Chapter 8
The Universe
Elementary Science Class Five (English Version)
Textual Dictionary
All entries below are taken from this chapter, and the meanings are given in English.
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| countless (KOUNT-ləs) | Too many to be counted. | numerous (many) innumerable (uncountable) | few (not many) limited (small in number) | You can see countless stars in the night sky. The night sky contains too many stars to count. |
| telescope (TEL-ə-skohp) | An instrument used to see distant objects in space more clearly. | observatory instrument (space-viewing tool) scope (viewing instrument) | — | Scientists use a telescope to study stars and planets. A telescope helps scientists observe distant objects. |
| research (REE-surch) | Careful study to discover or understand something. | study (learning) investigation (careful examination) | neglect (failure to study) ignorance (lack of knowledge) | Scientists research planets, stars and galaxies. Scientists carefully study objects in space. |
| orbit (OR-bit) | The specific path followed by a planet around the Sun. | path (route) course (direction of movement) | — | The Earth moves around the Sun in its orbit. The Earth follows a fixed path around the Sun. |
| rotation (roh-TAY-shən) | The spinning movement of the Earth on its own axis. | spinning (turning) turning (moving around) | stillness (no movement) rest (lack of motion) | The rotation of the Earth causes day and night. The Earth's spinning produces day and night. |
| satellite (SAT-ə-lite) | An object that revolves around a planet. | orbiter (object in orbit) moon (natural satellite) | — | The Moon is the only satellite of the Earth. The Moon moves around the Earth. |
| reflects (ri-FLEKTS) | Sends light back instead of producing its own light. | returns (sends back) 反射 করে (bounces light back) | absorbs (takes in) produces (makes) | The Moon reflects the Sun's light. The Moon sends the Sun's light back to us. |
| expanding (ik-SPAN-ding) | Becoming larger or spreading farther. | growing (becoming larger) spreading (extending) | shrinking (becoming smaller) contracting (becoming tighter) | The Universe is still expanding. The Universe is continuing to become larger. |
1. How to Use This Sheet
- Read the chapter before studying the vocabulary.
- Cover the meaning column and test yourself on each word.
- Read the pronunciation aloud and practise saying each word clearly.
- Study the synonyms and antonyms to understand related meanings.
- Copy the example sentences and use them for writing practice.
- Review the key points after reading the chapter and check what you remember.
Textual Dictionary
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| countless (কাউন্টলেস) | অগণিত (too many to be counted) | numerous (অনেক); innumerable (অগণনীয়) | few (অল্প); limited (সীমিত) | You can see countless stars in the night sky. তুমি রাতের আকাশে অগণিত তারা দেখতে পারো। |
| telescope (টেলিস্কোপ) | দূরের মহাজাগতিক বস্তু স্পষ্টভাবে দেখার যন্ত্র (an instrument for seeing distant objects) | observatory instrument (পর্যবেক্ষণের যন্ত্র); scope (দেখার যন্ত্র) | — | Scientists use telescopes to research planets, stars and galaxies in space. বিজ্ঞানীরা মহাকাশের গ্রহ, তারা ও গ্যালাক্সি গবেষণা করতে টেলিস্কোপ ব্যবহার করেন। |
| research (রিসার্চ) | কোনো বিষয় বোঝা বা জানার জন্য সতর্ক অধ্যয়ন (careful study) | study (অধ্যয়ন); investigation (অনুসন্ধান) | neglect (অবহেলা); ignorance (অজ্ঞতা) | Scientists research planets, stars and galaxies. বিজ্ঞানীরা গ্রহ, তারা ও গ্যালাক্সি নিয়ে গবেষণা করেন। |
| orbit (অরবিট) | সূর্যের চারদিকে কোনো গ্রহের নির্দিষ্ট পথ (the specific path around the Sun) | path (পথ); course (গতিপথ) | — | The Earth moves around the Sun in its orbit. পৃথিবী তার কক্ষপথে সূর্যের চারদিকে ঘোরে। |
| rotation (রোটেশন) | নিজ অক্ষের চারদিকে পৃথিবীর ঘূর্ণন (spinning movement on its own axis) | spinning (ঘোরা); turning (ঘূর্ণন) | stillness (স্থিরতা); rest (নিশ্চলতা) | The rotation of the Earth causes day and night. পৃথিবীর ঘূর্ণনের কারণে দিন ও রাত হয়। |
| satellite (স্যাটেলাইট) | কোনো গ্রহকে প্রদক্ষিণকারী বস্তু (an object that revolves around a planet) | orbiter (কক্ষপথে ঘোরা বস্তু); moon (প্রাকৃতিক উপগ্রহ) | — | The Moon is the only satellite of the Earth. চাঁদ পৃথিবীর একমাত্র উপগ্রহ। |
| reflects (রিফ্লেক্টস) | নিজে আলো তৈরি না করে আলো ফিরিয়ে দেয় (sends light back) | returns (ফিরিয়ে দেয়); bounces (প্রতিফলিত করে) | absorbs (শোষণ করে); produces (উৎপন্ন করে) | The Moon reflects the Sun's light. চাঁদ সূর্যের আলো প্রতিফলিত করে। |
| expanding (এক্সপ্যান্ডিং) | বড় বা আরও বিস্তৃত হওয়া (becoming larger or spreading farther) | growing (বড় হওয়া); spreading (ছড়িয়ে পড়া) | shrinking (ছোট হওয়া); contracting (সংকুচিত হওয়া) | The Universe is still expanding. মহাবিশ্ব এখনও প্রসারিত হচ্ছে। |
This textual dictionary contains 8 words from the chapter.
◆ Key Points
- The Universe contains countless stars, planets and galaxies.
- A telescope helps people see distant objects in space more clearly and bigger.
- Astronomy is the study of the Universe, including stars, planets and space.
- The Universe is still expanding, and no one knows its exact size.
- The Earth moves around the Sun in a specific path called its orbit.
- The Earth takes about 365 days and 6 hours to complete one trip around the Sun.
- The Earth also spins on its own axis, and this motion is called rotation.
- The rotation of the Earth causes day and night.
- The part of the Earth facing the Sun has day, while the opposite part has night.
- The tilt of the Earth's axis and its orbit around the Sun cause the seasons.
- The Moon is the only satellite of the Earth and revolves around it.
- The Moon does not produce its own light, but it reflects the Sun's light.
- The changing bright shapes of the Moon are called the phases of the Moon.
2. Key Words - Main Table (1-15)
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| countless (কাউন্টলেস) | Too many to be counted. | numerous; innumerable | few; limited | You can see countless stars with open eyes. |
| stars (স্টারস) | Bright objects seen in the night sky. | celestial bodies; suns | — | The telescope helps us see distant stars. |
| telescope (টেলিস্কোপ) | An instrument used to see distant objects more clearly. | observatory instrument; scope | — | Scientists use a telescope to study space. |
| clearly (ক্লিয়ারলি) | In an easy-to-see or easy-to-understand way. | plainly; distinctly | dimly; unclearly | The telescope shows the stars more clearly. |
| bigger (বিগার) | Larger in size. | larger; greater | smaller; lesser | A telescope makes distant objects look bigger. |
| scientists (সায়েন্টিস্টস) | People who study the natural world carefully. | researchers; investigators | — | Scientists research planets and galaxies. |
| use (ইউজ) | To employ something for a purpose. | employ; utilize | discard; avoid | Scientists use telescopes to study the Universe. |
| research (রিসার্চ) | Careful study to discover or understand something. | study; investigation | neglect; ignorance | Scientists research planets, stars and galaxies. |
| planets (প্ল্যানেটস) | Large bodies that move in specific paths around the Sun. | worlds; celestial bodies | — | The Earth is one of the planets in the solar system. |
| galaxies (গ্যালাক্সিজ) | Huge groups of stars in space. | star systems; universes | — | The Milky Way is one of the galaxies in the Universe. |
| space (স্পেস) | The vast area beyond the Earth. | outer space; cosmos | — | Telescopes help scientists study objects in space. |
| Universe (ইউনিভার্স) | All of space and the objects in it. | cosmos; creation | — | The Universe is still expanding. |
| study (স্টাডি) | Careful learning about a subject. | examine; investigate | neglect; ignore | Astronomy is the study of the Universe. |
| technologies (টেকনোলজিজ) | Scientific methods and tools used for a purpose. | methods; techniques | — | Scientists use different technologies to study the Universe. |
| Astronomy (অ্যাস্ট্রনমি) | The study of the Universe, including stars, planets and space. | space science; astrophysics | — | Astronomy helps us learn about stars and planets. |
◆ Key Points
- The Universe contains countless stars, planets and galaxies.
- A telescope helps people see distant objects more clearly and bigger.
- Astronomy is the study of the Universe, including stars, planets and space.
- The Universe is still expanding.
- No one knows for sure about the exact size of the Universe.
- The Earth moves around the Sun in a specific path called its orbit.
- The Earth takes about 365 days and 6 hours to complete one trip around the Sun.
- The Earth spins on its own axis, and this motion is called rotation.
- The rotation of the Earth causes day and night.
- The tilt of the Earth's axis and its orbit around the Sun cause the seasons.
- The Moon is the only satellite of the Earth and revolves around it.
- The Moon does not produce its own light, but it reflects the Sun's light.
3. Key Words - Main Table (16-30)
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| measure (MEZH-er) | To find the size, amount, or length of something. | calculate; assess; gauge | estimate; ignore; overlook | We can measure the time taken by light to reach the Earth. |
| distance (DIS-təns) | The amount of space between two places or objects. | space; interval; gap | closeness; nearness; contact | The distance from the Moon to the Earth is 3,84,400 km. |
| light (LYTE) | The form of energy that makes objects visible and travels from the Sun. | brightness; illumination; beam | darkness; shadow; dimness | Light can travel 3,00,000 km a second. |
| travel (TRAV-əl) | To move from one place to another. | move; journey; go | stay; remain; stop | Light takes about 8 minutes to travel from the Sun to the Earth. |
| speed (SPEED) | The rate at which something moves. | pace; velocity; rate | slowness; delay; stillness | The time can be found by using the distance and the speed of light. |
| calculate (KAL-kyoo-late) | To find an answer by using numbers or facts. | compute; work out; determine | guess; neglect; miscalculate | Calculate how long light takes to travel from the Moon to the Earth. |
| approximately (ə-PROK-sə-mət-lee) | Almost, but not exactly. | about; nearly; roughly | exactly; precisely; accurately | Light can travel at approximately 3,00,000 km a second. |
| emitted (ee-MIT-id) | Sent out from a source. | released; sent; produced | absorbed; received; stopped | We see sunlight that was emitted from the Sun about 8 minutes ago. |
| galaxy (GAL-ək-see) | A huge group of stars in space. | star system; galaxy group; cosmos | — | The Milky Way is one of the galaxies in the Universe. |
| expanding (ik-SPAN-ding) | Becoming larger or spreading farther. | growing; spreading; enlarging | shrinking; contracting; decreasing | The Universe is still expanding. |
| orbit (OR-bit) | The specific path followed by a planet around the Sun. | path; course; route | — | The Earth moves in a specific orbit around the Sun. |
| annual (AN-yoo-əl) | Happening once each year. | yearly; per-year; recurring | daily; monthly; irregular | The Earth's movement around the Sun is called its annual motion. |
| rotation (roh-TAY-shən) | The spinning movement of the Earth on its own axis. | spinning; turning; revolution | stillness; rest; immobility | The rotation of the Earth causes day and night. |
| axis (AK-sis) | An imaginary line passing through the centre of an object. | central line; centreline; pivot | edge; outside; boundary | The Earth's axis passes through the North and South Poles. |
| diurnal (dye-UR-nəl) | Related to the daily movement of the Earth. | daily; day-to-day; everyday | nightly; occasional; irregular | The Earth's diurnal motion causes day and night. |
◆Key Points
- The time taken by light is found by dividing distance by the speed of light.
- Light travels approximately 3,00,000 km in one second.
- Light takes about 1.3 seconds to travel from the Moon to the Earth.
- Light takes about 8 minutes to travel from the Sun to the Earth.
- The Milky Way is one of the galaxies in the Universe.
- The Universe is still expanding.
- The orbit of a planet is its specific path around the Sun.
- The Earth takes about 365 days and 6 hours to complete one trip around the Sun.
- An axis is an imaginary line passing through the centre of an object.
- The Earth's rotation on its own axis causes day and night.
4. Subject Terms and Definitions
◆ Key Points
- The Universe contains stars, planets and galaxies.
- A telescope helps people see distant space objects more clearly and bigger.
- A galaxy is a huge group of stars in space.
- Astronomy is the study of the Universe, including stars, planets and space.
- The Universe is still expanding, and its exact size is not known.
- The orbit of a planet is its specific path around the Sun.
- Earth's annual motion is its movement around the Sun in its orbit.
- An axis is an imaginary line passing through the centre of an object.
- Earth's diurnal motion is its spinning movement on its own axis.
- The rotation of Earth causes day and night.
- The tilt of Earth's axis and its orbit around the Sun cause the seasons.
- The Moon is Earth's only satellite and revolves around Earth.
- The Moon does not produce its own light; it reflects the Sun's light.
- The changing bright shapes of the Moon are called the phases of the Moon.
5. Words in Context
The night sky contains countless stars, and a telescope helps scientists see them more clearly. Through careful research, scientists learn about planets and galaxies. The Earth follows its orbit around the Sun while its rotation produces day and night.
The Moon is a natural satellite of the Earth. It does not produce its own light; it reflects the Sun’s light. The Universe is still expanding, so scientists continue to study its great size and distant objects.
Use the context to remember each word: stars may be too many to count, a telescope makes distant objects easier to see, research means careful study, an orbit is a fixed path, rotation is spinning, a satellite revolves around a planet, reflects means sends light back, and expanding means becoming larger.
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| countless (KOUNT-ləs) | Too many to be counted. | numerous; innumerable | few; limited | Countless stars can be seen in the night sky. The night sky has too many stars to count. |
| telescope (TEL-ə-skohp) | An instrument used to see distant objects in space more clearly. | observatory instrument; scope | — | A telescope makes distant planets look clearer. A telescope helps us observe faraway planets. |
| research (REE-surch) | Careful study to discover or understand something. | study; investigation | neglect; ignorance | Scientists research galaxies in space. Scientists carefully study galaxies. |
| orbit (OR-bit) | The specific path followed by a planet around the Sun. | path; course | — | Earth follows its orbit around the Sun. Earth moves along a fixed path around the Sun. |
| rotation (roh-TAY-shən) | The spinning movement of the Earth on its own axis. | spinning; turning | stillness; rest | Earth’s rotation brings different parts into sunlight. Earth’s spinning causes day and night. |
| satellite (SAT-ə-lite) | An object that revolves around a planet. | orbiter; moon | — | The Moon is Earth’s natural satellite. The Moon revolves around Earth. |
| reflects (ri-FLEKTS) | Sends light back instead of producing its own light. | returns; bounces | absorbs; produces | The Moon reflects sunlight toward Earth. The Moon sends the Sun’s light back to us. |
| expanding (ik-SPAN-ding) | Becoming larger or spreading farther. | growing; spreading | shrinking; contracting | The Universe is still expanding. The Universe is continuing to become larger. |
6. Exercise 1 - Match the Meaning
Match each word in Column A with the correct meaning in Column B.
| Column A: Words | Column B: Shuffled Meanings |
|---|---|
| 1. countless | A. The spinning movement of the Earth on its own axis. |
| 2. telescope | B. Becoming larger or spreading farther. |
| 3. research | C. An object that revolves around a planet. |
| 4. orbit | D. Careful study to discover or understand something. |
| 5. rotation | E. A huge group of stars in space. |
| 6. satellite | F. Sends light back instead of producing its own light. |
| 7. reflects | G. An instrument used to see distant objects in space more clearly. |
| 8. expanding | H. Too many to be counted. |
| 9. astronomy | I. The study of the Universe, including stars, planets and space. |
| 10. galaxies | J. The specific path followed by a planet around the Sun. |
Answer Key: 1-H, 2-G, 3-D, 4-J, 5-A, 6-C, 7-F, 8-B, 9-I, 10-E
Textual Dictionary
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| countless (/ˈkaʊntləs/) | Too many to be counted. | numerous; innumerable | few; limited | You can see countless stars with open eyes. |
| telescope (/ˈtelɪskoʊp/) | An instrument used to see distant objects in space more clearly. | observatory instrument; scope | — | Scientists use telescopes to research planets, stars and galaxies in space. |
| research (/rɪˈsɜːrtʃ/) | Careful study to discover or understand something. | study; investigation | neglect; ignorance | Scientists research planets, stars and galaxies. |
| orbit (/ˈɔːrbɪt/) | The specific path followed by a planet around the Sun. | path; course | — | The Earth moves around the Sun in its orbit. |
| rotation (/roʊˈteɪʃən/) | The spinning movement of the Earth on its own axis. | spinning; turning | stillness; rest | The rotation of the Earth causes day and night. |
| satellite (/ˈsætəlaɪt/) | An object that revolves around a planet. | orbiter; moon | — | The Moon is the only satellite of the Earth. |
| reflects (/rɪˈflekts/) | Sends light back instead of producing its own light. | returns; bounces | absorbs; produces | The Moon reflects the Sun's light. |
| expanding (/ɪkˈspændɪŋ/) | Becoming larger or spreading farther. | growing; spreading | shrinking; contracting | The Universe is still expanding. |
| astronomy (/əˈstrɒnəmi/) | The study of the Universe, including stars, planets and space. | space science; astrophysics | — | Astronomy is the study of the Universe. |
| galaxies (/ˈɡæləksiz/) | Huge groups of stars in space. | star systems; galaxy groups | — | The Milky Way is one of the galaxies in the Universe. |
Worked Example Series
Ex. Find the time taken by light to travel from the Moon to the Earth.
Sol:
Time = distance ÷ speed
Time = 3,84,400 ÷ 3,00,000 seconds
Time = 1.2813... seconds
Time ≈ 1.3 seconds Ans. About 1.3 seconds.
Time = distance ÷ speed
Time = 3,84,400 ÷ 3,00,000 seconds
Time = 1.2813... seconds
Time ≈ 1.3 seconds Ans. About 1.3 seconds.
Ex. Find the time taken by light to travel from the Sun to the Earth in seconds.
Sol:
Time = distance ÷ speed
Time = 15,00,00,000 ÷ 3,00,000 seconds
Time = 500 seconds Ans. 500 seconds.
Time = distance ÷ speed
Time = 15,00,00,000 ÷ 3,00,000 seconds
Time = 500 seconds Ans. 500 seconds.
Ex. Convert 500 seconds into minutes and seconds.
Sol:
500 seconds = 8 × 60 seconds + 20 seconds
500 seconds = 480 seconds + 20 seconds
500 seconds = 8 minutes 20 seconds Ans. 8 minutes 20 seconds.
500 seconds = 8 × 60 seconds + 20 seconds
500 seconds = 480 seconds + 20 seconds
500 seconds = 8 minutes 20 seconds Ans. 8 minutes 20 seconds.
Ex. How many hours are there in 365 days and 6 hours?
Sol:
365 days = 365 × 24 hours
365 days = 8760 hours
8760 hours + 6 hours = 8766 hours Ans. 8766 hours.
365 days = 365 × 24 hours
365 days = 8760 hours
8760 hours + 6 hours = 8766 hours Ans. 8766 hours.
Ex. Express one complete rotation of the Earth as seconds using 23 hours, 56 minutes and 4.0905 seconds.
Sol:
23 hours = 23 × 3600 seconds
23 hours = 82,800 seconds
56 minutes = 56 × 60 seconds
56 minutes = 3360 seconds
Total = 82,800 + 3360 + 4.0905 seconds
Total = 86,164.0905 seconds Ans. 86,164.0905 seconds.
23 hours = 23 × 3600 seconds
23 hours = 82,800 seconds
56 minutes = 56 × 60 seconds
56 minutes = 3360 seconds
Total = 82,800 + 3360 + 4.0905 seconds
Total = 86,164.0905 seconds Ans. 86,164.0905 seconds.
7. Exercise 2 - Fill in the Blanks
Word Bank: orbit · bigger · reflects · rotation · satellite · expanding · Astronomy · the Sun · day · Moon
1. The Earth moves in a specific path called its ______.
2. A telescope helps us see distant stars more clearly and ______.
3. The Moon ______ the Sun's light.
4. The Earth's ______ causes day and night.
5. The Moon is the only ______ of the Earth.
6. The Universe is still ______.
7. ______ is the study of the Universe, including stars, planets and space.
8. The Earth completes one trip around ______ in about 365 days and 6 hours.
9. The part of the Earth facing the Sun experiences ______.
10. The changing bright shapes of the ______ are called its phases.
Answer Key: 1. orbit; 2. bigger; 3. reflects; 4. rotation; 5. satellite; 6. expanding; 7. Astronomy; 8. the Sun; 9. day; 10. Moon
Worked Example Series
Ex. Find the distance light travels in 8 minutes.
Sol:
Distance= speed × time
Time= 8 × 60 seconds
Time= 480 seconds
Distance= 3,00,000 × 480 km
Distance= 14,40,00,000 km Ans.
Ex. Convert 28 days into hours.
Sol:
1 day= 24 hours
28 days= 28 × 24 hours
28 days= 672 hours Ans.
Ex. Express 365 days and 6 hours in minutes.
Sol:
365 days= 365 × 24 hours
365 days= 8760 hours
Total hours= 8760 + 6
Total hours= 8766 hours
Total minutes= 8766 × 60
Total minutes= 5,25,960 minutes Ans.
Ex. Divide one complete rotation of the Earth into four equal parts. Find the angle of each part.
Sol:
Complete rotation= 360°
Number of parts= 4
Angle of each part= 360° ÷ 4
Angle of each part= 90° Ans.
8. Exercise 3 - Synonyms and Antonyms
Choose the correct synonym or antonym as directed.
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| countless (KOUNT-ləs) | Too many to be counted. | numerous; innumerable | few; limited | The night sky shows countless stars. |
| telescope (TEL-ə-skohp) | An instrument for seeing distant objects more clearly. | scope; observatory instrument | — | A telescope allows scientists to observe far into space. |
| research (REE-surch) | Careful study to discover or understand something. | study; investigation | neglect; ignorance | Scientists research the Universe with different technologies. |
| clearly (KLEER-lee) | In an easy-to-see or easy-to-understand way. | plainly; distinctly | dimly; unclearly | The distant stars appear more clearly through the telescope. |
| bigger (BIG-er) | Larger in size. | larger; greater | smaller; lesser | Through the telescope, a distant object looks bigger. |
| planets (PLAN-its) | Large bodies that move in specific paths around the Sun. | worlds; celestial bodies | — | The Earth is one of the planets in the solar system. |
| galaxies (GAL-əks-eez) | Huge groups of stars in space. | star systems; galaxy groups | — | The Milky Way is one of the galaxies in the Universe. |
| satellite (SAT-ə-lite) | An object that revolves around a planet. | orbiter; moon | — | The Moon is the only satellite of the Earth. |
| reflects (ri-FLEKTS) | Sends light back instead of producing its own light. | returns; bounces | absorbs; produces | The Moon reflects the Sun's light. |
| expanding (ik-SPAN-ding) | Becoming larger or spreading farther. | growing; spreading | shrinking; contracting | The Universe is still expanding. |
Answer Key: 1. numerous; 2. scope; 3. study; 4. plainly; 5. larger; 6. worlds; 7. star systems; 8. orbiter; 9. returns; 10. growing.
Worked Example Series
Ex. Find the distance light travels in 2 seconds.
Sol: Distance = speed × time
Distance = 3,00,000 × 2 km
Distance = 6,00,000 km
Ans. 6,00,000 km.
Distance = 3,00,000 × 2 km
Distance = 6,00,000 km
Ans. 6,00,000 km.
Ex. Find the total number of seconds in 365 days and 6 hours.
Sol: 365 days = 365 × 24 hours
365 days = 8760 hours
Total hours = 8760 + 6
Total hours = 8766 hours
Total seconds = 8766 × 60
Total seconds = 5,25,960 seconds
Ans. 5,25,960 seconds.
365 days = 8760 hours
Total hours = 8760 + 6
Total hours = 8766 hours
Total seconds = 8766 × 60
Total seconds = 5,25,960 seconds
Ans. 5,25,960 seconds.
Ex. Divide one complete rotation of the Earth into 8 equal parts. Find the angle of each part.
Sol: Complete rotation = 360°
Number of parts = 8
Angle of each part = 360° ÷ 8
Angle of each part = 45°
Ans. 45°.
Number of parts = 8
Angle of each part = 360° ÷ 8
Angle of each part = 45°
Ans. 45°.
Ex. Find the distance light travels in 4 seconds.
Sol: Distance = speed × time
Distance = 3,00,000 × 4 km
Distance = 12,00,000 km
Ans. 12,00,000 km.
Distance = 3,00,000 × 4 km
Distance = 12,00,000 km
Ans. 12,00,000 km.
Ex. The Moon rotates once every 28 days. How many complete rotations occur in 56 days?
Sol: Number of rotations = total days ÷ days for one rotation
Number of rotations = 56 ÷ 28
Number of rotations = 2
Ans. 2 complete rotations.
Number of rotations = 56 ÷ 28
Number of rotations = 2
Ans. 2 complete rotations.
Ex. A galaxy has ten thousand crores of stars on average. How many stars are there in 3 such galaxies?
Sol: Stars in 3 galaxies = 3 × ten thousand crores
Stars = 30 thousand crores
Ans. 30 thousand crores of stars.
Stars = 30 thousand crores
Ans. 30 thousand crores of stars.
9. Exercise 4 - Make Sentences
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| countless (KOUNT-ləs) | Too many to be counted. | numerous; innumerable | few; limited | Countless stars shine in the night sky. |
| telescope (TEL-ə-skohp) | An instrument used to see distant objects in space more clearly. | scope; observatory instrument | — | A telescope makes distant stars easier to observe. |
| research (REE-surch) | Careful study to discover or understand something. | study; investigation; examination | neglect; ignorance | Scientists research the planets and galaxies. |
| orbit (OR-bit) | The specific path followed by a planet around the Sun. | path; course; route | — | The Earth follows its orbit around the Sun. |
| rotation (roh-TAY-shən) | The spinning movement of the Earth on its own axis. | spinning; turning; revolution | stillness; rest; immobility | The rotation of the Earth brings day and night. |
| satellite (SAT-ə-lite) | An object that revolves around a planet. | orbiter; moon; space object | — | The Moon is a satellite of the Earth. |
| reflects (ri-FLEKTS) | Sends light back instead of producing its own light. | returns; bounces; sends back | absorbs; produces; emits | The Moon reflects light from the Sun. |
| expanding (ik-SPAN-ding) | Becoming larger or spreading farther. | growing; spreading; enlarging | shrinking; contracting; narrowing | The Universe is still expanding. |
This textual dictionary contains 8 words.
Answer Key: Model Sentences
- Countless stars shine in the night sky.
- A telescope makes distant stars easier to observe.
- Scientists research the planets and galaxies.
- The Earth follows its orbit around the Sun.
- The rotation of the Earth brings day and night.
- The Moon is a satellite of the Earth.
- The Moon reflects light from the Sun.
- The Universe is still expanding.
Worked Example Series
Ex. Find the time taken by sunlight to travel from the Sun to the Earth.
Sol: Distance = 15,00,00,000 km
Time = Distance ÷ speed of light
Time = 15,00,00,000 ÷ 3,00,000 seconds
Time = 500 seconds
500 seconds = 8 minutes 20 seconds
Ans. About 8 minutes.
Time = Distance ÷ speed of light
Time = 15,00,00,000 ÷ 3,00,000 seconds
Time = 500 seconds
500 seconds = 8 minutes 20 seconds
Ans. About 8 minutes.
Ex. How many complete rotations does the Moon make in 84 days if it rotates once every 28 days?
Sol: Number of rotations = total days ÷ days for one rotation
Number of rotations = 84 ÷ 28
Number of rotations = 3
Ans. 3 complete rotations.
Number of rotations = 84 ÷ 28
Number of rotations = 3
Ans. 3 complete rotations.
Ex. A galaxy has ten thousand crores of stars on average. How many stars are there in 4 such galaxies?
Sol: Stars in 4 galaxies = 4 × ten thousand crores
Stars = 40 thousand crores
Ans. 40 thousand crores of stars.
Stars = 40 thousand crores
Ans. 40 thousand crores of stars.
Ex. Divide one complete rotation of the Earth into 6 equal parts. Find the angle of each part.
Sol: Complete rotation = 360°
Number of parts = 6
Angle of each part = 360° ÷ 6
Angle of each part = 60°
Ans. 60°.
Number of parts = 6
Angle of each part = 360° ÷ 6
Angle of each part = 60°
Ans. 60°.
Ex. How many hours are there in 30 days?
Sol: Hours in 1 day = 24
Hours in 30 days = 30 × 24
Hours in 30 days = 720
Ans. 720 hours.
Hours in 30 days = 30 × 24
Hours in 30 days = 720
Ans. 720 hours.
10. Vocabulary MCQ (1-10)
Meanings and Related Words
1. What does countless mean?
A. Very few
B. Too many to be counted
C. Easy to measure
D. Not moving
Sol: [B] “Countless” means too many to be counted.
2. Which word is closest in meaning to countless?
A. Numerous
B. Limited
C. Few
D. Still
Sol: [A] “Numerous” means many, like “countless.”
Space Instruments and Study
3. What is a telescope used for?
A. Measuring temperature
B. Seeing distant objects more clearly
C. Making planets move
D. Producing sunlight
Sol: [B] A telescope helps people see distant space objects more clearly and bigger.
4. Which sentence uses research correctly?
A. Scientists research planets and galaxies.
B. Scientists research the Sun to make it shine.
C. Scientists research a telescope into a star.
D. Scientists research night into day.
Sol: [A] Research means careful study to discover or understand something.
5. In the chapter, research is closest in meaning to:
A. Neglect
B. Investigation
C. Rest
D. Rotation
Sol: [B] “Investigation” means careful examination or study.
Earth and Moon Motions
6. What is an orbit?
A. A fixed path around the Sun
B. A bright part of the Moon
C. A line through a pole only
D. A kind of star
Sol: [A] An orbit is the specific path followed by a planet around the Sun.
7. Which sentence correctly uses rotation?
A. The rotation of Earth causes day and night.
B. The rotation of Earth makes the Moon a star.
C. The rotation of Earth stops its orbit.
D. The rotation of Earth produces its own light.
Sol: [A] Rotation is the spinning movement of Earth on its own axis.
8. Which object is a satellite of Earth?
A. The Sun
B. The Moon
C. The Milky Way
D. The telescope
Sol: [B] The Moon is the only satellite of Earth and revolves around it.
Light and the Universe
9. Choose the correct meaning of reflects in the sentence “The Moon reflects the Sun’s light.”
A. Takes in light
B. Sends light back
C. Produces its own light
D. Hides the Sun
Sol: [B] The Moon does not produce its own light; it sends the Sun’s light back.
10. Which sentence uses expanding correctly?
A. The Universe is still expanding.
B. The Universe is becoming smaller by expanding.
C. The telescope is expanding the Sun’s light.
D. The Moon is expanding its own light.
Sol: [A] Expanding means becoming larger or spreading farther.
11. Quick Revision List
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| countless (KOUNT-ləs) | Too many to be counted. | numerous; innumerable | few; limited | You can see countless stars with open eyes. You can see too many stars to count with open eyes. |
| telescope (TEL-ə-skohp) | An instrument used to see distant objects more clearly and bigger. | observatory instrument; scope | — | Scientists use telescopes to research planets, stars and galaxies in space. Scientists use telescopes to study objects in space. |
| orbit (OR-bit) | The specific path followed by a planet around the Sun. | path; course | — | The Earth moves around the Sun in its orbit. The Earth follows a specific path around the Sun. |
| rotation (roh-TAY-shən) | The spinning movement of the Earth on its own axis. | spinning; turning | stillness; rest | The rotation of the Earth causes day and night. The Earth's spinning causes day and night. |
| satellite (SAT-ə-lite) | An object that revolves around a planet. | orbiter; moon | — | The Moon is the only satellite of the Earth. The Moon revolves around the Earth. |
| reflects (ri-FLEKTS) | Sends light back instead of producing its own light. | returns; bounces | absorbs; produces | The Moon reflects the Sun's light. The Moon sends the Sun's light back to us. |
| expanding (ik-SPAN-ding) | Becoming larger or spreading farther. | growing; spreading | shrinking; contracting | The Universe is still expanding. The Universe is continuing to become larger. |
| astronomy (ə-STRON-ə-mee) | The study of the Universe, including stars, planets and space. | space science; astrophysics | — | Astronomy is the study of the Universe. Astronomy helps us learn about stars and planets. |
This revision list contains 8 words from the chapter.
◆Key Points
- The Universe contains countless stars, planets and galaxies.
- A telescope helps people see distant objects in space more clearly and bigger.
- Astronomy is the study of the Universe, including stars, planets and space.
- The Universe is still expanding, and no one knows its exact size.
- The Earth follows a specific path around the Sun called its orbit.
- The Earth takes about 365 days and 6 hours to complete one trip around the Sun.
- The spinning movement of the Earth on its own axis is called rotation.
- The rotation of the Earth causes day and night.
- The part of the Earth facing the Sun has day, while the opposite part has night.
- The tilt of the Earth's axis and its orbit around the Sun cause the seasons.
- The Moon is the only satellite of the Earth and revolves around it.
- The Moon does not produce its own light but reflects the Sun's light.
- The changing bright shapes of the Moon are called the phases of the Moon.
12. Practice Bank
Further Vocabulary
| Word (Pronunciation) | Meaning | Synonyms | Antonyms | Example Sentence |
|---|---|---|---|---|
| distance (DIS-tuhns) | The amount of space between two places or objects. | space (area); interval (gap) | nearness (closeness); proximity (short distance) | The distance from the Moon to the Earth is 3,84,400 km. The space between the Moon and the Earth is 3,84,400 km. |
| measure (MEZH-er) | To find the size, amount, or distance of something. | calculate (work out); assess (judge) | guess (estimate); ignore (overlook) | We can measure time as distance divided by the speed of light. We can calculate time from distance and speed. |
| speed (SPEED) | The rate at which something moves. | pace (rate); quickness (fast movement) | slowness (low rate); delay (lateness) | Light can travel 3,00,000 km a second. Light moves at a rate of 3,00,000 km each second. |
| approximately (uh-PROK-suh-mit-lee) | Nearly, but not exactly. | about (nearly); roughly (almost) | exactly (precisely); accurately (correctly) | Light travels at approximately 3,00,000 km a second. Light travels at about 3,00,000 km each second. |
| emitted (ih-MIT-id) | Sent out, especially as light or heat. | released (sent out); given off (sent out) | received (taken in); absorbed (taken in) | We see sunlight that was emitted from the Sun about 8 minutes ago. We see light sent out by the Sun about 8 minutes earlier. |
| galaxy (GAL-uhk-see) | A huge group of stars in space. | star system (group of stars); galaxy system (space group) | — | The Milky Way is one of the galaxies in the Universe. The Milky Way is one huge group of stars in the Universe. |
| invented (in-VENT-id) | Created something new for the first time. | created (made); developed (improved) | copied (made the same); destroyed (ruined) | Galileo invented an improved telescope. Galileo created a better telescope. |
| annual (AN-yoo-uhl) | Happening once every year. | yearly (every year); per-year (each year) | daily (every day); monthly (every month) | The Earth's motion around the Sun is called its annual motion. The Earth's yearly motion around the Sun has a special name. |
| diurnal (dye-UR-nuhl) | Related to the daily rotation of the Earth. | daily (each day); day-related (connected with daytime) | nightly (each night); annual (yearly) | Day and night are caused by the Earth's diurnal motion. The Earth's daily motion causes day and night. |
| imaginary (ih-MAJ-uh-nair-ee) | Existing as an idea rather than as a physical object. | imagined (thought of); unreal (not physical) | real (actual); physical (existing) | An axis is an imaginary line passing through the centre of an object. An axis is an imagined line through the centre of an object. |
| hemisphere (HEM-uh-sfeer) | One half of the Earth. | half-sphere (half of a sphere); half (one of two parts) | whole (complete object); sphere (round body) | The northern hemisphere has summer when it tilts toward the Sun. The northern half of the Earth has summer when it tilts toward the Sun. |
| phases (FAY-ziz) | The changing shapes of the bright part of the Moon. | stages (steps); forms (shapes) | constancy (unchanging state); sameness (lack of change) | The changing shapes of the bright part of the Moon are called its phases. The Moon's bright part changes through different stages. |
Hints: space between objects; find an amount; rate of movement; nearly exact; sent out as light; a group of stars; created for the first time; yearly; daily; not physically real; half of the Earth; changing Moon shapes.