When we look at an object that is 1000 light years

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When we look at an object that is 1,000light-years away we see it _________.as it was 1,000 years ago. It takes 1,000years for light to travel 1,000 light-years,so we see the object as it was 1,000 yearsago.Suppose we look at two distant galaxies:Galaxy 1 is twice as far away as Galaxy 2.In that case __________.we are seeing Galaxy 1 as it looked at anearlier time in the history of the universethan Galaxy 2. Remember that thefarther away we look in distance, thefurther back we look in time. BecauseGalaxy 1 is farther away, we are seeing itat a time further into the past, whichmeans earlier in the history of theuniverse.Could we see a galaxy that is 20 billionlight-years away? (Assume that we meana "lookback time" of 20 billion years.)
Suppose we make a scale model of oursolar system, with the Sun the size of agrapefruit. Which of the following bestdescribes what the planets would look
like?You can see this idea clearly in thefigures that relate to the Voyage modelsolar system in Section 1.2 of TheEssential Cosmic Perspective.If you could count stars at a rate of aboutone per second, how long would it taketo count all the stars in the Milky WayGalaxy?Several thousand years. There are atleast 100 billion stars in the Milky WayGalaxy, so it would take at least 100
The total number of stars in theobservable universe is about_________.

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Term
Winter
Professor
MCLEAN

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