FOLLOW THESE STEPS
Either go stand in a wide open field or the highest spot you can find. (Preferably evening or night)
Lay flat on your back as comfortable as you can. Do not bend your knees.
Face 90 degree skywards and make sure you do not see or be distracted by other images around you.
RESULT
You will feel like falling into the void (which is the sky).
You will lose your sense of gravity. Because we usually feel gravity below our feet and our body weight and perceiving gravity forces and activities before us, we cannot help to feel the sky is a straight path.
Do you know the saying, "If you stare at the abyss, the abyss stares back at you."
*most people will feel it.
*it's scary at the same time.