Editing Solar System (section)

=== Distances and scales ===
[[File:Solar System distance to scale.svg|center|thumb|upright=2.5|Comparison of the distances between planets, with the white bar showing orbital variations. The size of the planets is not to scale.]]
[[File:Orbital distances in the solar system linear scale.png|thumb|Relative orbital distances in the Solar System visualized as a condensed rectangle]]

The Solar System is huge, way bigger than what humans can easily imagine. The [[distance]]s and [[size]]s of the planets and other space objects are so big that it is hard to picture them using everyday ideas.<ref>{{Cite web|title=The Solar System to Scale: Dynamic 2D Model|url=https://solartoscale.com/|access-date=2025-07-08|website=solartoscale.com}}</ref> The [[Sun]] is the biggest thing in the Solar System. It is so massive that it makes up almost all the [[mass]] in the entire Solar System. The Sun’s [[radius]] is about 700,000 kilometers (or 400,000 miles). Even though [[Earth]] feels big to us, about 1.3 million Earth's would fit inside the Sun.<ref name=":10" /> [[Jupiter]] is the largest planet. It is 5.2 times farther from the Sun than Earth and is so big that over 1,300 Earths could fit inside it. Its [[diameter]] is more than 11 times that of Earth.<ref>{{Cite web|date=2017-10-05|title=Jupiter Facts|url=https://science.nasa.gov/jupiter/jupiter-facts/|access-date=2025-07-08|language=en-US}}</ref> On the other hand, [[Mercury (planet)|Mercury]], the smallest planet, is just a little bigger than [[Moon|Earth’s Moon]].<ref>{{Cite web|title=Mercury|url=https://observatory.astro.utah.edu/Mercury.html|access-date=2025-07-08|website=observatory.astro.utah.edu}}</ref> And even smaller are [[dwarf planet]]s like [[Pluto]] and tiny space rocks like [[comet]]s and [[asteroid]]s, which can be just a few kilometers wide.<ref>{{Cite web|date=2025-04-22|title=Planet Sizes and Locations in Our Solar System|url=https://science.nasa.gov/solar-system/planets/planet-sizes-and-locations-in-our-solar-system/|access-date=2025-07-08|language=en-US}}</ref>

Because the Solar System is so big, scientists use a special unit called the [[Astronomical unit|Astronomical Unit (AU)]] to measure distances in space. One AU is the average distance between the Earth and the Sun, which is about 149.6 million kilometers (or 93 million miles). Using AU makes it easier to talk about how far planets are from the Sun.<ref>{{Cite web|date=2025-05-29|title=Astronomical unit (AU, or au) {{!}} Definition, Conversion, & Facts {{!}} Britannica|url=https://www.britannica.com/science/astronomical-unit|access-date=2025-07-08|website=www.britannica.com|language=en}}</ref> For example, [[Venus]] is about 0.72 AU from the Sun, [[Mars]] is about 1.52 AU, and [[Neptune]], the farthest main planet, is about 30 AU away. The [[Kuiper Belt]], which contains icy objects like Pluto, stretches from around 30 AU to 50 AU.<ref>{{Cite web|title=Scale of the Solar System|url=https://web.pa.msu.edu/people/frenchj/solarsystemscale/|access-date=2025-07-08|website=web.pa.msu.edu}}</ref> Even farther out is the [[Oort cloud|Oort Cloud]], a mysterious area that might reach 100,000 AU from the Sun.<ref name=":6" /> Usually, the farther a planet is from the Sun, the bigger the gap between it and the next planet. For instance, Venus is only about 0.33 AU farther from the Sun than Mercury, but Saturn is 4.3 AU farther out than Jupiter, and Neptune is 10.5 AU beyond Uranus.<ref>{{Cite web|title=Comparing the Distance Between Planets|url=https://www.msnucleus.org/membership/html/k-6/uc/solar_system/2/ucss2_2a.html|access-date=2025-07-08|website=www.msnucleus.org}}</ref> In the past, scientists tried to find patterns in these distances, like the [[Titius–Bode law]] or [[Mysterium Cosmographicum|Kepler's ideas]], but as more planets and objects were discovered, those ideas did not hold up.<ref>{{Cite journal|last=Jaki|first=Stanley L.|date=1972-07-01|title=The Early History of the Titius-Bode Law|url=https://pubs.aip.org/ajp/article/40/7/1014/1045433/The-Early-History-of-the-Titius-Bode-Law|journal=American Journal of Physics|language=en|volume=40|issue=7|pages=1014–1023|doi=10.1119/1.1986734|issn=0002-9505}}</ref><ref>{{Cite journal|last=Phillips|first=J. P.|date=1965|title=Kepler's Echinus|url=https://www.journals.uchicago.edu/doi/10.1086/349957|journal=Isis|language=en|volume=56|issue=2|pages=196–200|doi=10.1086/349957|issn=0021-1753}}</ref><ref>{{Cite web|last=Staff|first=Astronomy|date=2006-10-01|title=Is it a coincidence that most of the planets fall within the Titius-Bode law's boundaries? {{!}} Astronomy.com|url=https://www.astronomy.com/science/is-it-a-coincidence-that-most-of-the-planets-fall-within-the-titius-bode-laws-boundaries/|access-date=2025-07-08|website=Astronomy Magazine|language=en-US}}</ref>

There is a lot of empty space between the planets in our Solar System. Even though the planets follow paths around the Sun, the distances between them are huge compared to how big the planets are.<ref>{{Cite web|title=Distances Between the Planets of the Solar System • The Planets|url=https://theplanets.org/distances-between-planets/|access-date=2025-07-09|website=The Planets|language=en-US}}</ref> For example, Earth is about 12,700 kilometers wide, but the closest it ever gets to Mars is around 96 million kilometers away.<ref>{{Cite web|date=2023-05-30|title=Facts About Earth|url=https://science.nasa.gov/earth/facts/|access-date=2025-07-09|language=en-US}}</ref><ref>{{Cite web|last=|first=|date=2025-01-12|title=Mars closest to Earth on January 12, 2025|url=https://earthsky.org/tonight/mars-closest-to-earth/|access-date=2025-07-09|website=earthsky.org|language=en-US}}</ref> Because of these huge distances, even fast [[spacecraft]] take a long [[time]], months or years, to travel between planets. The farther you go, the longer it takes.<ref>{{Cite web|date=2025-02-19|title=How Long Does it Take to Get to the Moon... Mars... Jupiter? We Asked a NASA Expert: Episode 51 - NASA|url=https://www.nasa.gov/directorates/smd/how-long-does-it-take-to-get-to-the-moon-mars-jupiter-we-asked-a-nasa-expert-episode-51/|access-date=2025-07-09|language=en-US}}</ref> For instance, [[light]] from the Sun takes only 8 minutes to reach Earth, but it takes over 4 hours to reach Neptune.<ref>{{Cite web|date=2024-04-12|title=How long does it take for light from the Sun to reach Earth?|url=https://www.skyatnightmagazine.com/space-science/how-take-light-from-sun-reach-earth|access-date=2025-07-09|website=BBC Sky at Night Magazine|language=en}}</ref><ref>{{Cite web|date=2017-11-10|title=Neptune: Facts - NASA Science|url=https://science.nasa.gov/neptune/neptune-facts/|access-date=2025-07-09|language=en-US}}</ref> All this [[Outer space|space]] makes it harder to explore and communicate with the outer planets. Sending missions to places like Neptune or beyond is a big challenge and a major achievement for [[science]] and [[engineering]].<ref>{{Cite web|title=Challenges of space travel - Space exploration - National 5 Physics Revision|url=https://www.bbc.co.uk/bitesize/guides/zqm4fcw/revision/3|access-date=2025-07-09|website=BBC Bitesize|language=en-GB}}</ref>

Some [[Scientific model|model]]s of the Solar System are made to help people understand just how big and spread out everything really is. Since the real Solar System is way too large to picture easily, scientists and educators sometimes build scale models to shrink it down while keeping the sizes and distances in the right proportion. Some of these models are small and mechanical, like [[Orrery|orreries]], which are devices that show planets moving around the Sun.<ref>{{Cite web|title=Orrery|url=https://www.hsm.ox.ac.uk/orrery|access-date=2025-07-09|website=www.hsm.ox.ac.uk|language=en}}</ref> Others are huge and can stretch across cities or even entire regions. One of the biggest models is the [[Sweden Solar System]].<ref>{{Cite web|title=Sweden Solar System|url=https://www.swedensolarsystem.se/en/|access-date=2025-07-09|website=www.swedensolarsystem.se}}</ref> In it, the [[Avicii Arena]] in [[Stockholm]] represents the Sun, and it is about 110 meters wide (361 feet). In this model, Jupiter is a 7.3-meter ball (about 24 feet wide) located at an [[airport]] 40 kilometers (25 miles) away. [[Sedna]], an object far out in the Solar System, is shown as a 10-centimeter ball (about 4 inches) placed 810 kilometers (500 miles) away.<ref>{{Cite web|title=Luleå är Sedna - Lokalt den 17 november 2005 - Arkiv - Norrbottens-Kuriren|url=http://www.kuriren.nu/arkiv/2005/11/17/Lokalt/1510647/Lule%C3%A5-%C3%A4r-Sedna.aspx|access-date=2025-07-09|website=www.kuriren.nu}}</ref><ref>{{Cite web|title=Tours of Model Solar Systems|url=http://www.psych.illinois.edu/~wbrewer/solarmodel.html|access-date=2025-07-09|website=www.psych.illinois.edu|archive-date=2010-07-24|archive-url=https://web.archive.org/web/20100724064517/http://www.psych.illinois.edu/~wbrewer/solarmodel.html|url-status=dead}}</ref> If we shrank the distance from the Sun to Neptune down to just 100 meters (about the length of a soccer field), then the Sun would only be about 3 centimeters wide (a little bigger than a [[marble]]), the [[Giant planet|giant planets]] would be all smaller than about 3 mm (0.12 in), and Earth and the other small planets would be tiny dots, smaller than a [[flea]]. These kinds of models help us understand that even though planets can be big, they are still tiny compared to the space between them.<ref>{{Cite web|title=Solar System Scale|url=https://www.nasa.gov/audience/foreducators/5-8/features/F_Solar_System_Scale.html|access-date=2025-07-09|website=www.nasa.gov|archive-date=2023-03-28|archive-url=https://web.archive.org/web/20230328021134/https://www.nasa.gov/audience/foreducators/5-8/features/F_Solar_System_Scale.html|url-status=dead}}</ref>