🌡️ 负数：0 左边的世界🌡️ Negative Numbers: the World Left of Zero
你早就会数 1、2、3 了。可是冬天温度计上的“零下”、电梯按钮上的“-1 层”、账单上的“欠款”，都躲到了 0 的左边。这一片，我们跟着 🧮 小算盘机器人去 0 左边逛逛。You've counted 1, 2, 3 since forever. But “below zero” on a winter thermometer, “floor -1” in an elevator, and “money owed” on a bill all hide to the left of 0. In this leaf, 🧮 the tiny abacus robot takes you on a tour left of zero.
第 1 步：0 的左边还有世界Step 1: There's a world left of 0
先看两样你天天见到的东西：温度计和电梯。Start with two things you see every day: a thermometer and an elevator.
温度计上，0°C 是一条分界线：上面越往上越热，下面越往下越冷，-5°C 就住在 0 的下面。电梯按钮也一样：1 层、0 层，再往下是 -1 层、-2 层。0 不是尽头，只是“分界点”——比 0 小的数，就写在它的左边，读作“负几”。On a thermometer, 0°C is a dividing line: up means warmer, down means colder, and -5°C lives below 0. Elevator buttons work the same way: floors 1, 0, then -1, -2 going down. Zero is not the end — just the boundary. Numbers smaller than 0 are written to its left, with a minus sign in front.
那“零下”和“地下”能不能画在同一张图上？Can “below zero” and “below ground” be drawn on one single picture?
第 2 步：在数轴上跨过 0Step 2: Crossing 0 on the number line
把温度计横过来，就是数轴：0 在中间，右边是 1、2、3……左边是 -1、-2、-3……小机器人从 +2 出发，向左走 5 格、跨过 0，就停在了 -3；再向右走回来，又回到 +2。记住方向：往左是变小，往右是变大。Lay the thermometer sideways and you get the number line: 0 in the middle, 1, 2, 3… to the right, and -1, -2, -3… to the left. The robot starts at +2, walks 5 steps left, crosses 0, and lands on -3; walk back right and it returns to +2. Remember the direction: left means smaller, right means bigger.
数轴上的“左右”，在生活里对应什么？What do “left” and “right” on the line mean in real life?
第 3 步：账单里的正负Step 3: Positive and negative on a bill
钱包也有一条自己的数轴。收入 +50 元，是往右走；支出 -35 元，是往左走；两条合起来，结余 +15 元——结果还是正的。正号“+”表示增加，负号“-”表示减少，它们记录的是同一个数的两个方向。Your wallet has its own number line. Income +50 means walk right; spending -35 means walk left; together they leave a balance of +15 — still positive. The plus sign means “gain”, the minus sign means “lose” — two directions of the same idea.
🎮 你来当领航员（30 秒）🎮 Your turn: pilot the pointer (30 seconds)
道理讲完了。拖动滑块，把红色指针开到目标位置——4 个都命中，就撒花。Theory done. Drag the slider and drive the red pointer to each target — hit all 4 and confetti falls.
一句话记住它：0 是分界线，左边住着负数；越往左数越小，跨过 0 要经过 0。Remember it in one line: zero is the boundary; negative numbers live to its left, further left means smaller, and crossing zero means passing through it.
比 0 小的数叫负数，写作“-几”，读作“负几”Numbers smaller than 0 are negatives, written with a minus sign数轴上越往左越小：-4 ＜ -1 ＜ 0 ＜ 3On the number line, further left is smaller: -4 < -1 < 0 < 3正负号用来记录相反方向：收入 +50、支出 -35Signs record opposite directions: income +50, spending -35
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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