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 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 travelling 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
Dammit, ughh, can we.. can we turn this thing around? Alright, 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. This isn't exactly true though, so I have whole another video that explainstime 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 0° Longitude and 0° Latitude, it's noon, because the Sun is at it's highest point in the sky. Great, now if we go 1,035 miles east we find ourselves in the lovely village of Etoumbi, in the Republic of the Congo. In Etoumbi, the time is 1PM, because the Sun reached it's 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, That's because there are really 2 definitions of a day.
The conventional definition is a Solar Day. The time between two noons when the Sun is highest in the sky. The more scientific definition is a Sidereal Day. That's the time it takes for the Earth to rotate 360° around it's 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 Sidereal Days and Solar Days because the Earth both on it's axis and around the Sun. So, watch this. Let's put a marker on a spot on the Earth and fast forward one sidereal day. You'll notice that the same spot is not yet the closest point on Earth to the Sun because the Earth also rotated around the Sun. To bring the marker closest to the Sun, we'll need to advance 4 minutes forward, and now we're at one Solar Day.
Those 4 minutes add up conveniently to just about 24 hours over one year. So that means there's one more Sidereal 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. It has a prime meridian right... here. Strangely, astronomers chose this prime meridian before Earth's was chosen. Using the mean solar time at the prime meridian, 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 settheir time before coordinated time zones were created. Each town on Earth set their time based on their own solar noon. 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 11 operational space crafts 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 Sol.
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. Deborah Bass, a scientist from the Jet Propulsion Laboratory who worked on the Spirit and Opportunity programs, said that Scientists who work on rovers sometimes wear two watches, one for Martian time and one for Earth time.
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