About The Scientist Lounge
What is this?
The Scientist Lounge is a collection of free, interactive science simulations that run directly in your browser. No downloads, no accounts, no paywalls — just science you can play with. The site currently focuses on physics, with plans to expand into chemistry and other disciplines.
Why it exists
Science is easier to understand when you can see it in action. Textbook diagrams are static, and videos only show one scenario. Simulations let you change the variables yourself and watch what happens — building real intuition for how the world works.
The Scientist Lounge was created to make that kind of hands-on exploration available to anyone with a web browser. Every simulation is designed for students, curious learners, and anyone who wants to understand the science behind everyday phenomena.
What you'll find here
- Interactive simulations — currently covering Newtonian mechanics (projectile motion, collisions, pendulums, springs, and more), with new topics and disciplines added regularly.
- Companion articles — each simulation has an article explaining the science behind it, written for a high school to early university audience.
- Real-time readouts — every simulation shows live values for velocity, acceleration, energy, and other quantities so you can connect the math to the motion.
How it's built
The entire site is built with vanilla JavaScript, HTML, and CSS — no frameworks, no external libraries. The simulations render on HTML Canvas 2D with accurate physics integration at 240 substeps per second.
How accurate are the simulations?
Every simulation on the site shares the same numerical engine, so a small predictable gap between the analytical formula and the on-screen readouts is universal — not specific to any one simulation. Three sources contribute to that gap.
Fixed-substep integration. Every simulation advances its physics state in steps of 1/240 of a second using explicit Euler updates of velocity and position. Each step accumulates a tiny floating-point rounding error; over a typical multi-second run this drifts the total energy or position by roughly 0.1 to 0.5 percent. Stiffer systems (high spring constants, large gravitational accelerations) drift slightly more; gentler systems drift less.
Boundary detection. Events that depend on a state variable crossing a threshold — a projectile landing when y reaches zero, two balls colliding when their centres come within 2·R, a pendulum bob reaching its tipping stop — are detected on the first substep where the threshold is crossed, not at the exact crossing instant. The simulator then nudges the state to a clean post-event configuration. This shaves or adds a fraction of a substep's worth of motion to the recorded readings.
Readout precision. The numbers in the live HUD are rounded to a fixed number of decimal places (typically two for speeds and times, three for momenta, integers for distances in kilometres). A true value of 40.825 m may display as 40.82 or 40.83 depending on rounding mode, even when the underlying float is exact.
Each simulation page has a "Source of Error" section that adds the physical idealizations specific to that model — what the simulation explicitly does NOT include (drag, rotation, finite stiffness, third bodies, relativity, etc.). The analytical prediction shown in the same section assumes the same physical idealizations as the simulation, so they cancel: only the three numerical sources above remain.
Contact
Have a question, suggestion, or found a bug? Reach out at thepassionatescientist@gmail.com.