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  1. #1 Question 
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    I could probably spend a little time and figure this out on the web but thought I might make someone get a pretty good laugh. Please excuse my ignorance for I only have a 6th grade education and a GED.
    So here is my question. You have a 10 pound box. Inside that 10 pound box you have a 200 pound piece of steel. So now you have a box that weighs 210 pounds. You suck the atmosphere out of the box creating a vacuum. The steel is now weightless. Is the box still 210 pounds?


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  3. #2  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by anaylor01 View Post
    You suck the atmosphere out of the box creating a vacuum. The steel is now weightless.
    Whoah! Hold on there... A vacuum doesn't make things weightless. Look at the astronauts on the moon (or even the Moon orbiting the Earth).

    (But it seems to be a common misconception, so don't feel too bad!)

    Is the box still 210 pounds?
    It will be slightly less because you have removed the weight of the air that was in it.


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    Forum Radioactive Isotope zinjanthropos's Avatar
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    Is the box still 210 pounds?
    Whoa......think about the question........No, the box is still 10 lbs. Whatever the stuff inside the box weighs is irrelevant.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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    Very good zinjanthropos. I meant does the box along with the contents still weigh 210 pounds? So when the astronauts train. They have a facility that sucks the atmosphere out and they become weightless. So you have the weight of the chamber plus the weight of the astronauts. So when the astronauts are in this chamber does the chamber weigh the same as it did before after the atmosphere is sucked out????
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    Genius Duck Moderator Dywyddyr's Avatar
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    Quote Originally Posted by anaylor01 View Post
    So when the astronauts train. They have a facility that sucks the atmosphere out and they become weightless.
    This is incorrect. As Strange pointed out, vacuum doesn't make things weightless.

    So you have the weight of the chamber plus the weight of the astronauts. So when the astronauts are in this chamber does the chamber weigh the same as it did before after the atmosphere is sucked out????
    As was noted earlier: the weight difference will that of the removed air only.
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    Maybe I am not explaining myself. There is a chamber that astronauts use to train in weightlessness. So WHATEVER they do to make the chamber weightless. Does the chamber with the astronauts weight weigh the same with the astronauts in it before they do WHATEVER they do to make it weightless as it does after they make it weightless??? And I guess I have another question. Isn't space a vacuum? Or is it just without atmosphere?
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    Quote Originally Posted by anaylor01 View Post
    Maybe I am not explaining myself. There is a chamber that astronauts use to train in weightlessness. So WHATEVER they do to make the chamber weightless. Does the chamber with the astronauts weight weigh the same with the astronauts in it before they do WHATEVER they do to make it weightless as it does after they make it weightless??? And I guess I have another question. Isn't space a vacuum? Or is it just without atmosphere?
    Let's try to unmuddle your several muddles:

    1) There is no magic chamber that cancels gravity. None.

    Astronauts sometimes train in water, whose buoyancy helps crudely emulate some aspects of weightlessness.

    For brief periods of time, you may confer weightlessness in an aircraft by diving (google for "Vomit Comet"). That's how the film Apollo 13 achieved its terrific effects. But because you can't dive forever, the scenes had to be shot in 5-minute (or thereabouts) takes.

    Taking the air out of something just takes the air out of something. Air is not responsible for gravity, so its removal does not remove gravity. Gravity, in Newtonian mechanics, is the result of mass acting on other mass. Here on earth, gravity is mainly due to that big ball we live on. It pulls on you, the box, the moon...you can't get rid of it. No magic chamber with a switch labeled "gravity on/off".

    2) The absence of an atmosphere IS a vacuum.
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    Thanks for all the replies. Maybe I am mistaken but I thought in the movie Armageddon they had a chamber that simulated weightlessness. I know there is also a scene where they are underwater.
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    The Zero Gravity Research Facility

    This is the ultimate zero gravity experience. Designed by NASA, this facility performs drop tests in a vacuum chamber to research the reactions of different components in a zero gravity atmosphere. Getting a shot requires a little more than purchasing a ticket, but if you have a plug at NASA this is the most official way to experience life without gravity—completely weightless.
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  11. #10  
    Genius Duck Moderator Dywyddyr's Avatar
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    Quote Originally Posted by anaylor01 View Post
    The Zero Gravity Research Facility
    This is the ultimate zero gravity experience. Designed by NASA, this facility performs drop tests in a vacuum chamber to research the reactions of different components in a zero gravity atmosphere. Getting a shot requires a little more than purchasing a ticket, but if you have a plug at NASA this is the most official way to experience life without gravity—completely weightless.
    https://www1.grc.nasa.gov/facilities/zero-g/
    And it goes on to state, specifically: "The Zero-G facility provides researchers with a near weightless or microgravity environment for a duration of 5.18 seconds. Microgravity, which is the condition of relative near weightlessness, can only be achieved on Earth by putting an object in a state of free fall." The lack of atmosphere is merely to remove drag on the falling object - also noted on the page: "Evacuating the chamber to this pressure reduces the aerodynamic drag on the freely falling experiment vehicle...".
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    Ok. I see what I just posted is not really zero gravity. So the ONLY way to actually get zero gravity is in space? Why can't the conditions of space be reproduced? I know something about gravity. But I thought space was just a vacuum and the absence of atmosphere and that was what caused anti gravity.
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    Quote Originally Posted by anaylor01 View Post
    Ok. I see what I just posted is not really zero gravity. So the ONLY way to actually get zero gravity is in space? Why can't the conditions of space be reproduced? I know something about gravity. But I thought space was just a vacuum and the absence of atmosphere and that was what caused anti gravity.
    I don't know if you are a troll or just a careless reader. But you are rude.

    The answer has been given to you, several times. I explained what does and does not cause gravity. And yet you continue.

    Gravity is from MASS. No mass == no gravity.

    Vacuum has nothing to do with gravity.

    Got it?

    Please read more carefully if you are not a troll.

    And if you are a troll, that will become evident in due course.
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    No need to be a douche.
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    And maybe you should read. I said from the beginning that I am not educated. Maybe I am not understanding. You say NO MASS = No gravity. But their are objects in space that have mass and their is no gravity. What am I missing? And please don't be rude about it.
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    Quote Originally Posted by anaylor01 View Post
    And maybe you should read. I said from the beginning that I am not educated. Maybe I am not understanding. You say NO MASS = No gravity. But their are objects in space that have mass and their is no gravity. What am I missing? And please don't be rude about it.
    I'm not intending to be rude or a douche. But I do insist that you take responsibility for readiing the answers that people here have gone to the trouble of providing. Your educational background has nothing to do with a lack of courtesy in acknowledging the information given to you, so you may not use that as an excuse. So don't call out others for responding sharply for laziness on your part.

    Now back to your questions. Mass causes gravity, yes. But its pull weakens as the distance to the mass increases. If one doubles the distance, the force weakens by a factor of four (it's known as the inverse-square law). The pull never goes to zero, but it drops to as close to zero as you would like as long as you go sufficiently far from it.

    Also, if you are situated precisely in the middle between two equal masses you will feel no net gravity at that spot (but will if you move away from that spot).

    The astronauts who went to the moon felt the pull of the earth and moon balance at only one point, nearer to the moon (because of its smaller mass) than to the earth. Then why did they appear weightless elsewhere during the flight? Somewhat paradoxically, another way to experience zero-g is to go into free-fall. That's how the "Vomit Comet" works, and it's also why astronauts in orbit feel weightless, despite the big earth pulling on them the whole time. An object in orbit is nothing more than a mass in perpetual free-fall, with the round earth conveniently getting out of the way to allow it to do so. So there are several ways to approximate zero-g without having a zero-mass universe.
    Last edited by tk421; January 20th, 2018 at 07:59 PM.
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    Ok TK421. Don't get made at me. I am really trying to understand. I went back and reread this thread and I guess either I am not understanding or am just stupid. Let me ask this way.
    1. What does "Space" consist of? Our atmosphere is made up of oxygen, nitrogen and carbon dioxide. I thought "space" was just the absence of those gases and gravity.
    2. What is it about "space" that makes MASS weightless? The absence of gravity right?
    3. Why can't "space" be recreated on earth? I think you are saying that because of gravity there is no way to recreate "space" on earth.
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    I am sorry if I am being obtuse. I am not trying to be.
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    Quote Originally Posted by anaylor01 View Post
    Ok TK421. Don't get made at me. I am really trying to understand. I went back and reread this thread and I guess either I am not understanding or am just stupid. Let me ask this way.
    1. What does "Space" consist of? Our atmosphere is made up of oxygen, nitrogen and carbon dioxide. I thought "space" was just the absence of those gases and gravity.
    One definition for space is the largely-empty region between objects.

    2. What is it about "space" that makes MASS weightless?
    Nothing.

    The absence of gravity right?
    No, you've got things backwards again. Since mass is what is responsible for gravity, only the absence of mass can cause the absence of gravity. Again, mass is the source of gravity. The absence of gravity is a consequence. It is not a cause.

    The gravitational force exerted by a mass extends beyond the boundaries of the mass itself. That's why a dropped fall falls.

    You are much too hung up on space, for reasons that are mysterious to me. Space is not making mass do anything, so just hit the big clear button in your brain. Focus on what you have been told over and over again:

    Gravity comes from mass.

    Repeat that to yourself as many times as necessary.


    3. Why can't "space" be recreated on earth? I think you are saying that because of gravity there is no way to recreate "space" on earth.
    Define what YOU mean by "recreate".

    You can certainly make a box here on earth that doesn't contain stuff. But that doesn't make gravity go away, because you haven't made mass disappear [see why it's important to get rid of the false idea that space has some effect on gravity?]. Sure, there's no mass inside the box, but there's mass nearby (a big one, called the earth). As I said in my previous reply, the gravitational force exerted by a mass never decays to zero. It gets weaker the farther away you go, but it doesn't suddenly go to zero at some distance away from the mass. The vast distances between objects in outer space means that gravity is weakly felt over vast parts of space. But that's quite different to saying that space makes gravity go away.
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    OH F)*K. I was WAY the hell off. See I thought that the makeup of space made things weightless. So "space" has no atmosphere so there is nothing to weigh things down. Like oxygen, nitrogen and carbon dioxide is absent so there is no drag. Space is a vacuum. THe absence of things. But MASS is responsible for gravity. THe larger the MASS the greater the gravity. Hence relativity. F*&K. See I thought as soon as you left our atmosphere you were weightless. Thinking the absence of atmosphere meant no gravity. But its the further you get from earth the less gravity there is. Right???? Thanks for your help. Sorry for taking soooo long to get it.
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    Quote Originally Posted by anaylor01 View Post
    OH F)*K. I was WAY the hell off. See I thought that the makeup of space made things weightless. So "space" has no atmosphere so there is nothing to weigh things down.
    Or, more precisely, no nearby masses to exert forces.

    Like oxygen, nitrogen and carbon dioxide is absent so there is no drag. Space is a vacuum. THe absence of things. But MASS is responsible for gravity. THe larger the MASS the greater the gravity.
    Yes!

    Hence relativity.
    Er, not hence, but...

    F*&K. See I thought as soon as you left our atmosphere you were weightless. Thinking the absence of atmosphere meant no gravity. But its the further you get from earth the less gravity there is. Right???? Thanks for your help. Sorry for taking soooo long to get it.
    No problem at all. You've pretty much got it straight now, so well done! The only off note is "...hence relativity." Relativity doesn't follow from the clause preceding your "hence", but that's something perhaps for a later discussion.
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    Quote Originally Posted by anaylor01 View Post
    OH F)*K. I was WAY the hell off. See I thought that the makeup of space made things weightless. So "space" has no atmosphere so there is nothing to weigh things down. Like oxygen, nitrogen and carbon dioxide is absent so there is no drag. Space is a vacuum. THe absence of things. But MASS is responsible for gravity. THe larger the MASS the greater the gravity. Hence relativity. F*&K. See I thought as soon as you left our atmosphere you were weightless. Thinking the absence of atmosphere meant no gravity. But its the further you get from earth the less gravity there is. Right???? Thanks for your help. Sorry for taking soooo long to get it.
    I suspect part of the problem for you is the rather lazy way we all tend to speak of astronauts in space as being "weightless".

    In fact they are NOT. Not in the least. The Earth continues to pull on them, and on their spacecraft and everything in it, just as when they were on the Earth's surface (well maybe a tad less, as they are further from the Earth, but not significantly).

    What we should be saying is that objects in orbit in space are in free fall. TK421 has already mentioned this concept. Objects in free fall all accelerate towards the source of gravitational attraction at the same rate. For example if you were in a lift (elevator in N America) and someone cut the cable and brakes, it would fall freely and so would you. You would appear to be weightless relative to the chamber you are in, because it and you would be accelerating at the same rate. Your legs would not need to support your body as both legs and body would be accelerating together. So you would feel weightless. You would not be aware that you and it were actually accelerating. So it would, for those few seconds, be effectively the same for you as being truly weightless. (Of course this would all come to a horrible halt when you and the lift hit the bottom of the shaft after a few seconds.) But that is why people talk of astronauts being "weightless". An orbit is a path of continuous free fall.

    True weightlessness, that is, absence of gravitational force, would only be achieved at a distance far enough from any massive body (Earth, Sun, stars etc) for their gravity to be negligible.
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    Forum Radioactive Isotope zinjanthropos's Avatar
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    Quote Originally Posted by anaylor01 View Post
    Thanks for your help. Sorry for taking soooo long to get it.
    Don't feel bad. I've asked plenty of dumb questions and been wrong many times over the years here . These guys are good and if you're attentive, patient & polite then they'll accommodate.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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  24. #23  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by anaylor01 View Post
    OH F)*K. I was WAY the hell off. See I thought that the makeup of space made things weightless. So "space" has no atmosphere so there is nothing to weigh things down. Like oxygen, nitrogen and carbon dioxide is absent so there is no drag. Space is a vacuum. THe absence of things.
    It is almost the other way round: it is the presence of gravity that means we have an atmosphere here on Earth and makes space, relatively, a vacuum.
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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