Checkpoints have been a staple of video games for decades and are almost as old as video games themselves, but how? These little tiny features have made a huge difference in the way we play games, allowing us to restart at a fair point or reload a checkpoint if we so desire. How, using science, not magic, can I explain the existence of these leaps through time?
To explain checkpoints scientifically you need to assume the existence of an alternative universe where the sapient inhabitants of this cosmos possess the natural ability of premortem transtemporal metempsychosis (PTM). Basically if you die your consciousness is transferred to a moment sufficiently prior to your death to continue and, hopefully, avoid being killed in the same way again.
To unpack the terminology.
"Metempsychosis" is the transfer of a mind from one to another body. The term is often used to describe reincarnation. In this case, the reincarnation takes place in the person's body at an earlier time.
"Transtemporal", naturally, means "across time" and deals with the time travel component.
"Premortem" means "before death" and preferrably the person who has died will want their mind to be reincarnated a reasonably lot earlier than when they died.
For this to be natural process and therefore explicable scientifically, it is not unreasonable that this happens in an alternative universe.
The 'Eve Online' explanation of resurrection after a character is killed is that a clone of the player (with implanted memory backup) is spawned (covered by insurance, naturally) after death. The impact on a society of this way of recovering from death would tend to make people more casual about making life or death decisions, since you can recover from them if you make a mistake.
So your checkpoint is a medical station that grabs a cell sample for cloning and also does a brain scan to back up your memories.
The 'checkpoint' is an on demand, full immersion virtual reality. The mega-computer it is connected to runs a simulation found to be identical to reality in all but an infinitesimal number of instances.
A person pays for the checkpoint and is plugged into the system. They are able to play out choices in the VR, over and over, until they get the desired outcome. At which point the key elements to achieve this outcome are impressed onto both their conscious and subconscious minds, so that the same events occur in reality (within a negligible margin of error*)
*results are not guaranteed in the event of clashing checkpoints or undetectable quantum fissures