Weightless Orbiting Earth?

When astronauts orbit the earth they are said to be weightless - not true!

They are just continually falling at an even rate as the orbit the earth, and so if you dive off a board in a swimming pool, you experience the same amount of "weightlessness" - if for only a short time.

Could spacesickness be not about being weightless but the stress on the body as it is continually falling?

There is no stress from falling, except for the air resistance. Also, theoretically, if you're large enough (> 50 km) you have a different gravitational pull on the differents place in your body. That would also cause a stress.

'Spacesickness' is because your body is not designed to handle weightlessness for a long time.

Originally posted by Ringwrath...Could spacesickness be not about being weightless but the stress on the body as it is continually falling?

A good article about the causes of motion sickness can be found here

Quote: "Consider, for example, "up" and "down." On Earth we always know which way is up because gravity tell us. Sensors in the inner ear, which are part of the body's vestibular system, can feel the pull of gravity. They signal the brain with information about our body's orientation.

In space, however, the vestibular system doesn't sense the familiar pull of gravity. The world can suddenly seem topsy-turvy.

Former shuttle astronaut Robert Parker recalls: "One of the questions they asked us during our first flight was, 'Close your eyes ... now, how do you determine up?'" With his eyes closed, he couldn't tell. Up and down had vanished."

Ringwrath i think your getting mixed up between weight and mass.

"Weightlessness" implies the force of gravity is cancelled out - as you said "continually falling at an even rate as the orbit the earth" - no resultant forces acting on their body

If the windows were blocked out - would the know they were orbiting the earth or just in deep space far outside the effect of any gravitational force?

When you are dealing with moving and in particular accelerating bodies you need to start considering relative mechanics and appropriate frames of reference.

Amantine - look at some of the volcanic activity on some of the moons in our solar system.

Right - weightlessness means:

centrifugal force due to orbiting + gravity force at orbital distance = 0

You can get the same thing in an airplane if you fly a parabolical flight path. At the top of the parabola you'll reach "weightlessness".

Hence, the Vomit Comet.

P.S. I achieved a few seconds of weightlessness once myself. I performed a "Daisy Duke". I was traveling down a dirt road I had never been down before TOO FAST and hit a woodbridge that ramped up at about 30 degrees and then leveled out and ramped back down to the road. The bridge was right at 40' long.

I was driving a little turd of a compact car and hit the "ramp" at about 65 mph. I came down 10' past the other side of the bridge (approx 50' airborne). Throughout that time I hovered at the top of the car.

It was a rather neat experience until I landed - on my oil pan and my top lip...

They're actually experiencing microgravity -- and there are tiny amounts of gravity that close to the Earth. You have to go quite a distance to be free of any gravity and to be truly weightless.

(yeah, yeah. I know... nitpicker!)

Check out the thread "Can Humans Survive a trip to Mars? No Way!" it deals with the body and weightlessness.

Originally posted by Valhall
You can get the same thing in an airplane if you fly a parabolical flight path. At the top of the parabola you'll reach "weightlessness".

Hence, the Vomit Comet.

I've done this twice. It's really a strange feeling. We were only weightless for about 10 seconds each time, but the adrenaline rush you get from it is really cool. You get a really wierd feeling in your stomach, and you notice that stuff is floating around. As soon as you move just a little....you're off the floor.

It was in the same type of plane as the "Vomit Comet" (KC-135R) but unfortunately it wasn't padded at all. I jammed one of my fingers on the ceiling and my butt was sore for a day afterwords. When the plane pulls out of the dive, BOOM! You hit the floor pretty fast. Luckily I had had a camcorder with me at the time so I have it recorded.

You get to do some crazy stuff when you're overseas. The plane I was on was refueling 6 F-15s doing a patrol of the No-Fly zone in Iraq. Since we were in a U.S. plane in a military controlled airspace, you can get away with loosing 10,000 feet in an airpane and no one asks why.
Yep, I'm a Gulf War I veteran. It makes me sound so old. "I remember back in Gulf War I......"

[Edited on 29-4-2004 by dbates]