Category Archives: Questions and Answers

Most people have many questions about astronomy, and aren’t happy with the standard answers. Here are some articles trying to change this. If you have any questions you would like to see answered, ask me in an email to the address below, and I will answer your question in an article on this list

What is Newton’s 3rd Law of Motion?

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Newton’s 3rd Law of Motion is the most famous of the three, but also the most misunderstood:  For every action, there is an equal and opposite reaction.  To understand what it means, place your hand against a wall, and push.  You are now applying a force to the wall through your hand, but your hand does not move.  Why?  Because the wall is exerting a reactionary force against the hand, exactly equal to your force, but in the opposite direction. … Continue reading →

What is Newton’s 2nd Law of Motion?

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Newton’s 2nd Law of Motion states that if you apply a force to an object, it will accelerate at a rate proportional to its mass, and to the amount of force applied, and that the acceleration will be in the same direction as the force.  We write this mathematically as: F = MA  (Force = Mass times Acceleration).  This makes sense, because we all know that it is easier to move a light object than a heavy one.  A heavy … Continue reading →

What is Newton’s 1st law of motion?

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Newton’s first law of motion says that an object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.  What does this mean, in plain english?  Every object in the universe hates change:  If it’s stationary, it will not just start moving by itself.  If it is moving, it won’t change that movement by … Continue reading →

What is dark energy?

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Dark energy is the name used by scientists to describe whatever it is that is pushing the universe apart.  Since the 1920’s, astronomers have been able to see that the universe is expanding, and this knowledge led them to  the Big Bang Theory.  One of the Hubble Space Telescope’s most amazing discoveries was that this expansion is not slowing down (as you would expect, because of gravitational attraction), but actually speeding up.  Nothing that we know about physics can explain … Continue reading →

Satellites

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Dear Urban Astronomer How exactly do satellites work? Who invented them, and how many are up there now? I heard somewhere that there must be millions! Is this true? Yours Curious Dear Curious     All artificial satellites have one thing in common: they are in orbit around something (usually the Earth), and will in theory stay up there indefinitely all by themselves.  If by “How do they work”, you meant “How do they stay up there”, then prepare for a … Continue reading →