I can actually tell you more about the nature of what science is;
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To me, humans usually apply fallacious concepts without their own awareness.
Science usually goes through 3 stages to determine a scientific truth,
1) Observation
Science is basically dealing with a set of rules behind a repeating pattern. Observation is achievable basically because the pattern itself can be repeated infinitively. Say, you can observe how the earth revolving around the sun because the number of times the earth revolving the sun is infinitive.*
2) Formulation
Through the possibly infinitive observations, you can develop theories about how it repeats. You can then try to quantitatively describe how it repeats, say, using a formula.
3) Prediction
Prediction is to put your quantitative descriptions (formulated rules) into tests. If they predict correctly, the set of rules discovered/formulated by you is considered a truth (a formal scientific truth). If the prediction fails or doesn’t fail within an acceptable variance (say, due to equipment capability limit), the set of rules you developed is considered falsified.
To simply put a set of rules behind a repeating pattern is considered "proven" when the prediction of the pattern using this set of rules doesn't fail.
For an example, water dissolves into hydrogen and oxygen. This holds true no matter what. That is, you make a prediction (that water must dissolve into H2 and O2) before each and every experiment and that your prediction will never fail. You deserve a Nobel Prize shall your this prediction actually fails.
A human brain thus realizes/recognizes that it is a truth as the numerous predictions never fail.
This is the nature (predictability and falsifiability) of what science is.
*
As for gravity, the related laws are proven as its behavior is repeatedly predictable. However, we don't know yet the true nature of gravity. Plus that we don't have a united theory (super theory) for the 4 known field theories. I believe that what limits us to explore further is that we cannot penetrate into other time-space dimensions to observe, formulate and predict the outcomes. We are confined within a 3D ball-like universe. On the other hand, even when one day we discovered the true nature of gravity and we developed a super theory which works for all the field forces, it won't falsify today's gravitational theory as the theory is considered proven. There will be a paradigm shift though. Just like the discovery of relativity is not a falsification of the Newtonian laws, it's just a paradigm shift. The Newtonian laws stand by themselves under a certain paradigm where they can be repeatedly verified through their predictability.