Fellow student seems to be chasing rainbows. Should I step in? I am currently writing my bachelor's thesis, and share advisors with a fellow student, who is also working in the same office as I am. We exchange daily about our progress.

I am under the impression that his work is going nowhere. He is working on a topic that has no previous work available, and according to him, direct verification on whether his research is useful is not possible. An indirect approach using yet another students' algorithm showed worse results in combination with the work of the student in question. To acquire this information, both students spent a large amount of time that could have been spent towards writing their theses.

He is somewhat backed up by his (our) supervisor, but I feel this is largely because the supervisor wants this research to end up in a peer-reviewed publication, even though there are no results that suggest the research is valid or useful in any way yet.

I have the impression that continuing this path will worsen the thesis outcome for my fellow student, as he is facing a deadline to turn in his thesis, but spends a lot of time trying things out and interpreting essentially bad results to show something positive.

Since I sympathize with him, I would like to intervene and talk bluntly about the issues written out above. I do understand, however, that it is not my place to correct him, as we are at the same stage of our careers, and I am about as inexperienced as he is. In addition, since our supervisor has a different opinion and more experience, it could very well be that I'll be wrong in the end.

What interaction, if any, is ethical and reasonable for me to engage in?

I imagine this sort of thing happens more often, even with more experienced academics, as confirmation bias seems to be a somewhat common issue.

How are similar problems usually handled in academia? Are people like my fellow student in question left alone to their own judgment, or do co-academics talk them out of seemingly bad ideas? Do people criticize each others' research a lot?
Which kind of interaction, if any, is ethical and reasonable for me to engage in?


Discuss your concerns with your peer. 


  How are similar problems usually handled in academia? 


Through discussion.


  Are people like my fellow student...left alone to their own
  judgement, 


Largely, yes, but...


  or do co-academics talk them out of seemingly bad ideas? 


...in an ideal world colleagues (who they've discussed their work with) will try to bring them back on track.


  Do people criticize each others' research a lot?


Yes! Constructive criticism is central to the research process (unconstructive criticism is unfortunately common).