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相关概念视频

Magnetism01:30

Magnetism

Magnets are commonly found in everyday objects, such as toys, hangers, elevators, doorbells, and computer devices. Experimentation on these magnets shows that all magnets have two poles: one is labeled north (N) and the other south (S). Magnetic poles repel if they are alike and attract if unlike. Moreover, both poles of a magnet attract unmagnetized pieces of iron.
An individual magnetic pole cannot be isolated. No matter how small, every piece of a magnet contains a north pole and a south...
Gravitation01:16

Gravitation

In the years before Newton, a general belief prevailed that different laws governed objects in the sky than objects on Earth. When Kepler wrote down the three laws of planetary motion, explaining in detail the geometrical properties of the planetary orbits around the Sun, there was no immediate idea to discern their connection with more fundamental laws. It was Isaac Newton who, in 1665–66, figured out the connection between planetary motion, the motion of the moon around the Earth, and the...
Magnetic Fields01:27

Magnetic Fields

A moving charge or a current creates a magnetic field in the surrounding space, in addition to its electric field. The magnetic field exerts a force on any other moving charge or current that is present in the field. Like an electric field, the magnetic field is also a vector field. At any position, the direction of the magnetic field is defined as the direction in which the north pole of a compass needle points.
A magnetic field is defined by the force that a charged particle experiences...
Atomic Nuclei: Larmor Precession Frequency01:11

Atomic Nuclei: Larmor Precession Frequency

The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession, and the angular frequency...
Diamagnetism01:26

Diamagnetism

Materials consisting of paired electrons have zero net magnetic moments. However, when these materials are placed under an external magnetic field, the moments opposite to the field are induced. Such materials are called diamagnets. Diamagnetism is the response of the diamagnets when placed in an external magnetic field.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets.
Potential Due to a Magnetized Object01:24

Potential Due to a Magnetized Object

Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...

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相关实验视频

Updated: Jun 26, 2026

Simulating Imaging of Large Scale Radio Arrays on the Lunar Surface
06:14

Simulating Imaging of Large Scale Radio Arrays on the Lunar Surface

Published on: July 30, 2020

早期的月球磁力是什么

Ian Garrick-Bethell1, Benjamin P Weiss, David L Shuster

  • 1Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 54-521, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. iang@mit.edu

Science (New York, N.Y.)
|January 20, 2009
PubMed
概括

月球可能有一个金属核心动力发电机,在42亿年前产生了磁场. 对古代月球岩石的分析支持了这个核心动力发电机假设.

科学领域:

  • 行星科学 行星科学
  • 地质物理学 地质物理学
  • 月球科学 月球科学

背景情况:

  • 月球上的金属核心和动力发电机的存在是不确定的.
  • 月球地的磁化可能源于撞击,而不是动力发电机.

研究的目的:

  • 研究月球磁化的起源.
  • 确定月球是否拥有古老的核心动力发电机.

主要方法:

  • 对托克托利特的磁性测量 76535.5.
  • 40Ar/39Ar 月球岩石的热年代测定.

主要成果:

  • 确定了已知最古老的未受冲击的月球岩石,特洛克托利特76535.
  • 数据表明,长期存在的月球磁场 (≥1微图星) 存在于42亿年前.

结论:

  • 月球场的早期年龄,强度和持续时间支持一个古老的月球核心动力发电机.
  • 这一发现挑战了冲击产生的磁化理论.

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