“Om namo bhagavate vasudevayah”

As we know, the soul which is the life energy in living beings is eternal. It never takes birth nor does this die(Sbg 2.17,2.20,2.34,2.30). But the other element of life is the Prakrti(material world) which holds the soul and provide a resting place and let it act.
One of the most noticeable phenomena in this material world is the constant change in the state of material body and the biggest among those change is the birth and death. We see an entity existing one time and then it's gone on other time. This forces us to think material objects can be created or destroyed.  But giving a deeper thought we can find it's not. It's only a change or transformation. What we notice as creation, propagation, and destruction of different objects around us is nothing but the transformation of material elements. The collection, interaction, rearrangement and reaction of elements to give illusions of creation and/or destruction.

Taking one example human body.  It appears as a separate entity but in reality its a complex abstraction of elements of nature. It does not come from anywhere outside material nature but within. After so-called destruction, it does not go anywhere but remains in nature. During all such transformation, the total measure of material nature remains the same. Material universe hence is eternal. Shrimad Bhagvad Gita describes this as follows:

Ch13:Sh20
prakritim purusham caiva viddhy anadi ubhav api
vikarams ca gunams caivaviddhi prakriti-sambhavan

In this way, know Prakriti (matter) and Purusha (individual consciousness) to be eternal. Know that the transformation of the body (ksetra) and the three Gunas also produced from the Prakriti(material nature)

Extracting the relevant text from the above translation

“Know Prakriti (matter) and Purusha (individual consciousness) to be eternal”.

As per this Shloka both life energy called as Purusha and material universe called as prakriti are eternal. 

Purusha is a subject of different discussion. In this post, we would discuss Prakriti. 

So prakriti, the material universe is eternal and that means it was never a time when this universe did not exist in the past nor is it going to happen in future that this ceases to exist.  But this universe and everything within it goes through a constant transformation. The second part the Shloka talk of that transformation:

Know that the transformation of the body (ksetra) and the three Gunas also produced from the Prakriti(material nature)

As per this whatever transformation we see in an object is produced from the constant transformation of the material universe. What we see as the creation and destruction of objects and entities is actually the transformation. Similarly, this transformation creates different abstractions at a different time. What we know as an entity or object is a particular abstraction of the material universe. When that abstraction vanishes we know it as destruction or death of the object when some abstraction created out of the transformation of material nature we call it as the creation or the birth of that object. 

From one seed, the tree is created, it grows, gives fruits, wood, leaves, etc. Fruits and sometimes leaves are consumed, wood is used to make furniture’s and after some time it breaks and disintegrates. We human identify them under a different name and see them created or destroyed. But the fact is that it’s all transformation of material nature giving rise to new state and new abstractions. A seed uses the elements of Prakriti (material nature)to grow. After disintegration, it again merges with the Prakriti(matter).
In a similar manner, the human body starts from the elements from parents, it takes other elements from nature and grows. During the lifetime human consumes everything produced from nature and emits wastes back to nature itself. Finally, when life ends, this material body remains here and disintegrate back to its nature. Human body starts and remains. The overall measure of Prakriti(material nature), its mass remains the same. Some of the objects are burnt or transformed in another form to give energy, but then energy is part of the same prakrit(material nature). If we consider the whole material world as one(in chemistry is it called as one system) then it overall mass and measure remain the same, including the energy.

This theory of Sanatan Dharma goes very well with the scientific theories and law. One of the most basic laws of physics the "Law of conservation of mass and energy" confirms this. As per this law mass and energy can't be created nor be destroyed by can be transformed.  Two or more compounds react to give some other substance. As we see, two molecules of Hydrogen when combines with one molecule of oxygen, gives 2 molecules of waters. 
2H2+O2=2H2O
In this chemical reaction abstractions of objects changed, inputs were hydrogen and oxygen produced third substance water. But in the whole process, the mass is conserved. which can be calculated as follows, 
In the above reaction:

2*(2*1)+16*2=2*((2*1)+12)
36=36

Further mass can be transformed to give energy. When we burn wood, the substance wood is gone, producing heat and light energy. There are other kinds of substance called Radioactive substance which loses its mass to give energy.  

Science so far describes the conversion of mass to energy, however, the opposite is not possible. However, Shrimad Bhagvad Gita Chapter 8 explains in clear terms that both mass and energy can be transformed from one to other. mass can be converted to energy and vice versa, energy can also be converted to mass. Let's hope science will be able to convert energy to mass sometime in the future. 

The state of the universe which we see today was not the same billions of years ago and it is not going to be the same billions of years hence. It will look different. But in all situation, the total measure of the universe will remain the same.

This way the Prakriti (material world) eternal. What we see is only the transformation of matter. 

Shri Hari Om Tat Sat”