People were also skeptical of all the people before the Wright brothers who jumped off cliffs and killed themselves. Skepticism is the natural worldview of an engineer, because the universe is incredibly hostile to our ideas.

>Skepticism is the natural worldview of an engineer

This is in a nutshell why me and my (MBA)boss get into arguments.

If those people weren't optimists, they wouldn't have jumped off the cliffs.

> "This is hacker news, where people are trying to do difficult things to change the world."

Hahaha, I say this partially in jest, but Hacker News is basically for people to bash on dreamers' ideas.

> Hahaha, I say this partially in jest, but Hacker News is basically for people to bash on dreamers' ideas.

I completely agree, though I prefer to look at it as "constructive criticism" of every flavor.

If nothing else they might work out how to send larger probes to far out parts of our solar system that reach in days instead of months and years.

This is exactly the point of long shot R&D: lesser milestones are useful in their own right. Who knows what else might come of it?

Skepticism could be constructive. Most of time people just want to improve some novel idea in question format. If someone really do not care about it they would not even bother to raise a question.

I do want to raise my hand about how the sails is going to avoid space objects (meteoroid, space dusts... visible, non-visible, or even dark matters) given its large surface.

Outside of Earth orbit, space objects become incredibly rare, and outside the solar system they are rarer still. There are much bigger problems to worry about, believe me.

By the way, dark matter is likely passing through your body right now. It's effects can only be seen on the scale of galaxies.

I also am skeptical. Why not instead try to send a probe into the interior of the sun? (because its cooler there than at the point of those lasers) Why not create a survey of the Oort cloud (because its an order of magnitude closer). This project seems cool; but maybe not well thought out.

These people are obviously very passionate about their project, and they're moving forward on something they want to do. If you're so passionate about those projects you mentioned, start making them happen!

Don't sit around complaining about people who are "doing" stuff because they're not doing the stuff you want them to be doing. Get out there and do the stuff yourself!

Good attitude! Still, it doesn't make their project any more likely to succeed. Those others I mentioned - easier by an order of magnitude. It makes them sound insincere.

That depends on how much energy that the space craft reflects. If it reflects all of it, the space craft would not gain any heat at all unless there is some weird quantum effect that would mean otherwise.

Likewise, such a spacecraft could survive the inside of the sun.

I'm not a physicist, but it seems like perfectly reflecting photons in a vacuum is different from being immune to conductive heat transfer in a plasma.

That and reflecting one wavelength vs a wide spectrum.

I'm skeptical that a guy who made his money by "transferring a variety of U.S.-pioneered internet business models to Russia" [1] and then muscling in on Silicon Valley investments like WhatsApp where he "bought a stake from the founders for $125 million within weeks of Facebook snapping up the messaging giant for $19 billion last year" [2] is capable of this kind of engineering project. He's good at making deals but he's not the kind of roll-up-your-sleeves engineer that should be involved with space exploration. I think he's just jealous of Elon Musk and Richard Branson. This seems more like the Spruce Goose than anything else, and in the same vein as Howard Hughes, I'm sure he'll be looking for a giant government grant to pay for his techno-playboy hobbies.

[1] https://en.wikipedia.org/wiki/Yuri_Milner

[2] http://www.forbes.com/sites/parmyolson/2015/03/25/yuri-milne...