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Problem: A scientist is cooling a sample of helium gas. The initial temperature is 4.2 K. Each cooling stage reduces the temperature by half of the remaining distance to absolute zero (0 K). How many stages are needed to reach exactly 0 K? Step 1: Understand the rule. The distance to 0 K is halved each stage. Step 2: Start at 4.2 K. Distance to 0 K is 4.2 K. Step 3: Stage 1: New temp = 4.2 / 2 = 2.1 K. Step 4: Stage 2: New temp = 2.1 / 2 = 1.05 K. Step 5: Stage 3: New temp = 1.05 / 2 = 0.525 K. Step 6: As you can see, the temperature gets smaller and smaller but never becomes exactly 0. No matter how many stages you do, you approach 0 but never hit it. Conclusion: It is impossible to reach absolute zero in a finite number of steps. This illustrates the Third Law.