The current expansion phase is about 13.7 billion years old. What, if anything was before that is unknown. At this point, we don't even know if 'before' is meaningful here.
I agree, many “unknowns” but still not science, agree?
No.
Science have been able to detect and measure the earliest photons, known as Cosmic Microwave Background Radiation (CMBR), first from radio telescope at Bell Laboratory in 1964. Since, then as better technology developed and advanced, we get increasingly better and more detailed measurements of CMBR, and space telescopes, starting with COBE (Cosmic Background Explorer, 1989-1993), then WMAP (Wilkinson Microwave Anisotropy Probe, 2001-) and Planck (2009-2013) have allow science to calculate the universe age, with greater precision.
The CMBR has been measured to 13.7 billion years ago. In the Big Bang timeline, that's 377,000 years after the Big Bang.
377,000 years marked the beginning of Recombination epoch. This is when ionised hydrogen and helium atoms became stable electrical neutral atoms. The became neutral atoms, when electrons bonded with the positive-charged hydrogen and helium nuclei.
Before the Recombination epoch, the younger universe was in a hot plasma state, which made the universe before Recombination epoch opaque. We cannot detect earlier light than the CMBR because photons quickly get reabsorbed by plasma state of hydrogen and helium nuclei.
The electrons bonding with atomic nuclei (during the Recombination epoch) have several effects upon the universe.
- It made universe transparent, and therefore observable.
- Photons (CMBR) was now able to free travel through space without getting reabsorbed by nuclei.
- The Recombination epoch paved the way for development of large structure formations, in this case, the formation of the earliest stars and galaxies, about 150 million years after the Big Bang.
My point is that, science don't have the technology yet, to observe beyond the Recombination epoch. The earlier universe is currently unpenetratable, due to the hot plasma state of the universe, acting like Event Horizon.
The universe is definitely older than the Recombination epoch, because the CMBR is already about 13.7 billion years old.
That radio telescopes and space telescopes equipped with instruments that can detect anisotropic cosmic radiations, showed that the bi Bang is a well-tested theory.
Can we learn more about the universe? Definitely. Are there still mysteries in the universe that scientists don't know about? Of course.
You have to remember that the cosmology is ongoing project,and we don't know all the answers, but science has only just started.