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Comment by exabrial | Hacker News Reader

The sun? Seems a little expensive.

$100M for a space mission seems inexpensive, let alone for our first interstellar one. Sending a few people to low Earth orbit costs $70M/person on Soyuz.

$100M is just the amount promised by the billionaire philanthropist. The mission itself would cost several orders of magnitude more.

The article states

"At an estimated present-day price of approximately $10 per watt of laser power, building and operating Breakthrough Starshot’s 100-gigawatt array today could cost as much as $1 trillion."

but goes on to say that the price is plummeting quickly, and so may be affordable in relatively short order.

Okay, but people are gigantic and heavy, and you have to feed them. Also, they usually have to breathe and go poop. They're like hundreds of thousands of grams, and then some, so 70M is less surprising.

Sending a working cell phone into low earth orbit probably wouldn't approach those numbers, I don't think.

If you're an amateur astronomer there one star that's incredibly easy to find, but you can only see it during the day.

I'm pretty sure we get orders of magnitude more illumination from the sun, even in the middle of the night, than we get from any other star.

It's called moonshine :^) at a magnitude of -14, the moon, which has ~0.25% of the brightness of the sun at -26.

All of the visible stars in the sky come to less than 10% of the moon's illumination. https://en.wikipedia.org/wiki/Apparent_magnitude

Sure, we get more illumination from the sun at night than we do from the stars. That doesn't mean we can see the sun at night; we can't.

Can you see the sun through a (reflecting) telescope? What's the difference between seeing a star via its light reflecting off a planet and seeing the star via its light reflecting off a mirror?

Mirrors show the image of what they reflect. Non-reflective surfaces don't.

What's the difference between the image of yourself in a puddle of rain on the sidewalk, and the image of yourself in the dry concrete of the sidewalk? One exists, and one doesn't. There's still light that travels from you, to the sidewalk, to your retinas, but that light reveals essentially nothing about you. The sidewalk has overwritten the information it used to carry.

I was thinking even when the moon was on the wrong side. IIRC we get more sunlight reflected off Jupiter alone than we get from any other star.

Sure but you can't see the sun at night...

Sorry, but are you on drugs?

Solar Probe Plus mission for instance is a $1.2 billion program.

http://www.space.com/9262-nasa-cant-afford-senate-timeline-s...

Playing along.... $100 million for research before sending sounds fine to me.

The sun (8 minutes from earth) is not a star. It is considered a dense helium hole.

I probably had you second thinking your comment for a bit. It's actually a star.

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