Because this is how science has always been done, it's just visible on twitter now. Someone submits a paper to be published. A few scientists look it over and check for basic correctness. Then the paper is published and people read it. If the paper is interesting, they start talking about it. They use the breakroom, email, twitter, facebook, science journals, backs of envelopes, and anything else that's convenient. This conversation about a paper is a critical part of the community absorbing a new piece of evidence. From these conversations, subsequent experiments are planned and published and science keeps moving forwards. These conversations are not as formal as a journal publication, but they are much more formal and structured than laypeople usually realize. Comments are worded in particular ways, and only certain kinds of objections make sense. Proving things about nature is an excruciating task that requires an enormous level of care and evidence.
