<span>Answer: Objects with a higher density than water can be observed floating on water
Water spider is one of the animals that can walk above the water. The legs of the spyder float because the force that it gives to the water surface is not higher than the surface tension, thus the water didn't break. Even though the spider density is higher than water, it could look like floating above the water.</span>
D.
The main properties of water are its polarity, cohesion, adhesion, surface tension, high specific heat, and evaporative cooling.
No, x-rays do not travel slower than infrared radiation or even the opposite. Both are travelling in vacuum therefore they travel at same speed. They differ in the frequency of the electromagnetic waves.
<span>In the 19th century, scientists realized that gases in the atmosphere cause a "greenhouse effect" which affects the planet's temperature. These scientists were interested chiefly in the possibility that a lower level of carbon dioxide gas might explain the ice ages of the distant past. At the turn of the century, Svante Arrhenius calculated that emissions from human industry might someday bring a global warming. Other scientists dismissed his idea as faulty. In 1938, G.S. Callendar argued that the level of carbon dioxide was climbing and raising global temperature, but most scientists found his arguments implausible. It was almost by chance that a few researchers in the 1950s discovered that global warming truly was possible. In the early 1960s, C.D. Keeling measured the level of carbon dioxide in the atmosphere: it was rising fast. Researchers began to take an interest, struggling to understand how the level of carbon dioxide had changed in the past, and how the level was influenced by chemical and biological forces. They found that the gas plays a crucial role in climate change, so that the rising level could gravely affect our future. (This essay covers only developments relating directly to carbon dioxide, with a separate essay for Other Greenhouse Gases. Theories are discussed in the essay on Simple Models of Climate.)</span>
