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My question is related to the base of cosmology science and theories.

If all what we know about cosmology science is based on our observation from sky and whatever we observe goes back to thousand and million and billion years ago, how can we be sure about some theories like universe expansion. Maybe universe is back to contraction as we talking now?

Topics: Cosmology
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  • Jan 4 2014: They're called theories because they aren't fact yet. It's kind of hard to reach the edge of the universe and observe it's expansion. We come up with theories as approximations to facts, and we go from there. Our current tech is mostly built on theories, and so far we got humans to the moon, rovers on mars etc
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      Jan 4 2014: This is perhaps something that I come across very often that still manages to annoy me, people don't know what theories are, and I'm sorry Jean but neither do you.

      "Theory is a system of ideas intended to explain something, such as a single or collection of fact(s), event(s), or phenomen(a)(on). Typically, a theory is developed through the use of contemplative and rational forms of abstract and generalized thinking."

      http://en.wikipedia.org/wiki/Theory

      A fact is just something that we have data that supports it, a theory is the highest rank that a human idea can have, please understand this. A theory makes predictions about the world based on facts and ideas put together. And every one either stands the tests that it's being put through or fails and is dismissed, this is how our understanding of the world continues to grow.

      Some of the best tested (which means that no one has been able to provide facts that contradict them) theories that have stood the test of time are: Evolution, Gravity and Big Bang. They may fall some time in the distant future, but there is no reason to believe so today, unless you just want to think that you are smarter then all the smart personas that have ever lived collectively.
      • Jan 4 2014: You didn't say anything that I didn't say, you just went more in depth with your description. A theory is not a fact, but is close to being one since they do tests and collect data from observations and come with rational deductions. We used to think that the earth was flat (was a theory), until someone proved otherwise. We used to believe that the earth was the center of the galaxy (was a theory) until the heliocentric model proved it wrong.

        That's why they're approximation to facts, close but not yet. It won't take long before most of our beliefs in Physics get shaken by the next genius to cine up with a breakthrough theory. I'm not saying that a theory is false, it is true to a certain extent, but is not a fact. What do you think I meant in my comment?
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          Jan 4 2014: I think that you are confusing the word theory and fact and the actual implications of it. It's a very common mistake.

          You see a fact is simply "The apple falls to the ground" is does not say anything more than that.

          A theory is "The apple falls to the ground because of gravity", which also makes the prediction that other objects of mass will fall to the ground. A theory is useful for understanding the world, a fact without a theory is nothing as it may be interpreted however people wish.

          Like "The apple falls to the ground" because god pushed it or because the apple wants to be close to the ground. It does not give us any predictions of the world that we can hold true.

          To get theories we must combine a myriad of facts and make and draw conclusions from them that can be tested.

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