What makes you weightless in space

The force of gravity is the only force acting upon your body. There are no external objects touching your body and exerting a force.

As such, you would experience a weightless sensation. You would weigh as much as you always do or as little yet you would not have any sensation of this weight. Weightlessness is only a sensation; it is not a reality corresponding to an individual who has lost weight. As you are free falling on a roller coaster ride or other amusement park ride , you have not momentarily lost your weight.

Weightlessness has very little to do with weight and mostly to do with the presence or absence of contact forces. If by "weight" we are referring to the force of gravitational attraction to the Earth, a free-falling person has not "lost their weight;" they are still experiencing the Earth's gravitational attraction.

Unfortunately, the confusion of a person's actual weight with one's feeling of weight is the source of many misconceptions. Technically speaking, a scale does not measure one's weight. While we use a scale to measure one's weight, the scale reading is actually a measure of the upward force applied by the scale to balance the downward force of gravity acting upon an object. When an object is in a state of equilibrium either at rest or in motion at constant speed , these two forces are balanced.

The upward force of the scale upon the person equals the downward pull of gravity also known as weight. And in this instance, the scale reading that is a measure of the upward force equals the weight of the person. However, if you stand on the scale and bounce up and down, the scale reading undergoes a rapid change. As you undergo this bouncing motion, your body is accelerating.

During the acceleration periods, the upward force of the scale is changing. And as such, the scale reading is changing.

Is your weight changing? Absolutely not! You weigh as much or as little as you always do. The scale is only measuring the external contact force that is being applied to your body.

Now consider Otis L. Evaderz who is conducting one of his famous elevator experiments. He stands on a bathroom scale and rides an elevator up and down. As he is accelerating upward and downward, the scale reading is different than when he is at rest and traveling at constant speed.

When he is accelerating, the upward and downward forces are not equal. But when he is at rest or moving at constant speed, the opposing forces balance each other. Knowing that the scale reading is a measure of the upward normal force of the scale upon his body, its value could be predicted for various stages of motion.

For instance, the value of the normal force F norm on Otis's kg body could be predicted if the acceleration is known. This prediction can be made by simply applying Newton's second law as discussed in Unit 2. As an illustration of the use of Newton's second law to determine the varying contact forces on an elevator ride, consider the following diagram. In the diagram, Otis's kg is traveling with constant speed A , accelerating upward B , accelerating downward C , and free falling D after the elevator cable snaps.

In each of these cases, the upward contact force F norm can be determined using a free-body diagram and Newton's second law. The interaction of the two forces - the upward normal force and the downward force of gravity - can be thought of as a tug-of-war. The net force acting upon the person indicates who wins the tug-of-war the up force or the down force and by how much. A net force of N, up indicates that the upward force "wins" by an amount equal to N.

The normal force is greater than the force of gravity when there is an upward acceleration B , less than the force of gravity when there is a downward acceleration C and D , and equal to the force of gravity when there is no acceleration A. Since it is the normal force that provides a sensation of one's weight, the elevator rider would feel his normal weight in case A, more than his normal weight in case B, and less than his normal weight in case C.

In case D, the elevator rider would feel absolutely weightless; without an external contact force, he would have no sensation of his weight. In all four cases, the elevator rider weighs the same amount - N. In this case, the acceleration of the elevator will be How much would the floor have to push up on the person to accelerate down at It wouldn't have to push at all.

The force the floor exerts on you would be zero. How would you feel? You would feel scared - I mean you are in an elevator with the cable cut.

How else do you think you would feel? Well, maybe you could be scared AND hungry if you were late for lunch or something. Oh, you would feel weightless. Could this really happen? In fact, some people even pay to do this. Check out this ride, Superman:. The basic idea is that you get in the car, it zooms up the vertical part of the track. During both the going up and going down parts fo the motion, the acceleration is Let me summarize so far:.

Oh, there is another great example of this weightlessness on Earth. The vomit comet. Yes, it's real. Basically, it is a plane that flies in a manner that it has a downward acceleration the same as a free falling object. Just like the falling elevator except it doesn't hit the ground. One more cool thing about the vomit comet. In the movie Apollo 13, the weightless scenes were filmed inside the vomit comet.

This way, it wouldn't only look weightless, it would BE weightless. Of course, this means that they had to shoot scenes like 30 seconds at a time. But is it accelerating? It is accelerating because the Earth pulls on it through the gravitational force. Even though it is moving in a circle, it is still accelerating.

You could say the Space Shuttle is indeed falling since its motion is determined by the gravitational force. However, since it doesn't really get closer to the Earth during its motion it would be better to call it "in orbit". Think of this. Suppose you tie a string to a ball and swing it around your head in a near horizontal circle. Does the ball moving in a circle accelerate? If it accelerates, it must have a force in the direction of the acceleration.

For the ball, this would be the tension in the string that pulls it towards the center of the circle. For an orbiting object, the gravitational force pulls on spacecraft. Well, what if you take a giant ball and string and swing it around. Already the agency has made changes. For example, it replaced the interim Resistive Exercise Device iRED with the Advanced Resistive Exercise Device in , allowing astronauts to do weight-lifting without "maxing out" their top weight.

ARED is linked to better outcomes in bone density and muscle strength, although all conclusions in space are hard to draw in the general since since the astronaut population is fit already and extremely small. Astronauts typically have an allocated exercise period of two hours a day in space to counteract these effects; this time not only includes cardiovascular exercise and weight-lifting, but also time to change clothes and set up or take down equipment.

Despite exercise, it still takes months of rehabilitation to adjust on Earth after a typical six-month space mission. More recently, doctors have discovered eye pressure changes in orbit. NASA has tracked vision changes in astronauts that were on the space station , but nothing so serious as to cause concern. Its cause is still under investigation, although one possible culprit includes spinal fluid that stays constant in microgravity instead of the normal shifting that takes place on Earth as you lie down or stand up.

In addition to spinal fluid, a study tracked changes in both short-flight and long-flight astronauts. Some studies also point out that astronauts experience a slightly elevated level of carbon dioxide on the station because of the filtration system; that gas may also contribute to eye problems.

His twin brother and former NASA astronaut Mark who retired before Scott agreed to participate, along with Scott, in several "twin experiments" to compare Scott's health in space with that of Mark's on the ground. Preliminary results from one study released in October showed that different genes turn on or off in space. Other studies discussed earlier that year revealed subtle changes as well. For example, telomeres which slow down chromosome deterioration in Scott temporarily got longer in space.

Scott also had a slight deterioration in cognitive ability thinking speed and accuracy and bone formation, although not enough to be concerning.

Scientists who work with microgravity health experiments note that often the changes seen in orbit mimic what happens as people naturally age, although often the processes are different. Looks like we are talking at cross-purposes. You are talking about a different reference frame the spacecraft. With Earth as the reference frame, the astronaut and the spacecraft are both accelerating at 9. In which case no matter where you are anywhere in the Universe you can never be weightless and the term becomes meaningless.

This is intuitive as it allows your weight to change if, for example, you are in an accelerating lift elevator or aeroplane airplane. On the ground, the orbiter weighs about , pounds. In orbit, the shuttle is about miles above the surface of the earth. Notice: the weight is not zero.

The shuttle is not weightless in orbit. The cause of the floating would be the lack of anything to cause it to not float. I know in earth the gravity is 9.

I thought gravity was zero in vacuum space. So if you multiply your weight by zero you get ZERO. But I was wrong and you know why.. Like this: Like Loading Am I right?