Yes, there was a beginning to time. However, a cautionary note is
Although our psychological sense of past, present, and future is strong, time may not
be a fundamental physical entity at all. Rather, it may simply express the numerical order of
For example, when a photon of light moves from position 1 to
position 2, photon position 1 doesn't exist before
photon position 2 in time, only in numerical order.
In this sense, the universe is timeless even though we use the word "spacetime"
to describe it. It isn't 3-dimensional in space and 1-dimensional in time, but
rather 4-dimensional in space.
Time plays an important role in comparing durations and
describing physical systems but it may just describe how space itself
is quantum-networked and entangled, rather than being something apart
That being said, our real time began when our universe did, in an
inconceivably hot, dense, tiny spot just after the "Big Bang".
It wasn't an explosion in the usual sense of the word but
rather the sudden
appearance of expanding space. Since then, a duration
of about 13.82 billion earth
years has elapsed.
"Big bang" is a term
coined somewhat mockingly by Fred Hoyle, a 20th century English astronomer,
science fiction writer, and big bang denier. In 1948, he argued against a beginning of time, proposing instead a
"steady state" universe with infinite time. He
rejected both the Big Bang theory and the Book of Genesis as
pseudoscience, suggesting a creator.
But the challenge for Hoyle's theory was the observed expansion of our
universe over time, hardly a steady state. To explain the
expansion, which was confirmed in 1927 by Edwin Hubble, Hoyle postulated mini bangs
of creation in between the galaxies—bangs that would keep the outward flow of matter
constant, like a steadily flowing river.
But Hoyle's job got more difficult in the early 1960s
when radio sources were found to be more prevalent in the early
(far away) universe than
in more recent times. In 1963, quasars, which only occur in the distant past, were discovered.
Then, in 1965, observation of the cosmic microwave background (CMB), a radiation
with no discernable source, pretty
much killed the steady state theory. On the other hand, big bang
theory predicted just such a background radiation.
When physicists try to extrapolate backwards in time from the earliest
well-understood state of the universe (a miniscule fraction of a
second after the big bang), they quickly hit a gravitational (i.e. curvature) "singularity" where
classical laws break down. Gravity, density and temperature
become infinite and all spatial dimensions shrink to zero.
To the rescue comes imaginary time, which treats time as a dimension of
space and successfully predicts quantum behavior. The state of the universe
in real time can be calculated from the state of the universe in
What's more, singularities like the big bang don't disrupt the
continuity of imaginary time, and so a beginning to our spacetime
need not violate the laws of physics.
Steven Hawking has shown that the big bang could've been an ordinary point on the 4-D
surface of spacetime, like the North Pole is an ordinary point on the 2-D surface of
The sudden expansion of a singular point and the rapid inflation of the
universe would borrow energy from the gravitational field to create
matter. In imaginary time, no physical laws would be
violated and the gravitational debt wouldn't need repaying until the collapsed end of
In 1994, when a Big Bang renaming contest in Sky and Telescope
magazine failed to pick a winner, Fred Hoyle said "Words are like
harpoons...Once they go in, they are very hard to pull out."