Mei 到處 8

Guano 海鳥屎–War of the Pacific太平洋戰爭

noreply@blogger.com (Wechner) — Sat, 09 Jan 2016 15:39:00 +0000

昨晚睇咗一套非常好的紀錄片Chris Tarrant Extreme Railway Journeys Series 2 Crossing the Andes 安地斯山脈.

在影片開頭, Chris 介紹了他要去睇 Nitrates Mine, 在19世紀Nitrates又叫white gold, 非常值錢是用來製造 gun powder 的 guano (海鳥屎含豐富的硝酸鹽).

guano: The word "guano" originates from the Andean indigenous language Quechua, which refers to any form of dung used as an agricultural fertilizer.
就是裡d 海鳥屎引起了War of Pacific,
https://en.wikipedia.org/wiki/War_of_the_Pacific
自1883年後, 玻利維亞失去出海口，成為內陸國.

我知道雀屎都有用的時候, 是我睇咗 Nauru: An Island Country Destroyed by Phosphate Mining:
http://www.amusingplanet.com/2015/06/nauru-island-country-destroyed-by.html
不過, 佢地叫雀屎為phosphate, 唔係guano.

The atmosphere of Earth

noreply@blogger.com (Wechner) — Sun, 03 Jan 2016 03:55:00 +0000

Scientists think that the climate on Mars 3.5 billion years ago was similar to that of early Earth.

So, if you don’t know the history of Earth, you will not understand why Mars has lost its atmosphere as it looks like, right now!

https://youtu.be/mDBQk5tOVlU ( time start from 10:00) Mr Sui, in this video says:

“Mars lost its atmosphere, because the iron on mars is only on it’s surface, not in the core of the planet, that causes the loss of its magnetic field, and the solar wind is so strong that it blew the atmosphere away.”;

“Iron could not condense because there was not enough heat to penetrate into the centrosphere of Mars”;

“because Mars is not like earth, which is full of solid iron in the centrosphere, it does not have a magnetic field, so it could not retained the atmosphere, and let the solar winds blow it away.”…..!!!

As what I write on my blog before : “Why is Mars Red?” ; “How did the core of Mars form?”; “Why did Mars’s core cool down.” all these articles are telling you the same thing, in our solar system, all the rocky planets were formed in the same way and what Mr Sui says is wrong!

Let’s have a look, how the atmosphere of the early Earth was formed:

The Early Atmosphere:

The first atmosphere 4.55 billion years ago:

When the Earth first formed, the solar system was a violent place. Giant hunks of rock, metal and ice slammed into the Earth's surface. As material collided and fused, there is intense heat and pressure. Matter vaporized on impact leaving puddles of magma. Many of the collisions released water vapour and other gases, which gradually formed a blanket of steam around the early Earth. This thickened over time becoming the first atmosphere. Some of the lighter gases like hydrogen leaked into space, but the denser steam collected and had a greenhouse effect insulating, heating and melting the surface of the planet.

(Mei : Thus, Mars would also have an atmosphere, during the violent, early period of the forming of our solar system)

The Oceans and the Moon 4.53 to 4.5 billion years ago:

Over time, the Earth, in a process called differentiation, separated into layers and it's crust cooled. Steam in the atmosphere condensed and formed the oceans, covering much of the planet in chemical-rich waters.

The young Earth settled down, but then something about the size of Mars is thought to have slammed into the planet, causing immense changes. The two bodies coalesced and material was blasted outward. Debris from the impact formed a ring of matter that orbited the Earth and eventually became the moon. The surface of the Earth became molten again from the intense heat, and the oceans reformed as a steam atmosphere.

When things finally cooled down again, the Earth's crust hardened and steam settled back down to reform the oceans again. The moon stabilized the Earth's tilt and helped to regulate the climate.

(Mei: We know, from the debris left over from the collision with the other planet, that the moon was formed from earth material because all the material we found in our moon is exactly the same as the material of the earth’s crust! Our moon is round because it is large enough that gravity shaped it spherically, whereas the two moons of Mars have an irregular shape because they are too small that gravity could force them into a spherical shape and we do not know how the Mars moons have formed.)

The Hadean Eon 冥古宙 4.5 to 3.8 billion years ago:

This part of Earth's history is uncertain because there is no surviving sedimentary rock to offer clues about the environment. There may have been several large asteroid or comet impacts, but none as big as the one that formed the moon. Molten rock or magma oozed in some places and blasted out in others. Volcanic activity released heavier gases like carbon dioxide and methane. There was still very little oxygen in the atmosphere.

The Archean Eon 太古宙 3.8 to 2.5 billion years ago:

The oldest sedimentary rocks found in Greenland tell us a lot about the Earth at that time. There were oceans, lands, rivers, and beaches. Deep in the ocean, chemical-rich hydrothermal venting may have contributed to the first forms of life on Earth. These first microbial organisms are thought to have eventually spread throughout the Earth's oceans. Some microbes consumed hydrogen gas and others produced methane as a waste product. Biology began to affect the atmosphere.

By about 3.5 billion years ago, stromatolites mounds made by microbes-- populated the world's beaches. Some early microbes used the sun's energy for photosynthesis, but the first photosynthesizers didn't release oxygen. However, by 2.8 billion years ago, life forms evolved that could use sunlight to split water molecules and release oxygen as a waste product. These were the cyanobacteria that still prosper in today's oceans.

Most of the new oxygen combined with organic carbon to recreate carbon dioxide molecules, and some was used up by other chemical reactions. But eventually, oxygen flooded the atmosphere and touched off a mass of ecological disaster from many of the anaerobic life forms that were poisoned by the abundance of oxygen.

Other life forms adapted to thrive in the new conditions. The rock record offers proof. Oxidized iron compounds are reddish and rust colored. In certain layers of sedimentary rock, they demonstrate the predominance of oxygen after 2.4 billion years ago.

At this time, oxygen formed the ozone layer about 20 to 30 kilometres above the ground, protecting life on the Earth's surface from the sun's harmful ultraviolet rays.

https://en.wikipedia.org/wiki/Cuatro_Ci%C3%A9negas

Snowball earths雪球地球 2.4 billion years ago to 2.2 billion years ago :

The rise of oxygen was coupled with the reduction in greenhouse gases like methane and carbon dioxide, so the Earth retained less of the sun's heat, and the global climate became significantly colder. There was mass glaciation and the Earth was encased in ice, often called a snowball Earth. The icy shell reflected sunlight, making it colder and colder, but volcanoes punched through the ice and volcanic carbon dioxide gradually built up in the atmosphere. When the greenhouse effect became strong enough, the planet warmed and the ice melted.

Scientists think that there were three snowball Earth cycles over a period of time from 2.4 to 2.2 billion years ago, and then a period of about one billion years in which the atmosphere and climate were fairly stable.

More recently, the planet experienced other snowball Earth events, but some life forms were able to survive the cold.

The Phanerozoic Eon Begins 542 million years ago:

The current eon, the Phanerozoic, brought a proliferation of plant and animal life. Vascular plants with tissues for conducting water and nutrients colonized the land about 400 million years ago and their photosynthesis caused oxygen levels in the atmosphere to rise.

By about 300 million years ago, extensive forest covered the Earth. They pushed the oxygen levels higher and enabled an even greater diversity of life. Biology, geology, astronomical events and periodic changes in the Earth's position in orbit influenced the climate, but overall, the atmosphere remained stable enough for life to persist.

(Mei: Scientists believe that as the earth’s core is cooling down over time, our planets atmosphere could be similar to that of Mars eventually.)

https://youtu.be/HBabZyJTFTA

Next, we will look at hypotheses that could have caused the loss of the heavy atmosphere on Mars. To be continued……

For your information:

https://en.wikipedia.org/wiki/History_of_Earth

Why did Mars’s core cool down

noreply@blogger.com (Wechner) — Tue, 17 Nov 2015 14:59:00 +0000

The reasons are:

1. After the Big bang, the energy burnt out, the whole universe cooled down gradually : The truth is, not only Mars was cooling down, even our Earth is cooling down too.

ref: no. 1

2. Obviously , Mars is further away from the Sun, and also it is a lot smaller than the Earth, that is why it is cooling down more quickly.

3. Mars has a lot less green house gas .

ref: no. 2

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ref: no. 1

The cosmic background radiation is radiation left over from early development of the universe, and is a landmark proof of the Big Bang theory. Before the formation of stars and planets, the Universe was smaller, much hotter, and filled with a uniform glow from its white-hot fog of hydrogen plasma. As the universe expanded, both the plasma and the radiation filling it grew cooler. When the universe cooled and stable atoms could form, they eventually could no longer absorb the thermal radiation and the universe became transparent instead of being an opaque fog. The photons that from that time have been propagating ever since, growing fainter and less energetic. The CMBR has a thermal black body spectrum at a temperature of 2.725 K, so it peaks in the microwave range frequency of 160.2 Ghz(1.9 mm wavelength).

http://www.universetoday.com/79777/cosmic-background-radiation/

https://nightsky.jpl.nasa.gov/news-display.cfm?News_ID=631

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ref: no. 2

scientists believe, Mars must have lost its most precious asset: its thick atmosphere of carbon dioxide. CO₂ in Mars's atmosphere is a greenhouse gas, just as it is in our own atmosphere. A thick blanket of CO₂ and other greenhouse gases would have provided the warmer temperatures and greater atmospheric pressure required to keep liquid water from freezing solid or boiling away.

http://science.nasa.gov/science-news/science-at-nasa/2009/06nov_maven/

How did the core of Mars form?

noreply@blogger.com (Wechner) — Thu, 12 Nov 2015 11:11:00 +0000

To understand how the core of Mars has formed, we need to look at how the whole solar system did come to be, the inner, rocky planets like Earth and Mars and the outer, gas giants like Jupiter and Saturn. The picture below does show the whole history of the formation of our galaxy the Milky Way and our solar system.

Here is a picture zoomed in at our solar system as it is now.

And here is the theory of how our planets have formed:

https://youtu.be/0zAAIYMDsTo

Our solar system, consists of:

The inner, the Rocky, or Terrestrial planets : Mercury, Venus, Earth and Mars.

The outer planets, the Gassy Giants: Jupiter, Saturn, Uranus and Neptune.

How the rocky planets formed:

1. The material that formed our solar system originates probably from a supernova explosion somewhere in our Milky Way. It formed a cloud that collapsed due to gravity and started to spin and as it spun it slowly flattened out to form a disk. Astronomers call such a disk a protoplanetary disk or short a proplyd, and as it collapsed it got hotter and hotter until fusion occurred and our sun was born. About 99.9% of all the material in the proplyd went into the sun, the 0.1% of the proplyd’s leftovers formed the rest of the solar system, the planets and planetoids.

2. The intense heat of the young sun drove away gassy materials (a lot of hydrogen and helium) from the inner parts of the solar system. Making this region deprived of hydrogen and helium and formed the outer planets, the gassy planets Jupiter, Saturn, Uranus and Neptune. These gas giants contain 99% of the leftover material, so what we're left with is a tiny residue of a tiny residue to form the inner rocky planets, including our Earth.

3. Closer to the sun, from that tiny residue of a residue, you find material orbiting, orbiting in the inner orbits, and that material is less gassy. There's more sort of solid stuff. You have little dust motes that eventually will gather together through electrostatic forces or collisions to form little rocks. You have particles of ice that will eventually form snowball-like objects, and eventually they form things like meteorites or asteroids, and they're getting bigger and bigger and bigger and they're colliding with each other. And in each orbit, you eventually get large objects that finally sweep up through their gravitational pull, everything else that's in the orbit. And so, eventually, over a hundred million years, in each orbit you have a rocky planet. Now, this process is called accretion.

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Since the four rocky planets were created with the same process there structure is very similar and varies only due to their different sizes , their distance from the sun and the time lapsed since their creation.

Very little is known about the core of Mars, but we can project the probability of the structure of its core from the knowledge we have gained about the Earth’s core.

https://youtu.be/ZzcXGqrvxJc

The early earth was extremely hot for a number of reasons :

1. Radioactivity: The supernova that blew up just before the solar system was formed created a huge amount of radioactive material, the radioactivity generated a lot of the heat.

2. Accretion: The violent collisions of materials like meteorites and asteroids in the early Earth created huge amounts of heat.

3. Pressure: As the clouds of dust from the supernova became denser and denser due to gravity, an enormous amount of heat was generated particularly at the centre where the highest pressure occurred.

In fact, the early Earth did get so hot that it melted, and that is really important. Because if it hadn't melted, today's Earth would be very different from the way it is. To get a sense of what happened and why this was so important, let's imagine a kind of absurd cooking experiment.

Put some stuff in a sauce pan. You're going to put in some coins. You're going to put in some rice. You're going to put in some plastic. Let's add a bit of mud.

Let's put in some ice and you can chuck in one or two other things. And now, we're going to heat that stuff up to several thousand degrees. Don't stir, just let it simmer.

Finally, what we'll see is that the whole thing is going to melt. The heavy stuff, such as the coins, are going to sink down to the bottom, lighter stuff is going to rise to the top, and some stuff is going to evaporate and boil above the sauce pan.

Now something very like this seems to have happened to the early Earth. It melted and because it melted, it formed a series of layers and they give it the structure we have today. Let's look at the four main layers.

1. The Inner and the Outer Core : The first is at the centre and is mainly iron and nickel because they are heavier than most other materials and therefore sank to the centre of the Earth. And the fact that the centre of the Earth is full of magnetic metals (iron and nickel) is really important because this gave the Earth its magnetic field, and the magnetic field deflects some of the sun's rays that would be harmful to living creatures such as us. So that's the first layer, the core.

2. The Mantle : The lighter stuff-- lighter rocks-- float above the core and form a layer that's called a mantle. Now, the mantle you can think of as a sort of hot sludge of rocks. These rocks are so hot they're sort of semi-molten and they're actually moving around in convection currents inside the mantle.

3. The Crust : At the very top, we have a layer called the crust. Very light rocks such as basalts and granites stayed on the top, they cooled down and formed a thin solid layer, the crust. That's where we live. The crust is pushed around by the convection currents from underneath. You can think of the crust as a tiny, thin layer a bit like a sort of egg shell.

4. The Atmosphere : Finally, the fourth layer, the atmosphere. Some of the gassy stuff bubbles up to the top, it evaporates. The very light gases such as hydrogen disperse into space, but a lot of other gases like Nitrogen and Oxygen, just hang around the Earth held by its gravitational pull.

And that's how the Earth acquired the structure it has today. All of this happened about ten million years after the creation of our solar system.

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https://youtu.be/XNkArWUT8pA

A new animation by NASA scientists illustrates what Mars – the fourth planet from the Sun and the second smallest planet in the Solar System – may have looked like billions of years ago.

Billions of years ago when the Red Planet was young, it appears to have had a thick atmosphere that was warm enough to support oceans of liquid water - a critical ingredient for life. The animation shows how the surface of Mars might have appeared during this ancient clement period, beginning with a flyover of a Martian lake. The artist's concept is based on evidence that Mars was once very different. Rapidly moving clouds suggest the passage of time, and the shift from a warm and wet to a cold and dry climate is shown as the animation progresses. The lakes dry up, while the atmosphere gradually transitions from earth-like, blue skies to the dusty pink and tan hues seen on Mars today.

Today, Mars is a cold, desert world. Liquid water cannot exist pervasively on its surface due to the low atmospheric pressure and surface temperature, although there is evidence for spurts of liquid flow that perhaps consist of a briny solution with reduced freezing temperature. Water under current conditions can be ice or sublimate directly into vapour without staying in a liquid phase.

Now a day, scientists are not yet certain if the core of Mars is solid, liquid, or in two distinct sublayers, like Earth. Future measurements will tell us more.

http://mars.nasa.gov/allaboutmars/facts/

Why is Mars Red?火星點解是紅色?

noreply@blogger.com (Wechner) — Wed, 04 Nov 2015 12:03:00 +0000

We learn from our science class during our secondary school that Mars is a red planet, and it is red, because it is full of rusty iron on the surface of the planet.

I just watch the follow video, and found it very interesting:

https://youtu.be/7koIlNPay-s

The iron got rusty because of the rain/water and the oxygen in the air, causing the iron oxidized.

But if you look closely at the surface of Mars, you’ll see that it can actually be many different colours. Some regions appear bright orange, whilst others look more brown or even black. But if you average everything out, you get Mars’ familiar red colour.

What I am most curios about Mars is:

If I could stand on the surface of Mars and look around, is

1.the sky on Mars red too?

(The dust in the atmosphere scatters the red photons, makes the sky appear red. We have something similar when there’s pollution or smoke in the air.)

2. the sunsets blue?

(The dust absorbs and deflects the red light, so you see more of the blue photons streaming from the Sun.)

https://youtu.be/tc2ctrrLHso

Further…………so, Mars is further away from the sun than the earth, I wonder how bright is daylight on Mars?

ANSWER from Jim Murphy on July 18, 1997:
The brightness of the sun on Mars, were there to be a clear day, is about
half the brightness of a similar day here on Earth.  I arrive at the value
of one-half simply by knowing that the brightness of an object decreases by
the square of the distance, and since mars is on average 1.5 times as far
from the Sun as earth, 1.5 times 1.5 is 2.25, and 1 divided by 2.25 is 0.44,
or 44 percent as bright.

Now, just because the apparent brightness is half, that does not necessarily
mean that the scene will be half as bright on Mars.  Mars' less massive
atmosphere will mean less scattering of light, and thus the clear martian
sky would not be as blue as here on earth, and all the scattered light which
we see here on Earth, which makes the sun appear a bit less of a flashlight
beam than it is would all conspire to make the Martian sky appear darker.

http://quest.arc.nasa.gov/mars/ask/atmosphere/Brightness_of_daylight_on_Mars.txt

Time Travel and it’s myths

noreply@blogger.com (Wechner) — Sat, 23 May 2015 06:42:00 +0000

From the BBC TV programme “Doctor Who” to the recently released movie “Interstellar” we are inclined to believe that time travel is actually possible. I was so intrigued to find out, that I studied the subject myself and here are my conclusions:

Michelson and Morley with their experiment in 1887 in Cleveland Ohio have started the possibility of time travel.

http://en.wikipedia.org/wiki/Michelson–Morley_experiment

The experiment established conclusively that the speed of light is independent of the speed of it's source. While, at first glance, this might not appear to be very significant, it has opened a new chapter in Physics with paradoxes that the human brain has trouble dealing with, it is beyond what we call logical.

In the following graph I try to demonstrate the dilemma. A bicycle rider, a stationary person and a sprinter all have a torch and a light receiver in their hand. They switch on their torches exactly at the same time at the blue starting line. The light will then travel towards a mirror where it is reflected and arrives back at the light receiver each persons holds in their hand. We can clearly see that as a result of the movement of the bicycle rider and the sprinter, their light beam will have to travel a much shorter distance than the light beam of the stationary person. The time, delta t, required for the light beam to travel the varying distances shown on the graph is the distance divided by the speed of light. Since the speed of light is constant, independent of the speed of it’s source, it is very obvious that only the time can change. That means if all three of them do wear a watch, they will all show a difference in time! This does not sound right, but it is!

The Dutch physicist Hendrik Lorentz was one of the first to define what we call now “Time Dilation” with which we can calculate the time difference between objects that move relative to each other, with the “Lorentz Factor”(Gamma). Albert Einstein went further with his analyses and included mass in his equations which consequently resulted in the release of his “Special Theory of Relativity” in the same year 1905. http://en.wikipedia.org/wiki/Hendrik_Lorentz

●○「以英文為準, 中文翻譯只作參考」○●

從BBC電視劇“超時空博士”到最近發佈的電影“星際啟示錄”使到大家都傾向於認為時間旅行是實際可能的。我也因而很感好奇, 想找出答案來，於是我對這個課題作出了研究, 以下是我的結論：

於1887年, 在俄亥俄州的克里夫蘭, 邁克生和莫立就做了他們的實驗, 來實驗時間旅行的可能性。

http://en.wikipedia.org/wiki/Michelson–Morley_experiment

實驗確證了光速不單是一常數(光速是一常數, 早於此實驗前已被驗証了),並且, 並不依賴於光源的運動(即與光源運動無關)。當，乍看之下，這可能並不顯現出很重大意義，可是它卻揭開了物理學新的一篇並且是看似是對, 卻又互相矛盾的現象, 使得人的大腦出現處理障礙，這是超出了我們所說的邏輯。

在上圖中我嘗試指出這種窘境。

一個騎脚踏車的人，一個站牢的警員，一個短跑運動員等, 他們每個人都手拿有一個手電筒和一個光接收器。在藍色的起跑線上, 他們同一時間打開他們的手電筒。手電筒的光束也就立即射向前方的鏡子, 並且立即直線反射到每個人手持的光接收器之上。我們可以清楚地先看到，騎腳踏車的人和短跑運動員的結果，他倆反射的光束比起站牢的警員的距離是更短的。

時間，delta t (時間差,即由源點至終點的差別):

要計算上圖各人光接收器的時差就是距離除以光速(delta t = 距離 / 光速) 。可是由於光的速度是恆定的，並且是與光源運動無關, 這很明顯地，只有時間可以改變。這意味著，如果他們三個人都戴著同樣準確的手錶來計算, 由光源至光接收器接收到的時間, 他們將發現大家的手錶上的時間是一致(舉例, 如果騎腳踏車者的手錶顯示收到光反射來的光速是10秒, 其它兩人也會說, 他們的錶也是顯示出10秒)！這聽起來很不正確吧(因為我們明明就看到在上圖, 騎腳踏車者應該是最快接收到光的人!), ，但這卻是如此的發生著！

要去解釋點解明明就是騎腳踏車者收到光先, 卻手錶上顯示出同其它兩人接收到光速的時間是一樣的, 唯一理由就只有他手錶是行得比其它兩人的要慢! 也就是, 當移動更快者, 他的時間相對於他人走得為慢!..........換句話來說, 唔郁的警察( 不動的警察) 也就是光反射路程最長的, 可是他的時間就要比其它兩人走得快了。

荷蘭物理學家亨德里克·勞侖茲是第一個定義出現在我們稱為“時間膨脹”，由他的“勞侖茲因子”使我們可以計算出由物體彼此相對移動的時間差異。 1905年, 愛因斯坦更進一步分析，並將質量加入在他的方程，因而導致了他的“狹義相對論”於同年發佈.

Time Dilation 時間膨脹:

In this picture we see a girl watching a light beam that travels from the source, on the bottom of a spacecraft, vertically up to a mirror on top of the spacecraft, at the distance D, and back down to a receiver on the bottom of the spacecraft.

If the spacecraft does not move as shown on the left, the time required, (delta t'), for the light to travel from the source to the mirror and back is clearly,

在這張圖，我們看到一個女孩觀看宇宙飛船上的光束從底部源頭垂直向上遊走至頂部上的反射鏡, 其距離為D，並回落到底部的接收器上。

如果如左邊所示的不移動的宇宙船，所需要的時間為（△T'），該光從光源到反射鏡再加回射回歸底部的接收器上, 顯然:

where D is the distance between the source and the mirror, and c is the speed of light.

If, however, the spacecraft is moving at a speed v, the light will have to travel much further because the mirror and the receiver are moving away from the light source. This is causing the whole paradox, because we know that the speed of light is constant, independent of the movement of it's source, but the distance it has to travel has significantly increased. So if the speed of the light is fixed and the distance is fixed, then only time can change as a result of it.

It is straight forward to calculate the time lapsed on the spacecraft for the light to travel from the source to the receiver. We draw the right angled triangle between the source and the mirror. The vertical cathetus is D, the horizontal cathetus is half the distance the spacecraft has travelled while the light travels from the source to the mirror, with v the speed of the spacecraft and delta t the time lapsed for the light to travel between the source and the receiver. The hypotenuse is the distance the light has travelled between the source and the mirror, at the same time, with c the speed of light.

其中，D是光源和反射鏡之間的距離，以及 c 是光速。

然而，如果宇宙飛船以v速度移動，光就必須比之前(宇宙飛船不動時)向前射前更多了，因為反射鏡和接收器都因宇宙飛船的移動而從光源移離更多。這是造成整個悖論，因為我們知道，光的速度是恆定的，與光源運動無關，但它卻因宇宙飛船的移動做成距離的(比前宇宙飛船不動時)顯著增加。所以，如果光的速度是固定的，該距離是固定的，那麼就只有時間可以改變，這就必然是其結果。

要明確計算當飛船移動後, 光束從底部源頭至頂部上的反射鏡, 再回落到底部的接收器上的時間差。我們繪製光源和反射鏡之間的直角三角形(即上圖左面的飛船飛行時, 光速與飛船移動所成距離的關系) 。垂直直角邊為D，水平線去到直角那一邊是宇宙飛船前行時光從光源到反射鏡再反射回到接收鏡, 整段距離的一半。用v為飛船的速度, 和delta t 為由光源發射去到接收器的時間差距。斜邊是光在光源頭和反射鏡之間距離, 同時, c是光速。

(簡單地說: v = 飛船航行速度

c = 光的速度

delta t = 由光源發射去到接收器的時間差距)

With the theory of Pythagoras we can now resolve the equation for delta t and get the following result. (It is a simple algebraic problem, I had not trouble resolving it)

由畢達哥拉斯的理論，我們現在可以解開三角方程式，找出delta t , 並得出以下結果。（這是一個簡單的代數問題，所以很容易就計算到答案了. 計算過程列於本頁尾. ）

If we substitute 2D/c with delta t' as we have defined it earlier, we get the time difference between a clock located on earth and a clock located in the moving spacecraft.

如果我們以2D / C 來替換 deltat t' 就如我們在之前已經做好的定義 ( )，我們會得到了一個位於地上地球時鐘和一個位於移動飛船上的時鐘之間的時間差。

Gamma (), referred to as the “Lorentz Factor”, is shown on the above graph as a function of v. As you can see on the graph, it does change very little between v = 0 and v = c/2, which is important to consider when we look at the potential of time travel with current space travel technologies. Gamma only increases significantly as the speed of the space craft approaches the speed of light. If the spacecraft reaches the speed of light then the time on the spacecraft stands still.

The twin paradox is commonly used to demonstrate the theoretical possibility of time travel, one twin enters a spacecraft and travels for 20 years at the speed of light while the other twin stays on earth. When the travelling twin returns after twenty years he has not grown older since he left earth, because time did stand still on the spacecraft, so he travelled forward in time when he meets his now twenty year older twin back on earth. Or the twin that stayed on earth has travelled back in time if he enters the spacecraft after it returns and meets his twenty year younger twin.

伽馬()，簡稱為“勞侖茲因子”(也即是我們之前計算所得, ) 我們用圖來演示出出當v函數(飛船加速)的增加時, 它對所做成的變化。正如可以在圖中看到，從v= 0 和 v = C / 2之間, 改變是極為之少。直至去到差不多90%左右的接近c, 突然急速增加, 並且愈接近c時, 即當飛船時速達至光速, 會是無限. 也就是說, 飛船如果達到光的速度時, 那麼飛船上時間會靜止不動。然而在v= 0 和 v = C / 2之間, 改變是極為之少。也即是說我們人類目前太空旅行技術來說, 我們宇宙飛船仍然是 v= 0 和 v = C / 2之間的早期, 還有好一大段的距離先可看到明顯的轉變, 先可同光時速一樣快。

孿生子悖論通常用來證明時間旅行理論的可能性，雙胞胎中的一個 (就當他是哥哥好了)進入飛船(就當他入飛船時是2000年好了) 以光的速度旅行了20年，而他的雙胞胎的弟弟(就叫他弟弟好了) 則留在地球上。可是當哥哥一踏入船艙飛行那一刻, 因為他以光速飛行, 他在船上的時鐘就開始靜止不動了, 當在20年後他回到地球(即2020年), 一踏出船艙, 他並沒有老了20年, 可是他見到的弟弟已經老了20年了。因為是他在船上時間是靜止了, 所以哥哥可以停留在2000年, 回到地球卻已經是2020年, 他向前旅走20年, 再遇到老了20年弟弟, 可是弟弟一踏入船艙見到了年輕的哥哥, 他的時間就好像時光倒流回到20年前那個年輕的哥哥!

While time travel is theoretically possible, I will now have a look at the time travel we can achieve with our current technologies.

The fastest spacecraft that we have ever built is Voyager 1 which is just leaving our solar system and is travelling right now at 61,380 km/h through outer space. The speed of light is approximately 1,080,000,000 km/h.

Voyager 1 is an unmanned spacecraft, much easier to accelerate than a manned spacecraft that would need to be much heavier to take all the amenities for a person to survive on board. So lets assume that we would be able to build a spacecraft that can take a person on board with supplies for a one year trip and travel at the extraordinary speed of 100,000 km/h, how much younger would the traveller be after a one year trip (assuming we don't need much time to accelerate and slow down the spacecraft)

Using the above formula, gamma would be 1.0000000043 for this speed. One year with 365 days and 24 hours per day and 3600 seconds per hour has 31,536,000 seconds. If we multiply that by gamma and deduct one year we find that the space traveller would be only 0.14 seconds younger than his twin who stayed on earth.

So the reality is that time travel is not within the scope of our current technologies, and all the speculation about worm holes, gravity walls ect, is just pure science fiction. The “Tardis” of course is quite different, it does work, because that was developed by time lords not by humans.

既然時間旅行在理論上是可能的，現在我們可以用我們目前的技術來看時間旅行是否可以實現。

我們曾經建造的最快的飛船是航行者1號, 它是第一個離開我們的太陽系，並以每小時61380公里在外太空飛行的人造飛行器，而光速卻是近乎每小時10.8億公里。

航行者1號是無人飛船，它比起要載人的航天飛船(除了個人, 它需要負載個人在船上生存所須的設施)將更容易加速。所以，讓我們假設，我們將能夠製造一隻航天飛船，可以載一個人(如上例的雙胞胎的哥哥), 他並且可以擕帶一年的所須的維生用品以每小時10萬公里的速度進行外太空之旅，究竟這位旅客經過這一年, 回到地球時將會比他留在地球上的胞胎弟弟年輕了多少呢?（為了較易於計算, 我們假設並不需要太多的時間來加速和減慢飛船, 亦即飛船起飛時所須的加速和飛船到達時的減速不計在內.)

使用上面的公式，我們計出, γ是1.0000000043這個速度。一年有365天，每天有24小時, 一小時有3,600秒, 所以一年就有31,536,000秒。如果我們乘上γ和扣除一年時間後, 我們發現太空旅行者(雙胞胎的哥哥)將會比他留在地球上的雙胞胎弟弟年輕只有0.14秒。

(也即是說拿我們現有的技術, 無人飛船的每小時61380公里, 改進成為有人的每小時10萬公里, 所得出來的結果是極少的0.14秒!)

因此，現實是，時間旅行將不是我們目前的技術可以做到的範圍之內，而所有關於蟲孔，重力牆等等的推測，只是純粹的科幻小說而已。而在“TARDIS”，當然是完全不同的了，它是可行的，因為這是由時間管主發明的, 而不是由人類發明的。

P.S.: the calculation of

Pythagorean theorem :

And

Then :

P.S. : This is the first part of Einstein’s special theory of relativity, I will cover the theory of length contraction and the increase of mass later on, when I have time.

The Toyota Mirai, Fuel Cell Vehicle, is not our future car! 豐田"未來",燃料電池車, 不是我們的未來!

noreply@blogger.com (Wechner) — Tue, 07 Apr 2015 10:27:00 +0000

The Toyota Prius is a lemon that environmentally conscious people are prepared to live with in order to minimise pollution. The Prius has an engine power of 73 kW plus a battery bank. To put this into perspective, a family car like the VW Golf R has an engine power of 206 kW

The Toyota Mirai (Japanese for “future) has a hydrogen fuel cell with a power output of 9 kW and the same battery bank as the Prius. So one could say the Mirai is an 8 times greater lemon than the Prius.

9 kW is probably sufficient power to keep the batteries fully charged in a Tokyo traffic jam with more charging time available on red traffic lights than driving time, but don’t take the Mirai for a spin in a hilly country side with a full load of people on board, the batteries will be empty in no time and 9 kW of fuel cell power does not get you over, even the most gentlest of, hill slopes.

It is obvious that the Mirai is just designed as a gimmick for the 2020 Olympics with the driving routes well defined and within the physical limits of the vehicle. I am also sure that Toyota has already space allocated in the local scrapyards to take all the Mirai’s after the closing ceremony of the 2020 Olympics is over.

The web site claims that the Mirai will store 5 kg of hydrogen in two bottles at a pressure of 100 bar. Hydrogen has a density of 0.09 g/l, so 5 kg of the compressed hydrogen would take the space of 5000 g / 0.09 g/l / 100 bar = 555 l. Scaling the fuel tanks size from the picture below, my best estimate is that they will hold a volume of about 100 l, that is about one fifth of what Toyota claims. This maybe ok for the transportations required at the Olympics and who cares how much hydrogen they can hold in the scrapyard.

豐田Prius(油電混合動力車)是一個檸檬(即買了回家, 才知道是爛貨). 只是一些有環保意識的人準備與它一起生活，以減少污染。Prius 發動機的動力加上電池組才擁有73千瓦。給大家一個相關的比照: 一個家庭的汽車，如福斯高爾夫R擁有206千瓦的發動機功率.

豐田Mirai(日語為“未來"）是用氫燃料電池和Prius相同的電池組, 其輸出功率為9千瓦。因此，可以說 Mirai 比 Prius 是一個8倍更爛的檸檬。

9千瓦大概是足夠的動力來保持電池完全充電,如果你開在交通堵塞的東京, 特別如果加上交通燈常紅的話(道理很易理解吧, 當車不開動的時候, 動力肯定就用去充電的了). 但千萬不要拿 Mirai 載滿人去郊外兜風，該電池肯定好快是空的. 9千瓦的燃料電池動力, 什麼樣也不可能會載你跨越甚至是爬上最不斜的小山坡。

很明顯，Mirai 只是為2020年奧運會設計出來的噱頭. 依據了奧運會範圍內固定的駕駛路線來設計並推它至物理極限。我肯肯定，當2020年奧運會閉幕儀式後, 豐田預留的廢料堆放場空間將用來放置他們的 Mirai。

豐田網站聲稱，Mirai 將存儲5千克氫在兩個瓶子，在100巴的壓力下。氫具有0.09克/公升的密度，所以5公斤壓縮氫氣將需要5000克/ 0.09克/升/ 100 巴 = 555公升的空間。從下面的圖片我依照油箱大小比例去計算了一下, 車上最多只有持有約100公升的容積，即大約五分之一的豐田在網頁中聲稱(555 l)。100公升的容積可能就是為了迎合在奧運會運輸所需吧. 可是又有誰在乎它的氫容積持有多少呢, 反正奧運結束後, Mirai就要堆入廢料場!

No, the Mirai is not the car of the future, neither is any other fuel cell powered car. For some further reading on fuel cell cars see http://edwardwechner-9.blogspot.com.au

不，Mirai 絕對不是汽車的未來，甚至其他任何的燃料電池動力汽車也沒可能是。

有興趣知多一些有關燃料電池汽車, 請至: http://edwardwechner-9.blogspot.com.au

The fourth dimension of the universe

noreply@blogger.com (Wechner) — Thu, 02 Apr 2015 11:50:00 +0000

According to Mr. Siu two dimensions is a circle, three dimensions is a ball and four dimensions is a banana. I have never heard of anything more weird and misleading.

We know that space is four dimensional since Einstein came up with the General Theory of Relativity, but we cannot readily visualize the four dimensional space, we see only three dimensions, but we can observe some effects of the fourth dimension by the way light is bending around a massive object like a galaxy and we can measure how time is affected by the proximity of a mass by measuring the time difference between an atomic clock located on the earths surface and an atomic clock located on a satellite in space.

By definition, the fourth dimension of the universe is time, time can be measure in meters due to the constant velocity of light.

The distance of the fourth dimension is c * t, where

c = the speed of light in m/s, &

t = time in s, & m/s * s = m;

so time can be measured in meters like the other three space dimensions that we can readily visualize.

recommendations for further reading:

http://edwardwechner11.blogspot.com.au/

Experiments with falling objects, something for us to learn about the behaviour of gravitation!

noreply@blogger.com (Wechner) — Sun, 15 Feb 2015 10:12:00 +0000

Experiment 1. Misconceptions about falling objects , YouTube channel, Veritasium:

Dr Derek Muller takes to the streets with a 5kg medicine ball (exercise ball or fitness ball) and a 1 kg basketball and poses the question:

when dropped from the same height, which one will hit the ground first? You may know the correct answer, but can you explain why?

According of what Dr. Derek Muller’s explanation: the force on the medicine ball is greater than the force on the basketball, but it has more inertia and what's really important is that the ratio of force to inertia is the same for all objects, so everything accelerates at the same rate and lands at the same time.

Let’s have a look at another experiment from Brian Cox:

Experiment 2. Feathers and bowling ball:

In this experiment, a bowling ball and feathers are dropped in the air of the atmosphere, and then again in a vacuum. The result...might not surprise you since you learned what would happen in secondary school science class.

P.S. : the same experiment was done by Apollo 15 Hammer and Feather Drop (Aug., 1971):

So, why does the basket ball and the medicine ball take the same time to hit the ground? they are in air, not in a vacuum chamber!

How can you explain why the feather and the bowling ball in Brain Cox’s experiment do not arrive at the same time, when the experiment conducted in air?

The force on the bowling ball is greater than the force on the feather, but the bowling ball has more inertia, so that the ratio of force to inertia is the same for all objects, and everything accelerates at the same rate and lands at the same time. But the fact is, in air, the feather falls much slower than the bowling ball due to the air resistance. The air resistance on the feather is much greater than the air resistance on the ball.

What is wrong on the Dr. Derek Muller’s experiment?? It seems everything he said is correct!

Comparing these two videos, we find:

Dr. Muller’s experiment : the medicine ball and the basket ball, their size and shape is exactly the same. Professional Brian Cox’s experiment: the feathers and the bowling ball, their size and shape is different, so they have a different air resistance!

The reason why Dr. Muller is using the same size balls for his experiment is because they have the same air resistance , so he doesn’t need to do the experiment in a vacuum chamber to prove that gravity is a constant at a given place on earth.

Let us use now Newton’s second law to calculate the velocity in the Dr. Derek Muller’s experiment:

http://en.wikipedia.org/wiki/Gravity_of_Earth

F = Force [N] Newtons, m = mass [kg] kilo grams, a = acceleration [m/s²] meter / second²

basket ball :

F = 1kg x 10 m/s² ( actually, it should be 9.81 metres (32.2 ft) per second every second, for simplicity, we use 10 instead of 9.81)

F = 10 Newtons.

medicine ball :

F = 5kg x 10 m/s²

F = 50 Newtons.

because : a = F / m

basket ball:

a = 10 Newtons / 1kg = 10 kg * m / kg * s²= 10 m/s²

a = 50 Newtons / 5kg = 50 kg * m / kg * s²= 10 m/s²

That is the proof that the acceleration of earth is constant ! The gravitational constant. (check this out : http://en.wikipedia.org/wiki/Gravitational_constant )

----------------------------------------------------------------------------------------------------------------

Experiment 3: a 15 kg dumbbell and a 25 kg dumbbell :

And now, we are sure that:

A 15 kg dumbbell and a 25kg dumbbell will accelerates at the same rate and lands at the same time, when they are being dropped in a vacuum room.

But how about if we make a dumbbell with 15kg that has exactly the same shape and size as the 25kg dumbbell would it also land at the same time if we drop them in air?

The answer is conditional, if we would manage to keep both dumbbells exactly aligned with each other during the fall then they would have the same air resistance and consequently land at the same time. But if the dumbbells are out of alignment with each other, during the fall, one could have more air resistance than the other and consequently they do not land at the same time.

This does not come into it in the experiments with the balls because the ball shape is homogeneous and thus the air resistance is not affected by the rotational alignment of the balls, the same does not apply to the dumbbells!

Further more, it is worth to mention that the earth acceleration has the dimension [m/s²], it is only a force when we multiply it with a mass [kg], [m/s² * kg = N] N stands for Newton which is a force. So we can talk about all forces of the universe, which are measured in Newton.

We have 4 forces in the Universe:

1. The electro magnetic force

2. The weak nuclear force

3. The strong nuclear force

We know all about these three forces but not all about the fourth force.

4. The gravitational force : we know how big it is ( very very small) and we know all about its behaves, but we do not know what it is, as yet.

But there is some hope that with the discovery of the Higgs Boson (they call it the god particle) we will be able to explain gravity.

What is gravity? :

As you can see, most of the people will answer that it is a downward force that stops you from flying away from the earth. Or a force that pulls all matter together. The more matter, the greater the gravitational attracting force, so the things that have a lot of matter such as planets and moons and stars have a lot of attraction force.

We all learned these answers in the secondary school, so we just need to remember it!

But fact is that even science still cannot explain what the gravitational force is!

They know how it behaves and they know how big it is, but they still don’t know what it is!

We know that every massive object falls to the ground and we know this is because of gravity.

But back in time of Aristotle the scientific opinion was that the speed at which an objects falls was directly related to their relative weights. Thus, a heavy object would fall faster than a lighter object. After all, pick up a feather and a rock and drop the two of them, and Aristotle’s view will be prove,

the rock will indeed fall faster than feather.

As mentioned before, the gravitational force pulls all forces together. In the examples of dropping balls, feathers and dumbbells onto the ground we have ignored the movement of the earth. But since the mass of the earth is so massive as compared with our dropping items used in the experiments, we can ignore the earths movement, it is immeasurable small. Nevertheless if the falling objects getting larger, like the size of the moon for example then the movement of the earth is detectable which is shown in the following video.

If an object with comparable mass to that of the Earth were to fall towards it, then the corresponding acceleration of the Earth would be observable.

Australia Red Black Spiders紅背蜘蛛

noreply@blogger.com (Wechner) — Sun, 14 Sep 2014 13:36:00 +0000

Nearly 10 years ago, I had moved to Australia. My new neighbour Ron called me to see him close to his fence in our backyard. Ron lived behind our house and he used to be a famer, he grew vegetables and loved to check us out, he wanted to know what we are doing.

When I walked closer, he said : “Mei, do you know that the red back spider is poison and deadly?” I told him that I did not know that and I did never see one yet!

Then he pointed his finger to the fence just between both of us, and then I saw a spider with a red point on the black who was hanging in a tiny web. I screamed immediately. Ron laughed and put his finger on top of the spider and squashed it, he killed the spider. He told me this is a piece of cake, he kills red blacks all the time.

After then, I did kill one myself when we renovated our backyard. I was moving a brick which has 6 holes in the middle, a red black did hide in one of this holes, when I moved it, I saw a red back spider moving, it was already close to my finger, I was scared and dropped the brick onto the floor, the spider was thrown out and fell onto the floor, I immediately stepped on it.

Then I knew red back spiders are not aggressive, just don’t wait until they bite you, you will be fine.

當我初來澳洲住, 我家後花園有個老鬼鄰居, 常常關注我家的動靜.

有天他見我在後園種花. 他叫我走到圍欄去聊天.

並問我道: 你可知否悉尼紅背蜘蛛是惡毒無比嗎?

我剛來報導, 當然對那些小動物是沒什興趣的, 當他知道我一無所知..... 就開始陰陰咀笑....

佢用手指一指角落, 說: 看, 那隻就是啦!

我看到一隻細小黑蜘蛛, 背部圓圓上是有一小紅點. 動也不動, 掛在蛛網上.

隨著, 老鬼便用手指往蜘蛛上一擠壓, 我"嘩"一聲, 老鬼覺得好不威風. 他說他殺紅背蜘蛛當食生菜.

後來, 我家後園重修, 我自己也看到過不少紅背蜘蛛, 也自己殺死過一隻.

當時是好害怕的, 它就是躲在一磚頭裡, 當我移動磚頭時發現了它, 立即就嚇到掉到地上, 它也被拋出掉在地上, 我好自然就往它身上踩去.

依我所見, 紅背蜘蛛根本不活躍的, 不是網上說的會向你攻擊的. 它們行動不快, 你有足夠時間殺鬼死它們, 肯定快過它們襲擊你.

Red Back Spider - Attenborough: Life in the Undergrowth – BBC

Red Back Spider - toilet spider

http://en.wikipedia.org/wiki/Redback_spider

紅背蜘蛛是一種劇毒蜘蛛，身長在2—8mm之間，背部有個紅色印記，攻擊性極強，被咬中五分鐘後傷口開始發熱發痛，如無血清治療，半小時內死亡。但自1956年以來，並無記錄在案的因紅背蜘蛛咬傷而死亡的案例。

紅背蜘蛛偏好棲息於黑暗乾燥處，雌性紅背蜘蛛會在交配後，把消化液注入雄蜘蛛的身體和把雄蜘蛛吃掉。據研究發現，母紅背蜘蛛壽命有2-3年；公蜘蛛壽命只有6-7個月，有83%的雄性紅背蜘蛛在沒有交配之前就死掉了。

有趣:

1. 紅背蜘蛛網: 晚上建築, 並且是三維建築的, 不單是和橫濶, 而是向下向深. (睇BBC, attenborough – Life the Undergrowth 就是.) 只要你想像天上就是一般的蜘蛛網, 可是他從網中一些線向下再築更多的支線接觸著地面或平面. 當有小動物經過觸摸到, 就被纏著整隻獵物被彈起. 因為彈起在半空, 而沒有了其中東西可以被依靠, 紅背蜘蛛就可以爬下來把你用網絲包起來, 慢慢吸食.

2. 紅背蜘蛛原來是外來客. 不是原產澳洲! (睇片: Red Back Spider - toilet spider)

Billy Connolly’s Big Send Off

noreply@blogger.com (Wechner) — Wed, 16 Jul 2014 06:41:00 +0000

When my papa left me in 2006, I was always afraid of death, because I was with him in hospital the last few days before he died...... all the terrible things around him, breathing facility, all the plastic pipes from his lungs, arms, mouth... all around his body....etc. I always think may be one day it will be my turn to be in the same situation like my papa was.......

Tonight, I watched a documentary, Billy Connolly's Big Send Off, I think it is a good documentary and it is worth to spend some time to have look at it........ for those who care for elderly parents or any other family member in that situation. It is inevitably that we are all going to die.

Billy Connolly embarks on a personal and enlightening journey where he looks at our attitudes towards death. He immerses himself in a range of experiences and talks about death with his pal Eric Idle.

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