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Comment by b34r | Hacker News Reader

It’s completely breathtaking how massive our planet is in every measure that matters. And then we find out how big Jupiter is, VY Canis Majoris... The universe is a wonderful place!

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I've often wondered what living on a earth-like planet as large as Jupiter would be like. People on the other side of this "planet" would be aliens to you.

Nice thought but earth like planets can never get that big because of gravity.

A rocky planet the size of jupiter is not physically impossible. It is almost certainly incompatible with life, but there is nothing in the laws of physics that would cause such a sized planet to explode or collapse.

It would not explode or collapse, but it would almost certainly be molten liquid and/or gaseous rock for a very, very long time

Yes that is why I said it is unlikely to be compatible with life.

It would almost certainly be molten at the surface with no water no matter the distance from the star due to radioactive decay.

I had to check if this was true. So, Jupiter is about 10x the diameter of Earth, which means it has 100x the surface area. So while it would still be possible to travel anywhere by jet, it would be impossible to travel everywhere in one human lifetime (e.g. there would be 100x the number of cities, nations, etc, and it's already unlikely that any human has visited every major city). So yeah, tentatively I think it's true.

By that argument, people on the other side of the earth from you are already aliens to you. Why would it matter if you personally visit everywhere "of significance"?

You may enjoy reading Ringworld - it involves life on the inside of a Dyson ring totalling 3*10^6 the surface area of Earth.

Or the Majipoor series (Lord Valentine's Castle, etc.) https://en.wikipedia.org/wiki/Majipoor_series

> Majipoor is a planet much larger, though far less dense, than the Earth. It has been settled by humans, Ghayrogs, Skandars, Vroons, Liimen, Hjorts and other alien races for many thousands of years. These races live in an unstable truce with the shape-changing aboriginal inhabitants of the planet, the Piurivar.

I don't remember the size but TVTropes says it's "ten times the size of Earth". http://tvtropes.org/pmwiki/pmwiki.php/Literature/MajipoorSer...

At the same time, on average the universe contains nothing. It is so vast, that even if all stars were VY Canis Majoris, it would be still pretty much devoid of anything.

Dark matter would like to have a word with you.

If there is one thing we have learned through the history of science, it's to be careful about statements like "X contains nothing".

IIRC dark matter is believed to exists because some equations predict a single digit multiple of accounted mass in the Universe. That's not so much to change the mostly-void perception.

that's relative. the further your frame of reference expands, the older the image of earth observable at the border of the frame of reference is, so a few billion light years out, even earth would look boring. And even if that still implied 'mostly-void', I will take it compared to 'pretty much devoid'.

And also at the same time, even the occasional mass concentrations in between are, in all likelihood, mostly rather bland and boring compared to earth, with its magnificent abundance of self-organizing and self-replicating patterns. Even the more interesting aspects of geology tend to be direct or indirect traces of life.

Or maybe not, and there actually is every imaginable wonder out there, including a planet where mattresses naturally occur, but my money would be on earth being pretty much as amazing as it gets.

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