The Quick and Dirty

via jitze/Flickr

by Math Dude

Have you ever needed to convert from miles to kilometers or vice versa? Perhaps you’re from the US and you were traveling in Europe. Or maybe you use kilometers at home and you were traveling in the US. Either way, it can be confusing. But the good news is that it’s easy to do the unit conversion in your head…and this post contains everything you need to know.

To convert distances in miles into distances in kilometers (or speeds in miles per hour into speeds in kilometers per hour), simply multiply the number of miles by 1.6 (which, completely coincidentally, turns out to be close to the value of the golden ratio that comes from the Fibonacci sequence):

(distance in kilometers) ≈ 1.6 * (distance in miles) Continue reading ‘How To Convert From Miles to Kilometers’

via juggernautco/Flickr

by Math Dude

Have you ever watched a football game and wondered exactly how fast a wide receiver is running towards the end zone? Are players jetting down the field at 5 mph, 10 mph, maybe 20 mph, or even faster?

In honor of the start of the NFL season, today’s post is aimed at teaching you an easy method that you can use to answer this question for yourself…and for all your friends at game day parties too. There’s a longer Math Dude article on this topic, so if you want to know all the details, be sure to check that out.

The first thing to know is that speed (which is typically measured in miles per hour in the US) is just a measure of the total distance travelled divided by the time it takes to cover that distance. So 30 miles per hour means that if you move at 30 miles per hour for 1 hour, you’ll travel 30 miles. Easy!

Continue reading ‘How Fast is That Wide Receiver Running?’

"Heart Nebula" (photo from Hewholooks at en.wikipedia)

by Math Dude

In the last post, we used a bit of simple unit conversion math to figure out roughly how many heartbeats there are in a typical human lifetime. (If you haven’t read it, you should check it out before moving on.) Toward the end of the post, I posed the question:

How does the number of beats in a human lifetime compare to the number of beats in the lifetime of something like a honeybee? Or a cat? Or a whale?

As luck would have it, a few weeks ago I stumbled upon a blog post by Caltech professor Sean Carroll about Ten Things Everyone Should Know About Time. And down there at number ten on his list under the heading “A lifespan is a billion heartbeats,” I found something pretty amazing. Sean writes:

…there exist simple scaling laws relating animal metabolism to body mass. Larger animals live longer; but they also metabolize slower, as manifested in slower heart rates. These effects cancel out, so that animals from shrews to blue whales have lifespans with just about equal number of heartbeats — about one and a half billion, if you simply must be precise. In that very real sense, all animal species experience “the same amount of time.”

Continue reading ‘How Many Heartbeats in a Lifetime? (Part 2)’

"Heart Nebula" (photo from Hewholooks at en.wikipedia)

by Math Dude

If I’m lucky, I might live to be 90 years old. If I’m really lucky, I might even make it to 100. My wife firmly insists that she’s going to live to 110…and I don’t doubt her.

If you think about it, these numbers are rather amazing. After all, we’re lucky if our cars, appliances, and other things with moving parts last a decade. But the human body—and in particular the human heart—keeps ticking away for nearly a century. It’s quite a well-functioning piece of machinery!

Which makes me wonder: If I live 100 years, how many times will my heart beat?

Well, depending upon how fit a person is, the typical human heart at rest will beat between 60 and 90 times per minute (hopefully toward the lower end of that range). Which, as we learned in the Math Dude article on converting units, means that my 100 year (fingers crossed!) lifetime will include:

Continue reading ‘How Many Heartbeats in a Lifetime? (Part 1)’

Photo by Jason Marshall

by Math Dude

On a recent trip up the California and Oregon coasts, I was lucky enough to walk amongst some of the most ancient and gargantuan living organisms: coast redwoods (aka sequoia sempervirens). And when I say ancient and gargantuan, I mean it. Coast redwoods live from 1,000 to 2,000 years (or maybe even more) and are the tallest living things on the planet.

Exactly how tall? Well, the largest specimen, known as Hyperion, rises to 379.3 feet. Just to give a bit of perspective: 379.3 feet is a little over 126 yards. Which means that this tree is a few yards longer than an American football field measured from the back of one end zone to the other.

So yeah, this tree is really Really REALLY tall. Where is it?

Continue reading ‘How Tall is the Tallest Tree on Earth?’