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Related Concept Videos

Weightlessness01:01

Weightlessness

When an object is dropped, it accelerates toward the center of the Earth. If the net external force on the object is its weight, it is said to be in free fall; that is, the only force acting on the object is gravity. Galileo was instrumental in showing that, in the absence of air resistance, all objects fall with the same acceleration g. However, when objects on the Earth fall downward, they are never truly in free fall, because there is always some upward resistance force from the air acting...
Acceleration due to Gravity on Earth01:21

Acceleration due to Gravity on Earth

According to Newton's law of gravitation, the gravitational force on a body is proportional to its mass. According to Newton's second law of motion, the acceleration produced by an external force is inversely proportional to the force. Hence, the acceleration of an object under an external force of gravitation is independent of its mass.
The acceleration of an object close to the Earth, because of the Earth's gravitational pull, is called the acceleration due to gravity. It is always directed...
Variation in Acceleration due to Gravity near the Earth's Surface01:20

Variation in Acceleration due to Gravity near the Earth's Surface

An object's apparent weight is its weight measured by a spring balance at its location. It is different from its true weight, the force with which the Earth pulls it, because of the Earth's rotation. Mathematically, an object's apparent weight equals its true weight minus the centripetal force that keeps it in a circular motion along with the Earth's surface every 24 hours.
The difference between the true and apparent weights is proportional to the square of the Earth's angular speed. Since the...
Principle of Equivalence01:18

Principle of Equivalence

According to Albert Einstein (1897-1955), free-falling and feeling weightless are intrinsically linked. If a person were in free-fall under gravity, for example, diving towards the Earth from an airplane, they would feel completely weightless. Similarly, a person descending in a lift may feel partially weightless. Broadly speaking, it is assumed that an object in a uniform gravitational field and an object undergoing constant acceleration in the absence of gravity are under the same...
Acceleration due to Gravity on Other Planets01:24

Acceleration due to Gravity on Other Planets

The gravitational acceleration of an object near the Earth's surface is called the acceleration due to gravity. It can be measured by conducting simple experiments on Earth. However, such an experiment is impossible to conduct on the surface of other planets.
Astronomical observations are thus used to measure the acceleration due to gravity on other planets. This can be determined by observing the effect of a planet's gravity on objects close to it. The crucial factor that helps in this...
Free-falling Bodies: Introduction01:07

Free-falling Bodies: Introduction

All objects, neglecting air resistance, fall with the same acceleration towards the Earth's center due to the force exerted by the Earth's gravity. This experimentally determined fact is unexpected because we are so accustomed to the effects of air resistance and friction that we expect light objects to fall slower than heavier ones. People believed that a heavier object had a greater acceleration when falling until Galileo Galilei (1564–1642) proved otherwise. We now know this is not the case.

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Related Experiment Video

Updated: May 10, 2026

Reduced-gravity Environment Hardware Demonstrations of a Prototype Miniaturized Flow Cytometer and Companion Microfluidic Mixing Technology
13:59

Reduced-gravity Environment Hardware Demonstrations of a Prototype Miniaturized Flow Cytometer and Companion Microfluidic Mixing Technology

Published on: November 13, 2014

Microgravity.

G Kim Prisk1

  • 1Departments of Medicine and Radiology, University of California, San Diego, USA. kprisk@ucsd.edu

Comprehensive Physiology
|June 6, 2013
PubMed
Summary
This summary is machine-generated.

Microgravity alters respiratory mechanics, primarily affecting abdominal compliance and reducing residual lung volume. Obstructive sleep apnea events are nearly eliminated during sleep in microgravity.

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Area of Science:

  • Physiology
  • Aerospace Medicine
  • Respiratory Mechanics

Background:

  • Gravity significantly influences respiratory system mechanics.
  • Previous models predicted microgravity's effects on lung volumes.

Purpose of the Study:

  • To investigate the impact of sustained microgravity on respiratory mechanics.
  • To analyze changes in lung volumes and expiratory flows in microgravity.
  • To assess the effect of microgravity on obstructive sleep apnea.

Main Methods:

  • Measurements of functional residual capacity, vital capacity, and residual volume in microgravity.
  • Assessment of abdominal compliance and rib cage mechanics.
  • Analysis of expiratory flows after intrathoracic blood volume normalization.
  • Monitoring of sleep in microgravity to evaluate obstructive sleep apnea.

Main Results:

  • Functional residual capacity in microgravity is intermediate between standing and supine postures in 1G.
  • Changes in functional residual capacity are mainly due to altered abdominal compliance.
  • Vital capacity remains unchanged post-correction of initial thoracic blood volume shifts.
  • Residual volume decreases in microgravity due to more uniform alveolar size.
  • Expiratory flows are unaffected by microgravity after normalization of intrathoracic blood volume.
  • Obstructive sleep apnea events are almost completely abolished during sleep in microgravity.

Conclusions:

  • Microgravity significantly alters respiratory mechanics, particularly abdominal compliance and lung volumes.
  • The respiratory system adapts to microgravity, with potential benefits for sleep-disordered breathing.
  • Understanding these adaptations is crucial for long-duration spaceflight and potential therapeutic applications.