moon replaced by big planet? or where could planet be by earthwithout harm?

[mntjohnson@gmail.com]

moon replaced by big planet? if planet far away would tides and other
effects be the same?

or where could planet be by earth without harm? how far must planet be
to not destroy earth or even cause tides?

it seems a planet would have to be months away to not adversely hurt
earth...

TOMJOHNSON

[Fred J. McCall[_3_]]

wrote:
:
:moon replaced by big planet? if planet far away would tides and other
:effects be the same?
:

Not the same, necessarily, but you'd presumably get some. They'd
probably be slower, as the distance (and hence orbital period) would
likely be larger (although even that is not required).

:
:or where could planet be by earth without harm? how far must planet be
:to not destroy earth or even cause tides?
:

Look into Roche's Limit. They show how to compute it here:

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

:
:it seems a planet would have to be months away to not adversely hurt
:earth...
:

Not necessarily.

--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw