List of Topics


Astronomy Feedback

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 15 letters




How does the moon rotate around the earth? Moon USA
Exactly what day a new moon falls on Moon Phases USA
Questions about multiple universes Multiple Universes The Netherlands
Why is the Earth spherical and not flat? The Earth Tanzania
Send me books on astronomy and relativity General Topics Ethiopia
What caused the initial motion in the very first atom? General USA
Why is the Moon called the Earth's only satellite? Our Moon Philippines
Please send all the astronomy information General India
Wnat websites on astronomy Resources India
Orbit page missing General USA
What heavenly bodies can I see from Ahmedabad? General India
What are the constellations seen from India? General India
I just love to learn this subject Our Solar System Zimbabwe
How can radiation escape a Black Hole? General Topics India
The Sun moves round the Earth The Earth Bangladesh

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First 15 letters


How does the moon rotate around the earth?

January 30, 2013


how does the moon rotate around the earth

- USA (23163)


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.

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Moon Phases

Exactly what day a new moon falls on

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 (22864)


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.

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Multiple Universes

Questions about 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 (22857)


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.

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The Earth

Why is the Earth spherical and not flat?

June 21, 2012


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

linus - Tanzania (22731)


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.

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General Topics

Send me books on astronomy and relativity

June 11, 2012


Can you send me some books on astronomy and relativity?

Mikon - Ethiopia (22715)


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.

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What caused the initial motion in the very first atom?

March 26, 2012


What caused the initial motion in the very first atom?

Joe - USA (22539)


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

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Our Moon

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

March 1, 2012


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

ricarose - Philippines (22467)


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

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Please send all the astronomy information

February 27, 2012


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

zubair - India (22453)


See out section on Astronomy for information.

Each lesson has listing of books.

Best wishes for success in your Astronomy studies.

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Wnat websites on astronomy

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 (22113)


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.

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Orbit page missing

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 (22101)


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.

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What heavenly bodies can I see from Ahmedabad?

October 11, 2011


I want to explore more and more
What all heavenly bodies can I see from Ahmadabad, Gujarat, in India?

Priyam - India (22059)


You should be able to see most of the galaxies and constellations in the Northern Hemisphere, as well as some of those in the Southern Hemisphere from Ahmadabad.

However, many cities have what is called "light pollution" where the city lights and humidity in the air block out the view of many stars. Observing the sky from away from the cities and even in the mountains is the best way to get a good view of all the stars.

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What are the constellations seen from India?

October 10, 2011


Which all constellations can we see from India?

Priyam - India (22054)


Some websites giving information about constellations seen from India include:
Circumpolar Constellations, India Constellations and Astronomy in Ancient India.

I hope that helps.

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Our Solar System

I just love to learn this subject

July 23, 2011


I am a homeboy but i just love to learn this subject, can you teach me?

Godfrey - Zimbabwe (21836)


I am glad you love to learn about Astronomy. Go through our free lessons to learn more about the subject. This will give you a good start.

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General Topics

How can radiation escape a Black Hole?

June 18, 2011


if black hole has a high gravity and attracts even light, then how can radiations known as black hole radiations can get out from there?

Shourya - India (21733)


Although a Black Body has such high gravity that particles or even light inside cannot escape, they still give off some radiation calling Hawking Radiation.

A Black Hole can have energy fluctuations, which cause the generation of particle-antiparticle pairs near the event horizon of the Black Hole. The event horizon is the edge where particles inside cannot escape, but particles outside the event horizon can escape.

If the particle-antiparticle pair is right at the event horizon, one of the particles falls into the Black Hole while the other escapes before they have an opportunity to annihilate each other.

It is s surprising phenomenon.

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The Earth

The Sun moves round the Earth

May 25, 2011


The Sun moves round the Earth is practical and the Earth moves round the sun is imaginative.

Because, To science day and night in crease and decrease mainly for annual motion of the world and the seasons change. on ellipse at the of rotating. The sun, The earth is changing its position always leaning against corner. The above information of the Science is not correct. Because water is always down fall. That is why, the surface of the leaning earth that is the north zone will remain canal, river and ocean less IE water less.

From 22 December to 21 June As soon as the earth leans. There would be continuous flow tide in the north zone. Again from 21 June to 22 December as soon as the earth leans, in the same way there would be Continuous ebb tide in the north zone and water will go down to the south. That is there will be flow tide and ebb tide in six months instead of six hours. On the other hand of leaning, The sun is visible in The north in summer that is 21 June and in winter it is visible in the south that 22 December.

On the other hand, the Venus, the planet mercury, the mars along with any planet or star are visible on the 21 June that is in Summer because of leaning the earth on the 22 December. That is in winter it is not visible very far to the south. All the planets and the stars in the Sky stay along side but not the Sun. Even in summer The moon is seen to the south. Because of leaning of The earth, as The sun is seen to the south in winter.

So The moon is supposed to be visible very far to the south. But The sun is seen very far to the north. That is because of leaning of The earth, all the planets, The star, The sun without The moon become visible to us in winter and summer to the north and the south is a hood with us. Actually the orbit of The sun is to the north in summer and to the south in winter, not the inclination of the earth.

To science during rotation the distance of earth from Sun does not remain same. From 4th July its distance is the15crore 20lac km and 3rd January 14crore 70 km. It distance in creases area decreases. That is why that The sun looks small in July that is The summer and it looks large in December that is in winter. Only 50lac km (15crore 20lac-14crore 70lac) near or distant for this the size of the sun from the earth look small or large yet because of annual motion, The earth stays at different distance at different time from every planet and star. But all the year round there is no change among the planets and the stars. During annual motion of the earth almost planets and the stars stay sometimes about 30crore km far again sometimes 30crore km near. As the mars stands 22.8crore km away from the sun and the earth stands 15.0crore km away from the sun.

The mars circumambulates the sun with in 687 day and the earth with in day onetime a day. So during rotation the earth stays sometimes (22.8-15.0)=7.8crore km far away from the mars again sometimes 22.8+15.0=37.8crore km. only for half a crore km the sun looks small or large but the size of the mars which is 30crore km near or far not seen small or large. Actually it the earth , on oval figure that is sometimes far or near in one word rotates/moves round the sun. So a ghostly affair will occur at night in the sky. Because whenever The earth approaches to planet or Star, that planet or star would be seen big gradually and the planet and the star from which the earth begins to move, that planet or star would be seen so much small. Since all the year round there is no change among planets and stars, every planet, Star and the Sun move round the earth.
To science `All stars are moving'.

The sun is also a Star and it is rotating in the firmament at speed 69,187 km per hour. Actually this rotation of The sun and stars is not for unknown target, rather moving having centered the earth. Some times at night in the sky the stars are seen to move from north to south again from south to north, again from west to east. They are called orbit deviated stars. Only with in 5/10 minutes these stars cross from one side to another. As these orbit deviated stars are much bigger than The sun and at a distance of crore km, It is easy for them to cross from one side to another side only with in 10 minutes. So in 24 hours the sun, the moon, the planets and the stars move round the earth and easy for them.

To science It takes 24 hours for the earth to move on its own axis. For this reason rotation of the earth is called diurnal rotation. In equator the speed of diurnal rotation of the earth is more than 1700km per hour. On the other hand it is not possible to enter in to orbit of the moon from the earth as a result moon exploration resulted in failure ten times. It needs 2.4km per second to enter in to orbit of the moon. Accident or what ever might happen if the orbit of the earth is dynamic, It would be possible to earth at any normal speed. The orbit of the moon is moving dynamic.

To science the Moon is only Satellite of the earth and the moon rotates the earth one time in days. The moon looks big because of staying near. It has no light . It gets light from the sun. If this idea of Science is correct, the blank part of the moon is expected to become visible up ward before full moon at night in east sky and after full moon at dawn in west sky but actually at that time the blank part of the moon is seen down ward. That is the moon rotates the earth one time in about 25 hours, on the contrary it is moving on its own axis one time in 29days. According to science as every planet is rotating the sun serially for because of distance so it is normal for every planet to move on its own axis serially for distance but in practical field it is not moving As the earth is moving on its axis in 23 hours 56 minutes but the planet mercury is moving on its axis in 59 day though it is very near to the sun Again though Jupiter planet stays for from the sun. It is moving on its axis one time in 9 hours 55 minutes. To science the moon rotates the earth one time in day but Science has not mentioned its opposite reaction.

Science has also mentioned that the sun rotates on its own axis one time 25 days but Science has not mentioned its own reaction. Be sides every planet is bright It the earth is planet, it is expected to be bright . But the earth is light less and dark that the earth is different from all the planets. It takes 365 days 6 hours for the earth to rotate the sun along own axis at speed of 29.76km per second or about 1lac 7thousand km per hour that is diurnal rotation of the earth and keeping the sun front, standing on its own axis in 24 hours the earth is moving west to east onetime in 24 hours that diurnal rotation is wrong. Rather the sun is moving round the Earth on time in 24 hours and its opposite reaction the sun is moving on its axis one time in the 25 days.
Yours faithfully,
Muhammad Robiul Islam Rony
Scientific Researcher

MUHAMMAD - Bangladesh (21623)


Thank you for your comments and views that the Sun orbits the Earth.

Unfortunately, you are misinformed about astronomical laws. The idea that the Sun moves around the Earth was shown to be incorrect over 500 years ago. Thousands of scientists and astronomers have verified that the Earth orbits the Sun. It has also been proven through pictures taken from space vehicles.

The Earth is tilted on its axis such that the seasons change during its orbit around the Sun. See Motion of the Earth for illustrations of the Earth's motion and the cause of the seasons.

However, it is good that you are studying about astronomy and questioning he various theories. It looks like you have done some intense evaluation. It is good to read much of the material on how things in space work to get a better viewpoint.

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