For those trying to find/locate a vortex in order to do physical Time Travel; take a look at these 2 cheap EMF detectors on EBAY...from a theoretical angle, they might be what we need...
Hot Electromagnetic Radiation Detector LCD Digital EMF Meter Dosimeter Tester
Noncontact High Sensitive Electromagnetic Radiation Detector Pen EMF Tester New
Hot Electromagnetic Radiation Detector LCD Digital EMF Meter Dosimeter Tester
Noncontact High Sensitive Electromagnetic Radiation Detector Pen EMF Tester New