not to mention the unkown orbits of bodies in the ort cloud only a few bodies have been discovered there and they estimate that there are thousands there the size of pluto. the orbits can take thousands of youears to compleate so you never know what can happen considering that planetary observation is still very promitive. Also you must take inco account of a varied gravitational flux by passing planets on ort cloud objects as well as passing stars.
They all have a gravitational effect on extra-planetary bodies. All it takes is just a tiny tug and its like a pool table on the break and earth is behind the 8 ball.
Any cosmologist or geologist will tell you its only a matter of time.