beecee Posted January 10, 2018 Share Posted January 10, 2018 5 minutes ago, interested said: Is that due to the movement through space of Uranus, or its spin rate or a mixture both or something else. I would say because Uranus is less dense. Link to comment Share on other sites More sharing options...
Strange Posted January 10, 2018 Share Posted January 10, 2018 1 hour ago, beecee said: I would say because Uranus is less dense. Effectively, yes. Gravitational time dilation depends on gravitational potential. As such it is dependent on the mass of the planet and inversely dependent on the radius. On the other hand the surface gravity varies with mass and (inversely) radius-squared. Link to comment Share on other sites More sharing options...
Janus Posted January 10, 2018 Share Posted January 10, 2018 1 hour ago, interested said: Is that due to the movement through space of Uranus, or its spin rate or a mixture both or something else. The only factor involved for the purpose of my statement is gravitational time dilation. Surface gravity acceleration: g = GM/r^2 Earth = 6.673e-11* 5.97e24/63780002 = 9.7932 m/s2 Uranus = 6.673e-11*8.68e25/255590002 = 8.8665 m/s2 Time dilation factor as measured by distant observer. 1.00000000069 sec passes for distant observer for every 1 sec on the Earth 1.00000000251 sec passes for distant observer for every 1 sec on Uranus. Surface gravity on Uranus is ~90 percent of that of the Earth, but its clock will run only 0.9999999976 as fast as the Earth clock when only taking gravitational time dilation due to the planets' masses themselves into account 2 Link to comment Share on other sites More sharing options...
swansont Posted January 11, 2018 Share Posted January 11, 2018 On 1/5/2018 at 2:08 PM, studiot said: I thought the innovation was that the speed of light was the same for all observers. That was known from Maxwell's equations, once people realized that EM waves were light. The innovation (which I think Einstein thought was an obvious thing to work out, rather than innovation) was in applying it to kinematics. And the other postulate made it clear that you can pick which frame is at rest (or pick any other inertial frame), so it didn't matter how you looked at the setup of a problem. Link to comment Share on other sites More sharing options...
interested Posted January 11, 2018 Share Posted January 11, 2018 Am I correct in thinking that since a photon travels at light speed, and for it time stops, the distance from the photons point of view is zero to any point in the universe. ie the photon is stationery from its point of view because time has stopped for it, and the distances it travels are shrunk, a bit like a muon. Link to comment Share on other sites More sharing options...
Janus Posted January 11, 2018 Share Posted January 11, 2018 8 minutes ago, interested said: Am I correct in thinking that since a photon travels at light speed, and for it time stops, the distance from the photons point of view is zero to any point in the universe. ie the photon is stationery from its point of view because time has stopped for it, and the distances it travels are shrunk, a bit like a muon. No. A photon has no valid frame of reference. It is also meaningless to talk about time dilation for a photon. If you make v=c in the time dilation equation you get T=t/0, and division by zero is undefined and has no solution. Link to comment Share on other sites More sharing options...
interested Posted January 11, 2018 Share Posted January 11, 2018 2 hours ago, Janus said: No. A photon has no valid frame of reference. It is also meaningless to talk about time dilation for a photon. If you make v=c in the time dilation equation you get T=t/0, and division by zero is undefined and has no solution. Are you saying space time does not exist for a photon ? or maybe time dilation does not apply and distances do not appear shorter for particles travelling at or very near light speed. Link to comment Share on other sites More sharing options...
Strange Posted January 11, 2018 Share Posted January 11, 2018 2 minutes ago, interested said: Are you saying space time does not exist for a photon ? or maybe time dilation does not apply and distances do not appear shorter for particles travelling at or very near light speed. No. Just that you can't apply the equations for time dilation etc. to a photon. It is not a valid frame of reference. The mathematics does not work when you try and apply it to a photon. The Lorentz transform only works for things moving at less than the speed of light (i.e. things). Link to comment Share on other sites More sharing options...
interested Posted January 12, 2018 Share Posted January 12, 2018 (edited) 14 hours ago, Strange said: No. Just that you can't apply the equations for time dilation etc. to a photon. It is not a valid frame of reference. The mathematics does not work when you try and apply it to a photon. The Lorentz transform only works for things moving at less than the speed of light (i.e. things). At 99.9999999999999999999999999999999999999999999999999999999999% c it works but at 100% c it does not work. When a photon enters a gas or a crystal and its speed is slowed, does the Lorentz transform then work? EDIT Gravitational waves travel at light speed, are they affected by lorentz transform, I am thinking of entanglement and some gravitational theories Edited January 12, 2018 by interested Link to comment Share on other sites More sharing options...
Strange Posted January 12, 2018 Share Posted January 12, 2018 1 hour ago, interested said: At 99.9999999999999999999999999999999999999999999999999999999999% c it works but at 100% c it does not work. Yes. You can divide by a very, very, very small number but you can't divide by zero. 1 hour ago, interested said: Gravitational waves travel at light speed, are they affected by lorentz transform No. Anything that travels at the speed of light will be invariant (other wise it wouldn't travel at the speed of light in some frames). Link to comment Share on other sites More sharing options...
interested Posted January 14, 2018 Share Posted January 14, 2018 On 1/12/2018 at 9:31 AM, Strange said: No. Anything that travels at the speed of light will be invariant (other wise it wouldn't travel at the speed of light in some frames). I guess (star trek) warp drive is possible then On 1/12/2018 at 9:31 AM, Strange said: you can't divide by zero. Yes I can 1/0 = infinity a number that can not be attained but is very convenient to use in maths. In computing terms you use a very large number to represent the infinity. By analogy it can be equivalent to an short circuit in electrical terms. 0/0 is defined, zero divided by any number is zero. By analogy 0 Volts/0 Ohms = 0Amps -2 Link to comment Share on other sites More sharing options...
Strange Posted January 14, 2018 Share Posted January 14, 2018 31 minutes ago, interested said: 1/0 = infinity Nope. It is undefined. 31 minutes ago, interested said: 0/0 is defined Nope. Link to comment Share on other sites More sharing options...
studiot Posted January 14, 2018 Share Posted January 14, 2018 (edited) 1 hour ago, interested said: By analogy 0 Volts/0 Ohms = 0Amps Actually not necessarily. You can create a thermal drift current yet the voltage and impedance can both be zero. Can we please get back on topic now. Edited January 14, 2018 by studiot Link to comment Share on other sites More sharing options...
Janus Posted January 14, 2018 Share Posted January 14, 2018 10 hours ago, interested said: I guess (star trek) warp drive is possible then Yes I can 1/0 = infinity Nope, because that would mean the infinity x 0 = 1 But infinity x n = infinity So by your argument, 2 x 1/0 = 2 x infinity = infinity and since 2 x 1/0 is the same as 2/0 then 2/0 = infinity and 0 x infinity = 2 1/n is an asymptotic function. its is also discontinuous at n=0 Here you can see that as n approaches 0 from the right 1/n becomes a larger and larger negative number, while as it approaches from the left it becomes a larger and larger positive number. Neither line ever reaches the point where n=0. Link to comment Share on other sites More sharing options...
phyti Posted January 15, 2018 Share Posted January 15, 2018 Infinity is not a number! Link to comment Share on other sites More sharing options...
koti Posted January 15, 2018 Share Posted January 15, 2018 (edited) 21 minutes ago, trevorjohnson32 said: Gee only the friendliest of hospitality1 Why don't you learn something about not being an... I promise I will and everyone will be more kind you (you will be surprised) when you stop posting ridiculous things like: 1 hour ago, trevorjohnson32 said: It is also true that gravity fields will have the same ageing effect as moving through space. I have heard that time dilation is caused by molecular activity that occurs at light speed. This activity has to travel in two different directions at light speed at once causing it to stop? and once the electrons? are stopped they seize to emit light? ...in a relativity forum where people are required a certain rigour which you are as far away from as the nearest pulsar. Gravity in General Relativity is space-time curvature. Gravity does not have an „aging effect” it’s just what happens to space-time when mass/energy is in it. Time dilation is not caused by „molecular activity at light speed” Time dilation is one of the properties of space-time which we observe when mass moves at a velocity to another reference frame - it has nothing to do with „molecular activity”, this is not some mid-evil alchemist mumbo-jumbo, its a well known and tested phenomena. You were also told in that other thread which got locked that a massive object cannot achieve light speed (c) Show that at least you understand anything from what is being thrown at you. Edit: Moderator please feel free to kill my post as several previous posts got killed. Edited January 15, 2018 by koti Link to comment Share on other sites More sharing options...
Phi for All Posted January 15, 2018 Share Posted January 15, 2018 ! Moderator Note Off-topic post and replies to it split to Trash here. This is a mainstream science section. People who understand it seem more than willing to answer questions from people who don't. No one here is willing to discuss beliefs and guesswork asserted by someone who clearly should be asking questions. It's nothing personal, it's science. Off-topic responses will be similarly split. Stay on topic, which is time and speed, and how speed impacts time. Link to comment Share on other sites More sharing options...
interested Posted January 19, 2018 Share Posted January 19, 2018 On 1/15/2018 at 6:46 PM, Phi for All said: ! Moderator Note Off-topic post and replies to it split to Trash here. This is a mainstream science section. People who understand it seem more than willing to answer questions from people who don't. No one here is willing to discuss beliefs and guesswork asserted by someone who clearly should be asking questions. It's nothing personal, it's science. Off-topic responses will be similarly split. Stay on topic, which is time and speed, and how speed impacts time. I am not sure this is on topic, but is related to fore shortening and relativity and how speed impacts gravity. When travelling at near light speed in a straight line time slows or stops and distances appear shorter or none existent, plank length and time perhaps? When travelling around a solar system in a circular orbit at light speed the radius of the orbit must also appear shortened, and to the object travelling at near light speed it would appear closer to the centre of the solar system than observed by those at the centre. Would it experience a greater affect of gravity due to appearing to be closer to the centre? The outer edges of galaxies are moving at around 240km/s the amount of foreshortening they experience will be minimal compared to something travelling at light speed, is this taken into account when calculating the amount of dark matter in the universe. Moving through space affects time and distances. I understand Gravity can be viewed equally as either the stretching of space or space flowing towards an object, it has the same effect. Could space in spiral galaxies be viewed as moving with the galaxies? If this is the case then they would in their own reference frame be moving much slower through space, and may not need DM to explain their movement. If the movement through space affects time and distance, and gravity is the movement of space towards a mass, can space be viewed as moving with a rotating galaxy? Link to comment Share on other sites More sharing options...
Strange Posted January 19, 2018 Share Posted January 19, 2018 38 minutes ago, interested said: When travelling around a solar system in a circular orbit at light speed the radius of the orbit must also appear shortened Length contraction only occurs in the direction of motion. 1 hour ago, interested said: The outer edges of galaxies are moving at around 240km/s the amount of foreshortening they experience will be minimal 0.00003% Insignificant, I would think. 1 hour ago, interested said: Moving through space affects time and distances. I understand Gravity can be viewed equally as either the stretching of space or space flowing towards an object, it has the same effect. Could space in spiral galaxies be viewed as moving with the galaxies? If this is the case then they would in their own reference frame be moving much slower through space, and may not need DM to explain their movement. This is the trouble with thinking that it is caused by "moving through space": it leads to confused ideas like this. It is a relative effect. It is not caused by moving through space, it is caused by movement relative to the observer. Link to comment Share on other sites More sharing options...
StringJunky Posted January 19, 2018 Share Posted January 19, 2018 (edited) 1 hour ago, Strange said: Length contraction only occurs in the direction of motion. 0.00003% Insignificant, I would think. This is the trouble with thinking that it is caused by "moving through space": it leads to confused ideas like this. It is a relative effect. It is not caused by moving through space, it is caused by movement relative to the observer. How about this scenario: picture yourself orbiting a cylindrical mirror such that a light pulse emitted from the orbiter returns on the same path and the orbiter receives the returning light pulse at the same point, having done one orbit. Would there be an anomalous result in the measured distances, having calculated the radius (time taken on light path/2) vs circumference measured by the orbiter? The point of this is that when you calculate the circumference, working from the light signal measurement, it doesn't conform with the circumference measured by the orbiter i.e it will be contracted, so if the radius was calculated from the orbiter it won't match with the measured radius. Hope that makes sense. Which Idoubt it will. It's nearly frying my brain. Edit. Just thought, it can't be a light signal that's released but a massive body (another observer) that is released and returns at the same time as the orbiter. Edited January 19, 2018 by StringJunky Link to comment Share on other sites More sharing options...
interested Posted January 19, 2018 Share Posted January 19, 2018 1 hour ago, Strange said: Length contraction only occurs in the direction of motion. If the direction of motion follows a circle and the length is contracted why is not the diameter of the circle contracted also. If the circumference is shortened then the diameter must also appear shortened unless basic trig falls down under relativity 1 hour ago, Strange said: It is a relative effect. It is not caused by moving through space, it is caused by movement relative to the observer. I think I was talking about the rotation of a galaxy not light. Some galaxies are moving away from us at 3 c and life in those galaxies goes on as normal, because all things are relative within those galaxies. If space is viewed as moving with them I do not see any change, in your relative perspective. Space contracts and expands due to gravitational waves, if it is viewed to flow like a big sea of vibrating strings , and it was rotating in the same direction as a spiral galaxy made up of vibrating strings, the centripetal forces would be due to objects moving with respect to the space the planets exist in would it not? Is it permitted to use vibrating strings instead of Quantum fluctuations and excitations Link to comment Share on other sites More sharing options...
StringJunky Posted January 19, 2018 Share Posted January 19, 2018 (edited) 13 minutes ago, interested said: If the direction of motion follows a circle and the length is contracted why is not the diameter of the circle contracted also. If the circumference is shortened then the diameter must also appear shortened unless basic trig falls down under relativity That's what I'm trying to get at: whether relativistic effects will skew the results of the two observers. when they later compare. Edited January 19, 2018 by StringJunky Link to comment Share on other sites More sharing options...
Strange Posted January 19, 2018 Share Posted January 19, 2018 35 minutes ago, StringJunky said: Would there be an anomalous result in the measured distances, having calculated the radius (time taken on light path/2) vs circumference measured by the orbiter? You would find that the ratio of radius to circumference was no longer equal to pi. Weird, huh? 17 minutes ago, interested said: I think I was talking about the rotation of a galaxy not light. And I am just pointing out that the length contraction and time dilation is not inherent on the movement of those stars around the galaxy, it depends what you measure relative to. Compared to other stars orbiting with them there will be (approximately) no relative motion and hence no length contraction. You cannot ascribe length contraction as being caused by "movement through space" because that leads to logical contradictions. (Actual logical contradictions, not just "it doesn't make sense".) 1 Link to comment Share on other sites More sharing options...
koti Posted January 19, 2018 Share Posted January 19, 2018 1 hour ago, Strange said: You would find that the ratio of radius to circumference was no longer equal to pi. Weird, huh? To visualise what Strange wrote above, a black hole with a circumference of a few miles can have a radius of thousands or even millions of miles due to extreme space-time curvature. Link to comment Share on other sites More sharing options...
interested Posted January 20, 2018 Share Posted January 20, 2018 (edited) Light is blue shifted and red shifted depending on if the source is moving away from you or towards, if it is blue shifted its frequency appears higher, and it has more energy, gravity waves travel at light speed, if a planet is moving towards you, is the gravitational intensity greater ie does gravity experience a form of blue shift and red shift. Could this effect the strength and or focus of gravity orbiting a planet. 20 hours ago, koti said: To visualise what Strange wrote above, a black hole with a circumference of a few miles can have a radius of thousands or even millions of miles due to extreme space-time curvature. Edit Are you meaning lensing or distance to the bottom of a trough, or gravity well if you observe a circle on 2 D space PI D applies. Nothing weird about it. However if the length of your ruler changes over a stretched surface then yes I get what you are saying, the ruler gets longer towards the middle of the circle in a gravity well, or stretched space. Edit But wouldnt spaghettification of your ruler inside a black hole cause the distance to be shorter to the centre of the BH Edited January 20, 2018 by interested Link to comment Share on other sites More sharing options...
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