How much does this represent the early universe?
Time doesn't permit covering all of this page.
It is 4019. You settle down to writing to friends at the other end of the universe.
(Readers suspend disbelief as our subject is using snail mail.)
You enclose an SAE thus:
Mr & Mrs J Smith
7 Church Green
Witney OX28 4AZ,
Oxfordshire,
United Kingdom
Europe
Northern Hemisphere
Earth
Solar System
CONTENTS
1 The scale of the Universe
2 The Hubble Telescope
3 Cosmology
4 Was there a time before the Big Bang?
5 "singularity"
6 The Milky way
7 One hundred billion galaxies
8 The most detailed image of the universe ever created
9 What is the diameter of the observable universe?
10 Photo of a nebula
11 The "eye" nebula
12 An artistic? nebula
1 The scale of the Universe
- Contemplating the scale of the Universe is a daunting task.
- One starting point is to think about Earth’s place within it by imagining our ‘cosmic address’. ..rather than writing down a house number, street, town and country, we replace each line with larger structures in space.
- Our cosmic address starts with our planet, Earth, which is one of several planets within the Solar System.
- The star at the heart of the Solar System, the Sun, is one of around 200 billion stars in the Milky Way and in turn, our galaxy is one of about 200 billion in a cluster called the Local Group.
- This combines with other galaxy clusters to form the Virgo Supercluster and finally this Supercluster is just part of a vast region in space called Laniakea, which contains around IOO million billion stars.
- This means that our cosmic address is: Earth, Solar System, Milky Way Galaxy, Local Group, Virgo Supercluster, Laniakea.
- Even if we understand where we fit within the Universe, understanding its scale is another matter. For such vast distances, everyday units of measurement such as kilometres or miles are not useful.
- Instead, astronomers use a unit called a light year: this is the distance that light can travel in one year.
- Since light has a speed of 3OO,000km/s, the distance it travels in a single year is 9.5 trillion km.
- Travelling at this speed, you could fly around Earth seven and a half times in one second!
- Now imagine travelling from your house to the next street, or even the next town — but doing this with your cosmic address.
- .......
- The Milky Way is 100,000 light years across.
- But largest of alI, the Universe — with its estimated 10 trillion galaxies — is an unimaginable 93 billion light years wide.
Planetarium: Chris Wormell & Raman Prinja. 2018,
Big Picture Press. here p 1
Note re 1.15 & 1.17
- The light-year is a unit of length used to express astronomical distances and measures about 9.46 trillion kilometres ... or 5.88 trillion miles
- ..
- As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). ...
- Because it includes the word "year", the term light-year is sometimes misinterpreted as a unit of time.
- However, if something emitting light is 2 million light years away, it's taking that long for the light to arrive.
- The light-year is most often used when expressing distances to stars and other distances on a galactic scale, ...
2 The Hubble Telescope
- The universe is approximately 13.8 billion years old.
- The Hubble Telescope uses the the universe’s expansion rate to determine its age.
- Hubble and the European Space Agency’s Gaia space observatory calculate this rate by measuring the distances between nearby galaxies using a special type of variable star as a cosmic yardstick.
- By studying the local universe, they’re measuring the recent rate of the universe’s expansion.
- This is like measuring the speed of a car and how far it has gone to find out how long it has been driving.
3 Cosmology
- The Universe encompasses everything there is: all of time, energy and every bit of matter in space, from the tiniest asteroids to the biggest galaxies.
- Its scientific study is called cosmology, which seeks to answer some of our most profound questions, such as how the Universe began, how it will end and whether there are other universes beyond our own.
- In order to do this, cosmologists create models for their theories, which make it possible to visualise and predict phenomena we could never possibly observe, including the very earliest days of the Universe.
- These models can then be put to the test by comparing them with observations of galaxies and stars.
- As our understanding of space evolves, some models are cast aside, while newer ones are constantly emerging. ......
- The main revolution in cosmology began in 1915, when Albert Einstein published his General Theory of Relativity.
- He outlined that massive objects, such as stars and galaxies, cause space to sag or bend around them — the way a large adult standing on a trampoline will make it sag down.
- Using Einstein's equations, the Belgian physicist Georges Lemaitre deduced that the Universe is expanding.
- Meanwhile, in 1929, Edwin Hubble's observations from the Mount Wilson Observatory in California, USA, revealed that galaxies were rapidly moving away from each other.
- Lemaitre used Hubble's discovery as evidence for what we now call the Big Bang theory — our prevailing model of the Universe.
- This model depicts a Universe that began around 14 billion years ago, has no centre, and has been evolving ard changing ever since its birth.
Planetarium: Chris Wormell & Raman Prinja. 2018, Big Picture Press. here P 84
In the beginning . .
4 Was there a time before the Big Bang?
Stephen Hawking has said that:
- "Since events before the Big Bang have no observational consequences,
- one may as well cut them out of the theory, and say that time began at
- the Big Bang.
- Events before the Big Bang are simply not defined, because there's no
- way one could measure what happened at them." source
- The Big Bang Theory is the leading explanation about how the universe
- began.
- At its simplest, it says the universe as we know it started with a small
- singularity, then inflated over the next 13.8 billion years to the cosmos
- that we know today.
- Too many books, papers, www announcements etc include terms
- not explained.
Here we have
5 "singularity".
The initial singularity was a gravitational singularity of seemingly infinite density thought to have contained all of the mass and space-time of the Universe.
We could explore space-time, quantum fluctuations and mass. However,
not on this website. Even inflation is more than meets the eye. more
>>>>
A singularity is what you end up with when a giant star is compressed to an unimaginably small
point.
It refers to the end of
a star but also something more fundamental: that a
singularity was the starting-point for the
formation of the entire universe.
Blue text from >>>> above is from the Transcript of Stephen Hawking's first Reith Lecture broadcast 26.01.2016 source
However, there were no stars to be compressed which makes the big bang an exceptional singularity,
- The Universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.
- While the spatial size of the entire Universe is unknown, it is possible to measure the size of the observable universe, which is currently estimated to be 93 billion light years in diameter.
- Source
- (Diameter 8.8×1026 m source)
- Space is the boundless three-dimensional extent in which objects and events have relative position and direction. Not so.*
- Physical space is often conceived in three linear dimensions.
- Source. .
- Not so. "Spacetime" is the forth dimension in space time.
- No time to delve. Very complicated.
- *
- Let's start with the three dimensions most people learn in grade school. The spatial dimensions—width, height, and depth—are the easiest to visualize. A horizontal line exists in one dimension because it only has length; a square is two-dimensional because it has length and width. Add depth and we get a cube, or a three-dimensional shape.
These three coordinates are used to pinpoint an object's location in space. But space isn’t the only plane we exist on; we also exist in time, which is where the fourth dimension comes in. Once we know a dot's altitude, longitude, latitude, and position in time, we have the tools needed to plot its existence in the universe as we know it.
source
6 The Milky way
- When confronted with the topic of stars and galaxies, a question that tantalizes most humans is, “Is there other intelligent life out there?” Let’s put some numbers to it—
- As many stars as there are in our galaxy (100 – 400 billion), there are roughly an equal number of galaxies in the observable universe
- so for every star in the colossal Milky Way, there’s a whole galaxy out there.
- All together, that comes out to the typically quoted range of between 1022 and 1024 total stars, which means that for every grain of sand on every beach on Earth, there are 10,000 stars out there.
10,000,000,000,000,000,000,000,000 = 1024
7 One hundred billion galaxies
- According to the best estimates of astronomers there are at least one hundred billion galaxies in the observable universe.
- They've counted the galaxies in a particular region, and multiplied this up to estimate the number for the whole universe.
8 The most detailed image of the universe ever created
