{"id":67132,"date":"2026-09-03T04:36:35","date_gmt":"2026-09-02T19:36:35","guid":{"rendered":"https:\/\/phys-edu.net\/wp\/?p=67132"},"modified":"2026-09-03T04:36:35","modified_gmt":"2026-09-02T19:36:35","slug":"if-the-sun-were-the-size-of-a-balance-ball-how-big-would-earth-be","status":"publish","type":"post","link":"https:\/\/phys-edu.net\/wp\/?p=67132&lang=en","title":{"rendered":"If the Sun Were the Size of a Balance Ball, How Big Would Earth Be?"},"content":{"rendered":"

I\u2019m Ken Kuwako, your Science Trainer. Every day is an experiment.<\/strong><\/span><\/p>\n

Here\u2019s a question for you. If you shrank the Sun down to a 50 cm diameter balance ball, how big do you think Earth would be? A soccer ball? A ping-pong ball? \u2026Believe it or not, the answer is just 1 mm. It would be so tiny that you\u2019d have to squint to see it! Today, let\u2019s take a journey into the wonderfully surprising world of a \u201cscale model of the Solar System.\u201d<\/p>\n

\"\"<\/p>\n

While flipping through a science reference book, I came across an intriguing idea: \u201cWhat if the Sun were a sphere 50 cm in diameter? What would happen to the other planets?\u201d I immediately decided to make a calculation sheet to find out. For the model Sun, I used a 50 cm diameter balance ball. You can find the spreadsheet here<\/a>.<\/p>\n

The Planets Turn Into Familiar Objects<\/h3>\n

Once I ran the numbers, I discovered that the other planets could be represented by surprisingly familiar objects when the Sun is scaled down to a 50 cm balance ball.<\/p>\n

Bead\u30008 mm in diameter
\nPing-pong ball\u300044 mm in diameter
\nSoccer ball\u3000220 mm in diameter
\nBaseball\u300070 mm in diameter
\nBeach ball\u3000260 mm in diameter
\nBalance ball\u3000500 mm in diameter<\/p>\n

I also prepared separate sheets for the questions and answers, with the calculation formulas already entered in the answer sheet. Here are the results.<\/p>\n

\"\"<\/p>\n

And what about Earth? Its diameter would be a mere 1 mm. \u201cWait, that tiny?\u201d You\u2019re probably not the only one who finds that surprising. Compared with the size of the Sun, even Jupiter would be no bigger than a ping-pong ball. Suddenly, the enormous scale of the universe becomes something you can almost hold in the palm of your hand.<\/p>\n

Let\u2019s Scale the Distances to the Planets, Too<\/h3>\n

Now that we have our balance ball (the Sun) sitting right in front of us, where would the other planets be orbiting? I ran the numbers for that, too. Here\u2019s what I got.<\/p>\n

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A handy way to visualize these distances is a web service that lets you \u201cdraw circles on Google Maps<\/b>.\u201d Even Mercury, the closest planet to the Sun, would be 21 meters away from our model Sun (the balance ball). That\u2019s already far enough to take you outside the room! Try using the app to draw the circles around your home or school, and you\u2019ll discover some surprisingly interesting things.<\/p>\n

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It would look something like this. The Sun sits at the center, with Mercury, Venus, Earth, and the other planets spreading outward.<\/p>\n

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Overlaying the model on a real map really drives home just how enormous the Solar System is. I\u2019ve also added another version to the spreadsheet<\/a> where the Sun\u2019s diameter is scaled up to 1 meter (100 cm), so give that one a try, too.<\/p>\n

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If Earth Were a 100 cm Sphere, What Would Happen to Tokyo?<\/h3>\n

Apparently, the idea of \u201cWhat would Earth look like if it were a 100 cm sphere?<\/a>\u201d has already been turned into a book. And the details are absolutely mind-blowing.<\/p>\n

The Moon would be about the size of a beach ball, orbiting roughly 30 meters from Earth. The Sun would be 12 km away and, astonishingly, would be about the size of Tokyo Dome. From the perspective of a 100 cm Earth, the Sun would shine as brightly as 14 billion 100-watt light bulbs switched on at once. It\u2019s an incredible reminder of just how enormous the Sun really is.<\/p>\n

Now, if we map these positions onto the JR Tokaido Line, the Solar System looks like this.<\/p>\n

\u30fbEarth would be around Omori Station in Tokyo, with a diameter of 100 cm.
\n\u30fbMercury would be around Shinagawa Station, with a diameter of 40 cm.
\n\u30fbVenus would be around Oimachi, with a diameter of 95 cm.
\n\u30fbMars would be around Kawasaki Station, with a diameter of 50 cm.
\n\u30fbJupiter would be around Hiratsuka Station, with a diameter of 11 m.
\n\u30fbSaturn would be around Mount Fuji, with a diameter of 9 m.<\/p><\/blockquote>\n

I wanted to see whether these numbers really checked out, so I did the calculations myself.<\/p>\n

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\"\"<\/p>\n

The numbers are slightly different from those in the reference I mentioned earlier, but they\u2019re broadly consistent. According to my calculations, the Sun would be about 100 meters in diameter. \u201cA 100-meter sphere\u201d may still be difficult to picture, but I looked it up and discovered that the giant Ferris wheel that once stood at Palette Town in Odaiba was exactly 100 meters in diameter<\/a>.<\/p>\n

\"\"<\/a><\/p>\n

Once you imagine that giant Ferris wheel as the \u201cSun,\u201d the sheer scale of our Solar System becomes truly astonishing.<\/p>\n

Turn It Into a Display and Experience It Together<\/h3>\n

Based on these calculations, I also created a display poster (Google Slides)<\/a>. If you find it useful, please feel free to use it for your classes, science projects, or other activities.<\/p>\n

\"\"<\/p>\n

Later on, I decided to give the display an upgrade. Take a look at this version, too!<\/p>\n

These are 45 mm diameter polystyrene balls I bought at Seria, a Japanese 100-yen shop.<\/p>\n

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I attached one of them to the display at the \u201cping-pong ball\u201d position using a hot glue gun.<\/p>\n

\"\"<\/p>\n

These are beads I also bought at Seria. They are just 4 mm in diameter.<\/p>\n

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I attached these to the display as well.<\/p>\n

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Compared with simply looking at a flat diagram or graph, turning the model into something three-dimensional that students can actually see and touch makes the enormous scale of the Solar System much more engaging\u2014and much easier to appreciate.<\/p>\n

Questions, Requests, and More<\/h3>\n

Let\u2019s bring the wonders and excitement of science a little closer to home! I share fun science experiments you can try at home, along with simple tips and explanations to help you get the most out of them. Feel free to explore the site and see what you can discover!
\n\u30fbThe content from Science Notebook has been turned into a book. For more information, click here<\/a>.
\n\u30fbFor more information about Ken Kuwako, the person behind the site, click here<\/a>.
\n\u30fbFor inquiries and requests, including writing, lectures, science workshops, TV science supervision, and appearances, click here<\/a>.
\n\u30fbFollow X for updates on new articles<\/a>!<\/span><\/p>\n

\"\"<\/a>Science Notebook Channel<\/a> features videos of science experiments!<\/p>\n

\uff19\u6708\u306e\u30a4\u30c1\u30aa\u30b7\u5b9f\u9a13\uff01<\/h3>\r\n\u304a\u5f01\u5f53\u7bb1\u3092\u30d7\u30e9\u30d0\u30f3\u304c\u308f\u308a\u306b\u3057\u3066\u30ad\u30fc\u30db\u30eb\u30c0\u30fc\u3092\u4f5c\u308d\u3046\uff01\r\n

\u30d7\u30e9\u30b9\u30c1\u30c3\u30af\u304a\u5f01\u5f53\u7bb1\u3092\u4f7f\u3063\u305f\u30ad\u30fc\u30db\u30eb\u30c0\u30fc\u4f5c\u308a\uff01<\/a><\/p>\r\n

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\u30c6\u30ec\u30d3\u756a\u7d44\u76e3\u4fee\u30fb\u30a4\u30d9\u30f3\u30c8\u7b49\u306e\u304a\u77e5\u3089\u305b<\/strong><\/b><\/span><\/h3>\r\n