Space Challenge Practice
| # | Answer |
|---|---|
| 1 | A star produces its own light and energy through nuclear fusion, while a planet does not produce its own light and instead reflects light from a star. |
| 2 | Mercury. |
| 3 | Jupiter. |
| 4 | Gravity. |
| 5 | The Sun. |
| 6 | We see different phases because the Moon orbits Earth, and we observe different portions of its sunlit side. |
| 7 | A light-year is a unit of distance, not time. |
| 8 | Gravity is still present in orbit, but astronauts and their spacecraft are in continuous free fall around Earth, so they experience apparent weightlessness. |
| 9 | The Milky Way Galaxy. |
| 10 | A meteor is the streak of light seen when space rock burns in the atmosphere; a meteorite is the part that reaches Earth's surface. |
| 11 | Seasons happen because Earth’s axis is tilted. As Earth orbits the Sun, each hemisphere receives different angles and lengths of sunlight during the year. |
| 12 | The Moon is tidally locked to Earth, meaning it rotates once on its axis in the same time it takes to orbit Earth. |
| 13 | Distance = speed × time = 20,000 m/s × 10 s = 200,000 m. |
| 14 | Time = distance ÷ speed = 150,000,000 km ÷ 300,000 km/s = 500 s, which is about 8.3 minutes. |
| 15 | Rotation is an object spinning on its axis; revolution is one object orbiting another. |
| 16 | A telescope collects more light than the human eye and can make distant objects appear brighter and more detailed. |
| 17 | It suggests the star is moving away from Earth, due to the Doppler effect. |
| 18 | Closer planets move faster in their orbits and have shorter paths to travel, so they complete one revolution in less time. |
| 19 | An exoplanet is a planet that orbits a star outside our solar system. |
| 20 | Weak gravity and little atmosphere mean there is little erosion from wind or weather, so impact craters and surface features can remain for a very long time. |
| 21 | Multiple stages reduce mass as fuel is used up, allowing the remaining rocket to accelerate more efficiently and reach space more effectively. |
| 22 | Without continuous thrust, gravity would pull it toward Earth. To stay hovering, it would need constant force to balance gravity, unlike an orbiting satellite that is falling around Earth. |
| 23 | Massive stars burn fuel faster, live shorter lives, and can end in supernovae, leaving behind neutron stars or black holes. Small stars live much longer and typically become white dwarfs. |
| 24 | Mars has evidence of ancient water, including dried river channels and minerals formed in water, which suggests conditions may once have supported life. |
| 25 | The universe is expanding, but galaxies do not all move away at the same speed. More distant galaxies generally recede faster according to Hubble’s law, and local gravitationally bound systems, like galaxies within clusters, may not be separating in the same way. |