The Reality Check Episode 55

Time Travel+Multitasking+Well Starseeing Myth

Is time travel possible?

Part 1: 

So, is time travel possible?

We know that in theory is it probable to go into the future by traveling at the speed of light. But, there is no way to go back in time. 

Some theories, most notably special and general relativity, suggest that suitable geometries of space-time, or specific types of motion in space, might allow time travel into the past and future if these geometries or motions are possible. In technical papers, physicists generally avoid the commonplace language of "moving" or "traveling" through time, and instead discuss the possibility of closed timelike curves, which are world lines that form closed loops in space-time, allowing objects to return to their own past. There are known to be solutions to the equations of general relativity that describe space-times which contain closed time like curves, but the physical plausibility of these solutions is uncertain.

Relativity states that if one were to move away from the Earth at relativistic velocities and return more time would have passes on Earth than for the traveler, so in this sense it is accepted that relativity allowed "travel into the future". On the other hand, many in the scientific community believe that backwards time travel is highly unlikely. Any theory which would allow time travel would require that problems of causality be resolved. The classic example of a problem involving causality is the "grandfather paradox": what is one were to go back in time and kill one's own grandfather before one's father was conceived? But some scientists believe that paradoxes can be avoided, either by appealing to the Noviko self-consistency principle or to the notion of branching parallel universes.

Stephen Hawking once suggested that the absence of tourists from the future constitutes an argument against the existence of time travel-a variant of the Fermi paradox. Of course this would not prove that time travel is physically impossible, since it might be that time travel is physically possible but that it is never in fact developed; and even if it is developed, Hawking notes elsewhere that time travel might only be possible in a region of space-time that is warped in the right way, and that if we cannot create such a region until the future, then time travelers would not be able to travel back before that date, so "This picture would explain why we haven't been over run by tourists from the future." Carl Sagan also once suggested that possibility that time travelers could be here, but are disguising there existence or are not recognized as time travelers.

However, the theory of general relativity does suggest scientific grounds fo thinking backwards time travel would be possible in certain unusual scenarios, although arguments from semiclassical gravity suggest that when quantum effects are incorporated into general relativity, these loopholes may be closed. These semiclassical arguments led hawking to formulate the chronology protection conjecture, suggesting that the fundamental laws of nature prevent time travel, but physicists cannot come to a definite judgment on the issue without a theory of quantum gravity to join quantum mechanics and general relativity into a completely unified theory.

Multitasking

Part 2:
So, is multitasking efficient of not?
Human multitasking is the performance by an individual of appearing to handle more than one task at the same time. The term is derived from computer multitasking. An example of multitasking is listening to a radio interview while typing an email. Some believe that multitasking can result in time wasted due to human context switching and apparently causing more errors due to insufficient attention. Other research illustrated our bains are capable dealing with certain 'dual multiple tasks' at the same time.
Because the brain cannot fully focus when multitasking, people take longer to complete tasks and are predisposed to error. When people attempt to complete many tasks at one time, "or rapidly between them, errors go way up and it takes far longer-often double the time or more-to get the jobs done than if they were done sequentially." This is largely because "the brain is compelled to restart and refocus". A study by Meyer and David Kieras found that in the interim between each exchange, the brain makes no progress whatsoever. Therefore, multitasking people not only perform each task less suitable, but lose time int he process.

Science Myth of the Week:
Can you see stars during a bright day at the bottom at a well?
Of course not! Just blocking your peripheral vision doesn't mean you can see stars.