Do Astronauts Feel the Speed of the ISS?

The question of whether astronauts feel the speed of the International Space Station (ISS) is more complex than it might seem at first glance. According to Henry Tom, the answer is a qualified YES; however, this perspective requires some understanding of physics and human perception.

The Role of Perception

The person asking this question may be considered juvenile if they have not yet had the life experiences to understand the nuances of motion and perception. Our bodies have several mechanisms to sense motion, and these can be influenced by various factors.

Basic Sensory Perception of Motion

Our bodies have sensory organs that allow us to perceive motion. What we see can sometimes play tricks on our minds. The eustachian tubes in our ears, which help in maintaining pressure balance, can also trigger reflex systems. These mechanisms help us perceive motion, but they can be easily influenced by external factors. For example, if we are in a stationary car next to some big trucks, we might perceive the trucks as moving, even if they are not, due to the contrast with our stationary position.

Astronauts and Sensory Perception

Astronauts on the ISS face similar challenges. They can perceive the Earth or the moon moving in their vision, but this is not due to an actual change in their speed. Instead, it is a result of their frame of reference. In the same way, a juvenile mind might misinterpret stillness as motion, astronauts can perceive motion without a sensation of speed if the ISS is orbiting at a near-constant velocity. Thus, the answer to the question is not a simple yes or no but depends on the perception and the context.

Perception without a Reference

Henry Tom's statement highlights that there is no way to feel speed without a reference point. This is true not just for astronauts but for anyone in a vehicle or space station. Cars, airplanes, and spacecraft all travel at high speeds, often much greater than what we might experience on the ground, but their occupants do not feel the speed.

Forces and Acceleration

The sensation that we do feel in vehicles, whether a car, airplane, or spacecraft, is related to acceleration, not speed. Acceleration is the change in speed, and when forces are applied to an object, we feel them. For example, when you press on the gas pedal in a car, you feel the force of the seat pushing against your back as the car accelerates. Similarly, when you slam on the brakes, you feel the force of deceleration.

However, when the vehicle is moving at a steady speed, such as when an airplane is cruising or the ISS is orbiting the Earth, there is no sensation of speed. This is because there are no changes in velocity in the absence of external forces or turbulence. Consequently, astronauts in the ISS do not feel the speed at which the spacecraft is traveling. They experience forces only when the ISS encounters turbulence or undergoes changes in velocity due to engine firings.

The Orbit and Continuous Motion

The ISS orbits the Earth every 90 minutes, which means it is constantly moving at an incredibly high speed—approximately 28,000 kilometers per hour (17,000 miles per hour). However, the astronauts do not feel this speed because the ISS constantly maintains a stable orbit. There are no bumps in the road nor turbulent air to cause the sensation of acceleration.

Sticking Your Head Out the Window

One common analogy is that if astronauts were to roll down a window and stick their heads out, they would feel the wind. However, this does not apply to bald astronauts, further emphasizing the need for a reference point to feel speed.

Conclusion

In summary, astronauts on the ISS do not feel the speed of the spacecraft in the same way that passengers in a car or an airplane do. Their perception of motion is influenced by the absence of changes in velocity and the constant orbit of the ISS. The sensation of speed, when it happens, is due to acceleration and forces rather than the speed itself.