If you haven't seen the movie (or were fortunate enough to forget it) here's the trailer:
There are a number of problems with this movie. For example it stars Mel Gibson. I'll stick to the scientific flaws, though.
In the final scenes we discover the aliens have a major weakness. They die when they come in contact with water. This is one of the most glaring plot holes in all of cinema history. These alien lifeforms travel untold miles to inhabit our planet and they didn't even look at a map first? The earth is more than 70% water, and humans themselves are 50-65% water. This entire alien invasion seems badly planned and ill-advised. But what's the deal with these aliens? Why do they have a problem with water?
Although the simple explanation is that water "burns" their skin, that isn't the most interesting explanation. Instead, let's make a few assumptions.
- Their skin must be very water soluble. In other words, they will dissolve like the wicked witch the second they touch any water. This is a fair assumption and it would make a splash of water a deadly blow, just like in the movie.
- The aliens are in a sealed ship before attacking and all exit the ship at the same time.
- There are millions of aliens exiting these ships at the same time.
I couldn't write about Signs without talking about...well...the signs. This main plot point in Signs is itself a big gaping plot hole. Crop circles were originally seen as proof of alien visitation. They have since been shown to be nothing more than a hoax. Although man made, there are a ton of designs out there, and most of them are stunning. It seems statistically unlikely that aliens would attack earth using a method used in previous alien hoaxes. I suppose it could be argued that the aliens studied our planet and chose to recreate the hoax because humanity was already desensitized to the idea of crop circles. If they had paid such great attention to detail, though, you think they would have noticed all the water...
 Solvation energy is the energy released when a solid dissolves into water. Maybe we should invent a new unit of measurement to standardize the energy of an entire alien dissolving into the atmospheric H2O. How about this: The person that proposes the best name for this new unit of measurement will be entered into the contest an extra time...
 Adsorbing. That's your sciency word for today. You've probably used the word absorb. Adsorbing is when something sticks to the exterior surface of something.