If the bible is not back by science why do Christians have such firm believes.?

Science is the study of the natural universe in natural terms. Supernatural/spiritual realities lie totally outside the realm of science, and science therefore cannot make any valid statements, pro or con, concerning such realities.
born again Christian biologist

Science doesn't explain everything.  The entire concept of 'faith' (by definition doesn't require "proof or evidence") exists because humans cannot be omniscient.  If humans could know all there is to possibly know, there would be no such thing as 'beliefs'.  The acceptance of scientific proof and evidence is, fundamentally, rooted in belief.  Everyone holds their beliefs out of the conviction that they're correct.

The idea that science and faith conflict with each other is a failure to understand both.  Supposing that the entire Bible is meant to be taken literally would suggest that ancient peoples were incapable of expressing themselves in metaphor and allegory.  Material and Christian Fundamentalism are limited constructs resulting in reductionism which ultimately negates itself.  

Both science and religion are in agreement that the "linear" is always a result and effect of the 'nonlinear'; just as the 'emptiness' of the sky allows clouds to pass.  "Sound and motion" are only detectable against the ever-present background of 'silence and stillness.  It is out of 'intangible and formless' thought that ideas arise as "tangible form".  The "physical world" is entirely made of 'nonphysical properties'.

'To exist', fundamentally a nonlinear expression, as energy and matter is made to change form; which suggest that existence is 'Eternal and Uncaused', and not unlike an 'Omnipresent God' without "beginning and end".  Biology confirms that the human body is made of the same elements found in the earth, which isn't any different from the Bible saying, "God made man from "clay/mud/dirt".

The opening passages of the Book of Genesis doesn't explain the "beginning of existence", as the Presence of God would signify that existence, 'already exists'.  What the Bible is describing is the 'origins of form', as God made the heavens and the earth from the formlessness of "darkness and void", before saying, "let there be light".  

Science explains "linear content" (components, specifics, details), and doesn't define nonlinear context (meaning, significance, implications).  Humans have the capacity to intuit and become aware of the things we cannot observe by the effect and influence they have on the things we can (i.e., what is called "dark" matter and energy).  Just because you cannot put 'potential' in a lab and measure it, isn't any reason to suppose "it isn't there".  

It's called 'faith', you ought to try it some time ...................

The bible is a book of faith, not a book of science.

Are science and the Bible compatible? Read here: https://www.jw.org/finder?wtlocale=E&docid=102011049&srcid=share

The bible is more of a history book, not a science book.

Scientism is a cult.

That is because Christians stand on the truth of the Bible, while science is still evolving. Things held as sacred for science 20 years ago have all been superseded by new information they just "discovered." God knew it long ago. 

Didn't you know ? all science is a plot by Satan to undermine faith in god. All those so called facts are nothing more than smoke and mirrors.

its called "FAITH" for a reason. There is 0 evidence/logic