(Today is Tue 22 02 2022)

Past time of the universe (or multiverse, if the multiverse idea happened to be true) can be divided into days, hours or other units of time.

Let us look at past time in terms of days, and hypothetically assume that there is actually an infinite number of days in the past.

In that case, each day in the past would correspond to a negative integer as follows:

today (22 Feb 2022) = 0

1 day ago (21 Feb) = -1

2 days ago (20 Feb) = -2

3 days ago (19 Feb) = -3

and so on…

So we have these two corresponding sequences:

…., 3 days ago, 2 days ago, 1 day ago, today

….,  -3, -2, -1, 0

Since each day in the past corresponds to one unique negative integer (as per above), to finish going through all the days in the past (one day by one day in succession) would be equivalent to complete the task of counting all negative integers.

But we know for sure that if we count integers one by one in succession, it is impossible to finish counting all negative integers. Even if an infinite or endless amount of time is given to an everlasting counting machine to do this task, it is still impossible to finish counting all the negative integers.

Before today (22 Feb 2022) can arrive, all the days before today need to be finished going through first, one day by one day in succession. If, hypothetically, there is an infinite/endless number of days before 22 Feb 2022, then to finish going through all the days before 22 Feb 2022 is equivalent to the attempt to finish counting all the negative integers: a never-ending task. Just as it is impossible to finish counting all the negative integers, it is also impossible to finish going through all those days before 22 Feb 2022 if there is an infinite/endless number of days before 22 Feb 2022. In such a situation, 22 Feb 2022 would never arrive!

But today (22 Feb 2022) has already arrived. This entails that the number of days in the past is NOT infinite.

The number of days in the past is thus finite. In other words, if past time is divided into days, then the past began with a very first day. If past time is divided into hours, then the past began with a very first hour. The past has a beginning.

Therefore the past time of the universe/multiverse is finite. In other words, the universe/multiverse has a beginning and is not eternal. This entails that someone/something else must have caused the universe/multiverse to begin existing (ie the universe/multiverse was not in existence at all before it began to exist). The universe/multiverse could not have brought itself from non-existence into existence because nothing can bring itself from non-existence into existence. Something/someone else (ie timeless, spaceless, non-physical, etc) already in existence would be needed to cause the previously non-existing universe/multiverse to begin existing.