As the Worlds Turn: Visualizing the Rotations of Planets
The rotation of planets have a dramatic effect on their potential habitability.
Dr. James O’Donoghue, a planetary scientist at the Japanese space agency who has the creative ability to visually communicate space concepts like the speed of light and the vastness of the solar system, recently animated a video showing cross sections of different planets spinning at their own pace on one giant globe.
Cosmic Moves: The Rotation of the Planets
Each planet in the solar system moves to its own rhythm. The giant gas planets (Jupiter, Saturn, Uranus, and Neptune) spin more rapidly on their axes than the inner planets. The sun itself rotates slowly, only once a month.
|Planet||Rotation Periods (relative to stars)|
The planets all revolve around the sun in the same direction and in virtually the same plane. In addition, they all rotate in the same general direction, with the exceptions of Venus and Uranus.
In the following animation, their respective rotation speeds are compared directly:
The most visually striking result of planetary spin is on Jupiter, which has the fastest rotation in the solar system. Massive storms of frozen ammonia grains whip across the surface of the gas giant at speeds of 340 miles (550 km) per hour.
Interestingly, the patterns of each planet’s rotation can help in revealing whether they can support life or not.
Rotation and Habitability
As a fish in water is not aware it is wet, so it goes for humans and the atmosphere around us.
New research reveals that the rate at which a planet spins is an essential component for supporting life. Not only does rotation control the length of day and night, bit it influences atmospheric wind patterns and the formation of clouds.
The radiation the Earth receives from the Sun concentrates at the equator. The Sun heats the air in this region until it rises up through the atmosphere and moves towards the poles of the planet where it cools. This cool air falls through the atmosphere and flows back towards the equator.
This process is known as a Hadley cell, and atmospheres can have multiple cells:
A planet with a quick rotation forms Hadley cells at low latitudes into different bands that encircle the planet. Clouds become prominent at tropical regions, which reflect a proportion of the light back into space.
For a planet in a tighter orbit around its star, the radiation received from the star is much more extreme. This decreases the temperature difference between the equator and the poles, ultimately weakening Hadley cells. The result is fewer clouds in tropical regions available to protect the planet from intense heat, making the planet uninhabitable.
Slow Rotators: More Habitable
If a planet rotates slower, then the Hadley cells can expand to encircle the entire world. This is because the difference in temperature between the day and night side of the planet creates larger atmospheric circulation.
Slow rotation makes days and nights longer, such that half of the planet bathes in light from the sun for an extended period of time. Simultaneously, the night side of the planet is able to cool down.
This difference in temperature is large enough to cause the warm air from the day side to flow to the night side. This movement of air allows more clouds to form around a planet’s equator, protecting the surface from harmful space radiation, encouraging the possibility for the right conditions for life to form.
The Hunt for Habitable Planets
Measuring the rotation of planets is difficult with a telescope, so another good proxy would be to measure the level of heat emitted from a planet.
An infrared telescope can measure the heat emitted from a planet’s clouds that formed over its equator. An unusually low temperature at the hottest location on the planet could indicate that the planet is potentially a habitable slow rotator.
Of course, even if a planet’s rotation speed is just right, many other conditions come into play. The rotation of planets is just another piece in the puzzle in identifying the next Earth.
The Most Fuel Efficient Cars From 1975 to Today
This infographic lists the most fuel efficient cars over the past 46 years, including the current leader for 2023.
The Most Fuel Efficient Cars From 1975 to Today
When shopping for a new car, what is the most important factor you look for? According to Statista, it’s not design, quality, or even safety—it’s fuel efficiency.
Because of this, automakers are always looking for clever ways to improve gas mileage in their cars. Beating the competition by even the slimmest of margins can give valuable bragging rights within a segment.
In this infographic, we’ve used data from the EPA’s 2022 Automotive Trends Report to list off the most fuel efficient cars from 1975 to today.
Editor’s note: This is from a U.S. government agency, so the data shown skews towards cars sold in North America.
All of the information in the above infographic is listed in the table below. Data was only available in 5-year increments up until 2005, after which it switches to annual.
|Model Year||Make||Model||Real World Fuel Economy (mpg)||Engine Type|
From this dataset, we can identify three distinct approaches to maximizing fuel efficiency.
Prior to 2000, the best way for automakers to achieve good fuel efficiency was by downsizing. Making cars smaller (lighter) meant they could also be fitted with very small engines.
For example, the 1985 Chevrolet Sprint was rated at 49.6 MPG, but had a sluggish 0-60 time of 15 seconds.
The 2000s saw the introduction of mass-market hybrid vehicles like the Honda Insight and Toyota Prius. By including a small battery to support the combustion engine, automakers could achieve good MPGs without sacrificing so heavily on size.
While the Insight achieved better fuel economy than the Prius, it was the latter that became synonymous with the term “hybrid”. This was largely due to the Prius’ more practical 4-door design.
The following table compares annual U.S. sales figures for both models. Insight sales have fluctuated drastically because Honda has produced the model in several short spans (1999-2006, 2009-2014, 2018-2022).
|Year||Insight Sales||Prius Sales|
The Prius may have dominated the hybrid market for a long time, but it too has run into troubles. Sales have been declining since 2014, even setting historic lows in recent years.
There are several reasons behind this trend, with one being a wider availability of hybrid models from other brands. We also can’t ignore the release of the Tesla Model 3, which began shipping to customers in 2017.
We’re currently in the middle of a historic transition to electric vehicles. However, because EVs do not use fuel, the EPA had to develop a new system called MPGe (miles per gallon of gasoline-equivalent).
This new metric gives us the ability to compare the efficiency of EVs with traditional gas-powered cars. An underlying assumption of MPGe is that 33.7 kilowatt-hours (kWh) of electricity is comparable to the energy content of a gallon of fuel.
The most fuel efficient car you can buy today is the 2023 Lucid Air, which achieves 140 MPGe. Close behind it is the 2023 Tesla Model 3 RWD, which is rated at 132 MPGe.
Check out this page to see the EPA’s top 10 most efficient vehicles for 2023.
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