How does the James Webb Telescope send pictures to earth from so far away?


Title. Also maybe more extreme, but how is the Mars Rover sending pictures to earth. I cannot grasp how this works over such a long distance.

In: 52

With high powered radio transmitters.

The same way you can use your car radio to tune into a radio stations miles and miles away.

Big radio receivers here on earth can pick up the signals that those space craft are sending out.

The mars Rovers can be a bit more complex, since this radio communication needs a direct “line of sight” so if earth is on one side of arms, and the rover is on the other side of mars, then mars itself blocks our radio signal. So the rovers will first send their signal up to a satellite orbiting mars, and then that satellite will pass the information back along to us.

Radio waves, for all intents and purposes, travel infinitely in space. If you think getting signals from Mars is impressive, look into the Voyager probes. Voyager 1 is 14 billion miles away (150 times farther than Mars) and we still get signals.

One thing that helps with these extremely long distance communications is that we know exactly where the signal is coming from. We even know the math to adjust for the time it takes for that signal to travel the long distances between there and Earth. So we can point a transmitter and receiver exactly where it needs to be in order to send/receive signals. Some averaging helps even out background noise, allowing us to see signals even if the received power is below the noise level.

The same way you can see Mars from Earth. Radio waves act just like visible light, both being a part of the electromagnetic spectrum. You get a wave in the spectrum with enough energy to escape the atmosphere, and you’ve got yourself a wave that will continue on until it hits something that stops it. And as long as you can recover enough of that energy at the other end to be able to tell what it originally was, you’ve got yourself a radio message (or a visible planet).

Light shows us what things look like by using different wavelengths which our brain interprets as colors. Radio waves, depending on the method used, do much the same thing by either varying the frequency (and therefore the wavelength) or phase (voltage) of the wave. You don’t need the whole radio wave to receive the message on the other end, just enough to distinguish between the frequency or phase differences. Sure, they take bit more power than your wifi uses, but it’s the same concept.

Radio signals are just a form of light that we can’t see. Light in a ~vacuum travels at the speed of light (obviously). Distance affects signal quality and how much data you can transmit but when traveling at relativistic speeds (ie the speed of light) the distance we are transmitting and receiving from isn’t really that crazy especially with nothing like air or water in the way to diffuse the signal.