Hey! I got a question! Why do people talk of the "vacuum" of space? I meen there must be something in between the gaps. is it because it a lower pressure than found on Earth? because if it was a true vacuum then shorely it would suck away the earths atmosphere, right? If i can sit on this plannet and suck thick ice creem upwards through a straw, totally defeating gravity with a partial vacuum created in my mouth, then how does the thin gasses of our upper atmosphere, in the weekest reaches of gravity manage to stay clumped in a nice neet ball? Total vacuum? Interested to hear some views on this.
Space is not empty, but it has no atmosphere either. We have an atmosphere because of gravity. We have a strong gravity because of the density of the earth's core material, which is basically a large iron ball hundreds of miles in diameter. With sucking on a straw, you're not defeating gravity, you're using a stronger force to overcome it. For the gases in our atmosphere, the stronger force is gravity. Gases have little gravity themselves and are no match for a planet-sized iron ball. x
The milk shake is pushed up the straw by the weight of the atmosphere above the cup. One way to look at it is the "sucking" of interplanetary vacum is balanced by the force of gravity, so our air stays put.
Firstly I disagree, there is a tug of war between the weight of the ice cream and its own pressure, the vacuum allows room (lack of pressure) for gravety to be "defeated", the goal of every rocket scientist. Also the gravety generated by gas is irrelavent, the sheer fact that gas particals have little mass/gravety only adds to my point that they arnt heavy and and therefore should repell against each other and fill the void where there is no atmosphere.
You explained that well, while reading it I think I had a brain wave. It all makes sense all of a sudden, I suppose if there is a total vacuum then any particals that wander into it will not have anything to bounce off, since this is essentially what pressure is the gravety will pull it back. WOW! That was bugging me but I feel like its obvious now.
It still goes back to gravity and the big iron ball. What "creates" the weight of the ice cream? Or the gas particles? The individual atoms which compose either are still under the influence of a gravitational field stronger than their own. This gives them weight. When you talk in terms of vacuum, you have to take into account gravitational fields exerted by large objects upon smaller ones. The vacuum you're talking about is just an absence of gases. Simple matter. To be totally free of any kind of gravitational field is the only true vacuum. You can be a trillion miles out in deep space, and there is something somewhere tugging on you. Gravity is what fills the spaces, and ALL physical matter dances to it's tune. x
...and the hard vacuum of space is still more complete than what we create here on earth. there isn't a total nothing out there, but there is a whole lot of it. and it's getting thinner (entropy)
It the gravitational attraction at the surface of the planet, which depends on both the mass and the volume of the planet. That can be expressed in terms of mass and volume Or mass and density Or density and Volume. But two of the three quantities, mass, volume, or density are needed to calculate the force of gravity at the surface of a planet.
Ahh I thought mass was density. I am not a scientist and have not studied mathematics I take an interest in such things but will have to look at what those terms mean to continue - I will teach myself what mass, volume, density are.
Mass - the amount of stuff in an object. In a constant gravitational field, it's equivilant to weight. Volume - the amout of space that an object occupies. Density - the mass of an object divided by its volume. Consider a kilo of feathers and a kilo of butter. The feathers take up much more room and therefore have a bigger density. A liter of lithium and a liter of gold have the same volume, but since gold is denser, the gold weighs more. If you know two of these three quanities, calculating the third is easy. If you only know one of those quantities, the other two are unknown and one of them needs to be measured to find the third. (A not uncommon situation in physics.)
mass and weight are only the same in constant gravity (which doesn't even exist across the face of earth) mass is constant, as gravity varies, so does weight, that's because mass is measured relatively, and weight is measured absolutely, this is also important.
mas is measured in relation to a set other mass, on a balance so a gram is balanced against a gram. the values are absolute, the amount of a material that, based on density and jazz that makes it up is absolute, but the amount of effort required to move it then becomes relative.
Gravity is only mass and distance. Nothing else. No volume, no density, no weight. The weight of an object is related to the mass it has and the force of gravity on it, and I'm sorry to tell Dave_techie that the force of gravity is the same everywhere on the face of this planet. From the lowest point of land to the highest point of land is only a mere 5-6 miles and that only would change the force of gravity in such a miniscule amount that it would take extremely sensitive equipment to detect it.
No it wouldn't, build a clock, it will detect the variation of gravity at different altitudes reasonably quickly, altitude error, it's one of the reasons clocks (old clocks) are calibrated for where they will be used. sophisticated equipment my ass, when did a pendulum become a piece of complicated, or sophisticated equipment?
^hey dave techie, nice picture, i just got that wallpaper off gnome-looks.com :-D naughty tux! hey mike i think the butter is more dense then the feather, think you had a typo. One of the coolest theories i have heard about what makes up empty (or otherwise i guess) space, is that it is particle of matter or energy constantly colliding with its inverse antimatter particle, and the resulting explosions are what gives reality its spacial dimension. Hope i got that as correct as i can. To the point of gravity. it is not the same everywhere on earth, the change isn't huge, but it certainly is not insignificant. It can act kinda funny, even in 'normal' situations and not just comparing the weight of your friend in the Mariana's trench to yours on Everest. Check out the Laurentide Ice Sheet & Canada's 'missing' gravity: http://science.howstuffworks.com/missing-gravity.htm
