# Size of our planets

Is there any answer to "what determines the size of each planet"?

Order by

As far as I know there is no theory that determines the size of a planet.  Any such theory would probably have been shredded shortly after planets were discovered outside our solar system.

The Roche Limit gives us a basic guideline as to the size of a planet, its tempure, and density,and how closely it may orbit its parent without being torn apart.  Unfortunately is is over a page long and has so many permutations and derivitives that I hesitate to post it here.

Basically, the denser the material a planet is made from, its mass and orbital energy, the longer is has been accreting, and the distance from its star, dictate the size of the planet.  That makes calculating the mass and temperature of exoplanets rather difficult, but we can make an approximate educated guesstimate of how we are always completely wrong.

I can still remember a paper written by Fred Hoyle saying that Jupiter's moon Io would be one of the coldest bodies in the solar system, when it turns out to be one of the hottest.  Hoyle also said that Titan would be at least as hot as earth because it had an atmosphere.  As it turns out, Titan is one of the coldest things in the solar system.

Science has to prove to itself constantly that we still don't know very much, and most of what we think we know turns out to be wrong.

Even so, the more we know, the better it gets, even if we know virtually nothing.

http://en.wikipedia.org/wiki/Roche_limit

Think it through, work the problem, never guess, sharpen your intuition.

## Related Questions

### Asked:The fate of planets not of stars

you seem knowledgeable in the areas I'm interested so maybe you can give me an answer to this question: What happens to PLANETS (not stars) when they get to the end of there life's? do they keep ...

### Asked:Which underground station is closest to Office ...

Which underground station is closest to Office Refurbishment London zoo?

Could someone please tell me the name of the male English teacher who wrote a book about 3 areas of strange electromagnetic disturbances--one area being the coal Tipple in Grand Haven, Michigan?? I ...

## Be The First To Answer

Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them

Hot Topic

### What planet is closest to the sun?

Mercury is the first out of the 8 planets, which is closet to the sun.

### Does any have pricing info about planet chiropractic in douglasville

Call them and ask what is the average range for an initial office visit. If they will not tell you. Don't go. Dr Ron. Jupiter, Fl.

### Bright planet next to the moon

In that all planets besides Pluto (a dwarf planet) orbit within a few degrees of the Ecliptic Plane, then virtually any planet may be seen conjunct the moon. In the days of Isaac Newton, predicting the location of planets was a very popular university passtime -- and it was considered most unfair ...

### Should humans inhabit new planets

Let's say we got there, the crew has not murdered each other off, that they have moderate politics, compassionate beliefs, and a realistic point of view when they land . . . somewhere. What would happen if they came to a planet that is as crazy as this one? It would be a moral imperative to blow ...

More