The photon sphere is a sphere above the event horizon in which light orbits the black hole.
One possible indicator that Earth is not a sphere is the perception that the horizon appears flat when observed from ground level over long distances. Additionally, some flat Earth proponents argue that lack of noticeable curvature in the horizon suggests a non-spherical Earth.
Simply divide the mass of the black hole by the volume contained within the event horizon. This is fairly simple for a typical black hole, since the event horizon will approximate a sphere whose radius is the collapsed object's Schwarzschild radius.
A great circle is a circle on the surface of a sphere that has the same center as the sphere, while a small circle does not share the same center as the sphere. Great circles have the largest circumference of all circles on a sphere, whereas small circles have smaller circumferences. The equator is an example of a great circle on Earth, while lines of latitude other than the equator are examples of small circles.
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass; whereas, the capitalized term Equator refers to the Earth's equator.
Earth is not a perfect sphere; it is slightly wider across the equator than it is from pole to pole, but that difference is less than a percent of Earth's average diameter, too small for the human eye to notice.
The photon sphere of a black hole is a region where light can orbit the black hole before being pulled in, while the event horizon is the point of no return where nothing, not even light, can escape the black hole's gravitational pull. The photon sphere is closer to the black hole than the event horizon.
Sphere is whole a hemisphere is not
A hemisphere is half a sphere
The escape velocity is affected by altitude for any celestial body; the further away from the mass, the lower the escape velocity from that point. At the event horizon, the escape velocity is the speed of light. Within the photon sphere but outside the event horizon, light paths not pointing outward will intersect the event horizon. At the photon sphere, a notionally tangential light beam would ideally remain in a perfectly circular "orbit" around the black hole (although, traveling in a geodesic, the light beam will be only traveling straight as far as it's concerned, space itself is bent).... outside the photon sphere, the escape velocity continues to fall with distance.
A sphere has 0 vortex and a cylinder has 2 faces
They are very different, as a square sphere is impossible. The difference is that a square pyramid exists, whereas there's no such thing as a square sphere.
Give a chance
A cube is a three dimensional square, and a sphere is a three dimensional circle.
Literally they both mean ball (orb from Latin, sphere from Greek).
A sphere to a cone is the same as a circle is to a triangle but they are both 3 dimensional.
Because the earth is a sphere. The horizon is the curvature of the earth (or other planet) as it falls away from you.
A sphere is round - like a tennis ball. A torus is ring-shaped - like a donut !