1
00:00:01,701 --> 00:00:06,673
(MUSIC)

2
00:00:06,673 --> 00:00:08,908
Joan Cartan-Hansen, Host: We 
measure a day by how long it

3
00:00:08,908 --> 00:00:11,678
takes for the Earth to turn 
once on its axis, and a year

4
00:00:11,678 --> 00:00:15,148
by how long it takes the Earth 
to revolve around the Sun.

5
00:00:15,148 --> 00:00:18,918
A day on Earth is about 24 
hours and a year is about 365

6
00:00:18,918 --> 00:00:20,019
days.

7
00:00:20,019 --> 00:00:22,889
But how long is a day or a 
year on the other planets in

8
00:00:22,889 --> 00:00:24,691
our solar system?

9
00:00:24,691 --> 00:00:29,129
A day on Mercury lasts 1,407 
Earth hours but a year is only

10
00:00:29,129 --> 00:00:30,663
88 Earth days.

11
00:00:30,663 --> 00:00:33,900
That's because Mercury rotates 
slowly on its axis but

12
00:00:33,900 --> 00:00:36,469
revolves quickly around the 
Sun because it is so close to

13
00:00:36,469 --> 00:00:38,004
the Sun.

14
00:00:38,004 --> 00:00:40,573
A day on Mars is only 37 
minutes longer than a day on

15
00:00:40,573 --> 00:00:41,508
Earth.

16
00:00:41,508 --> 00:00:46,045
But a year on Mars is much 
longer at 687 Earth days.

17
00:00:46,045 --> 00:00:48,348
A day on Jupiter is the 
shortest in the solar system

18
00:00:48,348 --> 00:00:49,849
at only 10 hours.

19
00:00:49,849 --> 00:00:54,687
And a year on Neptune is the 
longest at 60,190 earth days.

20
00:00:54,687 --> 00:00:57,724
So, the length of a day 
depends upon where you are in

21
00:00:57,724 --> 00:00:59,092
the solar system.

22
00:00:59,092 --> 00:01:01,661
For more information about the 
planets, check out the Science

23
00:01:01,661 --> 00:01:02,562
Trek website.

24
00:01:02,562 --> 00:01:04,631
You'll find it at Science Trek 
dot org.