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Comment by ohazi | Hacker News Reader

Is anyone else a little bothered by the fact that the reported speed was 1/5 the speed of light, yet the flyby necessarily increased to well over the speed of light in order to actually get you to Mars before you got bored and closed the tab? Traveling at the speed of light would have taken 5-20 minutes. Traveling slower than that would have taken even longer...

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Travelling at the speed of light would have taken 0 seconds for you, the traveller, but 5-20 minutes for your observer.

However, the Lorentz factor at 20% of the speed of light is ~1.02. This means the distance you travel is only about 2% shorter, so relativistic effects aren't the reason for the discrepancy.

Plus, if it was large enough to have an effect on perceived time, it would affect the apparent distance as well, thus negating the point of the demo!

What is bothering me most now is that if Earth is 100 pixels wide then 1 pixel is 127.42km and Mars should be something like 54600000/127.42 = ~428500 pixels away, not the claimed 857000. The radius of planets has been used where it should be diameter and this error seems to have been carried forward throughout the demonstration.

EDIT: This has now been corrected - nice one!

Yeah, I hadn't realized that they were doing that, and it does bother me. I don't mind the idea that we're going FTL, but they should explain that in the text, not just report 20% of the speed of light. Ironically, it makes the distances seem shorter than they are, in a thing that seems designed to make you understand how long they are.

Speed of light: 1.07925285 × 10e9 km/h Reported speed: 200,000 km/h

So more like 1/5000 the speed of light. But as pointed out below the reported speed may be way off.

I wonder if a mistake about the speed of light was made; it's about 300,000 km per second.

Right, but the original comment is also quite right that the speed is being misreported and the actual speed you're going (reported as 7000 pixels per second) is 3x the speed of light:

    (12742 km) / (100 px) * (7000 px)/s / c = 2.975

Yes; mine was more a comment on the site.

I also wish they would have noted the acceleration. Not doing so in fact undermines the point they're probably trying to make (giving users a visceral feel for the distances involved). Can't say it bothered me, though.

I'm more bothered by the authoritative fact that 'the timeline for a manned mission to Mars is the 2030s'. Says who, NASA?

They're not the only ones trying to get there.

Does anyone else have a realistic more aggressive timeline?

I'm planning to head over tomorrow. I'll let you know how it goes.

Are you there yet?

Yes. HN is loading slower than normal, however, so you'll have to wait for a full assessment. This whole three-way handshake thing is not such a great idea from Mars.

so was i, wanna split the fare?

See the response above - there is a window in 2018/2020 that private entrepreneurs will shoot for. I wish them luck, personally .. I'd love it if someone other than NASA got there first. It would truly ignite the human race.

The response above also suggests 2018-2020 is too soon. Are you aware of any private entrepreneurs realistically disagreeing?

Like the advent of nuclear energy!

See "The Case for Mars" by Robert Zubrin (manned landing 10 years from project start, then every 2 years thereafter), or the various hints dropped by Musk in interviews as to his plan.

Not that I know. SpaceX has considered sending an unmanned mission based on its Dragon platform in the 2018/2020 window which would prove a lot of technology that they could used for a manned mission later.

Essentially all Mars missions under serious consideration rely on special alignments of planetary orbits to minimize the fuel required. That leads to very specific "launch windows" that may only occur every few years. For an Earth-Mars trip, the basic launch window is available roughly every two years, but there are particularly low-energy opportunities every 16 years or so.

My understanding is that the next of those will be the 2018/2020 launch windows, which is almost certainly too soon for a mission to be ready. So the following low-energy opportunities will be somewhere in the mid 2030's. That's not to say that it would be impossible to use a launch window in the mid-2020's despite the higher fuel cost (or even some other orbit entirely that didn't try to minimize fuel at all), but doing so would be substantially more difficult.

Here's a link that is useful primarily because it links to more thorough discussions: http://en.wikipedia.org/wiki/Exploration_of_Mars#Launch_wind...

The difference between the Hohmann transfer orbit available every two-ish years and the low-energy opportunities is not significant enough to impact mission viability.

The reason a mission to Mars is "scheduled" for 2030's is because that's the nearest date outside of government budgeting schedules. It would take us 10 years to put together a focused effort (like the Apollo program), there's absolutely no plan to do so right now or over the next 10 years of the government budget. So by that sketchy line of thinking, the earliest this could happen is 2013 + 20 years, or 2033.

Maybe I'm showing my age, but I remember a decade ago "the Mars landing" was scheduled for the 2020's. In the 90's we were talking about the 2010's (now!). I bet you when 2020 rolls around, it'll be the 2040's that we're looking towards.

Exactly. The 2030s are just beyond what we could demonstrably prove ISN'T currently in the works.

For me it currently says "You're currently travelling at 7,000 pixels a second 200,000 km/h" - which is clearly wrong, as at that speed it would take an hour to get to the moon.

Good idea, well intentioned. But they got the numbers wrong...

100 pixel earth = 13KM

1 pixel = 0.13KM

7K pixels/s = 910 KM/s

910 * 60 * 60 = 3.3 Million KM/h

The Earth is not 13 km in diameter. Maybe you meant 13 Mm, or roughly 13 000 km? The result is ~3 billion km/h then. I haven't timed it, but that seems to align with how long the animation took (around half of a minute).

I timed it, and it was about a minute, so right in line with the 7k pixels/s. That does translate to about 3 billion km/h, or about 250,000 mh/s².

Distances are in pixels, with the Earth's diameter being 100 px.

Yes, he knows. But the point is: They say they're going 20% of the speed of light (in pixels). But the closest approach of Earth and Mars is about 4.35 light minutes away from each other. So if our virtual speed is 20% of the speed of light, it follows that the page should take more than 20 minutes to reach Mars. And it doesn't.

It doesn't even take 4.35 minutes, so the page must be continuing to accelerate past the 20% c measure, to superluminal speeds, in order to finish in a couple of minutes or so.

Which they don't mention.

The page flashes for me a couple of times, after which the starfield is still and then rapidly speeds up again. I assume this means that we're travelling with the assistance of warpgates or similar - and at 127km/pixel, it's unlikely that the warpgate or the ship would show on the map.

Nah, because if it's physical travel the starfield won't change at all. :P

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