Obviously the pics aren't floating around, but how can I explain this to a 10 year old?
A correct analogy would be:
- There is an image at some location.
- Someone is here and talks to someone else at a distance.
- The first person announces the color of each pixel, one by one.
- The second person, who hears the first one, draws each pixel according to the announcements.
- The sound of the voice takes time to travel, the further, the longer (this can be demonstrated easily by clapping hands at 100 yards).
- At the end there are two exact copies, albeit no image has traveled.
- For the spacecraft, the two persons and the voice are replaced by modulation and demodulation of a radio wave, which really allows to transmit information at very long distances.
You may also explain it takes time to announce all pixels; the two persons must know beforehand how to organize the pixels (image size); the names for all colors must be defined; etc.
You may also experiment Morse code with a torch light to simulate how information can be shared at distance. You can replace light by dots on a ball to simulate slow travel of the carrier... this is endless when the analogy is correct (no image is moving).
To understand the details of how an image is transmitted in practical, how long it takes and why images are not systematically transmitted in real time, you may read this other answer: How are New Horizons images sent back to Earth?
Spacecraft that take pictures take them similar to a digital camera. However, the camera is very far away. Similar to downloading a movie off of a website so you can watch it on your local device, it takes time to transmit those images. However, because the distance is so far away, it can take a lot of time to download the images.
The images reside on a memory card, similar to the memory card that a digital camera has, and stay on there until deleted. They are deleted only when someone from Earth confirms the image was downloaded correctly.
(10 year old version)
The pictures are sent by radio, and the radio signals travel at the speed of light. Although the speed of light is very fast, it is not unlimited, and space probes can be very far away. So the time that elapses is simply the time it takes for the radio waves to travel at the speed of light over the very long distances between the probe and Earth.
(there is also a low data rate factor, but I am not sure if this what you are asking about)
Radio waves are such an abstract concept that it might be useful to explain to a child using an analogy of concrete objects. In a real way, picture information contained in a radio transmission could just as well be a string of baseballs thrown at high velocity, where the patterns or aiming of the throws enable reconstructing the picture at the other end. If the baseballs have to transit a very long distance, all of them in flight together "are" the picture--representing it faithfully.
Further analogy to aid comprehension is possible. For example, explain how the signal being digital enables clear transmission even if any baseball gets slightly off course and arrives early or late or slightly to the side. Each baseball has a box in which it should arrive (both in space and time), which means that you can still tell what its target was.
This could help them conceptualize how flying objects can result in assembling a picture at the other end.
I am sure your 10 year old can "see" & "experience" how Cell Phones & Remote Controls work. Not see the invisible waves, but the can see the effect of 'doing' X and seeing a response on another device.
My sisters 2 year old uses remote controls with full awareness to turn on A/Cs, TV etc. They know it works, just not sure what's the underlying mechanism.
Easiest illustration would be to send take a few wireless devices and send pictures between them e.g. Take a Picture/ Photos from one Phone/ Tablet to another in front of your kid. Take some pictures and send again.
Ask him whether he knows how it works? Explain how invisible special waves act as a link to send it across.
To establish further how a link is formed:
Use 2 wireless devices for a voice transmit - Cordless Phones, Cell Phones, Baby Monitor
To show a visible link you can do the 2 Matchboxes + 1 taut string thingy we've done as kids and see how sounds can transmit over a visible medium.
These illustrations will establish foundation for how communication and transfer of information over visible as well as wireless & invisible links. So even though not visible it works.
You can choose the order of the above illustrations that work best for you & your kid.
Then use a, a visual depiction like the above answer would be much easier than explaining verbally. The right picture, animation or video would be worth more than all the words in the above answers; albeit if you can find a visual way to represent the above answer - you're good to go.
Google Search: Satellite (Communication OR Transmission)
Examples of search results vary from simple diagrams to complex ones. Choose the ones you feel can be most clearly representative.
The best way to explain it: 1. Understand it completely yourself 2. Give short and precise answers. 3. Encourage your kid to ask follow up questions to clarify and expand the answers. 4. If you get stuck, sit down with him on the computer and google it. And then break down the answers for him if they are too technical/complex.
If a kid asks a question, you are not really supposed to prepare a whole lecture that covers everything. Just talk to him and see what he already knows and what is missing to get the whole picture.
If he askes questions like that, he is also probably smarter than you expect in some regards. If you lecture him, he will just get bored if you are simplifying too much.