ISP 205: Visions of the Universe - Physics & Astronomy
ISP 205: Visions of the Universe - Physics & Astronomy
ISP 205: Visions of the Universe - Physics & Astronomy
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3) How can we know what <strong>the</strong> universewas like in <strong>the</strong> past?• Light travels at a finite speed (300,000 km/s).DestinationMoonSunSiriusAndromeda GalaxyLight travel time1 second8 minutes8 years2.5 million years• Thus, we see objects as <strong>the</strong>y were in <strong>the</strong> past:The far<strong>the</strong>r away we look in distance,<strong>the</strong> fur<strong>the</strong>r back we look in time.© 2005 Pearson Education Inc.,publishing as Addison-Wesley