一（九十二）：一个关于超速的笑话
据说美国物理学会曾经制作过一张红色的汽车保险杠贴纸，上面写着：
if this sticker is blue , then you are driving too fast.
意思是说：
如果这个贴纸是蓝色的，那么你开得太快了。
没有一点物理学知识，还真看不懂这个笑话。
这牵扯到“多普勒效应”。
怎么理解呢？以火车为例：
当你站在铁轨旁，一列火车鸣着汽笛朝你开来，你会发现汽笛声音越来越响的同时，音调越来越尖；当火车开过去离你越来越远时，汽笛声音越来越弱的同时，音调越来越低沉。
这就是多普勒效应的表现，汽笛发出的声波在接近你的时候，周期变短，频率变高；在远离你的时候，周期变长，频率变低。
多普勒效应是说：物体辐射的波长因为波源和观测者的相对运动而产生变化。
声波是这样，光波也是这样。
可见波的光谱如下：
图源：wikimedia
按照多普勒原理：如果光源离你而去，光的频率就会变低，表现在颜色上就会发红，叫做“红移”；如果光源是向你接近，光的频率就会变高，表现出来就是这个光的颜色会偏蓝，叫做“蓝移”。
科学家们就是依靠观察到星系普遍发生红移现象，才判定宇宙还在不停地向外扩张，宇宙大爆炸的威力仍在持续。
看了这些，你应该能看明白上面的那个笑话了吧~~
参考文献：
百度百科：多普勒效应
Posted using Partiko iOS
赞！
Posted using Partiko iOS
Congratulations! This post has been upvoted from the communal account, @minnowsupport, by julian2013 from the Minnow Support Project. It's a witness project run by aggroed, ausbitbank, teamsteem, someguy123, neoxian, followbtcnews, and netuoso. The goal is to help Steemit grow by supporting Minnows. Please find us at the Peace, Abundance, and Liberty Network (PALnet) Discord Channel. It's a completely public and open space to all members of the Steemit community who voluntarily choose to be there.
If you would like to delegate to the Minnow Support Project you can do so by clicking on the following links: 50SP, 100SP, 250SP, 500SP, 1000SP, 5000SP.
Be sure to leave at least 50SP undelegated on your account.
你今天过的开心吗？这是哪里？你是谁？我为什么会来这边？你不要给我点赞不要点赞，哈哈哈哈哈哈。假如我的留言打扰到你，请回复“取消”。
用笑話來寫 cn-stem 輕輕鬆鬆，並且容易入腦。
現代的科普節目，都是使用這方式，更容易讓市民記憶。
@teamcn-shop
哈哈，不知道某人怎么看
Posted using Partiko iOS
@honoru给您叫了一份外卖！
由 @ericet阿龙 @softmetal阿虎 @honoru阿豹 新手村龙虎豹组合 迎着暴雨 开着巴士给您送来
珍珠奶茶
吃饱了吗？跟我猜拳吧！ 石头，剪刀，布～
如果您对我的服务满意，请不要吝啬您的点赞～
@onepagex
This post has received a free upvote by @OnePageX
This bot is sponsored by OnePageX.com! To use it, simply reply to your post with @onepagex and you will get an upvote!
OnePageX.com is the simplest cryptocurrency conversion tool online!
This post has been voted on by the SteemSTEM curation team and voting trail in collaboration with @curie.
If you appreciate the work we are doing then consider voting both projects for witness by selecting stem.witness and curie!
For additional information please join us on the SteemSTEM discord and to get to know the rest of the community!
雖然是一則笑話，但是還是帶有教育性。👍
Posted using Partiko Android