The Big Bang Theory
Scientists have evidence that indicates our Universe (including all the stars, galaxies and planets) began about 13.7 billion years ago. The illustration on the right helps to show how the Universe expanded from a tiny "singularity" we call the "Big Bang", which was no bigger than an electron, into the infinitely large Universe we know today. And the Universe continues to expand! To get a blow-by-blow explanation of the events, click on the History of the Universe image to go to the NOVA website that describes it in more detail. Once you get to that webpage, click on the button that says "Launch Interactive"
The image on the right is another way of showing how the Universe inflated and then expanded over time.
Journey to the Edge of the Universe
Barred spiral galaxy. Click on the photo to go on a tour of the universe
Looking deep into the universe with the Hubble Space telescope, you can see galaxies 46 billion light years away.
A "light year" is how far light will travel in a year or, ~6 trillion miles. To give an idea of how fast that is, imagine that we could flip a switch to turn off the sun. The sun is about 93,000,000 miles away from Earth. [For comparison, the distance across the United States is 3,000 miles.] The speed of light is 186,000 miles per second. By "turning off" sun, we would have to wait about 8 minutes to notice that the light has gone out.
Stars and galaxies are "light years" away, which means that when a star in a galaxy only 1 light year away is "turned off", we would have to wait an entire year before we noticed here on Earth. That's why telescopes are often called time machines. We can look back in time by looking at light that left a distant star billions of light years ago. The Hubble Deep Space image (seen further below) shows the light from galaxies over 13 billions light years away - meaning the light that was captured in the image left the stars and galaxies 13 billion years ago.
The video above explains how the history of the Universe. It still is a little technical, but I haven't found a really good one yet.
By clicking on the image of the "barred spiral galaxy" to the left, take a trip past our solar system, past the Milky Way galaxy, past our Local Group, past other clusters of galaxies, deep into the cosmos and back in time to 10 billion years ago. But we can see further than that - almost 14 billion light years away. Click here to get an idea of how big our universe is.
Comparing all of time to a one year calendar
The image below compresses 13.7 billion years since the Big Bang into a one calendar year. Note that life appears in "September", but humans do not arrive until 6 minutes to midnight on the last day of the year!
If all of time since the Big Bang was compressed into one year, this is what the calendar of events would look like. Notice that humans don't appear until the last hour of the last day and the pyramids were built in the last 10 seconds of the year! Click on this picture to view a beautiful website that shows the timeline as a "Wall of Time"
Galaxies come in different shapes or 'morphologies'
(Credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team)
This is an image taken by the space telescope Hubble is called the Extreme Deep Field image, reveals 5,500 different galaxies of different sizes and shapes. The light of some of the galaxies in this photo started traveling towards us as long as 13.2 billion years ago! If you wish, you may click on the image above to get more information about it. You may also click on this HubbleSite link that has a short movie and other pages about the Deep Field image.
Examples of different types of galaxies
Earth's location in the Universe
Earth is located the solar system, which orbits our Sun. The sun is but one of billions of stars located in one arm of the Milky Way Galaxy. The Milky Way galaxy belongs to a group of about 30 galaxies in the universe called the Local Galactic Group. Andromeda galaxy is also in the Local Galactic Group and is also a spiral galaxy with over a trillion stars. The Local Galactic Group belongs to a a much larger "supercluster" of galaxies called the Virgo Supercluster, which belongs to a group of local neighboring superclusters. Click on the image to see a closer view of each image below.
In a way you can compare this to our own geography.....
Solar Interstellar neighborhood
Milky Way galaxy
Local Galactic Group
How our Sun & Planets were Formed
Our sun is an "average" star, not too big, not too little. Because stars are "born, live & die", it's nice to have a star that is just right. It is the size that will allow it to "live" for about 8 billion years. Right now, it's about halfway through it's life cycle. But we should also be happy that there are giant stars (called red giants), whose lifespans can be very short. When they "die" or explode into a supernova, that explosion can create all the elements that come back together to make up our earth - even us! Indeed, we are made of the stardust from a supernova explosion of a giant star.
Below is a wonderful view of such an exploding star taken this month (Jan. 2014). It's the best known image of a supernova to date, because it shows the earliest stages right after the explosion. The image on the left is the actual photo, while the image on the right is an artist's illustration of that photo.
Below is a wonderful view of such an exploding star taken this month (Jan. 2014). It's the best known image of a supernova that shows the formation of the dust during the earliest stages after the explosion. The image on the left is the actual photo, while the image on the right is an artist's illustration of that photo.
Telescopes have been looking at this red giant star for several years, and below you can see the images of that red giant as it after it sent off an explosion and created light "flashes". You can see the dust from previous explosions expanding away from the red giant over time. This red giant has NOT gone supernova (or completely exploded), though.
The video below tells how a star is formed within a nebula, and how planets such as Earth then form around the star.
A photograph of a protoplanetary disk about 450 light years away. The reddish 'stellar jet' is formed as strong winds push out gases from the center of the rotating disk.
Young stars (or protostars) typically form from clouds of hydrogen gas and dust. Our own sun is believed to have been made up of the remains of a much larger star that exploded (or went supernova). When a part of the cloud reaches a large enough size or density, it begins to collapse under its own gravity. As this collapsing cloud, called a solar nebula, becomes more dense, the gas begins to rotate and flatten out, and take the form of a disk—much like forming a flat pizza out of dough—, called a protoplanetary disk.
The gases in this disk start to gather together ( like our pepper demonstration) to form the beginnings of small young planets, called planetesimals. As they circle the newly forming star, gas and dust gather and collide. As THEY become larger, they have enough gravitational pull to attract other planetesimals, which gather together to ultimately form planets.
When the protosun becomes hot enough from the pressure, it ignites into a star
History of Earth
This is a very long 90 minute video documentary about the history of the earth. You do not need to watch this, but it is interesting if you have the time