Hello Keira,

I have been looking at your comments and hope I can provide some answers to your questions. Remember, as your questions delve deeper into a subject, the answers can be more difficult to understand but this is what learning is about.  As we learn and understand simpler things, it can be easy to learn harder things. I am still learning as I search for answers. See what you can understand in the answers I try to give. What you have asked will appear in bold blue text.

Your comment from the beginning of March on the post…

Life But Not As We Know It

This NASA image was listed as in the public domain and was sourced through Wikimedia Commons.

In my personal opinion, I think that Mars was once a beautiful planet, and there was life on this beauty. Since Mars did not have a very protective ‘umbrella’, Mars’ ‘umbrella’ shrank. Overtime, Mars got closer to the sun, burned, and sent life over to Earth, right past its ‘umbrella’. As Earth evolved, Mars lost its magnificent atmosphere, and moved behind Earth. Mars soon lost everything it once had owned, life and beauty. Now taking Mars’ place is Earth. As you may know, I have a plethora of questions to ask you. Do you think my idea may be possible?

Science doesn’t tend to talk much of the impossible and prefers the word improbable. To be impossible means there is absolutely no chance of something happening no matter what might change. Improbable means it’s not very likely so if something is improbable it can happen but it is far more likely it won’t. Based on what we know at this time, your idea comes under the improbable in some parts and probable (likely) in other parts.

Look at the video clip below from NASA. It is an animator’s view of the evolution of Mars based on the information NASA has. The journey starts about 4 billion years ago and shows a water planet up till today as we know it to be. Do you think it would have been beautiful? I know it still has a beauty today but not as a water world such as ours.

“Mars was once a beautiful planet” – I think this is probable if you mean having rivers, lakes and seas but improbable if you think it had trees and large animals moving through them. Life would have been simple if it had evolved. I think there is a good chance we will eventually show life existed on Mars and may still be in the soil in some areas.

Watch the video clip below looking at NASA’s findings on Mars. It shows us Mars probably had the right conditions for life to begin. With a proposed mission in 2020, we might be able to show Mars had life.

There is evidence Mars once had liquid water on its surface but the thin atmosphere can’t keep heat in as on our planet. The average temperature of Mars is around    -60C. With water freezing at 0C, liquid water isn’t likely. However, at Mars’s equator, summer daytime temperatures can reach 20C only to drop to -70C at night. While 20C is enough for water to be liquid on Earth, I think the thin atmosphere would only allow ice to turn to water vapour and not liquid on Mars.

Yes, Mars also has seasons because it is tilted only slightly more than Earth, You might remember a post about Earth’s tilt I wrote for your class, Earth’s Tilted Seasons.

Here is another video clip looking at Earth’s magnetosphere (umbrella) and the discovery of the outer and inner core. Mars doesn’t seem to have a molten outer core and solid inner core to create the magnetic field to protect it as we have on Earth.

Mars did not have a very protective “umbrella” – Mars probably had an “umbrella” (or magnetosphere) and much thicker atmosphere in its beginning but, as the core cooled, it lost much of it starting perhaps 4 billion years ago. Without the protection of a strong magnetic field, energy from the sun made Mars lose most of its atmosphere. Remember, it’s because of Earth’s liquid and solid iron core we have the magnetosphere (umbrella) to protect us.

As Earth evolved, Mars lost its magnificent atmosphere, and moved behind Earth. -  Earth and Mars would probably have formed at around the same time. Our sun was probably formed when a molecular (atoms of matter) “cloud” collapsed through gravity. Not all of the “cloud” was used in making up the sun. The matter remaining in what is known as the accretion disk started coming together under gravity. Much of this extra matter became the planets.

Formation of the Solar System

Earth Formation

Have you ever encountered someone who has an idea of how Mars lost its beauty that you think is true?

While I have not personally met a scientist who can say what had happened, there are a number of references and videos online to help us. As with all information on the internet, it’s best to use reliable sources such as NASA when looking for information. In sharing the video links I have given you, I first check links to see if they’re from a source I trust. I also find many with sometimes strange ideas from sources I don’t know. I usually don’t use these unless I have reason to believe they are accurate.

Do you think there could have been life on other planets, too?

In the video clip below from National Geographic, it asks what aliens might really look like. No one has proof of life other than on Earth at the moment so we don’t really know what life on other planets might look like. We may only have an idea of what might be needed. The clip shows on higher gravity planets, animals would need to be stronger and stockier (bigger) than on Earth or probably spindlier (thin looking) on a planet with less gravity. Some planets might only have life like the bacteria we have here. Until we find extraterrestrial (not of Earth) life, we can only guess.

While we have no proof at this time life exists on any planet other than Earth in our Solar System, I suspect life may be in many places across the universe in some form or other. We know life on Earth can exist in a very wide range of habitats (environments where life exists). Life can be found deep under sea near volcanic vents or locked in ice on mountains.

I have seen estimates of the number of galaxies in our universe being anything from 100 billion to 500 billion. For our galaxy, the Milky Way, the number of planets might be anything from 100 to 400 billion. If we take the lower estimates for galaxies and using the low estimate for planets in our galaxy to work out how many planets there might be in the universe, we would get…

100 billion (galaxies) x 100 billion planets = 10 hextillion planets

That is…

10,000,000,000,000,000,000,000 planets in our universe

What a waste of space it would be if the only life in the universe was to be found on our small, blue planet.

Where do you get all these facts?

When I see posts or questions I find interesting, I sometimes remember information I have read or seen in the past. If I decide to write a post, I usually have to search for extra information online or in books in my library. I try not to post anything unless I believe the information I find is the best available in my research. Because of this, I sometimes have to make changes to posts if I later find I have made mistakes.

The skill is to know how to find information, work out whether it might be true then use it to help others.

Your comment from March 26 on the post…

How Did the Earth Begin?

First of all, I am wondering why early scientists thought that the sun and every other planets orbited around us?

When we look up at night, we can see the stars. Watch long enough and you notice them move. During the day, the sun rises in the east and sets in the west. Surely the sun, planets and stars must orbit the Earth because we see them move and not us. This was the thinking and it can seem reasonable. It's what we seem to see.

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

Consider this, you are on a speeding train looking out of a window. The landscape is zipping past your window very quickly. Is it the landscape moving or the train moving through it? While saying the train is moving might seem reasonable, surely this couldn't be true for the Earth? The Earth is so big compared to the small stars and planets in the sky. The Earth must be still and everything else in motion.

As early as the 3rd century BCE, a man named Aristarchus suggested the sun was the centre of the solar system but it wasn’t until the work of a man called Nicolaus Copernicus in the early 1500s a sun-centred (heliocentric model) solar system began to be accepted. It was also around this time the first telescopes seem have made an appearance. Astronomy had its start in astrology but started to emerge as science with telescopes allowing better study.

Optical Telescope dome at Warrumbungles National Park 

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

If they had had technology back then, would they still have thought that everything orbited around us?

There are still many people today who believe the Earth is at the centre of the universe (geocentric model). They believe it is fixed in place and doesn’t rotate on its axis. The more modern model has the Moon orbiting Earth. Further out the Sun orbits Earth while the other planets and their moons orbit the sun. The other stars and galaxies we see are all further out forming a sphere around central Earth. This comes down more to what I think is misguided faith (believing no matter the evidence against).

I see problems with the idea. As example, if the Earth didn’t rotate on its axis, to have day and night the sun and all of the planets orbiting it would have to orbit the Earth every 24 hours and this is not what we see. Secondly, spacecraft such as the two Voyager missions and missions to Mars were sent out based on known positions of the planets orbiting the sun. If the centre Earth model had been true, the Voyager and Mars missions would have failed.

Another question I have is about how many other galaxies are out there?

I have given information on this above. There are estimates there could be anything from 100 billion to 500 billion galaxies in the universe.

The number of people alive on Earth is heading towards 8 billion. Using the numbers above, there would anywhere from about 12.5 to 62.5 galaxies for every person on Earth. That’s a lot of galaxies.

In the image below sourced from NASA through Wikimedia Commons, there are around 5500 galaxies in view. To make the low estimate for the number of galaxies in the universe (100 billion), you would need to show approximately 18 million photos showing 5500 galaxies.

This NASA image was listed as in the public domain and was sourced through Wikimedia Commons.

One more question I have is how did those giant stars form in the last video?

Let’s show that video clip again…

I would say it’s all a matter of matter and time.

Stars spend most of their “lives” as what is known as main sequence stars where they are burning hydrogen through something called nuclear fusion. Hydrogen becomes helium. Like any fire, the fuel can run out. As this happens the star’s core gets larger and starts burning helium and fusing it into carbon and oxygen. If the star has enough mass and other features, the star is known as a supergiant star.

The supergiant stars lose mass quickly. Some of these supergiants can be quite bright and losing mass very quickly. They are the hypergiant stars like the one in the video known as VY Canus Majoris. If it was at the centre of our solar system, it would be so big it would reach out beyond Jupiter.

The very large stars have been burning their fuel making new elements. When they get to the stage of making iron then eventually trying to fuse it, the star’s core can collapse and cause what is known as a supernova (a very big explosion of light and matter). What can be left behind could be a black hole (singularity), a neutron star, quark star or a magnetar.

Back in 1987 we were able to see a supernova explosion without using a telescope. A new star seemed to appear where only powerful telescopes might once have seen it. It eventually faded but I remember seeing what looked like a new dot in the night sky. Nova SN 1987A was about 168,000 light years from Earth. What this means is the light I was watching started out from the nova about 168,000 years ago. When we look deeper into space, we are looking back in history. Even the sunlight hitting you in daylight has taken over 8 minutes to reach us.

Look at the clip below. It gives information about SN 1987A and its jouney to supernova…

In the future, VY Canus Majoris will go supernova. What can be interesting is the matter thrown off when it does may be the resources other solar systems need to form.

Also, how did humans know that there are bigger stars than the sun?

Since the beginning of humans, they have been able to see stars in the sky. As knowledge and science has advanced, we have been learning more about the universe.

Optical telescopes brought the moon, planets and stars closer. Radio telescopes picking up the “sound” of space brought us more information. The Hubble telescope orbiting earth allowed us to see even further into space than telescopes on Earth. Computers help us model systems and calculate small changes in orbits of distant stars telling us of orbiting planets. We have learnt so much since the time the first cavemen looked up and saw the stars yet we still know so little. It’s like many things in life, the more we learn the more we realize how little we know.

 Parkes Radio Telescope

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

Finally, do you think that there are larger stars than the last one in the final video in the post?

VY Canus Majoris is listed as the largest known hypergiant star. The important word is “known”. There could be far bigger stars out there somewhere. Perhaps if you become an astronomer you might discover a much larger star somewhere in the universe. What would you call it? It might still be called a hypergiant but it might have some properties making it different to hypergiants and the superhypergiants could be born. I would think such hypermassive stars would not last a long time before going supernova, or would it be hypernova? Science has many mysteries still to explain.