Introduction
Is the Universe Eternal? Has the universe always existed, or did it have a beginning? Thanks to advancement in science, we now have very strong reasons to believe the universe is not eternal. In this article, we will explore 5 powerful scientific reasons that prove the universe had a definite beginning in the past.
Why does it matter?
Some may ask ‘why does it matter if the universe had a beginning? ’ If the universe is not eternal, then it came into existence for a reason. This raises deep questions about the origin of universe, purpose of our existence and meaning of our life. It’s not just science; it’s about our very existence itself.
5 Scientific Reasons to believe universe had a beginning
Let’s look at 5 compelling scientific reasons that lead us to the conclusion that universe is not eternal.
The Law of Thermodynamics (Entropy)
The Second Law of Thermodynamics states that Energy spreads out and gets used up over time. It’s like a battery. The more we use it, the weaker it gets until it finally dies. If the universe were eternal, that is, had no beginning and existing forever in the past, it would have already run out of usable energy by now. But stars are still shining, galaxies are still forming, and life still exists. This means the universe cannot be infinitely old. It must have had a beginning with fresh energy.
The Age of the Universe
Modern science has actually measured the age of the universe. Using data from the cosmic microwave background radiation (the “afterglow” of the Big Bang), scientists have calculated that the universe is about 13.8 billion years old.
If universe had no beginning, how could it have an age? For example: If you were never born, would you have an age? Of course not. The fact that we can measure its age so precisely means it had a definite beginning point in time.
Expansion of the Universe
In 1929, astronomer Edwin Hubble discovered that galaxies are moving away from each other. This showed that the universe is expanding — like a rubber band being stretched.
Now imagine pulling a rubber band. The more you stretch it, the more tension builds up. You can’t keep stretching it forever. At some point it either snaps or you have to let go, and it will shrink back.
In the same way, scientists say the universe can’t keep expanding forever without a beginning. If we “rewind” the expansion backward, the universe would shrink smaller and smaller, like a rubber band returning to its original shape, until everything comes back to a single point. That’s what scientists call the Big Bang, which marks the origin of space, time, matter, and energy.
Just like a rubber band cannot stretch infinitely without starting from somewhere, the universe cannot expand without having a beginning.
BGV theorem
In 2003, three scientists, Borde, Guth, and Vilenkin, published a famous result in cosmology. It’s called the BGV Theorem. They proved that ‘any universe that has been expanding on average throughout its history cannot be eternal in the past. It must have a beginning.’
The theorem proved in that paper is amazingly simple. Its proof does not go beyond high school mathematics. But its implications for the beginning of the universe are very profound. . . . With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape: they have to face the problem of a cosmic beginning.
Alex Vilenkin, Many Worlds in One (New York: Hill and Wang, 2006), pp.174-76.
The Impossibility of Endless Pasts
Let’s say the universe had no beginning. That would mean there are an infinite number of past days before today. To reach today, we would have to “live through” an infinite number of days in the past. This is impossible, because you can never complete an infinite journey.
For example: imagine trying to count all the negative numbers starting from -∞ … -3, -2, -1, 0. You would never get to zero. Similarly, if the past days were infinite, you would never reach today. But we experience today! That means the past cannot be infinite and the universe must have had a starting point.
Summary
- Thermodynamics → Energy would have run out if the universe had no beginning.
- Age of the Universe → Having a measurable age (13.8 billion years) proves a definite beginning.
- Expansion → Rewinding expansion leads to a single starting point.
- BGV Theorem → Any universe expanding on average cannot be eternal. It must have a beginning.
- Infinite Pasts → Today would never arrive if we had infinite days in the past.
All these points lead us to the conclusion that universe is not eternal and it indeed had a beginning.
Frequently Asked Questions (FAQ)
Did science prove the universe had a beginning?
Yes. Science provides strong evidence points to a beginning. The Big Bang theory and the Borde-Guth-Vilenkin theorem both show the universe cannot be eternal in the past.
What about the multiverse? Could it be eternal?
Even if multiple universes exist, the points discussed above, such as the BGV theorem, apply to the multiverse as well. This means that even a multiverse cannot stretch back infinitely. It too must have a beginning.
If the universe had a beginning, what caused it?
Science shows that the universe had a starting point. So, the cause itself must lie beyond space, time, and matter. To know more about the cause and origin of the universe, click here.
