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相关概念视频

The Evidence for Evolution02:55

The Evidence for Evolution

Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of novel varieties and entire new species. These changes are responsible for the diverse forms of life inhabiting the planet. The evidence for evolution suggests that all living organisms descended from common ancestors.The collection of fossils within sedimentary rocks give a record of common ancestry and often depicts the history of evolution.
Schwarzschild Radius and Event Horizon01:21

Schwarzschild Radius and Event Horizon

No object with a finite mass can travel faster than the speed of light in a vacuum. This fact has an interesting consequence in the domain of extremely high gravitational fields.
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape velocity with the...
Detection of Black Holes01:10

Detection of Black Holes

Although black holes were theoretically postulated in the 1920s, they remained outside the domain of observational astronomy until the 1970s.
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
Null and Alternative Hypotheses01:16

Null and Alternative Hypotheses

The actual hypothesis testing begins by considering two hypotheses. They are termed  the null hypothesis and the alternative hypothesis. These hypotheses contain opposing viewpoints.
The null hypothesis, denoted by H0 is a statement of no difference between the variables—they are not related. This can often be considered the status quo. As  a result if you cannot accept the null, it requires some action.
The alternative hypothesis, denoted by H1 or Ha, is a claim about the population that is...
Difference from Background: Limit of Detection01:05

Difference from Background: Limit of Detection

The limit of detection (LOD) is the smallest amount of analyte that can be distinguished from the background noise. The LOD value corresponds to the concentration at which the analyte signal is three times larger than the standard deviation of the blank signal. Below this value, the analyte signal cannot be differentiated from the background noise. It is calculated by dividing the calibration slope by 3 times the standard deviation of the blank signals.
The LOD indicates the presence or absence...
Norton's Theorem01:14

Norton's Theorem

Norton's theorem is a fundamental principle stating that a linear two-terminal circuit can be substituted with an equivalent circuit, which comprises a current source (ⅠN) in parallel with a resistor (RN). Here, ⅠN represents the short-circuit current flowing through the terminals, and RN stands for the input or equivalent resistance at the terminals when all independent sources are deactivated. This implies that the circuit illustrated in Figure (a) can be exchanged with the one depicted in...

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相关实验视频

Updated: Jul 23, 2026

Bioluminescence Imaging to Detect Late Stage Infection of African Trypanosomiasis
07:59

Bioluminescence Imaging to Detect Late Stage Infection of African Trypanosomiasis

Published on: May 18, 2016

黑洞存在的证据.

Mitchell C Begelman1

  • 1JILA, University of Colorado, 440 UCB, Boulder, CO 80309, USA. mitch@jila.colorado.edu

Science (New York, N.Y.)
|June 21, 2003
PubMed
概括

黑洞是大量的宇宙物体,恒星质量和超大质量类型几乎在每一个星系中都存在. 本综述探讨了它们的人口结构,环境相互作用,形成以及广义相对论的测试.

科学领域:

  • 天体物理学 天体物理学
  • 宇宙学的宇宙学是什么?
  • 一般相对论一般相对论.

背景情况:

  • 黑洞遍布整个宇宙,每个星系有数以百万计的恒星质量黑洞,大多数星系的中心有一个超大质量黑洞.
  • 恒星质量黑洞是巨大的恒星的残余,而超大质量黑洞的质量范围从数百万到数十亿太阳质量.

研究的目的:

  • 为了回顾宇宙中黑洞的人口结构和分布.
  • 讨论黑洞的环境相互作用和形成/增长调节.
  • 检查验证爱因斯坦关于黑洞时空扭曲的广义相对论的进展情况.

主要方法:

  • 观测天文学数据分析.
  • 理论天体物理学建模.理论天体物理学建模.
  • 宇宙学模拟. 宇宙学模拟.

主要成果:

  • 黑洞被证实在星系中很常见,无论是恒星质量还是超大质量.
  • 确定了影响黑洞种群的各种环境相互作用和监管因素.
  • 目前正在进行的研究提供了支持广义相对论关于黑洞物理学的预测的证据.

结论:

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  • 黑洞是银河系结构和宇宙进化的基本组成部分.
  • 了解黑洞的人口结构和相互作用对天体物理学至关重要.
  • 进一步的研究继续验证和完善我们对黑洞和时空的理解.