funker Posted March 8, 2017 Share Posted March 8, 2017 (edited) I am no scientist I just don't know where to ask this silly question that has been on my mind. I made an illustration, but cant find any way to upload to the forum. The link is below http://tinypic.com/r/29clzrd/9 Any feedback would be awesome. Luke Edited March 8, 2017 by funker Link to comment Share on other sites More sharing options...
EdEarl Posted March 8, 2017 Share Posted March 8, 2017 (edited) Light is energy. However, heat energy does not move at the speed of light via convection or conduction, it moves slower than the speed of light. Heat in the form of infrared is photons, the same as visible light except lower frequency. Edited March 8, 2017 by EdEarl Link to comment Share on other sites More sharing options...
Phi for All Posted March 8, 2017 Share Posted March 8, 2017 I made an illustration, but cant find any way to upload to the forum. The energy in the stick propagates through a solid much slower than the speed of light, so it's far from instantaneous. 2 Link to comment Share on other sites More sharing options...
funker Posted March 8, 2017 Author Share Posted March 8, 2017 Thank you for your fast reply!! Bare with me if I sound all over the place. So my illustration in the link above was the easiest way I could get my words across. So my real question is if I was playing a game of pool, the pool stick is an extension of my arm in which my energy is being transferred to the ball. The second the pool stick tip touches the ball my energy is transferred. Lets assume my pool stick is 100% solid and it reached from Earth to Mars. If I was to nudge the pool stick from here on earth wouldn't the pool stick tip near mars move instantly? If yes, would this energy transferred from my nudge here on earth be fast than light? Luke Link to comment Share on other sites More sharing options...
Lord Antares Posted March 8, 2017 Share Posted March 8, 2017 (edited) There is not pic so I will assume it's what Phi posted. No, the stick would actually move at the speed of sound, much slower than c. It was covered pretty well in this thread: http://www.scienceforums.net/topic/103327-pushing-a-light-year-long-stick/#entry973284 So no, it isn't instantaneous. Edited March 8, 2017 by Lord Antares 2 Link to comment Share on other sites More sharing options...
funker Posted March 8, 2017 Author Share Posted March 8, 2017 (edited) Thanks No Phi managed to get my image up...lol Edited March 8, 2017 by funker Link to comment Share on other sites More sharing options...
KipIngram Posted March 25, 2017 Share Posted March 25, 2017 funker, let me try to give an "inside view" of what's going on in the stick. You referred to it as "perfectly solid," but that's where you're getting off track. What the stick really is is a 3D "grid" of atoms / molecules. For simplicity, just imagine that it's a nice regular grid and that you're hand is pushing the back end of the stick rather than holding it in the normal manner: Hand | | | | | | | | | | 8-ball In that depiction each | character represents a one atom/molecule "slice" of the stick. The atoms/molecules in the slice are connected to one another via chemical bonds, and the slices are each connected to their neighboring slices by chemical bonds as well. These chemical bonds behave sort of like springs - they try to maintain a natural separation distance between the atoms/molecules. So when your hand pushes on the leftmost slice, that slice moves to the right. That "compresses the spring" between the first and second slices. That causes "the spring" to push the second slice to the right, which compresses the "spring" between the second and third slices. The process repeats all the way down the line until finally the right-most slice is pushed to the right. This process is actually how force is transferred to the 8-ball as well; the right-most slice pushes the 8-ball atoms/molecules it's in immediate contact with to the right, which compresses chemical bond springs inside the 8-ball - eventually you get the whole 8-ball into motion. Previous replies made reference to the speed of sound - that's the speed with which this spring compression wave moves through the material. That's why there is a speed of sound - it's calculated from the nature of the atoms/molecules in a material (their mass, primarily) and from the strength of the chemical bonds connecting them. Hope this helps. Basically, what you need to know here is that there is no such thing as a "perfect solid" as you phrased it - no such thing as a perfectly rigid extended object. 2 Link to comment Share on other sites More sharing options...
ravell Posted April 23, 2017 Share Posted April 23, 2017 And how would it be in case of very big masses M1 = M2, suspended on a weightless rope supported in rolls in a very wide arrangement, as on the sketch: O’’’’’’’’’’’’’’’’rope’’’’’’’’’’’’’’’’’’’’’’’’’ O I I M1 eg. D ≥ 3000 km M2 Whether, at the moment of cut off the mass M1, both the masses M1 and M2 will fall at the same time to the ground? Link to comment Share on other sites More sharing options...
KipIngram Posted April 23, 2017 Share Posted April 23, 2017 (edited) In any experiment you set up on non-relativistic scales it will look that way - to a very close approximation they'll fall together. On the other hand, with a long rope like you've indicated (why not make it even longer, to make it more clear), they would not. The change in tension of the rope at the cut has to propagate to the other end, and that takes time. You just can't expect the intuitions you've developed living in the world of short distances and small speeds to apply to situations far, far outside your experience. Say you added two more pulleys, lower and right next to each other, and arranged for the masses to be immediately next to each other (the rope would make a triangle then). Make your rope a light year long instead of just 3000 km. Then when you cut off M1, it will fall immediately. But M2 wouldn't fall for a year or more. And of course this is neglecting all the practical problems, like rope sag and so on. The tension wave will propagate through the rope at a speed governed by the rope's mass per unit length and tension. But no matter what rope parameters you invoke, that speed can't exceed the speed of light, because the internal atomic construction of real rope won't allow that. Edited April 23, 2017 by KipIngram 1 Link to comment Share on other sites More sharing options...
imatfaal Posted April 23, 2017 Share Posted April 23, 2017 ! Moderator Note Hijack by quickquestion asking what energy is - and trying to understand equations for KE and PE moved to its own thread. Please stop hijacking stuff. here is new topic http://www.scienceforums.net/topic/105090-what-is-energy-split-fro-can-energy-move-faster-than-light/ Link to comment Share on other sites More sharing options...
ravell Posted April 23, 2017 Share Posted April 23, 2017 In any experiment you set up on non-relativistic scales it will look that way - to a very close approximation they'll fall together. On the other hand, with a long rope like you've indicated (why not make it even longer, to make it more clear), they would not. The change in tension of the rope at the cut has to propagate to the other end, and that takes time. You just can't expect the intuitions you've developed living in the world of short distances and small speeds to apply to situations far, far outside your experience. Say you added two more pulleys, lower and right next to each other, and arranged for the masses to be immediately next to each other (the rope would make a triangle then). Make your rope a light year long instead of just 3000 km. Then when you cut off M1, it will fall immediately. But M2 wouldn't fall for a year or more. And of course this is neglecting all the practical problems, like rope sag and so on. The tension wave will propagate through the rope at a speed governed by the rope's mass per unit length and tension. But no matter what rope parameters you invoke, that speed can't exceed the speed of light, because the internal atomic construction of real rope won't all that. Thank you very much for your explanation. Link to comment Share on other sites More sharing options...
studiot Posted April 23, 2017 Share Posted April 23, 2017 (edited) This video shows brilliantly that effects take time to travel through a body from on end to the other. With thanks to the member who originally brought this video to my attention. My apologies I have forgotten who you are. Edited April 23, 2017 by studiot Link to comment Share on other sites More sharing options...
KipIngram Posted April 23, 2017 Share Posted April 23, 2017 studiot: Oh, NICE! I just showed that to my kids, and they had a blast. Link to comment Share on other sites More sharing options...
Delta1212 Posted April 23, 2017 Share Posted April 23, 2017 This video shows brilliantly that effects take time to travel through a body from on end to the other. https://youtu.be/uiyMuHuCFo4 With thanks to the member who originally brought this video to my attention. My apologies I have forgotten who you are. That was me. Thanks for posting it because it saved me the trouble of going back to find that post. Link to comment Share on other sites More sharing options...
KipIngram Posted April 23, 2017 Share Posted April 23, 2017 Delta1212: Brilliant work! Taking science and presenting it in a way that flips a kid's lid is no small feat! Link to comment Share on other sites More sharing options...
imatfaal Posted April 23, 2017 Share Posted April 23, 2017 That was me. Thanks for posting it because it saved me the trouble of going back to find that post. http://www.scienceforums.net/topic/103611-speed-of-light-and-action-at-a-distance-question/#entry974748 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now