Shinkansen Sway

Shinkansen door

Recently, I went to Japan. One of the highlights was the “bullet train” or Shinkansen. No, it doesn’t travel at the speed of a bullet (much to my dismay), but it’s still fast.

So I was sitting down, enjoying the 2 hour train ride. I can’t read or do much else while travelling (I get headaches), so I closed my eyes to rest… when suddenly the whole train rocked! I flashed my eyes open, and saw another Shinkansen on the right, coming in from the opposite direction. When the two trains “separated”, my train swayed another time.

This happened whenever I travelled by Shinkansen. So I started to keep track. It’s hard, since one never knows when another train will pass by. But I was vigilant. My efforts paid off, and I noticed that my train swayed in a certain direction when the trains meet up. And my train swayed in a certain direction when the trains separated.

Shinkansen sway

So my question to you is, which direction does the Shinkansen sway in, when the trains approach each other, and when the trains separate from each other? Some basic knowledge of physics and a bit of deductive logic should prove useful.