Wednesday, December 31, 2014

Pond Ice

A couple of weeks ago my wife and I took our daughters on a walk through the neighborhood.  It had been cold enough the previous few days that a few nearby ponds had frozen over.  On the day of the walk, however, the temperature outside was close to 50 degrees F.  The ice on the ponds was quickly melting, but had not finished melting yet.  We had fun throwing rocks onto the ice to see if we could break through.  We did.  We then found a couple of large sticks and starting poking the ice near the pond edges.  The cool thing is that the ice was the perfect thickness to break, but not shatter the ice into tiny pieces.  This allowed us to take out chunks of the ice from the pond.

We then threw these chunks out onto the pond ice and watched it shatter into tiny pieces.  The next cool thing we found is that some of the shattered pieces flew far distances across the pond ice.  Why?  The answer is conservation of momentum.  The large chunk of ice has some momentum when thrown.  Momentum must be conserved, disregarding friction, meaning the momentum of each tiny piece must add up to the momentum of the original big chunk.  Some of the shattered pieces moved back toward us while others barely moved at all.  To account for these zero and negative momentum pieces, there must be several pieces with large positive momentums.  These are the pieces propelled forward and travel great distances across the ice.

In the end we had a great time at the ponds.  I felt like a kid again as I cut out pieces of pond ice and threw them across the pond.  Neither of our daughters wanted to leave!  They were having a great time as well.  Fun times!

Tuesday, December 30, 2014

Top Ten Most Viewed Posts

I started this blog approximately 2.5 years ago in May 2012.  In that time I've posted 737 times.  This is blog post #738.  Each month this blog receives about 4,000-6,000 visits.  Which posts are visited the most often?  Below I've linked to the top ten all time viewed posts and the number of views each has received.

1.  The Egg Drop Experiment - 8021 views

2.  Thunder/Lightning Misconception - 7092 views

3.  Can You Get a Moonburn? - 3214 views

4.  Volleyball - 2982 views

5.  What Direction Does the Sun Rise and Set? - 2887 views

6.  Trouble at the Dentist - 2699 views

7.  Sonic Boom - 1218 views

8.  Egg Drop Experiment - 1121 views

9.  Upper Peninsula Trip #6: Ticks - 832 views

10.  Rosetta/Philae Comet Landing Pictures - 790 views

If you haven't seen these posts before, check them out, others certainly have!

Monday, December 29, 2014

Pulling Apart Two Magazines - Paper Friction

How much friction is there people two pieces of paper?  Answer:  Not much.  You can easily test this by placing one piece of paper on top of another and then pull the two pieces apart horizontally against each other.  The two pieces easily slide apart.  But what if you add more pieces of paper?  A really cool experiment to test this can be done using two phone books or two magazines.  My daughters and I grabbed two magazines and started interweaving the pages together.  One page from one magazine on top of the other page, and continue until the two magazines are interwoven page by page.


Now have on person grab one magazine binder on one side and a second person grab the other binder on the other side.  Now pull horizontally.  Do the magazines come apart?  If you pull hard enough, yes, but you have to pull very hard.  The greater the number of pages, the harder it is to pull apart.  My daughters gave it a try and were unsuccessful as you can see in the video below.


We then picked up one magazine and held the bundle vertically to see if gravity could do the trick.  No luck.


The friction force between any two pages is small, but add it up over all of the pages and the force is very large.  Mythbusters did this once with two phone books and ropes and chains were breaking while the books stayed stuck together, simply from the friction force of paper on paper.  

Give it a try, your kids will find it very cool!



Friday, December 26, 2014

This Blog's History: Candle/Air Pressure Experiment

Can you make water "magically" rise up a glass/bowl?  Maybe not with your mind, but with science you can!  This is an experiment I originally discussed last month, but I'm bringing it back to you for This Friday in This Blog's History.  Check it out!  It's very cool!

Candle/Air Pressure Experiment

Thursday, December 25, 2014

How Fast Must Santa Travel

Today is Christmas and along with Christmas comes Santa Claus.  Depending on the age of your kids, they may or may not still believe in Santa, but that's not the point of this post.  Each year on the first day of the second semester of my physics I give my students a thought problem where they have to calculate an approximate speed that Santa must travel to visit every house in the world in 24 hours (ignore time zone changes).  Let's work through it.

To start this problem I assume that Santa begins at the North Pole and slowly moves in circles about a given latitude toward the equator and then to the South Pole.  Let's also assume Santa has some magical powers and doesn't have to physical stop at each house.  He just flies through the air throwing presents left and right.  The presents magically work their way into the houses.  Let's also assume Santa has incredible arm strength and has a throwing reach of 500 meters in each direction.  Thus each swipe around the Earth covers a width of 1 km.

The circumference of the Earth is 40,075 km.  Santa makes circles going down one side of the Earth, so the distance Santa travels down the Earth is half this...20,037 km.  If each swipe has a width of 1 km, Santa must circle the Earth 20,037 times.  So how long is each of these swipes?  At the equator the swipe is 40,075 long, but at the North Pole the swipe is 0 km long.  Let's assume the average swipe is half the circumference of the Earth.  Thus we end up with:

20,037*20,037 = 401,491,387 km traveled.  Add on to that a one way trip back from the South Pole to the North pole and we get:

401,491,387 + 20,037 = 401,511,424 km traveled

Santa must do this in a 24 hour period.  To get Santa's speed we divide distance by time (converting to seconds):

401,511,424/86,400 = 4,647 km/s

That's blazing fast!  But is it physically possible?  The speed of light, the fastest anything with mass can travel is 300,000 km/s, so Santa is traveling less than this.  In our estimate, Santa travels at a speed of 1.5% the speed of light.  Well within the realm of possibility!

Too much geek for one day?  :-)

Wednesday, December 24, 2014

Sky & Telescope Magazine

If you haven't figured it out yet, I'll make it very clear now.  I'm a geek when it comes to science and I love reading science related books and magazines.  I subscribe to a few science magazines and every once in a while drop one and subscribe to another for a period of time.  I recently subscribed to Sky & Telescope.  The first issue arrived the other day and I immediately dug into it.  It's a great astronomy related magazine that explains things in a very general way without dumbing things down too much.  It can get a bit technical in articles that discuss amateur telescopes, but nothing you can't read through and get a basic idea of what's going on.  It's definitely a magazine I recommend for the science lover and anyone with a basic interest in astronomy.  Magazines are a great way to explore a field of science without getting over technical and confusing.


Tuesday, December 23, 2014

Straw Spray Experiment

I credit students in my high school physics class for introducing me to this science experiment/demonstration.  They sent me a link to this YouTube video, provided below, and asked me if I could get it to work, because they were unable to reproduce the experiment.  The idea is to fill a glass full of food colored water and tape a straw vertically inside the glass.  Then take another straw and blow perpendicularly at the very top of the taped straw.  The physics says that blowing air across the top of the vertical straw reduces the air pressure at the top of the straw, causing liquid inside the straw to rise.  As the liquid rises to the top, the air blowing horizontally causes the liquid to spray outward onto the wall.


Being The Cool Science Dad that I am, I had my two daughters help me out with this task.  We set it up just as described in the video and I started to blow through the straw.  The result?  Nothing.  Hmmm....as any good scientist does, we started to investigate why it wasn't working.  We tried various things and eventually cut the straw inside the glass as short as possible.  This reduces the height the liquid in the glass as to rise.

The result?  It worked, although you have to blow very hard into the straw.  I was barely able to get it to work, and my daughters had no luck at all, but it worked!

Try it out yourself!  Just be sure to have towels ready because you'll be blowing liquid out of the glass onto the wall/floor.  It's a cool science experiment because you see water appear to magically rise up the straw and out of the glass.  I say 'appear' because it's not magic.  It's science!

Monday, December 22, 2014

Dancing Pros and Physics

The other week my family and I had the opportunity to go see a Dancing Pros Live event.  If you're unfamiliar with Dancing Pros, check the link below.

Dancing Pros Live

The show is hosted by Alan Thicke and is composed of several top dancers that compete in a entertainment style competition.  I had no idea what to expect from the show, but I was very impressed.  Both of my daughters loved it!  My 4 year old fell asleep after intermission, but my 7 year old was just as amazed as I was at the moves these dancers could pull off.

There's a lot of physics that goes into dancing, much of it centered on balance.  Consider a person standing straight up.  At what point does one topple over?  If you lean over far enough, eventually your center of mass moves outside of your feet.  Everything else being equal, that's the point at which you will fall over.  The muscles in your body will help to avoid this, but eventually you will fall.

At the Dancing Pros Live event, we saw a male dancer do a hand stand, which is already a difficult feat.  Then, while on his hands, he slowly bent the bottom portion of his body over, stomach facing up, and keeping his feet straight out.  He reached a point where he was almost bent over at the waist at a 90 degree angle, and held it for a couple of seconds!!!  WOW!!!!  Simply wow!!!  The muscle strength and control needed to do that is simply amazing!  It looks physically impossible and is unless you have an extremely strong core.

Anyways, if you get a chance, take your kids to a Dancing Pros Live event.  They will love it!!!

Friday, December 19, 2014

This Blog's History: Seeing Your Own Breath

This Friday in This Blog's History I bring back to you a common misconception regarding your own breath.  Sometimes you see it coming out of your mouth or coming out of someone else's mouth.  Why?  Is it smoke?  Steam?  A cloud?  What's going on?  Check out the original post for the answer and for more details.

Seeing Your Own Breath

Thursday, December 18, 2014

Black and White TV

The other weekend my wife, kids, and I actually had a full free day with nowhere to go!  That lasted a whole 30 minutes because I quickly learned I had a plumbing problem to fix that required a trip to the store.  That's a whole other story, however.  In the afternoon we popped a batch of popcorn and cuddled up on the couch together to watch a kids movie.  It was my 4 year old's turn to pick and she chose to watch a movie she picked out at the library earlier that week:  The Smurfs Holiday Celebration.


This is old school Smurfs that my wife and I watched in the 1980s when we were kids.  I was telling this to my 7 year old and she looks up at me and says "was that when it was in black and white?"  Really!?!?!?!  How old do you think I am?!??!?!  It was the 80s, not the 50s.  LOL!  Crazy things that kids say!

Wednesday, December 17, 2014

My 7 Year Old Teaches Science to my 4 Year Old

The other night at dinner my wife and I were making iced tea.  We heated up a container of water, placed the tea bags in, and sat it on the table.  While eating dinner, my 4 year old asks "Mommy, why is there smoke coming out of the tea?"  My 7 year old responds "that's not smoke, it's tiny water droplets."

It took me a moment to realize that she was teaching my 4 year old science.  She was absolutely right.  We think of steam as a gas, but it's not.  The iced tea is evaporating into the air, but as it evaporates into a gas, the gas cools and condenses back into tiny water droplets.  The water droplets take on a cloud, or in this case, smoke type of an appearance.

This was a proud science Daddy moment!

Tuesday, December 16, 2014

Correct Guess

My two daughters recently entered a contest at our local library to win a set of kids magazines geared toward their age.  To win the set of magazines, they had to guess how many Legos were in a jar.  The entry with the closest guess wins the prize.  Some people may claim we cheated, but I disagree.  We simply used math skills to help us out.  I began by letting them know there was a method that would help us with our guess.  I told them that if we know how many Legos tall the jar is and how many Legos across the jar is, we could do a bit of math to get a close guess.  Here's how:

The jar was cylindrical and there's an equation for the volume of a cylinder.  The volume of a cylinder is given by:

V = Base Area*Height = pi*r^2*h

I told them to count the number of Legos high, and they each did.  Then I asked them to count the number of Legos across (diameter) and they both did.  We plugged the numbers in a calculator and they both had a number they wrote down and put in the guess box.  A week later after the contest had ended, I received a phone call letting me know that my 4 year old had the closest guess!  She was only 1 Lego off!!!

So who said knowing math doesn't come with perks?  Okay, perks for my 4 year old, but perks nonetheless!

Monday, December 15, 2014

Fiction Books Promoting Science

The other night my 4 year old picked out a couple of books to read before bed that had a science theme to them.

1.  Biggest, Fastest, Strongest

This book discusses a few of the "extreme" animals in the world in terms of their size and/or what they can do.  For example, what is the largest animal in the world?  Smallest?  Tallest?  Fastest?  The book does a great job introducing young children to these animals and has sizes to scale in the book, comparing the animal to a human.

2.  Magic School Bus Lost in the Solar System

Overall this book does a great job introducing kids to the Solar System through a fictional story.  Granted, it does a horrible job explaining the asteroid belt.  It gives the impression that the asteroid belt is loaded with asteroids that you must dodge to get through when in fact there are millions of miles between any two asteroids.  But if you can get through that part, it's a cool way to introduce kids to space.

There are plenty of other great books out there that introduce kids to aspects of science, but these were the two my 4 year old picked out last night.

Friday, December 12, 2014

This Blog's History: The Celery and Colored Water Experiment

This Friday in This Blog's History I bring to you once again the celery and colored water experiment.  It's a very simple experiment that requires celery, water, and food coloring.  That's it!  Check out the full details in the original post.

The Celery and Colored Water Experiment

Thursday, December 11, 2014

Winter Science Experiments

With winter weather sweeping across much of the country, now is a great time to do a few winter science experiments with your kids.  Here are 2 that are easy to do and allow your child the opportunity to investigate and predict outcomes.

1.  Which freezes first?  Hot water or cold water?  Fill two same sized glasses with the same amount of water and place outside at exactly the same time.  Common sense might tell you that the cold water freezes first since it is already closer to the freezing point of water.  But is common sense correct?  What happens when you reduce the volume of water?  Half the water?  Quarter full?  Etc.?  Try out different volumes of water to see if it has any effect on which temperature of water freezes first.

2.  Place a full, non-opened can of pop outside and wait for it to freeze.  What happens?  Try different types of pop.  Does one can freeze more quickly than another?  Setup a video camera to see the freezing in action.  It may take awhile, so make sure your camera has plenty of memory.

We'll be trying out a few things at my house and I'll post results here when they come in.  The pop can freezing requires a video camera, because inevitably the freezing action happens when you're not looking!

Wednesday, December 10, 2014

Spring Break 2015 Vacation Opportunity

Looking for an awesome science filled spring break vacation for you and your kids?  A great option, although very expensive, is a solar eclipse cruise!  There's a total solar eclipse in March 2015 that will sweep through the northern Atlantic.  The eclipse time itself will only last for a few minutes, but there's a ton of great scenery and sight seeing options in this area.  There are several cruise linesnoffering a solar eclipse cruise.

Faroe Islands Solar Eclipse Cruise

Smyril Line Cruises

Cruise and Maritime Voyages

It's going to cost a family of 4 around $10,000 to do this trip, but what an amazing experience!!!  My wife and I briefly entertained this, but the timing with school and work is horrible and that's not really in our budget this year.

But if it works for you, go for it!!!

Tuesday, December 9, 2014

The S-E-X Picture Frame

The other day at lunch we're all sitting down at the table eating when my wife leans over and asks me, "why does that picture frame say sex on it?"  Um...I looked over and sure enough, there's the word sex.  The picture frame in question, seen below, is a frame the girls made on Halloween with some of their friends.  This particular frame was made by my 4 year old with, gulp, help from me!


My 4 year old was asking me to help her spell certain Halloween related words.  She started with boo, followed by ghost, then cow (because I was a cow for Halloween), and then moo.  I helped her pick out the letters and she stuck them to the frame.  Then I went off to get ready for trick or treating and she finished the frame with random letters.  Several weeks later we noticed that she spelled sex, with a backwards 'e'.  :-)  

Yep, some great parenting going on here.  :-)

Monday, December 8, 2014

Discover Magazine Top 2014 Science Stories

The January/February 2015 issue of Discover Magazine recently arrived at my house.  The major feature in this issue is a recap of the top 100 science stories of 2014.  Very cool!  I highly recommend grabbing a copy of this issue to increase your knowledge of science current events.  The issue is very informative.


I haven't read through the entire issue yet, but glancing through it, the number 1 story is Ebola and the number 2 story is climate change.  I have to say I disagree with this ranking.  Yes, Ebola was a big story, but the only reason it was a big story was due to the misinformation spread by the media and many politicians.  The Ebola story is definitely worthy of top 100 status and should be ranked quite high given the outbreak in Africa.  Remember, however, no one who contracted Ebola in the U.S. died and only two people contracted Ebola in the U.S.  The others treated in the U.S. were treated AFTER they contracted it in Africa.  

To me, climate change is far more important of a story than Ebola.  Climate change affects the entire globe, all 7 billion plus people.  That's my opinion.  Regardless, this is an issue you should definitely check out!

Friday, December 5, 2014

This Blog's History: The Purpose of a Lightning Rod

We've all seen lightning rods, but what do they do?  Not what you think!  I previously discussed this on this blog several months ago, so for This Friday in This Blog's History I bring back to you the original post on lightning rods.

The Purpose of a Lightning Rod

Thursday, December 4, 2014

Does Eating Turkey Make You Sleepy?

It's now a week after Thanksgiving, a holiday that usually involves much over-eating and sleeping on the couch.  What causes the sleepiness after a Thanksgiving meal?  We often hear that turkey is the culprit, but is it really the turkey that causes you to fall asleep after Thanksgiving dinner?  Let's see what the science says.

The saying goes that the amino acid L-Tryptophan, which turkey contains, causes sleepiness.  WebMD describes it better than I can:

"Tryptophan is needed for the body to produce serotonin. Serotonin is used to make melatonin, a hormone that helps to control your sleep and wake cycles."

There you go, turkey causes sleepiness, right?  Not so fast.  The amount of L-Tryptophan contained in turkey is similar to that found in most other poultry products.  Therefore, one should find themselves just as sleepy after eating chicken.  Yet we never associate eating chicken with sleepiness. So what is really going on?

The real culprit isn't the turkey itself, but all of the other food that goes along with it at Thanksgiving.  Potatoes, stuffing, corn, yams, pie, etc.  Most of us tend to overeat at the Thanksgiving meal because there is so much delicious looking food right in front of us.  After overeating the digestion process requires more energy.  It is this excess in used energy that induces sleepiness after the Thanksgiving meal!

So next Thanksgiving, don't blame the turkey, blame yourself for eating too much food.  :-)

For more information, check out the WebMD explanation of turkey and sleepiness.

The Truth About Tryptophan

Wednesday, December 3, 2014

Holiday Gifts For My 4 Year Old

Earlier this week I published a post on science-related gifts for my 7 year old this holiday season.  While shopping for gifts, my wife and I were looking into science-related gifts for my 4 year old as well.  She's not quite at the age where she's as interested in science directly as my 7 year old, but she is interested in several things that develop skills directly related to science.  For example, we usually get her a Lego set of some kind for gifts.  She loves putting them together.  We help her follow the instructions to start, but then she takes them apart and starts building her own creations.  Legos are a tool for her to use her imagination and investigate several scenarios on her own.  That's science!

This holiday season we're giving her a couple of Lego items as gifts, but we are also getting her a GoldieBlox item.  GoldieBlox is a company whose self-described goal is "to get girls building."  Consider it a mix of Legos and Tinker Toys.

For more information, checkout out the GoldieBlox website.



Just as I encouraged you earlier this week, I encourage you again to give a few science related gifts this holiday season.  Provide kids with science opportunities and they will love it and grow to love science as an adult.


Tuesday, December 2, 2014

Underwear Bears

This is what my wife and I found in the living room the other day.


Yes, those are two stuffed bears dressed in my 4 year old's pajamas.  What's that on their heads?  Yes, each bear has a pair of my 4 year old's underwear wrapped over the head as a bandanna.  Why?  Don't ask!  I have a Ph.D. in astrophysics and I'm clueless!!!  :-)

Monday, December 1, 2014

Holiday Gifts For My 7 Year Old

Over the Thanksgiving holiday my wife and I did all of our holiday gift shopping...without leaving the house.  We both sat at the kitchen table, each with a laptop, and started searching and discussing what to get.  My 7 year old is very into science.  She's always bringing science books home from her school's library, and just discovered the science section at the local public library.  In addition, she's always talking about science experiments and coming up with her own.  My wife and I had a few gift ideas for her this holiday season, but I wanted to add something related to science to her list, knowing that she would love it.  We decided on two science items to include in her gifts this year.

1.  An Edible Chemistry Set - This set comes with materials for 15-20 science experiments that produce something edible.  I'm preparing myself to help her with a few the day she opens the gift.  I know she will be super excited about it!

2.  A Microscope - Not an expensive one, but one that she can get her hands on and investigate things on her own.

I know my 7 year old well enough that her eyes will light up when she sees these two science gifts.  At the moment I'm not sure who's more excited, me or her!

I encourage anyone reading this to include a science item or two in your gifts to your children, cousins, nieces, nephews, brothers, sisters, etc.  Expose young children to science and they will grow to love science as an adult.

Friday, November 28, 2014

This Blog's History: What is Frost?

My 7 year old just asked this question to me in the car on the way to an early morning soccer game so I thought this would be a great This Friday in This Blog's History re-post!

What is Frost?

Thursday, November 27, 2014

Happy Thanksgiving!

Happy Thanksgiving to all readers of this blog!  May your Thanksgiving Day be filled with joy and happiness....and a little bit of science!  :-)  Although not everyone has the same meal on Thanksgiving Day, it is very common for a turkey to be served.  A turkey has bones in it.  Instead of throwing those bones away, why not do a bit of science with them?

Grab a couple of turkey bones and clean them so there's no fat and/or turkey left.  Have your child(ren) test the strength of the bones by bending them.  They should notice that the bones are hard to bend.  Next fill a jar with vinegar, drop the bones inside, and close the jar.  Let sit for 3 days, take out the bones, rinse them, and test the strength.  Do the bones bend?  They should!

Normally one does this with chicken bones since it is more common to have chicken bones than turkey bones, but one can easily modify this on Thanksgiving when turkey is more likely to be served.

I haven't done this experiment with my kids yet, but I think later today we'll test it out!

Wednesday, November 26, 2014

Holiday Gifts for the Geek in Your Family

The holiday season is upon us and many of us are beginning or thinking about beginning our gift shopping.  We all likely have a geek somewhere in the family (being a geek is a good thing...I'm one!) and it can be tough finding gifts for the geek.  I recently came across an online store that offers gifts specifically for the geek.

Think Geek

Think Geek has gifts for both kids and adults.  Gifts include clothing items along with other accessories.  For example, they have a Doctor Who TARDIS lunchbox!!!

Doctor Who TARDIS Lunchbox

How cool is that?!?!?  I want one!

Tuesday, November 25, 2014

Quick Temperature versus Air Pressure Experiment

The other day my two daughters completed a very simple science experiment without even knowing it!  My wife and I were working on making dinner and both of our daughters went outside to the backyard to play.  The brought with them a large plastic ball filled with air and were kicking it around for about 45 minutes.  When it was time to come in for dinner, they noticed that the ball appeared to have less air in it and asked if it was leaking.


So what happened?  Was it a leak?  Nope, no leaks.  The ball was outside long enough and the temperature was low enough outside that the air temperature inside the ball dropped quite a bit.  When air temperature drops, the particles in the air move around more slowly and bounce against the sides of the ball wall less frequently.  This results in a drop in air pressure inside the ball and thus explains why the ball appears to have lost air, as shown above.  

Once the ball was brought inside it only took a couple of minutes for the air temperature to increase and for the ball to "re-inflate".  No air was added to the ball, but as the air particles inside gained speed, the inside air pressure increased.  

Very cool!  This just goes to show you that science surrounds you and is easy to find if you just take a moment to stop and look for it.


Monday, November 24, 2014

Candle/Air Pressure Experiment

Ever wonder how you can "magically" get water to rise up a glass?  Now you can do it yourself through this simple experiment.  Begin by lighting a small candle.  Fill a bowl of water colored by the food coloring of your choice.  Place the candle in the bowl of water, making sure the candle is tall enough such that the water level is below the candle wick.  See below.



Now take an empty class or jar (canning jars work great) and use it to cover the candle.  The flame will use up the remaining oxygen in the jar and go out.  As the flame diminishes and goes out, watch the water level in the jar.  It will slowly start to rise up the jar!  Very cool!  See our video below.


So why does the water appear to break the theory of gravity and rise?  The candle quickly heats the air inside the jar.  The air has nowhere to go.  As the flame diminishes, the air temperature quickly drops, and then drops even further as the flame goes out.  Colder air compresses into a tighter space and the air pressure is greater than the force of gravity pulling the water down.  Therefore, the water level inside the jar continues to rise!  If we had a taller candle, we could have tested how far the water level would rise.  Unfortunately all of our taller candles were larger than the jar so we couldn't test this.  Despite this, it was still a very cool science experiment.




Friday, November 21, 2014

This Blog's History: The Pop Can Race

This Friday in This Blog's History I bring back to you the pop can race experiment.  Which reaches the bottom of a ramp first?  A full pop can or an empty pop can?  Read the original post to find out.

The Pop Can Race

Thursday, November 20, 2014

Light-Years or Years?

My 7 year old recently brought home a book titled "First Space Encyclopedia".  It looks very cool and appears to be packed full of space-based information.  She just checked it out, so we haven't read much of it yet, but this morning while waiting for the bus, we read through the first page.  Each page has a fact question at the bottom with an answer on the next page.  The fact question on the first page was:

Q:  How old is the Universe?

Cool!  A very important question.  The answer?

A:  The Universe is just under 14 billion light-years old.

Um....????  What?  The "just under 14 billion" part is fine.  That's correct.  The age of the Universe is 13.8 billion ___________.  The key part is the unit that goes in that blank.  A light-year is NOT a unit of time.  A light-year is a unit of distance and describes how far away something is.  The edge of the Universe is 13.8 billion LIGHT-YEARS away, but that is not the same thing as age.  The answer to the question needed to be "just under 14 billion YEARS old."

It may seem like I'm being nit-picky here and making a big deal over nothing.  I argue that I'm not.  This may seem like a small thing, but this is how misconception develop, fester, and spread through society.  Whoever edited this book made a big mistake and thousands of kids will read this book and develop a misconception over the term "light-year".  It's a shame because the rest of the book looks great!

Wednesday, November 19, 2014

Science Rocks!

The other day my daughter brought home a science experiment book from her school's library titled Science Rocks.



The book was filled with awesome science experiments, many of which we had already done, but several of which were new to us.  Many of these will appear in this blog over the next several weeks.  One already has.  A few days ago I pointed readers to an experiment to Remove Salt from Saltwater.

Check out your local library for this Science Rocks! book or you can get it at Amazon here:

Science Rocks!

Tuesday, November 18, 2014

The Memory of a Goldfish

We shouldn't feel bad for a goldfish in a small bowl because the goldfish has a memory that is so short it will forget its surroundings by the time it reaches the other side of the bowl, right?  Unfortunately this is a misconception that started somewhere and got passed down to the point that most people think it's true.

Scientific studies show that the memory of a goldfish last much longer than mere seconds.  In fact, goldfish have the ability to retain memories for several months!

Three Second Memory Myth

Goldfish Do Not Have a 3 Second Memory

Granted, the memory span of a goldfish may exceed that of other types of fish and is certainly much less than that of a human, but it is not the few seconds that is commonly thought.  So if you have a goldfish, maybe get your fish a bigger bowl.

Monday, November 17, 2014

Rosetta/Philae Comet Landing Pictures

Unless you've been living in a cave, you've likely heard about the recent spacecraft that landed on a comet.  Normally you'd think of this as a NASA accomplishment, but it was actually the European Space Agency (ESA).  The Rosetta spacecraft launched in March of 2004, did a flyby of a couple of asteroids, began to orbit the comet (67P/Churyumov-Gerasimenko) in May of this year, and then on November 12, 2014, successfully landed a probe, named Philae, onto the surface of the comet.

This is an amazing accomplishment, something that had never been done before!  The harpoons to latch onto the comet did not work correctly, and the probe bounced upon landing, but was able to successfully come online, take picture, and send those pictures back to Earth!  AMAZING!!!  There's concerns that the probe is in a place where it won't receive enough energy through the solar panels to do much more, but nonetheless, this is a hugely successful mission!  It just goes to show you that humans can do amazing things when they work together!

Sit down with your kids and show them some of the pictures that are coming back from Philae.  They are simply amazing and show us the details of a comet's surface at a resolution never before seen!

Rosetta/Philae Mission Page


Friday, November 14, 2014

This Blog's History: Understanding Statistics

This Friday in This Blog's History I bring back to you a post discussing the importance of understanding statistics before reporting said statistics.  We see statistics thrown at us left and right every day through the internet, radio, TV, magazines, friends, teachers, parents, etc.  However, without understanding the science behind the statistics, numbers can be misused and twisted to prove an ideological point.  Don't let this happen.  Take time to understand the science behind the statistics.  Otherwise you might misrepresent the data and come across as an idiot and no one wants that!  :-)

Colder than Mars...Really?!?!?!

Thursday, November 13, 2014

1,000 Books Read!

In September 2012, my 4 year old (then 2 yr old) started a program at our local library called "1,000 Books Before Kindergarten".  We received a binder to record the title and date of each book read.  After each 100 books read, she was able to pick out a prize and a new book to keep at home.  Each time this happened was a day of excitement at the library for her.  I'm now happy to report that she/we read her 1,000th book last month!

Research study after research study shows that reading out loud to your children at a young age is the "single most important activity leading to literacy acquisition."

Importance of Reading Aloud

Library programs such as the one my daughter just completed are a great way to get parents to read to their children by providing incentives.  E-books are becoming more popular and are becoming a greater market share of all books, although recent stats show this increase leveling off.  I'm a big e-book reader, but I still love going to the library and showing my kids how to explore the library.  I'm often like a little kid when I go to the library, searching the stacks for a new author or new book series to read.

My point is to not forget about your local library.  It's a great resource for you and your children and often provides several programs to encourage reading.  Take advantage of these programs and let your kids explore the wonderful world of reading!

Wednesday, November 12, 2014

The Power of "I Don't Know"

Kids have a tendency to ask many, many questions, most of which seem to come out of nowhere and are completely unrelated to anything going on at that moment!  One of the joys of parenthood!  Many times, and I would argue most of the time, your kids probably ask questions that you don't have a clear answer to.  I know my kids do.  Instead of faking through an answer to shut your kid up, or saying something based on something you thought you once heard, don't be afraid to tell your child "I don't know."

I think that too often parents and caregivers are afraid to tell a child they don't know the answer for fear of appearing dumb or uniformed.  I'm telling you to stop worrying about that.  Your kids are still going to see you as the center of their universe even if you admit that you don't know the answer to something.  There are advantages to admitting that you don't know.  It shows your kids that you are not perfect and that nobody is.  It also provides an opportunity to search out an answer WITH your child.

If your child asks you an obscure question about a dinosaur, for example, tell them you don't know (assuming you really don't), and then head to the computer or library to search for the answer with him/her.  This will help show your child the power of researching answers to questions and is a great bonding experience between you and your child.

So the next time your child asks you a question you don't know the answer to, don't hesitate.  Just say "I don't know" and then find the answer together!

Tuesday, November 11, 2014

Is Coffee Bad For You?

Is coffee bad for one's health?  Given the amount of coffee (and other caffeinated products) people drink, it's an important question to ask.  Like me, you may have heard that coffee can stunt one's growth or that it can lead to a greater risk of cancer down the road.  But is this true?  If it is, then there's a legitimate reason to stop drinking coffee.  If not, then by all means drink that coffee.

To answer this question we must turn to science.  There have been several studies done on the effects of drinking caffeinated products.  According to the Mayo Clinic:

"Recent studies have generally found no connection between coffee and an increased risk of cancer or heart disease. In fact, most studies find an association between coffee consumption and decreased overall mortality and possibly cardiovascular mortality, although this may not be true in younger people who drink large amounts of coffee."

In addition:

"Studies have shown that coffee may have health benefits, including protecting against Parkinson's disease, type 2 diabetes and liver disease, including liver cancer. It also appears to improve cognitive function and decrease the risk of depression."

That's good news, right?  For the most part yes.  However, it's important to note that there are some possible side effects to drinking coffee.  From the Mayo Clinic:

"High consumption of unfiltered coffee (boiled or espresso) has been associated with mild elevations in cholesterol levels. And some studies found that two or more cups of coffee a day can increase the risk of heart disease in people with a specific — and fairly common — genetic mutation that slows the breakdown of caffeine in the body. So, how quickly you metabolize coffee may affect your health risk."

Here are the links to the Mayo Clinic comments on coffee consumption, as well as one from Harvard that concludes the same thing.

Mayo Clinic and Coffee Consumption

Coffee and Health

The main point to be drawn from this is that coffee does NOT stunt one's growth, nor does it lead to a greater risk of cancer down the road.  Coffee can have some health benefits, but can possibly lead to some health problems if one drinks too much.  However, a cup day appears to be perfectly fine, so go ahead and enjoy that coffee!  One last thing.  If you find yourself struggling to fall asleep at night or shaking/trembling after drinking coffee, you probably need to reduce your consumption or stop altogether.

Monday, November 10, 2014

Balloon Propelled Toy Car

I have to begin by giving my 4 year old's pre-school provider props for this one.  The other week my 4 year old's pre-school provider helped each of the students build balloon propelled toy cars, as seen below.


How does it work?  It starts with Newton's 3rd Law of Motion which states that for every force there is an equal and opposite reaction force.  The balloon is filled with air and held tight at the end.  When the end of the balloon is released, the greater outside pressure force collapses the balloon and pushes the air out.  The air from the balloon pushes against the air outside the balloon, which in turn pushes right back, propelling the car forward. 

Very cool!  Build your own and try out larger balloons.  What works best?  What type of balloon gives the greatest car speeds?  There are many things one can test out here.

Friday, November 7, 2014

This Blog's History: The Balanced Fork

This Friday in This Blog's History I bring back to you a very awesome demonstration that tests the concept of center of mass.  Two forks are balanced on a wine glass in a way that doesn't seem possible.  And there's fire!  If you haven't already seen it, check the original post link below and watch the video!

The Balanced Fork Experiment

Thursday, November 6, 2014

The Rotting Apple Experiment Results

Last week my daughters and I cut an apple up into slices, dropped 1 slice in several canning jars, and dropped something in each canning jar.  We sealed the jars and watched the apples over the next several days.  The goal was to take a look at how different substances, such as salt, water, sugar, etc., effect the decay of the apple slice.  Below is a picture of the apple slice that we used as a control (in jar by itself) after 7 days.


Slightly browned, as you might expect.  Next is the picture of the apple slice placed in water.


Much browner.  Next comes the apple placed in salt.


Salt is a preservative and the apple slice still looks very fresh!  Next is an apple placed in baking soda.


The baking soda did a horrible job preserving this apple slice!  Next is an apple placed in brown sugar.


Not as bad as the baking soda apple.  It's interesting how the brown sugar turned into a liquid after a few days in the jar.  Next, and last, is an apple in white sugar.


Still very brown.

To conclude, the salt did the best job keeping the apple fresh, followed by air by itself.  The other materials quickly turned the apple slice to some shade of brown.

This was a cool, week-long experiment that you can easily do in your home with your kids.  What other substances could you put in with the apple?  







Wednesday, November 5, 2014

Fungus Garden Success

I recently posted a few photos showing the start of a fungus garden my two daughters and I made.  We took a large canning jar and dropped in several food items.  We dropped in bread, cheese, lunch meat, and a Girl Scout cookie.


We then checked each day to see if anything was growing on the food items.  It took 7 days, but finally some mold started to grow on the lunch meat.  Then it spread to the cheese and eventually to the bread at the 10-12 day mark.


Mmmm...yummy!  LOL!  Yep, a successful fungus garden!  Try one out with your kids and see how quickly mold grows on different food items.  Nothing was growing on our cookie after 10 days, but the cookie did break up into several pieces as the days went by.  


Tuesday, November 4, 2014

What is Dew?

We've all seen dew develop on grass, glasses of water, soda cans, windows, etc.  But what is dew?  That's the important question.  Once we see something, we want to be able to adequately explain it.  So what is dew?


Dew occurs when water vapor in the air condenses to a liquid on a surface.  How does that happen?  Take a glass of ice water for example.  Unless you have a well insulated container, drops of water (dew) will form on the side of the glass.  It's not water seeping through the glass.  I used to think this as a kid, but I was completely wrong. :-) Instead, it has to do with changing air temperatures.  The air immediately surrounding the glass cools as energy transfers from the air to the glass.  As the air cools, water vapor in the air drops temperature and changes phase from a gas to a liquid on the glass. 

The same occurs for pop cans, windows, plants, etc.  If the object causes the air around it enough to change the phase of the water vapor in the air, dew forms.  

There you go.  Knowledge is power!

Monday, November 3, 2014

Vote for Science!

Tomorrow, Tuesday, November 4, 2014 is election day in the United States.  It isn't a presidential election, but mid-term elections are just as important.  Every seat in the U.S. House of Representatives is up for election as well as 1/3 of the seats in the U.S. Senate.  On top of that, every local community will have additional elections for state senators, state representatives, local city/county representatives, along with possible referendums on various issues.  I encourage you to vote for politicians who have education and science in his/her best interest.  Without science education, this country cannot survive.

Take time to research the candidates on your ballot and please, please, please, go out and vote.  Voting is the number 1 thing you can do to improve your community.  Take your kids to the polls.  Talk to your kids about how elections work.  If your kids see you taking the time to vote, they'll see how important it is and become voters when they are adults.

Again, tomorrow, Tuesday, November 4, 2014 is election day.  Go out and vote!!!

Friday, October 31, 2014

This Blog's History: Does it Sink or Float?

This Friday in This Blog's History I bring back to you a simple science experiment I did with my daughters this past summer.  We took a jar of water and started taking random food items to see what floats and what sinks. 


There's nothing complicated about this experiment, but ask your kids what they think and why before you test out the food item.  The thought process that goes into the prediction is the science.  If one is right, awesome!  If not, why not?  What was learned?  

Thursday, October 30, 2014

The Rotting Apple Experiment

My daughters and I recently set up an experiment to see how different substances can affect the rate at which an apple slice rots.  We cut up an apple into several slices, placed a single slice in several canning jars, and then placed a small amount of a substance in each jar.  We then closed the lids and will closely monitor how quickly each slice rots.  Here's what we have in each jar.

Jar 1 - Nothing.  This is our control jar to see how an apple slice rots from air alone.

Jar 2 - Water.

Jar 3 - Salt.  Salt absorbs moisture.

Jar 4 - Baking Soda.

Jar 5 - Brown Sugar.

Jar 6 - White Sugar.  Is there a difference between white and brown sugar and its affect on an apple slice?  We shall find out.


These apples will definitely be harmed in this experiment, but in the process we will learn something!  :-)

Wednesday, October 29, 2014

October 23, 2014 Partial Solar Eclipse Recap

Last week I pointed out an upcoming partial solar eclipse on October 23, 2014.  I set up a telescope on top of a nearby parking garage, as seen below.


It was still clear enough out at the time to see a huge cluster of sunspots which was very cool!  However, a few minutes later the clouds rolled in and never cleared leaving me and about 40 students out of luck.  Bummer.  Oh well, I'll try again in 3 years when the next solar eclipse in the continental U.S. makes an appearance.

Tuesday, October 28, 2014

Starting a Fungus Garden

My daughters and I decided to start our own simple fungus garden.  'Fungus' and 'garden' in the same sentence equals one cool science experiment!  We've just started the experiment, so I won't have results to show for another week or two, but here's how you start the garden.

Begin with a large, clear plastic or glass jar.  Then toss in a few different food items, such as bread, fruit, cheese, lunch meat, cookies, chocolates, etc.  Whatever you want to toss in is fine.  Then spread a couple of teaspoons of water in the jar for added moisture.  Seal the jar with a lid and you've started a fungus garden.  Ours is shown in the picture below.



Each day over the next two weeks we'll closely examine the contents of the jar to determine which have mold growing first and how quickly.  Honestly, I don't know what to expect, so I'm just as interested as my girls are.  We should have result pictures to post in a week or two.  

Monday, October 27, 2014

What is Fog?

We've had several foggy days this fall in our neighborhood, which led my 7 year to ask me, while waiting for the bus one foggy morning, what is fog?  Is it a cloud?  Is it something else?  What is it?


We've all seen fog come and go, but what is it?  How does it occur?  Fog is nothing more than a collection of water droplets and/or ice crystals.  It's basically the same thing as a misty day, except the visibility is much worse in fog than it is when it is misting.  This makes it the same as a cloud, but on the ground.  That begs the next question.  How does a cloud form on the ground?  

Fog forms when water vapor near the ground cools and condenses (changes phase) from a gas to a liquid, hence the tiny water droplets.  How this happens can differ depending on the type of fog.  A great source for this is:


In most cases, the fog will "burn" off as the sun rises.  The temperature of the water droplets increase and change phase back into a gas.  

Friday, October 24, 2014

This Friday in This Blog's History: Mixing Water and Pepper

This Friday in This Blog's History I bring back to you a cool science experiment my daughters and I completed last month.  What happens when you mix pepper and water?  The results may surprise you!

Mixing Pepper and Water

Thursday, October 23, 2014

Drinking Through Straw

We've all drank through a straw before, but how does drinking through a straw work?  Are you sucking up the water?  Not really.  What happens when you suck on a straw is that you remove the air in the tube.  The atmosphere pushing on the liquid in the glass at all times.  When the air from the straw is removed, the air pressure on the water is greater than the air pressure in the straw.  Therefore, the air pushes water in the glass up the straw.

Physics tells us there's a limit to the height of a working straw.  Construct a straw several meters in length and you'll find it impossible to suck water out of it.  Why?  The force of gravity acting to pull the water back down the straw increases as more water is pushed up the straw.  When the downward force of gravity equals the force pushing the water upward, water can no longer be forced up the straw.  Make a straw too long, and it doesn't work.

My daughters and I set out to simulate this by using a regular straw.  We took a jar of water with a lid, poked a hole in the lid, slid a straw through the hole, then sealed the hole with play-doh.


Sealing the hole with play-doh prevents outside air from entering the jar.  The only air pushing the water up the straw is the air inside the jar.  The task is to try to suck up a mouthful of water.  At first a little water comes up the straw, but if the hole is sealed, that's it.  There's not enough air pressure inside the jar to continue pushing water up the straw.  Cool stuff...plus you get to use play-doh!!!

Wednesday, October 22, 2014

Ebola Statistics

The news cycle is currently focused on Ebola, and if you haven't noticed, then you really need to pay attention to the world around you.  :-)  It's important, however, to put Ebola in perspective.  Yes, Ebola is a very deadly virus and we should not underestimate the importance of controlling its spread.  At the same time, however, we need to make sure that we aren't exaggerating the possible spread of Ebola.  Right now Ebola is about the only thing the news and politicians alike are discussing.  There's even a politician saying that anyone found with Ebola should be "humanely executed."  Wow...just a tad bid overboard I'd say.


Now that may be a very extreme comment, but many politicians are asking for travel bans from West Africa to the U.S.  Let's look at the statistics and let's begin with a humorous look at the statistics.  You may have seen the following image trending on Facebook.


Yes, it is a silly comparison, but also a true comparison.  Kim Kardashian is only 34 years old and been married 3 times.  Ebola has killed exactly 0 people who contracted it while in the United States.  At the time I write this, 3 people have officially contracted Ebola within the U.S. borders.  The first, a nurse in Texas, is in good condition and appears to be on the path for a complete recovery.  This doesn't mean that no one who contracts Ebola in the United States will die or that there won't be more cases.  Personally, I doubt we will see a number greater than 10 for number of Ebola cases contracted within the U.S.  

Again, we should not underestimate the threat of Ebola and we should put every REASONABLE measure in place to prevent the spread.  I wish that U.S. citizens would take other common viruses just as seriously.  Take a look at the graph below.


In this graph the 1 Ebola death comes from the patient first diagnosed in the U.S., but contracted it while in West Africa.  Take a look at the flu deaths over the same 9 day period?  WOW!  Why are people not as worried about the flu as they are of Ebola?  Yes, if one contracts Ebola, that person is much more likely to die than a person who contracts the flu.  The flu, however, is an airborne virus that is much easier to spread from person to person than the bodily fluid-borne Ebola virus.

If you are scared of contracting and dying from Ebola, then I must assume you are 1,110 times more scared of dying from the flu virus.  No?  Based on death statistics, you should be.

My point is that yes, we need to be serious about Ebola, but we need to be just as serious about other diseases.  Ebola is simply NOT something to be worried about.

For a more detailed description of Ebola, check out the Mayo Clinic.


For more information on the number of Ebola cases in the U.S., check out the following link from the CDC.


Tuesday, October 21, 2014

October 23, 2014 Partial Solar Eclipse

If you enjoyed the total lunar eclipse on October 8, 2014, then you will definitely enjoy the partial solar eclipse that will take place on October 23, 2014.  A solar eclipse occurs when the Moon positions itself in a direct line between the Sun and the Earth.  The Moon is a much smaller object than the Earth, so total solar eclipses are very rare.  When one occurs, you have to be at a very specific location on the Earth.  See the map of past and upcoming paths of solar eclipse totality.


If you're outside the paths shown above, you'll still see a partial solar eclipse as long as you aren't too far from the path of totality.  More often, totality is never reached and one can only see a partial solar eclipse.  That's the case with the October 23 solar eclipse.  If you live in North America, you'll have a chance to see the eclipse.  Using a telescope with a solar filter, or proper glasses, you'll see the Moon blocking part of the Sun's disk.  The following site provides help on how to safely view a solar eclipse.


For more details and exact start/end times of the October 23, 2014 eclipse, visit the following website:


This is another great observing opportunity for you and your kids and it takes place during normal awake hours!  Don't miss out!

Monday, October 20, 2014

Egg Drop Results - Historical

Readers of this blog know that I've done the egg drop experiment several times with my high school students.  We just finished the project again this Fall.  I started the project during the Fall 2007 term and have continued it each year in my high school physics classes.  My students did a great job this fall and being the geek that I am, I dug through all of my notebooks and tabulated the results to determine survival rates of dropping from specific heights.  I left out the Fall 2007 term in my results since that group of students had a full sized grocery bag to use which made the project a bit too easy.  The table below shows survival rates for 102 ships starting with the Fall 2008 term and ending with the 2014 term.

2 feet survival rate = 100%
6 feet survival rate = 94.12%
2nd floor survival rate = 72.55%
3rd floor survival rate = 50.00%
4th floor survival rate = 34.31%
4th floor (rocks) survival rate = 12.75%
4th floor (rocks, upside down) survival rates = 5.88% (5 ships all time)
4th floor (rocks, thrown downward) survival rates = 2.94% (3 ships all time)
4th floor (rocks, thrown upward) survival rates = 1.96% (2 ships all time)
4th floor (rocks, thrown outward) survival rates = 1.96% (2 ships all time)
This year's winner is one of the 2 ships all time that survived everything we could do to it!  It finally broke when I removed a few pieces!!!  Here's what it looked like, minus the sandwhich bag I removed.

A big congratulations to these two students!

Friday, October 17, 2014

This Friday in This Blog's History: Removing Salt from Salt Water

This Friday I bring back to you a very cool experiment involving salt water.  Drinking salt water is not healthy for your body due to the salt content.  Therefore, before drinking it, one needs to remove the salt.  This post shows one method to remove the salt from salt water.

Removing Salt from Salt Water

Thursday, October 16, 2014

Making Clear Ice Cubes

Have you ever tried to make clear ice cubes?  No?  Then check out any ice cubes in your freezer.  Try freezing a class of tap water.  You'll find that finding and/or making clear ice cubes is very difficult.  Although you don't see them, water out of the tap contains small air bubbles.  As the water changes phase into ice, the bubbles expand and give the ice cube a cloudy appearance, as shown in the "cloudy" ice cube from my own freezer.


You probably don't have a need of making clear ice cubes, but it is possible to do.  Begin by boiling a pot of water.  The boiling process removes air bubbles in the water.  After boiling the water, very slowly poor the water into a freezer safe container.  It's important to pour the water very slowly along the side of the container.  Pouring too quickly or jostling the container will re-introduce air into the water.  Seal the container and place it in the freezer for a few hours.  Once the water has frozen, you should see a more clear ice cube.


Although not perfect, the picture above is our attempt to make a clear ice cube.  The container on the right is standard tap water.  The container on the left is frozen water after the boiling process.  The picture doesn't do this experiment justice, but the ice on the left is more clear than the standard tap water ice on the right.

Give it a try!


Wednesday, October 15, 2014

Updated Blog Stats

Because I like statistics I've continued to plot the progress of page views on this blog.  I'm happy to report that page views continue to increase as each month goes by.  Below is the latest chart showing the average daily views for each month starting May 2012 and ending with September 2014.


Aside from a couple of peak months followed by declines, the general trend is upward, with nearly 200 page views per day last month.  Hopefully soon I'll see this blog consistently crack 200 page view per month.  Getting close!

Tuesday, October 14, 2014

Balanced Fork Experiment

Here's a very cool science experiment my two daughters and I tested out the other day.  It's a classic center of mass experiment where you balance something that appears to be impossible to balance. We began by intertwining two forks and jamming a toothpick between them, as shown below.  Then it's a matter of placing the toothpick/fork on the edge of any glass.  It may take a moment or two, but you should be able to balance it.  It is very cool looking, as seen below!


Why does it balance?  It's all about center of mass.  If an equal amount of mass is on each side of the balance point, the object will balance.  If not, the object topples over.  Because the forks curve around the sides of the glass, the fork/toothpick combo remains balanced.  To make the experiment even more impressive, light the toothpick on fire and watch it burn all the way to the glass edge.  It will still remain balanced!  See our video below.  Very cool!


And here are the final pictures.  



Give it a try!  This experiment is sure to wow your kids!


Monday, October 13, 2014

The Pop Can Race

My 7 year old has been checking out science experiment books from her school's library which has given us several ideas for testing out different concepts in science.  Recently, one science experiment struck me as odd, and well...simply wrong!  The idea of the experiment is very simple.  Take a full pop can and an empty pop can of the same size, start them at the top of a ramp, and release at the same time.  Which reaches the bottom first?

Galileo showed that all objects accelerate at the same rate regardless of size/shape/mass, in the absence of friction.  Without air, a golf ball and a feather, when dropped at the same time will reach the ground at the same time.  This has been shown in vacuum tubes when the air is pumped out.  In real life situations, friction always plays a role.  The science experiment book stated that the empty pop can will always reach the bottom of a ramp first because there's less friction acting on it.

This immediately struck me as incorrect because friction isn't the only force in play.  Granted, the force of friction between the can and the ramp is probably greater for the full can.  I'm not denying that but air friction probably plays a bigger role on the lighter can.  I don't know for sure, I'm just suspecting this.  However, my concern here isn't friction.  My concern is the rotation of the can.  Rotating objects are a bit more complicated.  If the mass is distributed in different ways, the inertia of the object differs.  An empty can, with all of the mass on the outside, has a greater moment of inertia than the full can.  As a result, the empty can takes a bit longer to start its motion.

This is a common physics topic in my high school classes and there are several demos I show with rings and solid cylinders to hammer this point home.  The solid cylinders always beat the rings in a race down the ramp.

My daughters and I decided to test this out ourselves and sure enough, the full pop can ALWAYS reaches the bottom of the ramp first.  The book is simply wrong on this.  See our video below.


Later we raised and lowered the ramp and the full pop can still ALWAYS wins!  As you can tell from the video, my 4 year old was quite excited!  LOL!  Try it yourself.  If your kids get as excited as mine were in the video, then you've killed a good 30 minutes of time on a rainy or too hot day!

Friday, October 10, 2014

This Friday in This Blog's History: Does the Moon Rotate?

This Friday in This Blog's History I bring back to you a very common misconception regarding the Moon.  The same face of the Moon always faces Earth.  Because of this, many people think the Moon does NOT rotate, but in fact, it does.  The fact that only one side of the Moon faces Earth tells us that the Moon MUST rotate on its own axis.  For full details, check out the original post below.

Does the Moon Rotate?

Thursday, October 9, 2014

150 Science Experiments

My 7 year old is big into science experiments lately.  After returning her Science Rocks! book from her school's library, she came home that same day with another science experiment book, titled 150 Science Experiments.  The best part was her excitement after getting off the bus.  It was the first thing she wanted to talk about!


Granted, we've done a number of these experiments already, but we found a few we haven't done and added them to the to-do list of science experiments.  I encourage you to find this book at your local library.  It's also available on Amazon.

150 Science Experiments

It's a great book for a weekend of science experiments, although it's important to plan ahead and pick up needed supplies.