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Visualizing the Gravitational Pull of the Planets

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    Visualizing the Gravitational Pull of the Planets

    Gravity is one of the basic forces in the universe. Every object out there exerts a gravitational influence on every other object, but to what degree?

    The gravity of the sun keeps all the planets in orbit in our solar system. However, each planet, moon and asteroid have their own gravitational pull defined by their density, size, mass, and proximity to other celestial bodies.

    Dr. James O’Donoghue, a Planetary Astronomer at JAXA (Japan Aerospace Exploration Agency) created an animation that simplifies this concept by animating the time it takes a ball to drop from 1,000 meters to the surface of each planet and the Earth’s moon, assuming no air resistance, to better visualize the gravitational pull of the planets.

    Sink like a Stone or Float like a Feather

    Now, if you were hypothetically landing your spacecraft on a strange planet, you would want to know your rate of descent. Would you float like a feather or sink like a stone?

    It is a planet’s size, mass, and density that determines how strong its gravitational pull is, or, how quick or slow you will approach the surface.

    Mass (1024kg)Diameter (km)Density (kg/m3)Gravity (m/s2)Escape Velocity (km/s)
    Mercury0.334,8795,4273.74.3
    Venus4.8712,1045,2438.910.4
    Earth5.9712,7565,5149.811.2
    Moon0.0733,4753,3401.62.4
    Mars0.6426,7923,9333.75.0
    Jupiter1,898142,9841,32623.159.5
    Saturn568120,5366879.035.5
    Uranus86.851,1181,2718.721.3
    Neptune10249,5281,63811.023.5
    Pluto0.01462,3702,0950.71.3

    According to Dr. O’Donoghue, large planets have gravity comparable to smaller ones at the surface—for example, Uranus attracts the ball down slower than on Earth. This is because the relatively low average density of Uranus puts the actual surface of the planet far away from the majority of the planet’s mass in the core.

    Similarly, Mars is almost double the mass of Mercury, but you can see the surface gravity is actually the same which demonstrates that Mercury is much denser than Mars.

    Exploring the Outer Reaches: Gravity Assistance

    Knowing the pull of each of the planets can help propel space flight to the furthest extents of the solar system. The “gravity assist” flyby technique can add or subtract momentum to increase or decrease the energy of a spacecraft’s orbit.

    Generally it has been used in solar orbit, to increase a spacecraft’s velocity and propel it outward in the solar system, much farther away from the sun than its launch vehicle would have been capable of doing, as in the journey of NASA’s Voyager 2.


    Gravity Assist

    Launched in 1977, Voyager 2 flew by Jupiter for reconnaissance, and for a trajectory boost to Saturn. It then relied on a gravity assist from Saturn and then another from Uranus, propelling it to Neptune and beyond.

    Despite the assistance, Voyager 2’s journey still took over 20 years to reach the edge of the solar system. The potential for using the power of gravity is so much more…

    Tractor Beams, Shields, and Warp Drives…Oh My!

    Imagine disabling an enemy starship with a gravity beam and deflecting an incoming photon torpedo with gravity shields. It would be incredible and a sci-fi dream come true.

    However, technology is still 42 years from the fictional date in Star Trek when mankind built the first warp engine, harnessing the power of gravity and unlocking the universe for discovery. There is still time!

    Currently, the ALPHA Experiment at CERN is investigating whether it is possible to create some form of anti-gravitational field. This research could create a gravitational conductor shield to counteract the forces of gravity and allow the creation of a warp drive.

    By better understanding the forces that keep us grounded on our planets, the sooner we will be able to escape these forces and feel the gravitational pull of the planets for ourselves.

    …to boldly go where no one has gone before!

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Maps

Mapped: Chinese Provinces With Cities Over 1 Million People

Some Chinese provinces are so populous they rival entire countries. But how many of them have cities over a million people?

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A cropped map of all the Chinese provinces with cities over 1 million people.

Mapped: Chinese Provinces With Cities Over 1 Million People

This was originally posted on our Voronoi app. Download the app for free on iOS or Android and discover incredible data-driven charts from a variety of trusted sources.

Almost two-thirds of the 1.4 billion Chinese population lives in an urban area. But how does this play out across the country’s geography?

This map shows the Chinese provinces with cities over a million residents. Data for this graphic is sourced from citypopulation.de.

Ranked: Chinese Provinces With Cities Over 1 Million People

China’s Guangdong province has 17 cities with a population size of 1 million or more. It is also China’s most populous province, home to 127 million people. This makes it comparable to the size of Japan, the 12th most populous country in the world.

RankProvinceCities With 1 Million People
1Guangdong17
2Jiangsu12
3Shandong9
4Hebei6
5Zhejiang6
6Liaoning5
7Guangxi*4
8Henan4
9Anhui3
10Fujian3
11Heilongjiang3
12Hubei3
13Hunan3
14Inner Mongolia*3
15Jiangxi3
16Jilin2
17Gansu2
18Shaanxi2
19Shanxi2
20Sichuan2
21Xinjiang*2
22Beijing**1
23Chongqing**1
24Guizhou1
25Hainan1
26Ningxia*1
27Qinghai1
28Shanghai**1
29Tianjin**1
30Yunnan1
31Hong Kong***1
32Macao***1

*Autonomous Region. **Direct-Administered Municipality. ***Special Administrative Region.

Jiangsu, ranked fourth in population overall, is the only other province which has 10+ cities with a million or more inhabitants.

Meanwhile, some of China’s most populous cities—Shanghai, Beijing, Tianjin, and Chongqing—are administered directly by the central government, and do not fall under provincial control.

In fact, Shanghai and Beijing have informal “population caps” to prevent them from growing larger, in a bid to reduce pollution, overcrowding, and pressure on public services.

On the other hand, Tibet’s cold climes and rugged terrain make for a sparsely-populated area, totalling 3 million people across 1.2 million km². Tibet is the only province-level division in China without a single city over a million residents.

All together, China has 105 cities with more than one million inhabitants. For comparison, India has 65, and the U.S. has nine.

Learn More About Population Metrics from Visual Capitalist

If you enjoyed this post, check out Interactive Map: The World as 1,000 People. This visualization shows how unevenly people are distributed across the globe, re-imagining the entire 8 billion human population as only 1,000 people.

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