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Saturday Morning in Boulder: Does The Sun REALLY Rise? NO! Not Really!

Each morning in Boulder the sun rises. We know what time that will happen. We know what time dawn (before sunrise) will happen. We can expect the sun to rise at specific precise times. But does it really “rise?” Of course not! If it did, this blog would be finished already. Have I totally lost it saying “the sun does not rise at all?” Probably, but that is not news!

When we are looking from the earth, the sun appears to rise as expected. But what if we’re watching from the International Space Station? What if we’re watching from a jet? Do we see the same thing? Of course not!  From the ISS, International Space Station, we’d see a line of light overtaking the darkness we call “night” moving from East to West.

The lit-up part of the Earth changes, we know. As the sun “rises” around the globe, it does not rise at the same time everywhere. We could fly in a jet, circling the globe, and follow the line of light we call sunrise, around the globe. We’d have to circle the Earth, about 25,000 miles, 37,000 kilometers, in 24 hours. We’d see that there is no “sunrise,” but that there is a moving portion of Earth that is lit up by the sun, and the other half which is in the dark of night, facing away from the sun.

FYI the space station circles the Earth every 90 minutes! It is FAST! The astronauts see 16 “sunrises” in 24 hours. Did the sun really rise 16 times in one day? Yes and no! It depends.

That is caused by the Earth traveling around the sun once each 24 hours so we have a sunrise every 24 hours or so. But does the Earth really travel around the sun? It depends! It depends upon where you are standing or flying. If we are flying around the earth, East to West, over the equator, we can follow this moving “sunrise” at the right speed so that it appears to hold still while the Earth turns under us. To travel 40,000 kilometers, 25,000 miles for one trip around the Earth, in 24 hours, to follow the “sunrise” around the Earth, we have to fly at about 1000 miles an hour, 1600 kilometers per hour. That’s only about two to three times faster than a regular commercial airline flies. Our f-16 jet can fly at 1300 miles per hour, 2100 kilometers per hour. In other words, fast, but not all THAT fast! An F-16 air force jet can travel faster than the line of the apparent sunrise travels around the earth. We could follow the “line of the sunrise” around the earth if we had enough jet fuel.

So is the sun rising, or is the sun holding still as the earth spins on its own axis? Easy! Both! As they say “it is all relative.” Depending upon where you are standing, things appear to move differently. So what is really happening? All of it is happening, and at the same time. What changes is our point of view. What changes is where we are standing when the illusion of sunrise is viewed. From the Earth, it is quite real, and the sun rises as expected. But if we are looking from the sun, we see the earth spinning on its axis as it slowly travels in its orbit around the sun. But is it really orbiting around the sun? NO it is not! It just appears that way if we look “down” on the sun and watch the Earth slowly travel around the around the sun. As the Earth spins, the sun lights the Earth, with the lit side always changing. That makes it appear from the Earth like the sun is rising. So what is true? Does the sun rise or doesn’t it? Easy. Both are true! We first pick the spot we are watching from. THEN we can describe what we see. We pick our POV point of view depending on what we want to know. If we are interested in the time of “sunrise,” we can look out the window, look at our phone, and see what time the sun breaks the horizon, starting to light the day. We can predict with great precision just when that will happen each day. That is fine for some purposes. For other questions, we must change our POV.

We see here one side of the Earth is daytime, lit by the sun, while the other side is night, away from the sun so it is not lit up. If we are flying from West to East, we would see more sunrises and not just one sunrise per day that we see from the Earth. That would shorten our work week. So if we were on the space station, and if we were flying West to East, our days would be shorter. AND our nights would be shorter. Bad for sleep, good for making the work day shorter.

As I said, “it depends!” Happy Saturday! Or is it really still Friday?? It depends!

Lenny Lensworth Frieling

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