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




Weak force asymmetry and orbit of Moon Moon USA
Observations and comments about black holes Black Holes Canada
Would someone ten light years away see a light? General Topics USA
What are the navigational stars? Constellations USA
How can the Unverse be 156 billion light years big? Our Universe USA
What if something fell into a Black Hole? Black Holes USA
Other theories besides the Big Bang theory should be mentioned Our Universe USA
How long for a space ship to travel one light year? Astronomical Distances USA
When will the Halley's Comet appear next? Observations India
Not sure what an ellipse is Orbital Motion England
How else does the Moon affect the Earth? Our Moon USA
How long will the Earth keep spinning in the axis? Our Solar System South Africa
Confused about the equation x = v^2 / 2g Black Holes USA
Is it possible for the Earth to be in a perfect circular orbit? Keplers Laws UK
Why does Jupiter have different colour gases? Our Solar System Jamaica

Next 15 letters


First 15 letters


Weak force asymmetry and orbit of Moon

November 16, 2009


How come F=m+{a}a where the value of the weak force asymmetry is added to mass gives the correct obit of the moon?

John F. Hendry/E W Higgs^^

John - USA (18671)


The weak force primarily applies to nuclear interactions and beta decay. The weak force asymmetry seems to show a difference between left- and right-hand interactions. As far as I know, any effects of the weak force is already included in determination of the mass of particles.

Also, nuclear effects don't really influence macro events like the orbit of the Moon or planets. Differences in gravitation from the Earth due to mountains and such have a greater influence on the Moon's path.

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Black Holes

Observations and comments about black holes

November 10, 2009


Now, I am no university professor but in the section about black holes it says that they "gain energy" but i have also heard there is gamma radiation emitted from black holes when it devours matter (named Hawking radiation)this emitted gamma is greater or less than the devoured energy (or relative energy) depending on the mass of said black hole. So, in theory black holes have the ability to either continuously gain in mass or slowly evaporate to a lesser mass until the gravity is at a state in which is does not have a escape velocity = to c (speed of light) so i don't know the calculations but this process would probably take a massive time period, but once a black hole has "evaporated" you would be able to see it and it would no longer be "black" this would probably be classified as a neutron star.

This text - property of Michael Diaz, Grade 9 Student

Michael - Canada (18646)


Thanks for your observations and comments.

The original, simple theories about black holes said they had such high gravity that not even light could escape. If that was the case, then they would be continually absorbing incoming radiation and thus gaining energy. I didn't get into this in my lesson, but perhaps I should.

But continually gaining energy--even a small amount--can bring up a number of problems, as you point out. The way the Hawking radiation works in theory is that quantum tunneling effects occur near the event horizon of the black hole. These effects bypass the gravitational requirements. This also reduces the mass of the black hole, ultimately causing the black hole to change its form.

What is amazing is that Hawkins made many of his discoveries through "mind experiments". Of course, he isn't the only scientist who contributed to theories about black holes.

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General Topics

Would someone ten light years away see a light?

July 28, 2009


If i were to turn on a light on earth and turn it back off in theory that light goes of forever correct ? Because say someone ten light years away wont see it for ten light years and so on far any distance,so once lit it shines forever. Does this make since ?

Robert - USA (18076)


A problem with most lights is that the wave spreads out as it travels away from its source. There is a distance where the energy is too small to see. Stars that are many light years away are so huge and bright that we can still see them. Astronomers estimate their distance by how much the light has dimmed.

A laser beam of light does not spread out, so that would be better to shine. Someone ten light years away could not see that beam until ten years from now.

So, when we look at distant stars, they probably aren't in the same position right now. In fact, some distant stars that we see right now may have even exploded and disappeared for all we know.

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What are the navigational stars?

July 11, 2009


What are the navigational stars for the Northern and Southern Hemispheres?

Laura - USA (18016)


In the Northern Hemisphere, the North Star (Polaris) is used for navigation, since it is close to due north.

In the Southern Hemisphere, the Southern Cross is used. It consists of several stars that stay close to due south.

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Our Universe

How can the Unverse be 156 billion light years big?

May 30, 2009


I have just read that our universe is estimated to be 156 billion light years across. If the big bang occured 13.7 billion years ago and nothing can travel faster than the speed of light, how do objects get to be that far apart? I'm confused. Can you please explain in lay terms how these distances and times are computed? Thank You, Bill Ridgeway

Bill - USA (17826)


This definition of the extent of the Universe is how far light has traveled and not where any stars have yet reached.

The logic used in the estimated diameter of 156 light years is that as light traveled from the source of the Big Bang, space itself has been expanding. So, light is going at the same speed with respect to space, but space is moving too. It is like shooting a bullet on a moving train: the bullet moves at one velocity with respect to the train, but actually faster with respect to an outside observer. Part of this argument comes from measurement of cosmic microwave background radiation, which is supposed to be from the Big Bang itself.

I don't like the logic or argument they use. It is a pretty wild guess. In fact, even the date of the Big Bang is questionable. It is also based on this background radiation and the amount of time it takes to cool to its present state.

To see how astronomers estimate distances of objects they can see, check:

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Black Holes

What if something fell into a Black Hole?

May 14, 2009


what would happen if something fell into a black hole? would it come out on the other side? or would it disappear for forever?

Julie - USA (17739)


A Black Hole is a star, sun or even planet that has so much gravity that even light cannot escape it. Thus if some object got too close, it would be sucked in by the gravity and probably be crushed into a small clump. Nothing escapes a Black Hole, except for a stream of gas at its top or bottom due to its spin.

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Our Universe

Other theories besides the Big Bang theory should be mentioned

May 7, 2009


I was just writing to say that I think it isn't very fair that on this website the only theory presented is the 'big bang' theory. Honestly that theory is one of the most ridiculous theories I have ever been presented in my life. I think if at least a couple more theories were included in this lesson then some readers would feel a little more included, especially those who believe that God created the universe. I hope that this is a possiblity, especially because no one can prove exactly what created the universe, so it shouldn't be summed down to just one theory. Thanks for your time!

Julie - USA (17713)


There are several other theories of how the universe began, but most scientists feel that the Big Bang theory is the best explanation. Note that many religions that believe that God created the universe also accept the Big Bang theory as a good explanation. See:

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Astronomical Distances

How long for a space ship to travel one light year?

April 17, 2009


How long does it take a man made object to travel one light year?

Hugh - USA (17622)


Although we've accelerated atomic particles to close to the speed of light, man-made objects have been only able to reach a small fraction of that speed.

Some space probes have reached the speed of 150,000 mph or 250,000 km/hr. That is about 1/4000 of the speed of light. Thus, such a space probe would take 4000 years to travel one light year.

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When will the Halley's Comet appear next?

March 9, 2009


when will the Halley's Comet appear next?

- India (17416)


Halley's Comet was last near the Earth in February 1986. The next appearance will be in July 2061.

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Orbital Motion

Not sure what an ellipse is

March 4, 2009


Hi- some of your information is really useful in my space project but i'm still not quite sure what an elliptical orbit is and why it occurs!
Can you help me please?????????????????

Julia - England (17378)


A perfect orbit is a circle. An ellipse is like a circle that is slightly flattened. It happens if the planet is not completely round, so that the gravity varies, or the effect from the gravity of other planets.

Best wishes in your space project.

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Our Moon

How else does the Moon affect the Earth?

December 10, 2008


other than the moon affecting the earths tides, are there any other effects the moon has on the earth?

natascha - USA (16930)


Besides affecting the tides, the gravity of the Moon also affects the thickness of the atmosphere in the same way as the tides. It can also cause a very small shifting of the ground.

The light from the Moon is useful for animals and humans at night. It may have some affect on plants.

The motion of the Moon around the Earth also causes a slight wobble in the Earth's orbit.

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Our Solar System

How long will the Earth keep spinning in the axis?

December 7, 2008


how long will the Earth keep spinning in the axis?

Thando - South Africa (16916)


Although the friction from the oceans is slowing down the spin of the Earth a very small amount, it is expected that the Earth will continue to spin for millions of years.

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Black Holes

Confused about the equation x = v^2 / 2g

December 4, 2008


I am confused about the equation x = v^2 / 2g
You said v was the velocity, but what velocity is that exactly? Average, initial, final? Also, you said the gravitational acceleration is 9.8m/s^2, but if the ball is going up, wouldn't the acceleration be negative?

Just a couple questions to clear up my understanding of the equation. :) Any help would be appreciated. Thanks!

Kristin - USA (16904)


See the lesson "Gravity Equations for Upward Motion" at:

v is the initial velocity that the object is propelled upward. x is the maximum height the object will reach, if it starts at velocity v. The equation is the opposite of the distance a falling object goes to reach v. Thus, the negative signs cancel out.

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Keplers Laws

Is it possible for the Earth to be in a perfect circular orbit?

December 3, 2008


i was told by a friend that it is imposible for the earth to revolve around the sun in a perfect circle , is this true? If it is why can't it?

nicole - UK (16898)


The orbit of the Earth around the Sun is almost a circle. The gravitational attraction from other planets pulls the Earth out of a circular orbit into a varying elliptical orbit.

If there were no other planets in the solar system and we did not have the Moon, it would be possible for the Earth to be in a perfect circular orbit.

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Our Solar System

Why does Jupiter have different colour gases?

December 1, 2008


Why is it that Jupiter has the different colour gases going around over and over again?

Racine - Jamaica (16878)


Jupiter is covered by a heavy layer of hydrogen and helium gas, with an upper atmosphere of ammonia crystals. Because of the composition of the gases and the temperature on Jupiter, those gases appear in colors and in streaks of colors.

The movement of the gases is very similar to the movement of high and low pressure weather systems on Earth. The only thing is that they are I'm a much larger scale, since Jupiter is such a large planet.

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