Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: ukmicky on 17/04/2005 02:03:44
-
THE MOON IS SLOWLY MOVING AWAY FROM US.
SO MY QUESTION IS.
IS IT ADVANTAGEOUSE FOR LIFE OR IS IT JUST A COINCEDENCE THAT INTELIGENT LIFE ON EARTH HAS EVOLVED ON EARTH AT THE EXACT TIME THAT THE MOON IS THE EXACT DISTANCE REQUIERED TO COVER THE SUN 100 % WITHOUT ANY WASTAGE DURING AN ECIPLSE. IF THE MOON WAS HALF MILLION MILES FURTHER OR NEARER WOULD CONDITIONS CHANGE SO MUCH THAT LIFE WOULD FIND IT HARD TO SURVIVE,
OR ARE WE IN THE PRESENCE OF THAT BILLION TO 1 CHANCE
-
1. turn off caps lock
2. i dont think the moon effects life on earth that much, but if it disapeared i heard that the planet would like flip out and itd be bad...
-
I would guess it is a coincedence, but not nearly as an unlikely one as you indicate.
For a start the earth's orbit is an ellipse with at distance that varies by 1-2% so the size of the sun will change by about 1.5% over the year. Also if you work out the actual ratio of distance to radius for the sun and moon you get 215 and 220, so there is another 2-3% error there,
so the real chance is something like:
time moon and sun look about the same size (within 4-5%)
----------------------------------------------
age of earth
which is going to be a hell of a lot better odds that 1: a billion I will try and work them out in the morning.
-
Ok I have done some calculations, from the moment of inertia of the earth, and the momoent of inertia of the moon going around the earth, and the fact that from coral daily growth rings we know that 200 million years ago there were 400 days in a year, and doing lots of horrible approximations I think the radius of the moon's orbit has changed by about 3% in the last 200 million years.
If you consider that you can change the apparent radius of the moon from 5% bigger to 5% smaller than the sun there will be about a period of roughly 600million years when they will be as close to one another in size as they are now.
Assuming our moon-earth system, and that it is 3-4 billion years old there is about a 1 in 5 chance of them appearing about the same size. Now I don't know what the odds of being on a planet moon system like ours are, but that very probably strongly affects the chance of intelligent life appearing...
-
Hey that means my calculations were not hugely off then, at 3.8cm a year it would take about a billion years to change it's radius by 10% (ok making a big assumption that things are linear which aren't). Right order of magnitude, not bad for physics ;)
-
ok billion to 1 one is way over the top granted. im now a junior
member. so i must research before i post
the moon is 4.5 billion years old
As you read this, the Moon is moving
away from us. . Researchers say that
when it formed, the Moon was about
14,000 miles (22,530 kilometers)
from Earth. It's now more than
280,000 miles, or 450,000 kilometers
away., at an average rate of
about 4 centimeters per
year. That means that the share of total solar eclipses is slowly decreasing.
Eventually, the Moon will be so far
away from Earth that there won't be
any total solar eclipses anymore,
but another factor is that the size of the Sun itself will grow in time
however that wont happen for 800 million years or so
[/quote]
-
Sorry I possibly went slightly overly negative there ( but you were posting in capitlas :p ) it is an interesting property, but it is also interesting how one misjudges probabilities...
have fun
Dave
-
gravity won't let the moon get that far away
if the moon did disappear them there wouldn't b any more waves in da ocean n seas n large lakes
animals would go crazy n some would go extinct
-
You would still get waves they are primarily produced from wind, you wouldn’t get any tides however.
wOw the world spins?
-
Also the moon keeps a LOT of atmosphere in suspension. So much even, you find air particles halfway to the moon. If all that would come down, we'd be heading for a Venus type of super green-house. So it would make some difference, and don't forget we don't know half how much tidal energy not only keeps oceans alive, but maybe also necessary tectonic processes.
-
Your would still get tides without the moon as the sun also produces tides, they are about 1/4 of the strength of the moon's tides. When they are both acting on the same line you get spring tides and when they are prependicular you get neap tides.
-
Dave - why do you get a spring tide when the moon and sun are aligned but the moon is on the opposite side of the Earth to the sun (a so-called new moon) ?
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
-
I think I have worked this out, it may be a little confused due to the fact I have just worked it out (and text is not the best medium for drawing diagrams)
You get two tides every day because the water on the side of the earth closest to the moon is pulled towards the moon strongly, the earth itself is pulled towards the moon a bit more weakly as it is on average further away, and the water on the far side of the earth is pulled even more weakly as it is further away still.
| centre | |moon|
-> ---> ---->
this means that you get a bulge (high tide) closest to the moon as the water is pulled away from the earth, and a bulge on the other side where the earth has been pulled away from the water. **
The size of these bulges will therefore be the difference between the force of gravity from the moon in the centre of the earth and at the two sides.
If you have both the sun and the moon pulling in the same direction:
E m S
x->
-The force from both the moon and the sun is towards the right
-The size of both forces increases towards the right. (inverse square law)
So the two changes in force add to the right giving a bigger value -> a spring tide.
Now if the moon is on the other side:
m E S
x->
-The force from the sun is still to the right and increases to the right
but
-The force from the moon is to the left but decreases as you move to the right
Total change in force = direction * change in amount of force
this means that the change in force from the moon is the first value(++) *-1 for the change in direction *-1 for the fact that it is now decreasing rather than increasing.
-1*-1 =1 so the changes of force across the earth for the moon and the sun still have teh same sign and so add, therfore you again get a spring tide!!!
** It is a bit more complex than this as oceans have inertia, but this only affects the times of the high tides.
++ when the moon was on the same side as the sun.
-
If the moon does float away, what am I going to howl at once a month ?
Men are the same as women.... just inside out !!(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.world-of-smilies.com%2Fhtml%2Fimages%2Fsmilies%2Fmini%2Fmini018.gif&hash=43d4f680fb1e52aecb14b539cb9eba2c)
-
I'll moon for you!
-
Without the moon there would be significantly less nocturnal life, since most nocturnal life still relies on sight for its activity, thus the moon. Anyone who's lived out in the country will tell you that nights with a full moon are much noisier than those where the moon is darker.