Why Won't Earth Fall into the Sun?

  • Thread starter FeynmanMH42
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In summary: Objects in elliptical orbits around a central point are said to be in equilibrium. There is no net energy loss in an elliptical orbit. If the planets were constantly orbiting the Sun, they would run out of energy and eventually fall into the Sun. However, the planets are in a stable orbit and don't lose energy.
  • #1
FeynmanMH42
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If the planets are constantly orbiting the Sun won't they eventually run out of energy, succumb to the gravitational pull and fall into the Sun?
They don't seem to be doing... why not?
 
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  • #2
Because gravity doesn't require energy for it to work. The gravity is always them same for the planets so that the work does not chage if there's no chage in work there's no energy required.
I think your going to need some other member to explain it better to you.
 
  • #3
FeynmanMH42 said:
If the planets are constantly orbiting the Sun won't they eventually run out of energy, succumb to the gravitational pull and fall into the Sun?
They don't seem to be doing... why not?


Stop and think.

What causes a system to lose energy? Things like friction, cooling losses of thermal energy, etc. But how is an object in orbit around the sun going to lose kinetic energy to friction (granted, objects in low Earth orbit do, but they're not really beyond the atmosphere, there is still a lot of matter there, and those objects are very light compared to say a planet. A system doesn't just 'run out' of energy, the energy has to go somewhere, that's the first law of thermodynamics. And in the case of planets in stable orbits around a star, there isn't a significant way to lose any energy.
 
  • #4
What is in motion will stay in motion until acted upon by an outside force.
Earth is in motion, there is no outside force.

Summary: Earth won't fall.
 
  • #5
But wait...dust in the solar system is a kind of friction to slow down the Earth. (Granted, it's a small effect...but acting over billions of years...plus, there's the increase in mass (again, small) of the planet which affects the gravitational interaction.)

Anyway, planets' orbits can and do change due to gravitational nudges from other planets, passing stars, etc. The interaction is complex...lose some energy here...gain some there...over and over throughout its existence. The current planets in the solar system are in what turned out to be the stable/safer orbits.

Unless something wild happens (rouge interstellar body messing up our solar system in the distant future?), the net energy loss should be negligible such that the end of the Earth won't be it spiraling into the sun but rather the sun expanding out to the Earth's orbit when it becomes a red giant.
 
  • #6
Simple orbital systems [e.g., binary neutron stars] do bleed off momentum via gravitational waves and can eventually collide. Absent external influences, as mentioned by other posters, it is theoretically possible the Earth could inspiral and eventually merge with the sun: albeit would take many billions of years [emphasis on many].
 
  • #7
Phobos said:
But wait...dust in the solar system is a kind of friction to slow down the Earth. (Granted, it's a small effect...but acting over billions of years...plus, there's the increase in mass (again, small) of the planet which affects the gravitational interaction.)

Anyway, planets' orbits can and do change due to gravitational nudges from other planets, passing stars, etc. The interaction is complex...lose some energy here...gain some there...over and over throughout its existence. The current planets in the solar system are in what turned out to be the stable/safer orbits.

Unless something wild happens (rouge interstellar body messing up our solar system in the distant future?), the net energy loss should be negligible such that the end of the Earth won't be it spiraling into the sun but rather the sun expanding out to the Earth's orbit when it becomes a red giant.

I'm not disputing that orbits can change under various influences. I'm disputing the form of the original question "Won't they run out of energy?".

That said, I would be surprised to find that any drag force on the Earth from the gases in the inner solar system was significant, even over the entire lifespan of the sun (with the possible exceptions of the planetary nebual phase, and the planetary formation phase, but even then I would still be surprised).
 
  • #8
Arian said:
What is in motion will stay in motion until acted upon by an outside force.
Earth is in motion, there is no outside force.

Summary: Earth won't fall.

The Earth is moving under the force of gravity. An object in motion continues in a straight line, unless acted on by a force. The Earth is orbiting in an ellipse.
 

What are the names of the eight planets in our solar system?

The eight planets in our solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

What makes each planet unique?

Each planet has its own unique characteristics, such as size, composition, atmosphere, and distance from the sun. For example, Jupiter is the largest planet and has a thick atmosphere made up mostly of hydrogen and helium gas, while Venus has a thick, toxic atmosphere and is the hottest planet in our solar system.

Are there any planets that could potentially support life?

Scientists believe that there may be potential for life on other planets in our solar system, such as Mars and some of the moons of Jupiter and Saturn. However, further research is needed to confirm this.

Do all planets orbit around the sun in the same direction?

No, not all planets orbit the sun in the same direction. Most planets in our solar system orbit in a counterclockwise direction, but Venus and Uranus rotate in a clockwise direction.

What is the farthest planet from the sun?

The farthest planet from the sun is Neptune, which is approximately 2.8 billion miles away from the sun. It takes Neptune about 165 Earth years to complete one orbit around the sun.

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