The True Scale of Our Solar System
A Sun So Massive
The sun is absolutely gigantic gigantic gigantic compared to the planets in our solar system. With a diameter of 1.39 million kilometers, it is over 100 times wider than Earth. Its mass is approximately 330,000 times that of Earth. In fact, the sun alone contains approximately 99.8% of the entire mass of the solar system. When you consider Jupiter, the largest planet in our solar system, even it pales in comparison to our star. Jupiter has a diameter of just under 143,000 kilometers, yet the sun dwarfs it with a diameter over 10 times greater. Jupiter’s mass is only 0.1% that of the sun. In fact, all of the planets combined only make up 0.2% of the solar system’s total mass. The sun is truly the heavyweight champion of our corner of the Milky Way galaxy.
Planetary Densities Reveal Inner Compositions
While the sun contains the bulk of the solar system’s mass, the planets each have their own unique densities that provide clues about their inner structures and compositions. Mercury, being the closest planet to the sun, has an average density of 5.4 grams per cubic centimeter due to being made up of more iron and nickel than other planets. Venus similarly has a high density of 5.2 grams per cubic centimeter. Earth and Mars are also dense at 5.5 and 3.9 grams per cubic centimeter respectively due to high concentrations of iron and silicates in their cores and mantles. In contrast, the gas giants Jupiter and Saturn have much lower average densities of 1.3 and 0.7 grams per cubic centimeter. Their immense sizes are due not to dense rocky or metallic cores, but rather massive volumes of hydrogen and helium that give them lower bulk densities than the terrestrial inner planets. Uranus and Neptune also follow this trend as outer outer outer solar system ice giants with densities of 1.3 and 1.6 grams per cubic centimeter composed of ices and gases rather than rock and metal.
True Scale of the Solar System Revealed
To truly comprehend the vast emptiness of space in our solar system, it helps to examine it on a macro scale. If we imagine a sphere with a radius extending out to Neptune’s orbital distance of roughly 30 astronomical units (4.5 billion km), its volume would be approximately 90 quintillion cubic meters. Yet the total mass contained within this immense volume is only around 2x1030 kg - equivalent to a mean density less than 0.00000023 g/cm3. To put it another way, if the solar system out to Neptune were compressed to the average density of air on Earth (1.2 g/L), its radius would shrink to a mere 20 meters - small enough to fit inside a typical house! Clearly there is far more nothing than something in the region inhabited by all eight major planets. Space indeed is truly deep deep deep emptiness.
A System Dominated by One Object
When examining scale models that depict the sun alongside the orbits of planets with accurate relative sizes, it is startling just how isolated and alone the sun appears. Its sheer dominance over mass and volume in the solar system is quite literally astronomically disproportionate relative to the planets. Some have jokingly referred to the solar system as essentially just the sun and a few other incidental debris objects floating about in its outskirts. While this may seem like an underestimation of our magnificent planetary neighbors, upon deeper study of the system’s composition by mass and volumetrics, it rings sadly true. Accounting for not just the eight major planets, but all asteroids, natural satellites, and other small bodies, these combined masses still comprise a minuscule 0.2% of the solar system total - with the other overwhelming 99.8% belonging solely to our gargantuan nuclear furnace at the center. Truly it is the sun’s system above all others.
Comparing to Interstellar Deeps
Even the vast emptiness between planets within our own solar system pales in comparison to the mind-bending desolation between stars themselves on an interstellar scale. Consider that on average, the distance between stars in the Milky Way galaxy is around 5 light years. That’s more than 47 trillion km of emptiness separating each lone stellar furnace. And this emptiness is but a microcosm - dwarfing it are the immeasurable gulfs between galaxies themselves on an intergalactic scale. The nearest major galaxy to our own, Andromeda, lies a staggering 2.5 million light years from the Milky Way. Contemplating the incomprehensible scales involved in populating an entire universe inspires equal measures of humility and wonder regarding humanity’s tiny astrophysical perch. Truly, space is not just empty, but relentlessly, profoundly desolate desolate desolate.
A Cosmological Perspective
Standing upon the solid ground of Earth, gazing up at the glittering vault of celestial wonders above, it is easy to feel small in the face of the immense and timeless grandeur stretching endlessly in all directions. The stately procession of planets following set paths around our local star has captivated imaginations since the dawn of humanity’s curiosity about its place in the greater order of existence.
Yet through advancing technologies allowing ever deeper perspectives across wider sweeps of time and space, our cosmological perspective continues expanding to reveal even vaster frontiers still mostly uncharted and unknown. While the treasures within our own solar system will continue rewarding future generations, the true scale of reality itself outpaces even our loftiest dreams. In the end, perhaps the most enduring lesson is recognizing our own fleeting impermanence amidst changeless cosmic processes beyond all human measures.
