Cosmic atom (Georges Lemaître) is in some ways better expression than Big Bang (Fred Hoyle) because the study of the origins of the largest things known to man, galaxies and supergalaxies and entire cosmos, is actually study of the smallest things known to man - cosmology and astrophysics of early universe are essentially nuclear physics.
Scientists have figured out the mathematics from the first milliseconds on but before that, in the beginning, defies science.
Was everything in a dot? What kind of dot and from where that dot??
Since there is no matter, no energy, nothing, Positivism and Logical Positivism tell us that we have no language to say anything meaningful about the initial state. Some say that there was nothing at all - but we have no ability to comprehend a state where there is nothing at all. It defies the structures wired into our brains.
Bible says that there was someone, the same One who is much later called the God of Israel.
Take a few good educated guesses: Hartle-Hawking initial state, string landscape, brane inflation, string gas cosmology, the ekpyrotic universe.
Things are not made at all easier to science by the realization that only about four percent of the energy density in the universe is visible by radiation. 22% is the rest is some strange hypothetical dark matter that we feel only by its gravitational effect. And a whopping 74% of the rest of the universe is dark energy, whatever it is. Or some even stranger component distributed diffusely in the space that we currently have no idea about.
Surely, CERN accelerator and FERMI accelerator and other fancy instruments humanity is able to build with enormous sums of money will bring much more information about the earliest universe.
So today scientists do not really know what most of the universe is made of. They have beautiful theories about dark matter and dark energy that we are unable to observe directly and intensive research goes on. Some day we will know more. But far behind us are those happy days of human optimism and faith in almighty Science when all explaining Newtonian physics and a small nice universe was known to us - or at least would soon be. That cultural and scientific era of optimism was crushed by us humans ourselves in the First World War.
So ... the astrophysicist and the cosmologist has most advanced tools of exploration to study that small fraction of the universe that is visible to us through some sort of radiation. The rest they examine in their brilliant minds with highest level of mathematical thinking.
But the zero moment, the initial state, seems to be even beyond our thinking.
after the Beginning
Plank epoch was not a very long epoch. In our clocks it lasted for
Before you have counted the digits in that number (43) Planck epoch is already ancient history.
"If supersymmetry is correct, then during this time the four fundamental forces — electromagnetism, weak nuclear force, strong nuclear force and gravitation — all have the same strength, so they are possibly unified into one fundamental force." (quote)
So scientists are not all that far from the Beginning. And yet they are very far from it.
In fact, zero moment seems to be beyond scientific exploration and something that we cannot comprehend with our brains. We are creatures and find it hard to even imagine when there is nothing created and time itself does not exist.
So we wish the scientist great success in solving these most fundamental issues.
And we believe.
We believe according to the Bible that there was nothing visible. We do not know if there was something but we do believe that there was someone.
Everything was One.
His people, the Jews, insist on telling the world that also today He is One.
And the Christians have pretty strong writings by Jewish people who believe that Jesus is the King of Israel:
"Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear".
Heb 11:3 KJVA
That someone has made Himself known to us as God of Israel whom the Christians call the Holy Trinity, Father, Son and Holy Ghost, who were all present before the creation of the world.
And cannot be studied scientifically.