Space Exploration/Space Question

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Question
Good day
I recently read that there are more than 100 billion galaxies in the universe.
1. How and what method(s) do scientist use to calculate this figure?
2. How can a scientist state with confidence that there this amount when we cannot access other galaxies? Also how do scientist know where the universe ends and what if where we think it ends, it really does not end or what if the vast magnitude that we perceive is nothing but an illusion and it is not as large as we think it is
3. What really exists on these galaxies and how can we know?

Sunil Mahabir
Miramar / Pembroke Pines,Florida

Answer
Hi, thanks for writing, 1. a survey is taken of a small sky area and approximate distances, then multiplied by the total area of the known universe to get an approximate figure. 2. we assume that the method used to calculate distance/size is correct, but, of course, we will never know with certainty it is correct. Due to dark energy, we cannot and never will see some of the universe. 3. we can never really know, but the closer galaxies give us a sample of the star/nebula content, and the closer stars give us a sample of the potential planet content.  Write anytime!

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Kenneth Renshaw

Expertise

Answer basic space flight questions, research info on specific space flights. Answer questions on astronomy

Experience

Amateur astronomer and avid astronomy/space flight fan for 31 years.

Organizations
Official NASA/JPL Solar System Ambassador for Arkansas and Missouri (one of about 300 nationwide). (http://www2.jpl.nasa.gov/ambassador/profiles/Kenneth_Renshaw.htm)

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Numerous local and area newspapers.

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AA/BME/MME

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