Chinese scientists find evidence for speed of gravity

[theniubt]

Chinese scientists revealed Wednesday that they have found evidence supporting the hypothesis that gravity travels at the speed of light based on data gleaned from observing Earth tides.

Scientists have been trying to measure the speed of gravity for years through experiments and observations, but few have found valid methods.

By conducting six observations of total and annular solar eclipses, as well as Earth tides, a team headed by Tang Keyun, a researcher with the Institute of Geology and Geophysics under the Chinese Academy of Sciences (CAS), found that the Newtonian Earth tide formula includes a factor related to the propagation of gravity.

"Earth tide" refers to a small change in the Earth's surface caused by the gravity of the moon and sun.

Based on the data, the team, with the participation of the China Earthquake Administration and the University of the CAS, found that gravitational force released from the sun and gravitational force recorded at ground stations on Earth did not travel at the same speed, with the time difference exactly the same as the time it takes for light to travel from the sun to observation stations on Earth.

The scientists admitted that the observation stations are located near oceans, indicating that the influence of ocean tides might have been strong enough to interfere with the results.

Consequently, the team conducted separate observations of Earth tides from two stations in Tibet and Xinjiang, two inland regions that are far away from all four oceans, as well as took measures to filter out other potential disturbances.

By applying the new data to the propagation equation of gravity, the team found that the speed of gravity is about 0.93 to 1.05 times the speed of light with a relative error of about 5 percent, providing the first set of strong evidence showing that gravity travels at the speed of light.

Their findings have been published online in English by German science and technology publishing group Springer.

Printed articles in both Chinese and English will be carried in a January 2013 edition of the Chinese Science Bulletin, according to the CAS Institute of Geology and Geophysics.

Source

Interesting read

 

[neehar]

the source must have published something wrong..gravity is referred by acceleration which is rate of change of speed.the term "speed of gravity is absurd" may be it has to say rate of change of gravity

 

[airuah]

Chinese scientists revealed Wednesday that they have found evidence supporting the hypothesis that gravity travels at the speed of light based on data gleaned from observing Earth tides.


Based on the data, the team, with the participation of the China Earthquake Administration and the University of the CAS, found that gravitational force released from the sun and gravitational force recorded at ground stations on Earth did not travel at the same speed, with the time difference exactly the same as the time it takes for light to travel from the sun to observation stations on Earth.

The scientists admitted that the observation stations are located near oceans, indicating that the influence of ocean tides might have been strong enough to interfere with the results.

Source

i may be wrong but i beleive gravity does not 'travel'. ....... gravity is an attractive force between two objects and it is more when the two objects are closer together.....eg. when you launch a satillite, the taking off of the rocket is the hardest part and a hell lot of energy is used for the purpose but the rest of the journey comparitively uses less effort as the gravitational pull of the earth decreases as the rocket moves away from it (increased distance between the objects). and thus obviously the gravitational force at the surface of the sun will be greater than that at the surface of the earth...and then again this force tends to vary as the earth has an elliptical orbit around the sun and hence the gravitational force also will vary according to the position of the earth in that orbit.

i think the source has totally not understood the finding and has made an absurd article

 

[theniubt]

the source must have published something wrong..gravity is referred by acceleration which is rate of change of speed.the term "speed of gravity is absurd" may be it has to say rate of change of gravity

No, this is not about the typical formula we've learned in general physics, where it measures the acceleration of an object under gravitational force. Instead, this is about how fast can gravity reaches an object.

i may be wrong but i beleive gravity does not 'travel'. ....... gravity is an attractive force between two objects and it is more when the two objects are closer together.....eg. when you launch a satillite, the taking off of the rocket is the hardest part and a hell lot of energy is used for the purpose but the rest of the journey comparitively uses less effort as the gravitational pull of the earth decreases as the rocket moves away from it (increased distance between the objects). and thus obviously the gravitational force at the surface of the sun will be greater than that at the surface of the earth...and then again this force tends to vary as the earth has an elliptical orbit around the sun and hence the gravitational force also will vary according to the position of the earth in that orbit.

i think the source has totally not understood the finding and has made an absurd article

Here are some more articles.

Chinese Scientists Measure Speed of Gravity

Gravity travels at speed of light Chinese research reveals

 

[Srinivas]

the source must have published something wrong..gravity is referred by acceleration which is rate of change of speed.the term "speed of gravity is absurd" may be it has to say rate of change of gravity

No mate "Speed of Gravity" means the "gravitational wave" emitted by a body. Just like an electro magnetic field emitted by a charge.

Here Mass is analogous to Charge , and Gravity wave is analogous to electromagnetic wave.

This concept is related to "Einstein's theory of relativity".

 

[Srinivas]

i may be wrong but i beleive gravity does not 'travel'. ....... gravity is an attractive force between two objects and it is more when the two objects are closer together.....eg. when you launch a satillite, the taking off of the rocket is the hardest part and a hell lot of energy is used for the purpose but the rest of the journey comparitively uses less effort as the gravitational pull of the earth decreases as the rocket moves away from it (increased distance between the objects). and thus obviously the gravitational force at the surface of the sun will be greater than that at the surface of the earth...and then again this force tends to vary as the earth has an elliptical orbit around the sun and hence the gravitational force also will vary according to the position of the earth in that orbit.

i think the source has totally not understood the finding and has made an absurd article

In space as the mass moves so does the gravity associated with it also moves and so the phenomena "Gravity waves".

 

[Not Sure]

i may be wrong but i beleive gravity does not 'travel'. ....... gravity is an attractive force between two objects and it is more when the two objects are closer together.....eg. when you launch a satillite, the taking off of the rocket is the hardest part and a hell lot of energy is used for the purpose but the rest of the journey comparitively uses less effort as the gravitational pull of the earth decreases as the rocket moves away from it (increased distance between the objects). and thus obviously the gravitational force at the surface of the sun will be greater than that at the surface of the earth...and then again this force tends to vary as the earth has an elliptical orbit around the sun and hence the gravitational force also will vary according to the position of the earth in that orbit.

i think the source has totally not understood the finding and has made an absurd article

The article is perfectly fine, however, it does not provide enough detail to make for a critical reading.

Speed of gravity is the distance per time it takes for a particular massive object to affect another mass particle with its gravitational force.

Remember, speed (<delta>distance/<delta>time) of gravitational force is not related to the magnitude of the gravitational force which is a force (distance/time^2) and not speed.

Taking the both as same would be akin to saying that a Car is equal to 100 mph. Taking Car as the gravitational force, and 100 mph as speed of that force would be the right approach.

While electromagnetic force has been measured to travel at the speed of light (light itself is electromagnetic radiation carrying the force with it), the nature and speed at which gravitational force travels have not been fully understood.

What I cannot figure out from the article is how they managed to measure the gravitational force exiting Sun at a particular time.

 

[shuttler]

the source must have published something wrong..gravity is referred by acceleration which is rate of change of speed.the term "speed of gravity is absurd" may be it has to say rate of change of gravity

a little learning is a dangerous thing!

This gives you and other ignoranmus who has made stupid accusations an idea of what the article is about:

Speed_of_gravity

Their findings have been published online in English by German science and technology publishing group Springer.

Printed articles in both Chinese and English will be carried in a January 2013 edition of the Chinese Science Bulletin, according to the CAS Institute of Geology and Geophysics.

the above links by the OP are just very basic introductions. Anyone who is serious in knowing the full process of experiment and the result has to read the paper carried by the German publisher or wait until Jan 2013 release on Chinese Science Bulletin!

Great Discovery nonetheless!

 

[airuah]

The article is perfectly fine, however, it does not provide enough detail to make for a critical reading.

Speed of gravity is the distance per time it takes for a particular massive object to affect another mass particle with its gravitational force.

Remember, speed (<delta>distance/<delta>time) of gravitational force is not related to the magnitude of the gravitational force which is a force (distance/time^2) and not speed.

Taking the both as same would be akin to saying that a Car is equal to 100 mph. Taking Car as the gravitational force, and 100 mph as speed of that force would be the right approach.

While electromagnetic force has been measured to travel at the speed of light (light itself is electromagnetic radiation carrying the force with it), the nature and speed at which gravitational force travels have not been fully understood.

What I cannot figure out from the article is how they managed to measure the gravitational force exiting Sun at a particular time.

thanks for the explanation....

just one question though......if

a)the earth revolves around the sun in a elliptical orbit(i.e its nearest to the sun at one time and away at the other-which is responsible for seasons)

and

b)the earth revolves around the sun because of gravitational pull of the sun


does that mean that the gravitational pull of the sun is kind of different at different periods (that is it varies at regular intervals like every few months causing the elliptical orbit and thus the seasons))

 

[Srinivas]

The article is perfectly fine, however, it does not provide enough detail to make for a critical reading.

Speed of gravity is the distance per time it takes for a particular massive object to affect another mass particle with its gravitational force.

Remember, speed (<delta>distance/<delta>time) of gravitational force is not related to the magnitude of the gravitational force which is a force (distance/time^2) and not speed.

Taking the both as same would be akin to saying that a Car is equal to 100 mph. Taking Car as the gravitational force, and 100 mph as speed of that force would be the right approach.

While electromagnetic force has been measured to travel at the speed of light (light itself is electromagnetic radiation carrying the force with it), the nature and speed at which gravitational force travels have not been fully understood.

What I cannot figure out from the article is how they managed to measure the gravitational force exiting Sun at a particular time.

You are true

So, in theory, we know that the speed of gravity should be the same as the speed of light. But the Sun&#8217;s force of gravity out here, by us, is far too weak to measure this effect. In fact, it gets really hard to measure, because if something moves at a constant velocity in a constant gravitational field, there&#8217;s no observable affect at all. What we&#8217;d want, ideally, is a system that has an object moving with a changing velocity through a changing gravitational field. What would that take?

Something intense, like two neutron stars orbiting each other extremely close together! Occasionally, we get very lucky, and a neutron star emits very regular blips of light, pulsing with incredible precision: this makes it a pulsar! If one of these neutron stars is a pulsar aimed at us, we can test whether gravity moves at the speed of light or not!

Incredibly enough, we&#8217;ve discovered multiple independent binary pulsars with this exact configuration!

Not only is the gravitational source (star #1) moving, but the other object (star #2) is changing its velocity, as it changes its direction in orbit around the gravitational source! Remarkably, this effect causes the orbit to ever-so-slowly decay, which leads to time changes in the pulses!

The predictions from Einstein&#8217;s theory of gravity are incredibly sensitive to the speed of light, so much so that even from the first binary pulsar system, PSR 1913+16 (or the Hulse-Taylor binary), we have constrained the speed of gravity to be equal to the speed of light with an error of less than 1%!

While we&#8217;d love to be able to detect these gravitational waves directly, rather than make an indirect measurement, we&#8217;re likely going to have to wait until close to 2030. Why? We&#8217;ll need to have LISA up and running, where it&#8217;s capable of detecting a system like this and directly measuring the speed of gravitational radiation.

But until then, indirect measurements of very rare pulsar systems like this give us the tightest constraints, and tell us that the speed of gravity is between 2.993 x 108 and 3.003 x 108 meters per second, which is an amazing confirmation of general relativity and a terrible difficulty for alternative theories of gravity! (Sorry, Newton!) And now you know not only what the speed of gravity is, but where to look to figure it out!

What is the Speed of Gravity? &#8211; Starts With A Bang

 

[KRAIT]

So gravitons also travel with speed of light. Does it shows dual nature ?

What is the percentage of water in Human body ?

Gravity of moon affects water on earth. These gravity waves from other planets can affect brain ?

Also when a baby is born, the brain is still not complete solid. S when he/she takes birth, the water and chemical, blood etc. experiences effect of gravity waves from the planets.

This has been a matter of discussion among scientist community to introduce Astrology as field of science for decades.

 

[Srinivas]

So gravitons also travel with speed of light. Does it shows dual nature ?

To explain the properties of Light two theories are proposed

1) Electromagnetic theory

2) Quantum theory

But there is still lot of work left to evaluate the dual nature of the light "Stephen Hawkings" Tried to converge the two theories.


Research on "Gravitational waves" is still in primitive stage.

 

[KRAIT]

To explain the properties of Light two theories are proposed
1) Electromagnetic theory
2) Quantum theory
But there is still lot of work left to evaluate the dual nature of the light "Stephen Hawkings" Tried to converge the two theories.
Research on "Gravitational waves" is still in primitive stage.

Actually electromagnetic theory is essentially included in quantum theory. Double split experiment explains the wave nature.

The other theory is Particle nature, where photons are considered. Photoelectric effect explains the particle nature.

 

[Not Sure]

thanks for the explanation....

just one question though......if

a)the earth revolves around the sun in a elliptical orbit(i.e its nearest to the sun at one time and away at the other-which is responsible for seasons)

and

b)the earth revolves around the sun because of gravitational pull of the sun


does that mean that the gravitational pull of the sun is kind of different at different periods (that is it varies at regular intervals like every few months causing the elliptical orbit and thus the seasons))

No, it does not mean that Sun's gravitational force fluctuates. Its gravitational force remains roughly constant, and has been very negligibly reducing at the same rate at which it loses its mass in the form of radiation and solar ejections.

The elliptical orbit of the Earth is because of two forces acting on it simultaneously. Its centrifugal force driving the Earth in a particular direction, and Sun's gravity pulling it back.

When the Sun's gravitational force pulls the Earth back, the speed of Earth increases, and works against the gravity of Sun.

For the Sun's constant gravity, it takes more time for Sun to pull down a speeding Earth back, and by that time the Earth has reached a farther distance in a particular direction resulting an elliptical orbit.

It would help to understand if you throw a marble in a semi-spherical bowl. The momentum of the marble takes in on particular direction at high speed, and by the time gravity of Earth stops its momentum, it has reached a certain high point in that direction. When the marble comes down, it comes in an elliptical fashion.

So depending on the force of the marble, either the marble will soon go out of the bowl, or it will eventually slow down and end up in the bottom of the bowl. Same will happen with Earth too. Moon, on the other hand, has been going away from Earth. 3 billion years ago it was 15,000 kilometers away from Earth. Now it is 300,000 kms away. One day, its momentum will overcome the gravitational pull of Earth and it will escape.




There are some lectures given by Richard Feynmann known as The Character of Physical Law. They are video lectures targeted at those who do not have a background in math and physics.

These lectures are freely available, and I am sure you can find them on YouTube.com. Since they are in simple language given by one of the smartest physicists of the last century, you will find them very helpful, esp regarding the concept of Center of Gravity, which basically remains unchanged despite all the movements taking place in this Universe.

To go for something more exhaustive, you may also look for the freely available lectures given by Professor Ramamurti Shankar known as Yale OYC Fundamental of Physics (Part I and Part II, both).

They are courses in Physics and include almost all the subjects in physics you may be curious about. Since they too are meant for those who do not possess a solid background in physics, they will be very helpful to you. In my opinion, if you learn everything provided in those videos, your level of knowledge will be no less than that of a Ph.D. from a reputed University!

 

[Srinivas]

Actually electromagnetic theory is essentially included in quantum theory. Double split experiment explains the wave nature.

The other theory is Particle nature, where photons are considered. Photoelectric effect explains the particle nature.

No Krait
Quantum theory is related to particle nature of light,

Though most of the properties of light can be understood by considering it as a wave, some of the properties of light can only be explained by using particle (corpuscular) nature of it. Newton considered light to possess particle nature. In the year 1900, in order to explain black body radiations, Max Planck proposed Quantum theory by considering light to possess particle nature.