How to measure distances of stars? -4 - Expanding Universe **Subscribe to get notified of new videos and support.
Until recent ages, many philosophers and scientists believed that the universe to be infinite.
The ancient Greeks recognized that it was difficult to imagine what an infinite universe might look like.
But they also wondered that if the universe were finite, and you stuck out your hand at the edge, where would your hand go?
But, when Isaac Newton discovered the law of gravity, he realized that gravity is always attractive. Every object in the universe attracts every other object.
If the universe truly were finite, the attractive forces of all the objects in the universe should have caused the entire universe to collapse on itself.
He realize that, if the universe is finite, it must be collapsing or expanding.
When Einstein developed his theory of gravity in the General Theory of Relativity, he thought he ran into the same problem that Newton did:
His equations said that the universe should be either expanding or collapsing, yet he assumed that the universe was static.
In 1920s Edwin Hubble, working at the Carnegie Observatories in Pasadena, California, measured the redshifts of a number of distant galaxies.
This phenomenon called Doppler effect; gives the same result for sound, radio waves and light.
For example, while the sound of an oncoming train is heard more squeal, sound is even more deep as the train moves away.
This is due to the compression of sound waves coming from the approaching train.
This is observed in the light spectra as reddening and blue shift. While the spectrum of the divergent objects glides red, the spectrum of the approaching objects shifts to blue.
Although it was thought that these galaxies were moving away from us at first, it was concluded that all the distant galaxies in all directions were moved away from us, and that it was due to the expansion of space.
All objects, except connected to each other by fundamental interaction (such as gravitation), moves away from each other due to the expansion of space.
However, clusters of interconnected galaxies are not affected by this situation like Andromeda and our galaxy.
Or, our atoms, connected each other by fundamental interactions, don't take apart.
Let's think we are making cakes with raisins. The distance between the raisins increases as the cake mix swelling, but the size of the raisins does not change. The raisins in the analogy are galaxies and the cake mix is space.
As the universe expands, the diameter of the galaxies does not change, as in the example. Only the space texture is expanding.
The expansion rate of the universe is expressed by a coefficient called the Hubble constant, which is constantly updated with observations.
This value is calculated as 65-75 km/s/Mpc according to the last measurements.
In other words, this value, calculated as 65-75 km/s per million parsec, indicates that distant galaxies are moving away from us at a higher rate than the relatively close galaxies, ie the distant space expands faster.
This coefficient also allows us to calculate the age of the universe. This is called the Hubble time.
The age of the universe is estimated to be approximately 14 billion years if the coefficient value determined by the last WMAP measurements is 71 km/s/Mpc.
Redshift is also used to measure the distance of galaxies. Because the greater the value of the redshift means greater distance.
The distances calculated using red shift with some distant objects are as follows ...
Pinwheel Galaxy - 21.9 million light years away.
NGC 1512 Galaxy - 37.87 million light years away.
NGC 1510 Galaxy - 38.65 million light years away.
LEDA 36252 (Kiso 5639) Galaxy - 112.2 million light years away.
Arp 142 Galaxies - 353.78 million light years away.
Abell 2218 Galaxy Cluster - 2.54 billion light years away.
Abel 1689 Galaxy Clusters - 2.67 billion light years away.
HE0450-2958 Quasar - 3.54 billion light years away.
Abell 370 Galaxy Cluster - 5.39 billion light years away.
3C 279 Quasar - 7.75 billion light years away.
3C 186 Quasar - 15.41 billion light years away.
ULAS J1120+0641 Quasar - 102 billion light years away. It is the most distant object ever observed.
It is seen that the velocity of the distant celestial bodies are faster than light. However, it is universe's expanding rate which faster than light.
Because of the texture of space have not any mass, it is thought that it can expand faster than light. Therefore, there is no contradictory situation with our physics rules.
What about the fate of the universe!
The three possible types of expanding universes are called open, flat, and closed universes.
If the universe were closed, it would eventually stop expanding and recollapse on itself, possibly leading to another big bang.
If the universe were flat, it would also expand forever, but the expansion rate would slow to zero after an infinite amount of time.
If the universe were open, it would expand forever. It is called big freeze scenario.
When things get farther apart, they will become colder, because their atoms will no longer interact and cause fission and fusion, which create explosions, and thus energy and heat.
A simple analogy to understand these three types of universes is to consider a spaceship launched from the surface of the Earth.
If the spaceship does not have enough speed to escape the Earth's gravity, it will eventually fall back to Earth. This is analogous with a closed universe that recollapses.
If the spaceship is given enough speed so that it has just enough energy to escape, then at an infinite distance away from the Earth, it will come to a stop (this is the flat universe).
And lastly, if the ship is launched with more than enough energy to escape, it will always have some speed, even when it is an infinite distance away (the open universe).
Scientists have determined that as a result of their work, the universe does not always expand at the same rate.
It should be expanded at a speed that is much faster than the speed of light in the period, and that the expansion rate is increasing now.
Although it cannot be determined how changed the universe's expanding rate in time, it is estimated that the current size of the universe should be about 95 billion light years.
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