Replies to This Discussion

Permalink Reply by George on July 9, 2011 at 3:05am

The Sun is not in a fixed position. Everything in the universe moves, and the Sun orbits the center of the Milky Way Galaxy approximately once every 225 million years.

The earth orbits the Sun in a roughly circular motion (the earth-sun distance varies slightly over the course of the year). The main forces at work are gravitation and inertia. The Sun's tremendous mass pulls the earth and all other planets towards it, but their motion perpendicular to that pull is fast enough that it prevents them from falling in.

It might help to explain that all objects with mass exert a gravitational pull on all other objects, but this pull is so slight that it is only noticeable to us in relation to very large objects such as moons and planets (i.e., an apple falling to earth exerts a slight upwards pull on the earth, but is so insignificant it is barely measureable).

Permalink Reply by Marc Draco on July 9, 2011 at 5:57am

That's probably a bit too much for kids, George (even though it's accurate). ;-)

 

Sol's given distance from Earth is the mean (average) but Earth's orbit is elliptical but it averages out at roughly 93 million miles or about eight light minutes.

 

Things orbit other things because they are attracted by gravity which is a very weak force - so you need a very large something before it can exert a noticeable force on something much smaller. Earth has man-made satellites and our moon, other planets may have moons and many stars are orbited by planets.

 

Our solar system orbits around (it's thought) a black hole at the centre of our galaxy... and so on. Black holes have immense gravity, you'll recall.

 

Crucially, to orbit something you have to be at a distance where you are constantly attracted to it but keep falling because you miss! Too close and you fall to the surface, too far away and you fly off into space.

Permalink Reply by Jim DePaulo on July 9, 2011 at 4:58pm

Attraction by a larger object is not really correct, but rather, the larger object warps space in such a way that smaller bodies fall toward it – however, the angular momentum of the smaller (less dense) body prevents it from falling into the larger body so it falls into a circular orbit.

Permalink Reply by George on July 9, 2011 at 11:49pm

The spacetime curvature description is not a particularly useful way of explaining gravity to most people, much less children in school.

Permalink Reply by George on July 10, 2011 at 7:15am

Do you mean by standing on the trampoline, or putting objects on it?  Sure that would illustrate space-time curvature, but it kind of begs the question because the objects are still being pulled down by gravity.  Also it's difficult to visualize the idea of 4-dimensional space.

Permalink Reply by Bwambale Robert on July 12, 2011 at 12:32am

Thanks

Permalink Reply by Ava Wilson on August 22, 2011 at 7:44pm

This isn't actually true. I found it much easier to understand gravity when it was explained to me like above, where a bowling ball was put on a stretchy surface and I could see the bend. It's also extremely EASY to explain four dimensional space to a child. In fact, understanding all of these things is MUCH easier than trying to get them to understand that 'a bigger object attracts a smaller object'. These explanations were very hollow and vague to me as a kid in science class and led to questions like 'So why don't we attract each other into orbit?', whereas with the visual of warped space time fabric, I could see that we obviously weren't big enough to make a dent in the fabric, like a bead compared to a bowling ball.

 

As far as explaining four dimensional space, the easiest way to explain it to a child is to explain it with the 'appointment' analogy. When you have a doctor's appointment, the dimensions of life are completely illustrated in the instructions.

 

The address / building is a place, which has three dimensions-- your length, width, and the height (the floor you're visiting for your appointment, for instance), and you have to be in the right mix of those three dimensions (i.e.: in the right place) in combination with the fourth dimension, time, in order to make your appointment. In this instance, time and place go directly hand in hand and illustrate how time is a cooperative dimension and not its own separate idea. Because if you're at your house during the time of your appointment, you've missed your appointment. You've also missed your appointment if you're in the right place at the wrong time. In either case, time is essential in the situation and it's something that kids, who have gone to the doctors many times by the time they're talking about space science in school, can understand easily--- especially with drawings.

Permalink Reply by George on July 9, 2011 at 8:35am

Found a useful link - NASA educational site with Lesson plans.

Using a Playground Model to Explore the Movement of the Sun, Earth,...


A great way to teach would be to set up a solar system model outdoors. Draw a large circle on the ground, and have some of the children act as the sun and the orbiting planets.

Similarly; have one child stand and hold one end of a rope, while the other child circles him or her holding the other end; the rope represents the pull of gravity.

Attachments:

• 08playground_diagram_02.gif, 6 KB

Permalink Reply by Bwambale Robert on July 12, 2011 at 12:35am

George, thanks for the NASA link, yes this i hope is going to answer my questions and will use the link for educational purposes.

Permalink Reply by Orson_Zedd on July 9, 2011 at 9:33am

Honestly, that's a really weird way to ask the question.

Permalink Reply by Loren Miller on July 9, 2011 at 9:38am

Actually, the quick and easy answer is: gravity and momentum.  For the more detailed answer, I rather like Mike K.s suggestion of Carl Sagan's series, "Cosmos" and George's diagram and links.

Permalink Reply by life3 on July 9, 2011 at 11:13am

Our solar system acts as one unit as it moves through our milky way galaxy. Earth is one of the satellites orbiting the sun, our moon is a satellite to earth. It is all about Gravity. No one mentioned this, but this might be a good place to explain how the universe is expanding and even our milky way galaxy is not fixed in the universe. In summary, the movements involve the earth moving around the sun, our solar system moving within our milky way galaxy, and our galaxy moving within a larger framework of the expanding universe. The big question would be is our universe moving within some larger context? That question would take us outside the realm of our common preception of space and time. For the record, I like snickers better than milky way.

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