[Guest]

question 1:

currently science teaches that mono-pole magnets are impossible. (or may be possible but haven't be found yet.)

wouldn't static electricity that has yet to be discharged fall under the category of mono-pole magnet? it's capable of attracting, repelling, and only has one pole.

question 2:

i was always confused by Einsteins theory of relativity, the more i read about it the less sense i can make of it. for example, we all know that light travel at different velocities in different mediums. therefore one light beam clearly can travel faster than another. for another dilemma if you fire two light beams toward each other from equally stationary objects, they will pass each other at twice light speed. (they will cover the distance to the other stationary object in the same amount of time.) can you explain these phenomenons under Einstein?

question 3:

i was always confused by the strong and weak nuclear force. they were "discovered" when it was realized protons being positively charged and necessarily repelling would break the atom apart, and electrons be negatively charged and attracting to the positive would crash and stick to the center of the atom. where do these forces emanate from? how do they act without losing power? why doesn't the strong nuclear force decrease at the same 1/r^2 law that all other forces decrease at? why wouldn't the strong nuclear force over take the weak one?

question 4:

I've heard it stated the the moon's gravity causes our tides. i find this difficult to believe. firstly the moon is quite far from us. secondly its much smaller than earth. thirdly, it has far less mass than it should. basically the moon's gravity amounts to holding a pea 10 meters above your head. even if water was readily compressible, which it's not, i don't see how this could feasibly give us several meters of ocean tides, and on both sides of the planet. anyone?

[Guest]

In answer to queston 2.

In your question you ask how two light beams fired toward each other from equally stationary objects will pass each other at twice light speed. The answer is -- they can not.

Take for example two cars on a highway, both travelling at the same posted speed limit but in different directions. When they pass each other, neither of them suddenly is travelling at twice their velocities. It is only relative to each passenger and driver in each vehicle that the other vehicle is travelling twice as fast at that moment. This "effect" is due in that each vehicle is veiwed as a "stationary" point of reference to its own driver and passengers and the car is seen as in motion.

From the Theory of Relativity, if you, as an observer saw two light beams fired at each other, and knowing that the two beams were fired at each other from stationary points of reference to each other, and you calculated that the speed of the two beams were twice the speed of light...then, (a) you may be wrong in your calculations, and-or (b) you, yourself, are not in a stationary frame of reference to the two other points.

[Guest]

dej mar-

let's say i put one light beam emitter on a wooden board. relative to me the wooden board isn't moving. i place another light beam emitter on another wooden board facing the opposite direction. i fire one light beam. i note the amount of time it takes to travel. i fire the other light beam, i note the tome it takes to travel. i fire both beams. i note that light didn't slow down or experience any other warping or relativistic effects compared to each other. i feel i can state from my perspective that the two light beams passed each other at twice light speed. just as the two cars would appear to be going toward each other at double their velocity.

[Guest]

i fire both beams. i note that light didn't slow down or experience any other warping or relativistic effects compared to each other. i feel i can state from my perspective that the two light beams passed each other at twice light speed.

And how did you arrive at that perspective?

I doubt you performed this experiment or have performed it with a realistic timing device. For it to have actually been a "realistic" perspective, you would have to have been riding one (or along side one) of the beams. If you (could) have done that, then you don't need me to assist you in finding an answer to a question of physics, for you would have invalidated the known laws of physics.

Edited July 25, 2010 by Dej Mar

[Guest]

dej mar, why would i need to ride the light beams to note their speed? if i can calculate the amount of time it takes to cover a particular distance, is that not measuring speed? if can measure two light beams firing at each other and see that they are capable of meeting at the half way point in half the time, in what way would they not be traveling at twice light speed from my prospective?

[unreality]

if can measure two light beams firing at each other and see that they are capable of meeting at the half way point in half the time

the problem is that you cannot do that So firing one light beam on the other side of the room will magically reduce the time of the other light beam?

Say the room is 1 lightyear wide (that's a big room ). You have a light emitter on each end, spaced a little apart though so that the light beams can "pass" each other.

After half a year, the light beams will pass each other

After a year, they will hit the opposite wall of the 'room'.

That's all there is to it. Relative to you (if you are standing still in the middle) they are both moving at the speed of light. But relative to the photons, the photons moving in the opposite direction are moving at double the speed because if they consider themselves stable then it means the REST of the world is actually moving "backwards" at the speed of light, so compound that with the photons that are actually (from your perspective) moving that direction at the speed of light, and you get 2c. But that's just an illusion of the frame of reference. Their actual velocity each is C

[Guest]

question 1:

currently science teaches that mono-pole magnets are impossible. (or may be possible but haven't be found yet.)

wouldn't static electricity that has yet to be discharged fall under the category of mono-pole magnet? it's capable of attracting, repelling, and only has one pole.

question 2:

i was always confused by Einsteins theory of relativity, the more i read about it the less sense i can make of it. for example, we all know that light travel at different velocities in different mediums. therefore one light beam clearly can travel faster than another. for another dilemma if you fire two light beams toward each other from equally stationary objects, they will pass each other at twice light speed. (they will cover the distance to the other stationary object in the same amount of time.) can you explain these phenomenons under Einstein?

question 3:

i was always confused by the strong and weak nuclear force. they were "discovered" when it was realized protons being positively charged and necessarily repelling would break the atom apart, and electrons be negatively charged and attracting to the positive would crash and stick to the center of the atom. where do these forces emanate from? how do they act without losing power? why doesn't the strong nuclear force decrease at the same 1/r^2 law that all other forces decrease at? why wouldn't the strong nuclear force over take the weak one?

question 4:

I've heard it stated the the moon's gravity causes our tides. i find this difficult to believe. firstly the moon is quite far from us. secondly its much smaller than earth. thirdly, it has far less mass than it should. basically the moon's gravity amounts to holding a pea 10 meters above your head. even if water was readily compressible, which it's not, i don't see how this could feasibly give us several meters of ocean tides, and on both sides of the planet. anyone?

Great questions phillip.

I'll do my best to answer some.

Question 1: No, static electricity could not be classified as a monopole magnet, despite the similar properties you listed. Both magnets and stationary charged particles can create "action at a distance", but the mechanisms in which they do so are completely different. Static electricity makes use of electric fields, while magnets make use of magnetic fields. These two fields are very closely related by Maxwell's equations, and together make up the electromagnetic interaction: one of the four fundamental forces in the universe. Although the large scale effects may seem the same, these types of fields differ greatly. For one thing, magnetic fields are only produced by moving charges, or changing electric fields, while all charged particles emit electric fields regardless of motion.

When you have a magnetic material, what is actually happening is that large large numbers of electrons are making small orbits in the material (motions create magnetic fields). These orbits in normal materials are all randomly oriented and cancel each other out, but in a magnet, they align and add together to create powerful magnetic fields. Another major difference between electric and magnetic fields, is that static electric fields naturally diverge from a single location and extend in every direction to infinity. Magnetic fields tend to vortex however, and always seem to form closed loops.

In a bar magnet, one end of a field line loop goes out of the North side, wraps around in the space around the magnet and goes back to the South side, completing the loop inside the magnet. Because of this closed loop nature, it seems that North and South poles must always come together in real magnets.

question 2: Einstein does actually say that even from a relative perspective, all light moves with a speed of c. You bring up a good point about light travelling at different speeds in different mediums. The answer to this apparent dilemma is that when light travels through a medium, it does not actually follow a straight path. It is chaotically reflected and rereflected, absorbed, and emitted in such a way that the average transmitted power propagates at a speed slower than c.

From the large scale world, it appears however that the light is travelling slower than c.

What you are talking about with the relative velocities adding together is what is called the Galilean transformation.

If 2 cars are driving towards each other, to each it appears that the other is travelling with a speed equal to the sum of their speeds. Einstein, without any real proof, postulated that the speed of light does not obey this transformation, but rather what's called the Lorentz transformation. For slow speeds (much less than the speed of light, but potentially faster than anything we can comprehend still), the Galilean transformation and the Lorentz transformation are approximately equal. Only at relativistic speeds (approaching c) do these transformations diverge from one another. It so happens that the Lorentz transformation also solves the problem of light travelling at a constant speed of c regardless of perspective.

question 3: I don't think I can completely answer this. Definitely I cannot answer where these forces come from. There are 4 fundamental forces that physicists have discovered. Maybe there are more, who knows. Gravity, electromagnetism, the strong force, and the weak force are the four. Perhaps dark energy is another. I don't think that the strong and weak force are necessarily in opposition within an atom, although I am not sure. No scientist can answer "why", only "how".

question 4: I think you are underestimating the effects of the moon. I'm not sure if your data is correct but even if it is, perhaps the answer can be explained by saying that although the pull is small, it affects each water particle at the same time, such that there is a net average motion due to the combined pulls of many many particles.

[Guest]

unreality, i'm not saying either beam will speed up. i'm saying their combined speed would appear to be double the original speed.

i know that the velocity of each is C. that's partly my point. if two beams of light are capable of passing each other, each going C, then in what way would their combined speed not be 2C?

let me put the dilemma in a different way. lets say i fire both beams from the same direction from the same object. relative to each other, the two beams would be traveling at 0, right?

[Guest]

1. interesting. thank you. not sure i agree, but i like to try to understand this stuff. in my opinion all magnetism is electricity that has yet to be released.

2. yes I've heard of the sqrt(1 -v^2/c^2) law. once again not sure i can agree. if we have tools that can measure the speed of light, and see that light does indeed speed up or slow down relative to our perspective, i see no reason to use this equation.

3. every force with exception of perhaps gravity is the result of some particle. my question is, which particles create these forces?

4. once agian, i don't see how. gravity acts on the body as a whole. if it was capable of interacting on unique particles in the manner you describe, dropping extremely large objects such as cruisers should see some bending and tearing during free fall.

[Guest]

1. interesting. thank you. not sure i agree, but i like to try to understand this stuff. in my opinion all magnetism is electricity that has yet to be released.

2. yes I've heard of the sqrt(1 -v^2/c^2) law. once again not sure i can agree. if we have tools that can measure the speed of light, and see that light does indeed speed up or slow down relative to our perspective, i see no reason to use this equation.

3. every force with exception of perhaps gravity is the result of some particle. my question is, which particles create these forces?

4. once agian, i don't see how. gravity acts on the body as a whole. if it was capable of interacting on unique particles in the manner you describe, dropping extremely large objects such as cruisers should see some bending and tearing during free fall.

1. there is an interpretation of magnetic fields that goes something like: there exists a frame of reference in which the magnetic field at a particular location appears identical to a static electric field. I'm not all that familiar with that though. The fact is however, that scientists all over the world classify electricity and magnetism as two distinct, but highly related things. Because of this, static electricity does not qualify as a magnetic monopole, but rather an electric monopole, which are definitely known to exist. If you still think that they are the same thing, then consider that it is a convention around the world to separate electricity and magnetism in scientific language. When people say magnetic monopole, they are intentionally excluding electric monopoles, which are already known to exist.

2. Einstein postulated his speed of light ideas and later on they were experimentally validated. No theory is perfect, but some are closer to reality than others. Specifically, Einstein's ideas were shown through experiment to describe reality better than what we had before (Newtonian physics).

http://www.simonsingh.net/1919_Eclipse.html

3. I can interpret your question in 2 ways. A particle is a source for the force, or particles make up the force.

Typically, particles that are sources for forces are fermions, while particles that make up the interaction are bosons. Look those up, they are interesting. Gravity is definitely created by particles : any particle with mass will create gravity. Electromagnetism : any particle with charge will create electric fields, and if in motion, will create magnetic fields (and if accelerated, will create electromagnetic waves). There is another role that particles play. Mainly that electromagnetic interactions can also be modeled as the exchange of massless particles called photons. If gravity has such a particle, physicists will call it a graviton. The strong force has gluons I believe, and the weak force has W-Bosons and Z-bosons. I am not sure what the source particles for the strong and weak force are, I did not specialize in nuclear physics. I think you can find a good explanation somewhere out there on the internet, if one exists. It was my understanding that the strong force was the result of a color force, caused by quark interaction. 3 quarks make up each proton or neutron, and when protons and neutrons are brought close to one another, their quarks interact with each other. I know very little about the weak force.

4. I'm not sure what you mean. If only a single particle with mass existed in the whole universe, it would emanate gravitational fields throughout the entire universe. Any particle coming into contact with such a field would experience a force. Each particle in a body of particles DOES experience the effect of fields. With solid objects, like cruisers, the force of gravity is greatly overpowered by the rigid bonds with neighboring particles that make the object solid. Typically, these intermolecular or interatomic bonds are elastic, and the entirety of all energy produced by the force is transfered into kinetic energy for the entire body of particles. Liquids do not have these rigid bonds and are more susceptible to forces as described above.

Edited July 25, 2010 by mmiguel1

[Guest]

4.

let's say i have an object with increasing dencity.

would the more dence side fall faster than the less dence side? no. we can confirm that all objects no matter how massive fall equally fast. this is my point. gravity acts on the object as a whole. for example the gravity that the triangle itself emits would be measured from the center of mass. not from the individual particles. this is my point.

[Guest]

4.

let's say i have an object with increasing dencity.

would the more dence side fall faster than the less dence side? no. we can confirm that all objects no matter how massive fall equally fast. this is my point. gravity acts on the object as a whole. for example the gravity that the triangle itself emits would be measured from the center of mass. not from the individual particles. this is my point.

i'm sorry phillip but gravity does not know a whole object from a non-whole object.

I don't see how your point about density is related to our discussion.

My argument would not predict that something with more mass would fall faster. From Newton's 2nd law and the the law of gravitation, it is easy to show that an object's acceleration due to gravitational field is independent of its mass.

you say: the gravity the triangle emits would be measured from the center of mass. this is true, but not because all of the gravity "gathers" at that point in reality. There is no single point that will perfectly describe the field that such a triangle emits as if it were a point source. The field the triangle would emit would not be spherical. However, the center of mass/ center of gravity/ whatever/ --- these points represent the best single point approximation for their respective phenomena.

What I'm saying, is that you cannot encompass all of the gravitational information of the triangle as if it were a single point. However if you must do so (to make the problem manageable rather than computationally ridiculous), there does exist a point which would better approximate the effects of the triangle's field if the triangle were to be replaced by a point mass at this location.

Humans cannot fathom the numerous interactions going on within the simplest of objects. To make the study of such things manageable, we make approximations. We take averages of many numbers rather than carrying a gigantic list of billions of numbers. The center of mass is actually an average. It is the average position for all the mass in an object. All masses on the atomic scale have an x,y, and z position. Looking at all of the particles, what is the average x position? The average y position? The average z position? These averages are all of course weighted on mass (something that is 2x massive will have 2x the weight in the average). The set of these three averages identifies a unique point in space : the center of mass.

In reality, this is not a point more significant to the object or to gravity than any other. It is only useful for simplifying physics calculations to the point where we can achieve useful results with a reasonable amount of computational effort. Gravity is not aware of this point and does not decide to act on the object only on this point. Each particle "feels" gravity, but also the rigid bonds of it's neighbors. If gravity displaces a particle, so that it moves closer to a neighboring particle, it will push its neighbor, which will in turn push another neighbor, which will in turn push another neighbor, etc. This ripple of pushing will propagate through an object at the speed of sound. When a particle pushes on it's neighbor it is pushed back upon, such that there may only be a small amount of net force on any given particle at any given time. However there is an average effect on all the particles, as the gravitational pull happens in parallel across all particles. If the object is a rigid solid, then most likely gravity will be too weak to deform it's shape. Rather any "attempt" to deform it will contribute to a net motion of the entire object. If the object in question were not a solid, but rather a gas, then we would see very different behavior. gas particles closer to the earth would experience a stronger pull than liquid particles further from the earth, resulting in a stretching of the original shape (of course there would also be rapid expansion due to diffusion, so this gravitational effect would probably not really be noticeable).

I read once that if you were to pass into a black hole, this sort of height difference alone would be enough to stretch you like spaghetti before you even get close to the center. This is because near a black hole the gravitational force is stronger than the bonds holding your body solid. These forces are nothing compared to the enormous amount of gravity, and your feet will move towards the black hole with at acceleration determined by your feet's r^2, while your head will move towards the black hole with it's slower acceleration due to it's r^2 (assuming you are going feet first).

I would like to impart that every time you treat an object as a single point, you are making a simplifying approximation. You just need to get used to it. If you can't you might spend your whole life trying to predict how fast an apple might when dropped from a tree. There will always be some factor you did not take into account, because even the gravity of the moon, the gravity of the nearest star, and the gravity of a nearby animal might have an effect on the trajectory of the apple. The point is to ignore effects that do not appreciably affect the outcome. This includes the shape and the extent of the apple.

These are simplifications we use to understand the world. We should not confuse them for reality. Think about it: who is to say what an object is anyway. If you have a water bottle, would you consider the water to be part of the same object? It is a different material, so some would say no, however it will move with the water bottle when they are thrown, so some would say yes. Does the gravity of the earth care? Are not the atoms that make up the water bottle themselves objects? Why not consider the center of mass of one of the atoms? When Earth attracts the water bottle, it doesn't care what we classify as objects. If it detects mass it will attract, no matter at what scale we examine the matter, atomic or macroscopic. There is no universal rule that says this water bottle is more of an object than one of it's atoms and hence it's center of mass is more important. That distinction comes from our minds. I'm not sure how else to argue it than by example.

I hope I haven't made too confusing of points.

Edited July 26, 2010 by mmiguel1

[Guest]

Since the gravity thing seems to be the most controversial one (and since the other ones confuse me) I post what I think about it:

Think about a bathtub full of water. When you step on it, the water level rises because you applied pressure on that spot, and the water goes to where the pressure is lowest. It also tries to push your foot back, and if it succeeds, the water level won't rise at all. Now think about the ocean as a whole. If the moon is right above a certain spot, it will pull every particle in that spot, countering the Earth's gravity. Which means the resulting gravity will be weaker. Great time to practice parkour. Not really. The difference is really small, but there's a difference nevertheless, and it will reduce the pressure on the water (the pressure in deep water results from the weight - not the mass - of all the water and air above it). As I said before, water goes to where the pressure is lowest, so the tide rises. Going back to the bathtub, imagine that you have a piston the exact size of the tub, but with a hole in the middle (the hole being where the moon is in the metaphor). When you apply pressure to the piston on the tub, the water will rise in the hole, because that's where the pressure is lowest.

[Guest]

what i'm trying to get to is the fact that gravity acts on every particle in the unvierse, from every paticle in the universe. sure, the gravity felt from a paticle on one side from the other would be exceedingly small but it's there. i guess i'm just trying to understand how that's possible. how gravity acts instantanteously (from newton) or even at the speed of light (from einstein) at such vast distances baffles me. i don't have an answer really, i've explored a few ideas, (i kinda like the theory of expanding matter, but that would mean everything doubling in size every 19 minutes.)

with the ocean and the moon, yes every particle is being acted on, but its being acted on as a whole. that is, the whole earth feels the moons gravity, not just ocean particles. you can't really say that the ocean is getting more of a pull from the moon than we are. here's a simple physics experiment you could do to detimine how much the moon's pull affects the ocean. wiegh yourself as acurately as possible when the moon is furthest from you, and then again when the moon is directly over head. see what the differance is. then multiply that differance by the size of the ocean.

*edit* i feel i should point out yet again, F = m*a, even if you double the force, with gravity, that genrally means double the mass as well. that is, the moon's gravity accelerates the ocean at the same rate it does us.

Edited August 10, 2010 by phillip1882

[Guest]

what i'm trying to get to is the fact that gravity acts on every particle in the unvierse, from every paticle in the universe. sure, the gravity felt from a paticle on one side from the other would be exceedingly small but it's there. i guess i'm just trying to understand how that's possible. how gravity acts instantanteously (from newton) or even at the speed of light (from einstein) at such vast distances baffles me. i don't have an answer really, i've explored a few ideas, (i kinda like the theory of expanding matter, but that would mean everything doubling in size every 19 minutes.)

with the ocean and the moon, yes every particle is being acted on, but its being acted on as a whole. that is, the whole earth feels the moons gravity, not just ocean particles. you can't really say that the ocean is getting more of a pull from the moon than we are. here's a simple physics experiment you could do to detimine how much the moon's pull affects the ocean. wiegh yourself as acurately as possible when the moon is furthest from you, and then again when the moon is directly over head. see what the differance is. then multiply that differance by the size of the ocean.

*edit* i feel i should point out yet again, F = m*a, even if you double the force, with gravity, that genrally means double the mass as well. that is, the moon's gravity accelerates the ocean at the same rate it does us.

Yes, both ocean and non-ocean particles on Earth feel the pull of the moon. Solid particles will not deform from such a weak force, while masses of liquid like the ocean would. Now you will ask, why don't we see tides in other bodies of water?

At different points in its orbit the moon applies different magnitudes of gravitational forces to these objects too.

I think there are 2 answers

1) The effect is not drastic enough to be noticed for smaller fluid systems

A puddle shifting 2 cm is not going to draw the same attention as the ocean shifting.

2) There are different, stronger factors influencing these systems (the moon's force difference is weak, but long lasting)

The moon's gravity might alter the path of a cloud, if it weren't for strong winds blowing it in the other direction.

[Guest]

One more thing,

when you say F = m*a, this is only true if F is the net force on the object, that is, the sum of all forces acting on the object.

The moon does not do any acceleration on the oceans or our bodies because the net force (from the frame of reference of the earth) is zero for the objects as a whole on average.

If the moon could maintain the creation of an average acceleration for us, we would crash into the moon or revolve around it.

Strictly speaking, you are right, the moon does accelerate both the oceans and us at the same rate, which is zero.

I know, I know:

F = m*a = G * M * m / r^2

and

a = G * M / r^2

but that equation assumes that gravity from M is the only force acting on m, which is almost never the case.

Also, the ocean WOULD get more of a pull from the moon than us because the ocean is more massive (the force is proportional to product of the masses of both interacting objects). More pull means more force, not more acceleration. The extra force would be needed to overcome the extra inertia of having that much mass in the first place, such that overall acceleration is the same in free space with no other forces.

For me sitting here, there are 3 forces of interest, all else being assumed negligible.

There is the pull of the moon, the pull of the earth, and the normal force between the ground and my feet (assume I'm standing).

If there was no moon, the normal force between the ground and my feet would equal the pull of the earth (magnitude-wise of course).

Let M = mass of earth

N = mass of moon

m = mass of me

R = radius of earth

r = distance between earth's surface and the center of the moon

If I were standing on a scale, then the scale would read G*m*M/R^2

Now taking into account the moon, it provides a pull on me directed upwards (for simplicity) of G*N*m/r^2

The force between the scale and my feet adjusts so that my net force is zero.

It will thus have magnitude

G*m*(M/R^2 - N/r^2)

Note that this force does depend on my mass (it is a scale after all, it should shouldn't it?), and so this experiment would not so easily apply to the ocean via your argument that the moon has the same affect on the oceans as us.

There are bigger problems to the experiment though. We modeled me as a point on the earth's surface. The ocean cannot be modeled as a point, it must be modeled as a hollow sphere the size of the earth with holes punched out of it for the continents. That is, the ocean on the side of earth away from the moon should behave significantly different than the ocean on the side nearest to it, and a simplification of the ocean into a single point is not sufficient to accurately capture the phenomenon of interest.

You are thinking of the ocean too much like a point mass. You are considering the properties of a point mass that change when forces are applied, like position, velocity, acceleration. But the ocean cannot be modeled as a point mass (unless we are talking about something much bigger than the moon). Although the position, linear velocity, and linear acceleration of the ocean are NOT changing due to the force, other properties not present in a point mass such as shape are changing.

An example of another such property could be the spinning kinetic energy of a wheel. To get a wheel moving, energy must be spent not only to get it's linear velocity up (moving along the surface of the earth), but also it's angular velocity (revolutions per second for example). With the same amount of energy, neglecting dissipative friction, you cannot get a rolling wheel as fast as you could get a non-rolling object, all else being equal, if both begin at rest and not spinning. This is because you have to spend some of the energy in making the wheel rotate rather than putting all energy into linear motion. When working with point masses, spin is not taken into account either and a spinning wheel is another example of something that cannot be adequately modeled as a point mass.

Edited August 11, 2010 by mmiguel1

[Guest]

miguel here's my problem with the moon ocean tides relationship. (and newton's idea in general.)

F = G* M*m/r^2

force of moon on ocean = 6.673 * 10^-11 m^3 /(kg*s^2) * 1.4×10^21 kg 7.36 * 10^22 kg / (384,403,000 m)^2 = 4.6*10^16 kg *m/s^2

force of bowling ball 1 millimeter above ocean = 6.673 * 10^-11 m^3 /(kg*s^2) * 1 kg * 7.36 * 10^22 kg / (.001 m)^2 = 4.9*10^18 kg *m/s^2

a bowling ball next to the earth's surface has 100 times more pull than the moon.

[Guest]

But that's if you consider that the whole ocean is 1 milimeter away from the bowling ball. You need to consider how much the moon's gravity will reduce the overall weight of the ocean water when it's right above a certain section of the Earth (sorry about my bad English). Let's say the Moon's gravity is 0.01% of the Earth's gravity. Then the weight of that part of the ocean will be 0.01% smaller, and as you know, pressure is a function of weight. But the oceans are connected, so you can't just have a low pressure zone in the middle. That's why the water level rises a little to make up for the weight difference. 0.01% doesn't look like much ( and I don't know if it's really 0.01%), but if you think that the ocean can be up to 11km deep... That's why the moon's effect is not noticeable on a swimming pool for example. Because the entire pool is suffering roughly the same effect, and because it isn't deep enough.

[Guest]

Re: question 1:

It's true that it is capable of attracting, repelling, and it has only one pole, but a static charge has no magnetic field, only an electric field. Just because the two are closely related does not mean they are interchangeable. It's not an exact analogy, but you can think of a charge as a source (or sink) of electromagnetic energy (depending on whether it is positive or negative) and a magnetic field is sort of a vortex or wake left behind when a charge moves by.

Re: question 2:

First, when physicists say that nothing travels faster than light, what they mean is that nothing can exceed the speed of light in a vacuum. The speed of light through some medium is always slower. Secondly, there is no contradiction in your example. Because everything is relative, nothing travels faster than the speed of light in your frame of reference. And, in your example, nothing does. It is perfectly acceptable to say that you saw a photon travelling south at c pass by another photon travelling north at c, because, in fact, you did. The photons, however, would disagree with your version of events.

Re: question 3:

You're not the only one to be confused.

The strong force is what holds together the subparticles (quarks) that make up baryons (protons & neutrons & some other esoteric particles). The strong force is very strong at very small distances, roughly the size of a baryon, but then is constant beyond that. So, if you're an object the size of a proton or larger, the strong force is the same between you and a very close particle and a very distant particle, so it all averages to nothing.

I can't remember what carries the weak force, but when it collides with a neutron, it breaks off an electron and an antineutrino, and, uh, a boson or lepton or something else, turning it into a proton. That's about all I remember about the weak force, I'm afraid.

Re: question 4:

If you think of the tides in the same context, it doesn't seem at all far-fetched. If Earth were the size of your head, the highest tides in the world would be roughly 200 nm, about 1/500 the thickness of a hair.

I hope this helps.