相关概念视频
01:10Detection of Black Holes
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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...
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...
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02:12The Wave Nature of Light
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The nature of light has been a subject of inquiry since antiquity. In the seventeenth century, Isaac Newton performed experiments with lenses and prisms and was able to demonstrate that white light consists of the individual colors of the rainbow combined together. Newton explained his optics findings in terms of a "corpuscular" view of light, in which light was composed of streams of extremely tiny particles traveling at high speeds according to Newton's laws of motion.
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01:21Schwarzschild Radius and Event Horizon
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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...
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...
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01:20Momentum And Radiation Pressure
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An object absorbing an electromagnetic wave would experience a force in the direction of propagation of the wave. This force occurs because electromagnetic waves contain and transport momentum. The force accounts for the wave's radiation pressure exerted on the object. Maxwell's prediction was confirmed in 1903 by Nichols and Hull by precisely measuring radiation pressures with a torsion balance. The measuring instrument had mirrors suspended from a fiber kept inside a glass container.
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01:13What is Matter?
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The substance of the universe—from a grain of sand to a star—is called matter. Scientists define matter as anything that occupies space and has mass. An object’s mass and its weight are related concepts, but not quite the same. An object’s mass is the amount of matter contained in the object and is the same whether that object is on Earth or in the zero-gravity environment of outer space. An object’s weight, on the other hand, is its mass as affected by the pull of...
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01:05Collisions in Multiple Dimensions: Introduction
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It is far more common for collisions to occur in two dimensions; that is, the initial velocity vectors are neither parallel nor antiparallel to each other. Let's see what complications arise from this. The first idea is that momentum is a vector. Like all vectors, it can be expressed as a sum of perpendicular components (usually, though not always, an x-component and a y-component, and a z-component if necessary). Thus, when the statement of conservation of momentum is written for a...
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暗物质和镜子世界
1Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, MD 20742, USA.
Entropy (Basel, Switzerland)
|April 26, 2024
概括
暗物质可能存在于一个平行镜像宇宙中. 这种模型解释了暗物质的丰富性,并要求镜子世界比我们更冷,为宇宙的膨胀再热温度设置上限.
科学领域:
- 宇宙学的宇宙学是什么?
- 粒子物理学 粒子物理学
- 天体物理学 天体物理学
背景情况:
- 天文学证据表明暗物质,但实验室搜索没有结果.
- 猜测提出暗物质居住在一个平行宇宙中,并以引力相互作用.
研究的目的:
- 为了探索暗物质的镜像世界模型.
- 为了研究镜面对称对宇宙学的含义.
- 为了解释物质-暗物质巧合问题.
主要方法:
- 假设一个镜子世界,具有相同的力量和物质.
- 分析大爆炸核合成的镜像模型要求.
- 从镜子世界的冷酷和物质-暗物质巧合中得出约束.
主要成果:
- 镜子世界模型提供了一个暗物质的候选者.
- 一致性意味着在膨胀再加热温度上的上限为~10^6.5GeV.
- 镜子世界可能由组成,而不是,与可见宇宙形成鲜明对比.
结论:
- 镜子世界假设为暗物质难题提供了一个潜在的解决方案.
