How did the polar ice caps form?

 During the age of the dinosaurs, Earth had no polar ice caps. They formed millions of years apart—one when a continent tore in half, the other paradoxically triggered by a warming current.

The southern ice cap formed first, roughly 34 million years ago. South America and Antarctica used to be a single continuous landmass, which allowed warm ocean currents from the equator to flow southward and keep the Antarctic continent temperate. As the tectonic plates shifted, South America tore away from Antarctica, opening a deep waterway known as the Drake Passage.

This narrow opening fundamentally changed the world's oceans. It allowed a massive stream of water—the Antarctic Circumpolar Current (ACC)—to flow continuously around the continent from west to east.

The Antarctic Circumpolar Current circles Antarctica from west to east, acting as a thermal barrier that prevents warm equatorial waters from reaching the continent. Source: Wikimedia Commons.

The ACC acts as a thermal shield. It traps cold water around Antarctica and physically blocks warmer tropical currents from reaching the southern landmass. Cut off from global heat circulation, Antarctica’s temperature plummeted, and snow began to accumulate year-round, eventually compressing into the continental ice sheet that exists today.

The Arctic ice cap formed much later, starting around 3 million years ago. For millions of years, ocean water flowed freely between the Atlantic and Pacific near the equator. But as North and South America drifted together, they collided to form the Isthmus of Panama.

This land bridge severed the connection between the two oceans. With nowhere else to go, the warm equatorial waters in the Atlantic were forced northward, creating the Gulf Stream. This powerful current carried immense amounts of moisture up toward the North Pole. Because global carbon dioxide levels were slowly dropping at the time, the Arctic was cold enough that this new influx of moisture fell as snow rather than rain. Year after year, the snow built up, reflecting sunlight back into space and cooling the region further until the northern ice sheets took hold.

What ice age animal could survive in today’s world if it was brought back?

 The wooly mammoth.

It is perfectly adapted to survive ultra cold climates in Siberia. They’ve even done estimates that at least 48,000 of them could survive in Alaska alone today.

They were big, strong, and capable of defending themselves against polar bears.

The problem would simply be with poaching and hunting. Some people would see them as the ultimate trophy to have on their wall.

But a part of me thinks most would relish the opportunity to see these big fellas roaming the earth again.

Why is water and ice colourless but snow is white?

 For one thing, objects do not have color. They reflect, transmit, refract, disperse, or absorb various wavelengths of light. And our retinas and brains receive and then interpret those wavelengths as color.

When objects transmit all of the wavelengths our eyes are sensitive to, we say those objects are clear … like a glass of water, for example, or even ice depending on how it freezes. But water absorbs certain long wavelengths (the red end of the spectrum) such that when there is a lot of it, it appears to us as blue.

Well, at least some of the time, unless there are lots of little droplets which scatter the light, so it might look white - or maybe even multicolored, depending on how the light is reflected and refracted from those droplets.

That is, what we see is light and how it is reflected or refracted or transmitted by what we are looking at. And sunlight transmitted through tiny ice crystals can also disperse the white light of the Sun according to wavelength.

Of course, even ice is not actually always clear, and it definitely can appear white - just like snow, and the water vapor we call clouds.

Or it can absorb the longer wavelengths of light and appear blue.