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3

I actually answered a related question a couple of days ago on Astronomy. Small world! One of the important properties of the Oort Cloud is that objects in it are not strongly influenced by the Sun. After all, its inner edge is roughly 2,000 AU away - 300 billion kilometers from the Sun. The Sun's gravitational influence in that region is rather weak, so ...


1

If you take something like Neptune and pass it through Earth's orbit perpendicular to the ecliptic so it collides directly with the Earth-Moon system at, lets say, 0.1c you would remove the Earth rather quickly. Get another if you want to disappear the moon as well. Neptune isn't so big that it would disturb everything else, maybe a wobble in Venus or Mars ...


9

If one of the rules to be a planet is that it needs to clear ALL objects from their orbit, does this also make Neptune a non-planet? This is a somewhat common misconception of the meaning of the term "clearing the neighborhood". None of the planets could be called "planets" if clearing ALL objects from the vicinity of the orbit was what that term meant. ...


4

"To clear an orbit" has a specific meaning which may not entirely intuitive. "Clearing an orbit" specifically does not mean emptying an orbit of all other bodies. It means the planet gravitationally dominates other bodies at approximately the same distance to the sun. Now you can wonder perhaps whether Neptune dominates Pluto or Pluto dominates Neptune. ...


8

Neptune actually is the dominant gravitational force in the region of the Kuiper belt in which Pluto resides. In fact, if you look at the image below, the belt is being cleared out by Neptune: In fact, there is a class of objects, suitably named the plutinos, that have been captured by Neptune. Solar system models have actually shown that Neptune was ...


4

I did some research and I think I can answer my question myself now, after all. I hope you find it interesting. As it turns out, the technology of the Kepler space telescope would indeed allow detection of all Solar system planets except Mercury and probably Mars, i.e. all of them are big enough to be seen by it from a distance of about 2,000 ly. However, ...


0

Well the light which is reaching there now, the light which is being detected by a telescope set up in the Kepler planets was emitted from the Sun's solar system 2000 years ago since light took 2000 years from here to reach Kepler planets. So any event which occurred 2000 years ago in our solar system will be visible now in the Keplers. If we are (somehow) ...


0

TL;DR version The ICRF +x axis is more or less the direction from the Earth to the Sun at the vernal equinox, or about March 20. Six months later, the direction from the Sun to the Earth is more or less along the +x axis. Keep reading! A bit of a taint of the ancient concept of a geocentric universe remains in modern astronomy. How astronomers specify ...


3

Rev 2: Partially finished, but now I have Saturday chores to do. I'll finish filling in this outline later this evening. A number of planetary formation simulations from late in the 20th century to early in the 21st century suggested that Mars should be at most a bit smaller than Venus or Earth. This obviously is not the case. Explaining this is the ...


0

A very late answer, one that I hope adds to the excellent answers by Mark and LuboŇ°. From the perspective of Newtonian mechanics, there's nothing wrong per se with using a geocentric point of view. Such a point of view does require adding fictitious forces and torques that would otherwise be absent in an inertial perspective, but if makes sense to do that, ...


1

Besides Mars having a weaker gravity field than Earth, it also has a much weaker magnetic field. Therefore, Mars' atmosphere was not protected from the solar wind. NASA scientists put forth the theory that the small sparse magnetic field that Mars does have actually helped the solar wind to drive off the atmosphere. ...


5

How far ahead can we predict solar and lunar eclipses? NASA has uncertainty calculations that show how certain we are about when eclipses happen. From a back of the envelope, the eclipses will likely vary by a full day 35 thousand years from now. That said, we have eclipse seasons, so we know eclipses will continue to happen, and at roughly which time of ...


49

On predicting planetary orbits A number of studies have shown that the inner solar system is chaotic, with a Lyapunov time scale of about 5 million years. This 5 million year time scale means that while one can somewhat reasonably create a planetary ephemeris (a time-based catalog of where the planets were / will be) that spans from 10 million years into ...


1

Look I know link only answers are terrible, but I don't want to ruin the surprise. Check out this link. That's on Wikipedia! It's safe to say that if wikipedia knows something, the experts know quite a bit more. We know the dynamics of the Sun-Earth-Moon system really well including the perturbations and the most likely sources of future upsets, so barring ...


-2

Given that we exist at all, we can confidently back-track the positions of the planets (and our moon) for a couple billion years. I see no reason, barring rather massive exo-system-sourced objects showing up unexpectedly, that the positions will go chaotic enough to be unpredictable any time in the next couple billion years. I suppose it might depend a bit ...


7

The main reason Earth still has its water and Mars doesn't is gravity. Earth is big enough so that typical thermal speeds of hydrogen in the upper atmosphere don't get to escape velocity. On Mars, this is not the case, Mars having significantly less mass and therefore lower escape velocity. As a result, over a long time, much of the hydrogen that was ...


23

A slightly simpler version of David Hammen's (as usual excellent) answer: Earth is "big enough" to have sufficient pull on the atmosphere: gravity stops it from escaping Earth is "close enough" to the sun to keep liquid water (and liquid core) Core is sufficiently magnetic that it acts to protect against solar wind (which would otherwise strip the ...


56

The Earth's climate isn't quite as stable as you think. The Earth's climate has toggled back and forth between a greenhouse Earth and an icehouse Earth for the last 600 million years or so. During the icehouse Earth phases, the climate can enter an ice age, an extended period of time during which the climate in oscillates between glaciations and ...



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