The Royal Institution
If gravitational forces don’t exist, how can you explain acceleration? Fay Dowker answers questions from the audience following her talk on general relativity and the nature of spacetime.
Watch the talk here: https://www.youtube.com/watch?v=XtptrdsToXU
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Fay Dowker is Professor of Theoretical Physics at Imperial College London and works on the problem of quantum gravity. Her research is based on the hypothesis that spacetime is fundamentally granular or atomic, and she has done numerous public lectures.
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So the proposal that the Earth is accelerating upwards at 9.8m/s2 – that presumably extends to our solar system too? And our galaxy? And most everything else we can observe in space? And it's only when objects are temporarily freed from this upsurge, by being put into an independent or free state, that we appear to see them as 'falling down' or subject to 'gravity'? That is one hell of a mind flip!
E = mc2 – interesting if c equals zero.
that last one was a … funny non-answer
So…..when objects are dropped, the tower, the ground and everything else is accelerating upwards at 9.8m/s2: and if two objects are simultaneously dropped from another tower on the other side of the planet, everything is also accelerating upwards – but in the opposite direction. Really?
please add subtitles
so, again, why does the microphone fall downwards every time it's dropped? why doesn't it sometimes fall upwards? because that's its natural path? that doesn't explain anything…
everything touching the ground is accelerating upwards at 9.8m/s squared? wow. that's literally insane.
earth is rotating around sun because of spacetime curvature. Then it should eventually fall at the centre of curve but its not happening. what could be the possible explanation for this?
That last theory was such a load of bull..
lovely answers; if truth is beauty, then this is it.
Well, now if the thing the reality is that the 2 objects falling from the leaning tower of Pisa have no forces on them & that they're absolutely free and that every thing else is in fact accelerating upwards,….. then why don't we start teaching GR to kids of 2nd and 3rd grade??!! why are we still teaching 'em that Newtonian gravity is the way things are??!!!
In a sufficiently small region of space, over a sufficiently small period of time, there exists a frame of reference in which objects which have no forces acting on them will appear to be either stationary or moving at a constant velocity. This is known as an inertial frame of reference. In any other frame of reference, objects which have no forces acting on them can appear to accelerate without a cause. Near the surface of the Earth, from the perspective of someone in an elevator that is in free fall, over a short period of time, objects in the elevator will appear to behave as they would in deep space away from any gravitational influence.
Objects on the surface of the Earth appear to accelerate downwards when let go because we are not in an inertial frame of reference. This is similar to how if an object were let go in a spaceship that was accelerating in deep space, we would perceive the object to accelerate towards the bottom of the spaceship.
In the neighbourhood of a massive body like the Earth, due to it's gravitational influence on space and time, there is no universal inertial frame of reference in which objects with no forces on it would behave as they would in deep space. In each local region of space for a short duration, there exists a frame of reference which approximates to an inertial frame. This is analogous to the fact that when you draw geometric figures in a small region on the surface of a sphere, the properties of the figures are the same as if the figures were drawn on a flat surface.
The lady's phrase that the earth is the one which move or pushed toward the object with acceleration 9.8 m/s bears some weirdness, because she said the object is free no force exert on it, but she did not explain what is that force which drive the earth with acceleration toward the object ?
Dr. Dowker's explanations of the microphone "falling" through spacetime, and her answer of how "everything else is accelerating up rather than the 2 objects accelerating down toward earth" are not good answers. There are unexplained issues in her answers, that make them incomplete.
For example, in the first question about the microphone falling, her answer said that the microphone would move through time, but would ALSO move through 3D space (following the shape of space – which would be curved due to earth's gravity). So if the microphone were stationary in spacetime (not near earth – so not in any curved space), then her answer again says it would "move" through both spacetime — thus moving through time (yes, normal) but it would also move through 3D space. It does not make sense why it would move through 3D un-curved (non-gravitational) space.
funny how everyone is laughing at the answers because that’s exactly what we should be doing
"All the time excists all the time", but practically we can not go back in time and change the past events, for example we can not go back in time to stop the process of trapping electrons to nuclei that composed helium and hydrogen as was the beginning of formation of atoms of lightest and heaviest elements in the universe.
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