On the interplanetary net there is no “now”

Vint Cerf gives an interview for BBC’s Click Online (transcript and video) where he shares his thoughts on the interplanetary net.

He points out the lag issue – an interesting design constraint for future interactive service designers…

“When you get it out in space everything is different. For one thing everything is a lot further apart.

For example, Earth and Mars are 35 million miles apart from each other, when closest together in their respective orbits around the Sun.

They are 235 million miles apart when farthest apart in their orbits.

At the speed of light, 186,000 miles per second, it takes five minutes for the light signal or radio signal to go from Earth to Mars when they are closest together, and 20 minutes when they are farthest apart.

The notion of trying to control a device remotely when it is very, very far away is an amusing image.

You can imagine seeing an image which is 20 minutes old coming from Mars, so you are seeing where your rover was 20 minutes ago.

If you want to move it somewhere, you move the joystick to say “go right’ – but the rover will not hear that for another 20 minutes, so we have this 40 minutes’ round-trip time.

If you have steered it in some direction which is going to get it in trouble, like going over a cliff, by the time you find out 20 minutes later it is long gone.

So there is no such notion as “now” in an environment where things are so far apart.”

Fine if you’re surfing cached stuff (presumably Akamai-type services would be a ubiquotous feature of the interplanetary net)…more problematic though if you’re trading shares on Mars…

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