SNC1W FULL Notes

Biology:

Animal relationships

Predator: Animal that eats other animal(s)

Prey: Animal that gets eaten by another animal

Herbivore: Animal that eats plants (e.g. Squirrel)

Carnivore: Animal that eats other animals (e.g. lion)

Omnivore: Animal that eats both plants and animals (e.g. Bear) 

Decomposer: Bacteria and Fungi that break down dead matter and waste to extract nutrients

Detritivore: An organism that consumes dead material and animal waste

Symbiosis

Mutualism: Both organisms benefit

Commensalism: One organism benefits while the other is neither helped nor harmed.

Parasitism: One organism benefits and the other is harmed.

Dominant species: Most biomass (Biomass = Total mass of living organisms in an area)

Keystone species: Greatly affects the ecosystem

Ecosystem engineers: Cause dramatic change to the landscape

Interspecific: Different species

Intraspecific: Same species 

Cycles: (Remember to make all of these cycles)

Carbon Cycle:

Carbon not returned to the cycle is stored in carbon sinks. These can be the wood of trees, fossil fuels, sedimentary rock and carbonic acid in oceans.

Nitrogen Cycle:

Water Cycle:

Energy in Ecosystems:

Radiant energy from the sun travels through empty space and is emitted from the sun

Thermal energy is transferred during heating and cooling, warms the atmosphere, evaporates water and produces wind.

Light energy is visible radiant energy (Invisible radiant energy is UV light)

Photosynthesis:

The process in which the sun’s energy is converted to chemical energy

Producers are organisms that use photosynthesis to make their food (Also called Autotrophs)

Consumers are organisms that eat producers to get nutrients (Also called Heterotrophs) 

Cellular respiration

During cellular respiration, cells use oxygen to get energy and they release carbon dioxide.

Food Chains: 

Food Webs:

Feeding relationships within a community (Series of interconnecting food chains)

Trophic Levels:

Way of classifying organisms based on how they gain their energy and identifies where organisms are on the food chain/web.

1st trophic level: Producers

2nd trophic level: Primary Consumers (Herbivores)

3rd trophic level: Secondary Consumers (Small carnivores and omnivores)

4th trophic level: Tertiary consumers (Large Carnivores at the top of the food chain/web)

Any level: Scavengers (Feeds on the remains of deceased organisms)

The Biosphere

Zone around earth where life can exist

Three components within that interact with each other: The Hydrophere, Lithosphere and the Atmosphere

Atmosphere:

Layer of gasses surrounding Earth

78% nitrogen, 21% oxygen, remaining <1% is argon, water vapour and a bunch of other stuff

Acts like a blanket by moderating the surface temperature (Blocks UV light and Solar Radiation)

Three layers within the atmosphere are the Troposphere, Stratosphere and Mesosphere.

Lithosphere:

Earth’s solid outer layer

Hydrosphere: 

All the water on Earth in all states

Ecosystems

All living organisms and their physical and chemical environment

Biotic and Abiotic factors:

Biotic factors are the living things in an ecosystem as well as their remains and features(A tree and a dead tree are both biotic and a bird’s nest is also biotic)

Abiotic factors are the non-living components in an ecosystem (Like wind and temperature)

Categorizations of ecology

An individual is an individual organism

A population is all of the same species in an ecosystem

A community is all the different populations living in an ecosystem

An ecosystem is a community of living organisms and non-living components that interact with each other.

A biome is a large area defined based on its climate and plant life.

An ecological niche is how a species interacts with the biotic and abiotic factors of an ecosystem to survive. (Sort of like a job)

Example: A lion’s niche is to feed on herbivores like zebra. This means that there are fewer zebra to eat the grass, allowing it to grow more

Biodiversity

The variety of life in the world or in a particular habitat or ecosystem.

Biodiversity is important for the survival of all living things since it provides essential things such as food, water, pollination, pest control and more.

Biodiversity is not evenly distributed across the globe but it tends to be higher in the tropics and lower in the polar regions.

Some areas, known as biodiversity hotspots, have extremely high levels of biodiversity. This means that they contain many species that are found nowhere else on Earth.

Biodiversity is dynamic and constantly changes over time, as a result of natural and human-induced factors.

Scientists have estimated that there are around 8.7 million different species of plants, animals, and microorganisms on Earth.

Human activities have accelerated the rate of biodiversity loss to unprecedented levels, posing a serious threat to the biosphere.

Many efforts have been made and are currently being made to conserve and enhance biodiversity at various levels, such as international conventions, national policies, local initiatives, community-based actions and individual choices.

Population Growth:

Caused by ideal biotic factors and abiotic factors for reproduction

When they aren’t ideal it can lead to population decline and even extinction

Limiting factors

Something that limits population growth

As a population increases, every individual has access to fewer resources, leading to competition, which limits population growth

Some limiting factors include:

• Food

• Water

• Predation

• Symbiosis

• Disease

• Light availability

• Water Quality

• Temperature

Carrying capacity

The size of a population that an ecosystem can indefinitely support

As population grows, there are fewer resources available in the ecosystem

When the birth and death rate of a species is about equal, that species has reached the carrying capacity

Tolerance Range

The abiotic conditions that make it possible for a species to survive

In the optimal range, the species thrives

In the psychological stress zone, the species are infrequent

In the zone of intolerance, the species is absent

Algal Blooms

Algal blooms occur when there is a lot of food for the algae to eat. They reproduce rapidly, creating a blanket overtop a body of water. This blocks out oxygen, causing organisms below to die.

Pests

When farmers plant a single type of crop in bulk, it is called a monoculture

Organisms that we call “pests” consume the monoculture (the term pest is used to refer to human wishes, in nature they are simply producers and consumers)

Humans use pesticides to control pests.

Pesticides

Poisons designed to kill pests

Herbicides are designed to kill plants

Insecticides kill insects

Molluscicides kill snails

Fungicides kill fungi

Piscicides kill fish 

Biomagnification/Bioamplification

When there is a pesticide in an area, such as a lake, it goes into producers. As the trophic level goes up, the concentration of the pesticides inside the animal also goes up, as the higher up in the food chain you go, the more organisms you eat that are contaminated by pesticides, and the higher concentration of the pesticides. (So L humans)

Chemistry:

The Periodic Table

Created by Dimitri Mendeleev in 1869

Period = Horizontal row, numbers 1 to 7, up to down. Atomic radius decreases across a period.

Group = Vertical Column, numbers 1 to 18, left to right. Atomic radius increases down a group.

Electron Affinity = How much a nucleus attracts electrons

Density = D=M/V  M=DV   V=M/

Metals

• On the left of the periodic table

• Solid(Except Mercury)

• Shiny

• Good conductors of heat and electricity 

• Malleable

• Ductile

• Tend to lose electrons to make cations (+)

Nonmetals

• On the right of the periodic table

• Any state

• Not as shiny

• Poor conductors of heat and electricity

• Not Malleable

• Not Ductile

• Tend to gain electrons to form anions (-)

Metalloids

• Between the other 2

• Share properties

Groups

In the first few groups, the bottom elements are more reactive as they hold their electrons looser

In the last groups, the top elements are the most reactive as they have the strongest pull, therefore gain easier.

Alkali Metals

First group

• Biggest atomic radius

• Low melting points

• Soft at room temperature

• Very reactive with air and water

• 1 valence electron

• Makes positive ions easily = cation (+)

Alkaline Earth Metals

Second Group

• Bigger atomic radius

• Slightly less reactive than Alkali

• Will burn in air if heated

• Produces bright and colourful flames, fireworks

• 2 valence electrons

• Makes positive ions easily = cation (+)

Halogens

Seventeenth group

• Smaller atomic radius

• Non-metals

• Very reactive and corrosive

• Melting point increases from Fluorine to Iodine

• 1 valence electron from full

• Makes negative ions easily = anion (-)

Noble Gases

Eighteenth group

• Smallest atomic radius

• Non-metals

• Very stable

• Odourless and Colourless

• All gases at room temperature

• Full valence shell

Atoms

Atom Structure: 

Proton          Neutron               Electron

•              O                          -

 1AMU           1AMU               1/1800AMU

Nucleus       Nucleus     Electron/Energy Shells

Atomic Number = # of protons

Atomic Mass = Total mass in AMU

Mass Number = # of protons + # of neutrons

Valence shell = Outer electron shell

Bohr Rutherford Diagram:

Isotope = Mass Number = Changing # of neurons

Ion = Changing # of electrons -> Less makes cations (+), More makes anions (-)

O- = 1 extra electron

Ca+ = 1 less electron

O2- = 2 extra electrons 

Ca2+ = 2 less electrons

The nth electron shell holds 2(n2) electrons

2, 8, 18, 32, 50, 72, 98, 128

For our purposes, it’s:

2, 8, 8, 18

Substances, Mixtures and Properties

Pure Substances

Pure Substance = One type of molecule

Element = concept

Atom = Physical representation of an element

Compound = Multiple elements joining

Molecule = Compound or multiple of the same atom together

Mixtures

Heterogeneous = 2 or more phases/regions

Homogeneous = Uniform

Soluble = Dissolves in liquid

Insoluble = Doesn’t dissolve in liquid

Solute = Substance of smaller quantity

Solvent = Substance of greater quantity

Particle Theory Of Matter

• Particles attract each other

• Gas least, solid most and liquid is medium

• Particles are always moving

• Gas most, solid least and liquid is medium

Physical vs Chemical Properties

Physical

Physical properties = No formula change

• Malleability

• Lustre

• Solubility

• Hardness

• Texture

• State

• Denstiy

• Conductivity

• Ductibility

• Colour

• Odour

• Clarity

• Viscocity

• Density

Chemical

Chemical properties = Formula change

• Stability

• Toxicity

• Flamability

• Combustibility

• Tarnishing

• Corrosion

Compounds

Counting atoms

Na - 1 (1 Sodium)

H2 - 2 (The 2 is called subscript) (2 Hydrogens)

Mg3(PO4)2 - 13 (3 Magnesiums, 2 Phosphorus, 8 Oxygen)

2H2O - 6 (4 Hydrogen, 2 Oxygen) (The 2 is called a coefficient)

Naming Compounds

Ionic

Al3+ O2- -> Al2O3 = Aluminium Oxide

Add “ide” to nonmetal which comes second

Covalent

Add a prefix on the second element and on the first element if it’s not 1

H2O = Dihydrogen Monoxide

Lower group number comes first 

*Except for Oxygen and halogen, halogen goes first.

Mono - 1

Di - 2

Tri - 3

Tetra - 4

Penta - 5

Hexa - 6

Hepta - 7

Octa - 8

Nona - 9

How Compounds Form

Physics:

The electrical nature of matter

Static electricity remains in the same place

More + than - means +

More - than + means - 

Metals conduct

Non-metals Insulate

Like charges repel each other, opposite charges attract, all charges attract neutral.

All matter is made of atoms which have protons (+), neutrons (0), and electrons (-). Only electrons move.

Different materials have different forces of attraction between electrons and the nucleus giving them a higher or lower tendency to lose electrons.

Ground = Object with a large amount of electrons to lose or gain

Sources of Electrical Energy

Hydroelectric - Water

Thermoelectric - Fossil Fuels

Nuclear - Nuclear

Most sources use water’s kinetic energy to drive turbines connected via a shaft to generators which convert kinetic energy into electrical energy.

Electrical Unit Conversions

1 Watt = 1 Joule per second

1 watt hour = 1 watt for 1 hour

1 Coulomb = 6.25x1018 Electrons = Q

I = Current (Amps = A)

t = Time (Seconds!!!)

W = Wattage

V = electrical potential/voltage (Can also be called energy/E)

R = Resistance (Ohms = Ω)

V=IR  I=V/R  R=V/I

W=IV

I=Q/t

Static electricity

Charging by friction = Rub things higher on the series on things lower on the series to charge them positively or negatively. 

Current Electricity

Electric Current = The flow of electricity through a conductor in a closed path

Source -> Provides electricity

Load -> Uses Electricity

Switches -> Brakes or connects circuit

Connectors -> Transport Electricity

Electrical Potential = The amount of energy required to move a certain amount of current

Batteries = Convert chemical energy to electrical energy

Drycells use paste

Wetcells use liquid

Primary = Single use

Secondary = Rechargable

Electrons flow out of the negative to the positive in science.

In conventional current, current flows from positive to negative.

The negative side of the battery has excess electrons whereas the positive side of the battery has an electron deficiency.

Resistance = Measure of opposition to the flow of electric current

Resistors are loads, but not all loads are resistors

Potential difference = Difference in electric potential energy per unit of charge between 2 points

Kirchoffs Law

Current

Parallel = Current after a junction adds up to the current before it

Series = Current through the entire circuit is the same

Voltage

Parallel = Voltage drop is the same as voltage rise

Series = Voltage drops add up to voltage rise

Current will only flow if there is a load, branches only count if they have a load. Be careful though as wires have resistance too, just very little.

Voltmeters go in parallel

Ammeters go in series

Space:

Our Solar System

Our Sun

Our sun (Called Sol) is classified as a dwarf star and is a G-type star, meaning that it produces yellow-white light and is of middling temperatures.

110 earth diameter

1.3 million earths can fit inside

An object on the sun’s surface weighs 28x as much as an object on Earth

The surface of the sun is 5500K (5315C)

The core is 15 million C

Where does the sun get its energy?

Nuclear Fusion (Fusing H to get He)

Releases a large amount of light energy, heat energy and other types of energy

Converts 400 million tonnes of H into He per second

In a second, the sun makes more energy than humans have ever used.

Diagram of The Sun

Core: 15 million C, nuclear fusion happens here

Radiative Zone: ¾ of the way to the surface, thick layer of highly ionized and dense gasses (76% hydrogen, 24% helium) 

Convective Zone: Plasma moves in a… convective… motion

Photosphere: Boundary between inside and outside of the sun, coolest layer at 5500 C

Chromosphere: Looks red, can only be seen during a solar eclipse

Corona(Not the virus): Outermost layer of the sun, can be viewed during a total solar eclipse 

Solar Flares: Explosions caused by the magnetic field breaking through the surface 

Sunspots: A part of the sun that is cooler since the magnetic field slows convection

The Planets

A planet is defined as an object that is:

• Massive enough to be round from its gravity

• Not big enough to support thermonuclear fusion (Be a star)

• Have a clear orbit

There are 4 inner solar system planets, also called the rocky/terrestrial planets. They are made of rock.

• Mercury

• Venus

• Earth

• Mars

The asteroid belt separates the inner planets from the outer planets

There are 4 outer solar system planets, also called the gas giants and the ice giants. Jupiter and Saturn are made of gas (primarily hydrogen and helium). Uranus and Neptune are made of water, methane and ammonia. All of them are under alot of pressure so they are effectively just fluid giants.

• Jupiter

• Saturn

• Uranus

• Neptune

Dwarf planets

Dwarf planets are in the Kuiper belt other than Ceres.

• Ceres (In the asteroid belt)

• Makemake

• Haumea (Elliptical)

• Eris (Big)

• Pluto (Demoted to a dwarf planet in 2006)

Pluto

Pluto qualifies as a planet in the first two criteria, but it has debris in its path therefore it is a dwarf planet.

Moooooons

Moons are natural satellites.

A moon is classified as an object orbiting a planet or dwarf planet orbiting the sun.

Only Mercury and Venus don’t have moons

Earth’s one moon is called Luna

The Asteroid Belt

Region of space between Mars and Jupiter

Contains Ceres and thousands to millions of other objects bigger than 1km

Scientists estimate that the weight of the asteroid belt is no bigger than 1/1000th of Earth.

The Kuiper Belt

• Outside Neptune’s orbit between 30AU and 50AU

• Contains most of the dwarf planets

• Overall mass is 1/10 of Earth

• Most objects are frozen ammonia and methane.

The Oort Cloud

• Largely theorized region of space 1-1.8 light years across

• Believed to surround the sun spherically

• Contains trillions of small, slow-moving comets

• It, along with the scattered disc (Where Eris is) may be the origin of many comets

Comets

• Small icy objects

• Often have eccentric(Elliptical) orbits

• As comets pass the sun, ice is transformed to gasses which give the comet it’s tail, 

Distances in Space

Msun is the sun’s mass

Kilometers

• Too small

• Sun to Earth is 149,600,000 km

Astronomical Units (AU)

• Distance from the earth to the sun = 1 AU = 149,600,000 km

• Jupiter is 5.2 AU

• Pluto is 39.5 AU

Light years

• Speed of light is 299,792 km/s (3x108m/s)

• Most common unit of measurement for distance in space

• Light can travel around the earth 7.5 times per second

• A light minute is 17,987,520 km

• Earth is 8 light minutes away from the sun

• Nearest star (Proxima Centauri) is 4.2 light years away

• Our galaxy is 1.46*1017km across

• 1 light year ~ 9.461 Trillion kilometers

Telescopes

Hubble

• The Hubble deep field is looking at very far objects (Billions of light years)

• Clear, detailed views that look deeper into space and time than predecessors

• Observations from Hubble saw the evolutions of many extraterrestrial objects

• Confirmed the existence of black holes

• Found the farthest galaxies

• Verified the accellerating expansion of the universe

• Can see near Infared but is better for higher frequencies 

James Webb

• Largest and most advanced telescope ever built

• Can see farther away than Hubble

• Cuts through dust and gas using Infared

Life of a Star

Birth of a star

• Born in nebulae (Clouds of gas and dust)

• Gravity in the nebula pulls dust and gas together, making protostars

• Once they get hot enough, they become real stars

 Hertzsprung Russel Diagram

• Horizontal axis is surface temperature/colour

• Vertical axis is luminoscity

• Diagonal from top left to bottom right is the main sequence

• Most of their normal life is in the main sequence

• Main sequence stars are called dwarf stars

• The top right of the sequence is the giant categories

• Giants are old stars

• Bottom left is the white dwarfs

• White dwarfs are dead but still have some heat (Still glow a little bit)

Things to note:

• Bigger stars are hotter, brighter and have shorter lifespans

• If the star is very heavy, it increases it’s fusion rate since there is more pressure

• Even though big stars have more fuel, the fusion rate still gives it a short lifespan

Death of a Star

• When the star runs out of hydrogen, different things happen, depending on the mass

Low mass stars (<0.5 of the sun’s mass)

• Burns all the hydrogen until it becomes all helium

• Red dwarf

• Starts to collapse

• Shrinks until atoms are really tightly packed together

• Stops since 2 electrons can’t be in the same spot

• Called electron degeneracy pressure

• You get a white dwarf which gradually cools over time

• Heavier white dwarfs are smaller.

Mid mass stars (0.5x sun’s mass to 10x the sun’s mass)

• When they run out of hydrogen, they fuse helium into larger elements (Like carbon)

• Turns into a red giant

• Has a core of carbon(After fusing all the helium), and then collapses into a white dwarf 

High mass stars(>10x sun’s mass)

• When they die, they start with helium and make heavier and heavier elements until iron

• When the core is iron, the shell implodes until it hits the core, causing a supernova

Supernovae

• During the explosion, there is a ton of excess energy, which turns the iron into even heavier elements even though it loses energy

• All elements on the periodic table were made in a supernova

• Our star must be a population I star (Second or later generation) which lets us have heavy elements on Earth

• Our solar system is made of supernova debris

Stellar Remnants

*Note, many factors can affect this turnout. This is very simplified

• After a supernova there is always stuff left

• If the remnants have a mass of equal to or less than 1.4x the mass of the sun, it will become a white dwarf. The original star would have had a mass of less than 10 suns

• If the remnants have a mass of between 1.4 and 2.5 suns, it will become a neutron star. The original star would have had a mass of between 10 and 29 suns

• If the remnants have a mass of more than 2.5 suns, it may become a black hole. The original star would have had a mass of more than 29 suns.

Neutron Stars

• In a neutron star, the mass compresses so much that even electron degeneracy cannot support it.

• When this happens, the electrons fuse with the protons creating a star made of only neutrons

• This star has the same density as the nucleus of an atom which is up to 6x1017kg/m3

• One teaspoon of neutron star has a mass of 6 billion tonnes.

Black Holes

• The star is heavy enough that the neutrons are compressed and no forces can support against gravity.

• It collapses until it has no size. The matter collapses to a single point. It is called a singularity.

• Surrounding that point is the event horizon where once something enters it can’t leave. Even light can’t escape the gravity of the black hole.

The Big Bang Theory

Spectrography

• Each element has its own spectral lines.

• We can tell what a star is made of from its spectral lines.

How We See Galaxies Moving

• Galaxies like stars have specific colours

• Those colours are peculiar though

• Galaxies are moving away from us at an accelerated rate.

The Duck of Science

• When a duck is sitting in the water, the waves are equidistant

• When the duck is moving, the waves in front are shorter and the waves behind are longer.

The Doppler Effect

• This same thing happens with sound as with waves in a pond

• As a noisy object like a fire truck approaches, the waves are closer together meaning the sound is higher.

• As it leaves the waves are farther so the sound becomes lower.

• Light is also a wave

• Violet is the shortest wavelength, red is the longest.

• If a luminous object is moving towards us, the waves become shorter meaning it is blue shifted

• If a luminous object is moving away from us, the waves become longer meaning it is red shifted

• When astronomers look at galaxies through spectroscopes, they see the correct pattern, but they are red-shifted. Therefore they are moving away from us

• Since they are moving away, they must have started at a single point, hence the big bang.

Cosmic Background Radiation

• Another source of evidence for the big bang is cosmic background radiation.

• In 1965, scientists made an accidental discovery using a radio telescope.

• They detected unexpected radiation coming from every direction in space

• They concluded that this energy was remaining from the big bang.

What does the Future Hold

• There are 2 theories

• The universe will reach a maximum size and then collapse on itself causing the “Big Crunch” which would end up as one mass similar to the beginning.

• The universe will expand forever ending in the “Big Freeze” where all things cool to near absolute zero and perhaps end in the “Big Rip”

• The “Big Rip” hypothesis hinges on the belief that dark matter holds the universe together and is being stretched as the universe expands.

• Eventually it won’t be able to stretch anymore and attractive forces like gravity and magnetism will have no more power.

• Galaxies will come apart and then stars, planets and eventually atoms.

• Current observations lead scientists to believe that the universe’s expansion is accelerating due to dark energy meaning the universe will expand forever.

Galaxies

The Milky Way

• The milky way can be seen in dark clear skies away from artificial lights.

• The band of stars you can see are the billions of stars between us and the center of the milky way

• The dark smudgy band you can see is dust

• It comes from the greek “galaxias” which means “milky”

• Our galaxy is a spiral galaxy with a black hole in the center

• It is 100,000 light years across

• We are 25,000 light years away from the center

• It is 1,000 light years thick, but the bulge is 10,000

Star Clusters

• Groups of stars within galaxies are called star clusters

• Open clusters contain hundreds or thousands of stars

• Globular clusters contain hundreds of thousands of stars in a spherical shape

• Pleiades is the most famous open cluster with around 1000 stars. It is found in our galactic disk.

• M3 is a globular cluster of about 500,000 stars. It is found in the galactic halo

Speeds

• The earth spins at 1,600km/h at the equator

• To revolve around the sun the earth is travelling at 107,000km/h

• It takes the sun 225 million years to travel around the galaxy, meaning it is moving at 792,000km/h

• Our galaxy is moving at 2.1km/h through the universe compared to cosmic background radiation

• Speed of light is about 1B km/h

Dark Matter and Dark Energy

• It is thought that 90% of the universe's mass is invisible

• Dark matter does not emit or react to EM(electromagnetic) radiation

• Therefore we can’t see it with telescopes

• The reason astronomers believe it exists is because galaxies have unexpected motion

• The amount of visible mass doesn’t seem large enough to move the galaxies in this way

• For example, our galaxy is spinning so fast that one would expect the stars to be flung away, but they stay together.

Dark matter is thought to be around these galaxies and it is highlighted in blue.

• Dark energy is a concept to explain why our universe is accelerating its expansion

• Something must be pushing out on the universe which is explained by dark energy

Galaxy Shapes

Spiral

• Spiral and Barred spiral galaxies

• About half of all spiral galaxies have a bar

• New arms continuously form as old ones disappear

Elliptical

• Elliptical galaxies’s shapes range from being spherical to football-shaped to cylindrical and long

• They contain very little dust and therefore have few young stars

• Many are very old

Irregular

• Galaxies that arent spiral or elliptical are irregular

• This can be the result of two galaxies colliding or passing by one another

Galaxy Clusters

• A group of galaxies from typically 100 to 1000 galaxies would be a galaxy cluster

• Other notable galaxy clusters are:

  • Virgo Cluster

  • El Gordo cluster

  • Pandora cluster

Local Groups

• Small groups of galaxies are called local groups

• Our local groups has about 54 galaxies and is called “The local group”

And Beyond

- Star (Sol)

• Solar System

  • Galaxy (Milky Way)

    • Local group (Local group)

      • Local Cluster (Virgo Cluster)

        • Local supercluster (Laniakea supercluster)

          • Universe

The Drake Equation

The Drake equation was developed by Frank Drake in 1961 as a way to focus on the factors which determine how many intelligent, communicating civilizations there are in our galaxy.

The Drake equation is:

N=N*fpnef1fifcfL

• N* represents the number of stars in the Milky Way Galaxy

  • 100 billion

• fp is the fraction of stars that have planets around them

  • 20 – 50% (currently 100%)

• ne is the number of planets per star that are capable of sustaining life

  • 1-5 

• f1 is the fraction of planets in ne where life evolves

  • 50%?

• fi is the fraction of planets where intelligent life evolves

  • 50%?

• fc is the fraction of fi that communicate

  • 10-20%

• fL is the fraction of the planet’s life during which the communicating civilizations live

• Ie. For each civilization that does communicate, for what fraction of the planet’s life does the civilization survive?

• Ex: the lifetime of Earth’s sun is 10 billion years, and we’ve been communicating with radio for about 100 years.  How long will our civilization survive?  If we communicate for 10 000 years, the answer is 1/1 000 000

When all of these variables are multiplied together we come up with:

• N, the number of communicating civilizations in the galaxy.