Gravity

[JBR]

It's a bit like someone using a match to burn your fingers, but both of you have your hands in the flame of a blow torch. Which has the greatest impact and which pales into insignificance?

I've burnt my finger on a match before now and I can assure you it didn't pale into insignificance!

 

[Mikefromlondon]

The answer is simple, a brick is a rectangular mass and a marble is a round object, so try and fit a square peg in a round hole

well not quite!

The marble cannot be attracted to the brick because the total force of attraction between the two is millions of times lesser than than the coefficient of friction of marble to its resting surface, so the force (the gravity between the two) cannot overcome the friction of the marble, plus the wind resistance, if they were in space floating freely, under no influence of other stronger fields or other forces of attraction, or very far away from the effects of earths gravity, then the two would clump together.

And if you nudge the marble a tiny winy bit, just under its escape velocity, it would start orbiting the brick, rather stupidly, well actually in an elliptical manner, assuming the force between the two was stronger than any other from distance planets.

Force of gravity weakens inversely proportional to its distance, but never completely disappears, but for practical purposes we can say that the space lab has a very weak influence from the earth's gravity due to its distance away from earth, the earth may still exert some minute pull at it, and hence every so often most satellites and space stations need correction via small rockets, hence all satellites must carry some on board fuel for this correction, hence the amount fuel for correction is what determines a life of a satellite.

 

[Astra99]

Thinking back to my schooldays and A-level Physics, I recall Newton calculated that each and every body (not everybody!!!!) displays a interaction depending on their masses, and the distance between them. He called this the Universal Gravitational Constant. The link to the Wiki article here

http://en.wikipedia.org/wiki/Gravitational_constant

 

[Mikefromlondon]

If earth was made up of lead entirely, its mass would exceed that of the sun and it would suck the sun in. (I think it might without me doing any calculations, I will let the bongos do the calculations!)

 

[masona]

How fast does the earth spin?

The speed at which the earth spins varies upon your latitudinal location on the planet. If you're standing at the north pole, the speed is almost zero but at the equator, where the circumference of the earth is greatest, the speed is about 1,038 miles per hour (1,670 kph). The mid-latitudes of the U.S. and Europe speed along at 700 to 900 mph (1125 to 1450 kph)

 

[wobs]

So why don't all things on the ISS gravitate towards the Earth?

They do insomuch as the ISS is constantly falling towards the earth otherwise it'd fly off in a straight line. So all things inside it do too. But relative to the ISS, things appear "weightess", er, I think

Pretty close.
The ISS is falling to Earth, and they have to start booster rockets to maintain its altitude.

There is a micro gravity on the ISS, but its effectively zero G.

 

[wobs]

If earth was made up of lead entirely, its mass would exceed that of the sun and it would suck the sun in. (I think it might without me doing any calculations, I will let the bongos do the calculations!)

Wrong.
No, this is really really wrong.

The sun is 1.9891×10^30 kg or 333,000 Earths

Lead is not 333000 more dense than what the Earth is made of (mostly: iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%))

Play your own bongos.

 

[Mikefromlondon]

wobs, whatever, no one can actually say these figures are accurate, since density varies, even on our own planet, so end of the day these figures are a best guess, based on average dispersion of matter and so on, don't forget the sun can spew millions of tons of matter into the space through eruptions, so no one could actually work out a steady weight for both sun and the earth, as earth itself gets matter deposited during meteor and other space debris falling to earth, and we keep taking out some via space exploration.

So in the end your figures are just as good as mine. Play your bongos now!

 

[wobs]

wobs, whatever, no one can actually say these figures are accurate, since density varies, even on our own planet, so end of the day these figures are a best guess, based on average dispersion of matter and so on, don't forget the sun can spew millions of tons of matter into the space through eruptions, so no one could actually work out a steady weight for both sun and the earth, as earth itself gets matter deposited during meteor and other space debris falling to earth, and we keep taking out some via space exploration.

So in the end your figures are just as good as mine. Play your bongos now!

Have you got anything that is based upon reailty?
The factors that you gave are so miniscule as to be ignored. Mass of the Earth and Sun are well known in science.

You are wrong. Again.

 

[Dextraneous]

Mass of the Earh and Sun are well known in science.

You are wrong. Again.

Makes one wonder how they worked it out.

 

[jeds]

Force of gravity weakens inversely proportional to its distance, but never completely disappears, but for practical purposes we can say that the space lab has a very weak influence from the earth's gravity due to its distance away from earth, the earth may still exert some minute pull at it, and hence every so often most satellites and space stations need correction via small rockets, hence all satellites must carry some on board fuel for this correction, hence the amount fuel for correction is what determines a life of a satellite.

That's also wrong. The ISS is held by Earths gravitational attraction and is in free fall towards the Earths centre- otherwise it would fly off into space. The main reason it needs adjusting occasionally is because even at that height there is a tiny amount of atmosphere which causes a tiny amount of drag.

 

[jeds]

Mass of the Earh and Sun are well known in science.

You are wrong. Again.

Makes one wonder how they worked it out.

Backward calculation worked out from the orbit. The orbit is observable and measurable - the mass is backward calculated from that. That's how we know the mass of comets, far off planets and stars etc.

 

[jeds]

wobs, whatever, no one can actually say these figures are accurate, since density varies, even on our own planet, so end of the day these figures are a best guess, based on average dispersion of matter and so on, don't forget the sun can spew millions of tons of matter into the space through eruptions, so no one could actually work out a steady weight for both sun and the earth, as earth itself gets matter deposited during meteor and other space debris falling to earth, and we keep taking out some via space exploration.

So in the end your figures are just as good as mine. Play your bongos now!

Have you got anything that is based upon reailty?
The factors that you gave are so miniscule as to be ignored. Mass of the Earh and Sun are well known in science.

You are wrong. Again.

You're on a loser mate. Mike gets all his info direct from his god.

 

[wobs]

wobs, whatever, no one can actually say these figures are accurate, since density varies, even on our own planet, so end of the day these figures are a best guess, based on average dispersion of matter and so on, don't forget the sun can spew millions of tons of matter into the space through eruptions, so no one could actually work out a steady weight for both sun and the earth, as earth itself gets matter deposited during meteor and other space debris falling to earth, and we keep taking out some via space exploration.

So in the end your figures are just as good as mine. Play your bongos now!

Have you got anything that is based upon reailty?
The factors that you gave are so miniscule as to be ignored. Mass of the Earh and Sun are well known in science.

You are wrong. Again.

You're on a loser mate. Mike gets all his info direct from his god.

Yes, I appreciate he has no interest in truth.

 

[luke_vibert_uk]

What if the ISS was positioned on a theoretical treadmill?