Higher dimension------part 2

To understand what does the seventh dimension look like, we must look at the bigger scale of world.----the universe. In the six dimension, time has different branches, which means that our universe has different version of futures, and each branches of time lead to different ending of the universe. If we connect all of the possible ending of the universe, and treat them as a single dot, this dot will be the dot exists in the seventh dimension. This dot represents infinite numbers of the ending of universe. To draw a line in the seventh dimension, we must find another dot in the seventh dimension. This dot represents all of the possible ending of a different universe. In order to make the eighth dimension possible, there must be more than one universe. Those universes all have a different start, which means that they are not started by the big bang. Also, the law of physics in those universes may be different from our universe's. If you pick one universe from one of those different universes, connecting all of its possible ending and treat them as a single dot. You will get another dot in the seventh dimension. If you connect two dots, you will get a straight line in the seventh dimension. If you find another dot, and connect it to the line you just drew, you will get a split line. This split line is the eighth dimension. The nine dimension, similar to the third and the sixth dimension, is a curled lower dimension. In other words, if you curl the eight dimension, you will get the ninth dimension.

The concept of the tenth dimension is similar to that of the seventh dimension. To reach the tenth dimension, you have to find all of the dots (all of the possible futures of each universe) in the seventh dimension, connecting them and treat them as a single dot. In other way to explain it, you have to find all the possible universe, and all of their possible time line. After you find all of them , you will get infinite amount of dots. If you connect those dots and treat the infinite amounts of lines as a single dot, you will get a dot in the tenth dimension.

Visualizing the higher dimension is challenging. Nevertheless, with some examples, everyone can picturing the higher dimension effortlessly. I hope this article can help readers to understand the concept of the higher dimension. If you have any question after reading this article, you can leave your question on the comment.

Higher dimension------part1

In the previous article, I talked about the string theory and its role in the grand unify theory. String theory has been considered as a strong candidate of the grand unify theory. The math equations in string theory, just like those in other verified theories, are consistent. Also, the prediction of the string doesn't contradict itself. However, string theory can not be tested at the moment. Therefore, it can not be considered a comprehend theory so far. Even so, it is still a strong candidate of the grand unify theory, because its consistency in math equations and prediction.

In the string theory, the existence of 10 dimensions is described in the theory. Before the string theory predicted the 10th dimensional space, we thought that there were only four dimensions that exist in this world---- first dimension is length, second dimension is width, third dimension is depth, and the fourth dimension is time. Nowadays, people can easily imagine four dimensions. However, most of people have a hard time imagine the dimensions above the fourth dimension. To be able to imagine the higher dimensions, we must understand how the higher dimensions are added to the lower dimensions. Assume that an ant that is crawling on a newspaper is a two dimensional creature, it can only travel on the two dimensional surface. If this ant want to travel from one end to the other end of the newspaper, the fastest way is to travel a straight line across the surface of newspaper, because this ant exist in the two dimensional world. However, if we curl one end of the newspaper to the other end, this and can travel from one end to the other, without traveling through the surface of newspaper. Normally, the ant can only move on two dimension, but when the two dimensional world it exists in is curled up, the ant travel in the extra dimension, the third dimension. However, the ant can not feel the path it travel in the third dimension. It can only feel that it is traveling in a second dimensional path.

In the fourth dimension, time is a line. (It may not be straight) Every three dimensional objects in the universe are traveling in fourth dimension, but no anyone can feel the path it travel in the fourth dimension. (Just like a second dimension creature can't feel the path it travel in the third dimension) Therefore, even time is not a straight line, we still can't feel its curve. If you were a fourth dimensional creature, you would be able to see the beginning and the end of your life at the same time. Just like they are on the two ends of a tunnel.

In the fifth dimension, time is not a single line but a line that has different branches. In other world, time is a split line in fifth dimension. Our decision can influence which branches we will go.
When the fifth dimension is curled up, the sixth dimension arises. In the sixth dimension, we can travel between different branches of future without going back in time. In the fifth dimension, on the other hand, you have to go back in time first before you enter a different branch of future. If it is hard to imagine, you can think this way: In the fifth dimension, ti,e is a split line, if you are in one of the branches at the moment and you want to go to another branch, you have to go back to the conjunction of branches, and then choose a different branch to enter. It means that you have to travel back in time, and force yourself to make different decision, so that you can go to different version of future. In the sixth dimension, things are totally different. Since the sixth dimension is a curled fifth dimension. you can travel between different ends without going through the lines, which means that you don't have to go back to the conjunction, travel back in time, to go to different branch of future.

星際旅行

從以前開始，人們就不斷幻想著星際旅行，直到現在，還是有很多科幻情節是關於太空船進行宇宙探索的。然而，我們現在的科技還沒有辦法讓人類離開太陽系，到達更遙遠的行星或是恆星。因為我們現在所掌握的科技沒辦法讓太空船維持高速行駛很長一段時間，如果讓太空船移動得很快，燃料一下就耗盡了，如果讓太空船持續移動很長一段時間，速度又太慢了。雖然想進行星際旅行還有很多問題要解決，但這並不是完全不可能，有一些正在發展的科技在未來很有可能被應用在太空船上，讓人類可以進行星際旅行。

目前太空船的動力有兩種，一種是利用化學燃料燃燒後產生高溫氣體，將氣體排出後產生推進力。這種化學燃料引擎雖然能夠產生很大的推進力，但是燃料在短時間內就消耗完了。另一種則是離子引擎，運作原理是將類似燈絲的東西利用電流加熱，燈絲被加熱後會產生離子，把這些離子射出去就能產生推進力。但是這種引擎產生的推進力非常小，只適合用在長時間的太空任務上。目前科學家找到了能夠大大提升推進力的方法，就是使用高溫電漿。把氣體加熱到攝氏幾百萬度，使其達到電漿態，再把電漿排出即可得到很大的推進力。如果電漿能被運用在火箭上，太空船就能在數個月內往返火星。但是以上這些方法都不能產生足夠的能量讓人類到達距離地球最近的恆星。

想要更接近光速，我們必須要找出一個能產生大量能量的方法。有些科學家認為可以使用核融合產生能量，讓核融合產生的能量轉換成強大的推進力。此外，核融合的原料可以從宇宙中採集，所以不怕會耗盡燃料。但是，根據估計，要製造具有核融合引擎太空船並發射到太空是有難度的，因為這樣的太空船有好幾千噸重，所以想讓這樣的太空船上太空，可能要直接在太空中進行製造。此外，以現在的科技來說，人類還沒有辦法維持核融合狀態很長的時間，現在的核融合技術甚至還沒辦法運用在發電上，所以，想用核融合當作能量來源還有一段路要走。除了核融合，有些科學家也想過要使用核分裂(也就是核電廠發電的能量來源)，也做為太空船的能量來源。核分裂的確能產生很大的能量，而且以目前的技也能將核分裂做應用，但是基於安全上的考量，這個技術恐怕也很難實現。因為核分裂反應可能有失控的危險，所以利用核分裂產生能量推動太空船就像是在船上載一個威力強大的炸彈一樣，除此之外，在太空船被發射到太空的途中，核分裂的燃料很有可能會爆炸。所以想利用這項技術，還有很多難題要克服。

除了使用不同的燃料產生能量外，我們也可以利用行星的引力為太空船加速。當太空船靠進行星的時候，由於受到行星引力的影響而獲得加速度。如果行星的質量夠大，太空船就能達到接近光速的速度。這個我們稱之為"彈弓效應"

想要實現星際旅行，我們能夠研究的方向很多，彈是以現在的科技來說有些問題還無法克服，但是在科技更為進步的將來，我們或許能找到解答。

What do aliens look like?

In many movies. Aliens are depicted as a kind of hairless creature that have a pair of big eyes. Because of this, when we try to think of the image of aliens, an image of a creature with thin fingers, smooth skin, big eyes, and human shape may come into our minds. In addition, their size are believed to be small, about as tall as kids. The appearance of aliens only exists in our imagination because most people have never seen aliens. Although some people claim that they have met one, they have no convincing evidence or don't have any prove at all. Therefore, we can't describe the appearance of aliens precisely. Are they giants that are over three meters tall? Or are they dwarfs that is nearly as tall as kids? Fortunately, we can use science to roughly predict the size and the shape of aliens.

  To briefly predict the size of aliens, we have to introduce the "scale law". With this law, we can predict what will happen if an animal is increased or decreased in size. Take an ape as an example. if you increase an ape's size by ten times, its weight will be increased by 10*10*10=1000 times.(because when your size grows, you grow in three dimension) In the meanwhile, the strength of bones and muscles of this ape also increase. The cross-sectional area of bones and muscles goes up by the square of the distance increased, that is, by 10*10=100 times.
It means that if an ape becomes 10 times bigger, it becomes 100 times stronger. But let me remind you, if an animal is increased in size by ten times, its weight will be increased in 1000 times, and the strength of bones and muscles only increases by 100 times. Which mean that if an animal is really big, it may have a hard time moving itself, and may crush its bones when it try to make a step. Therefore, we can assume that the size of intelligent creatures in other planet may not be many times  bigger than humans on Earth. What about the small size aliens? Is that possible? Well, let the scale law gives us the answer. According the scale law, if you decrease an animal's size by ten times. its surface area decreases by 10*10=100 times. Since the heat emitted by the animals is decided by the amount of surface area, if an animal become 10 times smaller, its rate of heat lost will be 100 times smaller. However, the heat it can contain will also decreases because it become smaller. The amount of heat it can contain decreases by 1000 times. Since this animal's rate of heat lost decreases by 100 times and the heat it can contain decreases by 1000 times, its body temperature drops easily. Therefore, it have to constantly search for food, gaining enough energy to generate heat. Such an animal will spend most of time searching for food and are impossible to develop a civilization. Using this law, we can theorize that aliens in other planets would resemble us in size.

The prediction I made is based on an assumption that the environment, gravity of the planets that supports intelligent creatures resembles to those on Earth. If the gravity of a planet is weaker than that of Earth, there may be some intelligent lives that is large in size because their bones don't have to induce a lot of pressure. If s planet has higher temperatures, there may be some intelligent lives that are small in size because their lost of heat will be reduced.

The appearance of aliens is still a mystery because we can hardly find one. Nevertheless, we can still use some theories to make predictions. Maybe one day, people on Earth will have opportunities to interact with aliens.

人造重力

很多科幻情節裡，都會有太空船的出現。而在這些太空船上面，所有的船員都能夠安穩的站在地上。然而，大家都知道，太空是無重力的空間，除非距離一個星球很近，否則物體是不會受到重力牽引的，不受到重力影響的情況下，物體會呈現漂浮的狀態。在現代，太空站裡的太空人都必須克服沒有重力的生活，雖然飄在空中會讓人們覺得新奇，但是在那種狀態下生活一段時間是很不方便的。如果能在太空中創造重力，在太空中生活以及進行探測會便利許多。雖然人造重力還沒有被實現，但是科學家已經漸漸的掌握方法了。

我們之所以能站在地表上不會漂走是因為地球的引力。這個引力給了我們加速度，這個加速度約為９.8公尺／秒平方，這個加速度的方向指向地球的核心，由於地表的存在，我們才沒有持續往地球中心移動。而我們所具有的往地心移動的趨勢就是我們感受到的重力。之道這個概念後我們可以這樣想，假設今天有一艘太空船想前往月球，如果要讓太空船上的人感受到與地球上相等的重力，太空船必須要以9.8公尺／秒平方的加速度進行加速。在地球上，物體是向著地心移動的，而因為運動是相對的，在太空中如果人靜止，太空船移動，太空船上的人也會因為與在地球上同樣的原裡感受到重力，遠離太空船的趨勢就是太空人感受到的重力。但是，根據愛因斯坦的相對論，速度越快的物體越難被加速，如果要讓太空船維持一定的加速度，所需的能量會一直增加，加速的時間越長加速所需的能量就越高。所以，我們必須要想出一個更好的辦法，移個不需要消耗大量能源的方法。

想要產生人造重力還有一個辦法，就是讓太空站旋轉，如果太空站以一定的速度不停旋轉，太空人就能感受到重力。而為甚麼旋轉的太空站能夠讓上面的人感受到重力呢？如果你拿一條繩子綁住一顆球並且旋轉它的話你就會明白了。在球沒有旋轉的時候，繩子是有點鬆弛的，但是當你開始將球旋轉的時候，你會發現繩子被拉緊了，這是因為當球開始旋轉的時候，球會有一個遠離旋轉軸的趨勢，而繩子則拉住球，讓球不會往外飛走。一樣的道裡，如果太空站開始旋轉，上面的人會有遠離太空站中心的趨勢，而慨空站的牆壁擋住了上面的人，讓它們不會繼續往外移動，如此一來，太空人就會感受到類似重力的力量。著個力量我們稱之為向心力。向心力的大小與旋轉的半徑有關係，關係為：　
Ｆ＝向心力　ｍ＝物體質量　ｖ＝物體旋轉的速度　ｒ＝旋轉半徑
也就是說，同樣旋轉速度下，離轉軸越遠，受到的向心力就越小，向心加速度也越小。假設今天有一個半徑１公里的太空站，如果我們想讓上面的人感受到與地球相同的重力加速度，我們就必須讓太空站上的人感受到9.8 公尺／秒平方的相新加速度。
向心加速度＝V²/r　所以，9.8(想要達到的向心加速度)＝V²/1000m
解出Ｖ大約＝９９ｍ／ｓ
這樣就證明了，要讓半徑１公里這麼大的太空站擁有相當於地球的重力需要很快的轉速，所以想讓龐大的太空站上創造足夠大的重力不是簡單的事。但是，等科學更進步之後，一定有辦法能夠有效率的讓太空站旋轉，並且創造夠大的重力。

Telepathy

The person who has the ability of telepathy may become the wealthiest and the most powerful person on Earth because they  can read others' minds at will. However, he or she would also be feared because they can dig out the deepest secret from others' minds effortlessly. During the cold war, CIA founded a research called Star Gate. This research was about telepathy and its goal was to train some people, giving them the ability to perform mind control and remote viewing. CIA believed, if they could trained people to be telepaths, they could locate the military installation and submarines of Soviet Union. Unfortunately, even CIA sponsored $500,000 per year on this project, they didn't get a satisfying result, and the money of taxpayer was dumped into the water. Although we have persuaded the ability of mind reading for a long time, we still haven't reached it. So here's the question: is telepathy possible? The answer is yes.

When our brains are functioning, they transmit electrical signals. If we can catch and interpret those signals, we may be able to read people's minds. However, there are some stumbling blocks with using those signals to read mind. First, those signals are too weak, in the milliwatt range. Second, those signals are gibberish, indistinguishable from random noise. Third, we can't catch the signals from others' brain because we lack an antenna. The last, even if we can receive those signals, we can't unscramble them. But don't despair, because reading others' thoughts is still possible. In the last decades, a kind of new instrument, MRI, is introduced. This instrument can help us looking into the thinking brains. Since brain activities are related to oxygen consumption, MRI can indicates the part of brain that is activated by detecting the concentration of oxygen. The higher the concentration of oxygen, the greater the mental activity in that part of the brain. By looking carefully at the MRI pattern, scientists can briefly tell that what a person is thinking or doing. Nowadays, scientists are able to find the corresponding MRI patterns of specific words, creating a MRI pattern dictionary. It means that we are able to know what words or sentences a person is thinking by looking at his or her MRI picture of brain. If we establish a MRI dictionary in computers, computers can "translate" MRI patterns into human languages, so that we can read others' thoughts by scanning their brains. Although the current MRI devices are large and heavy, scientists are confident that handheld MRI devices can be invented one day. If the handheld MRI devices could be invented, it would be possible to scan other people's brains and know what they are thinking about. 

The mind reading machine I mentioned above is a little bit different from what telepathy has been depicted in fictions. In some fictions, the person who has real telepathic ability can read not only words but also images in others' minds. In reality, such a tasks is extremely hard to achieve because one must be able to catch all the neuron activities in others' brains. The neuron networks in our brain are complicated. Moreover, the connections may alter when dealing with a new task, making a single neuron activity observation a nearly impossible task. Even though the kind of mind reading depicted in fictions is hard to achieve, our technology may be advanced enough to address all the issues one day.    

quantum computer

The computing power of computers keeps growing fast. The number of transistors on a microprocessor double every 18-months.  Even so, the progress of the computer technology still can't satisfy the needs of science research and development of other technologies. It is hard to satisfy the demands of computing power by upgrading traditional digital computer, but there's a type of computer, quantum computer, that can increase the computing power tremendously.

Computers nowadays are basically digital computers. This type of computer computes on a binary system which uses 0s and 1s, called bits. The states of bits are either 0 or 1. Quantum computer, on the other hand, uses qubits to do calculation. Unlike bits, qubits are not limited in two states. They can exist in a superposition states. Since quibits can stay in multiple states, they give quantum computers a potential to be a million stronger than today's most powerful supercomputer.

The superposition of quibits gives quantum computers parallelism. This parallelism allows quantum computers to work on million computation at a time, while the desktop PC can only work on one. In addition to this, a phenomenon called "quantum entanglement" also makes quantum computers powerful.(this phenomenon is also used in quantum teleportation) With quantum entanglement, scientists can know the state of one quibit instantly by observing the other quibit that it is entangled with. This portrait of quantum mechanism will increase the speed of information transmitting, and end up improving the data processing.

As the improvement of technology, our demand for a more powerful computer will never disappear. If we invent a practical quantum computer successfully, there will be a big burst on scientific research  and improvement of technology. Moreover, a secret code that takes the present computers hundreds of years to break will no longer be powerful. Therefore, the first country which invents quantum computer will be able to know the deepest secrets of other countries.

瞬間傳送科技

在很多科幻片裡都看到一種機器能把人或是物體在一瞬間傳送很遠的一段距離。而在現實生活中，人類的交通工具不斷在進步，從獸力到汽車甚至進步到使用飛機運輸。飛機、汽車以及船隻的速度隨著科技進步不斷的在提升，然而，我們至今還沒發明出能在一瞬間將物體傳送到其他地方的科技。這項科技是人們夢寐以求的，如果有了這項科技，人們就不需要花時間買機票、坐飛機了。想要橫跨地球，只需要藉由一部機器，想去哪裡旅遊，只要一眨眼就到了。

根據牛頓力學，物體不會從一個地方突然消失並且出現在其他地方，物體的移動需要受到力量的推動。如果沒有任何力量推動，物體是不會移動的，就算有力量推動物體，移動過程也會是連續的。這樣看來，瞬間移動裝置是不可能被實現的。但是，從量子力學的角度來看，這項科技絕對是可行的。牛頓力學在某些情況下是不適用的，尤其是在微觀的世界裡。而量子力學可以解式牛頓頓力學無法解釋的現象，運用量子力學，我們就有可能做出瞬間傳送裝置。

量子力學裡有一個叫做"量子糾纏"的現象。這個現象就是當兩個粒子有交互作用，而兩個粒子的性質能被結合成一個整體來看。舉例來說，假設有兩個粒子是互相糾纏的，而兩個粒子有各自的旋轉方向，如果把兩個粒子的旋轉加在一起所得到的結果是沒有旋轉。也就是說，如果其中一個粒子是以順時鐘方向旋轉，那另一個粒子就會以逆時鐘方向旋轉。如果我們改變其中一個粒子的旋轉方式，那另一個粒子也會跟著變化，因為兩個粒子的旋轉總合起來要是0。知到了量子糾纏的性質後，我們可以利用這樣的性質來傳遞資訊甚至是物體。首先，假設有兩個粒子A、C，而我們想把A粒子傳到C粒子的所在位置。首先，我要找出與粒子C糾纏的粒子B，並且讓粒子A去影響粒子B，讓A粒子的資訊轉移到B粒子上，使A、B產生糾纏的現象，由於B原本是和C糾纏的，所以所有有關A粒子的資訊會轉移到C粒子上面，而C粒子就變成了A粒子。這個現象有點抽象難懂，但是稍微思考一下就能懂了。其實簡單的來說就是A粒子取代了C粒子，所以原本與B粒子在同一個位置上的A粒子被轉移到C粒子所在的位置。雖然我們已經掌握了這個原理，但是要把瞬間移動裝置時線還有很長一段路，因為光是要傳送一顆粒子就花費科學家們不少心力，更何況是要傳送有上萬個粒子的人體或是物體呢?但是，這項科技確實是有可能成真的。

星際大戰---------光劍

最新一集的星際大戰---Star Wars上映了！不知道大家看了沒有。說到星際大戰，大家一定會先想到光劍 (Light sabers)。在電影裡，光劍是一種光束刀，能輕鬆斬斷人的身體甚至是堅硬的金屬。這個武器不只外型引人注目，也同時具有強大的威力。讓人不禁好奇，在現實生活中是否也能打造出這種高科技武器呢？

要探討這項科技的可能性，我們要先了解這項武器的構造和特性。首先，光劍的刀身是一個圓柱形的光束。這個光束似乎具有很高的溫度和能量，能貫穿一切事物。在現實中，高能量的雷射確實能貫穿並且燃燒物體，但是，光束是會不斷前進的，不會像電影裡的光劍一樣，有一個光束能維持一定的長度。如果絕地武士（ｊｅｄｉ）拿著雷射光劍決鬥，你會看到兩個人揮舞著無限長的光束揮來揮去。所以，電影裡的光劍不會是用高能量雷射製成的。

雖然光劍不能用光構成劍身，但是光劍仍然是能被實現的。光劍的劍身可以用電漿構成。電漿態是物質的第四態，是一種被電離的氣體，氣體分子中的電子脫離原子核跑出來後形成。想讓物體達到電漿態，最常被使用的方法就是將氣體加到高溫，達到電漿態的氣體具有攝氏上千度的溫度，這樣的溫度的確能破壞並融化大部分的物質。但是，達到電漿態的氣體只是高溫的氣體雲，用電漿打造的劍身不會和另一把光劍的劍身碰撞，如果劍身不能相互碰撞，就不可能用這樣的光劍來打鬥了。事實上，我們能用一種特殊材料來容納這些電漿，這個材料就是＂耐高溫陶瓷＂，著種材質可以承受電漿的高溫，進而儲存電漿。接著，只要在這種耐高溫陶瓷上開數個小洞，高溫電漿就能從這些小洞被釋放出來，並且斬斷被光劍碰觸到的物體。從劍身釋放出的店將會以光和熱的形式釋放能量，所以劍身會像電影裡的光劍一樣發光。所以，電漿的確是讓光劍成真的關鍵。

然而，要產生高溫電漿，我們必須要有巨大的能量。從電影裡我們可以看出，光劍的能量來源被放在約１５－２０公分的劍柄裡。以現在來說，體積小到能被放進劍柄裡的能量來源只有一般的電池，而這些電池無法產生足夠的能量來製造電漿。但是，我們可以藉由奈米科技幫我們達到目的，現在科學家正在研究一種奈米電池，奈米電池能讓電池的體積大幅縮小並且儲存大量的能源，所以，我們將能夠做出能夠被放進光劍劍柄而且具有足夠能量產生電漿的奈米電池。在未來，這樣的電池將能帶來更多的進步。

如此一來，光劍的劍身以及能量來源都有了，由此可知，想要做出一把真的光劍不是不可能。也許在不久的將來，這樣一把威力無窮的武器能夠問世。

Can human generate electricity to kill other creature?

In some superhero movies, there are some bad guys or heroes who can use lightning to strike others. They can generate great amount of electricity, hitting their enemies from meters away. Electricity is such a great power that can stun or even kill people. It can even destroy lifeless objects. Therefore, it will be awesome if a human could carry and control that great power. However, it is doubted that if humans can really generate and control electricity.

Before we evaluate the possibility for human to generate electricity, we should ask ourselves this question: if there's any animals that can generate electricity in reality? Fortunately, the answer is yes. There's one kind of animal, the electric eel, that can generate electricity which is strong enough to kill other creatures. Electric eels have a kind of special muscle tissue, electrocytes, that can generate electricity. Those muscles generate electricity by moving ions which are positively charged into the muscle cell, creating the voltage differences between outside of cells and inside of cells. Each electrocyte generates 0.5 volt of electricity. Since there are hundreds of electrocytes in the body of electric eel, electric eels can generate up to 600 volts electricity. If we can create this kind of electricity generating muscles in human body, humans will be able to generate electricity. Moreover, humans may be able to generate more powerful electric current because humans are bigger in size and are able to carry more electrocytes. The electricity generated by a human may be two to three times greater than an electric eel can generate.

Although it is theoretically possible that humans can generate electricity, the scenes in superhero movies still seem unreal. In superhero movies, those super humans can generate lightning which is strong enough to destroy objects such as buildings. To destroy things, a great amount of energy is required, which means that only with strong electric current can electricity make destruction on objects. Nevertheless, the resistance of air is very high that high voltage of electricity is needed to generate strong electric current. In real life, there's only one thing that have such a high voltage of electricity, the lightning. The voltage of lightning is two to three hundred million volts, generating an electric current of 30000 amperes. With such a strong electric current, lightning destroy trees, do harms on buildings, and kill creatures. Notably, lightning usually strikes from the sky which is far away from the ground, but still make great destruction.(7-11 km) To generate the kind of electric that is strong enough to destroy things which located meters away, one must generate the electricity which is higher than ten thousand volts. It is nearly impossible for humans to do such a thing with electrocytes. Moreover, humans may be "electrocuted" to death by such a powerful electricity which is produced by themselves.

Although humans are unlikely to generate electricity that powerful enough to destroy buildings, creating a human who can kill creatures by generating electric currant is still possible. Maybe scientist can bring this idea into practice someday.

漂浮汽車

我們對於未來世界的交通工具一直有諸多想像，其中，漂浮汽車是我們最常想到的。因為科技的進步，汽車的數量有增無減，導致某些大城市的道路擁擠不堪，如果有一天，陸地再也容不下更多交通工具的時候，人們將會往天空發展，並且發明出能漂浮在天空中的車子。事實上，這樣的概念已經落實在我們的生活中，也就是磁浮列車。磁浮列車是利用磁力讓列車浮在空中，這項技術可以降低列車行進時受到的摩擦力，所以可以讓列車以高速行駛，也減低了能量的損耗。

既然我們有了磁浮列車，為甚麼不能用同樣的原理做出能漂浮的汽車呢?事實上，要把這項技術應用到汽車上還需要克服一些困難。首先，我們要了解漂浮的原理。磁浮列車之所以能夠漂浮是因為有足夠強的磁場，想要創造強大的磁場是很困難而且耗費成本的。想創造出夠強的磁場讓列車漂浮就要借助"超導體"。超導體是某些材料在特定條件下形成的，超導體的性質很特殊，它可以讓電流在不受到任何電阻的情況下流通。由於電阻是0，我們可以藉由這種材料產生很大的電流。如果把用超導體製成的電線繞成線圈並通以電流，就能產生磁場，電流越強，磁場也越強，所以我們可以藉由超導體來創造很大的磁場，進而讓列車漂浮。
然而，想要讓特定材料成為超導體必須要讓材料達到特定的溫度，而每種材料所需的溫度都不一樣。但是這個臨界溫度通常都很低，最一開始發現的材料要在零下100多度才能變成超導體。而現在，科學家一直在研究超導體，想辦法做出能在比較高的溫度下也能形成超導體的材料。目前，有一種材料能在 -70℃ 的溫度下變成超導體。但是，想要讓漂浮汽車變成可能，科學家必須要找出能在室溫下形成超導體的材料才行。因為想用磁浮的方式做出漂浮汽車，就需要有很大面積的超導體才行，想要冷卻面積這麼大的材料讓它形成超導體是很困難而且可行度很低的事。

以現在超導體的臨界溫度 -70℃ 來說，距離室溫超導體還有一段距離。況且，科學家們沒有完全了解超導體形成的原理，所以現在尋找超導材料的方式都是用試的。有可能碰巧就在某次試驗中發現室溫超導體，但是機率是很低的。所以，讓這項技術實現所需的時間仍然是未知的。

真的會出現吃人殭屍嗎？

食人殭屍這個主題很常見，不管是在災難電影＜惡靈古堡＞以及＜末日之戰＞，或是影集＜陰屍路＞裡都可以看到。但是，這樣的情節是否會成真呢？我們是不是真的要買幾把刀子、斧頭，準備好糧食，甚至是事先找好避難所呢？

在我們一直去擔心會不會發生這樣的事以前，讓我們來分析一下這種情節發生的可能性吧！
首先，這種殭屍主題電影的開頭一定都是從病毒爆發開始。一種新型的病毒感染生物並且讓生物變成嗜血的殭屍。而在不同的電影裡，殭屍的形式都不太一樣。但是大部分的形式都有共同點，那些殭屍都是被病毒殺死的生物，被殺死後才變成吃人殭屍。但是問題來了，病毒跟細菌不一樣，病毒只能再活宿主裡生存、繁殖，只要宿主一死，病毒就跟著死亡。所以，病毒一定要在宿主還活著的情況下才有可能繼續傳染並且寄生在新宿主體內。但是大部分電影裡演的都是活人被已經死亡的殭屍感染，這是與現有的生物學知識相違背的。除非有能夠死去的宿主體內生存的病毒，不然殭屍病毒是不會透過殭屍傳染的。

第二，一個生物死亡後是不會繼續進行新陳代謝的，所以要已經死去的生物變成殭屍並且起來活動根本是不可能的。因為肌肉的活動需要能量，而能量的來源就是要透過新陳代謝來分解養分並且產生ＡＴＰ（透過化學鍵儲存能量的物質），藉由打斷ＡＴＰ裡的磷酸鍵來產生能量讓肌肉活動。就算病毒能在死亡的宿主存活並且控制了人腦，殭屍依然需要有新陳代謝來產生活動所需的能量。

但是要說吃人殭屍完全不可能又太果斷了，因為某些病毒真的有可能影響我們的大腦，讓被感染者的精神失去正常。開始隨機的攻擊，甚至吃人。某一些殭屍電影裡的殭屍就是以這種形式存在。被感染者的身軀沒有隨時間腐爛，維持著正常狀態，也就代表著被感染著依然活著，新陳代謝也在繼續著。然而，只要超過一段時間沒進食，這些所謂的＂殭屍＂（雖然被稱為殭屍，但是被感染者依然是活著的）就會再也無法活動，而不會持續數周甚至數個月不進食還能活動。也就是說，在病毒爆發後的三周內就會有大部分的＂殭屍＂死亡。只要有一個安全的避難所可以撐上至少３個月，人類就會贏得最終的勝利！

雖然能讓人精神錯亂的病毒確實存在（例如狂犬病），但是要像電影裡一樣有吃人殭屍的出現機率實在很低。再者，能透過空氣傳染的病毒至今尚未被發現。真的要像電影裡一樣有大規模的感染實在不太可能，因為只要封鎖疫區就能有效控制疫情，連傳染力很強的流感都能被控制住了，無法透過空氣傳染的病毒又怎麼會輕易被散播呢？

我們不能果斷地說這種情節或類似的情節不會在現實中發生。但是這種事發生的機率確實很低。因此，我們不需要想太多或過分的擔心。然而，這依然是個有趣而且值得探究的話題。

讓物體結凍的超能力能否成真?(2)

在上一篇我們提到了讓冰晶聚集並形成較大冰晶體的方法。但是需要消耗的能量相當大。
那麼如果讓水的溫度降低並且結冰呢?首先，根據熱力學第二定律的Clausius theorem，熱量不會從溫度低的地方流向溫度高的地方而不造成影響。。在穩定的環境中，每個區塊的溫度幾乎是達到熱平衡了。也就是熱量不太會繼續移動，要讓某個區塊的溫度降到更低，並且讓氣態或液態水變為固態，就需要對那個區塊的氣體作功(也就是賦予能量)。否則就會違反熱力學第二定律。也就是說，Elsa必須要施予能量並且讓熱量轉移"Let heat go! "才能讓溫度降低。

以現在的製冷科技來說，熱量的轉移通常是藉由冷媒在氣態和液態之間的相位變換過程，吸收以及放出熱量。首先把氣態的冷媒經壓縮機壓縮，讓冷媒氣體變成高溫高壓(這裡的高溫是相對來說)，接著讓這個氣體進入凝結室，冷媒氣體凝結時會放出熱量(氣態轉換為液態時會放熱)，接下來讓這個低溫高壓(因為經過放熱所以變成相對的低溫)的液體進入膨脹室，在膨脹室裡液體的壓力會降低，最後讓液體進入蒸發室，冷媒也體蒸發時會吸受熱量以達到冷卻效果。藉由這樣的過程不斷循環就可以把一個空間的熱量帶往另一個空間。
想要讓溫度降到能讓水結冰就必須要功率很大的壓縮機，一般來說，冰庫製冷機的壓縮機功率是50kw-1500kw(w為瓦特，功率單位，1瓦特的功率就是每秒消耗1焦耳)
這樣的功率非常高，甚至比上一篇提到的能量消耗更高。如果Elsa想要讓大量的水結冰，就必須要更有效率的轉移熱量。  或許她可以把轉移出來的熱量轉換成其他形式的能量，並且為下次的熱量轉移提供能量。這樣或許可以提高製冰的效率，並且減少能量耗損。
以上是我用一些物理學知識所提出的分析，希望大家可以參考並且提供意見喔。

讓物體結凍的超能力能否成真?

電影"冰雪奇緣"在前陣子很流行，而裡面的女主角Elsa是個只要手一揮就能讓水氣結冰並且形成任意形狀。這讓我不禁好奇，像這樣的能力是否在真實世界也能達成呢?

首先，我們要先明白水氣結冰的原因。在電影中，Elsa身處的環境是個冰天雪地，溫度本來就很低了，所以要讓水氣結冰似乎沒有很困難。想讓水氣結冰，就要讓水的溫度降到冰點以下，讓原本是氣態或液態的水變成固態。要讓水的相位油氣態或液態轉變為固態，就得讓水釋放出熱量，將低溫度。溫度降得夠低，水就能變為固態。

但是，除了這個途徑，在某些特殊情況下依然可以讓水不放出熱量就形成固態。更正確地來說，是將原本就是固態的水聚集，讓密度、體積提高，形成較大的冰結晶體。而要利用這種途徑的條件就是在周圍正在飄雪的時候。從天空降下來的水是一個個細小的冰結晶，降到地面堆疊起來時就會形成蓬鬆的雪堆。因為這些結晶體裡的水分子不會與鄰近晶體的水分子形成鍵結，而是推疊在一起，如此一來，這些結晶就不會進一步形成體積更大，結構穩定的固體。水分子間是透過"氫鍵"來鍵結的，氫鍵就是讓兩個以上的水分子互相連結的化學鍵。想要打破氫鍵就必須有足夠的能量，而打破鍵結時會釋放出能量。反之，如果要重新形成鍵結也要賦予能量。想利用周遭的冰晶形成更大的冰結晶體，就必須要賦予能量讓這些微小的冰結晶體間形成鍵結。氫鍵的鍵結能大約是 5-30kJ/mol (J是焦耳，能量的單位，mol 是莫耳數，1 mol的原子 大約等於有6*10^{23  個原子})    1mole的水分子質量大約為18g

假設今天要做出18g的冰晶體，那需要的最低能量就是5000J (5kJ) 。 但是，環境中的冰晶已經是由一定數量的水分子結合成的，在-12度C下形成的冰晶質量約為12 𝝻g，也就是含有約1.5*10^{9 個水分子。所以需要的能量就是5000*(}6*10^{23  -} 1.5*10^{9  /}6*10²³)  (已經有1.5*10^{9 個水分子鍵結，所以我們要扣除這些已經鍵結的水分子，重新計算能量消耗})  由於1.5*10^{9  相對於}6*10^{23 來說很小，所以我們可以省略不計，並且估計所需能量還是5000J。}

也就是說，光是要做出18g的冰晶體就要花費5000J的能量，在電影裡，Elsa做出的冰肯定有超過數十甚至數百公斤，也就花費了數萬甚至數十萬焦耳的能量。要一個人輸出這麼多能量是不太可能的。就算一直吃香蕉補充能量也行不通。

隱形

隱形的技術不管在科幻電影或者是知名魔幻電影"哈利波特"都有提到。科幻電影常常有讓太空船隱形的科技，哈利波特則擁有隱形斗篷。 事實上，這項技術離我們已經不遠了。

在了解隱形前先來看看"透明"這個概念。透明的材料有一種特性，就是透明物體的晶體結構往往是排列整齊並且具有一定模式的。如果晶體結構是呈現整齊的直線排列並且在晶體間有空隙讓光通過，那這種材料就會是透明的(因為光可以穿透)。但是，有些分子呈現隨機排列的材料也可以是透明的，例如玻璃。玻璃透過特殊的工業加工可以讓分子的排列方式呈現光可以穿透的狀態，進而成為透明材料。

有些科學家實驗後發現，有一種叫做"超材料"的特殊材料在特定的分子結構下可以讓光波彎曲並且從這種材料的周圍繞過。要知道，我們能看到物體是因為光的反射。如果某樣物體完全不會反射光線的話，我們就"看不到"這個物體的存在。  (如下圖)

"超材料"(meta materiel) 是一種混和不同種金屬的人工材料，這種材料在特定的結構下能改變電磁波的路徑(光就是一種電磁波)。這樣的特性讓隱形成為可能。但是，科學家仍然要克服一些技術上的限制才能讓隱形的產品問世。首先，如果想用這些材料操縱電磁波路徑，這些材料的大小和分子間的空隙要比電磁波的波長還小。一開始，科學家能彎曲波長較長的電磁波，但是，可見光的波長大約在390-700奈米之間。而想要讓物體隱形，必須要讓分子和分子間距離小於390奈米，才能讓所有可見光的路徑能被彎曲，進而達到隱形。所以，科學家把用來製作半導的技術應用到隱形科技，因為半導體能越縮越小都是仰賴一種蝕刻技術。利用這種技術，就能把超材料越做越小。現在，科學家已經能把波長約700奈米的光(紅光)彎曲。相信在科學的進步下，遲早能彎曲390奈米以下的光。

Physics of impossible------力場2

之前提到的四種作用力都無法創造出完美的力場，那我們就真的束手無策了嗎?事實上，現在的科技提供了一些可能的選項
1.Plasma window(Plasma即電漿):電漿是被離子化(電子從原子裡逃脫)的氣體，想創造出電漿，可以將氣體加熱到非常高的溫度或是用很強的電場或磁場把電子從原子核引出來。想做出Plasma window 必須要用磁場控制電漿，讓電漿把外界隔絕形成腔室。此時電漿會防止外界的氣體進入，讓我們能在上內創造真空。同時也可以反過來，在外太空時可以防止腔室內的氣體外流，與太空的真空隔絕。如果讓溫度很高的電漿形成一個遮罩，任何外來物碰觸到高溫電漿時就有可能被氣化從而達到抵禦的效果。但是要創造能排斥物體的力場，就需要別的東西了。

2.Laser curtain:與Plasma window 相同的概念，我們也可以用高能量的雷射形成一個遮罩，讓外來物被破壞甚至氣化。同時使用這兩種技術更可以增加氣化外來物的機率。

3. 奈米碳管:奈米碳管是由碳原子鍵結後構成構成的管狀結構。硬度是鋼鐵的好幾倍但是重量很輕。如果在Plasma window 和Laser curtain 後面再加一層奈米碳管構成的屏幕。未能被前兩層氣化的物體也有可能被奈米碳管擋下。

4.光致變色:雖然有上述三種技術就可以抵擋大部分的物體侵入，但是，還是無法抵擋雷射光的入侵。想要抵擋雷射光，就必須要有光致變色的技術。光致變色就是當一種特殊材料照射到紫外光時會產生化學變化改變性質，並且吸收特定波長的光。常見的應用是變色鏡片，當鏡片照到紫外光實惠該便性質並且吸收可見光，因此鏡片會變黑。如果使用這種技術，就有可能在雷射造成傷害前把它吸收掉。

結合以上幾種技術就可以創造出很強的防禦技術，這是目前的科技很有可能達成的事。但是要創造出能排斥任何雷射或是物體的完美力場，只有在我們發現第五種力的時候。而目前這方面沒有很大的進展或重大發現。想要看到像電影"失落的帝國"那樣的力場，可能還很遙遠了。

Physics of impossible--------力場

在很多科幻的情節裡，都有一種能夠抵禦任何外來物的力場，任何武器都無法穿透，只有切斷能量來源才能成功侵入。有人認為這是只有科幻片才有的情節，也有人認為這種力場被發明只是時間問題。

以目前我們對物理的認識以及現今的科技而言，這種力場是不可能存在的。因為目前沒有任何物質或是力場能達到這樣的效果。目前我們所知的有四種力-----重力、電磁力、強作用力以及弱作用力。
1.重力:重力是我們能站在地表上的原因，是一種吸引力。然而，我們想要的立場是能排斥外來物的，所以重力很明顯的不是我們要的答案。況且，重力在很遠的距離下依然會產生作用，我們要的力場是只在物體靠近時才發揮作用。
2.電磁力: 電磁力有吸引與排斥兩種，是一種在電場和磁場中可以感受到的作用力。既然電磁力可以產生排斥力，我們是否能用它來做出科幻電影裡的力場呢?事實上，只有帶有靜電荷的物質才能被電磁力影響。舉例來說，如果你把一塊塑膠丟進電磁場裡，它是完全不會被力場影響的。(塑膠是絕緣體，在沒有靜電的情況下是不會受電磁力影響的)所以，電磁力並不能抵禦所有的物體。
3.強、弱交互作用力:要清楚的解釋這兩種力需要花一些篇幅，所以我就不多做說明。弱交互作用是在原子衰變時可以觀察到，而原子衰變就是由較重的粒子轉變成較輕粒子的過程。強作用力則是一種能讓原子核裡的粒子穩定，不因為排斥力而分散的力。這兩種力的作用範圍都很小，只有原子的尺度。強作用力的作用範圍約10^{-15 m ，強作用力更小。所以這兩種力也無法創造我們要的那種力場。(我們要的力場是能在物體靠近數公分時發生排斥力)}