3. About the Universe
The Universe is commonly defined as the
totality of existence, including planets,
stars, galaxies, the contents of
intergalactic space, the smallest
subatomic particles, and all matter
and energy. Similar terms include the
cosmos, the world, reality, and
nature.
14. About Black hole
A black hole is a region of space-time from
which gravity prevents anything, including
light, from escaping.
The theory of general relativity predicts that
a sufficiently compact mass will deform
space-time to form a black hole.
The hole is called "black" because it absorbs
all the light that hits the horizon, reflecting
nothing.
15. About Black hole
A black hole is a place in space where gravity
pulls so much that even light can not get out.
The gravity is so strong because matter has been
squeezed into a tiny space.
This can happen when a star is dying.
Because no light can get out, people can't see
black holes.
They are invisible. Space telescopes with special
tools can help find black holes.