On BSD you use FIBs to declare process specific routing tables, on Linux you use firewall marks to do the same, then just route all trafik through the vpn uplink and deny any other.

“They used physics to do it” is just a laughably pathetic motivation. Nobel hated “abstract wankery” or “intellectual masturbation” and wanted to promote results which benefitted the common man and society directly. This is incidentally also why there doesn’t exist a Nobel prize in economics. The nobel prize comitte has since long abandoned Nobel’s will in this matter and it is anyones guess what the order of magnitude of spin Nobel’s corpse has accumulated.