How do I explore?
- Click any planet marker on the navigation bar to jump to that distance from the Sun.
- Use the playback buttons to travel at Voyager’s speed (📡) or at the speed of light (💫).
- Drag the slider for precise positioning anywhere from Mercury’s orbit to Alpha Centauri.
What should I notice?
- How does the Sun’s apparent size change as you move away?
- At what distance does the Sun start to look like just another star?
- How does brightness change compared to size? Are they changing at the same rate?
What about the data?
- Press Record Data at each planet to log the distance and brightness.
- Press Collect Data in the toolbar to send your log to Tuva.
- Look for a pattern between distance (AU) and brightness ratio — can you write an equation?
Standard addressed
5-ESS1-1 Support an argument that the apparent brightness of the Sun and stars is due to their relative distances from the Earth.
Design intent
- Brightness changes with distance. The Sun looks very different from Mercury than it does from Neptune — students can build intuition for this before touching the data.
- The solar system is vast. Even at the speed of light, meaningful changes in the Sun’s brightness take a long time to accumulate. The playback controls make that scale tangible.
- Our eyes can deceive us. Because of the inverse square law, brightness changes can be dramatic in the data yet nearly invisible to the naked eye — a key argument for why science relies on instruments.
Discussion prompts
- “What is an AU? What is a light minute? Why don’t we use miles to describe these distances?”
- “On our slider, 2.5 minutes and 1 hour look almost as far apart as 1 day and 1 month. Why?”
- “Why does the Sun’s brightness seem to drop fast when you’re close, but barely change at all when you’re far away?”
- “Based on the brightness trend, why do scientists use instruments rather than just their eyes to study stars?”
- “Record brightness and distance at several locations. How does brightness change as distance increases?”
Assumptions and simplifications
- Brightness follows the inverse square law exactly: B = 1/d² where d is in AU.
- The Sun’s apparent size also scales as 1/d (angular diameter).
- Voyager 1’s speed is modeled as 3.58 AU/year (its approximate current speed relative to the Sun).
- Distances for planets are approximate mean orbital distances.
- Alpha Centauri is shown at 268,000 AU (4.24 light-years), illustrating the vast gulf between stars.