The Sonic Boom

A sonic boom occurs whenever an object is moving faster than the speed of sound.  Because an object moving faster than the speed of sound moves ahead of the sound waves it produces, those sound waves cannot move out of the way of each other.  The waves compress together and form a shock wave that sounds like a big boom when it reaches the human ear.  We most commonly associated sonic booms with fighter jets that fly through the air very quickly.

However, a fighter jet is not needed to produce a sonic boom.  A simple bullwhip, similar to the one Indiana Jones used, produces a small sonic boom that you hear as the crack of the whip.  The tip of the whip moves faster than the speed of sound, creating a shock wave.

The big sonic boom misconception is that the sonic boom takes place the moment the object breaks the sound barrier.  This isn't true.  It is true that an object moving at the speed of sound produces a sonic boom, but an object moving faster than the speed of sound also produces a sonic boom.  In other words, an object continually produces a sonic boom as long as it is moving at or faster than the speed of sound.  You only hear it once because that is when the waves hit your ears.  There's no real physical barrier that the fighter jet is breaking through.  It's a simple bunching together of sound waves.  

Presenting at a Conference

As my daughters grow up I hope to teach them the skills necessary to speak in front of a public audience.  I'm an introvert so I'm not all that comfortable speaking in front of an audience, but ironically I'm a teacher and speak in front of an audience every day!!!  Every once in awhile I speak at a conference.  When I do so, I go to great lengths to prepare myself for my presentation.  I even practice it ahead of time out loud so that I know if my presentation is too short or too long given the allotted time.  I know I'm not a perfect speaker, but because of the effort I place into my own talks, I expect others to do the same.  I have a very high standard for conference presenters.

Conference presenters are a crap shoot.  Some are excellent and you can tell that they spent considerable time preparing.  Others simply choose to wing it, and the resulting talk is horrible.  Here are a few pointers for future conference presenters.

1.  Don't ever say "this should be pretty short, leaving plenty of time for discussion".  When I hear these words, I know the presenter has no clue how long his or her talk will last.  Nearly every time I've heard this, the presenter goes OVER the allotted time.  This is very frustrating.

2.  Don't go over the allotted time.  Don't treat your audience as if what you have to say is SOOO important that others should re-arrange their schedules for you!  Trust me, your audience tuned out long ago and is simply waiting for the pain to end.

3.  Don't prepare 75 PowerPoint slides for a 15 minute talk.  It's amazing how often this happens.  There's nothing wrong with PowerPoint, but how do you not know that 5 slides per minute is way too much?  Inevitably, the presenter is on slide 7 after 15 minutes and then plows through the remaining 68 slides in 5 minutes, leaving the audience utterly confused.

4.  Don't present a table or graph in 8 point font.  No one in the front row can see your table, let alone the back row.

5.  Practice your talk ahead of time!!!  It's obvious when the presenter hasn't practiced his or her talk ahead of time.  The speaking is choppy and the presenter has no plan or outline to focus on.

I used to sit through bad talks because I felt bad about leaving the room.  I'd watch others leave and think "that's pretty rude".   However, I've come to the conclusion that if I leave, I'm not the one being rude.  The presenter is the one being rude for wasting my time on utter nonsense.  I wasted my time on a speaker who was unprepared when there was probably another, much better, session that I could have attended.

My daughters are too young to learn the finer points of public speaking, but it's on my list of things to teach them when they are older.

'Africa' Series on the Discovery Channel

If you haven't checked out the recent 'Africa' TV series on the Discovery Channel, please do so.  It is absolutely amazing!  It's a 7 (45 min each) episode series that first aired in January 2013.  The video footage is incredible!

My two favorite pieces of video footage were the giraffes fighting and the baby sea turtles making a mad dash to the sea.  Before watching this series, I had no idea how quickly and violently a giraffe can swing its head and neck.  Awesome video footage!

As for the baby sea turtles, I had no idea how few of them actually survive to adulthood.  They hatch and leave their nests in the sand and make a several hundred yard mad dash across the beach to the ocean.  At only 3 inches long, this is no easy task.  Along the way they must battle predators that swoop down to carry them off to eat.  Yikes!  In the end, only 1 in 1,000 baby sea turtles reach adulthood.  That's a 0.1% survival rate!!!  Incredible!

My 5 year old watched part of the series with me.  She really enjoyed watching some of the animals.  This is probably one of the best documentary mini series that I've watched!  Excellent show.  Definitely check it out!

Myopia and Time Spent Outside

I recently read an article about an interesting study linking myopia (nearsightedness) and time spent outside.  Here's the link to the article:

Myopia and Time Spent Outside

As parents, we are encouraged to read to our kids every day and encourage them to read on their own.  There are several studies that link reading to increased success in school and beyond school.  I find it humorous that because of this, it appears that the rate of myopia in society is quickly increasing!

I also find it interesting that the link between nearsightedness and genetics is not as strong as it was once thought.  I myself am nearsighted.  Both of my parents are nearsighted.  I love to read.  I spent a lot of time indoors reading.  At the same time I lived on a farm and spent a lot of time outside playing.  I played baseball every year as a kid...outside.  Do I have myopia because I didn't spend enough time outside as a kid?  Or was it genetics?  I'll probably never know nor do I really care.  I certainly wouldn't give up reading to spend more time outside!

This makes me wonder about my daughters.  Their eyesight is currently normal for their age.  But will they develop myopia in the future?  Maybe.  My 5 year old loves to read.  She probably spends more time inside than I did as a kid since we live in town and not on a farm where one is more likely to be outside.  Then again, both of their parents are nearsighted.  So who knows?

I guess my point here is to not to worry too much about studies such as this.  They are interesting, but I wouldn't change my life because of it.  It's more important to limit your kids' screen time.  Limit the amount of time they are playing video games and/or watching TV.  Encourage them to use that extra time to play outside or read.

Saturn Book

Last week it was Mercury.  This week it's Saturn.  Pretty soon my 5 year old is going to run out of planet books to bring home from her school's library.  In addition to Mercury and Saturn, she's also brought home a book on Neptune!

Unlike the Mercury book last week, I'm happy to report that I discovered no errors in this book.  

Bouncy Ball Backspin

I experienced a great Daddy moment the other day.  Each of my daughters has her own large bouncy ball.

Several months ago I was playing with both of them, tossing their bouncy ball back and forth.  I would trick them every now and then by putting backspin on the ball so that it bounced back to me, away from them.  They both got a big kick out of this!  After awhile I started putting side spin on the ball so that once it bounced, it quickly moved away from them to the side.  I showed each of them how to do this and they practiced it for a bit.  

Just the other day we were playing with the bouncy ball again and my 5 year old says "remember that time when we spun the ball like this and it bounced away like this?"  Then she proceeded to show me.  It felt good knowing that she retained a bit of physics knowledge I had passed along to her!

Date Night with Your Daughter

I encourage all dads out there to take some time to have the occasional date night with their daughter.  I was thinking about this the other day and came to the realization that the frequency at which my oldest daughter and I have a date night is much greater than that of my youngest daughter.  At least it seems that way.  Some of this is natural simply because my 5 year old was here for 3 years before my 2 year old arrived in this world.  That naturally set up several daddy/daughter date nights.

Earlier this week my wife and 5 year old had a Girl Scouts event after school, leaving me and my 2 year old with an evening to ourselves.  It was at this point I realized that I haven't spent as much time with JUST my 2 year old as I probably should.  It's not that I don't spend time with her.  I spend a lot of time with her, but that time also includes my 5 year old and my wife.  When I realized this, I decided that my 2 year old and I were going out for dinner on a date night.

Date night with your daughter  doesn't have to be anything fancy.  It just needs to be you and your daughter out doing something.  In our case this week, my 2 year old wanted chicken nuggets at McDonald's   Again, nothing fancy, but that's what she wanted, so we went to McDonald's   She wanted me to sit on the same side of the booth as her.  Who was I to argue!?!?!  We had a great dinner together!

To all the dads out there, make sure you're taking advantage of these moments when you can.  It's easy to let them slip by and suddenly your daughter will be fully grown and those opportunities will no longer be there.  Kids, especially daughters, grow up way too fast!

Opening a Cereal Box Correctly

Go ahead and classify this post under silly science, but it's science nonetheless.  If you're a regular reader of this blog, you are aware that I'm a cereal snob.  Both of my daughters are big fans of cereal.  There are at least 5-6 cereal boxes in our house at one time and usually it's much more than that.  Whenever it's my turn to get groceries, you can guarantee that I'm bringing home several boxes/bags of cereal.  Having said that, I've come to realize that I need to sit down with my daughters (and my wife!) and teach them the proper way to open a box of cereal.  The image I took below is NOT the proper way to open a box of cereal.

Notice how the edges of the plastic are all torn and ripped?  Yep, whoever opened this box failed big time!  Why is this a problem?  Well, if the plastic packaging is ripped, the cereal gets caught in the edges of the plastic when it's poured into the bowl.  Then the cereal pieces end up falling outside of the packaging between the plastic and the cardboard box.  In addition, the next time someone pours a bowl of cereal from this box it's inevitable that several pieces will catch the edges of the packaging and shoot off in random directions, missing the bowl and clattering on the counter top and/or floor.  

Here, in the image I took below, is the proper way to open a package of cereal.

Notice how the plastic packaging is not ripped?  This is how you open a package of cereal.  Cereal pieces fall into the bowl without escaping, and no pieces get stuck between the plastic and the cardboard.  I think I need to hold a family meeting to discuss this very serious issue.  :-)

Making an Egg Yolk Float

Several times on this blog I've shared stories of my daughters and I doing density experiments, usually involving salt water.  It's always a test to see what floats and what sinks in water.  We've made whole eggs float and sink, but we've yet to make an egg yolk float and sink...until now!  This is an easy experiment to do and only requires a couple of glasses, a couple of eggs, and salt.

First fill up a glass of regular tap water.  Then fill up a second glass and add 5 tablespoons of salt.  Stir the salt into the water well.  Now crack open an egg and let the yolk fall into each glass.  You should see something like we saw.

The egg yolk sinks in the regular water since it is more dense than the water.  The salt water however has a greater density than the egg yolk, and therefore the egg yolk floats.  Cool!

A Rocking Horse is NOT a Step Stool!!!

Oh dear!  I still have much science to teach my 5 year old.  LOL!  She just returned from a birthday party the other day with a helium filled balloon.  Her and her sister were playing with the balloon when they let go of it and it floated up to the ceiling.  My 5 year old is quite resourceful and decided to take matters into her own hands.  She quickly realized she couldn't reach it by jumping so she went to get something to stand on.  Instead of a stable chair to stand on, she grabs this:

Yes, you're looking at that right.  She grabbed a ROCKING HORSE to stand on to reach her balloon.  I watched this without saying anything to see if she would come to the conclusion that the rocking horse as a step stool was a bad idea.  I waited until she put a foot on the saddle before stopping her and helping her get the balloon.  ROFL!

Mercury Book

My 5 year old continues her weekly trend of bringing one astronomy related book home from her school's library.  This week she brought home a book on Mercury.

All of the planet books she's brought home are from the same series by the same author.  The Mercury book, however, had an error in it.  It states that Mercury is "the second smallest planet in the Solar System". Uh...no it's not.  Mercury is the smallest planet in the Solar System, at least since 2006 when Pluto was changed from a planet to a dwarf planet.  I checked the publication date of the book and it was published in 2008.  There's even a book in this same series on Pluto that focuses on itss non-planet status.  

It's a pretty good planet book series for young kids, so I'll forgive them for this "mistake".  :-)

Meteor Breaks up over Russia - February 15, 2013

Early this morning (February 15, 2013) a meteor estimated to weigh 10 - 11 tons broke up over a city in Russia.  Over 400 people are said to be injured from this event.  The injuries, however, are not the result of pieces of the meteor hitting people.  The meteor broke up several miles above the ground, creating a large shock wave that caused exploding windows/glass.  Most of the injuries are the secondary result of glass shards striking people.  Fortunately no deaths are being reported at this time.

There is also some amazing video footage of the meteor streaking through the sky.  Check it out.

Meteor Breaks up in Sky over Russia

This is an excellent opportunity to explain to your kids that sometimes "rocks" do fall from the sky.  Anytime you see a shooting star in the sky, you are observing a small piece of debris entering Earth's atmosphere.  Most of this debris burns up in the atmosphere and never reaches the ground.  It is being reported that the meteor from this morning did not completely burn up and some pieces did reach the ground.

This is also a good opportunity to explain to your kids the importance of funding asteroid searches so that we know when something is about to hit the Earth.  If we know ahead of time, there might be something we can do to deflect the asteroid before it strikes the Earth.  We know that Earth has been hit by large objects in the past.  We know that these large objects can destroy most life on Earth, including humans.  We also know that we will be hit by a large asteroid in the future.  We just don't know when that will happen.

Important!!!  This meteor is NOT related to the asteroid passing within 17,000 miles of Earth today.  These are two unrelated events.

Life of a Kindergartner

Sometimes I think it would be nice to have a work day where you do the same things that a typical kindergartner would do.  For example, my 5 year old had her 100th day of kindergarten the other day.  To celebrate this, each student in her class had a '100' project to complete.  They had to glue 100 of something to a piece of poster board.  She decided on Cheerio pieces.

How easy and relaxing would a day be if that was your homework?  Ah, who am I kidding.  I'd get bored and need something else to do!

Asteroid - Close Encounter

You may have already heard this, but if not, it is somewhat exciting news.  There is an asteroid, about 150 feet in size, that will pass within about 17,000 miles of the Earth on February 15, 2013.  Now you may be thinking that 17,000 miles is a long distance and it is compared to distances on Earth.  This distance does, after all, take you about 3/4 of the way around the Earth.  However, 17,000 miles is closer than geosynchronous satellites (like your Dish Network or Direct TV satellite).  Here's a link with a few more details.

Asteroid Close Encounter

Yet this satellite analogy still doesn't convey to students how close this asteroid will actually come to passing the Earth.  In the article I linke, Bill Nye relates this distance to a time.  Doing so we find that this asteroid only misses the Earth by 15 minutes!  15 minutes!!!  That's it!!!  I was telling this to my students this week and by relating the closeness in terms of time they finally realized how close this really is.

Even if this asteroid were to hit Earth, it wouldn't destroy all life.  It simply isn't big enough.  It would, however, cause considerably damage.  If it struck a large city, it would pretty much flatten that city.  If it were to hit water, the more likely scenario, it would create a very large tsunami wave that would destroy coastal regions.

Starting a Fire with AA Batteries and a Gum Wrapper

The other day my wife and I were watching an episode of CSI:NY where they started a fire with a battery and a gum wrapper.  Naturally I thought to myself, does that actually work as easily as they showed it on TV?  Once the show ended I ran to the kitchen, grabbed a gum wrapper and 2 AA batteries.  Sure enough, the fire started right away!  Very cool!  My daughters were already in bed, so I was a bit bummed that they didn't get to experience this.  The next afternoon when they were home from school/daycare, we grabbed a couple of batteries and a gum wrapper.

They were both a bit scared when I said we were going to start a fire, but I explained that it would be a small fire and near the sink where we had a bowl of water ready to go.  Above is our video.  As you can see/hear, it was a big hit with my daughters who demanded an encore performance.  Of course I obliged!  

You're starting a fire in this experiment, so obviously be prepared.  Also, be careful using your fingers to hold the gum wrapper to the battery terminals.  The wrapper gets hot very quickly and you can burn yourself.  As long as you're careful, this is an awesome experiment/demo to show your kids!!!

Neptune Book

My 5 year old daughter provided me with another proud Daddy moment the other day.  Her school library has a small astronomy section and every so often she brings home an astronomy related book.  The other day she brought home a book about the Sun.  This past week she brought home a book about Neptune!

Neptune!  Maybe I should be a hand model!!!

The best part is when she came to me and said "Daddy, now we can learn all about Neptune!"  I'm such a happy Daddy right now!

P.S.  Neptune is, as of 2006, no longer the second to last planet in the Solar System.  With the demotion of Pluto to dwarf planet status in 2006, Neptune is the farthest official planet in our Solar System.

Another New #1 Post

The last time (Dec 17, 2012) I commented on the most often viewed blog post, the leader was the Intelligent Life Outside our Solar System post.  Less than a month later, this post has dropped to #4 on the list of most viewed posts.  The #1 spot now belongs to Trouble at the Dentist and the #2 spot belongs to the Thunder/Lightning Misconception.  In fact, Trouble at the Dentist has close to double the number of page views as the Intelligent Life Outside our Solar System post.  A quick Google search of "Trouble at the Dentist" shows that it appears on the first page (at least for awhile) of search results!  Wow!

What is Steam?

There's a big misconception regarding steam, which I've been known to slip on this from time to time.  Steam is the same thing as water vapor and like water vapor, steam is not visible to the naked eye.  So if steam is not visible, then what's that stuff you see floating above a pot of boiling water that we usually all steam?

What you see is water droplets that are the result of water vapor condensing back into a liquid.  As the hot, invisible water vapor rises from the pot, it mixes with cool air.  Energy is transferred from the water vapor to the air, which results in some of the water vapor condensing back into a liquid.  What you see is that liquid.  You're not seeing the actual water vapor or steam.

Step Counter (Pedometer)

Earlier this month I bought a step counter (pedometer) to keep track of my daily steps.  Doctors recommend that everyone have at least 10,000 steps per day to lead a healthy life style.  The pedometer is small and easily slips in my pocket and does a great job counting my steps.  I've learned that there are some days where it's easy to reach 10,000 steps and other days where it is hard.  If it's a day where I teach more classes, I can easily reach 10,000 steps because I'm often walking around the classroom while reaching.

My steps for this day.  Only 752 steps to go!!!

What I really want to do is have both of my daughters wear the step counter for the day to see how many typical steps a 5 year old  and a 2 year old take.  The geek in me finds this very interesting.  I haven't done it yet, because I haven't figured out a way to "attach" the step counter to them without one of the losing it during the day!  At around $20 for this pedometer, it's not super expensive, but I don't want to spend another $20 to replace it if it gets lost.

Making a Duck Call Whistle

Okay, so I'm not sure if this whistle sounds anything like a duck call, but it was fun to make with my daughters.  I found this idea on Science Bob's Experiment site.  The basic idea is to take a few plastic straws, flatten one end, and cut a triangle shape into the end.  Here are our pictures.

Now you blow into the end you just cut.  It may take a bit of practice to figure out where best to put your lips and teeth, but eventually you'll get a sorta duck call sound.  This is harder for kids because their lungs aren't as big and they can't blow out as much air, but my 5 year old was eventually able to get it to work.  After this we experimented a bit by attaching straws to each other.  We ended up making several different sounds.  I'd play the videos for you, but the sounds are very annoying on the video.  You'll just have to try it out for yourself!

Women's Rights and Population Growth

As a father of two young daughters, women's rights is an important issue to me.  I want my daughters to have the exact same, if not better, opportunities that I had and will continue to have.  They shouldn't have to suffer lower pay for the same job or experience fewer advancement opportunities simply because they lack a penis.  I'm ashamed to live in a country that recognizes there is an issue, but who's politicians are unwilling to make changes to support women.  It's even worse in third world countries where women often have no choices.  They are completely controlled by their husbands and lack the right to make their own choices.

Equal rights for women have been shown to increase economic output and lower the rate of population growth.  Here's an interesting article on women's rights and population growth.  It discusses many things, but one thing that sticks out is this.

"An estimated 215 million women in developing countries have an unmet need for family planning: they are sexually active, don’t want to become pregnant, and yet for various reasons—including lack of access—are not using contraception."

 I was recently listening to a talk radio show and the host was interviewing someone on this topic.  Extrapolating the effect of women's rights out several decades finds that if all women had equal rights, the world's population will be 1 billion less in 2050 than it would be if women continue to lack equal rights.  In a world where population growth is a problem, reducing growth by 1 billion people is very significant!

If you have daughters, cousins, nieces, etc., then you should be fighting for equal rights.  Even if you don't have any women in your life, you should fight for equal rights because it is the right thing to do.

Can you get a Moonburn?

Can you get a moonburn?  That's a good question, but first let me explain a moonburn.  I'm assuming that everyone is very familiar with a sunburn.  In fact, you've probably had several sunburns in your life.  A sunburn occurs when your skin is exposed to the Sun for too long of a time.  The UV radiation from the Sun that is not absorbed by the ozone layer reaches your skin and causes damage.  Too much damage and your skin turns red.  More dangerous yet is the deep tissue damage that can occur from overexposure to the Sun. This can lead to skin cancer later on in life.

We see the Moon because sunlight reflects off the surface of the Moon toward the Earth.  The Moon does not produce any of its own light.  Therefore, if what we see when we look at the Moon is reflected sunlight, can you get a moonburn?  The simple answer is no, you cannot.

So why is a moonburn not possible?  The amount of light reflected off the surface of the Moon and received by Earth is MUCH, MUCH less than received directly from the Sun.  The reflected light from the Moon is 500,000 LESS intense than light directly from the Sun.  In addition, the Moon does not reflect UV light as well as visible light, so the amount of UV light reflected off the lunar surface is even less.  There just isn't enough UV light reaching Earth's surface from the Moon to produce a moonburn.

There are many claims of people sleeping outside under a full moon for several hours and waking up with a "burn" on their skin.  This is "burn" is NOT caused by the Moon.  It is NOT a moonburn.  There could be a number of explanations, especially if the person has sensitive skin.  It could be a rash of some kind, but it is certainly NOT a moonburn.

Total Page View

Total page views on this blog jumped from 2,288 in December to 5,260 in January, an increase of 130%!!!  There was a big bump in page views during the first 20 days of January, then things dropped a little closer to normal, although still above December's pace, during the last 10 days.  Not sure why there was such a sudden increase, but sometime's it's better to not ask questions.  :-)

Ring Around the Moon

If you every walk outside and notice a large ring around the Moon in the sky, make sure you take advantage of this observing opportunity.  Grab your kids and show them how cool the Moon looks!  Seeing a ring around the Moon is not very common.  You won't see it every night, and it may be months or years between seeing it.  I've seen this a handful of times over the last two years.

What causes this ring?  The answer is ice crystals.  If the conditions in Earth's atmosphere are right, tiny ice crystals can form in Earth's upper atmosphere.  If there are enough crystals, light passing through (moonlight) refracts and bends, producing a ring like structure, amazing parents and children alike!