Which of the following best explains why the night sky is dark? a. the universe has not always looked the way it looks today. b. the universe is not infinite in space. c. the distribution of matter in the universe is not uniform on very large scales.

The universe is not infinite in space

This question is known as the Olbers' Paradox, who in the 19th century posed a question similar to the following:

If the universe where we live is infinite, static, and uniformly populated with stars (similar to the distribution of trees in an immense forest where we would find a tree in whatever direction we observe), which have eternally existed; the light of all of them would intensely illuminate any point of space.

That is to say, we should see stars in any direction, no matter how far away they are and the celestial vault should be exaggeratedly bright.

But this is not the case, the night sky is dark and the universe too.

Well, although the standard cosmological model of the universe suggests that it is infinite, the observable universe is not.

In other words, the universe is finite.

Then, in a universe of limited size, even having a great quantity of stars and galaxies, all of them would not be enough to illuminate all the space.

In addition, there is another important point: Not only the universe is finite, also its age is; this means it had a beginning.

Hence, having a finite observable universe that is continuously expanding, distant stars and galaxies move away even further.

So, when we look at a star that is 1 million light years away, we are seeing the star as it was seen 1 million years ago.

This means that the amount of light that comes to us from distant stars decreases all the time.

Therefore the light from the most distant stars has not yet had enough time to reach us.

It is B.

Explanation:

wire in brush may conduct electricity from cell to drill and vice versa electrc shock possible

-first use of geothermal energy occurred more than 10,000 years ago in north america by american paleo-indians

-the first industrial use of geothermal energy began near pisa, italy in late 18th century

-in 1904, italian scientist piero ginori conti invented the first geothermal electric power plant in which steam was used to generate the power

-with the above experiment, the first geothermal plant in usa started in 1922 with a capacity of 250 kilowatts

-however, in 1946 first ground-source geothermal heat pump installed at commonwealth building in portland, oregon

-during the 1960’s, pacific gas and electric began operation of first large scale geothermal power plant in san francisco, producing 11 megawatts

-in 1973, when oil crisis began many countries began looking for renewable energy sources and by 1980’s geothermal heat pumps (ghp) started gaining popularity in order to reduce heating and cooling costs

-as effect of climate change started showing results, governments of various countries joined hands to fight against it, for which kyoto protocol was signed in japan in 1997, laid out emission targets for rich countries and required that they transfer funds and technology to developing countries, 184 countries have ratified it

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