These aren't the kinds of questions most scientists worry about, but they are reasonable questions for the non-science layperson to ask. Any science educator should have answers for these questions. For one of those answers, hop on over to David Hone's blog and check out his post The Science Network. It's a good description of why science works, and why it's relatively safe to trust established scientific theories. It also describes (though, not explicitly) why breaking science news should be taken with a grain of salt: it's the process of checking and re-checking that refines scientific knowledge and weeds out bogus ideas.
Here's my condensed (ok, ok ... cherry-picked) version if you'd like a taste before clicking that link up above:
A good scientist knows what she knows and knows what he does not know. [They have] a good idea of [their] strengths and weaknesses and [their] areas of expertise and ignorance.While I'm at it, this perspective on how science works also highlights the near impossibility of conspiracy among scientists, especially given that nearly all researchers love to call out others on major mistakes. It's perhaps that impossibility that makes cartoons like this so amusing?
... crucially, I also know people who are good at the things I’m not good at and are not good at the things I am good at... Together we have breadth and depth.
...[Importantly], it allows us to cross check and revise our collective work and have confidence in what we are doing across the whole of science, even, or perhaps particularly, when we have little or no understanding of that field individually...
In this sense then, scientists are not so much a group of individuals as a cohesive whole. There are, obviously, errors made (occasionally profound ones) but this colossal network of research ideas and analysis does produce a singular, and generally very reliable, whole. I may not understand astrophysics, but I recognise and trust the methods used to generate the data, the analyses and the people behind it. So can you.