There is no absolute truth in science. There are, however, certain features of science that give it a distinctive character as a mode of inquiry. Even if the evidence supports a theory today, later on, new evidence may show that the theory needs revision. A good example of this scientific evolution is the progression from Newtonian mechanics to quantum mechanics. It is speculated that knowledge is recognized as not conclusively established; it may be challenged at any time, especially if it is suspected that its uncritical acceptance may be responsible for inconsistencies subsequently encountered. Albert Einstein explained that "the history of scientific development has shown that of all thinkable theoretical structures, a single one has at each stage of advance proved superior to all the others"
Therefore, science is a process for producing knowledge, and theories are at best approximations of truth. The scientific method depends both on making careful observations of phenomena, and on inventing theories for making sense out of those observations. Change in knowledge is inevitable because new observations will challenge prevailing theories. Irregardless of how well one theory explains a set of observations, it is possible that another theory may be a more appropriate fit to a still wider range of observations. The occasional replacement or refinement of theories, whether new or old, is a continuous process. Scientists assume that even if there is no way to secure complete and absolute truth, increasingly accurate approximations can be made to account for the world and how it works. That is, science is going to continue to change the way we understand the universe, and it will continue to change the way we live.
It's not enough to agree that ‘valid’ or ‘true’ mean different things to different people at different times. Scientists also have to agree on what they mean by them during the application of scientific theories.” Scientific theories are just a set of dogmas or beliefs, or facts, or theories. Nonetheless, facts can be mistaken, scientific theories can be overthrown, but the scientific method reveals an approximate truth that is theoretically neither true nor false. Bias attributable to the investigator, the sample, the method, or the instrument may not be completely avoidable in every instance. As Werner Heisenberg claimed, what we observe is not nature but nature subject to our method of questioning. Of course, scientists cannot proclaim to know absolute truth, but they can explore the question from a scientific viewpoint and see what they find out. Scientists can use scientific methods and techniques to analyse data, organize them in a coherent way, and try to extract an answer or solution.
In the long run, no scientist, however famous or highly placed, is empowered to decide for other scientists what is true, for none are believed by other scientists to have special access to the truth. Science is not authoritarian. That is, there are no preestablished conclusions that scientists must reach on the basis of their investigations. In retrospect, the Newtonian universe was a metaphysical commitment to the existence of a mind-independent reality; the semantic commitment to interpret theories at face value; and the epistemological commitment to regard theories as constituting knowledge of both observables and unobservables. On the other hand, it is argued that quantum mechanics, with its chaotic behaviour, uncertainty, entanglement or "spooky action at a distance" has does more than help to deepen our knowledge of the world and to expand our ability to manipulate it.
There simply isn't a scientific method that scientists always follow that leads them to truth. They never reach a stage where they can unequivocally assert that a theory has been proven true beyond a shadow of a doubt. Scientific theories are adequate instruments for predicting observable phenomena or systematizing observation reports. Scientists may often disagree about the value of a particular piece of evidence, or about the appropriateness of particular assumptions that are made, and therefore disagree about what conclusions are justified. But at the very least, they tend to agree about the principles of logical reasoning that connect evidence and assumptions with conclusions.