Why Do We Always See the Same Side of the Moon ? : āĻāĻŽāĻŋ āĻāĻŋāĻ¯āĻŧ āĻ¸āĻĻāĻžāĻ¯āĻŧ āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻāĻā§āĻāĻž āĻĢāĻžāĻ˛ā§āĻšā§ āĻĻā§āĻā§ ?
1. Rotation of the Moon (āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻā§ā§°āĻŖ)
- The Moon rotates on its own axis. : āĻāĻ¨ā§āĻĻā§ā§°āĻ āĻ¨āĻŋāĻ āĻ āĻā§āĻˇāĻ¤ āĻā§ā§°ā§āĨ¤
- One rotation takes about 27 days. : āĻāĻāĻž āĻĒā§ā§°ā§āĻŖ āĻā§ā§°āĻŖ āĻā§°āĻŋāĻŦāĻ˛ā§ āĻĒā§ā§°āĻžāĻ¯āĻŧ ā§¨ā§ āĻĻāĻŋāĻ¨ āĻ˛āĻžāĻā§āĨ¤
2. Revolution Around Earth : āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻāĻžā§°āĻŋāĻāĻĢāĻžāĻ˛ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖ
- The Moon also revolves around the Earth. : āĻāĻ¨ā§āĻĻā§ā§°āĻ āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻāĻžā§°āĻŋāĻāĻĢāĻžāĻ˛ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖā§ āĻā§°ā§āĨ¤
- One revolution also takes about 27 days. : āĻāĻāĻž āĻĒā§ā§°ā§āĻŖ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖ āĻā§°āĻŋāĻŦāĻ˛ā§āĻ āĻĒā§ā§°āĻžāĻ¯āĻŧ ā§¨ā§ āĻĻāĻŋāĻ¨ āĻ˛āĻžāĻā§āĨ¤
3. Equal Time for Rotation and Revolution : āĻā§ā§°āĻŖ āĻā§°ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖā§° āĻ¸āĻŽāĻ¯āĻŧ āĻ¸āĻŽāĻžāĻ¨
- Because rotation time = revolution time, the Moon turns exactly once while orbiting Earth. : āĻ¯āĻŋāĻšā§āĻ¤ā§ āĻā§ā§°āĻŖā§° āĻ¸āĻŽāĻ¯āĻŧ āĻā§°ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖā§° āĻ¸āĻŽāĻ¯āĻŧ āĻ¸āĻŽāĻžāĻ¨, āĻ¸ā§āĻ¯āĻŧā§ āĻāĻ¨ā§āĻĻā§ā§°āĻ āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻāĻžā§°āĻŋāĻāĻĢāĻžāĻ˛ā§ āĻāĻŦāĻžā§° āĻā§ā§°āĻžā§° āĻ¸āĻŽāĻ¯āĻŧāĻ¤ āĻ¨āĻŋāĻā§āĻ āĻāĻŦāĻžā§° āĻā§ā§°ā§āĨ¤
- Therefore, the same side of the Moon always faces Earth. : āĻ¸ā§āĻāĻāĻžā§°āĻŖā§ āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻāĻā§āĻāĻž āĻĢāĻžāĻ˛ āĻ¸āĻĻāĻžāĻ¯āĻŧ āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻĢāĻžāĻ˛ā§ āĻĨāĻžāĻā§āĨ¤
4. Tidal Locking : āĻāĻžāĻāĻĄā§āĻ˛ āĻ˛āĻāĻŋāĻ
- This effect is called tidal locking.
- Earth's gravity caused this over millions of years.
- āĻāĻ āĻāĻāĻ¨āĻžāĻā§āĻ āĻāĻžāĻāĻĄā§āĻ˛ āĻ˛āĻāĻŋāĻ (Tidal Locking) āĻŦā§āĻ˛āĻŋ āĻā§ā§ąāĻž āĻšāĻ¯āĻŧāĨ¤
- āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻŽāĻžāĻ§ā§āĻ¯āĻžāĻāĻ°ā§āĻˇāĻŖ āĻļāĻā§āĻ¤āĻŋā§° āĻŦāĻžāĻŦā§ āĻ˛āĻžāĻ āĻ˛āĻžāĻ āĻŦāĻā§°āĻ¤ āĻāĻ āĻ ā§ąāĻ¸ā§āĻĨāĻž āĻ¸ā§āĻˇā§āĻāĻŋ āĻšā§āĻā§āĨ¤
5. Far Side of the Moon : āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻĻā§ā§° āĻĢāĻžāĻ˛
- The side we cannot see from Earth is called the far side of the Moon.
- āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻĒā§°āĻž āĻ¯āĻŋāĻā§ āĻĢāĻžāĻ˛ āĻĻā§āĻāĻž āĻ¨āĻžāĻ¯āĻžāĻ¯āĻŧ āĻ¤āĻžāĻ āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻĻā§ā§° āĻĢāĻžāĻ˛ (Far Side) āĻŦā§āĻ˛āĻŋ āĻā§ā§ąāĻž āĻšāĻ¯āĻŧāĨ¤
Key Point | āĻŽā§āĻ˛ āĻāĻĨāĻž
- We always see the same side of the Moon because its rotation and revolution take the same time.
- āĻāĻŽāĻŋ āĻ¸āĻĻāĻžāĻ¯āĻŧ āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻāĻā§āĻāĻž āĻĢāĻžāĻ˛ā§āĻ āĻĻā§āĻā§, āĻāĻžā§°āĻŖ āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻā§ā§°āĻŖ āĻā§°ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖā§° āĻ¸āĻŽāĻ¯āĻŧ āĻāĻā§āĨ¤
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MCQ
Q1. What do we always see from Earth ? | āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻĒā§°āĻž āĻāĻŽāĻŋ āĻ¸āĻĻāĻžāĻ¯āĻŧ āĻāĻŋ āĻĻā§āĻā§ ?
(a) Different sides of the Moon | āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻŦāĻŋāĻāĻŋāĻ¨ā§āĻ¨ āĻĢāĻžāĻ˛ (b) The same side of the Moon | āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻāĻā§āĻāĻž āĻĢāĻžāĻ˛ (c) Only the dark side | āĻā§ā§ąāĻ˛ āĻāĻ¨ā§āĻ§āĻžā§° āĻĢāĻžāĻ˛ (d) Only the bright side | āĻā§ā§ąāĻ˛ āĻāĻā§āĻŦāĻ˛ āĻĢāĻžāĻ˛
Ans: (b) The same side of the Moon | āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻāĻā§āĻāĻž āĻĢāĻžāĻ˛
Explanation: The Moon’s rotation and revolution take the same time, so the same side always faces Earth.
āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž: āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻā§ā§°āĻŖ āĻā§°ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖā§° āĻ¸āĻŽāĻ¯āĻŧ āĻāĻā§ āĻšā§ā§ąāĻž āĻŦāĻžāĻŦā§ āĻ¸āĻĻāĻžāĻ¯āĻŧ āĻāĻā§āĻāĻž āĻĢāĻžāĻ˛ āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻĢāĻžāĻ˛ā§ āĻĨāĻžāĻā§āĨ¤
Q2. The Moon rotates on its _____. | āĻāĻ¨ā§āĻĻā§ā§°āĻ āĻ¨āĻŋāĻā§° _____ āĻ¤ āĻā§ā§°ā§āĨ¤
(a) Surface | āĻĒā§āĻˇā§āĻ (b) Axis | āĻ
āĻā§āĻˇ (c) Orbit | āĻāĻā§āĻˇāĻĒāĻĨ (d) Light | āĻĒā§āĻšā§°
Ans: (b) Axis | āĻ
āĻā§āĻˇ
Explanation: Rotation means turning around its axis. āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž: āĻā§ā§°āĻŖ āĻŽāĻžāĻ¨ā§ āĻ¨āĻŋāĻā§° āĻ
āĻā§āĻˇāĻ¤ āĻā§ā§°āĻžāĨ¤
Q3. The Moon revolves around the _____. | āĻāĻ¨ā§āĻĻā§ā§°āĻ _____ ā§° āĻāĻžā§°āĻŋāĻāĻĢāĻžāĻ˛ā§ āĻā§ā§°ā§āĨ¤
(a) Sun | āĻ¸ā§ā§°ā§āĻ¯ (b) Mars | āĻŽāĻā§āĻāĻ˛ (c) Earth | āĻĒā§āĻĨāĻŋā§ąā§ (d) Jupiter | āĻŦā§āĻšāĻ¸ā§āĻĒāĻ¤āĻŋ
Ans: (c) Earth | āĻĒā§āĻĨāĻŋā§ąā§
Explanation: The Moon is Earth’s natural satellite and revolves around it.
āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž: āĻāĻ¨ā§āĻĻā§ā§° āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻĒā§ā§°āĻžāĻā§āĻ¤āĻŋāĻ āĻāĻĒāĻā§ā§°āĻš āĻā§°ā§ āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻāĻžā§°āĻŋāĻāĻĢāĻžāĻ˛ā§ āĻā§ā§°ā§āĨ¤
Q4. How many days does the Moon take to rotate once ? | āĻāĻ¨ā§āĻĻā§ā§°āĻ āĻāĻŦāĻžā§° āĻā§ā§°āĻŋāĻŦāĻ˛ā§ āĻāĻŋāĻŽāĻžāĻ¨ āĻĻāĻŋāĻ¨ āĻ˛āĻžāĻā§ ?
(a) 7 days | ā§ āĻĻāĻŋāĻ¨ (b) 14 days | ā§§ā§Ē āĻĻāĻŋāĻ¨ (c) 27 days | ā§¨ā§ āĻĻāĻŋāĻ¨ (d) 365 days | ā§Šā§Ŧā§Ģ āĻĻāĻŋāĻ¨
Ans: (c) 27 days | ā§¨ā§ āĻĻāĻŋāĻ¨
Explanation: The Moon takes about 27 days to complete one rotation. āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž: āĻāĻ¨ā§āĻĻā§ā§°āĻ āĻāĻŦāĻžā§° āĻ¸āĻŽā§āĻĒā§ā§°ā§āĻŖ āĻā§ā§°āĻŋāĻŦāĻ˛ā§ āĻĒā§ā§°āĻžāĻ¯āĻŧ ā§¨ā§ āĻĻāĻŋāĻ¨ āĻ˛āĻžāĻā§āĨ¤
Q5. The Moon takes about ____ days to revolve around Earth. | āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻāĻžā§°āĻŋāĻāĻĢāĻžāĻ˛ā§ āĻāĻ¨ā§āĻĻā§ā§°āĻ āĻĒā§ā§°āĻžāĻ¯āĻŧ ____ āĻĻāĻŋāĻ¨āĻ¤ āĻā§ā§°ā§āĨ¤
(a) 10 | ā§§ā§Ļ (b) 20 | ā§¨ā§Ļ (c) 27 | ā§¨ā§ (d) 50 | ā§Ģā§Ļ
Ans: (c) 27 | ā§¨ā§
Explanation: The Moon also takes about 27 days to orbit Earth. āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž: āĻāĻ¨ā§āĻĻā§ā§°āĻ āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻāĻžā§°āĻŋāĻāĻĢāĻžāĻ˛ā§ āĻā§ā§°āĻŋāĻŦāĻ˛ā§āĻ āĻĒā§ā§°āĻžāĻ¯āĻŧ ā§¨ā§ āĻĻāĻŋāĻ¨ āĻ˛āĻžāĻā§āĨ¤
Q6. What is the effect called when rotation and revolution time are equal ? | āĻā§ā§°āĻŖ āĻā§°ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖā§° āĻ¸āĻŽāĻ¯āĻŧ āĻāĻā§ āĻš’āĻ˛ā§ āĻāĻ¯āĻŧāĻžāĻ āĻāĻŋ āĻā§ā§ąāĻž āĻšāĻ¯āĻŧ ?
(a) Gravity | āĻŽāĻžāĻ§ā§āĻ¯āĻžāĻāĻ°ā§āĻˇāĻŖ (b) Eclipse | āĻā§ā§°āĻšāĻŖ (c) Tidal Locking | āĻāĻžāĻāĻĄā§āĻ˛ āĻ˛āĻāĻŋāĻ (d) Reflection | āĻĒā§ā§°āĻ¤āĻŋāĻĢāĻ˛āĻ¨
Ans: (c) Tidal Locking | āĻāĻžāĻāĻĄā§āĻ˛ āĻ˛āĻāĻŋāĻ
Explanation: When rotation and revolution periods are equal, it is called tidal locking. āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž: āĻā§ā§°āĻŖ āĻā§°ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖā§° āĻ¸āĻŽāĻ¯āĻŧ āĻāĻā§ āĻš’āĻ˛ā§ āĻ¤āĻžāĻ āĻāĻžāĻāĻĄā§āĻ˛ āĻ˛āĻāĻŋāĻ āĻŦā§āĻ˛āĻŋ āĻā§ā§ąāĻž āĻšāĻ¯āĻŧāĨ¤
Q7. Which force helped cause tidal locking ? | āĻāĻžāĻāĻĄā§āĻ˛ āĻ˛āĻāĻŋāĻ āĻ¸ā§āĻˇā§āĻāĻŋ āĻā§°āĻžāĻ¤ āĻā§āĻ¨ āĻļāĻā§āĻ¤āĻŋāĻ¯āĻŧā§ āĻ¸āĻšāĻžāĻ¯āĻŧ āĻā§°āĻŋāĻā§ ?
(a) Wind force | āĻŦāĻ¤āĻžāĻšā§° āĻļāĻā§āĻ¤āĻŋ (b) Magnetic force | āĻā§āĻŽā§āĻŦāĻā§āĻ¯āĻŧ āĻļāĻā§āĻ¤āĻŋ (c) Earth’s gravity | āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻŽāĻžāĻ§ā§āĻ¯āĻžāĻāĻ°ā§āĻˇāĻŖ (d) Heat energy | āĻ¤āĻžāĻĒ āĻļāĻā§āĻ¤āĻŋ
Ans: (c) Earth’s gravity | āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻŽāĻžāĻ§ā§āĻ¯āĻžāĻāĻ°ā§āĻˇāĻŖ
Explanation: Earth's gravity slowly synchronized the Moon’s rotation and orbit. āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž: āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻŽāĻžāĻ§ā§āĻ¯āĻžāĻāĻ°ā§āĻˇāĻŖ āĻļāĻā§āĻ¤āĻŋāĻ¯āĻŧā§ āĻ§ā§āĻ°ā§ āĻ§ā§āĻ°ā§ āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻā§ā§°āĻŖ āĻā§°ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖ āĻ¸āĻŽāĻžāĻ¨ āĻā§°āĻŋāĻā§āĨ¤
Q8. The side of the Moon we cannot see is called the _____. | āĻ¯āĻŋāĻā§ āĻĢāĻžāĻ˛ āĻāĻŽāĻŋ āĻĻā§āĻāĻž āĻ¨āĻžāĻĒāĻžāĻ āĻ¤āĻžāĻ āĻāĻŋ āĻā§ā§ąāĻž āĻšāĻ¯āĻŧ ?
(a) Bright side | āĻāĻā§āĻŦāĻ˛ āĻĢāĻžāĻ˛ (b) Near side | āĻ¨āĻŋāĻāĻ āĻĢāĻžāĻ˛ (c) Far side | āĻĻā§ā§° āĻĢāĻžāĻ˛ (d) Hot side | āĻā§°āĻŽ āĻĢāĻžāĻ˛
Ans: (c) Far side | āĻĻā§ā§° āĻĢāĻžāĻ˛
Explanation: The far side of the Moon always faces away from Earth. āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž: āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻĻā§ā§° āĻĢāĻžāĻ˛ āĻ¸āĻĻāĻžāĻ¯āĻŧ āĻĒā§āĻĨāĻŋā§ąā§ā§° āĻĒā§°āĻž āĻāĻāĻ¤ā§°āĻ¤ āĻĨāĻžāĻā§āĨ¤
Q9. Does the far side of the Moon receive sunlight? | āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻĻā§ā§° āĻĢāĻžāĻ˛ā§ āĻ¸ā§ā§°ā§āĻ¯ā§° āĻĒā§āĻšā§° āĻĒāĻžāĻ¯āĻŧāĻ¨ā§?
(a) Yes | āĻšāĻ¯āĻŧ (b) No | āĻ¨āĻšāĻ¯āĻŧ (c) Sometimes | āĻā§āĻ¤āĻŋāĻ¯āĻŧāĻžāĻŦāĻž (d) Only at night | āĻā§ā§ąāĻ˛ ā§°āĻžāĻ¤āĻŋ
Ans: (a) Yes | āĻšāĻ¯āĻŧ
Explanation: The far side also receives sunlight; it is not always dark. āĻŦā§āĻ¯āĻžāĻā§āĻ¯āĻž: āĻĻā§ā§° āĻĢāĻžāĻ˛ā§āĻ āĻ¸ā§ā§°ā§āĻ¯ā§° āĻĒā§āĻšā§° āĻĒāĻžāĻ¯āĻŧ; āĻ āĻ¸āĻĻāĻžāĻ¯āĻŧ āĻāĻ¨ā§āĻ§āĻžā§° āĻ¨āĻšāĻ¯āĻŧāĨ¤
Q10. Why do we always see the same side of the Moon ? | āĻāĻŽāĻŋ āĻāĻŋāĻ¯āĻŧ āĻ¸āĻĻāĻžāĻ¯āĻŧ āĻāĻ¨ā§āĻĻā§ā§°ā§° āĻāĻā§āĻāĻž āĻĢāĻžāĻ˛ā§āĻ āĻĻā§āĻā§ ?
(a) Because the Moon does not move | āĻāĻ¨ā§āĻĻā§ā§° āĻ¨āĻā§ā§°ā§ (b) Because rotation and revolution take the same time | āĻā§ā§°āĻŖ āĻā§°ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖā§° āĻ¸āĻŽāĻ¯āĻŧ āĻāĻā§
(c) Because of clouds | āĻŽā§āĻā§° āĻŦāĻžāĻŦā§ (d) Because of sunlight | āĻ¸ā§ā§°ā§āĻ¯ā§° āĻĒā§āĻšā§°ā§° āĻŦāĻžāĻŦā§
Ans: (b) Because rotation and revolution take the same time | āĻā§ā§°āĻŖ āĻā§°ā§ āĻĒā§°āĻŋāĻā§ā§°āĻŽāĻŖā§° āĻ¸āĻŽāĻ¯āĻŧ āĻāĻā§
Explanation: The Moon rotates once in the same time it takes to orbit Earth, so the same side always faces Earth.
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