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.
|Does the Earth have a uniform velocity?||The Earth||India|
|Does the Earth wobble?||Orbit Demo||USA|
|Kepler's concepts on polygons and orbits||Orbit Demo||USA|
|Why are the planets in motion?||Observations||Turkey|
|Giving report on elliptical orbits||Orbital Motion||Turkey|
|Is the Earth moving closer to the Sun?||The Earth||USA|
|What is a Black Hole made of?||Black Holes||Australia|
|How are satellite part protected from a solar flare?||Our Sun||India|
|Astronomical observations from moon surface||Our Moon||India|
|Why are orbits ellipses?||Our Solar System||Pakistan|
|Electrons do not rotate in elliptical orbits||Orbital Motion||USA|
|Why will the satellite hit the earth?||Orbit Demo||Asia|
|Difference between Waxing and Waning of the Moon||Our Moon||India|
|What is the path of a geostationary satellite?||Orbit Demo||India|
|Phase of moon on Easter April 8, 2007||Our Moon||USA|
Does the Earth have a uniform velocity?
October 16, 2007
Can we say that earth is moving with uniform velocity as it always have the same average velocity
usha - India (14551)
Since the Earth is traveling in a slight ellipse around the Sun, it actually speeds up when it is closest to the Sun. But most do not consider that and say the Earth has a uniform velocity. Average velocity is more correct.
Does the Earth wobble?
September 7, 2007
Mr. Kurtus; On the subject of the moon's orbit. My source is the web site " How things work ." It was stated that the moon and earth orbit each other around a common center of mass. That we cannot assume that the moon orbits a planet that is stationary with respect to it. But since the earth is 81 times more massive than the moon, that center of mass resides inside the earth and the earth's orbit is something like a wobble. ??? I had never heard this before. Your opinion? Thanks.
Aldo - USA (14359)
The view from Earth is that the Moon is rotating around the Earth. But from outer space, it is seen that the are both rotating around the center of mass of the two. This center is called the barycenter. Because of the great difference in size, the barycenter is located inside the Earth. Thus from space, it would look like the Earth was wobbling.
Binary stars are an example of objects that are almost the same size that are rotating around each other. In such a case, the center of mass is usually located halfway between the two, so it is obvious that they are rotating around a center.
Note that much has to do with your point-of-view. the Earth may appear to wobble to someone in space, but it does not appear to wobble to someone on Earth or on the Moon.
Kepler's concepts on polygons and orbits
August 28, 2007
I really think your site is wonderful.
You've taken ideas which can be very complex and made them easy to understand. Thank you. I appreciate that you've made it a little easier.
I'm wondering though if you have any comments on something Kepler was doing with perfect geometrical solid figures. He felt were they were the keys to explaining the planets orbits.
According to my textbook, it says that,"Kepler suggested that spaces in the shapes of each of these regular solids came between each pair of the spheres that carried Copernicus's six planets."
The shapes were: the tetrahedron (pyramid), the cube, the octahedron (8 faces), the dodecahedron (12 faces) and the icosahedron (20 faces). I'm having difficulty making sense of that.
Thanks for all of the help.
Julie - USA (14277)
I'm glad you found the site useful to you.
Kepler was a mathematician who was looking for a geometric basis of the Universe. He found that 3-dimensional polygons or polyhedra could be placed inside and outside spheres that had radii proportional to the orbits of the planets around the Sun. He thought he had found Gods geometrical plan for the universe.
He later went on to determine the laws of planetary motion that Newton used to explain gravity.
Kepler's ideas on the polygons are considered interesting, but not all that relevant to explaining orbital motion.
Why are the planets in motion?
August 14, 2007
hi my name is abdullah I asked a question about elliptical orbits last week now I have a question too.why are the planets stir?which power to set planet into action?
abdullah - Turkey (14198)
If you look at hot water before it boils, you will see parts of the water spinning in circles. The same thing happened when the Universe was being formed. Everything was a gas or liquid in spinning eddies, but they soon collected into solids like the various stars and planets. But they still have that circular motion.
Giving report on elliptical orbits
August 6, 2007
hello my name is abdullah
I am reading Feynman's lost lecture.in this book there are a lots of imformation about why elliptical orbits .so this year I will give a conference in my school. I will prove that why elliptical orbits . but I do not have enoug information about elliptical orbits . so can you help me about this topic. I will wait your answer. please give me more information about this topic
abdullah - Turkey (14166)
When you spin a weight on a string around you, it travels in a circular orbit. The string exerts a constant force on the weight to keep it from moving in a straight line. But in the case of a particle or object moving along in a straight line and then attracted to another object that has an force of attraction toward it, the orbit will be an ellipse, because of the component in the original line of motion.
The slower the initial velocity of the object (or the stronger the force of attraction) the more the ellipse will become circular. It can never be a true circle, because there must always be a component of velocity. If the velocity is zero, the object would simply fall toward the center.
Note that if the initial velocity is too great, the object will not travel in an elliptical orbit. Instead, it will move in a parabolic path.
You can get more information from:
Best wishes in you project.
Is the Earth moving closer to the Sun?
August 5, 2007
Is it true that the Earth is moving closer to the sun each year? and if it is true does that mean in so many years we will all die of heat waves.
- USA (14162)
Yes, the Earth is slowing down and thus is getting closer to the Sun. But it is less than a mile a year. Since the Earth is 92,000,000 miles from the Sun, people on Earth will not be affected by it for about a million years from now.
What is a Black Hole made of?
August 5, 2007
what is the black hole made of?
stephanie - Australia (14163)
Black Holes are suns or stars that have collapsed on themselves. Their force of gravity is so great that their light cannot escape.
How are satellite part protected from a solar flare?
July 31, 2007
I have planned to do a paper presentation on PROTECTION OF COMMUNICATION SYSTEMS FROM SOLAR FLARES. I need help from you. All i need to know is, whether the parts inside the satellites can be protected using nano compunds, etc.? Or if you have any idea, please let me know.
Karthik - India (14139)
Solar flares are storms on the surface of the Sun that send out high energy x-rays, electrons and other particles. Methods to protect against damage include extra shielding, turning off equipment to avoid the radiation from causing excessive internal currents, and rotating the satellite to face sensitive equipment away from the Sun.
Astronomical observations from moon surface
July 10, 2007
I am writing an essay on astronomical observations from moon surface vis. a vis. low earth orbiting observatory.Could you please give some points which ought to be included in such an essay.
- India (14049)
Some points in your essay could be:
1. What are the advantages and disadvantaged of such observations?
2. What problems are there in getting telescopes and other equipment to the moon?
3. How do extreme condition affect observation equipment?
4. Do humans need to be on the moon, or can it be done with machines and robots sending the information via radio waves?
I hope that helps. Best wishes in your essay.
Why are orbits ellipses?
June 2, 2007
why the orbit of electrons around the nucleus is elliptical in shape? and does plasma exist on the earth its composition structure and complete explanation?is there there any technique or relation by which energy can be converted into mass..........i have read by equation....e=mc2 that energy and mass are inter convertable
Abeera - Pakistan (13870)
Planets in the solar system and electrons in orbit travel in elliptical orbits because of the forces of other objects acting on them. If there were no other planets around, the Earth would travel in a circular orbit. Likewise for electrons.
Note that new theories say that electrons are in sort of a cloud around the nucleus.
Since "c" is the speed of light, the Einstein's equation shows that mass can be converted to radiant energy. When the atom splits, some of its mass is sent off as high energy particles and gamma rays.
Electrons do not rotate in elliptical orbits
May 18, 2007
Under "Orbital Motion and Kepler's Laws" the article says that electrons travel around the nucleus in an elliptical orbit. This is not true. The electrons around an atom travel in random paths that cannot be measured accurately because of the Heisenberg Uncertainty Principle, but can be approximated. In fact, electrons have both wave-like and particle-like properties, so it is even more difficult to describe their motion.
Sam - USA (13814)
Thanks for your feedback.
In the very simple Bohr model of the atom, many phenomena can be explained with electrons in orbit around the nucleus. But the more modern and complex models of the atom include quantum mechanics effects such as the Heisenberg uncertainty principle.
One model is that the electrons are in some sort of cloud, where their position could not be predicted according to the Heisenberg principle. Another theory is that the electrons are really vibrating strings. These theories fill in the gaps that the old Bohr model cannot explain.
We do mention those theories elsewhere, but perhaps this material should be clarified to state that the elliptical orbits of the electrons only hold for the Bohr model of an atom.
Why will the satellite hit the earth?
April 4, 2007
why will the satillite hit the earth?
janequa - Asia (13486)
It the orbit gets too oblong or if the satellite slows down, it will hit the Earth.
Difference between Waxing and Waning of the Moon
March 21, 2007
What is the difference between Waxing & Waning of the Moon as ooposed to eclipse of the moon? Is there a relation between these two?
Gaurav - India (13404)
Waxing comes after a new Moon and waning comes after the full Moon, as shown in the illustration. They relate to the angle of the Sun on the Moon.
An eclipse of the Moon is when the Earth's shadow covers the Moon. That does not happen often.
What is the path of a geostationary satellite?
March 20, 2007
since earth is also revolving around the sun -what is the actual path of the geostationary satellite around the earth?
Hareesh - India (13399)
The path has to be relative or respect to something.
The satellite is stationary with respect to the Earth. But it travels in a looping path similar to the Moon with respect to the Sun. Also note that the Sun rotates in an orbit within the Galaxy.
Phase of moon on Easter April 8, 2007
March 19, 2007
What phase will the moon be in on Easter April 8,2007?
kendra - USA (13398)
It will be a Waning Gibbous, which is between a Full Moon and the Last Quarter.
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