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Added comments about the word "weightless."
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user9803
user9803

First of all, the word "gravity" connotes a material substance that can somehow be transferred from body to body and lack of this material causes a body to NOT gravitationally attract other bodies. After 20 years of teaching undergraduate physics, I have direct evidence of this misconception. The fix is to NOT use the word "gravity" and to replace it with "gravitational attraction." Second, gravitational attraction is required for an artificial satellite to maintain anything other than a linear, uniform speed trajectory. Third, objects don't "float" as that word (words are very important here, by the way) connotes support by some physical influence. Water holds boats up. Air holds aircraft up. Air hold balloons up. Nothing hold the ISS or its contents "up" as the entire system (craft + astronauts) is being pulled toward Earth's center. Fourth, the correct term that describes the ISS and astronaut's state of motion is "free fall." There's nothing more to it than that. The astronauts are free falling toward's Earth's center, but so is the ISS and its floor which would otherwise support them. The astronauts are NOT floating. ISS is NOT floating. Things don't float.

EDIT: There's no such condition as "weightless" either, because the term "weight" is most properly defined as the gravitational attraction between Earth and an object, and that can never be zero. OF course, it can be very, very, very small, but it cannot be zero.

You have no idea how badly words like "gravity" and "weightless" and "float" harm students' understanding of the simplest physics concepts.

First of all, the word "gravity" connotes a material substance that can somehow be transferred from body to body and lack of this material causes a body to NOT gravitationally attract other bodies. After 20 years of teaching undergraduate physics, I have direct evidence of this misconception. The fix is to NOT use the word "gravity" and to replace it with "gravitational attraction." Second, gravitational attraction is required for an artificial satellite to maintain anything other than a linear, uniform speed trajectory. Third, objects don't "float" as that word (words are very important here, by the way) connotes support by some physical influence. Water holds boats up. Air holds aircraft up. Air hold balloons up. Nothing hold the ISS or its contents "up" as the entire system (craft + astronauts) is being pulled toward Earth's center. Fourth, the correct term that describes the ISS and astronaut's state of motion is "free fall." There's nothing more to it than that. The astronauts are free falling toward's Earth's center, but so is the ISS and its floor which would otherwise support them. The astronauts are NOT floating. ISS is NOT floating. Things don't float.

First of all, the word "gravity" connotes a material substance that can somehow be transferred from body to body and lack of this material causes a body to NOT gravitationally attract other bodies. After 20 years of teaching undergraduate physics, I have direct evidence of this misconception. The fix is to NOT use the word "gravity" and to replace it with "gravitational attraction." Second, gravitational attraction is required for an artificial satellite to maintain anything other than a linear, uniform speed trajectory. Third, objects don't "float" as that word (words are very important here, by the way) connotes support by some physical influence. Water holds boats up. Air holds aircraft up. Air hold balloons up. Nothing hold the ISS or its contents "up" as the entire system (craft + astronauts) is being pulled toward Earth's center. Fourth, the correct term that describes the ISS and astronaut's state of motion is "free fall." There's nothing more to it than that. The astronauts are free falling toward's Earth's center, but so is the ISS and its floor which would otherwise support them. The astronauts are NOT floating. ISS is NOT floating. Things don't float.

EDIT: There's no such condition as "weightless" either, because the term "weight" is most properly defined as the gravitational attraction between Earth and an object, and that can never be zero. OF course, it can be very, very, very small, but it cannot be zero.

You have no idea how badly words like "gravity" and "weightless" and "float" harm students' understanding of the simplest physics concepts.

Source Link
user9803
user9803

First of all, the word "gravity" connotes a material substance that can somehow be transferred from body to body and lack of this material causes a body to NOT gravitationally attract other bodies. After 20 years of teaching undergraduate physics, I have direct evidence of this misconception. The fix is to NOT use the word "gravity" and to replace it with "gravitational attraction." Second, gravitational attraction is required for an artificial satellite to maintain anything other than a linear, uniform speed trajectory. Third, objects don't "float" as that word (words are very important here, by the way) connotes support by some physical influence. Water holds boats up. Air holds aircraft up. Air hold balloons up. Nothing hold the ISS or its contents "up" as the entire system (craft + astronauts) is being pulled toward Earth's center. Fourth, the correct term that describes the ISS and astronaut's state of motion is "free fall." There's nothing more to it than that. The astronauts are free falling toward's Earth's center, but so is the ISS and its floor which would otherwise support them. The astronauts are NOT floating. ISS is NOT floating. Things don't float.