神秘的黑洞

黑洞很容易让人想像成一个“黑窟窿”,其实它和地球、太阳一样,都是一种天体。黑洞概念最早由爱因斯坦提出。当一颗恒星衰老时,它的内部能量耗尽,核心开始塌陷、缩小,最后形成体积小、密度大的星体。巨大的引力使得处于引力场的任何物质都向恒星中心靠近,即使光也无法“逃出去”,从而形成黑洞。2002年10月17日,科学家宣布,通过“哈勃”太空望远镜,观察一颗围绕银河系核心运行的天体,证实银河系中央存在一个巨大的黑洞。上图是这个黑洞处于星群中间的概念图,由科学家绘制而成。(欧文)神秘的黑洞@欧文     

科学家探索黑洞之谜

初中生之友如果一个天体质量足够大、体积足够小，那么它的引力大得就会连光都逃不出去。这种天体就是黑洞。黑洞这一概念刚提出来时曾被人们称作痴人说梦，但科学家的研究日益证明这种天体的确存在，一些科学家还因研究黑洞而出了名，其中最有名的一个要算英国科学家霍金。近年来，科学家又发现了黑洞的许多新的怪脾气。英国科学家对由巨大黑洞和小型黑洞发出的X射线辐射进行了比较研究后发现，尽管黑洞其大小各异、质量也相差甚远，但它们在吸收周围气体，同时放射出X射线的过程中有着相同的波动规律，如同快慢不同但演唱音调相同的“同…     

浅谈黑洞那些事儿

1915年,爱因斯坦提出了广义相对论.该理论预言了黑洞的存在,并开启了人类对黑洞的不断探索.就在刚刚过去的2019年里,科学家公布了首张黑洞照片,发现了目前为止具有最大质量的恒星级黑洞和最小质量的黑洞.我们知道,黑洞是一种引力极大的天体,会吞噬其周围的任何物质,甚至连速度最快的光子都无法逃离.那么黑洞是如何形成的呢?黑洞完全不发射和反射光,我们又该如何观测它呢?黑洞距离地球如此之远,其质量又是如何计算出来的呢?下面我们来谈谈这种神秘天体.     

宇宙中的黑洞

黑洞由广义相对论预言,是一个由奇异面所包围、含有中心奇点的时空区域。宇宙中的黑洞特指具有观测效应的一些特殊天体。由于黑洞本身不产生电磁波辐射,在观测上,人们通过分析黑洞周围物质的电磁波辐射以及引力波事件,获得恒星级黑洞和超大质量黑洞存在的观测证据。此外,物理学家还预言了原初黑洞的存在,在未来也有可能被观测检验,本文简要介绍人类对宇宙中黑洞的观测研究进展。     

哈勃望远镜发现了黑洞存在的证据

哈勃望远镜发现了黑洞存在的证据在宇宙间所有已知的星体之中，最不可思议而又让人好奇的天体相信非“黑洞”莫属。这种奇异天体是６０年代初由英国剑桥著名理论天体物理学家霍金斯最先预测的。他从恒星的物理研究，发现当质量硕大的星体演化至晚期，除会造成轰然爆炸的超...     

望向黑洞的慧眼——HXMT卫星

正同学们,黑洞这个神秘天体,就像魔咒一般深深地吸引着我们。多年来,人类对黑洞的探索从未停止,我国的科学家也对黑洞进行了深入的研究和不懈的探索。(小好奇)为了研究黑洞、中子星等高能致密天体的基本物理性质以及它们对周围时空的影响,中国科学院高能物理研究所和航天科技集团五院等单位研制了我国第一颗空间X射线天文卫星——HXMT卫星。     

黑洞

虽然,早在二百多年前就有人讨论了现在称作黑洞的概念,但“黑洞”这个名字是到了1967年才由美国物理学家约翰·惠勒提出来。     

漫谈黑洞与霍金

黑洞是广义相对论预言的天体。爱因斯坦的广义相对论认为,万有引力不是真正的力,而是时空弯曲的表现。时空弯曲是由于物质存在造成的。美国物理学家奥本海默(第一颗原子弹的总设计师)指出,当天体附近的时空弯曲得极其厉害,以至于它发射的光都会被“弯”回去的时候,外面的人就不可能看到这个天体。这个天体就是我们所说的黑洞。     

科学上的六大悬案

科学上的六大悬案一、宇宙天体除地球外，还有没有生命存在。二、黑洞天体美国和加拿大科学家发现银河系的大麦哲伦星系中有一个“黑洞”．质量为太阳的８—１２倍，但它到底是不是黑洞，还要等待找出证据。三、引力辐射探测１９１６年爱因斯坦从理论上证明，引力是一种波...     

百万计的黑洞使银河系支离破碎

百万计的黑洞使银河系支离破碎李洪译佳丽校据荷兰一位天体物理学家计算，我们的银河系至少有１亿个黑洞。这是一个大胆的推断，因为，迄今天文学家在我们的银河系只确认了４个黑洞。阿姆斯特丹大学的赫费尔说：“显然，以前不曾有人作过这种计算。黑洞是在超新星爆炸中结...     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.     

团图为数的图中的闭团贯数

Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.