If the universe had a beginning, then how can it be infinite?
Universe is finite. .of course universe has boundary and edges... Only our observable universe is infinite.. There is different between them..... But interesting thing is whatever we do we can't reach boundary of universe.. Because space is expanding more than speed of light. .Just imagine, you wanted to set you foot on the boundary of the universe, so you invented a spaceships which cruise at the light speed and you started you journeys... Universe started expanding 13.7 billion years ago.... So you need to travel 13.7 billion years to catch the boundary.. After13.7 billion years the boundary will be still a ahead of you at distance of 13. 7 billion light years... So you will never reach the boundary..
Does the universe have an infinite past?
We do not know answers to questions like what happened before big bang which makes it difficult to assert if the universe is infinitely old. When cosmologists talk about universe it is the observable universe. Any physical theory is required to be verified by observations hence from a physical point of view we can only talk about observable universe. We know that this universe which can be explained by laws of physics is finite and has a finite age. In fact we can calculate the age of an expanding universe given that we know what the universe is made of and what is the proportion.If the universe was completely filled with dark energy we would be living in an infinite universe ie a universe with no beginning and no end. But the universe as we know today is made of two more components matter and radiation (which is why we exist in the first place). This universe theoretically should have a finite age.It was observational evidences that first suggested that universe should have a finite age. Yian had pointed out one such observation in his answer below.Our theoretical understanding is pretty much in tally with many astronomical observations and the theory of finite expanding universe is widely accepted among cosmologists. It is well accepted that universe has a finite age (When the definition of universe is a physical one).
Does infinity have a beginning?
If your infinity refers to time, it had a beginning. Time is a measure of motion. The earth moves around the sun (year). The moon moves around the earth (month). The earth spins (day). Atomic time is measured by the movement of atomic particles in an atom, such as cesium. Before there was any movement, there was no time. Prior to the big bang, there was no movement and thus no time. If all movement ceases to exist in the far future, time will end.
Did the Universe Have a Beginning?
Science proves that the universe has a beginning because if the universe goes back an infinite number of years then to reach the time period we are at now (2010) the universe would have to have went threw time an infinite number of years. a synonym can be used to clarify this, if a car is 10 feet from my self then i am also 10 feet from the car correct, if the universe is the car and you are the year 2010 and the distance between you too is infinite then the car could never reach you, picture a timeline, it has a beginning and a end, if it has no beginning then the end could never be reached, but if the universe has a beginning then it would only have to travel an X amount of years to reach 2010 which is possible.
Did the universe have a beging or is it just a chain of infinite events?
That's a very good question and one which science is struggling to answer. You should read Stephen Hawkin's "A History of the Universe."
Is the universe infinite or finite? If it's infinite, how can it have a beginning?
There are two ways in which the universe could be infinite. Temporal and Spatial.If the universe is Spatially infinite then either it has always been infinite, or in the past it underwent some infinite expansion. Both seems rather impossible, but we don't know. Note however that the whole 'beginning of the universe' and 'big bang' only says something about our visible universe, which is finite alright.The universe could also be Temporally infinite, that simply means that, no matter how much time you'd wait, there's always a universe. This seems pretty possible and is, iirc what current theories predict. You can compare this with half of a line: lines are infinitely large, but half of a line still has one end point, the beginning in this case.In the end, we don't know. We're simply limited in the knowledge we have, but also in the knowledge we can have. The entire universe is several times bigger than the visible one, and it's altogether possible we'll never be able to gather enough data to exactly pinpoint whether it's finite or not.