Home Up

 

Answers To Frequently Asked Questions At Star Parties

I am frequently asked basic questions at Star Parties.  The important thing I try to remember is that it is important to have an accurate answer, and to keep the scope of the answer simple and clear. The individual will keep asking questions if they want more information.  It's tempting sometimes to discuss things from the standpoint of an advanced amateur, but my objective at star parties is to EXCITE people about the night sky.

These answers are very approximate, and leave a lot of room for more discussion and refinement...if they want.  

 

How Far Away is the Sun? 93 million miles

How Far Away is The Moon? 250,000 miles

How Far Away is Venus? 57 million miles

How Far Away is Jupiter? 390 million miles

How Far Away is Saturn? 794 million miles

How Far Away is the nearest Star? The Sun is actually the nearest star, but Alpha Centauri is the nearest star outside of our solar system. It is 4.3 Light Years away from the Earth, or 25 trillion miles.

 

Can you see the flag on the Moon or Lunar Landers or the footprints with a telescope? No. Theyíre just too small.  We can see craters down to a couple of miles across though.

Also - Can the Hubble Space Telescope See the Flag/Lander/Footprints?  No.  Hubble was designed to view incredibly dim, far away objects.  The Lunar Surface is too bright.  There is a planned Japanese Lunar Orbiter that may be able to resolve the Lunar Lander Module in photos in two years.

 

Can you see Pluto with your telescope?  Yes.  But it looks like a really faint star and you have to have a chart and observe it over several nights just to see which little dot of light is moving against the background field of dim, faint stars.

 

How powerful is that telescope? How far away can it see? Even though itís real tempting to get into the optics formulae, typically people just want to know the distance to the farthest away object that you can see.  The Andromeda galaxy, which can be seen on a dark, clear night as a faint smudge with the naked eye, is over 3 million light years away!  With a telescope we frequently observe objects hundreds of times farther away than this.

 

What is a Black Hole? A former star that had so much mass that when its hydrogen fuel was used up, it collapsed under its own gravity until it became a single point.  A black hole's gravity is so strong, not even light can escape from itís surface.  A surprise to most people is that most galaxies have a massive Black Hole at their center.

 

When all the planets line up, does it cause earthquakes? (A personal favorite)  No.  The gravitational force is inversely proportional to the square of the distance between the masses.  The largest planet, Jupiter, is 390 million miles away and Saturn is almost twice as far as that.  Even if all of the planets were aligned perfectly on the same side of the sun, there would be no detectable changes here on Earth.  You will experience more gravitational pull from your dog walking by than the combined tug of all of the planets aligning.  The Moon only affects the Earth because it is relatively close at 250 thousand miles, and is comparatively large for a moon.

 

Have you ever seen any aliens?  You're on your own with this one!  Because I have a warped sense of humor, I have been at star parties where I knew beforehand that two bright Iridium Flares were going to happen within a couple of minutes of each other in the same section of sky.  With a bit of theatrics, an electronic camera flash and a story about being able to contact the aliens, it can be pretty funny.  Yeah, I know - strange sense of humor.

 

If all of the planets line up, will it cause earthquakes, floods, and generally the end of the world?  You don't have to worry. There was a major planetary alignment in the mid 1980's and again in 2000.  These have happened many, many times since the beginning of our solar system.

As expected there was no disaster on May 5th, 2000, due to the planetary alignment.  No polar ice shift, cataclysmic earthquakes, or giant tidal waves.  The planets were not pulled into the Sun.  There will be other alignments and unusual planetary configurations from time to time in the future, and no doubt some people will claim dire consequences based on prophesy or strange theories.

The Solar System has been doing its thing for millions of years based on the rules of gravitation and orbital science.  Physical effects are caused by physical forces, and when a prediction is made based on someone's prophesy but science doesn't back it up, you can bet the prediction will fail.  In this particular case, any good high school physics student could have figured out that the forces exerted on the Earth during this alignment would be nothing out of the ordinary and, in fact, be less than occur quite commonly.

I once calculated that if ALL of the planets were aligned on one side of the Sun (the absolute maximum gravitational force possible due to planetary alignment), I would experience more gravitational effect on myself from a passing Golden Retriever than I would from the planetary alignment.  (OK... I was a Physics Major and bored!)

While the masses of the planets are huge in comparison to my calculation of the dog and myself, the distances are even greater.  Distance is what reduces the gravitational force very quickly.  I can't tell how old you are from your brief e-mail, but there is a formula that you can use to calculate the gravitational force between any two objects.

F= G x (m x M) / r2

Where F is the force between the objects, G is called the gravitational constant and doesn't change, m is the mass of the first body, M is the mass of the second body, and r2 is the distance between the bodies squared.

Imagine that the masses of two objects are doubled.  From the equation, the gravitational force would double.  Now imagine that the distance (r) between them is doubled.  You can see that the gravitational force is * reduced * by 4!  Distance is really the major player here.

Remember one other thing about a planetary alignment that most people forget - the planets on orbits outside the orbit of the Earth: Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto, would all be pulling the Earth slightly AWAY from the Sun with their gravitational forces.  Only tiny Mercury and Venus's infinitesimal gravitational forces would add to the Sun's existing force.

 

 

You must have others.  Please send them to me and I'll post them on this page! 

 

Introduction to the Night Sky - Part IV

Return to Part IV Outline << Previous Subject Next Subject >>

 

11/2011

05/26/2017