[amelius]

Modern smartphones almost weigh nothing, so I'm wondering why is a VR headset so heavy?

[danielvf]

Glass for the lenses, for one thing.

Another is that the force exerted on you head is roughly weight times the distance that weight is from the centerline of your neck. This multiplier makes stuff hanging out in front of your face much heavier than it would be if were just sitting on top of your head.