# Radioactivity vs RelativityTheory

The clearest difference is update cadence: RelativityTheory at every 3 weeks against Radioactivity's every 36 months. RelativityTheory also leads on device support (3 vs 1). Radioactivity's advantage is iOS requirement (12.0 vs 14.4). On price, ads and in-app purchases there is nothing between them.

Radioactivity costs $0.99 and RelativityTheory $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Radioactivity ships an update every 36 months, RelativityTheory every 3 weeks. The most recent releases landed on September 16, 2026 and September 13, 2026 respectively.

## The numbers

| Metric | Radioactivity | RelativityTheory |
| --- | --- | --- |
| Price | $0.99 | $0.99 |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 36 months | **Every 3 weeks** |
| Size | 52 MB | 6 MB |
| Requires iOS | **12.0** | 14.4 |
| Devices | iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [www.ajaxmediatech.com](https://appshunter.io/developer/973768003) | [Takao Akatsu](https://appshunter.io/developer/1530946331) |

## What reviewers say

### Radioactivity

[App page](https://appshunter.io/ios/app/radioactivity-physics/id1136130171)

**Features:** macOS Compatibility

**In-app purchases:** none


### RelativityTheory

[App page](https://appshunter.io/ios/app/relativitytheory/id1620999874)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Radioactivity free?

Radioactivity costs $0.99, with no in-app purchases.

### Is RelativityTheory free?

RelativityTheory costs $0.99, with no in-app purchases.

### Do Radioactivity or RelativityTheory have ads?

Neither Radioactivity nor RelativityTheory shows ads.

### Which is updated more often, Radioactivity or RelativityTheory?

Radioactivity ships an update every 36 months, and RelativityTheory every 3 weeks. Most recently, Radioactivity was updated on September 16, 2026 and RelativityTheory on September 13, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*