Think Science .

Richard feyman(1918-1988) is one of the most respected and famous among physics student. Not just physics student but among any science student. His lectures on physics are very famous. And his work is scattered across the internet. So i decided that it is good to compile it in single list so anyone wants to find more information and links can get it from single source.

Read Richard feyman’s “Surely you’re joking Mr.Feynman“
http://www.gorgorat.com/

One stop resource for the richard feyman related links, there are many others not listed on that web page, but stil it is an excellent resource.
http://www.feynmanonline.com/

Richards Solutions to some of the common problems in physics.
http://www.feynmanlectures.info/exercises.html

Feyman’s Tips on Physics are maintained at below URL.
http://www.aw-bc.com/catalog/academic/product/0,1144,0805390634,00.html

Feyman and water sprinkler experiment.
http://www.fotuva.org/online/sprinkler.html

There are many other resources that i would love to list here. I’ll update the list soon. If you’ve any interesting link then do post it in comments.

Its something which we experience, when we’re/an object in an atmosphere (Space, to be exact); and experiences another force, which attracts us in all directions equally; just the opposite to gravitational force of attraction.

Its not what accelerate the universe’s speed of growth. What do it is the so called dark energy. Anti gravity is a force exactly as gravity, but it pushes instead of pulling. To have it, you must get a spot on space with negative mass/energy, which is impossible today. TODAY!

The description that is accepted today of gravity, is the General Relativity description, which describes it as a curvature of space-time. This curvature is done at a direction, and anti gravity is that same curvature, but at the other direction, meaning inverted gravity.

Right now, the idea to have anti gravity is related with the quantum vacuum, that can get a negative quantity of energy, but we can’t control it right now.

The Moon’s orbit (its circular path around the Earth) is indeed getting larger, at a rate of about 3.8 centimeters per year. (The Moon’s orbit has a radius of 384,000 km.) I wouldn’t say that the Moon is getting closer to the Sun, specifically, though–it is getting farther from the Earth, so, when it’s in the part of its orbit closest to the Sun, it’s closer, but when it’s in the part of its orbit farthest from the Sun, it’s farther away.

The reason for the increase is that the Moon raises tides on the Earth. Because the side of the Earth that faces the Moon is closer, it feels a stronger pull of gravity than the center of the Earth. Similarly, the part of the Earth facing away from the Moon feels less gravity than the center of the Earth. This effect stretches the Earth a bit, making it a little bit oblong. We call the parts that stick out “tidal bulges.” The actual solid body of the Earth is distorted a few centimeters, but the most noticable effect is the tides raised on the ocean.

Now, all mass exerts a gravitational force, and the tidal bulges on the Earth exert a gravitational pull on the Moon. Because the Earth rotates faster (once every 24 hours) than the Moon orbits (once every 27.3 days) the bulge tries to “speed up” the Moon, and pull it ahead in its orbit. The Moon is also pulling back on the tidal bulge of the Earth, slowing the Earth’s rotation. Tidal friction, caused by the movement of the tidal bulge around the Earth, takes energy out of the Earth and puts it into the Moon’s orbit, making the Moon’s orbit bigger (but, a bit pardoxically, the Moon actually moves slower!).

The Earth’s rotation is slowing down because of this. One hundred years from now, the day will be 2 milliseconds longer than it is now.
This same process took place billions of years ago–but the Moon was slowed down by the tides raised on it by the Earth. That’s why the Moon always keeps the same face pointed toward the Earth.

Because the Earth is so much larger than the Moon, this process, called tidal locking, took place very quickly, in a few tens of millions of years.Many physicists considered the effects of tides on the Earth-Moon system. However, George Howard Darwin (Charles Darwin’s son) was the first person to work out, in a mathematical way, how the Moon’s orbit would evolve due to tidal friction, in the late 19th century. He is usually credited with the invention of the modern theory of tidal evolution.

So that’s where the idea came from, but how was it first measured? The answer is quite complicated, but I’ve tried to give the best answer I can, based on a little research into the history of the question.There are three ways for us to actually measure the effects of tidal friction.

* Measure the change in the length of the lunar month over time.
This can be accomplished by examining the thickness of tidal deposits preserved in rocks, called tidal rhythmites, which can be billions of years old, although measurements only exist for rhythmites that are 900 million years old. As far as I can find (I am not a geologist!) these measurements have only been done since the early 90’s.
* Measure the change in the distance between the Earth and the Moon.
This is accomplished in modern times by bouncing lasers off reflectors left on the surface of the Moon by the Apollo astronauts. Less accurate measurements were obtained in the early 70’s.
* Measure the change in the rotational period of the Earth over time.
Nowadays, the rotation of the Earth is measured using the Very Long Baseline Interferometry, a technique using many radio telescopes a great distance apart. With VLBI, the positions of quasars (tiny, distant, radio-bright objects) can be measured very accuarately. Since the rotating Earth carries the antennas along, these measurements can tell us the rotation speed of the Earth very accurately.

However, the change in the Earth’s rotational period was first measured using eclipses, of all things.

There’s no “relative mass”. Mass is a characteristic quantity of a physical system. When we measure the mass of a physical system in a reference system this mass is the same in all reference systems.

This is perhaps why it’s commonly said that “relativity theory” should be better called “theory of invariants”. However, the last name has not caught up people hearts.

Energy, on the other hand, change when we switch reference systems. Some people say that if we imagine that mass is E/c^2 (c is the velocity of light) then it does depend on the system of reference. However, this is not the complete history. There’s nevertheless a number, that these people will call “rest mass”, that is the same in all inertinal reference systems. This “rest mass” is what is defined to be simply “mass”.

Also, I should add, the “rest mass” is what coincides with newtonian definition of mass (which is our common-day experience knowledge of mass), while the other “mass” does not reduce to the Newtonian definition. In Newton’s mechanics mass is never E/c^2.

Yes, at very high energies it’s possile to measure the mass of particle. I’m not an experimental physicist, so I don’t know the details; however, I do know that detectors in high energy experiments usually do have parts of it designed to measure the momentum and energy of a particle. By measuring directly the momentum and energy, mass can be obtained.

I don’t know if that answers your question. As you for sure know, there’s no way we can measure mass of a subatomic particle via gravitation, which is the way we do with macroscopic bodies. We use the law of gravity to measure the mass of a macroscopic bodie because we know the exact relantionship of momentum transfer and the mass. In high energies the same thing is done, not with gravity, but by studying other interactions and by the use of the relantionship of mass, energy and momentum.

The moon revolves around the Earth. The period of revolution of moon around the Earth is same as the period of revolution of the Earth around its axis. If you consider the distance of moon from the Earth and from the SUN, then it is very less in case of Earth. Actually moon revolves around Earth, which in turn revolves around the sun. There are some non Euclidean Geometry involved in this. Gravitation is responsible for creation of such non euclidean space. Remember that planets revolve around the sun in their non euclidean spaces only. The moon also revolves around Earth through a non Euclidean space coz of gravity.

The sun revolves around the Galactic Center. Will you say that why the planets of the sun do not revolve around the center of Galaxy??? As simple as that.

As things coalesce, the star’s gravitational orbit sets that dust and gas to spinning. Any clump that forms within that disk is going to naturally have some sort of rotation.

As the clump collapses on itself it starts spinning faster and faster because of something called conservation of angular momentum. Figure skaters exploit this law when they bring their arms closer to their bodies to speed up their rate of spin. Since gravity pulls inward from all directions equally, the amorphous clump, if massive enough, will eventually become a round planet. Inertia then keeps that planet spinning on its axis unless something occurs to disturb it. The Earth keeps spinning because it was born spinning.

The Earth’s rotation might be as a result of fluid dynamics in the past when the planets were formed and now due to internal activity in Earth’s core.The Moon is supposed to b created from the Earth when it was struck by an extra terrestrial or may be extra solar object.This took place close after planet formation when Earth was in fluid state.The Moon being small in size in having less gravity must have lost all internal activity soon after formation n also slowly stopped rotating around its own axis.This can b compared with the planet Mercury which rotates around its axis every 6 months but revolves around the Sun in 88 Earth days.