Here’s a thread for those 4th grade science questions that you still don’t get. Post with immunity, you will not be laughed at.
I hope.
Because here’s mine.
I still don’t understand how the moon works. When I see a crescent moon, I understand (I think) that the lit part is a reflection of the sun…right? But the dark part is…what? and if we have a crescent moon in Chicago, is there also a crescent moon in Australia? Or is it different from different places on the globe?
jar the theatre major
The dark bit of the moon is the shadow of the earth ,since the moon has an orbit of the earth of 28 days it passes into the earths shadow and sometimes passes in the way of the sun making an eclipse.
Ehm, geepee, that turns out not to be the case. The dark bit of the moon is the part of the moon that’s visible from earth, but doesn’t get struck by sunlight.
The Earth does indeed throw a shoadow at the moon, and that’s a lunar eclipse.
S. Norman - waiting for the Bad Astronomer to come and tell me I got it all wrong.
Think of it as the sun, earth and moon being in near allignment. Kinda like the earth as the sun’s shadow puppet.
geepee, passing off false information in GQ is very much frowned upon.
jarbabyj, at any given time, one half of the moon is illuminated by the sun, just as half of the earth is illuminated by the sun. The dark part of the moon is that portion that we see that is not illuminated.
Here’s a quick experiment that really easy (and involves candles, which you’ll love). Light a candle near the wall in a completely dark room. Have your husband hold up a baseball in the middle of the room. Slowly walk around the baseball. You’ll notice right away that depending on the position of you, the baseball, and the candle, you will see different ‘phases’ in the baseball. If it’s difficult to tell, put the candle closer.
thanks Munch! I’ll try it.
and thanks for not laughing at me.
If you are on a motorcycle going down the highway, and you press on the inside of the left handle grip, why do the wheels turn to the right, but you turn to the left?
:rolleyes:
jarbaby, just do the experiment Munch has suggested. You’ll immediately understand.
Actually, I have a better way of doing it. Instead of you walking around the baseball., have your husband hold the baseball and walk around YOU, simulating the moon orbiting the earth. (Have him hold it a little over your head, though, so you don’t block it. The Earth rarely blocks the moon - lunar eclipses aren’t common. Watch it as it goes around you. It’ll go through phases, just like the moon does.
No, that’s incorrect as well. The dark part is NOT the earth’s shadow, except for very rare occassions of an eclipse.
lieu, in my above experiment, do the following:
In the dark room, face the light source. Hold the baseball at arm’s length at a right angle (90 degrees) perpendicular to the light source (if you’re facing north, hold the ball either west or east). Look at the ball. You will see a ‘half-moon’. Why? Because you can only see 1/2 of the illuminated part of the baseball. Now, notice where your shadow is - it’s directly behind you, to the south. There’s no way that your shadow can play any part in being the dark part of that baseball.
Hope this helps.
The first part was brilliantly answered by Spiny and Munch, so I’ll tackle this:
While the moon will turn the same side towards the viewer on any point on the earth (assuming that it’s over the horizon), it will still look different! That’s because you (the viewer) will be ‘tilted’. The crescent shape we northern-hemispherians associate with a new moon will look like a symmetric bowl at the equator. In Australia it will have the shape that you in Chicago would associate with a waning moon!
To illustrate that you will have to continue the RickJay-Munch experiment, and try leaning at different angles. (Hanging upside-down to simulate being in Sydney.:))
Yup. I just thought of that. It does make it much easier.
For the record, with your husband walking around you, the candle is the sun, you are the earth, and the ball is the moon.
Hope this helps!
The wheels don’t turn to the right-- you’re leaning to the left.
At least, that’s what I do when I’m going more than 30 kilometres an hour… Johnny LA will probably come along and say that it’s called counter-steering, but I think that’s a 10 cent word meaning “to lean.”
Maybe I’m missing something, but if I push the inside left on my handle bar, one of the following occurs:[ul][]The wheel turns to the right. I automatically lean right as well, so as to facilitate a right hand turn.[]The wheel turns right. I fail to lean to the right, and crash on my left side.[/ul]What kind of bike do you ride? 
Ah, I see, I see. You push the left end of the bar DOWNWARDS. I assumed forwards.
Here’s a nifty moon phase animation that might help you out.
Notice that for the purposes of the animation you are always standing at the 3 o’clock position. Granted the earth rotates but since the moon orbits slower than the earth rotates you can always consider yourself at the 3 o’clock position. The moon takes roughly a week to move to each cardinal point (12, 9, 6 and 3).
So, while at the 3 o’clock position you are looking at the side of the moon when it is at 6 o’clock and 12 o’clock thus giving you a Half Moon. The moon at 3 o’clock give you a Full Moon since you are looking at it dead on into the lit half. At 6 o’clock you are looking at the ‘back’ half that is unlit for a New Moon.
Hope that helps.
BTW: Australia will see the moon in the same phase as we do since the earth rotates quicker than the moon orbits to shift its phase from our perspective.
One more note about Chicage and Australia – rather than leaning, it might be a better analogy to open just your left eye, than the right. Two different points on your head representing two different points on Earth. You should see similar, but not exact, views of the baseball/moon. You should observe that how different the views actually are depends on the distance between your eyes and the distance to the baseball.
As already mentioned, this is called counter steering.
Lets say you want to turn left. To turn left, the bike needs to be leaning left into the turn to counter centripidal force. To get the lean started, the front wheel needs to be turned in the opposite direction. This gets the bike leaned over. As soon as the lean is started, that pressure must be released or the bike will end up on its side on the road. At the end of the turn, (to stop the turn) one would turn the wheel further into the direction of the turn. This will stand the bike back up.
Buddhadog,
This only happens, by the way, above a certain speed. If you are going slow enough, the bike will turn in the direction you would expect. The reason the motorcycle behaves as you describe at speed is due to a phenomena called precession. For a thorough explanation of precession, I recommend you look it up - it is a fairly complex subject. You can observe precession with a gyroscope.
I will give you a quick explanation, though. When you try to turn a rotating object, you produce a force at 90 degrees to the direction of rotation. When you push on the left handlebar and turn the front wheel of the bike to the right, you produce a force which makes the whole motorcycle lean to the left. It is the leaning to the left that turns the bike.
crud , back to 4th grade for me then sorry about that got that mixed up
Sorry about that Spiderman,
I seem to have gotten us confused??:eek:??