How do cats purr?
Cats purr when they feel happy, but no one knows how. When they purr, you don’t even hear their heart beating!
Scientists say cats make the vibrating sound with their vocal chords. Its frequency accelerates healing and reduces pain, which is why cats purr when they are stressed or hurt.
Where did some creatures come from?
Many species don’t have any ancestors. No one knows exactly when amphibians evolved from fish because the first land animals had well-developed limbs and heads.
It’s also said that dinosaurs became extinct after a natural cataclysm 65 million years ago. At the same time, species of mammals appeared from nowhere.
What was the "gelatinous" rain?
An unusual phenomenon occurred in Oakville, Washington, in August 1994. Instead of rain, jelly-like substances fell from the sky. The next day, dozens of people got flu-like symptoms.
Scientists analyzed the substance: it contained two types of bacteria, one of which is usually found in the human digestive system. They couldn’t find a connection between the bacteria and the mysterious epidemic.
Why do we dream?
Some believe that dreams are random images and brain waves. Others consider them subconscious desires, unsolved problems, and experiences.
The study of dreams is called oneirology. Scientists claim that dreams symbolize something hidden deep in the human psyche, but no one knows what exactly.
猫怎么样？
当他们感到快乐时，猫ats。声，但没有人知道如何。当他们呃，你甚至不听到他们的心跳！
科学家们说，猫会用声带和弦来振动声音。它的频率加速愈合并减轻疼痛，这就是为什么当他们受到压力或受伤时，猫会呜咽。
些动物来自哪里？
许多物种没有任何祖先。没有人知道两栖动物是否从鱼类发展而来，因为第一批土地动物有四肢和头部发育良好。
也有人说恐龙在6500万年前的天灾后就灭绝了。同时，哺乳动物的种类也从无处出现。
什么是“凝胶状”的雨？
1994年8月在华盛顿的奥克维尔出现了一个不寻常的现象，而不是下雨，像果冻般的物质从天上掉下来。第二天，几十人患有流感样症状。
科学家分析了物质：它含有两种类型的细菌，其中一种通常在人类消化系统中发现。他们找不到细菌和神秘的流行病之间的联系。
为什么我们梦想？
有人认为梦想是随机的图像和脑波。其他人认为他们是潜意识，未解决的问题和经验。
梦想的研究被称为一维学。科学家们说，梦想象征着人类心灵深处隐藏的东西，但没有人知道究竟是什么。
Above images are downloaded from : https://google.com
Thanks to 
Original post : https://brightside.me/wonder-curiosities/11-surprising-mysteries-scientists-cant-explain-301860/