Exploring the Solar System and Universe

• Revision booklet covering the solar system, the scale of the universe, gravity, mass, weight, light and sound.

Scale of the Universe

• The Universe contains everything that exists and the multiverse theory suggests there could be many universes.
• A Galaxy is a huge cluster of billions of stars, planets, gas, and dust held together by gravity.
• A Solar System includes multiple planets orbiting a star.
• A Star is a huge ball of burning gas, composed mostly of helium and hydrogen.
• A Planet is a large, round body in space.
• An Asteroid is a small, rocky object in space.

Our Solar System

• Planets in order from the sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
• Mnemonic to help remember the planets' order: "My Very Easy Method Just Speeds Up Naming Planets."

Data Tables related to the Planets

• A year is the time that it takes for a planet to do one orbit around the sun.
• Earth makes one orbit in 365 days (one earth year).
• Planets further from the sun take longer to orbit it.
• A day is the time taken for a planet to rotate once on its axis.
• Earth makes one rotation in 24 hours (one earth day).
• Jupiter is the solar system's biggest planet and has 66 moons.
• It possesses the most gravity due to its large mass.
• Smaller planets with less mass have less gravity.
• Neptune and Uranus are the coldest planets.
• Venus is the hottest planet because its thick atmosphere contains greenhouse gases like carbon dioxide.

Planets and Orbits

• All planets move around the sun in an elliptical orbit.
• The sun is the most massive object in Earth's solar system.
• The sun's gravity keeps the solar system together with objects orbiting around it.
• Earth maintains an ideal distance from the sun, providing a habitable climate, and is known as the 'Goldilocks' zone.
• Without the sun’s heat and light energy, life on Earth would not exist.

Gravity

• Everything with mass attracts anything else with mass.
• There is a constant force pulling everything towards the center of the Earth.
• The more mass an object has, the stronger its gravitational force.
• Gravitational attraction weakens as the distance between objects increases.
• Gravity causes objects to have weight.
• Astronauts appear weightless in space due to the absence of gravity.

Weight, Mass, and Gravity

• Weight (N) = mass (kg) x gravity (N/Kg)
• Mass = weight ÷ gravity
• Gravity = weight ÷ mass
• Mass remains constant regardless of location, while weight changes depending on gravity.

Astronaut Mass/Weight Sample Problem

• An astronaut with a mass of 72 kg on Earth retains the same mass in space (72 kg).
• In space (zero g), the astronaut's weight is 0N.
• On Earth, gravity pulls with a force of 10N on every kilogram of mass.
• An astronaut who has a mass of 72kg has a weight of 720N.

Gravity and Space Travel

• An astronaut's mass remains constant at 60 kg during a journey to the moon.
• Gravity decreases as an astronaut leaves Earth orbit, resulting in reduced weight.
• In space where there is no gravity, an astronaut weighs nothing.
• On the moon's surface, an astronaut weighs less than on Earth due to the moon's weaker gravity (1.6N/Kg).
• Weight increases if an astronaut travels near a planet in space due to the presence of some gravity.

Day and Night/Earth Rotation

• Day and night are due to the Earth's rotation.

Seasons

• The Northern and Southern Hemispheres experience seasons.
• Seasons are caused by the Earth's tilt on its axis.
• Summer occurs in the northern hemisphere/pointed towards the sun/strong sun, with long, hot days and short nights.
• Summer occurs in the northern hemisphere/pointed away from the sun/weak sun, with low, cold, short days.

The Sun

• The sun 'rises' in the East and 'sets' in the West.
• The sun is highest at midday, resulting in very short shadows.
• Shadows are very long in the morning and evening when the sun is low.
• Shadows are long all day during winter and shorter during summer.

Eclipses

• Eclipses occur when the sun, moon, and earth align.
• During a lunar eclipse, the moon passes into the Earth's shadow.
• During a solar eclipse, the moon passes directly in front of the sun, casting a shadow on the earth.

Satellites

• A satellite orbits around a planet or star.
• Moons are natural satellites.
• Earth's moon orbits it in approximately 28 days.
• Other planets in Earth's solar system have moons.
• Jupiter has 66 moons.
• Mars has 2 moons.

Artificial Satellites

• Thousands of artificial satellites orbit Earth.
• They are used for communications (satellite television and phone calls), weather forecasting, navigation (GPS), and space research.
• Polar orbits take satellites over the Earth's poles, closely mapping the planet and monitoring weather.
• Geostationary satellites move at the same speed as Earth's rotation, maintaining a constant position in the sky for communication, phone calls, and GPS.

Space Exploration

• Space probes are unmanned devices used to explore space and gather scientific data.
• Since the 1950s, approximately 200 space probes have been launched to photograph space and transmit information back to Earth.
• Voyager 1, one of the most successful probes, is the farthest man-made object from Earth.
• Launched in 2002, SpaceX develops reusable rockets for space travel.
• Elon Musk aims to establish a human presence on Mars in the coming years.

Pros/Cons of Space Exploration

• Pros: learning more about the universe, understanding the origin of life, finding potential life on other planets, and discovering habitable planets.
• Cons: high costs, potential for using resources to solve problems on Earth (poverty, world hunger, climate change), and pollution/climate change.

Light and Sound

• Light comes from luminous sources like the sun, candles, and light bulbs.
• Light is a wave of energy that always travels in a straight line (light ray).
• Light travels at 300,000,000 meters per second/Sound travels at 340 m/s.
• Light travels through a vacuum because it does not need particles.
• Sound cannot travel through a vacuum as it needs air particles.

Reflection

• The angle of incidence (i) equals the angle of reflection (r).

Periscopes

• A periscope allows one to see over walls using mirrors at 45° angles.

Refraction

• Light slows down and changes direction when it moves from a less dense medium, like air, to a thicker/more dense medium, such as glass or water.
• Refraction occurs.
• In refraction, the incident ray and the emergent ray are exactly parallel.
• Light bends towards the normal when moving from a less dense (air) to a more dense (glass) medium.
• Light bends away from the normal when moving from a more dense (glass) to a less dense (air) medium.
• Refraction makes objects in water appear shallower than they are.

Dispersion

• White light comprises seven colors.
• Shining white light through a prism causes it to split into its constituent colors.
• Light waves refract as they enter glass because they are slowed down.
• Refraction is when the spectrum is produced because different colors travel at different speeds through the glass.
• Red light slows down the least and refracts the least.
• Violet light slows down the most and refracts the most.
• Colors separate and result in a spectrum.
• Dispersion occurs.
• Easy way to remember the 7 colours (ROYGBIV) "Richard Of York Gave Battle In Vain."

Seeing Colours

• White light comprises all colors.
• When white light shines on a green surface, the surface absorbs red, orange, yellow, blue, indigo, and violet, while green reflects back.

Sound

• Sound is a wave of vibrating particles.
• Sound waves result from vibrations.
• Sound travels as vibrations are passed from one air particle to another.
• Vibrating air particles cause the ear drum to vibrate making us hear sound.
• Sound cannot travel through a vacuum because there are no particles.
• Sound travels at 340m/s.
• Sound travels fastest through solids and slowest through gases.
• Volume and pitch change depending on the amplitude/frequency.
• The loudness of sounds is measured in decibels (dB).
• Loud noises can damage hearing.

Oscilloscope Traces

• Amplitude (Volume)
• Lower amplitude = quiet sound
• Higher amplitude = louder sound
• Frequency (Pitch)
• Low frequency = low pitch
• High frequency = high pitch

How We Hear Sound

• Sound waves go into the ear canal.
• The ear drum vibrates.
• These vibrations cause 3 tiny bones and tiny hairs inside the ear to vibrate.
• The auditory nerve sends these vibrations to the brain where the sound is interpreted.

Hearing

• The loudness of sounds is measured in decibels (dB).
• Loud sounds can damage hearing.

Outer/Middle/Inner Ear Damage

• Continuous exposure to loud noises can slowly damage the tiny hairs inside the ears.
• After the tiny hairs are damaged, they no longer pass on the vibrations as well.
• Sudden exposure to loud noise can damage the person's ear drum and damage tiny bones.

Auditory Ranges

• Different animals have different auditory ranges.

Echolocation

• Some animals use sound waves to 'see' where they are going.
• High frequency sounds bounce off the objects in front of them and the echo tells the animal what is in front of them.
• This is called echolocation.

Distance / Speed / Time

• Speed = Distance / Time
• Distance = Speed x Time
• Time = Distance / Speed