air
We cannot see the wind because air is homogenous and transparent. Wind does not reflect or block the light arriving at the eyes of a human being. We can only feel the presence of wind by the movement of thins around us like the trees, clouds and our bodily hairs.
I have no idea where in the world you are and so cannot guess as to what triangle shapes are around you. A triangle is a plane area surrounded by three straight lines.
Using a mirror or any form of TIR yes you can, but unfortunately the human eye cannot see around corners.
Gravity is a force that cannot be seen directly, but its effects can be observed. We can see the effects of gravity when objects fall to the ground, planets orbit around stars, or when tides are created in the oceans due to the gravitational pull of the moon.
No, according to traditional Christian beliefs, souls in heaven cannot see us on Earth.
The air.
According to the Bible, the dead cannot see the living.
Look, God is always with us. The only thing is we cannot see Him.
A model
model
none of us can know we cannot see your television
Two things you can feel but not see are emotions and air. Emotions like love or fear are internal experiences that are felt but not visible. Air is all around us, but we can only feel its presence, not see it.