List of Topics

SfC Home > Physical Science > Astronomy >


Feedback Q&A on Astronomy

by Ron Kurtus

Readers have sent in a total of 303 comments and questions on Astronomy issues. They are listed according to date.

You can read them to further your understanding of the subject.

List of next 10 letters




Moon How does the moon rotate around the earth? USA
Moon Phases Exactly what day a new moon falls on USA
Multiple Universes Questions about multiple universes The Netherlands
The Earth Why is the Earth spherical and not flat? Tanzania
General Topics Send me books on astronomy and relativity Ethiopia
General What caused the initial motion in the very first atom? USA
Our Moon Why is the Moon called the Earth's only satellite? Philippines
General Please send all the astronomy information India
Resources Wnat websites on astronomy India
General Orbit page missing USA

Next 10


First 10 letters

How does the moon rotate around the earth?

Topic: Moon


January 30, 2013

how does the moon rotate around the earth




Both the Moon and the Earth are in motion in space. The gravitational force between the Moon and The Earth causes the Moon to go in orbit around the Earth. Gravitation causes the centripetal force to keep it in orbit.

Likewise, the force between the Earth and the Sun keeps the Earth in orbit around the Sun.

Back to top

Exactly what day a new moon falls on

Topic: Moon Phases


August 28, 2012

I'm struggling with knowing exactly what day a new moon falls on. I know what usno navy says but my rabbi keep telling me something the next new moon on September 16 or another time?

chris - USA



According to the USNO Phases of the Moon, the next new moon would be on September 16.

Although your rabbi may know about astronomy, I would trust the USNO, since that is their business.

Back to top

Questions about multiple universes

Topic: Multiple Universes


August 23, 2012

Dear Champion,

I've read the page of 'Theory of Multiple Universes' with much interest. Some questions arose while going through it. I would be very grateful if you could share some light on some:

1) If our universe was made up in a multiverse, then can't the same questions regarding the start of universe, still be asked about the multiverse? So shouldn't we still ask ourselves how then the multiverse started? Doesn't this make the multiverse the same thing as the universe? (I am also asking the last question because you write that universes might affect force fields of other universes and that there are possible distances between them – as far as I understand these conditions can only be met in one universe)

2) How can there be a distance between universes if distance (space) is only existing within a universe?

3) It is written that the universe is 13,5 billion years old and that it is 156 billion light years wide. Then this would mean that the universe is expanding faster than the speed of light... I wonder if you can deduct this from those two premises, because it could also be that in the early days of the universe it was expanding very rapidly compared to nowadays and then now it does not have to be expanding faster than the speed of light. Am I right with saying that above deduction does not hold or am I missing something? (I know that nowadays the expansion of the universe is said to accelerate, which means that indeed that happens with a greater speed than light, and I know that a universe expanding is something else than matter travelling over space).

4) The answer given to ‘What is beyond the existing outer edge of the Universe?’ is according to the text ‘Many astronomers believe it is just empty space or nothing at all.’ I highly doubt that. From what I have read astronomers usually see the universe as all that exists and if you’d be at the ‘edge’ of the universe it should be really all there is. If there would be empty space behind it, then that is part of the universe as well. Most think in higher dimensions than the famous 3D. The universe could very well be curved in a non-3D way that would make the edge be a sort of loop to the universe itself. I can’t really explain it well, but maybe see it as Escher’s waterfall. His waterfall does not end at the edge because it simply loops into itself. So I tried to say that the universe according to astronomers is limited, but has no boundaries. There is no edge. So my question regarding this is if most astronomers really believe in a void beyond the edge of the universe, or if they believe that the universe has no edge?

5) I don’t think I get the Multiverse theorem. If universes overlap due to expansion, what does this mean? They become one? In what way do they overlap? In distance? Doesn’t that make the Multiverse one universe then?

6) How do you define distance if distance exists between universes in which all existing is included? It seems contradictive. Maybe I am making assumptions there are not in place? I just don’t understand how one can speak of distance between universes if distance seems to be one of those things that is existing or maybe needs something to exist because a distance is always between. If two universes exist and hence one can speak of distance between them, then what’s the difference between a universe and a multiverse? Is this a definition problem?

7) If only this universe can be measured (or we can have information about it, so to say), then how do you test/prove that other universes might be there? (if it is to explain things like the accelerated expansion of the universe, then how does this theory sound any better than the old idea of a God that created the universe and made it that way that it expands faster and faster?)

Thank you for showing interest in my pondering,

kind regards,

Kim - The Netherlands



With the concept of a multiverse or multiple universes, the various universes will start with a "big bang" of their own, just as our Universe started. However, the forces created from such "explosions" could influence or affect neighboring universes.

Light from nearby universes would probably be too faint to detect. Also, there is the consideration that the various universe have different forms of matter and energy.

Space and time are interesting concepts and probably are not confined to our Universe but extent throughout the Multiverse. Likewise with distance or separation between objects.

There are several versions of estimations of the width of the Universe. Some imply that expansion is faster than the speed of light. The best explanation I've seen is that dim galaxies at the edge of the observable Universe seem to be 13.5 billion years old. Light traveling from them would then take 13.5B years to reach us, and thus the radius of the observable Universe is 13.8 billion light-years.

I would define the edge of the Universe as the edge of matter from the Big Bang. Beyond that would be just space or perhaps other universes.

The distance between galaxies in our Universe is usually measured in terms of the length of time it takes light to travel the separation.

A good question is if other universes have the same physical laws. Perhaps there are different forms of energy.

The big thing is that the concept of multiple universes or multiverses is highly speculative. Although based on measurements, even the size and age of our Universe is guesswork.

Back to top

Why is the Earth spherical and not flat?

Topic: The Earth


June 21, 2012

why earth is said to be in spherical shape and not flat?. Why other planets do not support life?

linus - Tanzania



When the Earth and other planets were formed, they were hot liquids. The internal forces cause liquids to take the shape of a sphere, like like with a raindrop.

When the Earth cooled and solidified, it remained in a spherical shape. Note that a flat shape would be unstable and inefficient.

Life as we know it requires an atmosphere of Oxygen and mild temperatures. Some plants are too hot and others are too cold. However, they may have forms of life that we do not yet recognize.

Back to top

Send me books on astronomy and relativity

Topic: General Topics


June 11, 2012

Can you send me some books on astronomy and relativity?

Mikon - Ethiopia



I'm sorry but we cannot send you any books. However, you have use our lessons to get some of the information you need.

I am adding to the material all the time and will soon have e0books on the subject.

Back to top

What caused the initial motion in the very first atom?

Topic: General


March 26, 2012

What caused the initial motion in the very first atom?

Joe - USA



The Big Bang Theory says that all atomic particles were highly compressed together and then exploded outward about 13 billion years ago. Particles clumped together after the explosion to form atoms and then later stars and galaxies.

See Big Bang Theory

Back to top

Why is the Moon called the Earth's only satellite?

Topic: Our Moon


March 1, 2012

Why the moon its also called the earth's only satellite?

ricarose - Philippines



The Moon is the Earth's only natural satellite. However, countries have put numerous artificial satellites up into orbit around the Earth.

Back to top

Please send all the astronomy information

Topic: General


February 27, 2012

please send all the astronomy information to me .and related best books.

zubair - India



See out section on Astronomy for information.

Each lesson has listing of books.

Best wishes for success in your Astronomy studies.

Back to top

Wnat websites on astronomy

Topic: Resources


October 25, 2011

I love learning from your site.
Can you give me some other FREE websites from where I can gain knowledge about astronomy?
And PLEASE, don't think that your website is not enough for me.
I just love your website!

Priyam - India



Sky and Telescope Magazine has a good list of astronomy websites.

NASA Science has much about space science.

Astronomy Magazine has some interesting articles about the latest in the subject.

Back to top

Orbit page missing

Topic: General


October 19, 2011

A course website I help maintain was linking to a page on your website but the link now returns a page not found message. The page was at your school for champions domain followed by the path:


Has the material moved? In particular our website referred to a demonstration of a satellite revolving around the Earth. If you would let me know where that moved I would appreciate it.

Linda - USA



If I remember, that was a simulation of a satellite in orbit as a Java app. The page was from about 2005. But unfortunately, the application was not working as it should, so I removed it.

Usually, I provide a link to a page that has been moved and keep that link available for a few years.

If such an animation of an object in orbit is of interest to you and your students, I might be able to add something like that to the site. Let me know.

Sorry about the inconvenience.

Back to top

Next 10


Hopefully, this reader feedback has helped provide information about Astronomy issues.

Ask, seek, know

Resources and references

Ron Kurtus' Credentials


Astronomy Resources


Top-rated books on Astronomy

Questions and comments

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.

Feel free to establish a link from your website to pages in this site.

Where are you now?

School for Champions

Astronomy topics

Feedback Q&A om Astronomy

Astronomy topics

Solar system




Graded test

Also see

Let's make the world a better place

Be the best that you can be.

Use your knowledge and skills to help others succeed.

Don't be wasteful; protect our environment.

You CAN influence the world.

Live Your Life as a Champion:

Take care of your health

Seek knowledge and gain skills

Do excellent work

Be valuable to others

Have utmost character

Be a Champion!

The School for Champions helps you become the type of person who can be called a Champion.