Life & fun · alternatives · 2026
24 alternatives to What if the speed of light was 5 km/h?
Special relativity simulator in which light crawls along at a human speed, so Lorentz contraction, aberration and Doppler shift happen at walking pace.
Below are 24 products that do a similar job, ranked by how close each is in meaning and then by launch-day votes.
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- 2PA
We have a black hole at home — with actual relativistic physics, live in your browser. I'm Sasha (Alexander) Plavin, an astrophysicist at Harvard's Black Hole Initiative studying quasars and black hole environments. I work with raytracing/radiative transfer simulations professionally, and wanted to make one anyone can play with — so I built this app. Put the black hole onto your screen (any browser), or directly into your room with AR or VR (requires WebXR, for example Chrome on Android, or any VR headset). When looking around, pay attention to unintuitive relativistic effects: rays…
Jul 2026 · blackhole.plav.in · its alternatives →
- 3IB
I built this because measuring my age in years felt boring—I wanted to see the kilometers. The first version only used Earth's orbital speed (~30km/s), but the number moved too slowly. To get the "existential dread" feeling, I switched to using the Milky Way's velocity relative to the CMB (~600km/s). The math takes some liberties (using scalar sum instead of vector) to make the speed feel "fast," but it gets the point across. Under the hood, it's a single HTML file with zero dependencies. No React, no build step. The main challenge was the canvas starfield—I had to pre-allocate the…
Jan 2026 · cosmic-odometer.vercel.app · its alternatives →
- 4RA
2021 · ramp-book.com · its alternatives →
- 5GI
Just for fun and self education, I've built this over a weekend to teach myself why orbits exist, not just show planets going around. Something that was never clearly explain to me in school. It opens with a guided tour that builds the idea up step by step: two bodies and the equal/opposite force, inertia (the Sun is removed and Earth just drifts straight), then "an orbit is falling and continuously missing," cosmic velocities with a little rocket, Voyager 1 & 2's real gravity assists (the clock runs the actual 1977–1989 dates so the planets orbit into their grand-tour alignment and the…
Jun 2026 · qunabu.github.io · its alternatives →
- 6
Google Translate for engineers working with motion
2017 · its alternatives →
- 7DK
2020 · github.com · its alternatives →
- 8RT
2025 · github.com · its alternatives →
- 9NV
2019 · github.com · its alternatives →
- 10DE
2015 · lewis500.github.io · its alternatives →
- 11OI
2016 · orbides.org · its alternatives →
- 12BB
Features include: - Several preset periodic orbits: the classic Figure-8, plus newly discovered 3D solutions from Li and Liao's recent database of 10,000+ orbits (https://arxiv.org/html/2508.08568v1) - Full 3D camera controls (rotate/pan/zoom) with body-following mode - Force and velocity vector visualization - Timeline scrubbing to explore the full orbital period The 3D presets are particularly interesting. Try "O₂(1.2)" or "Piano O₆(0.6)" from the Load Presets menu to see configurations where bodies weave in and out of the orbital plane. Most browser…
Nov 2025 · trisolarchaos.com · its alternatives →
- 13IW
I was playing around with fundamental constants and out popped 13.8 billion light years. What is going on? the wavelength of an electron mass photon / (2pi) * the charge radius of a proton / the black hole radius of a proton = 13.8 billion light years ((h / (m_e * c * 2pi)) * (h / (m_p * c * pi/2)) / (2G * m_p / c^2)) = 13.8 billion light years…
2021 · its alternatives →
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- 15AP
We ported pbrt-v4 to Julia and built it into a Makie backend. Any Makie plot can now be rendered with physically-based path tracing. Julia compiles user-defined physics directly into GPU kernels, so anyone can extend the ray tracer with new materials and media - a black hole with gravitational lensing is ~200 lines of Julia. Runs on AMD, NVIDIA, and CPU via KernelAbstractions.jl, with Metal coming soon. Demo scenes: github.com/SimonDanisch/RayDemo
Feb 2026 · makie.org · its alternatives →
- 16AS
The little particles will gravitate to your cursor (or touch location), and can even enter stable orbits if the conditions are right! Mainly an excuse for me to experiment with wasm and WebGL, but it makes for a surprisingly good fidget toy.
2024 · aestuans.github.io · its alternatives →
- 17A2
2017 · htmlpreview.github.io · its alternatives →
- 18AN
2013 · github.com · its alternatives →
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- 20
- 21
- 22
Particular Drift▲140Create flowing particle animations out of any image (FOSS)
2025 · its alternatives →
- 23IP
I started teaching my daughter physics by showing her how things actually work - plucking guitar strings to explain vibration, mixing paints to understand light, dropping objects to see gravity in action. She learned so much faster through hands-on exploration than through books or videos. That's when I realized: what if I could recreate these physical experiments as interactive simulations? Lumen is the result - an interactive physics playground covering sound, light, motion, life, and mechanics. Each module lets you manipulate variables in real-time and see/hear the results…
Jan 2026 · projectlumen.app · its alternatives →
- 24IB
Mar 2026 · structuredlabs.github.io · its alternatives →
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Ranked by how close each launch is in meaning, then by votes. Prices were read from each product’s own site when checked and can change. Refine with your own description →