Every once in a while, we have a celestial body that passes through our solar system. What would be needed to reel one of these in? Not crashing down to Earth, that would be bad, but say into a high earth orbit (above the satellite belt)?
You could look it up :-) . The basic problem is that it takes a [bleep]-load of energy to force a distant object to stop orbiting way out there and fall towards the sun, or to be exact, towards Earth. It then takes another [bleep]-load of energy to kick it back up to the needed velocity relative to Earth to be able to orbit Earth.
To some extent, you can reduce the energy required by sending it on a slow spiral, as is more or less done when sending probes to Mars, but that leads to tens of years (at best) waiting for it to arrive.
If you're thinking of comets in their extreme elliptical orbits, well, same problem, since their path is nowhere near tangent to Earth's orbit.