I gave a teleclass on the biggest *oops!* found in science textbooks, and in addition to the teleclass recording, I thought you’d enjoy an excerpt from my notes. If you’ve found one or more of these in your books, it’s not the end of the world… but this may raise your awareness a few notches.
This article will outline the basic fundamental concepts in physics and give you real hands-on experiments you can share with your child that they will love. I’ve been teaching physics from grade school through college, and in this article I am going to address the common myths and misconceptions about physics and help you set the record straight.
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Great question! And don’t hesitate to pelt me with all your questions – that’s what we are here for!
Yes, satellites do need power to stay in orbit, but most of this power comes from the initial launch of the rocket that put the satellite in orbit.
There’s not as much atmosphere in orbit so the satellite doesn’t experience the same amount of drag when orbiting the earth as it would on the surface, so it takes longer for a satellite to ‘slow down’. Their orbits do decay over time (although there are fewer particles to hit in orbit, it does still happen), and recently we had to ‘bump’ the Hubble telescope satellite back into its original orbit or it would have crashed back onto the earth in 2012. It’s a balance of forces between the gravitational pull and the force created by moving in a circle and the drag force from particles in its path.
Does that help?
The earth curves about 16 feet down for every 26,000 feet along the horizon. For a satellite to orbit the earth, it needs to go 26,000 feet horizontally before it falls 16 feet down, which gives an initial speed of 26,000 feet per second (about 5 miles per second). When you launch the satellite at this speed, it will fall toward the earth at the same rate that the earth is curving away. If a satellite goes too fast, it will overcome the gravitational pull of the earth and shoot out of orbit.
We understand the principle of orbiting – but with the satellite falling out of orbit and your explanation that satellites need to go fast enough to stay ahead of the earths curve – are they powered by an energy source? Or are they naturally moving forward simply by being sent to a specific height? Why do they fall out of orbit?
I am teaching this to my science class and don’t have a clear answer for this. Thanks for helping us understand.
Great question! Satellites typically move about 5 miles per second in low earth orbit in order to keep from falling back to the earth.
When we launch rockets from the surface of the earth, we aim them vertically at first, but after launch the rocket shifts its vertical motion to be primarily horizontal (parallel to the surface) motion by the time it reaches orbit altitude. Just like when you toss a ball in the air and it comes back to you, objects within the influence of the earth’s gravitation will also move toward the center of the earth if left on their own. That’s why we swing things around the earth – to keep them in orbit! (Think of swinging a bag of oranges around your head – there’s a pull you feel on the bag the faster you swing the oranges around. This is the force that balances out the gravitational pull and keeps the satellite in orbit. You can do this experiment here.)
We are having trouble with Satellites and orbiting. The moon orbits the earth but is not moving forward at the same time (bullet example). So does the Satellite need to be moving forward fast enough to keep ahead of the earths curve? If it stops moving forward will it fall into earth?
Hello, I appreciate that explanation you gave the other lady. Thank you for all the info too! I recently spoke to my children about other deceptions(or mistakes), that are going on in history books/ Bible, etc…. I encouraged them to seek truth, especially through their faith and JESUS relationship, and not get discouraged at the mix-up, mess-ups. I expect to let them see this and talk with them about it. Very, very interesting.
You’re right Deanna, it’s a hard one to visualize at first, but here’s something you can consider… if the satellites DON’T move in orbit, then there’s nothing to keep them up there and the gravity from the earth would pull them back to crash on the surface. The trick is that the satellites need to move at a rate that allows them to constantly ‘fall’ to the earth at the same rate the earth’s surface is curving away from the satellite (because the earth is round). Just as a bullet can travel fast enough so that the rate it falls to the ground matches the rate that the earth curves away from it. the satellite falls to the earth as the earth moves out of the way, so to speak. Does that help?
Hi Aurora: My son and I were wondering if you could explain a bit more about the misconcept that:
“Satellites don’t move in orbit.” I didn’t think they did but conversations we are having with others has been very interesting. Most people say “Of course they do!” Brain Pop which is a great resource- just indicated the same misconcept to its subscribers. Can you explain it a bit more in lay men’s terms– so it will be easier to explain it to others that tend to “argue” the fact with us? I have reread your explanation but it just is not sinking into my mind. So if I understand this concept correctly– they do move but just fast enough to keep it in orbit but not enough to officially say they they are moving in orbit? Is this correct? Any help would be much appreciated. Thanks. Deanna