Gravametrics from planets viewed as the source for elliptical decay.
Encke is considered by some to have been a super comet..that spiralled in and was shorn in pieces.Our Earth History a testimony to Encke's power.
Dr's Victor Klube and Napier submit that we will be hit again while transiting accross the Taurid meteor stream. The Stream is likend unto crushed gravel that is delivered for drive ways..lots of consistantly small uniform sizes... with a varied amount of larger rock included. It is the larger pieces of Encke's train that fail to burn up in our atmosphere that have been doing the damage... Tunguska events to Barringer.
An interesting side note...there are positional horizon markings at Stonehenge..some feel this was also part of the design..a way of monitoring the seasons..and the Taurid meteor stream .. that the ancients feared greatly.