Picture a hot coffee. If you leave the coffee on the table and come back to it a few hours later, it will have reached the temperature of the room. This is because of the second law of thermodynamics. The second law of thermodynamics states that in a closed system (i.e. one in which there is no energy being added), the matter and energy will eventually reach its most probable distribution. This is called "entropy".
The universe, much like your coffee, is also a closed system. That means entropy is increasing, and eventually, if left to itself, the universe would suffer what is known as a "heat death". This is actually what forced secular scientists to admit that the universe had a beginning (which they would have known already if they'd just open the Bible).
So, the universe is slowly heading towards entropy, but there is a problem here: Entropy cannot be reversed. In order for our universe to be winding down, something has to have wound it up. What was it? There are three possible answers. The first is that we are so unbelievably ignorant of science that everything we know about thermodynamics is wrong. You can take that route, but I hope I don't need to explain how complex that will be for you. Let's just say when you've re-formed a worldview in about 500 years, come back to me and we'll talk about why Christianity is still the better option.
The second possibility is that our knowledge is right (or at least close to it), but there's some kind of scientific law we don't know about yet, and maybe we'll eventually discover that in the future. This is somewhat less complex than the first option, but it's also rather desperate. You can't argue from what we might know in the future, simply because we don't know it yet.
The third option is by far the simplest. That is, the origin of the universe is supernatural. The existence of the supernatural allows us to comfortably leave all our current knowledge intact, but with the added discomfort of the possibility that the supernatural thing that created the universe might actually be God. This is an uncomfortable conclusion precisely because if God is real, we are accountable to Him, and yet, we have messed up rather spectacularly.
Option 3, being the simplest and most logical, is also the one I must encourage you to accept. This argument, commonly called the "cosmological argument", is but a mere foundation for establishing the existence of the supernatural. However, there is far more evidence besides this, and on top of this, there is also much evidence for Christianity. Though this can be scary for us as sinners, it is also a great blessing, for though God must deal with our sin, He has two options for doing so. The first is to punish us eternally in Hell, but the second, which is certainly His preference (see Ezekiel 18:32 and 33:11), is that we repent of our sins and live. If we choose the latter option, our sins will instead be nailed to the cross upon which Jesus died. He received the full punishment for our sin, and all we need to do to receive that benefit is confess Him as Lord, and believe God raised Him from the dead.