If they found the actual time chemical make up or cosmetic diagnose for example. Theoretically understand how to manipulate it only back in time, as my theory going forward is far superior more dangerous if you fuck with the idea of time travel. Reason being is theoretically there is nothing scarred in the time continume forwardly, so yea...

Say these crazy willing to die for the sake of science theoretically gain the cosmetic diagnosis and make up of time. They theoretically manipulate going back words in time. My theory is they would have to be stable and not move to even exist on a past time event, and theoretically they may not even be able to be present in the area they even start and end. Basically they would maybe able to get readings but that might be it, than theoretically they may have to reverse there manipulation out of the past in their designated line of travel.