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Author Topic: How does mankind know that we are being pulled to the ground?Im havin doubts!  (Read 11813 times)

Offline gazza711

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I would be interested to know what objects, that are visible around us, today rely on the fact that we are being pulled towards the ground.   :P

And not only that but how would these things still function if we were not being pulled to the ground....   [:I]

Some possible examples for consideration: cars, shoes, hydroelectric dams, rain, rockets, golf and even the Moon.
How do you know everything is being pulled down.You know that trick when you spin a wheel fast enough,you can tell which way its turning.surely if all things attracted,especially LEAD,then the universe and solar system would just stick to itself and it would just be one lump of ###
 

Offline chiralSPO

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There are two reasons that the universe in not one big lump, despite all the matter attracting all the rest of the matter:

1) Energy--there is enough energy in the universe to break that lump into smaller pieces, and enough left over to make these pieces move around.

2) Space--there is enough space in the universe that two clumps of matter are unlikely to get close enough together to stick.

Now for the interesting part: the amount of (kinetic) energy that the matter has is decreasing over time (on average, the universe is getting colder and things are moving more slowly), implying that as time goes on, the universe is more likely to condense into this large lump you mention. But the amount of space appears to increasing as well, and this would imply that it is getting more difficult for the universe to collapse into a large lump.

Which is it? We don't know for sure, but most cosmologists agree at this point that the expansion will beat out the cooling.
 

Offline evan_au

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I would add a third reason why everything doesn't collapse together:

3) Orbiting in a gravitational field does not dissipate energy. So even objects which are close enough to attract each other strongly, like the Sun and the Earth, the Earth and the Moon, or the Sun and the galactic black hole, they do not collapse into one another. As they get a little bit closer, they speed up; they then move further away and slow down again - this produces an elliptical orbit which is stable for astronomical periods of time.

(There is a small amount of gravitational radiation which does affect closely-orbiting neutron stars; this can be ignored for objects the size of the Solar System.)
 

Offline Ophiolite

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In forty days time New Horizons will arrive at Pluto. To do so it made a close approach to Jupiter in order to pick up speed. If it performs in a comparable way to other planetary probes it will arrive, after a decade long journey, within seconds of its planned arrival time.

How would this be possible, gazza, if we did not have a sound understanding of gravity?
 

Offline PmbPhy

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Quote from: gazza711
How do you know everything is being pulled down.You know that trick when you spin a wheel fast enough,you can tell which way its turning.surely if all things attracted,especially LEAD,then the universe and solar system would just stick to itself and it would just be one lump of ###
You can't be serious! Think about what you just said. If you threw a stone and another stone when they stick together because of their gravitational attraction or would they simply bounce off of each other? Do you know why all of the planets in the solar system have been revolving around the sun these last 4 billion + years and haven't fallen into the Sun due to its gravitational field?
 

Offline gazza711

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I would add a third reason why everything doesn't collapse together:

3) Orbiting in a gravitational field does not dissipate energy. So even objects which are close enough to attract each other strongly, like the Sun and the Earth, the Earth and the Moon, or the Sun and the galactic black hole, they do not collapse into one another. As they get a little bit closer, they speed up; they then move further away and slow down again - this produces an elliptical orbit which is stable for astronomical periods of time.

(There is a small amount of gravitational radiation which does affect closely-orbiting neutron stars; this can be ignored for objects the size of the Solar System.)
So I totally agree on what you have said.I never stated my theory was fact-just who agreed.Until we can simulate conditions of space and mimic all that we believe,then its still a theory isn't it?if gravity was indeed proved-it wouldn't be a theory still after 4 billion years.I guess if someone said-hey eureka-we can explain this,then one might ask that the attraction is more to with either the motion of water being swished and something being dragged in the path replacing it.that would be displacement like smoking out a moving car window and a car drives past and sucks that away.who knows.
 

Offline evan_au

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Quote from: gazza711
either the motion of water being swished and something being dragged in the path replacing it.that would be displacement like smoking out a moving car window and a car drives past and sucks that away
The motion of water and smoke are both considered problems in hydrodynamics. Both are "dissipative systems", where the large scale motion breaks up into whirlpools or vortices, and these spin off even smaller vortices, and so on until the energy is largely dissipated.

This is entirely unlike the motion of planets around the Sun, which are conservative in nature - they basically keep the same angular momentum over time (with a bit of trading backwards and forwards between the planets).

Quote
who knows.
Scientists puzzled this out over a century or two - Newton's law of universal gravitation is quite simple, and predicts orbits which are periodic for hundreds of millions of years into the future (although they eventually degenerate into chaotic motion, even without external influences). It is very accurate, and just needed a small tweak from Einstein in the case of Mercury.
 
The Navier Stokes equations describing the motions of fluids are far more complex, are very hard to solve, and result in chaotic motion on a millisecond-by millisecond basis. Despite their great economic value in improving the aerodynamics of aeroplanes and predicting the weather, they can only be roughly approximated on today's largest computers.

Newton basically invented differential equations as part of proving the uniqueness of the inverse square law of gravity (around 1670). The Navier-Stokes equations (early 1800s) require partial differential equations, which were a much later development in mathematics. 

So I guess you could say that for about the last 2 centuries, it has been known by everyone who took the trouble to ask.
 

Offline Ophiolite

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Until we can simulate conditions of space and mimic all that we believe,then its still a theory isn't it?
You really need to learn what a scientific theory is. Ignorance is something we all have and is nothing to be ashamed of. Deliberate, persistent ignorance is another matter.

You could start here, but if you can't be bothered, this sentence gets to the heart of the matter.

Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge

Do you understand? In science you don't get better than a theory.
 

Offline PmbPhy

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Quote from: gazza711
Until we can simulate conditions of space and mimic all that we believe,then its still a theory isn't it?if gravity was indeed proved-it wouldn't be a theory still after 4 billion years.
First of all it's quite literally impossible to simulate "conditions of space and mimic all that we believe" because that includes all the permutations of the various conditions that are possible and that's an infinite number of states. Second of all it appears as if you think as the term is used in science and by scientists that the term "theory" is merely a synonym for an hypothesis and it most certainly isn't. See: http://www.merriam-webster.com/dictionary/theory

Or better yet, see: http://en.wikipedia.org/wiki/Theory
Quote
In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that any scientist in the field is in a position to understand and either provide empirical support ("verify") or empirically contradict ("falsify") it. Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge, in contrast to more common uses of the word "theory" that imply that something is unproven or speculative (which is better characterized by the word 'hypothesis'). Scientific theories are distinguished from hypotheses, which are individual empirically testable conjectures, and scientific laws, which are descriptive accounts of how nature will behave under certain conditions.
Note the part I underlined which said Scientific theories are distinguished from hypotheses..
 

Offline PmbPhy

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simply-what evidence do we have.anal I know,but ive seen many things since theorizing this that is defeating this theory.dont forget that science theorises a lot about things about space.there is no proof that I know of that shows 2 objects of different sizes attracting one another due to GRAVITY.This experiment doesn't work in space either does it?
Let me ask you something without having to reread this entire thread all over again. Have you figured out that there's an enormous amount of observational data and experiments which confirm the theory of gravity? If the theory of gravity, based on the force between two point objects having a force of F = GMm/r2 was wrong then we'd never have been able to send all those probes that we've sent out into the solar system and get to where we expected them to go. And that required an extreme amount of precision. In fact the discovery of Neptune was a sensational confirmation of Newton's theory of gravity. See:
http://en.wikipedia.org/wiki/Discovery_of_Neptune

For more evidence see: http://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation
 

Offline Ophiolite

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Is there an echo here?
 

Offline gazza711

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simply-what evidence do we have.anal I know,but ive seen many things since theorizing this that is defeating this theory.dont forget that science theorises a lot about things about space.there is no proof that I know of that shows 2 objects of different sizes attracting one another due to GRAVITY.This experiment doesn't work in space either does it?
Let me ask you something without having to reread this entire thread all over again. Have you figured out that there's an enormous amount of observational data and experiments which confirm the theory of gravity? If the theory of gravity, based on the force between two point objects having a force of F = GMm/r2 was wrong then we'd never have been able to send all those probes that we've sent out into the solar system and get to where we expected them to go. And that required an extreme amount of precision. In fact the discovery of Neptune was a sensational confirmation of Newton's theory of gravity. See:
http://en.wikipedia.org/wiki/Discovery_of_Neptune

For more evidence see: http://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation
Hi.What proof can you show me that objects attract on earth.Cavendish experiment only helped newtons theory-Neptune discovery based on Stonehenge predicting seasons for example.neptune had been discovered before but not predicted when it would return on its path.theories are predictions.einstein improved the theory but didn't change.theres a million disproven theories.the fact that things fall do not mean they are being pulled unless you can see the force(like magnetic flux)
.....
 

Offline chiralSPO

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If you don't accept that the cavendish experiment proves the attraction of objects, then there isn't much hope that anything said in this forum will change your mind...

The gravitational force is just as easy to "see" as magnetic fields (they are both completely invisible), I don't understand what the holdup is there...

Gravity is not only a force that shows itself when causing objects to fall--it's also responsible for requiring energy to lift objects up (or hold them up). You can feel the gravitational pull of the Earth every time you climb the stairs and every time you lift anything heavy.

Theories are more than predictions. Theories are what we use to make predictions. The theory of gravity allows us to predict the orbits of all of the planets and moons in our solar system and others, allows us to send probes wherever we wish within the solar system; allows us to put satelites up around the Earth, allows us to launch missiles from any point on the Earth to any other point on the Earth etc. etc. etc.

 

Offline PmbPhy

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Quote from: gazza711
Hi.What proof can you show me that objects attract on earth.
The Cavendish experiment of course. That is precisely the experiment that directly tests that relationship. But there's no reason to assume, in fact its irrational to think otherwise, that gravity doesn't work on Earth given that it does work for planets

Quote from: gazza711
Cavendish experiment only helped newtons theory..
So what? That's what you're talking about. I.e. Newton's theory is that F = GMm/r2 and that's what the Cavendish experiment directly tests. This has been explained to you many times. I suggest that you cease trying to claim that it's wrong and start trying to understand why it's right. You've been given direct experimental observations and all you do is claim that they aren't such. That's quite illogical.

Quote from: gazza711
-Neptune discovery based on Stonehenge ..
What??? "based on Stonehenge"? You've got to be kidding me! It's the relation F = GMm/r2 that was used to find Neptune.

Quote from: gazza711
neptune had been discovered before ..
That is absolutely wrong. Please check your facts before posting misinformation like this.

Quote from: gazza711
theories are predictions.
Wrong. You should learn what theories are before you try to claim what they are.

Quote from: gazza711
einstein improved the theory but didn't change.
Wrong yet again.

Quote from: gazza711
theres a million disproven theories.
No evidence to support such claims. Probably because you don't appear to understand what a theory is. You appear to be confusing it with an hypothesis.

Quote from: gazza711
the fact that things fall do not mean they are being pulled unless you can see the force(like magnetic flux)
Wrong again.
 

Offline gazza711

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Quote from: gazza711
Hi.What proof can you show me that objects attract on earth.
The Cavendish experiment of course. That is precisely the experiment that directly tests that relationship. But there's no reason to assume, in fact its irrational to think otherwise, that gravity doesn't work on Earth given that it does work for planets

Quote from: gazza711
Cavendish experiment only helped newtons theory..
So what? That's what you're talking about. I.e. Newton's theory is that F = GMm/r2 and that's what the Cavendish experiment directly tests. This has been explained to you many times. I suggest that you cease trying to claim that it's wrong and start trying to understand why it's right. You've been given direct experimental observations and all you do is claim that they aren't such. That's quite illogical.

Quote from: gazza711
-Neptune discovery based on Stonehenge ..
What??? "based on Stonehenge"? You've got to be kidding me! It's the relation F = GMm/r2 that was used to find Neptune.

Quote from: gazza711
neptune had been discovered before ..
That is absolutely wrong. Please check your facts before posting misinformation like this.

Quote from: gazza711
theories are predictions.
Wrong. You should learn what theories are before you try to claim what they are.

Quote from: gazza711
einstein improved the theory but didn't change.
Wrong yet again.

Quote from: gazza711
theres a million disproven theories.
No evidence to support such claims. Probably because you don't appear to understand what a theory is. You appear to be confusing it with an hypothesis.

Quote from: gazza711
the fact that things fall do not mean they are being pulled unless you can see the force(like magnetic flux)
Wrong again.
Hey clever dude.stone henge helped people predict.thats what were talking about.just because ur all phd whatevers,ur to arrogant to accept anything other than GR and Newtonian laws.if u research both,u might find theyre both flawed and this is mentioned many times by scientists over many years.look into liquids under different atmospheric pressures on other planets.
to planets.no gravity there?look into what could happen to humans if exposed to space.do they freeze or boil.i mearly asked the question-what proof do we have we are being pulled down to the earth.not one person on this site can answer that.arrogance or inquisitive?look into my theory across the internet that vacuum pressure causes atmos pressure which causes "gravity".
if gravity were so,why doesn't light bend towards the earth?hmmmm
newton law=earth is flat
Einstein theory=world is round.both incorrect but acceptable.ive done my research and its ongoing.oh and equations help people predict accurately-a theory is a theory not a fact.the theory of gravity has many theories-none proven.casimer effect is the best answer ive seen and string theory.cavendish and all other experiment showed mankind nothing.what proof do we have that we are attracted to earth!!!!!easy question  and only 5 people on this site-time to move on with this as no answer available.shame.i thought this was a scientific forum.and im not a troll-im logical and untrained in physics.peace
 

Offline jccc

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how long can you lift 1 leg in the air?

what is pulling it down? vacuum pressure?

you are full of it, why?
 

Offline gazza711

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how long can you lift 1 leg in the air?

what is pulling it down? vacuum pressure?

you are full of it, why?
I expected some people to have a broader view of what we don't understand.I don't mean to be cheeky,but others comment with things like what happens when we throw things up-they come down.The most misguided word always used is PULL.Prove it?Vacuum pressure would be the pressure of the air bubble that we live on with a solid crust and liquid centre consisting of metal elements.Now mimic the earth on a micro scale in a vacuum in outer space.
Impossible -I know.when you throw a rubber duck with air in it hard into water.it will sink then float.buoyancy I know.But what force is dragging it back to the surface?anti-gravity.Air around us is less dense than water but behaves in the same way as water.it deflects when we move through it.both apply force on everything form 360 degrees.so why do we believe we are pulled down?we cant see the flux of gravity and we cant see buoyancy but we can see magnetic flux.the only thing convincing us is the Cavendish experiment which only used lead-research lead and how it interacts with other materials/situations.if you seek an answer you will find it I say.peace
 

Offline chiralSPO

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As a moderator, I would like to remind everyone to remain civil. This thread is getting a little heated.
~~~~~~~~~

Now on to the science!

gazza711, perhaps you would like to share some experimental evidence that your theory is correct. Or do you believe that experimental evidence is not important?

I don't understand your objection to the use of lead in the Cavendish experiment. You also seem to make some claims about the effects of oxygen and nitrogen on gravtiy that I don't understand. Could you clarify what the different elements do?

 

Offline gazza711

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As a moderator, I would like to remind everyone to remain civil. This thread is getting a little heated.
~~~~~~~~~

Now on to the science!

gazza711, perhaps you would like to share some experimental evidence that your theory is correct. Or do you believe that experimental evidence is not important?

I don't understand your objection to the use of lead in the Cavendish experiment. You also seem to make some claims about the effects of oxygen and nitrogen on gravtiy that I don't understand. Could you clarify what the different elements do?
Sure-no one who commented answered the question.end of.they shouldnt reply if they cant answer the question with proven answers.Unfortunately nobody would understand anything other than PULL and its a waste of my time explaining where others who choose to comment should do their research first too.if I had evidence,I wouldn't be chatting openly about it here-or would I.what is your understanding of the Cavendish experiment? ;D ;D ;D
 

Offline chiralSPO

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How can you be so certain if you have no evidence?

How can you claim that the theory of gravitation is wrong because it has no evidence, when there is so much evidence for it. Even if we call into question the Cavendish experiment itself (which would be illogical, but for the sake of argument, let's say that experiment may have been flawed somehow), other similar experiments have been performed on Earth:

http://en.wikipedia.org/wiki/Schiehallion_experiment
http://adsabs.harvard.edu/full/1896ApJ.....3..303W
http://en.wikipedia.org/wiki/Gravitational_constant#History_of_measurement
http://www.livescience.com/46385-new-gravitational-constant-measurement.html

It has also been shown to hold in space for every system we have studied in depth...
 

Offline gazza711

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How can you be so certain if you have no evidence?

How can you claim that the theory of gravitation is wrong because it has no evidence, when there is so much evidence for it. Even if we call into question the Cavendish experiment itself (which would be illogical, but for the sake of argument, let's say that experiment may have been flawed somehow), other similar experiments have been performed on Earth:

http://en.wikipedia.org/wiki/Schiehallion_experiment
http://adsabs.harvard.edu/full/1896ApJ.....3..303W
http://en.wikipedia.org/wiki/Gravitational_constant#History_of_measurement
http://www.livescience.com/46385-new-gravitational-constant-measurement.html

It has also been shown to hold in space for every system we have studied in depth...
Ok.gravity on earth is not the same in space.casimir effect not newton theory.
other experiments were out to measure masses and densities and proved gravitational attraction-they were all made with lead weights not apples-
the schiehallion experiment.hmm-did they use a spirit level.once again they must have used lead as plumb lines would've been lead at that time.hmmm.lead/metal/conductor or equivalent as well as when a man goes straight up and holding a stick and weight for example,he isn't really going straight up vertically.if two men dug a hole each 5 metres apart and dug down far enough,the holes would meet.thus proving the experiment to not prove attraction.show me a experiment where theres attraction without using a metal or conductive material.water carries current and is magnetic plus there are stronger and weaker (gravity)points all over the earth.

 

Offline gazza711

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How can you be so certain if you have no evidence?

How can you claim that the theory of gravitation is wrong because it has no evidence, when there is so much evidence for it. Even if we call into question the Cavendish experiment itself (which would be illogical, but for the sake of argument, let's say that experiment may have been flawed somehow), other similar experiments have been performed on Earth:

http://en.wikipedia.org/wiki/Schiehallion_experiment
http://adsabs.harvard.edu/full/1896ApJ.....3..303W
http://en.wikipedia.org/wiki/Gravitational_constant#History_of_measurement
http://www.livescience.com/46385-new-gravitational-constant-measurement.html

It has also been shown to hold in space for every system we have studied in depth...
Ok.gravity on earth is not the same in space.casimir effect not newton theory.
other experiments were out to measure masses and densities and proved gravitational attraction-they were all made with lead weights not apples-
the schiehallion experiment.hmm-did they use a spirit level.once again they must have used lead as plumb lines would've been lead at that time.hmmm.lead/metal/conductor or equivalent as well as when a man goes straight up and holding a stick and weight for example,he isn't really going straight up vertically.if two men dug a hole each 5 metres apart and dug down far enough,the holes would meet.thus proving the experiment to not prove attraction.show me a experiment where theres attraction without using a metal or conductive material.water carries current and is magnetic plus there are stronger and weaker (gravity)points all over the earth.
How can we be taight that gravity pulls when we cant prove it-same question you asked me-except all the other planets show exactly what temp/pressure can do to a planet.buoyancy is gravity (on earth)and its not the same as space attraction
 

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