[xenophiles]

Others have pointed out how harmless a black hole would be (1. According to all theory it would evaporate so fast we probably wouldn't even be able to detect it, much as we'd like to, 2. even if it could endure it would almost certainly have enough residual velocity to leave Earth and never come back, and 3. even if it stayed here it would be so tiny and weak it wouldn't do much of anything).

As for strange matter, last time I studied that theoretical stuff, the theory was that it could absorb normal matter and grow only under conditions of very high pressure: the sun's core wouldn't be enough.

[Jeff F]

For their entire life, the earth, sun and all other observable bodies have been bathed in cosmic rays vastly more energetic than anything the LHC will ever produce (as much as 10^21 eV compared with less than 10^12 eV for the LHC). So far we have managed to avoid being destroyed by strangelets, micro black holes, and other fantastical hobgoblins.

The cosmic ray background extends to nine orders of magnitude more energetic than the worst the LHC will dish out, and is only six orders of magnitude away from the Planck energy.

[richardtavor]

No, it would probably only last a few seconds, and would send the researches back in time for a few seconds, and they would be asking “this is strange, but it seems like De Ja Vu all over again.”