Weightlessness and Microgravity — Reading Comprehension

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Grades

Standards

MS-PS2-4
MS-ESS1-2

About This Reader

This science reading passage for middle school students explores the phenomenon of weightlessness and microgravity. Aligned to NGSS standards MS-PS2-4 and MS-ESS1-2, it explains why astronauts on the International Space Station (ISS) feel weightless, dispelling the misconception that there is no gravity in orbit. Students will learn how the ISS and its occupants are in a state of continuous freefall, resulting in microgravity conditions. The passage discusses the effects of microgravity on the human body, including fluid shifts, muscle and bone weakening, and balance issues, as well as the health challenges and benefits for scientific research. It integrates key concepts from physics and life sciences and encourages scientific thinking about forces and motion. The content is audio integrated for accessibility and includes activities such as quizzes, writing prompts, and graphic organizers to support learning.

CONTENT PREVIEW

"Astronauts in weightlessness" by NASA / Wikimedia Commons (Public domain).

Weightlessness is a condition commonly experienced by astronauts aboard the International Space Station (ISS), and it plays a crucial role in advancing our understanding of science and human health. Many people believe astronauts float because there is no gravity in space. However, this is a misconception. In fact, gravity at the ISS is nearly as strong as on Earth’s surface—about 90% as strong. The real explanation for weightlessness lies in the nature of orbit and the concept of freefall.

How Weightlessness Happens: The Science of Freefall

Objects in orbit, including the ISS and its crew, are constantly falling toward Earth due to gravity. However, they are also moving forward at a high speed—over 28,000 kilometers per hour. This combination causes the ISS to continuously "miss" the Earth as it falls, creating a state of perpetual freefall. Because the astronauts and everything inside the ISS are falling at the same rate, there are no internal support forces acting on their bodies. This results in the sensation of weightlessness. The correct scientific term for this state is microgravity, meaning that the effects of gravity are greatly reduced but not entirely absent. Microgravity allows scientists to study physical and biological processes in ways impossible on Earth.

Effects on the Human Body and Scientific Research

Microgravity produces noticeable changes in the human body. Without Earth's gravity pulling fluids down, bodily fluids shift toward the head, causing puffy faces and nasal congestion. Over time, muscles and bones weaken because they are not used as much, leading to health challenges for astronauts. The vestibular system—responsible for balance and spatial orientation—can become confused, causing motion sickness or balance problems. Despite these difficulties, microgravity provides a unique environment for scientific experiments, such as studying the growth of protein crystals or observing how flames behave. Some of these experiments can lead to medical and technological advances on Earth.

Training, Misconceptions, and Broader Implications

Astronauts must prepare for microgravity before traveling to space. They train in special aircraft, sometimes called the "vomit comet," which flies in parabolic paths to simulate weightlessness for short periods. Understanding microgravity helps scientists design better spacecraft and develop ways to keep astronauts healthy during long missions. It also challenges us to rethink our basic ideas about force, motion, and gravity. Recognizing that weightlessness is not the absence of gravity but a result of continuous freefall is essential for understanding how orbiting systems work.

Studying weightlessness and microgravity not only helps us plan future space missions but also deepens our knowledge of physics and the human body. These insights can lead to innovations for both space exploration and life on Earth.

Interesting Fact:
Even though astronauts appear to float freely, they are actually falling around Earth at thousands of kilometers per hour—never truly escaping gravity!

Why do astronauts on the ISS feel weightless?

Because they are in continuous freefall around Earth.Because there is no gravity in space.Because the ISS has no mass.Because they are farther from the Sun.

What is the scientific term for the 'weightless' condition experienced in orbit?

SupergravityAnti-gravityMicrogravityMagnetism

What causes the ISS to stay in orbit around Earth?

It is being pushed by the Sun.It moves forward fast enough to keep missing Earth as it falls.There is no gravity in space.It is attached by a cable to the Moon.

Which of the following is an effect of microgravity on the human body?

Bones and muscles become stronger.Fluids shift toward the head.Gravity increases inside the ISS.Astronauts can breathe underwater.

What does the term 'parabolic path' mean in the context of astronaut training?

A straight flight path to space.A curved flight that creates short periods of weightlessness.A path that circles the Moon.A path underwater.

In the passage, what does 'support force' refer to?

The force from the rocket engines.The force that pushes up against your body, like the floor on your feet.The force of wind in the ISS.The force of magnets in space.

Why is microgravity useful for scientific experiments?

It makes experiments easier to see on Earth.It allows scientists to study processes that can't be observed under normal gravity.It creates stronger gravity for better results.It helps astronauts grow taller.

True or False: Gravity at the ISS is only about 10% as strong as at Earth's surface.

TrueFalse

True or False: The vestibular system is responsible for balance and spatial orientation.

TrueFalse

Which of the following is a misconception addressed in the passage?

Astronauts on the ISS float because there is zero gravity.Microgravity allows for unique experiments.Astronauts train on special aircraft.Gravity affects fluids in the human body.