Title: Relativistic Time – Exactly What Is Time?
Headings: Relativistic Time
Relativistic Time
Space-Time
Time Dilation
Gravitational Time Dilation
Twins Paradox

Content: both the past and the future are simply “there”, laid out as part of four-dimensional space-time, some of which we have already visited and some not yet. So, just as we are accustomed to thinking of all parts of space as existing even if we are not there to experience them, all of time (past, present and future) are also constantly in existence even if we are not able to witness them. Time does not “flow”, then, it just “is”. This view of time is consistent with the philosophical view of eternalism or the block universe theory of time (see the section on Modern Philosophy ). According to relativity, the perception of a “now”, and particularly of a “now” that moves along in time so that time appears to “flow”, therefore arises purely as a result of human consciousness and the way our brains are wired, perhaps as an evolutionary tool to help us deal with the world around us, even if it does not actually reflect the reality. As Einstein himself remarked, “People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion”. However, if time is a dimension, it does not appear to be the same kind of dimension as the three dimensions of space. For example, we can choose to move through space or not, but our movement through time is inevitable, and happens whether we like it or not. In fact, we do not really move though time at all, at least not in the same way as we move through space. Also, space does not have any fundamental directionality (i.e. there is no “arrow of space”, other than the downward pull of gravity, which is actually variable in absolute terms, depending on where on Earth we are located, or whether we are out in space with no gravitational effects at all), whereas time clearly does (see the section on The Arrow of Time ).