I enjoy relaxing and watching the darkness of night extinguish the distractions of daytime, as the tranquil beauty of the silent stars appears. We’re used to those stars holding still, but at times it looks like some are moving.
Those movements aren’t unusual and neither are they stars. If a point of light is moving fast and lasts only a few seconds at the most, it’s probably a meteor, a stone from outer space. A lot of the lights are moving slowly enough to take about five minutes to cross most of the sky. These are usually airplanes and satellites. If the moving light has blinking lights, or is coming from the east, it’s probably an airplane. If not, it’s probably a satellite.
Here’s why satellites don’t come from the east. The Earth rotates toward the east at about 1,000 miles per hour (1600 km/h) at the equator. Satellites are usually launched from a place close to the equator and toward the east to take advantage of that huge speed boost. It’s a simple technique that makes not-so-simple rocket science a little easier.
The basics of launching a satellite are easy to comprehend but hard to carry out. All a rocket scientist needs to do is use a rocket to essentially throw a satellite above the air and sideways at just the right speed that, as the satellite falls, its curved path downward perfectly matches the curve of the Earth. That speed for low Earth orbit is a little over 17,000 miles per hour. The satellites you see gliding across the sky at night are actually in a freefall arc curving downward and blitzing through space at about five miles per second.
The brightest artificial satellite you can see is the International Space Station. It usually has at least three people on board. They’re freefalling too, so they feel weightless. But it’s not because they’ve escaped gravity. Gravity has complete control of them and is plunging them downward. Since they’ve yielded to gravity, they can’t feel its effects. They no longer have to resist gravity like we do when we stand up on the Earth.
All satellites are in space, but just barely; a lot of them are only 200–300 miles up, about 1,000 times closer than the Moon. So, they are nowhere close to the stars. The closest star is about 100 billion times farther away.
There are more than 6,000 functioning satellites in orbit. SpaceX is a company that intends to launch a total of 42,000 satellites for internet service. Every satellite must be tracked to avoid collisions.
Sometimes collisions are unavoidable though. In 2009, two satellites designed for relaying communications to and from Earth were definitely not communicating with each other when they collided while moving at over 16,000 miles per hour. Both shattered. In 2007, the Chinese military experimented with shooting a weather satellite; it exploded too. Now instead of tracking that one satellite, there are more than 3,000 pieces that need to be tracked.
A satellite that appears to be dimming and brightening on a regular cycle is a sure sign of junk that’s spinning out of control. Most satellites are pieces of left-over space junk like old rocket bodies.
There are so many satellites crisscrossing the sky that it’s almost impossible to get a long exposure, deep space photograph without having satellite trails sweeping through the photos. Thankfully, computer software can be used to subtract the trails.
The satellites are too far away and tiny for us to resolve, yet they shine clearly. It is because they reflect a great deal of the Sun’s brilliant light. We don’t usually think of it, but beyond the blackness of the night sky, sunlight is streaming in full force, just a few hundred miles above us. The satellites catch the light and reflect some of it down to Earth.
You normally don’t have to wait more than a few minutes to see a satellite after sunset or before dawn. In the future, there will be many more, and they’ll be considered much more of a nuisance than they are now.
Thankfully, there’ll still be a respite from the distracting artificial lights. As the night goes on, Earth’s shadow rises higher in the sky. The satellites pass into it and go dark. In the chaotic space junk traffic jam of the near future, midnight will extinguish the glaring satellites to preserve the tranquil beauty of the silent stars.
