A Very fast way of getting from A to B

This one belongs in the "something we could do if we get a quantum leap in engineering" category.

Two places on the surface of the earth, A and B. Dig a straight tunnel from A to B. The earth is a sphere, so this tunnel will be a chord. At both ends it will slope down. Make the tunnel air-tight and remove all the air so it is a vacuum inside. Put a vehicle inside suspended from the sides by a magnetic-induction system like they use in Maglev trains.

Start the vehicle at "A" and let go. There is no friction resistance (not touching the sides) and no air resistance (vacuum). The vehicle speeds up till it reaches the middle and then slows down until it reaches "B".
This is the same as a pendulum, or a children's swing. It comes to a rest at exactly the same height as it started.
Instead of letting it swing back, catch it at "B". The vehicle is air-tight, and you need a docking mechanism at each end to let people get in and out. Then a new load of passengers get in and it swings back to "A" again. You would probably need some propulsion to overcome residual air resistance, no vacuum is ever perfect, and B might be higher above sea level than A. Or just give it a push to start it, like a child's swing.

How long would the journey take?
The answer is just over 20 minutes, regardless of the distance from A to B. I won't burden you with the maths, but it is similar to a pendulum which always takes the same time regardless of the amount it swings, it just goes faster in the middle if it starts higher up.

The occupants wouldn't feel any acceleration. Just like a child's swing, they are in free-fall in the direction of movement, but they will feel varying gravity.

Now all we need is a method of building tunnels hundreds or thousands of Km long, which are air tight and can withstand the pressures and temperatures under the earth's crust.
It's merely an engineering problem!

P.S. I had this idea years ago, I have mentioned it to a few people (usually after a few beers), but I have not seen it anywhere else.

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