Many modern thinkers, on the other hand, think of time as an objective reality that exists statically and through which we somehow pass. In this view there is no past or future. Every moment exists simultaneously but we experience them sequentially.
Somewhat between these two views is the theory that what we call time is a collection of states of affairs that we experience, but that time itself is an illusion.
There's an interesting article on time in Popular Science by astrophysicist Adam Frank who seems to adopt this latter view. Frank presents us with an excerpt from his book About Time in which he advances the interesting theory that time has no real existence and describes the thinking of physicist Julian Barbour in support of his theory:
Julian Barbour’s solution to the problem of time in physics and cosmology is as simply stated as it is radical: there is no such thing as time.There's more on this at the link. Take the time to read it, or perhaps I should say, enter the Now of reading the article.
“If you try to get your hands on time, it’s always slipping through your fingers,” says Barbour. “People are sure time is there, but they can’t get hold of it. My feeling is that they can’t get hold of it because it isn’t there at all.”
Isaac Newton thought of time as a river flowing at the same rate everywhere. Einstein changed this picture by unifying space and time into a single 4-Dimensional entity. But even Einstein failed to challenge the concept of time as a measure of change. In Barbour’s view, the question must be turned on its head. It is change that provides the illusion of time. Channeling the ghost of Parmenides, Barbour sees each individual moment as a whole, complete and existing in its own right. He calls these moments “Nows.”
“As we live, we seem to move through a succession of Nows,” says Barbour, “and the question is, what are they?” For Barbour each Now is an arrangement of everything in the universe. “We have the strong impression that things have definite positions relative to each other. I aim to abstract away everything we cannot see (directly or indirectly) and simply keep this idea of many different things coexisting at once. There are simply the Nows, nothing more, nothing less.”
Barbour’s Nows can be imagined as pages of a novel ripped from the book’s spine and tossed randomly onto the floor. Each page is a separate entity existing without time, existing outside of time. Arranging the pages in some special order and moving through them in a step-by-step fashion makes a story unfold. Still, no matter how we arrange the sheets, each page is complete and independent.
As Barbour says, “The cat that jumps is not the same cat that lands.” The physics of reality for Barbour is the physics of these Nows taken together as a whole. There is no past moment that flows into a future moment. Instead all the different possible configurations of the universe, every possible location of every atom throughout all of creation, exist simultaneously. Barbour’s Nows all exist at once in a vast Platonic realm that stands completely and absolutely without time.
“What really intrigues me,” says Barbour, “is that the totality of all possible Nows has a very special structure. You can think of it as a landscape or country. Each point in this country is a Now and I call the country Platonia, because it is timeless and created by perfect mathematical rules.” The question of “before” the Big Bang never arises for Barbour because his cosmology has no time. All that exists is a landscape of configurations, the landscape of Nows.
“Platonia is the true arena of the universe,” he says, “and its structure has a deep influence on whatever physics, classical or quantum, is played out in it.” For Barbour, the Big Bang is not an explosion in the distant past. It’s just a special place in Platonia, his terrain of independent Nows.