If earths velocity is what keeps us in orbit then if we slow down do we fall into the sun? Are we slowing down? And if not why not? Isn’t there a tiny fraction of friction in space that might slow us down eventually? It seems so unlikely that we would enter the solar system so perfectly that we would start to orbit. Have there been a thousand planets before us that just missed the mark or is there something keeping us on track?
In: Physics
No we won’t fall into the Sun instead the Sun will expand into us. When the Sun changes from fusing hydrogen to fusing helium that generates more heat and energy than before which will cause the Sun to dramatically expand to a point where the outer edge of the Sun is approximately where the Earth’s orbit currently is. https://youtu.be/64L0Dv55_Cw
Technically yes, we are slowing down. Space after all is not absolutely empty, there is stuff to slow us down out there – just very little of it.
However, the amount we are slowing down is so infinitesimally small that the Sun will expand and consume the Earth long before we would notice any change in orbit.
In order to hit the Sun we would need to slow down by tens of thousands of mph.
No, we are not slowing down, because yes, there is no friction in space. What would there be friction against, anyway? We didn’t “enter” the solar system with the right speed to orbit, we didn’t even really “enter” the system at all. We formed with the rest of the solar system out of a cloud of already spinning gas and dust.
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While there is only one perfectly circular orbit (for each radius) , there’s actually a range of stable elliptical orbits. We’re in one of them. There are only a couple of ways Earth’s orbit could change.
One would be impacts from other objects such as meteorites, photons, and stray protons. As others pointed out, there really aren’t enough asteroids in our solar system to push us out of a stable orbit. And while stray protons do have momentum, the Universe would end long before they’d have any significant affect.
The other major factor that could change the Earth’s orbit would be tidal forces between the Earth and Sun. The mass of the Sun is so large that again the Universe would probably end first. And even if it didn’t, the Sun surely will
Edit: specified perfect circular orbits
Considering it’s been there for billions of years… pretty stable.
It’s not easy to fall into the sun from orbit. You have to have a high angular velocity relative to the sun to be in orbit in the first place. Canceling out a planet’s orbital velocity at once would take an immense amount of energy… nothing short of a planetary collision, at which point, falling into the sun isn’t as much of a worry as the planet being utterly destroyed– but if it was just the right impact, all the pieces would fall into the sun or rain down on the inner planets.
A better way of thinking about this isn’t that Earth was some random floating rock that happened to get captured by the sun. Earth was formed over billions of years as gas and dust settled together under the forces of gravity around a similar distance and velocity around the sun. Anything that was slower and closer to the sun helped to form Venus. Anything that was faster and farther away helped to form Mars. Our orbit is stable because that is the very nature of planetary formation.
But isn’t true that our galaxy is moving through space? So these aren’t just stationary orbits, but elliptical orbit around something that’s also moving. I’m only asking as I didn’t study astrophysics at university. Very interesting
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