>To my knowledge, one person and one experiment (usually, except where the product is purely mathematical) is enough to propose a new theory (but also to refute an existing one).
To my knowledge theories proposed that way in modern science aren't taken seriously and in our present time are not the norm for any recent major scientific discoveries or research. Those days are long past. New science is done in expensive labs with very expensive equipment and gets funded by grants. The Alvarez Hypothesis was possible because of cutting edge nuclear science that could identify the iridium. LIGO, and every space science and astronomical discovery are driven by really expensive ever growing scopes. In astronomy, chem, physics, molecular biology, paleontology, et al today you'll need an expensive lab and very large grants to do cutting edge work. At this point we're building colliders many kilometers in length. Modern Science is a product of well funded labs with staffing and equipment funded largely by research grants. There are cases in domains like macrobiology where individuals could do field work and find a new species, but the domains where the individual scientist is doing meaningful work are dwindling to none, and you should update your model of how modern science actually operates and is funded, it's interesting.
This isn't an argument in favor of scientific consensus. There's no straight path between expensive, collaborative research/science and scientific consensus. If anything the units of science have moved from individuals to teams acting as a body. But this isn't scientific consensus.
To my knowledge theories proposed that way in modern science aren't taken seriously and in our present time are not the norm for any recent major scientific discoveries or research. Those days are long past. New science is done in expensive labs with very expensive equipment and gets funded by grants. The Alvarez Hypothesis was possible because of cutting edge nuclear science that could identify the iridium. LIGO, and every space science and astronomical discovery are driven by really expensive ever growing scopes. In astronomy, chem, physics, molecular biology, paleontology, et al today you'll need an expensive lab and very large grants to do cutting edge work. At this point we're building colliders many kilometers in length. Modern Science is a product of well funded labs with staffing and equipment funded largely by research grants. There are cases in domains like macrobiology where individuals could do field work and find a new species, but the domains where the individual scientist is doing meaningful work are dwindling to none, and you should update your model of how modern science actually operates and is funded, it's interesting.