TWL #5: Timekeeping on Mars | Wendover Productions

0:00So, there's this fantastic Wikipedia list, descriptively titled Wikipedia colon unusual articles. I just remember it as that Wikipedia list. It's a collection of hundreds of articles about unusual, unexpected, and unbelievable subjects. No matter what link you click, it's bound to be interesting. For that reason, every week I'm going to click on a new link and teach you a little bit more about our amazing world. Today, we're going to take a trip. We're going to slip the surly bonds of earth up into the heavens. We're traveling through the galaxy to learn about timekeeping on the red planet, Mars. But before we can understand timekeeping on Mars, we first have to understand timekeeping on Earth. Damn it. Can we turn this thing around? All right, so this is the Greenwich Observatory in England. Greenwich is known for being the site of the prime meridian. For all intents and purposes, this is the longitudinal center of Earth. For simplicity's sake, we'll say that time is determined based on the sun.

1:02This isn't exactly true though, so I have a whole other video that explains time in more detail. When the sun is highest in the sky at any given location, we call that noon, and the rest of the day's time is relative to this. So now let's go south to the intersection between the equator and the prime meridian. We find ourselves in the middle of the Gulf of Guinea. Similar to how the prime meridian is the longitudinal center of the Earth, the equator is the latitudinal center of the Earth. At this point of zero degrees longitude and zero degrees latitude, it's noon, because the sun is at its highest point in the sky. Great. Now if we go 1,035 miles east, we find ourselves in the lovely village of Atumbi in the Republic of Congo. In Atumbi, the time is 1 pm because the sun reaches highest point an hour ago. This is why we have time zones, since the Earth rotates once every 24 hours, there are 24 time zones. But wait, I lied. It doesn't take 24 hours for the Earth to rotate once, it takes 23 hours, 56 minutes, and 4.0916 seconds.

2:02That's because there are really two definitions of a day. The conventional definition is a solar day, the time between two moons when the sun is highest in the sky. The more scientific definition is a side-deerial day. That's the time it takes for the Earth to rotate 360 degrees around its axis, and therefore the time it takes for the same star to appear in the same spot in the sky from one day to the next. There's a difference between side-deerial days and solar days because the Earth rotates both on its axis and around the sun. So watch this. Let's put a marker on a spot on the Earth and fast-forward one side-deerial day. You'll notice that the same spot is not yet the closest point on Earth to the sun, because the Earth also rotates around the sun. To bring the marker closest to the sun, we'll need to advance four minutes forward and now we're at one solar day. Those four minutes add up conveniently to just about 24 hours over one year, so that means that there's one more side-deerial day per year than solar day. Alright, now we can go to Mars. That was quick. So Mars is a pretty similar planet to Earth and time works in a pretty similar way.

3:06It has a primaridian right here. Strangely, astronomers chose this primaridian before Earth was chosen. Using the mean solar time at the primaridian, there's a coordinated Martian time known as MTC, but for the most part, any rovers on Mars just set their clocks using the solar time of their landing site. This is actually pretty similar to how towns on Earth set their time before coordinated time zones were created. Each town on Earth set their time based on their own solar new, but this created difficulties when rapid transit between places was invented since no one really knew what time it was. If you want to learn more about this, you can once again go check out my other video on time. Since there have only ever been eleven operational spacecrafts on Mars, having different time standards based on solar time hasn't yet caused any problems. It does mean, however, that even the seconds aren't coordinated between different rovers. What does cause a bit of a problem, though, is that a Martian day is slightly longer than an Earth day. Anyone who's watched the Martian knows that a solar day on Mars is called a soul.

4:10One soul is equal to 24 hours, 39 minutes, and 35.244 seconds. Rovers on Mars generally only work during the day, partially because some are solar powered and partially because much of the work is based on observation from cameras which need light. Therefore, the teams on Earth controlling rovers have to live their lives based on Martian time. Their work shift essentially moves forward 40 minutes every day to coordinate with the time that it's light on Mars. Jebra Bass, a scientist from the Jet Propulsion Laboratory who worked in the spirit and opportunity programs, said that, you're always jet lagged. It's only a little bit, because an hour, who cares, that's also bad. But it starts to take a toll. Scientists who work on rovers sometimes wear two watches, one for Martian time and one for Earth time. So, if we do go colonize Mars, we'll want to create time zones and actually use the standardized time. Having different time standards at different places always creates problems, especially for computers and communications.

5:10This, of course, is just one of many details that we'll have to figure out before we go live on the red planet. I hope you enjoyed this week's episode. It was far more educational than last week's episode about toilet paper orientation, which you can find right here. You can also subscribe to this channel by clicking here. Also, before you go, this is my formal plea for you guys to go follow me on Twitter. I have 13 followers, and while those 13 seem like really cool guys, I would love to have more people to talk to. My username is AtWendoverPro. Thanks for watching, and come back next week for more of that Wikipedia list.