Comparison

Relatively Simple vs Photronium

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Relatively Simple

This app offers an experiential explanation of Einstein's theory of Special Relativity. Designed by a Carnegie Mellon University professor, it breaks down complex concepts like spacetime and E=mc^2 for a general audience.

Highlights
  • Experiential learning approach
  • Explains Special Relativity
  • Demystifies complex physics concepts
  • Designed by university professor
  • Accessible for general audience
Features
Read full description

When people hear the term "Einstein's theory of Special Relativity", they automatically assume its above their heads. You hear terms like "Space Time" and the famous equation "e=mc^2" and it sounds way too abstract to understand for someone without a PhD in Physics. Designed by Carnegie Mellon University's Dr. Ira Rothstein, this app is aimed at experientially explaining Einstein's theory of special relativity to anybody.

About

Photronium

Access over 360 physics equations with clear explanations and powerful search tools. Test your knowledge with custom quizzes and learn offline anywhere, anytime. This educational reference is designed for learners of all levels.

Highlights
  • 360+ physics equations
  • Offline access
  • Intelligent Search
  • Symbol Search
  • Customizable quizzes
  • Bookmarking
Read full description

With over 360 physics equations explained in a clear, easy-to-understand way and a flexible search system, Photronium can be an immensely helpful tool for learners of any level. PHYSICS AT YOUR FINGERTIPS Look up any physics equation, with topics including: • Motion in One Dimension • Projectile Motion • Laws of Motion • Uniform Circular Motion • Work and Energy • Linear Momentum and Collisions • Rotation of Rigid Bodies • Universal Gravitation • Fluid Mechanics • Oscillatory Motion • Wave Motion • Sound Waves • Thermodynamics • Electromagnetism • Light and Optics • Relativity • Quantum Physics All available offline, so you can learn anywhere, anytime. MEMORY QUIZ Test your knowledge by taking quizzes! Bookmark any section that interests you, and Photronium will automatically create quizzes based on those bookmarks. INTELLIGENT SEARCH & SYMBOL SEARCH Just type anything. Intelligent Search can work with the most ambiguous descriptions, like “atom”, “lens”, “radiation”, “Newton”, and “phase angle”. And when you need to find a physics formula without any description, Symbol Search provides a discovery experience you’ve never seen before. FREE & NO ADS Photronium comes with over 360 physics equations, Intelligent Search, Symbol Search, Widgets, Bookmarks, Suggested Websites, and Dark Mode all available for free and ad-free. With Extras, you can purchase more features and support the app’s development. Have questions or feedback? From the app, open Extras and send a report.

Screenshots

Relatively Simple4 screens
Photronium4 screens

Verdict

The call

The clearest difference is in-app purchases: Relatively Simple at none against Photronium's 1. Relatively Simple also leads on iOS requirement (8.0 vs 16.4). On price, rating, review sentiment and ratings volume there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Photronium sells 1 one-off in-app purchase. Relatively Simple asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

On the App Store both sit at effectively the same score — 5.0 for Relatively Simple against 5.0 for Photronium. Both are backed by a comparable volume of ratings — 7 and 8 respectively. Written reviews split almost evenly too, at 100% and 100% positive.

UpkeepUpdate frequency

Both ship on a similar rhythm, roughly monthly. The most recent releases landed on September 19, 2026 and September 18, 2026 respectively.

Scorecard3 real differences · 7 level
Relatively Simple versus Photronium: the parameters behind the verdict, then further details
ParameterRelatively SimplePhotronium
PriceFreeFree
Rating5.0 (7 ratings)5.0 (8 ratings)
Positive reviews100.0% of reviews100.0% of reviews
Number of ratings78 — better
Update frequencyMonthlyMonthly
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree — betterFree with in-app purchases
DevicesiPhone, iPad, iPod — betteriPhone, iPad
Requires iOS8.0 — better16.4
Further details — not scored
Size434 MB59 MB
Age rating4+4+
DeveloperIra RothsteinHao Nguyen

Customer experience

Relatively Simple

All ratings7 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews1 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

Photronium

All ratings8 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews4 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

None

Relatively Simple

No in-app purchases

1 purchases

Photronium

One-time1
  • Multicolored Bookmarks$0.99

Questions

Is Relatively Simple free?
Relatively Simple is free to download, with no in-app purchases.
Is Photronium free?
Photronium is free to download, with in-app purchases available.
Which has better reviews, Relatively Simple or Photronium?
Relatively Simple and Photronium are both rated 5.0 out of 5 on the App Store, from 7 and 8 ratings respectively.
Do Relatively Simple or Photronium have ads?
Neither Relatively Simple nor Photronium shows ads.
Which is updated more often, Relatively Simple or Photronium?
Relatively Simple ships an update monthly, and Photronium monthly. Most recently, Relatively Simple was updated on September 19, 2026 and Photronium on September 18, 2026.

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