Theres very little we can say about our physical world with any absolute certainty.
Once upon a time the speed of light was considered an absolute measurement, but in recent years physicists have issued light pulses and microwaves that have travelled much faster than the once universally accepted speed limit.
It used to be that the tiniest building blocks in the universe were atoms, until science proved that atoms were really combinations of electrons, protons and neutrons. Now researchers are looking even deeper, discovering that the trons themselves are made up of quarks that co-exist with mesons.
There are a few laws of motion, gravity and thermodynamics that are pretty solid, and the new math seems to work pretty well, but we still have a lot to learn about world and the complex systems that make our home planet what it is. Some things we may never completely understand.
The problem with this scenario is that people and western societies are wired backwards. Instead of doing things cautiously, living within the ecology until we know its safe to do something, we feel safe doing whatever we want to the planet until science can prove that were doing harm. Science, always constrained by funding and priorities, is left playing catch-up.
The matter is complicated by the fact that science, a constantly evolving field of knowledge and technologies, can never be perfect. If the speed of light and atoms are not absolutes, then what is?
Another problem for science is that results are often open to interpretation, with scientists taking different sides on major issues. Even if the large majority of scientists agree on a principle, a small minority of doubters often on the payroll of the companies most affected by scientific discoveries are given equal footing in debates and tend to get more support from governments. They call it being cautious. As long as one scientists says "no", a theory will never become universally accepted.
Im referring to a lot of different issues, but the most important is the ongoing debate on global warming and climate change.
Climate scientists agree unanimously that greenhouse gas emissions have increased from about 280 parts per million 100 years ago to about 370 ppm today higher than they have been in half a million years or more. They agree that increase in greenhouse gases could result in higher average temperatures by storing solar radiation that would ordinarily be reflected back into the atmosphere. They also agree that, on average, temperatures are half a degree Celsius warmer than a century ago. All of this is easily proven.