Quiz

The horizon of a black hole is a place where photons can orbit in circular
orbits, just skimming the surface without falling in.
True or false?

If you fall into a black hole,
you will be torn apart at the horizon.
True or false?

You hover just above the horizon of a black hole,
dangling an immensely strong fishing line.
You dip the line through the horizon.
What happens?

You, on the outside, watch a person fall through the horizon of a black hole.
According to you, the infalling person's watch appears to freeze at the horizon.
If you now fall in yourself,
you can see the previous infaller actually pass through the horizon.
Does this mean that the previous infaller's clock suddenly appears to
speed up as you pass through the horizon?

As you fall freely into a black hole,
you see the entire future of the Universe played out before your eyes.
True or false?

As you approach the horizon of a black hole,
your view of the Universe outside concentrates more and more into a tiny
region of the sky just above you.
As you pass through the horizon into the black hole, the view contracts to a
point and then disappears, leaving you in blackness.
True or false?

The orbital period of an object in circular orbit about a Schwarzschild
(spherical) black hole is exactly equal to the orbital period given by Kepler's
third law.
True or false?

The Schwarzschild metric is invalid inside the horizon of a Schwarzschild
black hole.
True or false?

From the point of view of an outside observer,
a star collapsing to a black hole never appears to collapse,
but rather freezes at the horizon.
How then can it be said that the star collapses to a singularity,
if it never appears to collapse even till the end of
the Universe?

If nothing can escape from a black hole,
how can you feel the gravity from it?

From the point of view of an outside observer,
a person falling into a black hole will never actually be seen to fall in,
but will rather appear to freeze at the horizon.
Suppose however that the mass of the black hole is increased
(by other matter falling in), so that the horizon is enlarged.
Will the person then appear to be engulfed by the
horizon?

Xray binaries consist of a normal star overflowing on to a companion
neutron star or black hole.
Is the xray emission Hawking radiation?
