Well, do you know how we "see" black holes? The "body" of a black hole is nothing but darkness, but we see the radiation given off by the mass accelerating towa

Well, do you know how we "see" black holes? The "body" of a black hole is nothing but darkness, but we see the radiation given off by the mass accelerating toward the black hole event horizon that can often reach significant fractions of c. Given the high mass density of a planet compared to space, a massive amount of hard radiation will be released. Also the relative velocities of earth and the black hole is extremely important. Depending on the relative velocities, it's possible that the blackhole simply gets lodged in the earth's core and we're 100% dead, another 100% dead scenario is if it plunges in, out the other side, but then "falls back" for another pass and so on.