Celestia Forums

One thing to keep in mind is that the further away the Moon moves, the slower the tidal interaction that causes that movement.

...John...

HP, can you please just use the default text colour? It's impossible to read your text in the Silver board layout.

I've heard a figure of more like 1-2 inches a year. The Moon would have to approach about 1,500,000 km from Earth before Earth lost its grip. This is known as the Hill Sphere. But like Dollan said, the further it ventures, the slower it receeds. Earth's rotation would tidally lock to the Moon orbital period before it loses its grip on the Moon, but the timeframe for this to happen exceeds the Sun's life. Earth and Moon will be swallowed by the Sun when it expands to a red giant long before the tidal lock occurs.

Hunter Parasite wrote:Actually, by the time the sun reaches the red giant stage, the earth and moon will not be swallowed by the sun because it waas born of a nebula with a solar mass less than 20 so when it reaches it's red giant stage it will not be large enough to get Earth, only mercury and venus will be swallowed.

Actually the jury is still out on that. It seems likely that Earth will still be destroyed by the sun since the red giant's surface will be very close to Earth's orbit and we could be caught in its extended atmosphere which can reduce our orbit by drag effects.

Either way, earth will be roasted completely. Whether it's actually destroyed or not is irrelevant really.

Be awesome if something could still survive on the Earth when the sun gets bloated and fat That'd kick the "Goldilocks Conditions" in the butt.

Nothin' like sticking marshmallows on a stick and pointing them to the sky when the sun eats Mercury and chomps down Venus then wishes for a Mars Bar.

Heh who knows, maybe this could happen somewhere :

In the future (sometime around when our sun gets swollen and people have made it possible to somehow survive on Earth still):
Man 1 is sticking a marshmallow to the sky.
Man 1: Did you know that people used to cook their marshmallows above a fire?
Man 2: You're kidding me!
Man 1: Nope. They musta been crazy.
Man 2: Did they ever roast squirrels over fires?
Man 1: I think so...
Man 2 then sticks a squirrel on a stick
Man 2: Well too bad for them cause those crazies never knew how great a squirrel tastes like in the sun.

Mmmmmm...roasted humans...yum!

Oh wait, that's cannibalism...oh well! Too bad for them.

RUN!

Wait! Come back! I just wanna eat you! That's all! It won't hurt!

Hmmm, when's the sun gonna go white dwarf and then pull off a reverse Michael Jackson and go black dwarf?

WildMoon wrote:Hmmm, when's the sun gonna go white dwarf and then pull off a reverse Michael Jackson and go black dwarf?

Interesting way of putting it...

Give it a few trillion years. It takes a VERY long time for a white dwarf to cool down.

Malenfant wrote:

Hunter Parasite wrote:Actually, by the time the sun reaches the red giant stage, the earth and moon will not be swallowed by the sun because it waas born of a nebula with a solar mass less than 20 so when it reaches it's red giant stage it will not be large enough to get Earth, only mercury and venus will be swallowed.

Actually the jury is still out on that. It seems likely that Earth will still be destroyed by the sun since the red giant's surface will be very close to Earth's orbit and we could be caught in its extended atmosphere which can reduce our orbit by drag effects.

Either way, earth will be roasted completely. Whether it's actually destroyed or not is irrelevant really.

I read somewhere that even Venus could survive the sun's red giant stage.

As the sun slowly loses mass, the orbits of the planets may stray farther from the sun, a side effect caused by the sun's gravity decreasing, so when the red giant stage comes along Earth and Venus will be in a safer position.

Darn, so much for roasting marshmallows and humans under the sun when it gets bloated.

Michael Kilderry wrote:As the sun slowly loses mass, the orbits of the planets may stray farther from the sun, a side effect caused by the sun's gravity decreasing, so when the red giant stage comes along Earth and Venus will be in a safer position.

The sun would lose about 0.3 solar masses between the subgiant phase and the time it sheds its outer layers to form a white dwarf. I don't know if it'd lose it quick enough to allow the orbits to expand before Venus and Earth got engulfed though.

Certainly they'd expand AFTER it becomes a white dwarf but it may be too late by then.

Indeed, human life will be impossible on Earth before sun become a red giant... The temperatures will rise during the next billion of years, overheating exposed sediments, so the cycle of carbon will be stopped, and every life on earth will die because of lack of CO2... Funny isn't it, in this period of overheating greenhouse effect ?