How Do We Measure the Size of the Galaxy with Limited Telescope Scans?

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SUMMARY

The discussion centers on the measurement of the Milky Way's size, specifically its estimated diameter of approximately 100,000 light years, despite only detailed scans covering about 100 light years. Michio Kaku, in a video regarding the SETI (Search for Extra-Terrestrial Intelligence) project, clarifies that the limited scanning refers specifically to radio telescopes searching for extraterrestrial signals. Additionally, the Hubble Space Telescope has captured optical images of galaxies billions of light years away, providing further context to our understanding of galactic dimensions.

PREREQUISITES
  • Understanding of astronomical measurement techniques
  • Familiarity with radio telescopes and their applications
  • Knowledge of the Hubble Space Telescope's capabilities
  • Basic concepts of galactic structure and distance measurement
NEXT STEPS
  • Research the principles of radio astronomy and its role in the SETI project
  • Explore the capabilities and findings of the Hubble Space Telescope
  • Learn about methods for measuring astronomical distances, such as parallax and redshift
  • Investigate the structure of the Milky Way and its components
USEFUL FOR

Astronomers, astrophysics students, science communicators, and anyone interested in the methods of measuring galactic dimensions and the search for extraterrestrial life.

flyingpig
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Homework Statement



It is said that telescopes have found that our galaxy is about a hundred thousand light years across. It is also said that our telescopes have only scanned a hundred light years of the galaxy.

I am just quoting from this video:

So my question is, how can we know that the galaxy is a hundred thousand light years across when we've only scanned a hundred light years
 
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Hello flyingpig.

As usual, details are important.

In that video, Michio Kaku is speaking of the SETI (Search for Extra-Terrestrial Intelligence) project. Early in the video he says that we have only scanned perhaps 100 light years from Earth in some detail. What he refers to is scanning with radio telescopes for the purpose of detecting radio signals from some form of intelligent life.

He does not say that telescopes have only scanned 100 light years from earth.

The Hubble telescope has recorded optical images from galaxies which are billions of light years away.
 

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