831
xkcd #3084: Unstoppable Force and Immovable Object
(imgs.xkcd.com)
Title text:
Unstoppable force-carrying particles can't interact with immovable matter by definition.
Transcript:
[An arrow pointing to the right and a trapezoid are labeled as 'Unstoppable Force' and 'Immovable Object' respectively.]
[The arrow is shown as entering the trapezoid from the left and the part of it in said trapezoid is coloured gray.]
[The arrow is shown as leaving the trapezoid to the right and is coloured black.]
[Caption below the panel:] I don't see why people find this scenario to be tricky.
Source: https://xkcd.com/3084/
That's pretty simple, if there is any matter they could both interact with in the way, it would be converted to energy and either expelled to the side or shunted to another dimension.