I would like to fact check from an informed scientific source. Basically there is an argument about whether or not an object that naturally exists in a fourth dimensional space, would by default have more than countably infinite times the energy of a 3 dimensional Object...
  27. B

    Relative velocity between a Bus and a Car

    for part 1: t= d/s = 9000/13 = 692.31s for part 2: What i am unsure about is wether or not this is after the initial observation or exactly what they are asking honestly. so i found the relative velocity of the bus to the car and vice vera and came up with: t=d/s = 9000/4 = 2250s however i dont...
  28. A

    What do you think of this FTL/time travel engine?

    So, I have this idea for the FTL engine for artistic purposes and I wanted to ask if anybody could point out it's flaws. I would greatly appreciate if you were willing to discuss them further. It is just a rough summary, so if you want me to disclose more details, ask away. The idea is as...
  29. W

    Retarded time calculations: Electrodynamics

    Homework Statement A positive charge ##q## is fired head-on at a distant positive charge ##Q## that is held stationary. It comes in at speed ##v_0## and comes to an instantaneous halt at distance ##r_f## away from Q. What is the amount of energy radiated due to acceleration in this time...
  30. L

    Loading/charge time of an electromagnet

    Hej Guys, Did anyone see anywhere an equation to this? If nothing else then a loading time formula for solenoid would do. Thank you!