Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Seven earth-sized planets discovered circling a star 39 light years from Earth

nature.com

Post reply on HN
Print view View original

581–590 of 754 posts

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#581

Post by kakarot »

lutorm wrote: post #274
kakarot wrote: post #241

Earlier quoted context omitted.

Referring to an average of 1-2 trillion years as "trillions of years" is either misleading, uninformed, lazy, or a combination of the 3. When dealing with hard science it's important to choose your descriptors wisely. Most readers will not follow up.

Uh, "1-2 trillion" IS "trillions". I'm not sure how you can make that out to be misleading. Stating "trillions" in lieu of "tens of trillions" or "hundreds of billions" might be misleading, but this is not.

It seems the rest of HN disagrees with me, but when I hear "trillions" I think in plurality of trillions, a handful maybe, but afaik these things don't really live past 2 trillion years

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#582

Post by saalweachter »

mirimir wrote: post #521
Mtinie wrote: post #474

Earlier quoted context omitted.

@ConceptJunkie > The Moon is about 2% of Earth's mass, not 27%. 2% of mass, yes, but also 27% of the diameter. You are both right.

My first reaction was WTF? Then 0.27^3 = 0.0197 And then, only 60% as dense (no core) so 0.0119 :)

One of my scale numbers is, everything between Jupiter and the Sun masses less than 2 Earths -- Venus, Mars, Mercury, the Moon, and all the asteroids mass less than the Earth.

And only just barely! You get to around 99% of the Earth's mass with the rest of the inner solar system.

All of the other rocky bodies in the solar system give you another 10% of Earth's mass out to Pluto and another 10% beyond.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#583

Post by misnome »

blueprint wrote: post #555
certifiedloud wrote: post #549

Earlier quoted context omitted.

Understanding something doesn't mean you can manipulate it in any way you want.

When it comes to physics, it does in fact mean you can use the principle you discovered in engineering technology. That's kind of the whole point.

By the same 'argument', understanding the laws of thermodynamics (which prohibit perpetual motion) allows us to exploit perpetual motion?

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#584

Post by thefifthsetpin »

sathackr wrote: post #524
jerf wrote: post #167

Earlier quoted context omitted.

The debate rages. The problem is that one side of the planet is essentially exposed to space and thus tends to be at cosmic background temperature, and the other side exposed to the star. It is thought by a lot of people that anything volatile enough to be a gas, ever (so, including water), would rapidly end up migrating over to the frozen side, so even if the planet started with the right mix of water and whatever o…

So if the water and gasses migrate to the cold side, I wonder if that would eventually make the cold side heavy enough to be rotated towards the star, causing the planet to periodically(probably over several millenia) reverse the side facing the star.

You're thinking of Earth, where the polar ice builds up perpendicular to the sun, causing tidal effects to wobble our axis a bit.

In this case, the ice is building up in such a way to make the planet even longer in the direction that tidal locking already had elongated it. The effect of which is that tidal locking would get stronger; not weaker.

I don't think it matters too much that it'd be icy on one side and rocky on the other; I think it matters more that it's oblong. But even supposing it does matter, if your intuition is that the more-dense end would want to fall towards the star, then that'd be the rocky end; not the icy end. Yes, the icy end got heavier supposing you measure from the rocky planet's center. But if you shift your frame of reference to be the planet's center of mass, then both halves of course kept exactly 50% of the mass; the densities are what shifted.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#585

Post by maverick_iceman »

Arizhel wrote: post #539
maverick_iceman wrote: post #461

Earlier quoted context omitted.

General relativity gives a very solid and accurate understanding of gravity.

It does? Great; please point me to some instructions on how to build an anti-gravity device. I can easily build myself an electromagnet with some wire and a battery, so if our understanding of gravity is so great, I should be able to do the same with gravity, right?

What's your score?[1]

[1] http://math.ucr.edu/home/baez/crackpot.html

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#586

Post by misnome »

blueprint wrote: post #220
raspasov wrote: post #138

Earlier quoted context omitted.

It sounds like you have a startup idea on your hands : )

You've no idea. But for the first step, I need to find one or two very truthful physics grad students / electrical engineers who feel some responsibility for Earth or saving themselves. You wouldn't happen to know someone?

I think you mean "Post-truthful"

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#587

Post by bbarn »

echelon wrote: post #575

I imagine any intelligent life that evolves on a system with so many planets in such close proximity--many within the habitable zone, and each perhaps with atmospheres and organics--will have a much easier time than we do of pushing forward to becoming a multi-planetary species. We lucked out with Earth being as hospitable and resource rich as it is, but we're stuck in a deep gravity well with not much in our solar s…

..and what problems we don't have they might have!

Planets too close, disrupting each other's ecosystems. The usable ice being distributed amongst several planets when the system was formed instead of a single one.. there's no end to catastrophic possibilities.

This is why I still love sci-fi. Anything you can think of, put it on paper, and it could make for a great story.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#588

Post by sixdimensional »

antiviral wrote: post #548
dmix wrote: post #6

My favourite part of the press release: > The planets also are very close to each other. If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the moon in Earth's sky. > In contrast to our sun, the TRAPPIST-1 star – classified as an ultra-cool dwarf – is so cool that liquid water cou…

Just as interesting is a recent news story about a plan to build an interstellar space ship, propelled by giant solar sails to travel about .2c (20% of the speed of light). In other words, we could get to the Trappist-1 star system in about 145 years.. practically in the blink of an eye. https://www.gizmodo.com.au/2017/02/how-an-interstellar-stars...

Nuclear pulse propolsion... Project Orion... if only we could figure out the darn problem with the fallout and treaties/bans.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#589

Post by stevewilhelm »

jameshart wrote: post #389
dmix wrote: post #6

My favourite part of the press release: > The planets also are very close to each other. If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the moon in Earth's sky. > In contrast to our sun, the TRAPPIST-1 star – classified as an ultra-cool dwarf – is so cool that liquid water cou…

Importantly, that means there is basically no way that a civilization that developed on such a planet would not at some point endeavor to travel to those other planets.

> no way that a civilization that developed on such a planet would not at some point endeavor to travel to those other planets.

That seems like a very human statement.

One could argue for a civilization to succeed it must be content with living on its home planet. And as a result, it would take good care of it.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#590

Post by mirimir »

saalweachter wrote: post #582
mirimir wrote: post #521

Earlier quoted context omitted.

My first reaction was WTF? Then 0.27^3 = 0.0197 And then, only 60% as dense (no core) so 0.0119 :)

One of my scale numbers is, everything between Jupiter and the Sun masses less than 2 Earths -- Venus, Mars, Mercury, the Moon, and all the asteroids mass less than the Earth. And only just barely! You get to around 99% of the Earth's mass with the rest of the inner solar system. All of the other rocky bodies in the solar system give you another 10% of Earth's mass out to Pluto and another 10% beyond.

You just blew my mind ;)

What do we know about the gas giants' cores?

Post reply on HN