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  1. J

    Ball bouncing on a planet (no atmosphere) follow up questions

    This thread will contain several follow up questions, but let me start with the most simple one. Imagine a planet with no atmosphere and a ball in empty space. The ball is dropped on the planet from a certain height and starts bouncing. We ignore friction and consider this to be the fully...
  2. J

    Would this device(pic inside) work for boiling cold water?

    Imagine some giant glass(or other material) dome placed on top of some ocean or lake. Then pump some air out of this dome, until the water level rises a few meters under the dome. Place another dome below the first dome, and repeat the process, resulting in a little less pressure in the second...
  3. J

    B Quantum tunneling - Questions about some pop-science claims

    This might become a series of questions, but let me begin with the most essential one. According to QM/QFT, would it be true that there is a non-zero chance for an object on earth to instantaneously tunnel to the moon for example? Like let's say a paper with a note on it. Could this paper...
  4. J

    Getting energy from deep ocean pressure

    Let's say we would take a pipe made of some very strong material, and connect it to the ocean at the deepest level possible. For example 500 meters. Then we would dig a huge area on land, again, as deep as possible. Lead the pipe to the lowest level of this huge basin we created and then use...
  5. J

    B The perfect relativistic quantum particles simulation

    How would a physicists expect a perfect relativist quantum particles simulation to look like? Can anyone give a description of its functionality? Let's say for example, someone would program a simulation, composed of a 4D space-time diagram. Within this simulation are a large amount of quantum...
  6. J

    B Do particles of a rotating disk just change position or also spin?

    When we rotate a disk, can this process be fully explained by looking worldlines of the particles the rotating disk is composed of, hence their x,y,z,t position "as time passes", or do particles have some kind of "facing direction", hence also spin(not the quantum mechanical notion of spin)...
  7. J

    B Need help with the math for a more advanced Simulation

    In my infamous simulation of the twin paradox, i assume a near instantaneous acceleration, with the results being almost identical with the "real" thing sub some extremely small values which you could not see with the naked eye anyway. But i might want to take the simulation a step further, to...
  8. J

    B DeltaT of clocks at endpoints of a rocket post acceleration

    Following scenario: A rocket measuring 10 lightseconds in length accelerates near instantaneously to v=0.4c. Pre-acceleration two clocks placed at the endpoints of the rocket were synced. What will be the time difference between the two clocks post acceleration? I tried to figure it out...
  9. J

    B Lorentz transformation formulas for arbitrary distances

    In my simulation of the twin paradox, i used the Lorentz transformation formulas to map events from one inertial reference frame into another IRF. Reading through various threads here, i read that spacetime is curved and that space can be considered flat only for small distances. So my...
  10. J

    B Relativistic simulation of charged particles

    Supposed i wanted to do a relativistic simulation of charged point particles moving at different velocities and interacting with each other. My simulation would give me the x,y,z coordinates of each particle seen from an arbitrary observer's point of view, at a given t. The t given however, is...
  11. J

    B Twin Paradox visualized

    I decided to work a bit on my Java program created to visualize the Twin Paradox. It shows two diagrams. One from the perspective of the stay at home/earth twin on the left side and the travelling twin on the right side/diagram. The accelerations are considered to be near instantaneous, hence...
  12. J

    B Energy required to change speed?

    Ok, this will be awkward but i somehow got lost in this thought, For low velocities, the formula for energy boils down to the classical E=1/2m*v^2 So let's say two astronauts A and B are in empty space absent of gravity. B has a jetpack and accelerates to 5m/s which require E=1/2m*v^2=...
  13. J

    B Entangled photons thought experiment

    Following scenario: One million entangled photon pairs are created and are sent to Alice's and Bob's laboratory such that Alice receives 1 million photons(or any other large number) of which each is entangled to one of the million photons Bob receives, their laboratories being at a distance to...
  14. J

    Clarifying entropy

    Considering a closed system with an ideal gas(in a low entropy state) inside, then are following statements correct? The gas is in a certain state we can assign an entropy value to. Let X be the set of all states which are of a lower entropy value compared to the current state. Y the set of...
  15. J

    B Moon base

    Following scenario: 1) Send a few rockets with large payloads to the moon, carrying various parts of a nuclear reactor to be assembled on the moon 2) Use the nuclear reactor to extract oxygen from various materials found on the moon 3) Use the power of the reactor to harvest resources for...
  16. J

    B Clarifying relative velocity

    I have been told that relative velocity can be negative on this forum, so i would like to ask a few questions based on this. scenario 1) Two observers O and O' are facing each other and are approaching each other. O sees O' approaching at v=0.5c and vice versa. The vector of the velocity is...
  17. J

    I Are the Lorentz transformation formulas on wikipedia correct?

    They seem to defy the most fundamental principle of SR. The first postulate/equivalence principle. According to wikipedia, we get Lorentz boost (x direction) and slightly different formulas for the inverse Lorentz boost "This "trick" of simply reversing the direction of relative velocity...
  18. J

    I Proper mapping of the second postulate into math

    The second postulate of SR is telling us that light always travels at C in a vacuum(absent of gravity) measured by any observer independent of the source or inertial frame the observer is measuring the light from. However, light is made up of photons which do not travel like ping pong balls in...
  19. J

    B A little clique "game" in Java - Clique Problem

    For what it's worth, i created a little java program in relation to the clique problem https://en.wikipedia.org/wiki/Clique_problem The idea was, to play around with it and maybe discover some better algorithm than the known ones used to discover all maximum cliques The code is quite small...
  20. J

    Flywheel inside a spaceship experiment

    Given the above setup in this image, there is a fast spinning massive flywheel inside a spaceship. The flywheel is only connected via a lock to a spring. What would happen if the retractable steel wall moves towards the steel ball (purple) which is connected to the fly wheel, so the steel...
  21. J

    Measuring spin on electrons prepared in various directions

    Let's say we have 200 electrons. The first batch of 100 of those electrons are prepared in a way that 50% are UP in the x axis while 50% are DOWN in the x direction. The order is unknown. The second batch of 100 electrons are prepared in the same manner but in the y axis. Bob picks one...
  22. J

    Entagled Electrons - measuring both x and y spin

    According to QM, given two entangled electrons A and B, if you measure the y-axis spin on A to be up, then you know electron B's y-axis spin is down. Also according to QM, if i understood it properly, you cannot then go on to measure the x-axis spin on B, because then you would know both y...
  23. J

    Why does the universe move towards an observer at rest?

    In relativity, we do not talk about just space anymore, but space-time, with time being just another dimension. An observer A at rest in an IRF who considers himself at rest at t=0 x=0, has a far away clock at t=100 for example moving towards him, i would like to say at 1second per second, but...
  24. J

    A gas in a mini universe reaches maximum entropy

    Assuming a mini-universe with the same laws as our current one. A gas within that universe reaches a state of maximum entropy. Would it remain in that state of maximum entropy once it is reached? Maybe the question does not make much sense. In that case, forgive my ignorance. edit: the...
  25. J

    Two Observers with clocks in space moving at vrel relative to each other

    As the title says, imagine two observers with clocks A and B in space which move at vrel relative to each other. Just when clock A passes by clock B, the clocks counter shows zero. Observer A will conclude clock B to tick slower, while observer B will conclude clock A to move slower (both using...
  26. J

    Attempt on Twin Paradox via Minkowski diagrams

    This is an attempt to solve the twin paradox via two Minkowski diagrams with a few questions attached. Note that there might be mistakes in this drawing i will fix in the course of this thread in case someone notices any. First, let me explain the two Minkowski diagrams in the drawing first...
  27. J

    Using length contraction to push a bomb trigger

    Inspired by Aziza's question i came up with a similar, seemingly puzzling question. Imagine a space-platform with a big cylinder on it. The cylinder has a hole drilled in, with a bomb-button at the end of the hole, which would trigger a bomb destroying the whole galaxy. A terrorist is on that...
  28. J

    Lonely Hydrogen Atom in Space (casimir)

    A sole hydrogen atom in a vacuum (negligible gravity). The hydrogen atom has the lowest possible kinetic energy allowed by QM. Given that casimir effects apply... Will the hydrogen atom remain at it's initial lowest kinetic energy state indefinitely or is it possible for it's energy state to...
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