and presumably a presentist would not be ok with “now” meaning “this century”. But if they narrow it down to “the smallest possible unit”, then they’re not talking about the world that we see or act on, right?
From the wiki on the present
As a concept of current time:
The present is the time that is associated with the events perceived directly and in the first time, not as a recollection (perceived more than once) or a speculation (predicted, hypothesis, uncertain). It is a period of time between the past and the future, and can vary in meaning from being an instant to a day or longer.
“The present” raises the difficult question: “How is it that all sentient beings experience now at the same time?” There is no logical reason why this should be the case and no easy answer to the question.
Special Relativity’s “present”:
One has to conclude that in relativistic models of physics there is no place for “the present” as an absolute element of reality. Einstein phrased this as: “People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion”.
Today vs. now:
“Today” signifies a “day” in a 24-hour interval to signify one’s stance within the plane of time, this is contrary to “now”, because “now” has no definite measure for its own duration. On the graph of Space-Time, the present can appear to be infinitely small, or account for a large portion of a sequence.
Thus, if time is a continuum, then the present (depending on context) can be an instant which is infinitely small (but not zero), a second, minute, hour, day(24 hours), month, year etc.
If time is discrete, i.e. there is a quantum unit of time (Planck time), then the smallest present is that interval.
If time is a continuum, it is problematic to demarcate the past/future as distinct realms and if time is discrete, it is impossible. It makes more sense to consider time as a sequence of presents.
However, if one were to take SR’s time as time in reality (as eternalism do), then there is no distinction between present, past or future at all which is counter-intuitive to all conscious human experience of time. This is unacceptable to most conscious humans, notwithstanding SR.
Two questions which arises are:
1. Should conscious humans believe their experience of time or abandon it as an illusion to be discarded for belief in SR’s time?
2. Is SR’s time really the nature of time or is physics simply misrepresenting time by treating it as a dimension like space?