THE SPACETIME CONTINUUM, GRAVITY, AND

LIGHT

Dimensions

A dimension is something that we use to help explain where a point in space is For example, the point below is at (2, 3) The elevator is at the

lower level (LL)

1 Dimension

If something exists in 1 dimension, we can describe where it is using only a line There is no height or width in 1 dimension,

only length

Number lines are 1 dimensional Example – The point is at -2

1 Dimensional Example

We describe our houses locations in 1 dimension much of the time.

For example, Mr. Sandor’s favorite restaurant is located at 325 3rd Ave N

Shapes are not possible in 1 dimension. There can only be 1 one line.

2 Dimensions

If something exists in 2 dimensions, we need to use 2 lines to describe where it is. A graph would be 2 dimensional. We need 2

lines to describe where a point is.

In 2 dimensions, there is length and height but no width.

2 Dimensional Example

We can describe where the school is located using 2 dimensions WMCI is located at the corner of Preston

Avenue S and Taylor Street

2 Dimensional Example

A 2 dimensional person would have no idea of “over” or “under” They also could not have a 1 way digestive

system because it would cut them in half

3 Dimensions

If you need to use 3 lines to describe something, it is 3 dimensional If something is 3 dimensional, it has length,

width, and height.

3 Dimensional Example We are 3 dimensions. We have length,

width, and height.

We can describe where someone is using 3 dimensions Example

Homer is on thecorner of Preston Aveand Taylor on the 3rd floor.

Space

The 3 dimensions we can move in are what make up space This is not space as in outer space. This is space as in the amount of space we

take up

If you move through space, what you are really saying is that you are moving through 3 dimensions

Time – The 4th Dimension

The 4th Dimension that exists is time

When we need to describe the position of an object using length, width, and height as well as describe where it is and where it used to be, this is 4 dimensions

4th Dimension Example

Mickey is on the Ferris wheel in London. He is riding for 10 minutes. He starts at

the bottom of the wheel

4th Dimension Example

After 5 minutes, Mickey is at the top of the wheel

Not only did Mickey move through space, he also moved through time.

Witnessing Time

We are 3 dimensional We live in (at least) 4 dimensions This means that we can control where we

move in space (3 dimensions) but we cannot control how we move through time We can witness ourselves move through time

in ‘moments’

Example Imagine a 2 dimensional

person

That person has no idea what ‘above’ or ‘below’ are.

Imagine a 2 dimensional person seeing a 3 dimensional object (like a balloon) They would only see

‘sections’ of the balloon. To a 2 dimensional person,

a balloon would first look like a dot, then a circle that grows larger, then a dot again.

Witnessing Time We are much the same as the 2

dimensional person We are 3 dimensional but see only

moments in the 4th dimension If we could see ALL of the 4th dimension,

we would see long ‘snakes’ that trail ahead and behind of everyone.

Spacetime

Space and time are both connected

You cannot move through space without moving through time You also cannot move through time without moving

through space

People often refer to space and time as one thing called Spacetime Continuum (or spacetime)

Everything in our Universe is moving through the Spacetime Continuum

Forces

As well as spacetime, our Universe also consists of 4 fundamental forces Strong Force Weak Force Electromagnetic Force Gravitational Force (or Gravity)

Strong Force This force holds protons

and neutrons together in the nucleus of atoms

It is the strongest force It has the shortest

range

• Weak Force– This force causes

radioactive decay (causes the nucleus to be unstable at certain times)

– It is the not as strong as the strong force

– It has a very short range

• Electromagnetic Force– This is the force that

causes magnets and electricity to attract and repel objects

– Only works on objects that have a charge

– Has an infinite range

• Gravitational Force– This causes any objects

with mass to be attracted to each other

– Effects all objects with mass

– Has an infinite range– Is the weakest force

Gravity and Space

Everything is space is very far apart only affected by forces with an infinite range

Not everything in space has a charge but everything has mass Not everything affected by electromagnetic force Everything affected by gravity

Because of these 2 reasons, gravity is the dominant force in the Universe Everything in the Universe was made and shaped

by gravity

How Gravity Works

Gravity causes anything with mass to attract any other object with mass

The Moon is attracted to the Earth by the Earth’s Gravitational pull The Earth is also attracted to the Moon

As the Earth pulls you down, you pull the Earth up

Gravity means that everything in the Universe is attracted to you, and you are attracted to everything in the Universe!

How Gravity Works

Gravity depends on how much mass an object has The greater the mass, the greater the

gravitational pull

How Gravity Works Mass causes gravity

by distorting (bending or reshaping) spacetime

Imagine spacetime like a giant sheet of fabric If you add mass on the

fabric, the sheet will droop

If you add greater mass onto the fabric, it will dip even further down creating a ‘well’

Curvature of Spacetime

Spacetime is actually curved and reshaped by all of the mass around it This curved nature

creates gravity This means that

even though it looks like a straight line from here to a star, it may actually be a curved path

Why Doesn’t the Earth Fall into the Sun?

The Earth has enough velocity (speed) to keep going without ‘falling’ into the Sun This is also why the Moon doesn’t run into the

Earth

The Extreme of Gravity

One example of extreme gravity is a black hole A black hole is something that has so much

mass packed so tightly that it pulls everything close to it strongly to the point that even light cannot escape its gravitational pull

Light Light is both a particle and a

wave

We call the particles photons

To understand space, we need to understand light Light is how we observe space.

We look at the light given off by stars and galaxies. We examine the colours of light that reflect of planets, moons, and nebula. This is how we learn about space is through light

Light

Light acts as a wave.

Every wave has some properties that we need to know Wavelength Amplitude

Waves Waves go up and down over time.

Waves transmit energy

Amplitude is how high or low a wave goes Amplitude is what determines how powerful a

wave is It is often referred to as peaks (ups) and

troughs (downs)

Waves

The wavelength of a wave is how long it takes for a wave to complete a cycle The length from peak to peak or trough to

trough

The shorter the wavelength, the greater the energy

The longer the wavelength, the less energy

Light Waves

The amplitude of a light wave determines brightness A 100W light bulb gives out

light with greater amplitude than a 40W light bulb

The wavelength of a light wave determines the energy and the colour The shorter the

wavelength, the higher the energy

The longer the wavelength, the less the energy

Colours of Light

The colour of the light is determined by how long a wave is. Shorter waves

look blue Longer waves

look red

Light There is more light than what our eyes

can see We see a tiny portion of all the light that

exists. We only see visible light

Other forms of light include X-rays, gamma rays, radio waves, microwaves, infrared, ultraviolet

Atoms and Light

Each element gives off its own colours Each element emits and absorbs specific

colours of light This is why copper burns green and strontium

burns red

We can determine what stars, planets, nebula, etc. are made of by the colours of light they emit

Light and Space

Waves must travel through a medium Ocean waves transmit energy through water Sound waves transmit energy through air Light waves transmit energy through space

Light travels through space so it is affected by gravity’s bending of space

The Speed of Light

Nothing can travel faster than the speed of light

The speed of light is like a cosmic “speed limit” If things get fast enough to approach the

speed of light, other values such as time, length, and mass of an object will change

Light moves at 300 million metres per second

Light-years

Light takes time to travel from one place to another It takes 8 minutes for light

to reach Earth from the Sun

To measure distant objects we use the measurement light-years Light years are the amount

of distance light travels in 1 year – about 9.5 trillion kilometres

Light-years The nearest star to Earth

other than the Sun is Proxima Centauri 4.24 light years from Earth

When we see Proxima Centauri, we are actually seeing what it looked like 4.24 years ago That is the amount of time

it takes light to get here from that star

Light-years

The furthest object from Earth ever seen was 13.37 billion light-years This means it took 13.37 billion years for the

light to travel to Earth for us to see it. This object was a protogalaxy – a cloud of

gas that began to form one of the first galaxies