#### DaveC426913

Gold Member

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Someone has naively calculated the speed of the object at a ridiculous number - a fraction of the speed of light!

I'm pretty sure their error is that they are not taking into account the drop off in g as your distance from Earth's centre decreases. (i.e. they don't realize it, but they're actually calculating the speed of a ball falling towards an

*Earth-mass black hole with zero radius*).

So, what is the velocity of the ball as it passes through the centre of the Earth (ignoring all the usual factors: vacuum, Earth's rotation, etc.)?

Thx.