Answer:
Open me, and you can't see me without a mirror. Close me and you can't see me at all. What am I?
Sometimes I fly as fast as the speed of light. Sometime I crawl as slow as a snail. Unknown until I am measured but you will certainly miss me when Iām gone.
I am the same written forward backward and upside down.
*forward* *backwards*is what I do all day. I come in all different shapes and sizes. I can be scary and I can calm you down.
I am a shimmering field that reaches far. Yet I have no tracks and am crossed without paths. What am I?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.