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Comment by krylon | Hacker News Reader

Ignoring all the fascinating stuff about Jupiter, let me point out this gem: The download of six megabytes of data [...] took one-and-a-half days

I sometimes like to scare kids by telling them about the time when I surfed the Internet with 14.4 kbit modem, but even that looks incredibly fast compared to the speed of interplanetary data transmission (back then, 6 MiB would have taken me about 2-2.5 hours).

(NB that I am not complaining or anything, just pointing out that this is many orders of magnitudes slower than anything one would normally consider a "slow" connection.)

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http://descanso.jpl.nasa.gov/DPSummary/Juno_DESCANSO_Post121...

> On the HGA we expect ≥18 kilobits per second (kbps) (≥12 kbps during Grav passes due to power required for carrier signal), and ≥10 bps on the MGA.

HGA = High Gain Antenna, MGA = Medium Gain Antenna. HGA activity is limited to when the spacecraft is precisely aligned towards Earth:

> Due to the nutation of the spinning spacecraft following any maneuvers, we will need to allow several hours for nutation damping following Earth-point maneuvers before using the HGA.

> Currently we allow 8 hours prior to most DSN tracks and 16 hours prior to the 6-hour MWR or Grav perijove science passes that start at PJ – 3 h.

So it's not necessarily any slower than your modem once it gets going, it just has terrible latency and dialing the connection can take the better part of a day.

It's also fascinating to think about how TCP is ineffective at that distance.

https://en.wikipedia.org/wiki/Interplanetary_Internet is a good starting point to learn more.

That means when humans finally colonize Mars, there will be two FaceBooks, FB Mars and FB Earth, with any communication between them running at a lag.

I bet there will be AI research to create bots to act in "real time" on your behalf on the opposite planet. If the artificial agent can imitate your own actions and judgements, it would be a good way to surpass the speed of light. It will be necessary to build these agents because other interested parties could use the time lag to unfairly gain an advantage over you. The more we explore, the larger the time lag. With Jupyter it is 33-53 minutes. With Pluto it's 5h. The nearest star - 4 years. The Moon is at 1.3s.

The last thing I need is a realtime Facebook now. I feel like I should build in a delay of ~1 week to everything I do.

Yes. I world also like to see the delay randomized between 3 and 10 days so that nobody can tell what tempo you're replying at.

It seriously sounds like you might have a notification addiction: you should try forcing yourself to check messages at most only a few times a day for a while to detox.

Distributed systems are hard to get correctly when there's a few extra milliseconds of latency. Imagine now having 30 minutes of latency be the norm, and sometimes more.

It's an interesting problem I hope I'm around to witness.

You are truly seeing the future, my friend.

TCP had to be revisited when Wifi became popular. Space is that x 10000.

This is off topic for this post, but astronomy, space and space missions always have a way of putting things in perspective and showing how much humans have progressed and learned, and also the magnitude of human achievement (in the past) with what seem like completely unusable equipment today.

I look at the Voyager (1 and 2) data whenever I feel like comparing things to what we have today, and I always end up being overwhelmed by the facts, figures and what humans have achieved. I can't help but be awed.

Quoting from the Voyager FAQ [1]:

> Question: How fast are the Voyager computers?

> Answer:Not very fast compared to today’s standards. The master clock runs at 4 MHz but the CPU’s clock runs at only 250 KHz. A typical instruction takes 80 microseconds, that is about 8,000 instructions per second. To put this in perspective, a 2013 top-of-the-line smartphone runs at 1.5 GHz with four or more processors yielding over 14 billion instructions per second.

Quoting from the Voyager Interstellar Science page [2]:

> Science data are returned to earth in real time at 160 bps.

Just imagine sending data to earth at 160 bps from a distance of 20 billion kilometers and 17 billion kilometers^ [3] , respectively, for Voyager 1 and Voyager 2. The time it takes light to travel between earth and Voyager 1 and Voyager 2 is currently about 19 hours and 15.5 hours^, respectively. (Some other communication is collected and sent at 115 kbps)

^: These figures are rounded since it doesn't make a huge difference to me at this magnitude, and also, the distance from earth to these two spacecraft does sometimes decrease due to earth's revolution around the sun.

[1]: http://voyager.jpl.nasa.gov/faq.html

[2]: http://voyager.jpl.nasa.gov/science/

[3]: http://voyager.jpl.nasa.gov/where/

> Just imagine sending data to earth at 160 bps from a distance of 20 billion kilometers and 17 billion kilometers^ [3] , respectively, for Voyager 1 and Voyager 2.

Sending data - regardless of bandwidth - over these distances is very impressive in my book. Let alone sending a computer so far and have it still work after all these years.

>I sometimes like to scare kids by telling them about the time when I surfed the Internet with 14.4 kbit modem

You just gave me a great idea for a Halloween costume.

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