The short answer, and in my view the most intuitive, is that nothing can go faster than the speed of light, because nothing can travel at any other speed. There is only one speed in the whole Universe, and that’s the speed of light.
The only thing that changes about an object’s motion as it (apparently, from a three-dimensional perspective) “speeds up” or “slows down” is its direction of travel through four dimensional spacetime. When an object appears stationary (to some observer) it is moving entirely in the time direction of spacetime, at a rate of one second per second.
It is in fact misleading to call it “speed of light”, because the maximum speed in the universe actually has nothing to do with light. It just so happened that light was the first thing we humans discovered to travel at this cosmic maximum speed. We now know that gravity and strong nuclear force also propagate at the same speed. A better name for it would be “speed of causality”. This is the maximum speed at which an effect can be generated from its cause. All events in the universe are governed by the fundamental forces of nature. Photons, gravitons and gluons, being the respective massless force carriers of light, gravity and strong nuclear force, all travel at the speed of causality. The weak nuclear force, having two massive force carriers the W and Z bosons, actually propagates below the speed of light.
When you’re in love, you want to tell the world. This book is a personal statement, reflecting my lifelong love affair with science.
But there’s another reason: science is more than a body of knowledge; it is a way of thinking. I have a foreboding of an America in my children or grandchildren’s time — when the US is a service and information economy; when nearly all the key manufacturing industries have slipped away to other countries; when awesome technological powers are in the hands of a very few, and no one representing the public interest can even grasp the issues; when the people have lost the ability to set their own agendas or knowledgeably question those in authority; when, clutching our crystals and nervously consulting our horoscopes, our critical faculties in decline, unable to distinguish between what feels good and what’s true, we slide, almost without noticing, back into superstition and darkness. The dumbing down of America is most evident in the slow decay of substantive content in the enormously influential media, the 30-second sound bites (now down to 10 seconds or less), lowest common denominator programming, credulous presentations on pseudoscience and superstition, but especially a kind of celebration of ignorance.
Science (from the Latin word scientia, meaning “knowledge”) is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
Scientists usually take for granted a set of basic assumptions that are needed to justify the scientific methods:
- that there is an objective reality shared by all rational observers
- that this objective reality is governed by natural laws
- that these laws can be discovered by means of systematic observation and experimentation.
The most vitally characteristic fact about mathematics is, in my opinion, its quite peculiar relationship to the natural sciences, or, more generally, to any science which interprets experience on a higher than purely descriptive level.
Most people, mathematicians and others, will agree that mathematics is not an empirical science, or at least that it is practiced in a manner which differs in several decisive respects from the techniques of the empirical sciences. And, yet, its development is very closely linked with the natural sciences. One of its main branches, geometry, actually started as a natural, empirical science. Some of the best inspirations of modern mathematics (I believe, the best ones) clearly originated in the natural sciences. The methods of mathematics pervade and dominate the “theoretical” divisions of the natural sciences. In modern empirical sciences it has become more and more a major criterion of success whether they have become accessible to the mathematical method or to the near-mathematical methods of physics. Indeed, throughout the natural sciences an unbroken chain of successive pseudomorphoses, all of them pressing toward mathematics, and almost identified with the idea of scientific progress, has become more and more evident. Biology becomes increasingly pervaded by chemistry and physics, chemistry by experimental and theoretical physics, and physics by very mathematical forms of theoretical physics.
There is a quite peculiar duplicity in the nature of mathematics. One has to realize this duplicity, to accept it, and to assimilate it into one’s thinking on the subject. This double face is the face of mathematics, and I do not believe that any simplified, unitarian view of the thing is possible without sacrificing the essence.
Sound is produced by a mechanical means. Sound travels in waves and exists only within a medium. Light also travels in a wavelike manner but light has electric and magnetic properties and accordingly it is an electromagnetic wave. Sound travels at 343 m/s in air and light travels through all mediums at almost 300M m/s. Light travels 1M times faster than sound.
Sound is also classified by wavelength, but keep in mind that sound is produced by mechanical means. Sound does not have the electrical and magnetic fields that visible light does.
We typically define science as a practical and intellectual activity surrounding the systematic analysis, examination, and deconstruction of the physical and natural world through observation and experimentation.
Scientists use what we know to find out what we don’t know and use all possible resources to find out more about what we don’t know.
Học sinh được dạy “Toán là chìa khoá cho mọi vấn đề,” nhưng học xong không biết dùng nó mở bất kỳ vấn đề nào trong cuộc sống; cuối cùng đành an ủi rằng nó giúp ích cho tư duy, mặc dù không biết sự giúp đỡ ở mức nào, và có cách nào hiệu quả hơn không.
Momen xoắn được xem là đại lượng đặc trưng cho khả năng chịu tải tức thời của động cơ xe hơi. Đây là đại lượng có hướng, nên giá trị thu về còn tùy thuộc vào hệ quy chiếu. Do đó, để đo lường sức mạnh của một chiếc xe thì người ta hay nhắc tới thông số momen xoắn. Thông số càng cao thì lực quay của bánh xe càng mạnh.
Ngoài ra, giá trị này còn phụ thuộc vào tốc độ vòng tua máy và tại một vòng tua nào đó thì nó sẽ đạt giá trị cực đại. Trong bảng thông số động cơ, momen xoắn được ghi chính là giá trị cực đại.
Hiểu đơn giản là momen xoắn càng nhiều thì động cơ có thể tạo ra công suất càng lớn. Động cơ xe có nhiều momen xoắn sẽ giúp xe tăng tốc nhanh hơn khi mới bắt đầu nổ máy.