Why is the earth's core hot and other planets core not hot?

Question

Why is the earth's core hot and other planets core not hot?

Answer 1

Lots of planets have hot cores.

Contrary to popular wisdom - Jupiter does have a solid core and it's ~20000K!

All the planets and moons should have started out with hot interiors, but the energy contained in a planet is proportional to its volume, while the flow of energy out into space (cooling) is proportional to the surface area through which it can flow.

Consequently, the cooling rate is slower the bigger a planet is.

This is why Mars, Mercury, the Moon etc have cooled off to the pointed of having solid cores.

Venus is a bit of a mystery. How do we determine whether it has a hot core? It's about the same size as Earth, so it should still be hot. Problem is that it spins slowly, so we can;t use its lack of magnetic field as evidence (you need the molten core and a fast spin to get the magnetic field generated.)

Answer 2

They are hot, or at least most of them are. Mars, for example, used to have a much hotter liquid core that caused a magnetic field, but because it is smaller then Earth it cooled quicker and the core is now solid, so it has lost its magnetic field.

Answer 3

many other planets have hot cores - for example mars had a metallic core like earths but its much smaller and cooled faster.

also the earth has the moon whose gravitational pull also cases friction and heat to add to the core - the earth is cooling down but slowly due to its size and the effect of the moon.

this stabilises our planet and its magnetic field allowing life to develop here without being affected by the solar rays.

Answer 4

Chemical reaction between the uranium and something else in there gives of heat as a by product. I#m not sure know what that other thing is though. Hydrogen?

Answer 5

The Sun is delivering thermal energy to the planet all the time...and even so, in the creation process of the earth...the hot core's life could be extended this way...as well as the spinning of the earth could keep it from cooling off.

Convection currents in the mantle...it's always moving...therefore extending the heat....if the convection currents turned off, then the core would start to solidify...the mantle with it...that would mean the earth is not spinning either.

A precursor to life...is to have a planet which turns in space on an axis around a star.

Our moon doesn't turn...it always facing us...one of it's sides...so it must be completely devoid of thermal heat inside of it.

Answer 6

I believe That it is two things. One The earths flux has positive and negative flows running through it. The other is that The flux of the earth, when in line with it's neighbouring planet, Is opposite to the neighbouring and there for the opposing lines of flux cause friction and heat each others cores.

Answer 7

In the earths core it has two plates these plates rub together which makes friction...friction makes heat therefore these plates makes the earths core hot..also if these plates cause to much friction they will cause things such as volcanoe eruptions and tsunami's.

Answer 8

well earth has diffrent layers that we know of.

jupiter and some of the other planets are made up of gas so there is no solids there.

the other solid planets havnt all been visited so we dont know much about there layers and stuff

Answer 9

the others are as well, Jupiter for example is even hotter and gassier, it is a gas giant, like me. lmao

Answer 10

No one knows for sure why the Earth's core is hot, except I've got my own pet theory - at least It's a sort of theory.

Pet Theory

Hot core = live volcanic action - as of a living planet.

Cold core = dead planet - probably little or no life.

Now for some real science. . . . .

Heat in the Earth's Core.

Evidence points to heat being caused by friction during the creation of planets. ... It is not known why the earth's core is hot, but there are lines of evidence. ...

http://www.nov55.com/heat.html

The only other planet which we know anything much about, is Mars.  NASA are there right now - not sure if they've found anything or if they will.  From past experience my guess is that no amount of digging will find any life.  It's just too cold.

As for the core of other planets within our own solar system, I'm not sure they do have cold cores or not.

Nine Planets: Mars

Sometimes referred to as the Red Planet, Mars is the fourth planet from the Sun ... The most likely scenario is a dense core about 1700 km in radius, a molten rocky ...

http://www.nineplanets.org/mars.html

Exploring Mars: Educational Brief

Despite these signs of ancient water, Mars now is too cold and its atmosphere ... The data for Mars indicate that its central core is composed mainly of iron and ...

http://www.lpi.usra.edu/expmars/edbrief/...

Jet Propulsion Laboratory

Tour JPL with our new Virtual Field Trip site. Stops include ... Orbits sun around the north and south poles. + Mission home page + Other Solar System missions ...

http://www.jpl.nasa.gov/solar_system

Solar System Exploration: Planets: Comets

... from the formation of our solar system around 4.6 billion years ago. ... as long as 30 million years to complete one trip around the Sun. (It takes Earth ...

http://www.solarsystem.nasa.gov/planets/...

APOLLO

http://www.youtube.com/watch?v=t1xzPGyt4...

Answer 11

Some planets do have hot cores others were hot but have since cooled. The heat comes from the energy absorbed from collisions when the planet formed under the influence of gravity and radioactive decay.