when i look closely at my hand, I see very small dust particles being drawn to it, is this gravity from my hand? when you stand next to a large building or cliff you sort of feel it, is it because those things have gravity?
2007-12-30 13:00:49 · 12 answers · asked by Anonymous in Science & Mathematics ➔ Physics
No. The gravitational force your hand exerts is far too weak to be observable by your own eyes. If dust particles are being attracted to your hand, it's probably because of static.
The feeling you get when standing on the edge of a cliff (as I assume you mean by "next to," as I don't know why you'd feel anything at all when simply standing next to something) is probably vertigo or something similar.
2007-12-30 13:08:12 · answer #1 · answered by Anonymous · 5⤊ 1⤋
No. Dust attracted to your hand is most likely the result of static electric change on your body attracting the dust.
The force of gravity is F(g) = G * m1 * m2 / r². For a 1kg hand and a 0.1g spec of dust at 0.1m the force of gravity between the two would be:
F(g) = 6.67x10^-11 * 1 * 0.0001 / (0.01)² = 6.67x10^-12 N.
The acceleration caused by that force would be:
a = F(g)/m = 6.67x10^-12 N / 0.0001kg = 6.67x10^-8 m/s².
Meanwhile the Earth is exerting a force and accelleration about one million times stronger (9.8m/s²) and even the moon is pulling at the dust a thousand or so times stronger (about 3.4x10^-5 m/s²).
Even in a vaccum, the dust is going for the Earth, the moon, a nearly lake, etc. thousands or millions of times faster than towards your hand. In the atmosphere, the force of gravity produced by your hand it too weak to move air molecules out the way.
Dust is likely attracted to your hand by the electromagnetic force. Tiny static electric changes build up in your body and in the dust particles and these (at close distances) are much stronger than the force of gravity and are sufficient to attract dust particles. You will notice that if you rub your hair or drag your feet across the carpet you can even pick up small shards of paper. However, step into a bath tub (full of water) and the shards of paper are no longer attracted to your hand.
Buildings are not massive enough to produce noticable gravity changes which humans could detect. Even local density changes in the ground, oceans, large mountains, high flying aircraft, nor the distance differences between the poles and equator cause more than a tiny fraction of a percentage difference in local gravity conditions on Earth. Only extremely sensitive instruments can detect such small differences.
2007-12-30 21:53:01 · answer #2 · answered by bw022 7 · 0⤊ 0⤋
The dust thing, no - see other answers.
The wall thing, no, but it is something almost as interesting. Blind people use the feeling all the time to help navigate between buildings and to keep from walking into walls. My wife is a blind person and with her I have learned to observe this sensing. It is a combination of changing air pressure from moving air, changes in sounds, both echoing off the wall and being blocked by the building or cliff, and changes in heat from radiation, again the heat radiating from the building/cliff and heat being cut off from the sun (shadow) It's kind neat. Anyone can do it with a little attention, it is not a "supersense" developed by the blind.
2007-12-30 22:31:16 · answer #3 · answered by Mike1942f 7 · 1⤊ 0⤋
Believe it or not, the gravitational constant G, was initially measured with an apparatus in which two spherical balls were brought close enough together such that the gravity due to the two pulled them together.
The dust is probably attracted to your hand more so by a slight electrostatic charge or van der waal forces though.
2007-12-30 22:28:53 · answer #4 · answered by minuteblue 6 · 0⤊ 0⤋
Gravity is the weakest of all natural forces.
If anything, it would be the static from your body, or from the dust.
Were you wearing shoes? Socks? In fact, dust is so tiny, I'm sure the most insignificant charge could draw force from a minuscule distance.
2007-12-30 22:43:09 · answer #5 · answered by michael_p87 2 · 0⤊ 0⤋
NO, it is static attraction, i.e. electromagnetic forces at work. Gravity is so weak on our everyday scale, that it is very hard to understand sometimes.
Force of electromagnetic attraction is 1,000,000,000,000,000,000,000,000,000,000,000,000,000 times stronger than gravity at the same distance.
2007-12-30 21:38:20 · answer #6 · answered by Charles M 6 · 0⤊ 0⤋
I think the cells and adoms on your hand are pulling the dust to your hand. So yes, that's gravity.
Oh, and interesting question.
2007-12-31 00:07:10 · answer #7 · answered by HarryPotterfan12 1 · 0⤊ 0⤋
No. Gravity is space displaced by matter, trying to return to its original shape. Space, therefore, is not 'nothing'...
2007-12-31 00:02:36 · answer #8 · answered by Thomas E 7 · 0⤊ 0⤋
dust particles are attracted easily to charge materials, what you saw could be an effect of static charges.
2007-12-30 21:09:19 · answer #9 · answered by + cruz + 2 · 1⤊ 1⤋
i doubt it is gravity from your hand...it is the earth's gravity or the wind pointing at a certain direction
2007-12-30 21:09:46 · answer #10 · answered by Einstein Freak 2 · 0⤊ 1⤋