# Light from the Sun takes 8 minutes to reach Earth. How long does it take to reach Mars?

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What is the Given & Unkown(s):

8 minutes (light to reach the sun)

t=?

Approprite formula:

?

Conversion of the formula in order to determine your unknown:

?

Inserting numbers:

8 min/ 1 Au = t/ 1.52 AU

t= (8 min x 1.52 AU)/ 1 AU = 12.2 min

Units:

?

(I don't know what to put for those 3 parts)

What is the Given & Unkown(s):

8 minutes (light to reach the sun)

t=?

Approprite formula:

?

Conversion of the formula in order to determine your unknown:

?

Inserting numbers:

8 min/ 1 Au = t/ 1.52 AU

t= (8 min x 1.52 AU)/ 1 AU = 12.2 min

Units:

?

(I don't know what to put for those 3 parts)

##### 1 Answer

Based on speed of light (300,000 km/s): ca. 12 min. 40 sec.

Based on 8 min. from Sun to Earth: ca. 12 min

#### Explanation:

To compute the time, we need the following data:

Speed of light in vacuum:

(More exactly 299 792 458 m/s, but for our purposes the round figure of 300 000 fits nicely)

Distance from Sun to Mars: 228 000 000 km.

(Distance from Sun to Earth:

The only two items we need, are really the speed of light and the distance it has to travel, as our calculation then becomes:

time in seconds = Distance / speed of light

=

=

If we instead base our computation on the data we have been given, i.e. that the light uses 8 min. = 480 sek. to reach the earth, we must use the ration between Earth's distance and Mars' distance to the Sun, i.e.

=