Science unit test

What is a scientific theory?

A scientific theory is a well-tested explanation of how or why something happens in nature, supported by lots of evidence.

What three things must a scientific theory be able to do?

1. Explanation for things we observe in nature

2. Provides strong evidence for that explanations

3. Be testable and be falsifiable

How do theories help scientists understand the universe?

They help scientists explain how the universe works, connect different observations, and predict what they might discover next.

Units for Measuring Distances in Space

1. Astronomical unit (AU)

• Definition: The average distance between Earth and the Sun.

• Used for: Distances within our solar system.

Example: Earth is about 1 AU from the Sun

2. Light-year (ly)

• Definition: The distance light travels in one year on earth

• Used for: Distances between stars and galaxies.

Example: Proxima Centauri, the nearest star beyond the Sun, is about 4.24 light-years away.

Scientific notation

used to simplify really large numbers or really small numbers

What does the electromagnetic spectrum show?

It shows all types of electromagnetic radiation arranged by wavelength or frequency.

As you move toward gamma rays:

Wavelength decreases.

Frequency increases.

Energy increases.

What is radiation?

Radiation is energy that travels through space or matter as waves or particles. Electromagnetic radiation can travel through empty space.

Similarities and differences of electromagnetic waves

All electromagnetic waves:

• Transfer energy.

• Travel at the speed of light in a vacuum.

• Do not require a medium to travel.

They differ in wavelength, frequency, energy

What are the levels of hazardousness for different types of radiation?

• Radio waves, microwaves, infrared: Generally not harmful; intense exposure can heat tissue.

• Visible light: Usually safe at normal levels, but very bright sources can damage eyes.

• Ultraviolet: Can damage skin

• X-rays and gamma rays: damage cells and DNA.

• Gamma rays: extremely hazardous

Describe each type of orbit

1. Geostationary orbit

• Above the equator.

• Takes about 24 hours to orbit Earth.

• Appears to stay over the same location.

• Used for communications and weather monitoring

2. Low Earth orbit (LEO)

• Relatively close to Earth.

• Usually takes about 90–120 minutes to orbit.

• Used for Earth imaging and the International Space Station.

3. Polar orbit

• Passes over or near both poles.

• Earth rotates beneath the satellite, allowing it to observe different areas.

• Used for mapping and environmental monitoring.

Natural vs. artificial satellites

Natural satellite: A naturally occurring object that orbits another object, such as the Moon orbiting Earth.

Artificial satellite: A human-made object placed in orbit, such as a weather satellite.

Describe four ways satellites help us on earth

Weather forecasting: Track storms and hurricanes.

Communication: Support television, phone, and internet services.

Navigation: GPS helps people find locations and directions.

Earth observation: Monitor wildfires, deforestation, ice melt, and pollution.

Explain why space junk is a problem and how it can be solved

Space junk is old satellites, broken pieces of spacecraft, and other human-made debris orbiting Earth.

Why is it a problem? Debris travels very quickly and can damage working satellites or spacecraft when they collide.

Solutions: Track debris, design satellites to leave orbit safely when their missions end, and develop ways to remove dangerous debris.

Compare the wavelengths and energies of red light and blue light.

Red light: Longer wavelength and lower energy.

Blue light: Shorter wavelength and higher energy.

Explain red-shift and blue-shift regarding the electromagnetic spectrum.

Redshift: Light shifts toward longer wavelengths, indicating that an object is moving away from us.

Blueshift: Light shifts toward shorter wavelengths, indicating that an object is moving toward us.

This is the Doppler effect applied to light.

Describe the sound you would hear when a train blows its horn as it passes by you.

The horn sounds higher-pitched as the train approaches and lower-pitched as it moves away. This is the Doppler effect for sound.

What can the spectral lines from stars and galaxies tell us? Explain how this works.

Elements absorb or emit specific wavelengths of light, producing unique patterns called spectral lines. Scientists compare these patterns with laboratory measurements to determine which elements are present in stars and galaxies.

How are spectral lines used to measure the velocity of moving stars?

Scientists compare the observed spectral lines with their normal wavelengths.

• Shift toward red → moving away.

• Shift toward blue → moving toward us.

• A larger shift generally indicates a higher speed along our line of sight.

What is a scientific theory? How is the Big Bang Theory an example of this?

The Big Bang theory is the scientific theory that the universe expanded from an extremely hot, dense early state and expanded over time. In the beginning, it was filled with gamam rays but over time, it streatched into microwaves and will continue streatching

It is a scientific theory because it explains observations and is supported by multiple lines of evidence.

What is Hubble’s Law and how was it discovered?

hubble's Law states that, the farther away a galaxy is, the faster it generally moves away.

Edwin Hubble and other astronomers combined galaxy-distance measurements with observations of redshift in the late 1920s to establish this relationship.

How does Hubble's Law support the Big Bang?

Hubble’s Law shows that distant galaxies are moving away from us, proving that the entire universe is continuously expanding. If we trace that expansion backward, the universe would have been much hotter and denser in the past.

How does the Cosmic Microwave Background Radiation support the big bang?

The Cosmic Microwave Background Radiation (CMBR) supports the Big Bang Theory because it is leftover radiation from the early universe.

• The early universe was extremely hot and dense.

• As the universe expanded, it cooled down, allowing light to travel freely.

• That light has stretched into microwave radiation as the universe expanded.

• Scientists can still detect this radiation today, providing evidence that the universe began in a hot, dense state.

State the region of the electromagnetic spectrum observed in each of the evidence above. (CMBR and Hubble)

The Cosmic Microwave Background (CMB) is observed in the microwave region of the electromagnetic spectrum.

Hubble’s Law: Observed using visible light and other regions of the electromagnetic spectrum, especially redshift in the light from distant galaxies.

What is the connection between mass and gravity?

Mass is the amount of matter in an object. The more mass there is in an object, the stronger its gravitational pull.

Describe how stars are formed? Make sure you use the vocabulary listed in your notes to describe each stage and process.

• Nebula Cloud: A giant cloud of mostly hydrogen and helium drifts through space.

• Gravitational Collapse: Cold temperatures cause pockets of gas and dust to clump together. As they collect more mass, their gravity grows stronger and pulls the material inward.

• Protostar: As the material packs tighter, friction and compression heat up the core, forming a hot, baby star called a protostar.

• Nuclear Fusion Ignition: Hydrogen atoms begin to smash together and fuse into helium. This process—nuclear fusion—releases massive amounts of energy.

• Main Sequence Birth: The outward push from nuclear fusion balances the inward pull of gravity, and the star officially ignites as a main sequence star

What is Nuclear Fusion?

Nuclear fusion is a process where two light atomic nuclei combine to form a single heavier nucleus, releasing a massive amount of energy

List reasons why our sun plays an important role in our solar system and life on earth. Make sure to provide examples for the reasons.

Light: Provides energy for photosynthesis.

Heat: Keeps Earth warm enough for liquid water.

Climate and weather: Solar energy drives winds and the water cycle.

Gravity: Holds the planets in orbit around the Sun.

Life: Supports food chains because plants use sunlight to make glucose.

difference between meteors, meteoroids and meteorites

Meteoroid (In Space)

Meteor (In the Atmosphere)

Meteorite (On the Ground)

What is the frost line?

The frost line (or snow line) is the distance from a star where it gets cold enough for gases to freeze into solid ice. between mars and jupiter, after the aesteroid belt