You must be able to imagine with interllectual eyes that a ball bounds here and there in a three-dimensional room. This is important for the understanding of the curved space. Three-dimensional thinking is a prerequisite for this. Just imagine the ball starts to fly and hit the wall.
Hereby, it applies to angle of incidence equal angle of falling out. 

Exercise for three-dimensional thinking.
As a practice, one can imagine in its thought the way of the ball in the defined room The ball hits the wall and flies in the same angle at the next wall. 
 
 

Tardoxx: 

Gravitation - attraction
To understand one must make oneself clear that forces result only from the presence of a mass (a planet or a star), which affect other masses. 

Thus, comet appear to us every 76 years which is held in the appearance rhythmus due to the gravitation attraction. 

The comet disappears then again in billions of kilometers and reappears again near the earth atmosphere. comet Gravitation

Geodaete in consideration of the gravitational pull 

A Geodaete is generally the shortest connection between 2 points on the earth's surface - this is called: the great-circle. 

Legend: If we want to go on the earth's surface from the point A to the point B, then the shortest way  would be in a straight line along the yellow line through the earth. Since this is not possible, we obligatorily have to go on the red line on the earth's surface . That would be then under these circumstances the shortest way to the point B. 
The red way is the Geodaete (great - circle) and longer than the yellow way. We go however the red way without noticing , that we are rerouted. In the case of airplanes, the red line is also the shortest way from A to B. 
 
 
 

Beam deflection 
The way of the light beam is curved within the area of a mass (s. picture down beam deflection ). 

Why are light beams also deflected from planets, although light does not possess mass? 

To understand this procedure we have to imagine the following: 

The wooden box in space 

A wooden box floats in weightless space in the proximity of a sun. The box contains void of air - in other words - vacuum. 

 

The wooden box is now accelerated by a rocket with 9.81 meters for each second square in the space. That is the same acceleration due to gravity, which exists on earth. The box contains a small hole at the side panel, into which sunlight breaks in. 

Diagram: Box in space is accelerated by rocket

The beam penetrates through the hole into the box and hits on the other side of the panel and withdraws again from the crate.

While the light flows from one side to the other side of the panel, the box continues to move on its own rate (pushed by the rocket). Thus, the light-beam changes its direction; it is the difference between measurements 
" A " and " B ".  This difference depends on the rate and acceleration of the crate. That was the preface - now to 3 separated cases: 
 
 

Situation: The box is not accelerated by the rocket - the box is weightless in space. The light beam penetrates into the hole; the box does not move, since no acceleration is available, therefore the light beam ist not shifted in this case. The beam penetrates the hole into the box at point "E" and reach point "F" on the opposite wall. Without acceleration by the rocket the measurement  "A" and "B" 
remains the same and the beam in the box is a straight line. 
 
 

The light beam penetrates into the hole, the box moves forward in even rate  and the light beam reach the other side of the panel, this time shifted in its position through the acceleration of the rocket. The beam penetrates the hole in the box at point "E" and reach point "F" un the opposite wall.

This light curvature is for an observer only within the box noticeable, only for those, who are subjected also to the acceleration of the rocket. For an observer, who is found to be outside the box, the light curvature is not available, since the beam flows is an straight path. 

The invasion of the light beam is seen subjective from the box, i.e. the box is fixed steadily by the observer and the movement of the box is not perceived. 
 

The box is namely moving, but the light beam remains on its previous position and moves only in its direction.
Subjectively seen from the light beam, it is still in motion on a straight line and does not bend. The measurement  of "A" is larger than the measurement of "B". The light beam forms a straight line within the box. 
 

In the DIAGRAM
The light beam in the diagram is fixed and the box moves firmly.
The light beam penetrates at the point "E" and hits the wall on the opposite side at point "F". The beam has proceeded as usual an even course, however not for the observer, who is found to be in the box.

Case 3: 

The wooden box in space possess two holes, one in the front ( here flows the beam into the box) and back side (here, the beam withdraws from the box). The distance of the holes can be determined from the rates of the box and the light.

Situation: The box is constantly further accelerated by the rocket and flys with constantly increasing speed in the space. The light beam falls into the hole. The box continues to moves on and the light reach the other side of the panel, shifted from its position through the acceleration. The beam penetrates the hole into thr box at point "E" and reach the opposite side at point "F".

Then the beam leaves the box. The boc still moves on, but the light beam remains on its previous course and moves only in its direction. We see subjectively from the light beam - this means that we are observing only the light beam. On the other way round, we would fix the crate (see case 2). 

Here in the case 3, the beam make back a hyperbola - thus a curve. This is the result of additional acceleration and the rising speed. The observer outside the box sees the light beam however moving further in a straight line without changing its position. 
For the observer within the box is the measurement "A" larger than measurement "B". This light curvature is noticeable only for an observer within the box, namely only for those, who are also subjected to the acceleration of the rocket. For those, who are found to be outside the box, the light curvature is not available, since the beam moves in a straight line. 
 
 

Light beams at the sun 
The same applies to light which is found in the proximity of suns or planets. Even this light beam remains in a straight line for observers outside the box. One must imagine according to the situation to be inside the box, since the curvature is only noticeable within the box.

To the diagram beam deflection: 
In the environment of massive heavenly bodies the space is curved by the gravitation (attraction). That also applies to light beams. From the star at point 4, light beams are transmitted. The star is seen from the earth. However, we mean  that the star is located at point 3. But the beams is rerouted at point 2 and the star is actually located at point 4. All this is due to the curvature of the space. 

The shortest connection between 2 points in curved space is the curve. Even this is a sign, that comets are also found to be moving on the shortest way (an elliptical course) since they move outside the solar system and are able to move back to the sun.

The gravitation curves the space and the space brings the matter in motion. Curvature is actually defined as straight line bend to a curvature (an ellipse). Thit is the shortest way around a sun in a curved space. Planets also take elliptical course. 

Stephen Hawking and Black Holes

Stephen Hawking determines: 
- that we can measure time more exactly than length. - 
- the consequence in relativity theory is due to the fact that there is no absolute time. 
- each observer has his own time measure --> twin experiment
- the Friedmann' model (1922 - Russian physicist and mathematician Alexander Friedmann) is remarkable. The universe is not infinite in the space, however space has no boundaries. 
- the gravitation is so strong that the space curve back in itself so that it turns to look like the surface of a ball. When one constantly moves  on the earth's surface in a certain direction he turns to return back again to his starting point. The infinity is crossed, because the space is curved.
- even the time, which is the fourth dimension, is with finite expansion, but is like a line with two ends or boundaries, a start and an end. If one combines  the  general relativity theory, the uncertainty relation and the quantum theory, then space and time can be finite, without edges or boundaries. 

The question of the contraction 
Info.: Expansion: enlargement of the universe
Contraction: Shrinking of the universe
In the theory one assumes that the universe contracts after the termination of the expansion of time. At this,  the distances between the galaxies and the individual Planet-systems become smaller again. 

One question and two different answers: 

The question is : Why is our universe found to be in the expansion phase and not in that of contraction. 

Professor Stephen Hawking answered hereby (readable in his book "A short history of the time 1988/2001" page 195: "This question can be answered with the weakest anthropic principle. The conditions in the contraction phase would not be suitable for the existence of intelligent natures, who could ask, why does the disorder increases in the same time-direction, in which the universe expands " 

Normal answer: " Since Hubble, we found out through measurements and observations in our surrounding universe  that the universe expands at present and does not contract." 

Why is everything theorized and represented pedantically and accessed with the left hand to the right ear, when seizable observation results are available? 

It is intentionally made complicated, so that not all can understand it.
 
 
 
 

SUMMARY - light-beam curvature (bend):
It happens in different cases:
1) the light-beam curvature (bend) occurs as in the examples with the "box in space". see HERE
However in this case no actual diffraction of ray of light is 
present, but it only appears like this for the observer in the box. For an observer outside the box, the ray of light moves accurately straight on. HERE

2) A light-beam curvature (bend) is caused by the gravitation. 

Both are correct.
 
 
 
 

Background information 
see light beam curvature     and   seeing of human 1 -  part 2
How is an object seen     Entire on curved space-time
 
 

Space curvature 
With the help of the general relativity theory of A. Einstein (1916), one brought the structure and the curvature of the space in connection with the presence and the distribution of the masses in space. In the environment of massive heavenly bodies the space is strongly curved than those in larger distances of such masses. Though, the total curvature of space is caused through the total of all masses and these theories were able to be proven by observation and experiment.  A. Einstein originally believed, an infinite and unlimited universe to be stable. However 1922, A. Friedmann was able to point out that this universe is completely unstable and is determined by expansion and contraction. Few years later, was then also an event proven in the shape of the Hubble - effect which suggests the expansion of the cosmos. 
Off: http://www.die astronomie.de/ Exists NOT in 2005
Space-time curvature
 
 

Stephen Hawking and black holes
Stephen Hawking and Roger Penrose showed that relating to Einstein's relativity theory, both time and space must have begun with the Big Bang and will be terminated in the black holes. A connection to quantum mechanics was able to be made by Hawking.
This is also the basis to the KinkelCyclesTheory. 

Hawking determined: The time is pear-shaped - he means that a Big Bang took place and that the time finds an end, and the relativity theory does not have a global validity anymore in the black holes. Hawking means, that the beginning of the universe must be determined by the same laws, which are valid at all other times. He would have already approached his aim. He means, a law is no law, if it is only effective some times. Referring to Einstein, he said that one cannot curve the space, without including the time. space and time are indissolubly connected to each other. The time seems to go only in one direction. 
"Black holes give radiation" (emit radiation), this is the discovery of Stephen Hawking. General relativity theory and quantum mechanics form the basis of the Hawking thesis. The quantum mechanics shows the product on Planck's quantum principle and Heisenberg's uncertainty relation. 
 

SPACEtime  Timeduration HERE