mankind since ancient times to think about how the world is arranged.Why is the grass grows, why the sun shines, why can not we fly ... The latter, incidentally, is always particularly interested in people.We now know that the cause of everything - gravity.What is it and why this phenomenon is so important on the scale of the universe, we are reviewing today.
Introduction
Researchers found that all massive bodies experience a mutual attraction to each other.Later it turned out that this mysterious force causes the movement of the heavenly bodies and their constant orbits.The very same theory of gravitation formulated by Isaac Newton a genius whose hypothesis predetermined the development of physics for many centuries to come.He developed and continued (albeit in a completely different direction) is the scientist Albert Einstein - is one of the greatest minds of the last century.
For centuries, scientists have observed the attraction, trying to understand and measure it.Finally, in the last few decades is at the service of humanity (in some sense, of course), even such a thing as gravity.What is it, what is the definition of this term in modern science?
scientific definition
If you study the works of ancient thinkers, it is possible to find out that the Latin word «gravitas» means "burden", "attraction".Today, scientists have called the universal and permanent interaction between material bodies.If this force is relatively weak, and acts only on objects that are moving much slower speed of light, it is applicable to them Newton's theory.If it is not the case, you should use the findings of Einstein.
Outset: Currently, the nature of gravity is not fully understood in principle.What is it, we are not yet fully present.
theories of Newton and Einstein
According to the classical doctrine of Isaac Newton, all bodies attract each other with a force directly proportional to their mass, is inversely proportional to the square of the distance that lies between them.Einstein argued that the attraction between objects is shown in the case of the curvature of space and time (and the curvature of space is only possible if it has the matter).
thought this was very deep, but modern research has shown her some inaccuracy.Today, it is believed that gravity bends space only space: time, you can slow down and even stop, but the reality is changing the shape of a temporary matter theory has not been confirmed.But because classical Einstein equation does not provide even a chance that the area will continue to affect matter on a magnetic field.
The more we know the law of gravity (gravity), the mathematical expression of which is owned as time Newton:
\ [F = γ \ frac [-1.2] {m_1 m_2} {r ^ 2} \]
Underγ refers to the gravitational constant (sometimes the symbol G), the value of which is equal to 6,67545 × 10-11 m³ / (kg · s²).
interaction between elementary particles
incredible complexity of the space surrounding us is largely due to an infinite number of elementary particles.Between them, there are also various interactions at those levels about which we can only guess.However, all kinds of interactions of elementary particles among themselves vary greatly in strength.
most powerful of all known forces bind the components of the atomic nucleus.To separate them, you need to spend a truly colossal amount of energy.As the electrons, they are "tied" to the kernel only ordinary electromagnetic interaction.To stop it, sometimes quite the energy that appears as a result of the normal chemical reaction.Gravity is (what it is, you already know) in the form of atoms and subatomic particles is the easiest kind of interaction.
gravitational field in this case is so weak that it is difficult to imagine.Oddly enough, but the movement of the heavenly bodies, whose weight sometimes impossible to imagine, "follow" those.All this is possible thanks to two features of gravity, which are particularly pronounced in the case of large physical bodies:
- Unlike atomic force gravitational attraction more noticeable at a distance from the object.Thus, the Earth's gravity keeps in his field, even the moon, and a similar strength of Jupiter's orbit easily supports multiple satellites, the mass of each of which is comparable to the Earth!
- Moreover, it always ensures the attraction between objects, the distance, this force is weakened at low speed.
formation of a more or less coherent theory of gravity is relatively recent, and it is the result of centuries of observation of the movement of the planets and other celestial bodies.The problem essentially easier by the fact that they all move in a vacuum, where there is simply no other possible interactions.Galileo and Kepler - two prominent astronomer of the time, its most valuable observations have helped to pave the way for new discoveries.
But the great Isaac Newton was able to establish the first theory of gravity, and express it in mathematical mapping.It was the first law of gravitation, mathematical mapping of which is given above.
conclusions of Newton and some of his predecessors
Unlike other physical phenomena that exist in the world around us, gravity manifests itself always and everywhere.It should be understood that the term "zero gravity", which often occurs in the pseudo-scientific circles, it is not correct that even the weightlessness in space does not mean that a person or a spacecraft is not valid attraction of a massive object.
In addition, all material bodies have a certain weight, expressed as a force that was applied to them, and the acceleration produced by the impact.
Thus, the force of gravity is proportional to the mass of objects.Numerically, they can be expressed receiving the product of the masses of both of the bodies.This force is strictly obeys the inverse square of the distance depending on between objects.All other interaction quite different depending on the distance between the two bodies.
Mass as a cornerstone of
array of objects became particularly controversial point, which is built around the entire modern theory of gravitation and Einstein's relativity.If you recall Newton's second law, you probably know that the weight is a mandatory feature of any physical material body.It shows how the object will behave in case of application of force thereto, regardless of its origin.
Since all the body (according to Newton) when exposed to an external force accelerated, that the mass determines how big is this acceleration.Consider a clear example.Imagine a scooter and a bus, if applied to them exactly the same effect, they reached different rates for unequal time.All of this is explained by the theory of gravitation.
What is the relationship of weight and gravity?
Speaking of gravity, the mass of this phenomenon plays a role completely opposite to that which it plays in relation to force and acceleration of the object.That it is the primary source of attraction.If you take a look at the two bodies and the force with which they attract a third object, which is located at equal distances from the first two, the ratio of forces is equal to the ratio of the masses of the first two objects.Thus, the attractive force is directly proportional to body weight.
If we consider Newton's third law, we can make sure it says exactly the same thing.The gravitational force which acts on the two bodies disposed at an equal distance from the source of attraction is directly dependent on the mass of data objects.In everyday life we are talking about the force with which a body is attracted to the surface of the planet, as its title.
sum up.Thus, the weight is closely linked to the power and acceleration.At the same time, it determines the force which will act on the body attraction.
Features acceleration of bodies in a gravitational field
This amazing duality is the reason that in the same gravitational field of acceleration quite different objects is equal.Suppose that we have two bodies.Assign one of them a lot to z, and another - Z. Both objects are thrown on the ground, where the free fall.
How is the ratio of the force of gravity?It shows a simple mathematical formula - z / Z.Here are just accelerating, they receive as a result of the force of gravity will be exactly the same.Simply put, the acceleration that the body has a gravitational field does not depend on its properties.
What determines the acceleration in the case described?
It depends only (!) Of the weight of objects that create this field, as well as their attitude.The dual role of the mass and acceleration equal to different bodies in a gravitational field already discovered some time ago.These phenomena have the following title: "The principle of equivalence."This term emphasizes once again that the acceleration and inertia often equivalent (to a certain extent, of course).
about the importance of the value of G
From school physics course, we remember that the acceleration of gravity at the surface of our planet (Earth's gravity) is 10 m / sek.² (9.8 of course, but for simplicity of calculations this value is used).Thus, without taking into account air resistance (at a substantial height when the distance of incidence), then the effect obtained when the body gets incremented acceleration of 10 m / sec.every second.So, a book that has fallen from the second floor of the house, at the end of its mission will be moving at a speed of 30-40 m / s.Simply put, 10 m / s - this is the "speed" of gravity within the Earth.
acceleration due to gravity in the physics literature indicated by the letter «g».Since the shape of the Earth to a certain extent more like a mandarin, than the ball, the value of this quantity is not in all of its areas is the same.Thus, the acceleration at the poles above, and on the tops of high mountains, it becomes smaller.
Even in the mining industry a significant role is played by gravity.The physics of this phenomenon sometimes saves a lot of time.So, geologists are particularly interested in a perfectly precise definition of g, because it allows you to explore the exceptional accuracy and finding mineral deposits.By the way, it looks like the formula of gravitation, in which we examined the value plays a role?Here it is:
F = G x M1xM2 / R2
Note!In this case, the formula implies gravity G «gravitational constant", the significance of which we have already given above.
At the time, Newton formulated the principles enunciated above.He knew, and the unity and universality of the gravitational force, but all aspects of this phenomenon, he could not describe.That honor fell to Albert Einstein, who was able to explain the principle of equivalence.That's it mankind owes the modern understanding of the nature of space-time continuum.
theory of relativity, Albert Einstein's work
In the time of Isaac Newton believed that the starting point can be represented in the form of some tough "rods", by which determines the position of the body in the spatial coordinate system.At the same time it was assumed that all observers note that these coordinates will be in the same space of time.In those years, this situation was considered so obvious that no attempt was made to challenge or complement it.This is understandable, because within our planet no deviation in the rule no.
Einstein proved that the accuracy of the measurement would be really significant if a hypothetical clock is moving much slower speed of light.Simply put, if one observer moving slower than the speed of light, will follow the two events, they happen for him at the same time.Accordingly, for the second observer?whose speed is the same or more events may occur at different times.
But the force of gravity related to the theory of relativity?Let us open the issue in detail.
connection between relativity and gravitational forces
in recent years made a huge number of discoveries in the field of subatomic particles.A growing conviction that we are about to find the final particle beyond which our world can not be crushed.It becomes more insistent need to know how affect the tiny "bricks" of our universe are fundamental forces that have been opened in the last century, and even earlier.Especially sad that the very nature of gravity has not yet been explained.
That is why, after Einstein, who established the "incapacity" of classical Newtonian mechanics in the area under consideration, the researchers focused on a complete rethinking of earlier data.Largely undergone revision and gravity itself.What is it at the level of subatomic particles?Does it have at least some value in this amazing multi-dimensional world?
simple solution?
first many assumed that the discrepancy Newton's gravitation and the theory of relativity can be explained quite simply an analogy from the field of electrodynamics.It would be possible to assume that the gravitational field spreads like a magnetic field, then it is possible to declare a "mediator" in the interactions of celestial bodies, explaining the many inconsistencies of the old and the new theory.The fact is that then it would be considered relative propagation velocity forces were significantly lower light.Since gravity and time bound?
In principle, Einstein himself almost got to build a relativistic theory is based on such views, that's just one thing prevented his intentions.None of the scientists of that time did not have any information at all which would could help determine the "speed" of gravity.But there was a lot of information related to the movement of large masses.As you know, they just did is a recognized source of a powerful gravitational fields.
Large speed greatly affect body weight, and it did not like the interaction speed and charge.The higher the speed, the greater the weight.The problem is that the latter is automatically would become infinite if the motion speed of light or greater.So Einstein concluded that there is no gravity, and tensor field to describe which should be used much more variable.
His followers came to the conclusion that the gravity and practically not related.The fact that this very tensor field can act on the space, but at the time of impact can not.However, the brilliant physicist Stephen Hawking modernity there is another point of view.But that's another story ...
