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Obviously the pics aren't floating around, but how can I explain this to a 10 year old?

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    $\begingroup$ Is this in relation to a specific mission? $\endgroup$ – PearsonArtPhoto Aug 10 '15 at 18:02
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    $\begingroup$ The "picture" is radio frequency light waves blasting through space. Basically, you could say they are floating around. $\endgroup$ – Broots Waymb Aug 10 '15 at 20:33
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    $\begingroup$ @DangerZone I doubt the probe clears its memory until it knows the data is received. Can't you explain it like "it's in the post and will be here soon" $\endgroup$ – Alec Teal Aug 10 '15 at 23:39
  • $\begingroup$ @AlecTeal, I don't think that really works either unless you can also explain that there is a copy in post and at the source as well (this almost never happens..). So you'd have to explain it as 2 copies. Like taking a picture with a camera. The copy on the camera (picture on probe/lander/whatever), and then physically mailing a copy to a friend (the waves in space) $\endgroup$ – Broots Waymb Aug 11 '15 at 13:33
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A correct analogy would be:

  1. There is an image at some location.
  2. Someone is here and talks to someone else at a distance.
  3. The first person announces the color of each pixel, one by one.
  4. The second person, who hears the first one, draws each pixel according to the announcements.
  5. The sound of the voice takes time to travel, the further, the longer (this can be demonstrated easily by clapping hands at 100 yards).
  6. At the end there are two exact copies, albeit no image has traveled.
  7. 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?

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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.

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    $\begingroup$ +1 For taking into account on-board storage until confirmed delivery. $\endgroup$ – called2voyage Aug 10 '15 at 18:11
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(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)

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    $\begingroup$ Depending on how advanced the 10 year old is, some basic philosophy may also be in order. I.e. Is it really a picture until it is displayed in a viewable format? The camera records the light hitting it as digital information. This digital information is stored in memory and then transmitted via radio signals to Earth. Once received it is stored as digital information in Earth computers and only becomes a picture when that information is interpreted by software to screen output or a printer. But this may be more technical an explanation than desired. At 10 I could understand this in plain lang. $\endgroup$ – called2voyage Aug 10 '15 at 18:15
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    $\begingroup$ @called2voyage: I always found these "philosophical" questions to be extremely irritating and, in my eyes, indicating that the person asking them is somewhat of a nutjob. I did so at the age of 10, I did so at the university talking to "real" philosophy students, and I still do so over twenty years later. No offense intended to you, but I wouldn't encourage confusing kids with this stuff -- they usually have a good instinctive grasp of a "picture" being a computer file one moment and a piece of paper with color on it the next. $\endgroup$ – DevSolar Aug 11 '15 at 10:58
  • $\begingroup$ @DevSolar You may disdain philosophy, but what you described is also philosophy. In this instance you are defining a picture as the information and identifying that the information can change states from a computer file to colors on a piece of paper. I would highly encourage teaching 10 and up philosophy because examples like this are especially pertinent to life. How we define and interpret things in discourse affects what we perceive to be true. $\endgroup$ – called2voyage Aug 11 '15 at 13:32
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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.

If the child still doesn't understand, show them a bean bag toss tic tac toe game: Bean bag toss tic tac toe

This could help them conceptualize how flying objects can result in assembling a picture at the other end.

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    $\begingroup$ This is probably the best and simplest explanation, though not for a ten year old. I'd use this brilliant analogy to describe radio communication to kids under six. $\endgroup$ – Vedant Chandra Aug 11 '15 at 16:01
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I really can't add much to the already excellent answers but as seen as this is for a 10 year old the following picture from wikipedia may help explain the concept. It shows a pulse of light travelling at the finite speed mentioned in the other answers.

Diagram of a light pulse travelling from the earth to the moon

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  • $\begingroup$ @mins I am confused by your comment, I am not asking for clarification nor am I critiquing certainly not consciously. I answered with this image as the question specifically asks how to explain the concept to a 10 year old and visual representations of concepts are often easier to understand especially at a younger age. $\endgroup$ – o.comp Aug 12 '15 at 12:08
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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)

https://www.google.com/search?biw=1350&bih=861&tbm=isch&sa=1&q=satellite+%28communication+OR+transmission%29&oq=satellite+%28communication+OR+transmission

Examples of search results vary from simple diagrams to complex ones. Choose the ones you feel can be most clearly representative.

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  • $\begingroup$ @Heike - An illustration and visual stuff will always work better than a verbal explanation. $\endgroup$ – Alex S Aug 11 '15 at 15:28
  • $\begingroup$ I think this answer, while generally correct, may miss a lot of the point, which is the transmission time. From Pluto, New Horizons has a latency of four and a half hours -- where are the pictures during those four hours? $\endgroup$ – Nathan Tuggy Aug 11 '15 at 15:40
  • $\begingroup$ @NathanTuggy - Its a 10 year old, baby steps. The term is latency - If he wishes for his kid to understand that, I will add something to illustrate that as well. Please comment as I cant and ask him if he wants that. PS: To answer his question - its in the air / space in transit. $\endgroup$ – Alex S Aug 11 '15 at 17:52
  • $\begingroup$ I don't really expect the term latency to come up, but the general concept (the lapse in time between sending and receiving) seems to already be part of the question. $\endgroup$ – Nathan Tuggy Aug 11 '15 at 17:59
  • $\begingroup$ I like this answer; if Alex hadn't already written it I would have written something very similar. It brings the question close to home. $\endgroup$ – David Hammen Aug 12 '15 at 14:06
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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.

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