If the planets were as close to the Earth as the Moon is (was?)

[Aiel Heart]

OOOOOOO shiney. Did you get one of Jupiter and its moons?

 

If not, one of those would be SUPER amazing

 

 

Going to respond to Fnorrll simply because I like talking about science and haven't gotten to do it much lately. 

 

Going to spoiler it because I'm going to babble and it will be long :P 

 

 

 

I asked him about Jupiter in particular since that would be the most extreme example. In that instance, there is the automatic change that we would be a moon of Jupiter because that's just war would be the case in that situation. Here was his answer:
"If we were a close moon of Jupiter, what would happen?"

I can't think of anything dramatic. Except if there are multiple moons. For instance the three-way tug of war between Jupiter and the other moons keep Europa and Io hot in their interior. But the Earth is already hot in the interior, so I imagine if we orbited Jupiter then that would be even worse and we would have world wide volcanoes. Jupiters magnetosphere would make electronics interesting, but we would have developed that technology within that context so who knows. Tides would definitely be larger. Oh! And the Earth would be tidally locked, so a "day" on the Earth would be the orbital period of the earth around Jupiter. For reference, io and Europa are on about 3 and 7 day orbits around Jupiter.

Not sure who your source is (an astronomer with a doctorate in astronomical physics ;P )  (*edit* just noticed he mentions a lot of the same points I do so I guess I only disagree with his conclusion not his theory of events, sorry for not reading more carefully apology accepted :) you have valid points though--it would be pretty extreme ) and don't mean to sound rude but I don't think the earth would survive being 240,000 miles from a planet the size of Jupiter. Gravity is affected by mass, meaning the larger the planet, the stronger it's gravity field, hence Jupiter has the strongest gravitational pull of any planet in our solar system by far. Being so close to it would wreck our tidal systems and not just that but even affect the geo-tectonic plates of the earths crust, causing earthquakes and volcanos with much greater consistency and force than we currently see.

Like you said, same points, just the degree to which that would happen which differs between your conclusion and his, and how much that degree would affect us. I'm not sure how much thought he put into it but he tends to do all sorts of math and figuring in his head in routine conversation so his thoughts are probably in somewhat of a ballpark. A lot of it would also depend on the stability of the orbit and such. 

 

Of course, we would also become a moon of Jupiter- not the other way around. And we would have to maintain an incredibly fast orbit to of such a large entity to keep an even telemetry within its gravitational field and not eventually be pulled into the planet itself.

Both are givens ;)

On top of that we have to consider that Jupiter has four moons of its own (I know this because I was looking at it with a 1000x telescope last night, was very pretty! you could even see the banding going across it) so there would possibly be issues with overlapping orbits etc. Also consider the radiation Jupiter throws out, remember only earth is a habitable planet in our solar system.

You saw the four big ones--jealous! I haven't had access to telescopes very often. Jupiter actually has something in the ballpark of... 20 moons? Too lazy to double-check that number right now. There's actually a lot of research going into figuring out whether one of those four, Europa, may be habitable. I took a class about the habitability of planets and how we think life formed and all of that. It combined all of the sciences and we learned different way to calculate the chance that there's life elsewhere and all sorts of cool stuff. I think it's still the favorite of the classes I've taken; every day was just fascinating! (Yeahyeah gaining more nerd points by the word in this thread :P )

 

Last but not least, for this to happen- would Jupiter come to us or would we go to it? Because that would have a vast effect in terms of the temperature hitting either planet as opposed to now, or the level of light that the earth would get from the sun should we go there... Not to mention (possibly?) the effect of the gravitational pull of the sun on a much larger object such as Jupiter being much closer to it. I'm just guessing at this point.

We were talking about what it would be if that was just how it was. Either planet moving would be really interesting.

Earth going to Jupiter: The force that would send Earth so far off course would probably be enough to completely destroy it, or at least us, and there'd be little left to get screwed up by the tides and volcanos.

Jupiter moving to Earth: It slows down enough that it can't fight the Sun's pull anymore? What would speed it back up to make it stop at Earth? What effect would passing through the asteroid belt have on it? More moons (come to think of it the asteroid belt would have destroyed Earth en route if the kicking off force didn't). Jupiter actually probably wouldn't change all that much in composition and such because we've actually found Jupiter-like planets not too far away from their stars--possibly as close as an AU. Those all probably became so close during the solar system's formation however; a Jupiter size planet (or any planet) moving from its established orbit would be considered odd. Though, it should be noted, we don't have much of a sample of all planets in the universe to take this from. But anyway, Jupiter probably wouldn't have most of it's gas burn off or anything like that; it'd still have a pretty strong gravitational pull on it. It's mainly during formation that gas is tricky. 

In fact all of that is off the top of my head and could be looked into further and possibly I could be corrected. But all the elements of the solar system are placed exactly where they ought to be for earth to be able to sustain life as we know it.

Speaking of that--do you know the theory that the moon was once an Earth-like planet?

I can't remember all that goes into it right now, but I do recall a bit. Compared to other terrestrial planets, we have an oddly big core (core size compared to planet size), which is part of what makes Earth so good for us (stronger atmosphere because of the better gravitational pull, tectonic plates and such are also affected, etc). The moon is very much like a terrestrial planet, but it has a very small core. And there's a lot more of reasons that support the possibility that the moon glanced off of the earth, contributing to earth part of its core and surface, and then gravity helped both round themselves out a little more evenly again. An additional reason we owe our existence to the moon (beyond tides and helping to deflect asteroids and such :P )

 

 

 

This has been a Heart Science Babble. Come back next week to learn more about Europa and why it's potentially habitable! 

 

(Not that people tend to talk about space on a day to day basis, but I have a suspicion that my RL friends avoid talking about it near me because they know how excited I get :P maybe I should have become an aerospace engineer after all...)

[The_Fnorrll_Reborn]

Sorry, my argumentative side kicked in so I found this:

 

What would happen if Jupiter suddenly replaced our moon, with (initially) the same orbital speed?

Best Answer: Frank Heile, PhD in Physics from Stanford University

 

818 upvotes by: Mark Barton (PhD in Physics, The University of Queensland, p... (more) ), Don van der Drift (In PhD Physics program for 2.5 years at Technis... (more) ), Mike Specian (Theoretical astrophysics doctoral student, JHU,... (more) ), Stephan Hoyer (Physics Ph.D, UC Berkeley), Amol Patwardhan (PhD student in Physics (Astrophysics)), (more)

 

TL;DR: The Earth will crash into Jupiter in less than 1 day. And by the way, Jupiter would be HUGE in our sky (and get even bigger as we fall into Jupiter).

Link to full article with workings out: https://www.quora.com/What-would-happen-if-Jupiter-suddenly-replaced-our-moon-with-initially-the-same-orbital-speed

[Aiel Heart]

Fun! I'll look at it later!

 

That is noting with the SAME orbital speed though, which of course would end in disaster. 

 

Now I want to calculate what orbital speed would result in a stable orbit.... GRAH I'M STILL SUPPOSED TO BE ON BREAK FOR TWO MORE DAYS!!!!!!!!!!!

(We'll ignore that I'm headed back to my apartment as soon as my dad stops by to say goodbye to me on his lunch break)

[Mrs. Cindy Gill]

I thought the popular theory nowadays was the moon was a result of a big boom with a big big rock that knocked a whole bunch of earth into orbit, mainly surface, making the core differential what it is but I dunno. it was a neat cgi on some discovery channel show.

[The_Fnorrll_Reborn]

Fun! I'll look at it later!

 

That is noting with the SAME orbital speed though, which of course would end in disaster. 

 

Now I want to calculate what orbital speed would result in a stable orbit.... GRAH I'M STILL SUPPOSED TO BE ON BREAK FOR TWO MORE DAYS!!!!!!!!!!!

(We'll ignore that I'm headed back to my apartment as soon as my dad stops by to say goodbye to me on his lunch break)

 

The article answers that question and provides a link to the calculations. The trouble is ( I imagine) surely if you change the orbital speed it's always going to have an effect, even if you bump it up to what's needed to maintain a valid orbit, which for the record is almost 10x faster than the moon.

 

Article also mentions things that have been mentioned previously, tidal forces, volcanic activity, and of course the radiation emitted by Jupiter.

 

Have fun with the read.