Name: weightlessness and einstein’s equivalence
Uploaded: 2023-04-30T11:07:46.000Z
Duration: 1 min 18 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Physics

PH.9

PH.9.c

Principle of Equivalence

Космический челнок, вращающийся вокруг Земли, находится в движении свободного падения, ограниченный гравитационной силой Земли. Однако космонавт внутри космического челнока чувствует невесомость, как будто на него не действует никакая сила.
Предположим, что космический челнок разгоняется вверх со скоростью 9,8 м/с2; пол помещения космического челнока будет двигаться вверх к парящему астронавту. Однако астронавту кажется, что он ускоряется вниз к полу космического челнока со скоростью 9,8 м/с2.
Для него ускорение создает тягу в космическом шаттле, подобную гравитации на поверхности Земли. Сидя внутри закрытой комнаты космического шаттла, астронавт не может различить, находится ли он на Земле или ускоряется в космосе.
Поэтому Эйнштейн утверждал, что нет никакой разницы между равномерным гравитационным полем и равномерным ускорением в отсутствие гравитации. Это известно как принцип эквивалентности.
Он пришел к выводу, что гравитация не является силой между двумя массами, а возникает в результате взаимодействия материи и пространства.

Принцип эквивалентности

По словам Альберта Эйнштейна (1897-1955), свободное падение и ощущение невесомости неразрывно связаны между собой. Находясь в свободном падении под действием гравитации, например, прыгнув с парашюта из самолёта, человек чувствует себя полностью невесомым. Аналогично, человек, спускающийся в лифте, может ощущать частичную невесомость. В общем случае предполагается, что объект в равномерном гравитационном поле и объект, подвергающийся постоянному ускорению в отсутствие гравитации, находятся в одинаковых экспериментальных условиях (то есть нет эксперимента, который мог бы различить эти две ситуации). Это утверждение называется принципом эквивалентности.

Принцип рассматривает фундаментальное предположение закона гравитации Ньютона: предполагается, что массы, определяющие силу притяжения между двумя объектами, являются теми же массами, которые определяют их реакцию на силы в соответствии с законами движения Ньютона. Однако эти две массы, иногда называемые гравитационной массой и инерционной массой, могут фактически различаться. В результате сочетания закона гравитации Ньютона с законами движения Ньютона получаются результаты, согласующиеся с экспериментами. Другими словами, это предположение оказывается экспериментально верным. Однако причина этого явления не понятна.

Согласно принципу эквивалентности, это не совпадение. Фундаментально, равномерное ускорение и гравитация являются одним и тем же.

Связывая равномерное ускорение с гравитацией, Эйнштейн предложил, что гравитация не является силой между двумя объектами. Вместо этого, это эффект воздействия двух объектов на пространство-время вокруг них, которое, в свою очередь, определяет их динамику. Он математически описал эти идеи в своей общей теории относительности в 1915 году.

Этот текст адаптирован из <a href="https://openstax.org/books/university-physics-volume-1/pages/13-7-einsteins-theory-of-gravity">Openstax, University Physics Volume 1, Section 13.7: Einstein's Theory of Gravity.</a>

Согласно Альберту Эйнштейну (1897-1955), свободное падение и ощущение невесомости неразрывно связаны. Если бы человек находился в свободном падении под действием силы тяжести, для...

Education

JoVE Core

Физика

Unit 1

Раздел 1

Gravitation

Гравитация

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

weightlessness and einstein’s equivalence

Weightlessness and Einstein’s equivalence principle are closely connected in gravity. A person in free fall under gravity, such as someone diving toward Earth from an airplane, would feel completely weightless. A person descending in a lift may feel partially weightless.

The principle of equivalence says that an object in a uniform gravitational field and an object accelerating at a constant rate with no gravity are under the same experimental conditions. In other words, no experiment can tell the two situations apart. This idea links gravity with uniform acceleration.

The principle also addresses a key assumption in Newton’s law of gravitation. It assumes that the mass that creates gravitational attraction is the same as the mass that responds to force in Newton’s laws of motion. These are sometimes called gravitational mass and inertial mass. They can be different in practice, but the results from combining Newton’s law of gravitation with Newton’s laws of motion still match experiments.

Einstein argued that this agreement is not a coincidence. He proposed that gravitation is not simply a force between two objects. Instead, it is an effect of those objects on the space-time around them, which then shapes their motion. He turned these ideas into mathematics in his general theory of relativity in 1915.

Weightlessness and Einstein’s Equivalence

gravitation

Newton’s Law Behind Planet Motion

Newton’s law of gravitation links falling objects, the Moon’s orbit, and planetary motion. Before Newton, many people thought the sky and Earth followed different laws. Kepler later described the three laws of planetary motion, but their connection to a deeper force was still unclear. Isaac Newton made that connection in 1665 to 1666. He showed that the same phenomenon explains why objects fall to Earth and why the Moon moves around Earth. He also found that the Moon’s centripetal acceleration...

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newton's law of gravitation

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reduced mass coordinates: isolated two-body problem

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Center of Mass in the Two-Body Problem

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acceleration due to gravity on other planets

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Measuring Gravity on Distant Planets

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apparent weight and the earth's rotation

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variation in acceleration due to gravity near the earth's surface

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the principle of superposition and the gravitational field

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escape velocity

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circular orbits and critical velocity for satellites

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Orbital Speed and Period in Circular Paths

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energy of a satellite in a circular orbit

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Satellite Orbits and Energy in Space

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kepler's first law of planetary motion

Planet Orbits as Ellipses

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kepler's second law of planetary motion

Kepler's Equal-Area Planet Motion

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kepler's third law of planetary motion

Kepler’s Planet Distance Law

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tidal forces

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schwarzschild radius and event horizon

Escape Velocity Limits and Black Holes

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detection of black holes

How Astronomers Find Black Holes

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principle of equivalence

Weightlessness and Einstein’s equivalence principle are closely connected in gravity. A person in free fall under gravity, such as someone diving toward Earth from an airplane, would feel completely weightless. A person descending in a lift may feel partially weightless. The principle of equivalence says that an object in a uniform gravitational field and an object accelerating at a constant rate with no gravity are under the same experimental conditions. In other words, no experiment can tell...

space-time curvature and the general theory of relativity

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key terms and concepts

Learn how free fall, weightlessness, and constant acceleration connect in Einstein’s equivalence principle and why it led to general relativity.

Weightlessness and Einstein’s Equivalence | JoVE K12

physics

JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Alabama Course of Study Science

9-12

Earth and Space Science

Earth's Place in the Universe

9-12.ESS.1.3

Florida Department of Education

High School

SC.912.E.5

SC.912.E.5.5

SC.912.E.5.10

Georgia Standards of Excellence

Astronomy

SAST4

SAST4.1

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PH.9.a

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PH.9.b

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PH.9.d

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The student will investigate and understand that extremely large and extremely small quantities are not necessarily described by the same laws as those studied in Newtonian physics. Topics, such as these listed, may be included. solid state physics;

PH.9.e

The student will investigate and understand that extremely large and extremely small quantities are not necessarily described by the same laws as those studied in Newtonian physics. Topics, such as these listed, may be included.

Weightlessness and Einstein’s Equivalence

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