The history of science is replete with discoveries that were considered socially, morally, or emotionally dangerous in their time; the Copernican and Darwinian revolutions are the most obvious. What is your dangerous idea? An idea you think about (not necessarily one you originated) that is dangerous not because it is assumed to be false, but because it might be true?
It does not necessarily have to pertain to science, but can be a social idea, philosophical, economic or what have you.
I'll start with a simple one, which I call:
"The Gradual Extinction Of The Human Race As We Know It.
In the 21st century, science will move forward in many areas, one of which is bio-genetic engineering.
As of this writing, there are many genetic screen tests that can be performed on fetal humans to determine a probability percentage for certain diseases. In fact, science can now preselect the sex of a child depending on the desires of the parents:
http://www.fertility-docs.com/fertility_gender.phtml
Soon, certain diseases or deficiencies will be not only detected, but removed before birth or even before conception. As well, there will come the ability to pre-select dominant traits such as eye and hair color, and following that, the ability to select much more, including attributes such as appearance, build, and perhaps even intelligence and natural propensity for certain abilities.
Essentially, society will, within a few decades at the very least, have the ability to create a designer human.
This is an idea which is described fairly well in layman's terms with the movie; "Gattaca".
http://www.imdb.com/title/tt0119177/
As technology in this area advances, it will be preferable to produce designer offspring, if for the very least to enhance the child's ability to succeed in what will surely be the most highly competitive global marketplace ever seen by mankind.
Genetic modification will become normalized and common place, and one fateful day, there will be a human produced with more that 1% differences in their DNA structure than in normal "unaltered" humans, which will render them incapable of reproducing with normal humans in a natural way. This child, will no longer be human. This child can not longer be classified as "Homo-Sapien" but rather they will be an in fact an brand new type of organism, which we can, for the purposes of this thread, call "Super-Humans", or "Sumans" for short.
Inevitably, "Sumans", being superior in intelligence, knowledge, ability and physique, will supplant normal humans by method of reproductive attrition.
Thereby, the Human species, Homo-Sapiens, as we know them, will fall to the new order of organisms, which we could also all: "Homo-Superior".
There you have it.
...So what's Your dangerous idea?

