The star sirius is about 8 . 1 × 10 13 km from the earth. Assuming that light travels at a speed of 3 . 0 × 10 5 km per second, find how long will the light from sirius take to reach the earth?

The distance of star sirius from the earth is 8 . 1 × 10 13 km. The light travels at a speed of 3 . 0 × 10 5 km/sec. If a quantity is written as the product of a power of 10 and a number that is greater than or equal to 1 and less than 10 , then the quantity is said to be in scientific notation. So, the time will take to cover distance = d i s t a n c e s p e e d = 8 . 1 × 10 13 k m 3 .0 × 10 5 km / sec = 8 . 1 × 10 13 km 3 .0 × 10 5 km / sec = 8 . 1 3 . 0 × 10 13 10 5 sec = 2 . 7 × 10 8 sec Therefore, the time taken to cover the distance of 8 . 1 × 10 13 km is 2 . 7 × 10 8 sec .

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The star sirius is about $8.1 \times 10^{13}$ km from the earth. Assuming that light travels at a speed of $3.0 \times 10^{5}$ km per second, find how long will the light from sirius take to reach the earth?