## Monday, February 29, 2016

### Leap Years and How Scientists Tell Time

I couldn't let Feb. 29th go by without commenting on leap years, especially since I have no expectation that this blog will still be around four years from now. Leap years originate in astronomy -- the length of the year (the time it takes the Earth to go around the sun), is not an even number of days (the time it takes the earth to rotate on its axis). The length of the year is roughly 365.2422 days. Lucky for us, the fractional part of the year (0.2422) is almost equal to 0.25 (or 1/4), so we can fix things by adding 1/4 of a day every year, or one day every four years. This "fix" was introduced by the ancient Romans, and it works pretty well, but it's still not perfect. The Gregorian calendar fixes the fix by taking away leap days every 100 years (so, for instance 1800 and 1900 were not leap years) and then adding them back in every 400 years, so 2000 was a leap year. Our leap year in 2000 is something we won't see again until 2400! This gives us a length of the year equal to 365 + 1/4 - 1/100 + 1/400 = 365.2425 days, which means the calendar will be off by one day every 3333 years -- not too shabby!

Calendar reform had a symbiotic relationship with the infant science of astronomy. It's really just a weird coincidence that a simple leap year works so well, but not well enough that it didn't need to be fixed later on. Would science have developed any differently if the year were more exactly a simple fraction of the number of days, so that the Gregorian reform had not been necessary? And what if the opposite had been true? What if the year weren't anywhere close to a simple fraction of the number of days? Would that have led to much greater calendrical confusion over the centuries?

Given all of this confusion, what unit of time do scientists use in their own work?  Days? Years? Hours? Minutes? The answer is none of the above.

## Friday, February 26, 2016

### The Flat Universe Society

In my peregrinations around the Internet, I have discovered not one, but two websites devoted to the Flat Earth Society:

www.theflatearthsociety.org
and
www.tfes.org

I think one is a splinter group from the other. I bet they hate each other.

But why limit ourselves to a binary choice? Why does the alternative to a round Earth have to be a flat Earth? Let's be creative and think of other possibilities.

Maybe the Earth is actually shaped like a torus (a gigantic donut):

This is even better than a sphere -- now there are two different ways to go around the world! You can sail around the outside of the donut, or you can circle the world through the donut hole.

Or maybe the surface of the Earth has negative curvature, like a saddle or a Pringles potato chip:

Of course, this isn't what the Earth looks like. But it's what the entire universe might look like.

## Tuesday, February 23, 2016

### Gravitational Radiation and the Search for Extraterrestrial Intelligence

With the first direct detection of gravitational radiation by LIGO, we've entered a new era in science. Gravitational wave astronomy promises to be the most exciting field in the physical sciences for the next decade. So should we start looking for signals from ET in this data?

## Wednesday, February 10, 2016

### First Detection of Gravitational Radiation?

It's totally irresponsible for scientists to spread rumors on the Internet, so I will wait until after the break to do so.

## Tuesday, February 2, 2016

### Dell Award for Undergraduate Science Fiction Writing

This past fall marked the third time that Professor Jay Clayton and I taught our Vanderbilt seminar on science and science fiction. As a final exercise, the students usually choose to write their own short stories. (They also have the option of writing a "popular science" article or a critical essay, but only one student has chosen this in the entire history of the class!) We've always entered the best of the students' stories in the competition for the Dell Award for undergraduate science fiction writing. This year, our students took first place and third place in the competition!