Tag Archives: Moon


3/4B, 4T and 3SF visited the Penrith University of Western Sydney Observatory and share their experience in a blog post. They also asked questions and I loved the challenge of trying to answer them. To see their post…

Bloggers of the Week: Our Excursion to the Observatory

To see Part 1 of this comment...

Observing Space, there’s so much of it out there – Part 1

Hello 3/4B, 4T and 3SF,

Here are some possible answers to the second set of questions.

1. How many more years until we have to pack up and move to another planet, because the sun died?

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Firstly, let's look at how our Earth is thought to have come to be. Heather and Keira from California had challenged me to explain how the Earth had begun. Here is a link to the post I wrote for them if you are interested.

How Did the Earth Begin?

... and here is a link to a Wikipedia post looking at history of the Earth. It is about  Earth from its formation to now.

History of the Earth

Okay, we have an idea how our Earth began but how might it end? As our planet's birth was linked to the formation of our sun, the sun is also involved in its suspected end.

Back in 1987, I was able to look into the night sky and see a "new" star. A star astronomers named SN 1987A had gone supernova. It is about 168,000 light years* from Earth and could not normally be seen without a powerful telescope. It is again too dim to be seen without a telescope. Had it been our star, our planet would have been destroyed.

Then what about our Sun? How old is it? What might happen to it? When might it happen?

This is a NASA photo released into the public domain. It was sourced through Wikimedia Commons. http://commons.wikimedia.org/wiki/File:The_Sun_by_the_Atmospheric_Imaging_Assembly_of_NASA%27s_Solar_Dynamics_Observatory_-_20100819-02.jpg

This is a NASA photo released into the public domain. It was sourced through Wikimedia Commons.

Our Sun is thought to be about 4.6 billion (4,600,000,000) years old. I had to do a little research about the Sun to find out what might happen. I found interesting information suggesting our Sun is becoming brighter by about 10% every billion years and it's surface is slowly becoming hotter. As it gets older and burns more of its hydrogen fuel it will grow in size to eventually become a red giant. By this time Earth, if it still exists, will not be able to support life.

The video clip below shows what might well happen when our to end of world. Duration: 3:04 minutes.

It replaces the original linked video clip now blocked from viewing in Australia due to copyright issues.

This is not my video clip.

Should we worry?

It is thought it could take about 5 billion (5,000,000,000) years before our Sun is a red giant and perhaps 1 billion (1,000,000,000) years before the Sun's rising temperature means all water will evaporate away from Earth. A billion years is a very long time. However humans develop in that time, we can only hope they have solved the problems. For a time until the sun gets too big or hot this might mean people moving to Mars but to go to other stars people might have to spend a very long time in space. By the time people reach other stars, they could be the great, great, great, great,... great, great, great, grandchildren of those who left Earth.

But I've seen movies where they move through gates or hyperspace at faster than the speed of light and arrive quickly...

The movies love finding ways to arrive quickly. Who knows what science might discover in a billion years. For now, the idea of travelling close to the speed of light is beyond us. Whatever the future brings, I have faith humans will find a solution if there's one to be found. I know NASA engineers are looking at ways it might be one day possible to warp space and make travel to the stars real. 🙂

168,000 light years* - as explained in Part 1, a light year is the distance light travels in a vacuum in one Earth year. While I saw the supernova as a bright star in 1987, the light had started on its way 168,000 years ago. When we look at stars, we are looking back in history. Even light from our own sun started its journey about 8.3 minutes before we see it.

2. Did you know that there are many different galaxies in space?

Yes. Too quick an answer? 🙂 I'll share some NASA galaxy photos using links.

The two galaxies shown here are in the early stage of an interaction that will eventually lead to them merging in millions of years. The two galaxies are about 450 million (450,000,000) light years from us. If you look carefully you can see other galaxies in the distant background.

UGC 9618, Chandra + Hubble

By Smithsonian Institution [Public domain], via Wikimedia Commons

This second photo shows galaxy M33. It is about 3 million (3,000,000) light years from Earth. The really bright stars are young, very large stars. Yes, stars are still being made in our universe from the remains of other stars.

Galaxy M33 Chandra X-ray Observatory

By Smithsonian Institution from United States [see page for license], via Wikimedia Commons

The third photo shows galaxy Centaurus A. If you can see what looks like a line of white light coming from its centre, that's the result of Centaurus A having a supermassive black hole at its centre.

Centaurus A Chandra

By NASA/CXC/CfA/R.Kraft et al (http://chandra.harvard.edu/photo/2008/cena/) [Public domain], via Wikimedia Commons

Galaxies are not all one size. Dwarf galaxies might only have as few as 10 million (10,000,000) stars whereas giant galaxies might have up to 100 trillion (100,000,000,000,000) stars. There are estimates the might be up to 170 billion (170,000,000,000) galaxies in the observable universe . There may be very many more but they are so distant their light still hasn't reached us, they're not yet observable. That's a lot of galaxies.

I like looking at big numbers so let's look at big numbers. I have said their might be 170 billion (170,000,000,000) galaxies in the observable universe. I also said galaxies could have from 10 million to 100 trillion stars. Let's say the average galaxy has 1 billion (1,000,000,000) stars.

How many stars might their be in the observable universe?

170,000,000,000 galaxies x 1,000,000,000 average stars = 170,000,000,000,000,000,000 (I make that 170 quintillion stars.)

In Part 1 of these answers to your questions I mentioned it has been said there are more stars in the universe than all of the grains of sand on every beach on Earth. Would one of you start counting so we can check? 🙂

Below is a You Tube video clip from NS showing galaxy M31 known as the Andromeda Galaxy. It is the nearest large spiral galaxy to our own. Our galaxy, The Milky Way, is also a spiral galaxy. Duration: 3:06 minutes

This is not my video.

3. Did you know that Pluto has 2 more moons?

Yes, but I found there seems to be more discoveries when I was researching. In order of distance from Pluto they are Charon, Styx, Nix, Kerberos, and Hydra. It is possible more small "moons" might be found. Click to read Moons of Pluto on Wikipedia.

In this photo taken by NASA in 2005, the two dots listed as candidate satellites
Pluto system 2005 discovery images

When Pluto was discovered in 1930, its brightness suggested it was much larger than it was found to be but that was because it is icy. Charon was discovered in 1978. I always found its name was a great choice. In ancient Greek mythology, Pluto was the god of the underworld where people went when they died. To reach there, you had to cross the River Styx. This could only happen if you had a coin to pay the boatman, Charon. It was common for ancient Greeks to bury their dead with a coin so they could pay Charon. This is why I thought the name is a good choice. Pluto and Charon are together in ancient Greek mythology.

One unusual piece of information I read was about Pluto and Charon. Moons orbit around their planet as does our moon but Pluto doesn't seem to be the centre of Charon's orbit. The centre of orbit is somewhere in between but closer to Pluto. What a strange place Pluto would be.

While searching online, I found an animated file showing a computer generated rotating image of Pluto you might like to see. It's based on NASA images of the surface of Pluto. This an embedded NASA file in the public domain.

Pluto animiert 200px
By Aineias, NASA, ESA, and M. Buie (Southwest Research Institute)  derivative work: Aineias, Ilmari Karonen (Pluto_hubble_photomap.jpg via Pluto_animiert.gif) [Public domain], via Wikimedia Commons

4. Did you know that Neptune's ring is made out of ice particles?

Below is my favourite image of Neptune. NASA released this image into the public domain. Neptune's atmosphere seems to be mostly hydrogen and helium. "The interior of Neptune, like that of Uranus, is primarily composed of ices and rock." (Wikipedia). Remember, ices aren't necessarily only water. Have you heard of dry ice we can buy here on Earth? It isn't water. It's icy carbon dioxide. For Neptune, the ices are thought to be mostly water, ammonia and methane. The core of the planet is said to be rocky.


By . (http://photojournal.jpl.nasa.gov/catalog/PIA00046) [Public domain], via Wikimedia Commons

The next NASA image was taken by the Voyager 2 and shows the rings on Neptune.

Neptune rings PIA02224

By Courtesy NASA/JPL-Caltech (http://photojournal.jpl.nasa.gov/catalog/PIA02224) [Public domain], via Wikimedia Commons

The rings are thought to probably contain large amounts of micro-dust as well as ice.


5. Did you know that it takes 1 month for the moon to orbit around the earth?

Wikipedia reference for the different types of months and years: Month

This embedded graphic shows the phases of the Moon seen as it orbits the Earth. Do you notice we only see one side? The other side is often called the dark side. It also comes into sunlight but, since it faces away from Earth, we don't see it.

File:Lunar libration with phase Oct 2007 450px.gif

This work has been released into the public domain by its author, Tomruen. This applies worldwide.

This is an interesting question even if it sounds simple. Rather than say "yes" or "no", I might ask what type of month?

I know the months we talk about run from January to December. February has 28 days or 29 in a leap year. The others have either 30 or 31 days. The average number of days in a month is about 30.4 days. If you mean one of our Gregorian Calendar months we use, the answer is not quite a month.

When compared to the position of stars, the Moon takes about 27.3 days to orbit the Earth but Earth is also moving through space so the time between two full moon is about 29.5 days.

Did you know there was something known as a lunar calendar?

The calendar we use is a solar calendar. It's based on the time it takes for the Earth to complete one orbit around the Sun. Lunar calendars are different because they are based on cycles of the Moon.

Many cultures have had lunar calendars.  One of the important examples is the Islamic Calendar. A year has either 354 or 355 days where as the Gregorian Calendar has 365 or 366 days based on a solar year. If you have Muslim friends, you might know the first day of their new year is a different day on our calendar each year. This happens because their lunar year is 11 days shorter.

The Gregorian solar year has an average of about 30.4 days per month giving us about 365 days a solar year.

The Islamic lunar year has an average of about 29.5 days per month giving us about 354 days a lunar year.

Can you see the solar calendar gives us about the time it takes for the Earth to complete an orbit of the Sun while the approximate number of days in a lunar month is how long it takes the Moon to go from one full moon to the next?

The embedded diagram below shows how the phases of the Moon come about while the Moon orbits Earth.

Moon phases en

By Orion 8 (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

6. Did you know that (it takes) a year for the earth to orbit around the sun?

Our Gregorian solar calendar is based on how long it takes the Earth to complete one orbit of the Sun, that is it takes about 365.25 days for Earth to orbit the Sun. We call that a year of 365 days with a leap year helping us catch up on the extra bits by having an extra day.


By Adam850 at en.wikipedia [Public domain], from Wikimedia Commons

What would a year be on other planets and dwarf planets?

Here are the other planets and known dwarf planets in our Solar System with how long their years would be in our Earth years (Ey).

Mercury ....................... 0.24 Ey (88 days)

Venus ........................... 0.62 Ey (226 days)

Earth ............................ 1.0

Mars ............................. 1.88 Ey

Ceres (dwarf) ............... 4.6 Ey

Jupiter .......................... 11.86 Ey

Saturn ........................... 29.46 Ey

Uranus .......................... 84.01 Ey

Neptune ....................... 164.8 Ey

Pluto (dwarf) ................ 248.09 Ey

Haumea (dwarf) .......... 282.76 Ey

Makemake (dwarf) ...... 309.88 Ey

Eris (dwarf) ................... about 557 Ey

A little extra...

In July last year a class asked some questions about space. I didn't add and pictures to the post but you might like to see their questions and my answers...

Wonderings About Space

* * * * * * * * * *

And one final You Tube video clip answers,

"What Is Space?"

Duration: 55:43 minutes

This is not my video clip.


I had written a post on plate tectonics and continental drift for Mrs. Yollis and her class. Two students, Heather and Keira, challenged me to explain how the Earth began. This post is an attempt to provide an explanation according to my understanding of the science. To see the comment and challenge, click the link and scroll down to the comments.

Plate tectonics and our dynamic continents

How Did the Earth Begin?

Dear Heather and Keira,

There are so many stories of how the Earth began if we look though the amazing cultures in our world. It would be remiss of me not to mention one or two. Because of my home and yours, I have chosen stories from the native people of Australia and North America.

The Aboriginal People of Australia

Many people think there was one Aboriginal (native Australian) culture and one language but, before the coming of European colonists, there were many, many of those cultures now lost. One of the best sites I have seen comes from the Yolngu people of Ramingining in the northern part of Central Arnhem Land in Australia's Northern Territory.

For one of their creation stories, click the link Twelve Canoes and wait for the site to load. The picture below will appear. Once loaded, click on the picture indicated by the arrow to see a creation story.

This graphic should not be copied.

I think you will find many interesting things on this site as well as one of their creation stories.

Native American People

I found the following You Tube clip telling the story of creation of the Earth through the traditional beliefs of three Native American tribes, the Iroquois, Seminole and Cherokee.

This embedded You Tube clip is not my video.

Let's now start looking at what science is finding...

Let's start with some word learning. You have had many ideas in your life but have you ever heard someone say they have a theory? Many people confuse "idea" and "theory".

A scientist has an idea after looking at the information available through study or research and proposes an explanation for what has occurred. Other scientists look at the conclusions and test the idea against other data or new information. This may lead others to agree with the idea. With other scientists agreeing and available evidence supporting, the idea becomes a theory. Science is a path to discovery. We learn more and more about how things work.

Did you know up until a few hundred years back people thought the Earth was the centre of the universe and all of the stars, planets and our Sun orbited around us? This idea is called Geocentric.

A Geocentric View of the Universe

This drawing is based on a map by Bartolomeu Velho (1568)

Schools and students have permission to use this graphic for non-commercial, educational purposes.

A second geocentric model has Earth at the centre of the universe. The other planets orbit the sun and the sun and all the planets orbit the Earth.

It wasn't until about the 1500s more and more evidence was being gathered to show Earth isn't at the centre of the universe. It is a planet orbiting our Sun and now we know our Solar System is towards the outer edge of a double spiral galaxy we call, The Milky Way. We also know our galaxy is one of very many, probably billions, in our universe. We know this because of what scientists have been able to observe and because of the theories arising.

Watch the below video to see an explanation of what is thought to have happened to form our planet and others in our Solar System. Remember, you can click on the small box symbol on the bottom right of the video to watch full screen.

 Now let's look at the information in the video

* About 9 billion (9,000,000,000) years after the universe was born a massive start went Supernova - A supernova is an explosion of a star. It might have been caused by the collapse of the massive star's core. Radiation, energy and stellar dust explodes out from the collapsed star. Back in 1987, we were able to look into the sky and see a supernova astronomers named SN 1987A. Where once nothing could be seen, a star bright enough to be seen without a telescope had appeared. It is said to be 167,885 light years distance. This means the light took 167,885 years to reach us. The supernova happened a very long time ago.

* Gravity began its work on regions of the massive dust "cloud" sent out. The "cloud" particles started to gather. Pressure and heat increased. Our Sun was being formed.

* The temperature increased to about 10 million (10,000,000) C or about 18,000,032 F. About 4.5 billion (4,500,000,000) years ago our sun lit up.

* The Sun used much of the "cloud" leaving only 0.1%. Look at this picture. Imagine the cloud was made up of 1000 students in a school. 999 of them would go to make up the Sun. Just one of them would be left to make all of the planets and asteroids in the Solar System. The little guy in red looks a little lonely. 🙂

Schools and students have permission to use this graphic for non-commercial, educational purposes.

* The left over material was caught in the pool of the Sun's spinning motion. The left over material was spinning (orbiting) around the sun. The spin and gravity of the sun was drawing the material into rings (like Saturn's gravity has drawn material into rings around it). The way the material was orbiting the sun stopped it from being pulled into the Sun. I know this can be hard to understand so look at the next graphic I have prepared.

Imagine you are the Sun. You have a long, strong elastic attached to a tennis ball and you are spinning it around your head.

The ball is orbiting you. The elastic is your gravity trying to pull the tennis ball to you. The tennis ball is one of the planets. If the movement of the ball slows, the elastic draws it closer. If the ball moves faster, the elastic stretches further. Yes, in case you wonder, if the tennis ball was instead a basketball, the amount of stretch would be bigger.

Jupiter is said to be 317 more massive than the Earth. Imagine trying to spin 317 tennis balls on the end of the elastic. You wouldn't need to spin the balls as fast to keep the elastic as stretched as one tennis ball. Our Earth takes one year to orbit the Sun (that's what a year is, the time it takes our Earth to go once around the Sun). Jupiter takes about 12 years. If you could spin the tennis balls fast enough, the elastic would break and "Jupiter" would sail off into space.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

* The debris in the rings around our sun started to collide and come together to form larger masses. Their journey to becoming planets had started.

Have you heard of the asteroid belt between Mars and Jupiter? This ring of debris wasn't able to form a planet because it was being pulled from two sides, the Sun and Jupiter, the largest of our system's planets. Our ring was able to produce a planet which is fortunate for us or I wouldn't be writing this.

* From 4.8 to 3.5 billion years ago (4,500,000,000 to 3,500,000,000 years ago), the Earth was being bombarded from space. Combined with this bombardment, radioactive elements and pressure, Earth became a molten furnace. Heavier minerals like iron and nickel sank into the core and lighter minerals rose to the surface.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

You have probably seen how certain things float while others sink. If you drop stones or pieces of metal into a container of water, they sink to the bottom because they are heavier. Put in olive oil and it will float to the top.

* Around this time a large object about the size of Mars collided with our early Earth. Part of the collided matter broke off to eventually become our moon. The Moon at first was much closer to our planet.

Remember the elastic experiment? Earth's "elastic" isn't quite strong enough so it is gradually "stretching" but the Moon isn't expected to break away, just reach a distance where there is a balance but this is billions of years into the future so we needn't worry.

* Because of all of the heat and volcanic activity throwing out gases, Earth's atmosphere was mostly nitrogen, water vapour and carbon dioxide. We couldn't have survived the heat let alone the poisonous atmosphere.

* As the bombardment of debris from the creation of the Solar System reduced, Earth's surface started to cool. Water vapour cooled and the first ancient ocean formed. The cooling crust of the Earth formed the first land, Pangaea. Remember the layers of the Earth?

Schools and students have permission to use this graphic for non-commercial, educational purposes.

In the  final video clip at the end f this post you will hear it said, if the Earth were a basketball, the crust would be thinner than a piece of paper on its surface yet that's where we live.

* The Earth had an atmosphere and water, conditions needed for the first life but that is another story.

Are there any other systems with planets or are our Solar System planets the only ones? Is there life on other planets in our universe?

I have a favourite quote from a man called, Carl Sagan. He was an astronomer, astrophysicist, cosmologist and author. He wrote a novel named "Contact". The quote comes from his book...

"The universe is a pretty big place. If it's just us, seems like an awful waste of space."

Many people had suspected other stars would have planets but it wasn't until 1988 the first planet outside our Solar System was found. Before this we simply didn't have the technology to do this. Now the possibility of around 2400 planets outside our Solar System are being investigated. It would seem planet formation as is said to have happened with our system is much more common that we had thought. You know I like numbers so look at this...


If there were only 1 billion galaxies in our universe each with 1 billion star, then there would be...

1,000,000,000,000,000,000 stars

(one quintillion stars)

Just say of these only 0.1% (like the amount of material left when our sun formed) had planets, then there would be...

1,000,000,000,000,000 stars with planets out there.

That is one quadrillion stars with planets.

Now just say of these only 0.0001% of the planets had life (that is not 1 out of a 1,000. It is 1 out of a million), then there would be...

1,000,000,000 planets with life.

That is one billion planets with life.

But there are probably many more than a billion galaxies in our universe and I suspect life is much more common than the above but reaching planets outside our Solar System to find life doesn't seem likely because of the vast distances between the stars and far greater between galaxies.

As you know, NASA has the Curiosity rover on Mars. Latest news shows it has found rocks on Mars have some of the chemicals necessary for life - sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon. If we find evidence of life on Mars or that it once existed, we have proof we are not alone but don't expect Martian people. If life is found it will most likely only be something like bacteria.

Early Earth & Plate Tectonics

This one talks of the possibility of a number of land masses forming over time and gives them names. This is quite possible but I am happy enough with just Pangaea unless I find further evidence. The clip does show you how our Earth is protected from harmful radiation from our sun by it's magnetic field caused by our rotating liquid iron outer core. Mars's interior cooled a very long time ago. Solar radiation shed much of Mars's atmosphere but Earth has been protected. Our volcanoes, tectonic plates and earthquakes show us our world is still very active and I am thankful it is.

This embedded You Tube clip is not my video.

 New Video Clips to Watch

(added: March 24, 2013)

When checking through You Tube, I found this clip showing an animation of the Big Bang, and the beginning of our system, the Sun, Earth and Moon. This clip has nothing to read just images to watch as billions of years pass.

This embedded You Tube clip is not my video.

You know our Sun is much larger than the Earth. It's said it would take about a million Earths to make the size of the Sun but is our Sun a very big star? I found this video clip to show our Sun is so much smaller than the largest known star. This video clip shows just how tiny our Sun is compared to some other suns (stars).

This embedded You Tube clip is not my video.