Video: The 5 Largest Cities Throughout the Course of History
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Video: The 5 Largest Cities Throughout the Course of History

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The world’s most influential cities have certain attributes that make them appear timeless.

Metropolises like New York City, Hong Kong, Shanghai, and London have unprecedented size, opportunities, economic might, and cultural significance, that it’s easy to imagine them as permanent and unparalleled fixtures on the world stage.

However, any glance at world history shows us immediately that these places are not as exceptional or as timeless as we would like to think. Over time, it seems that even the most important cities eventually fall or slip in status.

That’s why a glance at the record books can be humbling, as we come across the names of many ancient cities that were the most important during their time – places like Luoyang, Ctesiphon, Pataliputra, and Constantinople – that today, the majority of people are much less familiar with.

The 5 Largest Cities Over Time

Today we present to you two videos from the Ollie Bye Youtube channel that show the rapidly changing history of the world’s top cities by population.

It’s incredible to watch the rise and fall of these cities, especially when we’re talking about the centers that were the undisputed heavyweight champions of their day.

The 5 Largest Cities (Years: 3000 BC to 1600 AD)

Over this massive span of time, the designation of the world’s most populous city shifts 16 times.

Rome keeps the title for an impressive period – over 400 years – while Baghdad and Chinese cities also have impressive runs as well. However, what’s most provoking about the video is the list of lesser-known cities that have held the title, such as Chang’an, Merv (Marv), and Pi-Ramesses.

The 5 Largest Cities (Years: 1600 to 2100)

During this much shorter stretch of time of more modern history, the rate of urbanization is skyrocketing and cities are now growing at exponential rates.

The most populous city shifts nine times – and by the year 2100, it’s projected that the five most populous cities could have 370 million people living between them.

This would be higher than the total population of the entire world in the 12th century.

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Science

Draining the World’s Oceans to Visualize Earth’s Surface

More than two-thirds of Earth’s surface is covered by water and hidden from sight. This animation drains the world’s oceans to reveal the ocean floor.

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Draining the World’s Oceans to Visualize Earth’s Surface Share

Draining the World’s Oceans to Visualize Earth’s Surface

Although many maps of our planet go into great topographical detail on land, almost two-thirds of the Earth’s surface is covered by the world’s oceans.

Hidden from sight lie aquatic mountain ranges, continental shelves, and trenches that dive deep into the Earth’s crust. We might be familiar with a few of the well-known formations on the ocean floor, but there’s a whole detailed “world” that’s as rich as the surface, just waiting to be explored.

This animation from planetary researcher James O’Donoghue of the Japan Aerospace Exploration Agency (JAXA) and NASA simulates the draining the world’s oceans to quickly reveal the full extent of the Earth’s surface.

How Deep Does the Ocean Go?

Above sea level, Earth’s topography reaches all the way up to 8,849 meters (29,032 ft) to the top of Mt. Everest. But going below sea level, it actually goes deeper than the height of Everest.

Open ocean is called the pelagic zone, which can be broken down into five regions by depth:

  • 0m–200m: Epipelagic (sunlight zone). Illuminated shallower waters that contain most of the ocean’s plants and animals.
  • 200m–1,000m: Mesopelagic (twilight zone). Stretches from where 1% of surface light reaches to where surface light ends. Contains mainly bacteria, as well as some large organisms like the swordfish and the squid.
  • 1,000m–4,000m: Bathypelagic (midnight zone). Pitch black outside of a few bioluminescent organisms, with no living plants. Smaller anglerfish, squid, and sharks live here, as well as a few large organisms like giant squid.
  • 4,000m–6,000m: Abyssopelagic (abyssal zone). Long thought to be the bottomless end of the sea, the abyssal zone reaches to just above the ocean floor and contains little life due to extremely cold temperatures, high pressures, and complete darkness.
  • 6,000m–11,000m: Hadopelagic (hadal zone). Named after Hades, the Greek god of the underworld, the hadal zone is the deepest part of the ocean. It can be found primarily in trenches below the ocean floor.
  • To put ocean depths into context, the bottom of the ocean is more than 2,000m greater than the peak of Mount Everest.

    What “Draining” the World’s Oceans Reveals

    For a long time, the ocean floor was believed to be less understood than the Moon.

    The sheer depth of water made it difficult to map without newer technology, and the tremendous pressure and extreme temperatures make navigation grueling. A manned vehicle reached the deepest known point of the Mariana Trench—the Challenger Deep—in 1960, almost 90 years after it was first charted in 1872.

    But over the last few decades, humanity’s understanding and exploration of the ocean floor has grown in leaps and bounds. O’Donoghue’s animation shows just how much detail we’ve been missing.

    The first easily noticeable characteristic is the Earth’s continental shelves, which appear quickly. Most are visible by 140 meters, though the Arctic and Antarctic shelves are far deeper.

    The animation then speeds up, as thousands of meters of depth reveal the tops of small mountain ridges and aquatic islands. From 2,000 to 3,000 meters, mid-ocean ridges appear that span the length of the Arctic, Pacific, and Indian oceans.

    From 3,000 to 6,000 meters of ocean drained, these aquatic mountains slowly give way to the vast majority of the ocean floor. Little changes over the final 5,000 meters except to illustrate just how deep the ocean’s trenches reach.

    Of course, technically the bottom of the Challenger deep is the deepest known point of the Mariana Trench. As satellite and imaging technology improves further, and aquatic mapping voyages become more possible, who knows what else we’ll discover beneath the waves.

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Misc

How Has Car Safety Improved Over 60 Years?

Seatbelts first became mandatory in the US in 1968. Since then, new technologies have greatly reduced road fatalities.

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Car Safety innovations

How Has Car Safety Improved Over 60 Years?

Did you know that in 2019, there were 6.7 million car accidents in the U.S. alone?

This resulted in 36,096 deaths over the year—an awful statistic to say the least—but one that would be much worse if it weren’t for seatbelts, airbags, and other modern safety devices.

In this infographic, we’ve visualized data from the U.S. Bureau of Transportation to show how breakthroughs in car safety have drastically reduced the number of motor vehicle fatalities.

Measuring Safety Improvements

The data shows the number of fatalities for every 100 million miles driven. From a high of 5.1 in 1960 (the first year data is available), we can see that this metric has fallen by 78% to just 1.1.

YearFatilities per 100 million miles
19605.1
19704.7
19803.4
19902.1
20001.5
20101.1
20191.1

What makes this even more impressive is the fact that there are more cars on the road today than in 1960. This can be measured by the total number of miles driven each year.

Vehicle Miles Driven

So, while the total number of miles driven has increased by 371%, the rate of fatalities has decreased by 78%. Below, we’ll take a closer look at some important car safety innovations.

1. The Seatbelt

The introduction of seatbelts was a major stepping stone for improving car safety, especially as vehicles became capable of higher speeds.

The first iteration of seatbelts were a 2-point design because they only looped across a person’s waist (and thus had 2 points of mounting). This design is flawed because it doesn’t hold our upper body in place during a collision.

Today’s seatbelts use a 3-point design which was developed in 1959 by Nils Bohlin, an engineer at Volvo. This design adds a shoulder belt that holds our torso in place during a collision. It took many years for Volvo to not only develop the device, but also to convince the public to use it. The U.S., for instance, did not mandate 3-point seatbelts until 1973.

2. The Airbag

The concept of an airbag is relatively simple—rather than smacking our face against the steering wheel, we cushion the blow with an inflatable pillow.

In practice, however, airbags need to be very precise because it takes just 50 milliseconds for our heads to collide with the wheel in a frontal crash. To inflate in such a short period of time, airbags rely on a chemical reaction using sodium azide.

The design of an airbag’s internal mechanism can also cause issues, as was discovered during the Takata airbag recall. As these airbags inflated, there was a chance for them to also send metal shards flying through the cabin at high speeds.

Dual front airbags (one for each side) were mandated by the U.S. government in 1998. Today, many cars offer side curtain airbags as an option, but these are not required by law.

3. The Backup Camera

Backup cameras became a legal requirement in May 2018, making them one of the newest pieces of standard safety equipment in the U.S. These cameras are designed to reduce the number of backover crashes involving objects, pedestrians, or other cars.

Measuring the safety benefits of backup cameras can be tricky, but a 2014 study did conclude that cameras were useful for preventing collisions. A common criticism of backup cameras is that they limit our field of vision, as opposed to simply turning our heads to face the rear.

Taking Car Safety to the Next Level

According to the National Highway Traffic Safety Administration (NHTSA), having both seatbelts and airbags can reduce the chance of death from a head-on collision by 61%. That’s a big reduction, but there’s still plenty of room left on the table for further improvements.

As a result, automakers have been equipping their cars with many technology-enabled safety measures. This includes pre-collision assist systems which use sensors and cameras to help prevent an accident. These systems can prevent you from drifting into another lane (by actually adjusting the steering wheel), or apply the brakes to mitigate an imminent frontal collision.

Whether these systems have any meaningful benefit remains to be seen. Referring to the table above shows that fatalities per 100 million miles have not fallen any further since 2010.

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