Note: There is a special note to teachers at the bottom of this post. If you’re a teacher, please be sure to check it out!
My friend Tina is a teacher at the Saegert Sixth Grade Center in Austin, Texas. She asked her sixth grade students to send me questions they had about astronomy, and I answer them on camera. There were so many I had to split this into five parts! I’ll be posting one part every day, first thing in the morning. Monday was Part 1, and below is Part 2.
I think y’all will like number 8 the best.
The questions asked in Part 2 are:
1) Why is gravity different on the Moon?
2) Why are planets round?
3) How deep do the gases on Jupiter go?
4) Are Uranus and Neptune solid ice?
5) Why is Uranus tipped over?
6) Can a moon have a moon?
7) Can you touch a comet and land on an asteroid?
8) Does Titan smell like poop? 
9) Will my school get hit by a meteorite?
10) What would happen if you hit a golf ball on the Moon?
SPECIAL NOTE TO TEACHERS: Many schools block access to YouTube. There is another video hosting platform called TeacherTube, which is designed to be used in schools. I’ve uploaded this video (Part 2) to my channel there, where you can access it in your school (note: the video is in higher-resolution on YouTube). If you do, please let me know! I’d love to know what the students thought of the video — warts and all.
May 20th, 2008 at 9:12 am
“6) Can a moon have a moon?”
Yes, obviously. Each of the so-called planets is a moon of the Sun, and many of those moons have their own moons which stay on orbit for billions of years.
May 20th, 2008 at 9:31 am
Planets aren’t moons. They’re planets.
But remember, too, these are questions from kids. What’s obvious to someone who has been reading about astronomy for years isn’t clear at all to a 12 year old.
May 20th, 2008 at 9:37 am
Perceived gravity is also influenced by the objects rotation. If Earth wasn’t rotating, the gravitational constant (little g, I mean) would be higher.
May 20th, 2008 at 9:37 am
Well, does Titan smell like poop?
May 20th, 2008 at 9:50 am
Didn’t Alan Shepherd hit a couple golf balls during his moon mission?
Thanks.
May 20th, 2008 at 9:52 am
Stop saying Moons. (That’s bad astronomy!) They’re satellites, natural satellites.
May 20th, 2008 at 9:57 am
I think not giving our moon a proper name once we found it not be unique is the bad astronomy here.
May 20th, 2008 at 9:57 am
Great video! Wow, five parts. Can’t wait to see the other three. You really have a talent for explaining things. And I’ve even learned some new stuff.
May 20th, 2008 at 10:04 am
These are good, even for us non sixth graders.
May 20th, 2008 at 10:12 am
The real question is, does Uranus smell like poop?
SOMEBODY had to say it
May 20th, 2008 at 10:17 am
“What’s obvious to someone who has been reading about astronomy for years isn’t clear at all to a 12 year old.”
Sure. But this is an opportunity to broaden their scope of things. It’s like when Sagan said, “The stars are suns, but very far away. The Sun is a star, but close up.” Very similarly, we can point out that the planets are moons, and the moons are planets. Even the Sun is ultimately a massive body orbiting a barycenter. It’s really all the same.
May 20th, 2008 at 10:24 am
As Sagan said “there is no such thing as dumb question.”
May 20th, 2008 at 10:48 am
#3 is a pretty good question for 6th graders.
With the godl balls, how many times stronger than a normal human would you actually need to be to hit a golf ball off the moon?
Anyone can calculate this?
May 20th, 2008 at 11:08 am
Assuming a 0.045 kg golf ball:
To give a golf ball 0 net energy, considering only it’s gravitational potential energy due to the Moon and its kinetic energy, at the average surface of the Moon, you’d need to give it about 127 kJ worth of kinetic energy.
The world initial for initial ball speed is 328 km/h, which give a KE of about 187 J.
So, from an energy perspective, about 680 times.
May 20th, 2008 at 11:58 am
I’m surprised no one mentioned this earlier, but Phil made a BA gaffe: he clearly said that Titan’s atmosphere is composed mostly of methane, when it’s actually a trace gas in an almost pure Nitrogen atmosphere.
Also, wouldn’t Titan actually smell a LOT? I mean, all those complex organic molecules include polycyclic *aromatic* hydrocarbons, so shouldn’t it be the equivalent of living in a claustrophobic gas station?
May 20th, 2008 at 12:07 pm
Ozy:
True, but only barely worth even considering. The acceleration due to the Earth’s spin at the equator is ~3 cm/sec^2, about 0.3% of the gravitational acceleration.
May 20th, 2008 at 12:09 pm
Keep ‘em coming! Man, these are great questions. Simple always makes it better.
May 20th, 2008 at 12:20 pm
I like how you’ve sorted the questions to make a coherent ’story’ out of each session – they seem to tie together nicely.
May 20th, 2008 at 12:23 pm
That is true here, John Weiss, but in general, one can imagine objects which spin fast enough that the apparent gravity is differs significantly from that of a similar, non-rotating object.
May 20th, 2008 at 12:32 pm
Santiago, aaaaarrrrrggg! You’re right. Nuts. Well, I’ll post something on the page correcting that error.
I briefly considered adding in that esters and such might make Titan smelly anyway, but I wasn’t sure, and it seems like a long shot.
May 20th, 2008 at 12:54 pm
Phil, the Gatorade commercial with Tiger Woods,
http://www.youtube.com/watch?v=Mp4n2Wuczl0
he is teeing-off towards Mars.
The golf ball is covered with a ablative material which is heated by the solar wind it is plowing through. This explains the ‘burning up’. :^)
May 20th, 2008 at 1:14 pm
Great videos, BA! On the golf one you could also have mentioned that the ball would go straight, due to the lack of an atmosphere. That would be a real blessing to most earthbound golfers.
Out of curiosity, what is the yellow square on the shelf next to your head? It’s a little distracting.
May 20th, 2008 at 1:27 pm
Trebuchet, the moon still has gravity! So the ball will arc.
The square is a piece of the insulating blanket from Hubble, brought back in 1999. It’s part of an award plaque for people who worked on Hubble.
May 20th, 2008 at 1:30 pm
Trebuchet,
Golf balls would still travel an arc on the Moon. It’s the same principle that makes satellites travel their elliptical orbits out in airless space. If the ball followed a true straight line, it would mean there was no gravitational interaction between the ball & the Moon.
May 20th, 2008 at 1:42 pm
I think what Trebuchet meant was that the golf ball wouldn’t “slice” i.e. curve to the right or left due to the ball’s spin.
Here is video of Alan Shepard hitting golf balls on the moon. Mission control joked about a “slice”.
May 20th, 2008 at 1:50 pm
I look forward to playing a round of golf of Ceres. It will do wonders for my driving distance.
May 20th, 2008 at 2:07 pm
5) Why is Uranus tipped over?
Giggle-giggle.
(Hey! They’re questions from sixth-graders! I can chuckle!)
May 20th, 2008 at 2:15 pm
What about the dimples on the ball? It’s my understanding that the dimples reduce drag AND produce lift. You’re obviously not gonna get any lift or drag on the moon. My mechanical ingenuity and semi-intelligence suggests that the absence of drag would more than offset the absence of lift in making the ball go farther but…
May 20th, 2008 at 3:01 pm
So…is Jupiter basically like a large terrestrial planet that just happens to have a very very dense and extensive atmosphere? I mean if it has a rocky core about 4X the size of the earth, then the rest of it can be considered atmosphere can’t it?
May 20th, 2008 at 3:44 pm
BA, it’s time for you to stop being gainfully unemployed and start teaching in school. I wish I had a teacher who could explain things as well as you.
May 20th, 2008 at 3:50 pm
You can always play golf on the moons of Saturn. Sorta. (Look, I have to plug it: a friend and co-worker worked really hard to make the game…)
May 20th, 2008 at 4:00 pm
Tim G said:
“I think what Trebuchet meant was that the golf ball wouldn’t “slice” i.e. curve to the right or left due to the ball’s spin.”
Ah- that does make sense. Thanks for pointing that out.
May 20th, 2008 at 4:28 pm
Ah, I hadn’t thought about slicing. If so, I retract my snark.
Funny– that whole thing with Alan Shepherd’s golf ball is used by moon Hoaxers, amazingly. “How can it slice if there’s no air on the Moon! And it wouldn’t go ‘miles and miles’!” I have seriously seen those as actual reasons why the landings must have been faked.
May 20th, 2008 at 5:10 pm
Re: poo-smell: “Mercaptan, my captain!” XD
May 20th, 2008 at 5:20 pm
I love these videos at least as much as the kids they’re intended for, but you’ve missed an opportunity to expose them to SI units. Miles? Tons? tsk tsk.
May 20th, 2008 at 6:29 pm
If you want to know whether Titan smells like poop, freeze yourself for about 1,000 years and ask Prof. Farnsworth.
May 20th, 2008 at 7:31 pm
Awesome videos. Is there any chance you can release the source versions as downloadable and under some sort of Creative Commons (or other redistributable) license?
I would love to be able to redistribute these videos here in Australia on some of our websites.
May 20th, 2008 at 10:41 pm
Tim said:
“I think what Trebuchet meant was that the golf ball wouldn’t “slice” i.e. curve to the right or left due to the ball’s spin.”
Exactly right. I had not, however, thought about the distance enhancing effect of the dimples, as Robin T pointed out. So it does not slice or hook, but you may not get the distance you do on earth.
May 20th, 2008 at 10:44 pm
Re: aromatic hydrocarbons, even in the sanctity of a Titan colony, wouldn’t a smell tend to build up over time with repeated cycling of the airlocks? Naturally, you’d want to have really good filters in your environmental system, but it wouldn’t be 100% efficient at removing all traces of outside atmosphere.
Bet you the claustrophobic gas station smell would be overwhelmed by the smell of human, though.
May 20th, 2008 at 11:42 pm
Great series, Phil! Your sense of wonder and enthusiasm comes across well. Very non-patronizing style too; most kids dislike being patronized no less than most adults.
Keep it up. We can never have too many popularizers of good science like you.
May 21st, 2008 at 6:37 am
Hey Phil,
Theres actually another gaffe on your video.. A golf ball hit on earth will go a lot farther than one hit on the moon, because as was briefly mentioned earlier, golf balls have lift. So on the moon without any atmosphere there is no lift. Even though the gravity is less and accounting for friction, the golf ball on earth will go farther. You can do the math if you have the time, but I remember doing this on a fluid dynamics test back in college.
May 21st, 2008 at 7:53 am
Now hold on a second, Dan.
If you hit a golf ball at 65 meters per second (which many pros can surely do) at an angle of 25 degrees (yes, 45 degrees would be optimum for a particular speed), it would travel some 2000 meters.
Anyway, real pros can slice around a tree. So that is one element of the game that would be taken away on airless worlds.
May 21st, 2008 at 11:52 am
That video rocks, content-wise.
Now, what can be improved technically? A descent microphone will get you the most bang for your bucks, IMO. Spend a couple hundred dollars on that, plus an hour to learn howto filter out background noise. Then you’ll be ready for Hollywood.
May 21st, 2008 at 12:28 pm
I’m pretty sure that “fart” is a term regularly used by twelve-year-olds.
I’ll get back to you after I ask my seven-year-old. Might just be the local biochemisty.
May 21st, 2008 at 3:00 pm
The Koldren tell me that “fart” is not an offensive term unless it involves me, broccoli and cheese sauce.
When applied to the description of a moon’s atmosphere, it makes sense to them.
I’m ditching dairy products for a week. Maybe they’ll be able to pay attention instead of laughing.
Neat thing: my 11-year-old asked me to find the mass of SgrA* before heading off to school this morning.
Yay!
May 21st, 2008 at 3:59 pm
BA: You missed a minor point…
The kid who asked if a meteorite would hit his school wasn’t worried about the impact, he (or she) was more likely hoping school would be closed!
So your answer “don’t worry, an impact on your school is unlikely” should have been “sorry, an impact is unlikely, so you’d better start studying for your test!”
I use this thought in my class (college introductory geology). I ask the students to calculate the probability that an impact will cancel their final exam…
May 21st, 2008 at 6:06 pm
“I use this thought in my class (college introductory geology). I ask the students to calculate the probability that an impact will cancel their final exam…”
Sounds like some good motivation to figure out how to move asteroids.
I like it.
May 21st, 2008 at 7:21 pm
Im really glad these videos mentioned NEAR. I didn’t realise we’d done something that awesome. I often have to use the word ‘awesome’ when discussing things I learn from BA. Science really needs better press.
May 21st, 2008 at 7:32 pm
When the Slytheen (sp?) took over Luke, Maria and Clyde’s school a few weeks ago, the kids were greatly amused by the principal’s difficulties with his gas exchange module.
May 22nd, 2008 at 5:38 am
A transcript would be fantastic for the people like me who lack sound, are on dial-up, have really shi-ite computers & no spare cash to fix ‘em up, etc … if that’s possible … (hint, hint, hint.)
Hmm .. sounds like fun though – let me try :
******
The questions asked in Part 2 are:
1) Why is gravity different on the Moon?
Me : It isn’t. Gravity remains the same force everywhere.
2) Why are planets round?
Me : ‘Coz they’d look really silly if they were triangular!
3) How deep do the gases on Jupiter go?
Me : Very … no wait make that very, very, very!
Actually they go so deep they stop being gases and become liquids instead under all the “weight” (or ok mass) of the gases above.
4) Are Uranus and Neptune solid ice?
Me : No.
5) Why is Uranus tipped over?
Me : There’s no up & down in space – from there it just seems that we’re the one’s tipped up.
6) Can a moon have a moon?
Me : yes – in fact our moon has its own artificial moons that are called lunar staellites ..
(Lunar Prospector, Clementine, that recent Chinese spaceprobe {Chang’e was it?} are all still up there aren’t they?)
7) Can you touch a comet and land on an asteroid?
Me : No reason why not if you can afford to develop and launch and be on a space mission to one … Or just find a meteorite sizeable enough to jump upon with both feet!
(BTW There’s one in the Adelaide museum that that’d work for -not that I’ve done so or really recomend trying it!
. )
Does Titan smell like poop?
Me : Your nose would freeze solid there before you could smell anything.
9) Will my school get hit by a meteorite?
Me : Maybe – & maybe you will – but the odds are very very, lo-onng -far worse than for winning any lottery!
10) What would happen if you hit a golf ball on the Moon?
Me : Ask Alan Sheperd Jr. Or watch his video footage & you’ll see.
—–
Yes, yes, I know I’m not giving up my day job any time soon ..
May 22nd, 2008 at 5:43 am
# Muson 20 May 2008 at 10:12 am
The real question is, does Uranus smell like poop?
SOMEBODY had to say it.
No they didn’t.
And its Ouranos that’s “Oo- RAh-nOs” in the proper Greek spelling and pronuniciation anyway.
Now while the IAU are stuffing about with changing things planets-wise (Pluto you’re still a planet to me!)
we’ve got to get them to fix that shocker up once & for all. Sigh.
May 22nd, 2008 at 5:45 am
Darn it by Jove! What happened to my blockquotes there? Argh!
May 22nd, 2008 at 5:49 am
Oh & shi-ite isn’t rude – its a Muslim denomination just a Sunni Muslim isn’t necesarily just one with a sunny nature.
Okay, okay I’ll stop now!
May 22nd, 2008 at 12:53 pm
Wow. I’ve enjoyed your blog for a long time, and, although I have an interest in space and cosmology, I’m learning a lot from these
Will now buy your book!
~Chris
May 23rd, 2008 at 5:52 pm
The smell of Titan reminds me of one of the surprising discoveries of Apollo: the Moon smells like gunpowder.
May 30th, 2008 at 7:07 pm
[...] 1, Part 2, Part 3, Part 4, and Part [...]
June 22nd, 2008 at 6:26 pm
Our moon does have a name and it is not moon. It is Luna but no one ever uses it and we all just call it the moon.