Gravity waves were predicted by Einstein back when speculation was rampant about the possible existence of black holes. What makes you think that a device is in our future capable of generating a wave force counterbalancing that generated by a mass the size of the earth. Believe me, were such a method or device concocted, hover boards would be so low on the list of priorities, that few would care or even notice. That’s one of the truckload of inconsistencies with the BTF franchise. Hover boards all over the place while all the cars roll around on primitive wheels.