Science mid yearly 2025

universe

all matter and space that exists

one light year

distance light travels in one year

distance of light year

9.46 x 10^12 km

galaxy

a group of dust, gas and stars held together by gravity

planetary system

planets, asteroids, meteoroids, comets, other celestial objects

star

hot sphere of plasma, massive object held by gravity, produces light by burning hydrogen

ordinary matter

made of protons, neurons and electrons that combine to form atoms

what does ordinary matter make up of

stars, planets, other objects found in space

dark matter

does not reflect, emit or obstruct light (cannot see it)

dark energy

pushes universe apart against pull of gravity

name the types of galaxies

elliptical, spiral, irregular

elliptical galaxy

elliptical shape, contains old stars

spiral galaxy

spiral shaped with long arms from centre, consists of flat rotating disk of stars, gas and dust

irregular galaxy

does not have a regular or distinct shape

celestial objects

any natural objects found in space (most form when gravity causes gas/dust to clump together)

moon

orbits a planet, is a natural satelite, usually solid and rocky, reflected light from the sun

solar system

the eight planets and their moons that orbit the sun, apart of planetary system

inner planets

Mercury, Venus, Earth, & Mars, orbits within the asteroid belt. Planets made up of rocks and metal with solid surfaces,

outer planets

Jupiter, Saturn, Uranus, & Neptune. planets made up of gases called gas giants

Kupier belt

a region of the solar system past Neptune with comets, asteroids, and icy objects.

goldilocks zone

habitable zone able to sustain life (earth)

the bigger the planets:

the stronger the gravity

history of the solar system

formed a cloud of gas and dust called molecular cloud, gravity of cloud fell and formed sun

when did the solar system approx. form?

4.6 billion years ago

protoplanetary disk

remaining gas and dust from collapsing of molecular cloud, surrounding the sun, primarily made up of gas (helium and hydrogen) and dust

extraterrestial objects

much smaller than sun and planets includes comets, asteroids, meteoroids, meteor

when was approx the universe formed?

13.6 billion years ago

universe formed from?

explosion or rapid expansion (big bang)

star evolution

starts with gas and dust cloud (nebula), protostar, main sequence, then continues

protostar

formed star within a nebula

main sequence star

A stable star fusing hydrogen into helium

4 major types of stars

main sequence, red giants, supergiants and white dwarfs

red giant

expanded, cooled star after hydrogen is reduced, relatively old

white dwarf

hot core left behind when red giant loses its outer layers

black dwarf

A white dwarf that has burnt out completely.

supernova

massive explosion of a big dying star, red super giant

neuron star

collapsed core left after a supernova and contains only neurons in the dense core

hertz-spring russell diagram

graph of stars, showing relationship between stars

heliocentric model

sun is centre of solar system, planets revolve around

geocentric model

earth was centre, sun and other planets revolved around it, outdated

nebula

hydrogen forms gas clouds in space, bigger clouds have stronger gravity and birthplace of stars

AU

astronomical unit, used to measure distance from earth to sun

km used in science

used to measure diameter or planets

speed of light

3 x 10^8 m/sec

stellar parallax method

A method of determining the distance to nearby stars.

frequency getting highter =

wavelength getting shorter

Hubble telescope

captures clear images of space from above Earth's atmosphere

Edwin Hubble

proved that other galaxies existed beyond the edge of the milky way

milky way

A large spiral galaxy that is home to Earth and the rest of our solar system, and about a trillion stars.

radio telescope

telescope that detects radio waves from space

telescope

magnifies distant objects

infra-red

has long wavelengths that are longer than visible light and feels like heat

infrared telescope

Telescope that detects heat (infrared raditation) from objects in space

what is a black hole

a region in space with gravity so strong that nothing, not even light, can escape

gravitational field

a force field that exists in the space around every mass or group of masses

in 1955, there were two theories on the origin of the universe:

steady state and evolutionary

steady state theory 1940-1960s

a theory which states that there was no beginning to the universe and that the universe does not change in appearance.

what is the big bang theory

started at a hot, dense point of the universe 13.6 billion years ago and has expanded ever since

redshift galaxies

light from galaxies shifts red, shows the universe is expanding

steady state proposed by:

Fred Hoyle, Herman Bondi, and Thomas Gold

Big bang theory proposed by:

edwin hubble saw galaxies moving away, showing the universe is expanding

explain big bang theory

• supported when edwin hubble found that galaxies were moving farther away form us

• started with tiny, hot, dense point then expanded really quick

• right after big bang, universe was really hot and full of energy

doppler effect

a sound changes as something noisy moves closer or away

gravity

A force that pulls objects toward each other

the closer 2 things are:

the stronger the force of gravity

nuclear fusion

hydrogen atoms fuse into helium, creating heat and light in a star

gravity's role in planetary orbits

gravity helps create celestial objects and keeping them together

planets stay in orbit:

due to balance of two forces:

• inertia and gravity

inertia

The tendency of an object to resist a change in motion

because of inertia:

objects keep moving in the same direction at the same speed unless something makes them stop or change

balance between gravity and inertia:

causes planet to move in an elliptical orbit around the sun

formation of black holes

a huge star’s outer layers explode, and its core collapses until a black hole forms

event horizon

the boundary where nothing can escape the black hole “point of no return”

climate change:

unexpected rise/lower of temperature

earths climate:

constantly changing for millions of years

glacial periods

earths history when it was colder, covered in ice

interglacial periods

warmer periods of time

Earths atmosphere

layer of gases around the planet that supports and protects life

carbon dioxide is

greenhouse gas

greenhouse gas:

natural gases that trap heat in Earth’s atmosphere and keep the planet warm

what increases greenhouse gases?

burning fossil fuels at fast rates to like factories trapping heat in earth’s atmosphere

ice core data was to record:

data helps check if today’s rise in carbon dioxide and temperature follows natural patterns

glaciers form

years and years of snow pile on top of eachother (become ice)

layers of an ice core

youngest was at the top and oldest was at bottom

fossils:

Preserved remains of once-living organisms

fossils include

include bone, teeth, shells, imprints

fossilisation

process of preserving parts of organisms

process of fossilisation

1. organism dies

2. buried by sediment

3. soft parts go decay

4. hard parts turn to rock

2. remains become covered in sediment

3. petrification (turned to rock)

4. fossil exposed due to erosion

soft bodied organisms

less likely to fossilise than those with hard shells

2 main methods to determine fossils

relative and absolute dating

techniques like carbon dating providing exact date in years

trilobites

a common Paleozoic era ocean animal, related to today’s Horseshoe Crab

different types of fossils

petrified,imprints, mould, cast, amber

mould fossils

impressions left in rock

cast fossils

3D replicas formed when minerals fill a mould

imprint fossils

preserve details like leaves or feathers as thin carbon layers

petrified fossils

form when wood or bone is turned into stone by mineral replacements