Upload
owen-robertson
View
221
Download
0
Tags:
Embed Size (px)
Citation preview
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