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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>General Relativity Explained Simply</title>
    <script src="https://cdn.tailwindcss.com"></script>
    <script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.4.0/css/all.min.css">
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            transform-style: preserve-3d;
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            backface-visibility: hidden;
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        .concept-back {
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</head>
<body class="bg-gray-900 text-gray-100 min-h-screen">
    <div class="container mx-auto px-4 py-8">
        <!-- Header -->
        <header class="text-center mb-12">
            <h1 class="text-5xl font-bold mb-4 bg-gradient-to-r from-blue-400 to-purple-600 bg-clip-text text-transparent">
                General Relativity Made Simple
            </h1>
            <p class="text-xl text-gray-300 max-w-3xl mx-auto">
                Understanding Einstein's theory of gravity without the complex math
            </p>
        </header>

        <!-- Main Content -->
        <div class="grid grid-cols-1 lg:grid-cols-3 gap-8">
            <!-- Left Column - Core Concepts -->
            <div class="lg:col-span-2 space-y-8">
                <!-- Introduction -->
                <section class="bg-gray-800 rounded-xl p-6 shadow-lg">
                    <h2 class="text-3xl font-semibold mb-4 text-blue-400">
                        <i class="fas fa-atom mr-2"></i> What is General Relativity?
                    </h2>
                    <p class="mb-4 text-gray-300">
                        General Relativity is Einstein's theory of gravity that revolutionized our understanding of space, time, and the universe. It explains gravity not as a force, but as a curvature of spacetime caused by mass and energy.
                    </p>
                    <div class="flex flex-wrap gap-4 mt-6">
                        <div class="bg-blue-900/50 px-4 py-2 rounded-full flex items-center">
                            <i class="fas fa-ruler-combined mr-2 text-blue-300"></i>
                            <span>Space tells matter how to move</span>
                        </div>
                        <div class="bg-purple-900/50 px-4 py-2 rounded-full flex items-center">
                            <i class="fas fa-weight-hanging mr-2 text-purple-300"></i>
                            <span>Matter tells space how to curve</span>
                        </div>
                    </div>
                </section>

                <!-- Spacetime Visualization -->
                <section class="bg-gray-800 rounded-xl p-6 shadow-lg">
                    <h2 class="text-3xl font-semibold mb-4 text-purple-400">
                        <i class="fas fa-project-diagram mr-2"></i> Spacetime: The Fabric of the Universe
                    </h2>
                    <p class="mb-4 text-gray-300">
                        Imagine space and time are woven together into a 4-dimensional fabric called spacetime. Massive objects like stars and planets create "dents" in this fabric, and other objects move along these curves.
                    </p>
                    
                    <div class="space-time h-64 rounded-lg mt-6 relative flex items-center justify-center">
                        <div class="gravity-well w-32 h-32" style="bottom: 50%; left: 50%; transform: translate(-50%, 50%);"></div>
                        <div class="particle w-4 h-4" style="bottom: 30%; left: 30%;"></div>
                        <div class="particle w-4 h-4" style="bottom: 40%; left: 60%;"></div>
                        <div class="particle w-4 h-4" style="bottom: 70%; left: 20%;"></div>
                        <div class="absolute inset-0 flex items-center justify-center">
                            <div class="text-center px-4 py-2 bg-black/50 rounded-lg">
                                <p class="text-sm">Massive objects curve spacetime</p>
                                <p class="text-xs opacity-70">Smaller objects follow the curvature</p>
                            </div>
                        </div>
                    </div>
                    
                    <div class="mt-6 grid grid-cols-1 md:grid-cols-2 gap-4">
                        <div class="bg-gray-700/50 p-4 rounded-lg">
                            <h3 class="font-semibold text-blue-300 mb-2"><i class="fas fa-arrow-down mr-2"></i>Newton's View</h3>
                            <p class="text-sm text-gray-300">Gravity is a force that pulls objects together instantly across space.</p>
                        </div>
                        <div class="bg-gray-700/50 p-4 rounded-lg">
                            <h3 class="font-semibold text-purple-300 mb-2"><i class="fas fa-project-diagram mr-2"></i>Einstein's View</h3>
                            <p class="text-sm text-gray-300">Gravity is the curvature of spacetime caused by mass and energy.</p>
                        </div>
                    </div>
                </section>

                <!-- Key Concepts -->
                <section class="bg-gray-800 rounded-xl p-6 shadow-lg">
                    <h2 class="text-3xl font-semibold mb-6 text-green-400">
                        <i class="fas fa-lightbulb mr-2"></i> Key Concepts Simplified
                    </h2>
                    
                    <div class="grid grid-cols-1 md:grid-cols-2 gap-6">
                        <!-- Concept 1 -->
                        <div class="concept-card bg-gray-700/50 rounded-lg overflow-hidden h-full">
                            <div class="concept-inner relative w-full h-full">
                                <div class="concept-front p-4">
                                    <h3 class="font-bold text-xl mb-3 text-blue-300">
                                        <i class="fas fa-ruler-combined mr-2"></i> Curved Spacetime
                                    </h3>
                                    <p class="text-gray-300 text-sm">
                                        Massive objects like the Sun curve the spacetime around them. Planets orbit by following these curves, not because of a mysterious force.
                                    </p>
                                    <div class="mt-4 h-32 bg-gradient-to-br from-blue-900 to-blue-700 rounded flex items-center justify-center">
                                        <i class="fas fa-circle text-yellow-400 text-4xl"></i>
                                        <div class="absolute w-48 h-48 border-2 border-blue-300 rounded-full opacity-30"></div>
                                        <div class="absolute w-32 h-32 border-2 border-blue-300 rounded-full opacity-50"></div>
                                    </div>
                                </div>
                                <div class="concept-back absolute inset-0 bg-blue-900/80 p-4 flex flex-col justify-center">
                                    <h4 class="font-bold text-lg mb-2">Analogy</h4>
                                    <p class="text-sm">Like a bowling ball on a trampoline - it creates a dent that makes marbles roll around it.</p>
                                    <div class="mt-4 text-xs opacity-70">
                                        <i class="fas fa-info-circle mr-1"></i> The heavier the object, the deeper the "dent"
                                    </div>
                                </div>
                            </div>
                        </div>
                        
                        <!-- Concept 2 -->
                        <div class="concept-card bg-gray-700/50 rounded-lg overflow-hidden h-full">
                            <div class="concept-inner relative w-full h-full">
                                <div class="concept-front p-4">
                                    <h3 class="font-bold text-xl mb-3 text-purple-300">
                                        <i class="fas fa-clock mr-2"></i> Time Dilation
                                    </h3>
                                    <p class="text-gray-300 text-sm">
                                        Time runs slower in stronger gravitational fields. Your head ages faster than your feet (by a tiny amount)!
                                    </p>
                                    <div class="mt-4 h-32 relative bg-gradient-to-br from-purple-900 to-purple-700 rounded flex items-center justify-center">
                                        <div class="text-center">
                                            <div class="text-2xl font-mono">00:00:00</div>
                                            <div class="text-xs opacity-70">Earth surface</div>
                                        </div>
                                        <div class="absolute right-4 top-4 text-center">
                                            <div class="text-xl font-mono">00:00:01</div>
                                            <div class="text-xs opacity-70">Space</div>
                                        </div>
                                    </div>
                                </div>
                                <div class="concept-back absolute inset-0 bg-purple-900/80 p-4 flex flex-col justify-center">
                                    <h4 class="font-bold text-lg mb-2">GPS Needs Relativity</h4>
                                    <p class="text-sm">GPS satellites must account for time running faster in orbit (by 38 microseconds/day) or positions would be off by kilometers.</p>
                                </div>
                            </div>
                        </div>
                        
                        <!-- Concept 3 -->
                        <div class="concept-card bg-gray-700/50 rounded-lg overflow-hidden h-full">
                            <div class="concept-inner relative w-full h-full">
                                <div class="concept-front p-4">
                                    <h3 class="font-bold text-xl mb-3 text-green-300">
                                        <i class="fas fa-spinner mr-2"></i> Frame Dragging
                                    </h3>
                                    <p class="text-gray-300 text-sm">
                                        Rotating masses like Earth actually "drag" spacetime around with them, like stirring honey with a spoon.
                                    </p>
                                    <div class="mt-4 h-32 bg-gradient-to-br from-green-900 to-green-700 rounded flex items-center justify-center">
                                        <i class="fas fa-globe-americas text-white text-4xl animate-spin"></i>
                                        <div class="absolute w-48 h-48 border-2 border-green-300 rounded-full opacity-30 animate-spin"></div>
                                    </div>
                                </div>
                                <div class="concept-back absolute inset-0 bg-green-900/80 p-4 flex flex-col justify-center">
                                    <h4 class="font-bold text-lg mb-2">Gravity Probe B</h4>
                                    <p class="text-sm">This NASA experiment confirmed frame dragging by measuring how Earth's rotation twists spacetime around it.</p>
                                </div>
                            </div>
                        </div>
                        
                        <!-- Concept 4 -->
                        <div class="concept-card bg-gray-700/50 rounded-lg overflow-hidden h-full">
                            <div class="concept-inner relative w-full h-full">
                                <div class="concept-front p-4">
                                    <h3 class="font-bold text-xl mb-3 text-yellow-300">
                                        <i class="fas fa-expand mr-2"></i> Expanding Universe
                                    </h3>
                                    <p class="text-gray-300 text-sm">
                                        General Relativity predicts the expansion of space itself, leading to our modern understanding of the Big Bang.
                                    </p>
                                    <div class="mt-4 h-32 bg-gradient-to-br from-yellow-900 to-yellow-700 rounded flex items-center justify-center">
                                        <div class="flex space-x-1">
                                            <div class="w-3 h-3 bg-white rounded-full"></div>
                                            <div class="w-3 h-3 bg-white rounded-full"></div>
                                            <div class="w-3 h-3 bg-white rounded-full"></div>
                                        </div>
                                        <div class="absolute inset-0 flex items-center justify-center">
                                            <div class="w-full h-full animate-pulse"></div>
                                        </div>
                                    </div>
                                </div>
                                <div class="concept-back absolute inset-0 bg-yellow-900/80 p-4 flex flex-col justify-center">
                                    <h4 class="font-bold text-lg mb-2">Dark Energy</h4>
                                    <p class="text-sm">The mysterious force accelerating the expansion of the universe is one of GR's biggest puzzles.</p>
                                </div>
                            </div>
                        </div>
                    </div>
                </section>

                <!-- Simplified Math -->
                <section class="bg-gray-800 rounded-xl p-6 shadow-lg">
                    <h2 class="text-3xl font-semibold mb-6 text-red-400">
                        <i class="fas fa-square-root-alt mr-2"></i> The Math Behind It (Simplified)
                    </h2>
                    
                    <div class="grid grid-cols-1 md:grid-cols-2 gap-6">
                        <!-- Einstein's Equation -->
                        <div class="equation-box p-4 border border-gray-700 rounded-lg">
                            <h3 class="font-bold text-lg mb-3 text-red-300">
                                Einstein's Field Equations
                            </h3>
                            <div class="text-center my-4 text-2xl font-math">
                                G<sub>ΞΌΞ½</sub> = 8Ο€G/c<sup>4</sup> T<sub>ΞΌΞ½</sub>
                            </div>
                            <p class="text-sm text-gray-300">
                                This is the core equation of General Relativity. It relates the curvature of spacetime (left side) to the matter and energy content (right side).
                            </p>
                            <div class="mt-4 grid grid-cols-2 gap-2 text-xs">
                                <div class="bg-gray-700/50 p-2 rounded">
                                    <span class="font-bold text-red-300">G<sub>ΞΌΞ½</sub></span>
                                    <p>Curvature of spacetime</p>
                                </div>
                                <div class="bg-gray-700/50 p-2 rounded">
                                    <span class="font-bold text-blue-300">T<sub>ΞΌΞ½</sub></span>
                                    <p>Matter/energy content</p>
                                </div>
                            </div>
                        </div>
                        
                        <!-- Tensors Simplified -->
                        <div class="equation-box p-4 border border-gray-700 rounded-lg">
                            <h3 class="font-bold text-lg mb-3 text-purple-300">
                                Tensors Made Simple
                            </h3>
                            <div class="tensor-visualization h-24 rounded-lg mb-4 flex items-center justify-center">
                                <div class="bg-black/70 px-4 py-2 rounded">
                                    <span class="font-mono">Multi-dimensional arrays</span>
                                </div>
                            </div>
                            <p class="text-sm text-gray-300">
                                Tensors are mathematical objects that generalize numbers, vectors, and matrices. In GR, they describe curvature and energy in all spacetime directions.
                            </p>
                            <div class="mt-3 flex space-x-2 text-xs">
                                <div class="bg-purple-900/50 px-2 py-1 rounded">Scalar (0D)</div>
                                <div class="bg-blue-900/50 px-2 py-1 rounded">Vector (1D)</div>
                                <div class="bg-green-900/50 px-2 py-1 rounded">Matrix (2D)</div>
                                <div class="bg-red-900/50 px-2 py-1 rounded">Tensor (nD)</div>
                            </div>
                        </div>
                    </div>
                    
                    <div class="mt-6 bg-gray-700/50 p-4 rounded-lg">
                        <h3 class="font-bold text-lg mb-3 text-yellow-300">
                            <i class="fas fa-brain mr-2"></i> Intuitive Understanding
                        </h3>
                        <p class="text-sm text-gray-300 mb-4">
                            You don't need to solve these equations to grasp the key ideas. Think of spacetime as a flexible rubber sheet:
                        </p>
                        <div class="flex items-start">
                            <div class="mr-4 text-yellow-300 text-2xl">
                                <i class="fas fa-arrow-right"></i>
                            </div>
                            <div>
                                <p class="text-sm">
                                    <span class="font-bold">More mass</span> β†’ <span class="text-blue-300">Deeper curvature</span> β†’ <span class="text-purple-300">Stronger "gravity"</span>
                                </p>
                                <p class="text-sm mt-2">
                                    <span class="font-bold">Faster motion</span> β†’ <span class="text-green-300">More time dilation</span> β†’ <span class="text-red-300">Clocks run slower</span>
                                </p>
                            </div>
                        </div>
                    </div>
                </section>
            </div>

            <!-- Right Column - Interactive Elements -->
            <div class="space-y-8">
                <!-- Gravity Simulator -->
                <section class="bg-gray-800 rounded-xl p-6 shadow-lg">
                    <h2 class="text-2xl font-semibold mb-4 text-blue-400">
                        <i class="fas fa-gamepad mr-2"></i> Gravity Simulator
                    </h2>
                    <div class="space-time h-64 rounded-lg relative" id="gravityCanvas">
                        <div class="gravity-well w-20 h-20 absolute" id="centralMass" style="bottom: 50%; left: 50%; transform: translate(-50%, 50%);"></div>
                        <div class="particle w-3 h-3 absolute" id="orbitingObject" style="bottom: 30%; left: 50%; transform: translate(-50%, 50%);"></div>
                        <div class="absolute bottom-4 left-0 right-0 flex justify-center">
                            <button id="startOrbit" class="bg-blue-600 hover:bg-blue-700 px-4 py-2 rounded-lg text-sm">
                                <i class="fas fa-play mr-1"></i> Start Orbit
                            </button>
                        </div>
                    </div>
                    <div class="mt-4 grid grid-cols-2 gap-2">
                        <div>
                            <label class="text-xs block mb-1">Mass Size</label>
                            <input type="range" id="massSize" min="10" max="50" value="20" class="w-full">
                        </div>
                        <div>
                            <label class="text-xs block mb-1">Orbit Speed</label>
                            <input type="range" id="orbitSpeed" min="1" max="10" value="5" class="w-full">
                        </div>
                    </div>
                    <div class="mt-4 text-xs text-gray-400">
                        <i class="fas fa-info-circle mr-1"></i> Adjust sliders to see how mass and speed affect the orbit
                    </div>
                </section>

                <!-- Time Dilation Calculator -->
                <section class="bg-gray-800 rounded-xl p-6 shadow-lg">
                    <h2 class="text-2xl font-semibold mb-4 text-purple-400">
                        <i class="fas fa-clock mr-2"></i> Time Dilation Calculator
                    </h2>
                    <div class="mb-4">
                        <label class="block text-sm mb-1">Gravitational Field Strength</label>
                        <select id="gravityField" class="w-full bg-gray-700 border border-gray-600 rounded px-3 py-2 text-sm">
                            <option value="earth">Earth Surface (1g)</option>
                            <option value="sun">Sun Surface (28g)</option>
                            <option value="neutron">Neutron Star (10^11g)</option>
                            <option value="blackhole">Black Hole (∞)</option>
                        </select>
                    </div>
                    <div class="mb-4">
                        <label class="block text-sm mb-1">Time Duration</label>
                        <div class="flex">
                            <input type="number" id="timeInput" value="1" class="flex-1 bg-gray-700 border border-gray-600 rounded-l px-3 py-2 text-sm">
                            <select id="timeUnit" class="bg-gray-700 border border-gray-600 rounded-r px-3 py-2 text-sm">
                                <option value="seconds">Seconds</option>
                                <option value="minutes">Minutes</option>
                                <option value="hours">Hours</option>
                                <option value="days">Days</option>
                                <option value="years">Years</option>
                            </select>
                        </div>
                    </div>
                    <button id="calculateDilation" class="w-full bg-purple-600 hover:bg-purple-700 px-4 py-2 rounded-lg text-sm mb-4">
                        <i class="fas fa-calculator mr-1"></i> Calculate Time Difference
                    </button>
                    <div id="dilationResult" class="hidden bg-gray-700/50 p-3 rounded-lg text-sm">
                        <div class="flex justify-between mb-2">
                            <span>Local Time:</span>
                            <span id="localTime" class="font-mono">1.00 sec</span>
                        </div>
                        <div class="flex justify-between">
                            <span>Distant Observer:</span>
                            <span id="observerTime" class="font-mono">1.00 sec</span>
                        </div>
                        <div class="mt-2 text-xs text-gray-400">
                            <i class="fas fa-info-circle mr-1"></i> Time runs slower in stronger gravity
                        </div>
                    </div>
                </section>

                <!-- GR Predictions -->
                <section class="bg-gray-800 rounded-xl p-6 shadow-lg">
                    <h2 class="text-2xl font-semibold mb-4 text-green-400">
                        <i class="fas fa-check-circle mr-2"></i> GR Predictions
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                    <div class="space-y-4">
                        <div class="flex items-start">
                            <div class="bg-green-900/50 rounded-full w-6 h-6 flex items-center justify-center mr-3 mt-1 flex-shrink-0">
                                <i class="fas fa-check text-xs"></i>
                            </div>
                            <div>
                                <h3 class="font-semibold">Gravitational Lensing</h3>
                                <p class="text-xs text-gray-400">Light bends around massive objects, creating multiple images of distant galaxies.</p>
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                        <div class="flex items-start">
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                                <i class="fas fa-check text-xs"></i>
                            </div>
                            <div>
                                <h3 class="font-semibold">Black Holes</h3>
                                <p class="text-xs text-gray-400">Regions where spacetime curvature becomes infinite - first image captured in 2019.</p>
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                        <div class="flex items-start">
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                                <i class="fas fa-check text-xs"></i>
                            </div>
                            <div>
                                <h3 class="font-semibold">Gravitational Waves</h3>
                                <p class="text-xs text-gray-400">Ripples in spacetime detected in 2015 from colliding black holes.</p>
                            </div>
                        </div>
                        <div class="flex items-start">
                            <div class="bg-green-900/50 rounded-full w-6 h-6 flex items-center justify-center mr-3 mt-1 flex-shrink-0">
                                <i class="fas fa-check text-xs"></i>
                            </div>
                            <div>
                                <h3 class="font-semibold">Mercury's Orbit</h3>
                                <p class="text-xs text-gray-400">Explained the precession of Mercury's orbit that Newton couldn't.</p>
                            </div>
                        </div>
                    </div>
                </section>

                <!-- Learn More -->
                <section class="bg-gray-800 rounded-xl p-6 shadow-lg">
                    <h2 class="text-2xl font-semibold mb-4 text-yellow-400">
                        <i class="fas fa-book-open mr-2"></i> Learn More
                    </h2>
                    <div class="space-y-3">
                        <a href="#" class="flex items-center p-3 bg-gray-700/50 hover:bg-gray-700 rounded-lg transition">
                            <div class="bg-blue-900/50 p-2 rounded-lg mr-3">
                                <i class="fas fa-video"></i>
                            </div>
                            <div>
                                <h3 class="font-medium">Video Explanations</h3>
                                <p class="text-xs text-gray-400">Visual guides to GR concepts</p>
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                                <h3 class="font-medium">Beginner Books</h3>
                                <p class="text-xs text-gray-400">GR without heavy math</p>
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                                <h3 class="font-medium">Online Courses</h3>
                                <p class="text-xs text-gray-400">Step-by-step learning</p>
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        <!-- Footer -->
        <footer class="mt-16 pt-8 border-t border-gray-800 text-center text-gray-500 text-sm">
            <p>General Relativity Explained Simply - A visualization tool for understanding Einstein's theory</p>
            <p class="mt-2">Β© 2023 Science Education Project</p>
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    </div>

    <script>
        // Gravity Simulator Animation
        document.getElementById('startOrbit').addEventListener('click', function() {
            const orbitingObject = document.getElementById('orbitingObject');
            const massSize = parseInt(document.getElementById('massSize').value);
            const speed = parseInt(document.getElementById('orbitSpeed').value);
            const centralMass = document.getElementById('centralMass');
            
            // Update central mass size
            centralMass.style.width = `${massSize}px`;
            centralMass.style.height = `${massSize}px`;
            
            // Reset position
            orbitingObject.style.transition = 'none';
            orbitingObject.style.left = '50%';
            orbitingObject.style.bottom = '30%';
            orbitingObject.style.transform = 'translate(-50%, 50%)';
            
            // Orbit parameters
            const orbitRadius = 80; // pixels
            const centerX = 50; // percentage
            const centerY = 30; // percentage
            let angle = 0;
            
            // Start animation
            function animateOrbit() {
                angle += 0.02 * speed;
                const x = centerX + orbitRadius * Math.cos(angle);
                const y = centerY + orbitRadius * Math.sin(angle);
                
                orbitingObject.style.left = `${x}%`;
                orbitingObject.style.bottom = `${y}%`;
                
                // Continue animation
                animationId = requestAnimationFrame(animateOrbit);
            }
            
            // Start the animation
            let animationId = requestAnimationFrame(animateOrbit);
            
            // Update button state
            this.disabled = true;
            this.innerHTML = '<i class="fas fa-sync-alt mr-1"></i> Orbiting';
            
            // Allow restart by clicking again (though it will create multiple animations)
            setTimeout(() => {
                this.disabled = false;
                this.innerHTML = '<i class="fas fa-redo mr-1"></i> Restart';
            }, 2000);
        });
        
        // Update mass size display
        document.getElementById('massSize').addEventListener('input', function() {
            const size = this.value;
            document.getElementById('centralMass').style.width = `${size}px`;
            document.getElementById('centralMass').style.height = `${size}px`;
        });
        
        // Time Dilation Calculator
        document.getElementById('calculateDilation').addEventListener('click', function() {
            const field = document.getElementById('gravityField').value;
            const time = parseFloat(document.getElementById('timeInput').value);
            const unit = document.getElementById('timeUnit').value;
            
            // Convert to seconds for calculation
            let timeInSeconds = time;
            switch(unit) {
                case 'minutes': timeInSeconds *= 60; break;
                case 'hours': timeInSeconds *= 3600; break;
                case 'days': timeInSeconds *= 86400; break;
                case 'years': timeInSeconds *= 31536000; break;
            }
            
            // Simple dilation factors (not precise, for demonstration)
            let dilationFactor = 1;
            switch(field) {
                case 'earth': dilationFactor = 1.0000000007; break;
                case 'sun': dilationFactor = 1.00002; break;
                case 'neutron': dilationFactor = 1.5; break;
                case 'blackhole': dilationFactor = Infinity; break;
            }
            
            const observerTime = field === 'blackhole' ? '∞' : (timeInSeconds / dilationFactor).toFixed(6);
            
            document.getElementById('localTime').textContent = `${timeInSeconds.toFixed(2)} sec`;
            document.getElementById('observerTime').textContent = `${observerTime} sec`;
            document.getElementById('dilationResult').classList.remove('hidden');
        });
    </script>
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