The desire to get to one place from another has been with us for a long time. In Mycenae, Greece, ancient remnants of bridges have been found dating back to about 1600 B.C.E. We’ve built bridges in many different shapes and sizes. Some of them are considered works of art. In Northern India, villagers have even built living bridges using tree roots.Yet for a while, Earth didn’t need bridges at all. It was one giant landmass called Pangea. But over time, Earth’s tectonic plates began to shift and Pangea split into chunks, forming the continents we know today.With so many land masses separated from each other, bridges became a necessity. The desire to connect to each other has pushed us forward technologically, demonstrating our incredible ingenuity as engineers. Many ancient bridges are still in use today, such as the Meles River bridge in Izmir, Turkey, which is nearly 2,900 years old.But if we were going to build bridges between continents, where would we build them? From New York to London? From Sydney to Singapore? Or what about a bridge between Russia and Alaska, over the Bering Strait?Could we possibly build a bridge between continents? And if so, what would it take to build it?There are many different types of bridges we could build to connect two continents. With so many important shipping routes by sea, we’d have to allow boats to pass underneath. We’d probably want to build a railway as well, to maximize the usefulness of such long bridges. This could be beside a road, or below it.The bridge would need a huge number of supports to withstand the weight of thousands of vehicles. If we were to, say, build a bridge between San Francisco and Yokohoma, Japan, some of the supports would have to be built as deep as 5,000 meters (16,404 feet) to sit on the ocean floor. The bridge itself would have to be 8,292 km (5,152 mi) long.To put things into perspective, California’s Golden Gate Bridge, between San Francisco and Sausalito, which is just 1,284 m (4,200 ft) long, took 1,000,000 tons of concrete just to build the anchorages, the massive blocks that grip the bridge’s supporting cables. It took 130,000 km (80,000 mi) of galvanized steel for the support cables.To build a bridge between Japan and California would be 6,478 times longer and almost 33 times deeper than the Golden Gate Bridge. If we used the same bridge design to get to Japan, we’d be looking at roughly 488 billion kg (1,076 billion lbs) of steel just for the support cables!Ok, so we’ve done some of the math. Maybe a bridge between the United States and Japan isn’t the best option. But a bridge between Russia and Alaska over the Bering Strait might be technically feasible.Some people have suggested building an intercontinental railway, for $100 billion, that would include a 60-mile tunnel under the Bering Strait to connect Russia and Alaska. Even if they could raise the money, we’d have to consider factors such as the environmental impact and even politics.But if they changed the plan to building over the Bering Strait, workers may need to be stationed on oil rigs along the way, and construction could be affected by dangerous weather. The construction could also affect the ecosystem in the ocean. And once the bridge was built, there wouldn’t really be enough traffic to make it worthwhile.But what if we built a longer bridge over an ocean? The longest bridge we’ve ever built is China’s Danyang-Kunshan Grand Bridge, spanning 164.8 km (102.4 mi). That’s a small distance compared to going over an ocean.We would need a weather alert system in place to monitor storms and protocols to protect travelers from sudden changes in the weather. We might need to build a covered bridge to protect vehicles from extreme winds. And in order to keep this bridge operational, there would likely be a steep fee to use it.And what would the trip be like? Due to the huge distance, we’d need gas stations, rest stops, hotels, garages, hospitals and even police stations. Unlike a typical road trip, you would get pretty bored by the scenery, which would be miles of concrete and water.Don’t expect any fun landmarks along the way, although you might see a whale or two!We even thought about building a chain of bridges from Northern Territory, Australia through various islands to Singapore. However, with the majority of the Australian population living in the south, most Australians would likely prefer to fly instead of the long drive to the north.This series of bridges would also be incredibly expensive to build, and require a huge amount of people, resources and time. You can imagine the fees to drive across one of these incredibly long bridges, plus the cost of gas, and meals, and hotels.The long and short of it is that we probably won’t be building bridges across our oceans. However, this might be a possibility if we lived on a tiny planet. But that’s a story for another What If.