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Time: 第442次例會，2014年6月20日(週五)晚上19:00~21:30
Place:
丹堤咖啡開封店三樓 Dante Café 3rd Floor
台北市開封街一段16號3樓（捷運台北站 ）
Fl. 3, No.16, Sec. 1, Kaifeng St., Zhongzheng Dist., Taipei City
Taipei MRT Station
http://www.happyforum.org/happy/viewtopic.php?f=2&t=15
There is a minimum charge at Dante Coffee. Please order a drink or a meal at Cashier when you step in. Thanks for your cooperation.
Agenda:
19:00~19:10 Session One - Free talk
19:10~19:30 Speaker of the Day: Cathy – City of Angels-Bangkok, Thailand
19:30~20:05 Video Session: Nova – Hunting the Edge of Space
20:05~20:50 Session Two – Discussion
20:50~21:10 Happy Time
Host: Denise
Speakers of the Day: Cathy
Topic: The Universe
Source:
Article:
＊ The Universe ＊
The most popular theory of our universe's origin centers on a cosmic cataclysm unmatched in all of history—the big bang. This theory was born of the observation that other galaxies are moving away from our own at great speed, in all directions, as if they had all been propelled by an ancient explosive force.
Big bang proponents suggest that some 10 billion to 20 billion years ago, a massive blast allowed all the universe's known matter and energy—even space and time themselves—to spring from some ancient and unknown type of energy.
The theory maintains that, in the instant—a trillion-trillionth of a second—after the big bang, the universe expanded with incomprehensible speed from its pebble-size origin to astronomical scope. Expansion has apparently continued, but much more slowly, over the ensuing billions of years.
Scientists can't be sure exactly how the universe evolved after the big bang. Many believe that as time passed and matter cooled, more diverse kinds of atoms began to form, and they eventually condensed into the stars and galaxies of our present universe.
Origins of the Theory
A Belgian priest named Georges Lemaître first suggested the big bang theory in the 1920s when he theorized that the universe began from a single primordial atom. The idea subsequently received major boosts by Edwin Hubble's observations that galaxies are speeding away from us in all directions, and from the discovery of cosmic microwave radiation by Arno Penzias and Robert Wilson.
The big bang theory leaves several major questions unanswered. One is the original cause of the big bang itself. Several answers have been proposed to address this fundamental question, but none has been proven—and even adequately testing them has proven to be a formidable challenge.
Stars are cosmic energy engines that produce heat, light, ultraviolet rays, x-rays, and other forms of radiation. They are composed largely of gas and plasma, a superheated state of matter composed of subatomic particles.
Though the most familiar star, our own sun, stands alone, about three of every four stars exist as part of a binary system containing two mutually orbiting stars.
No one knows how many stars exist, but the number would be staggering. Our universe likely contains more than 100 billion galaxies, and each of those galaxies may have more than 100 billion stars.
Yet on a clear, dark night Earth's sky reveals only about 3,000 stars to the naked eye. Humans of many cultures have charted the heavens by these stars.
〜 Appearance of the Stars
Some stars have always stood out from the rest. Their brightness is a factor of how much energy they put out, which is called their luminosity, and also how far away from Earth they are.
Stars in the heavens may also appear to be different colors because their temperatures are not all the same. Hot stars are white or blue, whereas cooler stars appear to have orange or red hues.
Stars may occur in many sizes, which are classified in a range from dwarfs to supergiants. Supergiants may have radii a thousand times larger than that of our own sun.
Hydrogen is the primary building block of stars. The gas circles through space in cosmic dust clouds called nebula. In time, gravity causes these clouds to condense and collapse in on themselves. As they get smaller, the clouds spin faster because of the conservation of angular momentum—the same principle that causes a spinning skater to speed up when she pulls in her arms.
Building pressures cause rising temperatures inside such a nascent star, and nuclear fusion begins when a developing young star's core temperature climbs to about 27 million degrees Fahrenheit (15 million degrees Celsius).
Our own sun exists in a state of nuclear fusion during which they will emit energy for billions of years by converting hydrogen to helium. Stars evolve over billions of years. As stars move toward the end of their lives much of their hydrogen has been converted to helium. Helium sinks to the star's core and raises the star's temperature—causing its outer shell to expand. These large, swelling stars are known as red giants.
The red giant phase is actually a prelude to a star shedding its outer layers and becoming a small, dense body called a white dwarf. White dwarfs cool for billions of years, until they eventually go dark and produce no energy. At this point, which scientists have yet to observe, such stars become known as black dwarfs.
〜 Black Holes
A few stars eschew this evolutionary path and instead go out with a bang—detonating as supernovae. These violent explosions leave behind a small core that may become a neutron star or even, if the remnant is large enough, a black hole.
According to science fiction, black holes are trying to suck us all in since it possesses incredible gravitational pull. If you take a rocket close to the event horizon, but don’t cross it. For every minute you spend there, a thousand year will pass on Earth. It’s hard to believe, but that’s what happens. Gravity trumps time.
If you cross the event horizon, then what? You will appear frozen at the hole’s edge Frozen for an infinite amount of time. There are some debates about the moment you cross over. It is possible there exists what’s call a fire wall, when you cross over, you promptly burn up. And if fire wall doesn’t exist, you will still be ripped apart; pieces of you will reach the bottom of the black hole.
〜 Galaxies
Galaxies are sprawling space systems composed of dust, gas, and countless stars. The number of galaxies cannot be counted—the observable universe alone may contain 100 billion. Some of these distant systems are similar to our own Milky Way galaxy, while others are quite different.
Galaxies with less than a billion stars are considered "small galaxies." In our own galaxy, the sun is just one of about 100 billion stars.
Galaxies are classified into three main types: spiral galaxies, elliptical galaxies, and irregular galaxies.
Spiral galaxies, such as the Milky Way, consist of a flat disk with a bulging center and surrounding spiral arms. The galaxy's disk includes stars, planets, dust, and gas—all of which rotate around the galactic center in a regular manner.
This spinning motion, at speeds of hundreds of kilometers per second, may cause matter in the disk to take on a distinctive spiral shape like a cosmic pinwheel. Some spiral galaxies obtain even more interesting shapes that earn them descriptive names, such as sombrero galaxies.
Older stars reside in the bulge at the center of the galactic disk. Many new stars also form in spiral systems, and their disks are surrounded by a halo, which scientists believe is rich with mysterious dark matter.
Elliptical galaxies are shaped as their name suggests. They are generally round but stretch longer along one axis than along the other. They may be nearly circular or so elongated that they take on a cigarlike appearance.
Elliptical galaxies contain many older stars, up to one trillion, but little dust and other interstellar matter. Their stars orbit the galactic center, like those in the disks of spiral galaxies, but they do so in more random directions. Few new stars are known to form in elliptical galaxies.
The universe's largest known galaxies are giant elliptical galaxies, which may be as much as two million light-years long. Elliptical galaxies may also be small, in which case they are dubbed dwarf elliptical galaxies.
Galaxies that are not spiral or elliptical are called irregular galaxies. Irregular galaxies appear misshapen and lack a distinct form, often because they are within the gravitational influence of other galaxies close by.
Our own Milky Way may someday merge with the Andromeda galaxy—just two million light-years away and visible to the naked eye from Earth's Northern Hemisphere.
These intergalactic processes may be part of natural evolution by which irregular galaxies transform into one of the other shapes, and by which spiral galaxies eventually become elliptical galaxies—as scientists believe they must.
There are still lots of mysteries about the universe remain unknown. Mankind is seeking the earth-like planet in case one day the Sun exhausts its fuel and we need move to a new habitat such as the Mars.
Remark: The above article is excerpted from National Geographic Magazine.
Video:
http://www.youtube.com/watch?v=iYqCMTAzarg
Questions:
1. There are numerous stars and planets existing in the Universe. Do you believe there are aliens living on other planets? What do they look like in your mind? Please share some information in this regard with your group mate.
2. Do you know what are supernova, white dwarf, dark energy and dark matter?
3. There are so many magnificent nebulas in Universe, can you name one of them which impress you the most?
4. Except of Big Bang theory, is there any other theory possible to launch the Universe? Use your imagination and discuss with your group mates.
5. In the future, if humankind is able to travel into the Universe, which appearance you are eager to see first? Such as black hole, any nebula, simply the Mars or any other? Why are you fascinated with it?
例會須知
時間地點須知：
http://www.happyforum.org/happy/viewtopic.php?f=2&t=15
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參與例會，請自行列印當週的討論文章，並帶至現場
http://www.happyforum.org/happy/viewforum.php?f=33
參與例會，請勿討論政治/種族/宗教/性，經勸導無效者，不得參加本會任何活動
http://www.happyforum.org/happy/viewtopic.php?f=1&t=1766
週六晚餐(Saturday Dinner)
http://www.happyforum.org/happy/viewforum.php?f=76
戶外活動(Club Outing)
http://www.happyforum.org/happy/viewforum.php?f=72
所有行程(All Schedule)
http://www.happyforum.org/happy/viewtopic.php?t=883
