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相关概念视频

Eccentricity of an Ellipse01:27

Eccentricity of an Ellipse

An ellipse is a fundamental conic section defined by the constant sum of distances from any point on its curve to two fixed points, known as the foci. This geometric property can be physically demonstrated using a pencil, string, and two pins. By anchoring the string at both ends and maintaining it taut with a pencil, one can trace the outline of an ellipse.The shape and extent of the ellipse are determined by its eccentricity, e, defined as the ratio of the distance between the center and a...
Kepler's First Law of Planetary Motion01:10

Kepler's First Law of Planetary Motion

In the early 17th century, German astronomer and mathematician Johannes Kepler postulated three laws for the motion of planets in the solar system. He formulated his first two laws based on the observations of his forebears, Nikolaus Copernicus and Tycho Brahe.
Polish astronomer Nikolaus Copernicus put forth a theory that stated a heliocentric model for the solar system. According to this heliocentric theory, all the planets, including Earth, orbit the Sun in circular orbits.
On the other hand,...
Maximum Size of Aggregate01:12

Maximum Size of Aggregate

The maximum size of aggregate is defined as the aperture of the sieve retaining 15 percent or more of the particles present in the aggregate sample. The aggregate's maximum size impacts the concrete's water requirement, workability, and strength. Larger aggregates reduce the surface area needing cement paste coverage, which can lower water needs, thereby allowing a decrease in the water-to-cement ratio when the desired workability and richness of the mix are to be maintained, which can result...
Ellipses01:30

Ellipses

An ellipse is formed when a right circular cone is intersected by an inclined plane that does not cut through its base. This intersection yields a closed, symmetric curve characterized by distinctive geometric properties. Most notably, an ellipse is defined as the collection of all points in a plane for which the combined distances to two fixed points—called the foci—remain constant.The ellipse features two principal axes: the major and the minor axes. The major axis is the longest diameter,...
Hyperbolas01:30

Hyperbolas

A hyperbola is a conic section produced when a double-napped cone is intersected by a plane at an angle steeper than the slope of the cone, such that it cuts through both nappes. This intersection yields two separate, mirror-image curves known as branches, which open away from each other along the transverse axis. The nearest points on each branch to the hyperbola’s center are termed vertices, and the distance from the center to a vertex is denoted by a. Perpendicular to the transverse axis is...
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Conformations of Ethane and Propane

In an organic molecule, free rotation about the carbon-carbon single bond results in energetically different conformers of the molecule. Due to this rotation, called the internal rotation, ethane has two major conformations — staggered and eclipsed.
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered ethane, the...

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相关实验视频

Updated: Jul 11, 2026

Scattering And Absorption of Light in Planetary Regoliths
11:34

Scattering And Absorption of Light in Planetary Regoliths

Published on: July 1, 2019

赫克托:最大的高度延长的小行星.

W K Hartmann, D P Cruikshank

    Science (New York, N.Y.)
    |February 29, 1980
    PubMed
    概括

    新的观测揭示了特洛伊小行星624,赫克托尔.

    科学领域:

    • 天文学和天体物理学.
    • 星球科学 星球科学

    背景情况:

    • 小行星624",赫克托尔"是一颗特洛伊木马小行星.
    • 它的旋转光曲线呈现出高振幅,暗示着不寻常的特征.

    研究的目的:

    • 为了调查赫克托的旋转光曲线中高振幅的原因.
    • 为了评估小行星624的物理特征和形成假设,Hektor.

    主要方法:

    • 分析了1979年4月获得的小行星624号Hektor的新观测数据.
    • 解释旋转光曲线数据以推断物体形状和表面特性.

    主要成果:

    • 赫克托尔旋转光曲线的高幅度归因于其长长的形状.
    • 观测排除了白度变化作为光曲线幅度的主要原因.

    结论:

    • 小行星624号,赫克托尔具有显著的延长形状.
    • 这些发现支持了赫克托是一个由两个大小相似的特洛伊木马之间的碰撞形成的复合小行星的假设,为行星积累提供了洞察力.

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