Genady Posted February 21, 2023 Share Posted February 21, 2023 1 minute ago, mistermack said: Well, either the observer accelerates, or a free falling object accelerates. But to decide which is happening, I'm looking at which is experiencing a force. In general relativity, gravity is not a force. But the observer IS experiencing a force through his feet. So from a GR point of view, the observer is the one that is accelerating, and hence the surface that he's standing on is likewise accelerating. So the OP is pointing out that the surface of the Earth is accelerating upwards, away from the centre, all over the world. So here in the UK, the surface is accelerating upwards, and on the opposite side, in New Zealand it's also accelerating upwards but in the opposite direction because the Earth is a ball. In the thread that I linked, I was trying to argue the notion that this happens because space (or the element of space that determines the position and motion of inertial frames) is constantly falling into massive bodies, whether they are a black hole, or a planet like the Earth. I see. Sorry, but it is not how GR works. Link to comment Share on other sites More sharing options...
MigL Posted February 21, 2023 Share Posted February 21, 2023 (edited) If you are in free fall are you experiencing a force ? No. And an accelerometer attached to you will not show any acceleration. If something stops your free fall, will you experience a force ? Most definitely. If that something is the ground, it will stop you dead ( literally ). Even if you are not falling, but simply standing on the ground, you will feel a force equivalent to your weight. And yes, that is GR. Edited February 21, 2023 by MigL Link to comment Share on other sites More sharing options...
Genady Posted February 22, 2023 Share Posted February 22, 2023 30 minutes ago, MigL said: If you are in free fall are you experiencing a force ? No. And an accelerometer attached to you will not show any acceleration. If something stops your free fall, will you experience a force ? Most definitely. If that something is the ground, it will stop you dead ( literally ). Even if you are not falling, but simply standing on the ground, you will feel a force equivalent to your weight. And yes, that is GR. Yes, what you say is GR. What I replied to above, is not. Link to comment Share on other sites More sharing options...
swansont Posted February 22, 2023 Share Posted February 22, 2023 11 hours ago, Willem F Esterhuyse said: The Earth is a ball. How can one side and the opposite side accelerate upwards (their local "up"). ! Moderator Note You have not established that this happens. You can’t ask how something happens while begging the question of whether it does. Link to comment Share on other sites More sharing options...
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