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. 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.
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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Even while political regimes across these countries have changed over time, they’ve largely followed a few different types of governance. Today, every country can ultimately be classified into just nine broad forms of government systems.
This map by Truman Du uses information from Wikipedia to map the government systems that rule the world today.
Countries By Type of Government
It’s important to note that this map charts government systems according to each country’s legal framework. Many countries have constitutions stating their de jure or legally recognized system of government, but their de facto or realized form of governance may be quite different. Here is a list of the stated government system of UN member states and observers as of January 2023: Let’s take a closer look at some of these systems.
Monarchies
Brought back into the spotlight after the death of Queen Elizabeth II of England in September 2022, this form of government has a single ruler. They carry titles from king and queen to sultan or emperor, and their government systems can be further divided into three modern types: constitutional, semi-constitutional, and absolute. A constitutional monarchy sees the monarch act as head of state within the parameters of a constitution, giving them little to no real power. For example, King Charles III is the head of 15 Commonwealth nations including Canada and Australia. However, each has their own head of government. On the other hand, a semi-constitutional monarchy lets the monarch or ruling royal family retain substantial political powers, as is the case in Jordan and Morocco. However, their monarchs still rule the country according to a democratic constitution and in concert with other institutions. Finally, an absolute monarchy is most like the monarchies of old, where the ruler has full power over governance, with modern examples including Saudi Arabia and Vatican City.
Republics
Unlike monarchies, the people hold the power in a republic government system, directly electing representatives to form government. Again, there are multiple types of modern republic governments: presidential, semi-presidential, and parliamentary. The presidential republic could be considered a direct progression from monarchies. This system has a strong and independent chief executive with extensive powers when it comes to domestic affairs and foreign policy. An example of this is the United States, where the President is both the head of state and the head of government. In a semi-presidential republic, the president is the head of state and has some executive powers that are independent of the legislature. However, the prime minister (or chancellor or equivalent title) is the head of government, responsible to the legislature along with the cabinet. Russia is a classic example of this type of government. The last type of republic system is parliamentary. In this system, the president is a figurehead, while the head of government holds real power and is validated by and accountable to the parliament. This type of system can be seen in Germany, Italy, and India and is akin to constitutional monarchies. It’s also important to point out that some parliamentary republic systems operate slightly differently. For example in South Africa, the president is both the head of state and government, but is elected directly by the legislature. This leaves them (and their ministries) potentially subject to parliamentary confidence.
One-Party State
Many of the systems above involve multiple political parties vying to rule and govern their respective countries. In a one-party state, also called a single-party state or single-party system, only one political party has the right to form government. All other political parties are either outlawed or only allowed limited participation in elections. In this system, a country’s head of state and head of government can be executive or ceremonial but political power is constitutionally linked to a single political movement. China is the most well-known example of this government system, with the General Secretary of the Communist Party of China ruling as the de facto leader since 1989.
Provisional
The final form of government is a provisional government formed as an interim or transitional government. In this system, an emergency governmental body is created to manage political transitions after the collapse of a government, or when a new state is formed. Often these evolve into fully constitutionalized systems, but sometimes they hold power for longer than expected. Some examples of countries that are considered provisional include Libya, Burkina Faso, and Chad.
