No assumptions, but repeatedly verified observational experimentation.
See:
SN1987A and the Age of the Universe
and
Does the Speed of Light Slow Down Over Time
Evidence for this flaw and bias?
This paragraph shows a fundamental mis-understanding of science and the scientific method.
Science doesn't prove anything. Leave proof for mathematics and courts of law.
Science provides evidence that supports or contradicts hypothesis. Basically, we come up with ideas about how the world works, test to see if the world does work that way and then confirm or reject the idea depending on the evidence.
The scientific method is a self correcting process. It repeatedly tests its ideas. If new evidence is unearthed, or the old evidence was found to be incorrectly interpreted, then the previous hypothesis is rejected and is replaced with a new one.
If science stopped doing this, it would mean one of two things. Either the entire concept of the scientific method has come acropper. Or we've dicovered all the information in the universe and explained it to an almost perfect degree of accuracy.
Your welcome to your beliefs. You are not welcome to your own facts.
You believe in a God. You believe that God gave you a brain. Do you think that God would be happy with you rejecting knowledge - tested, observed, verified knowledge, earned through centuries of diligent study and rigorous intellectual endeavour - in favour of simple dismissal and falsehoods?