Planets Definition and 510 Threads

can anyone tell me how planets form and how we know that life can only exist in an environment where there is liquid water. is it possible that we only know how to observe or measure lifeforms we have previously encountered?:confused:

How exactly is this done? Is it done in the visible wavelengths or in the radio? Also, how small can the (planet size)/(sun size) ratio be. I'd expect that given noise especially, there's a definite lower limit.

If your on a planet that has 4x as much mass as earth, but only 2x the diameter, would you weigh 4x as much as you do on earth? Does the diameter of the planet even matter? or is it only the mass that affects how much you weigh. Thanks

Finding weights on other planets URGENT yeah, here comes a homework problem my class had that both me and my friends couldn't get. please help us :bugeye: A bag of sugar weighs 5.00 lb on earth. what should it weigh in Newtons on the moon, where the free-fall acceleration is 1/6 that of...

A few weeks ago I saw a documentary that said that a rocky planets cannot exceed 14 times Earth's size, because any bigger than this it will collapse and cannot stand. Why is this? Also, how many times bigger are Jupiter, Saturn, Uranus, and Neptune? I know they are much bigger than 14...

I know why planets revolve around the sun. But why do they rotate on their axis?

An article about the likely magnitudes and feasibility of terrestrial sized rocky planets orbiting in the habitable zones in the Alpha Centauri system: (link removed)AA http://www.publishedauthors.net/aa_spaceagent/

Why doesn't the immense gravity of Jupiter and the others turn the gases into solids? (More than just a tiny core, that is.) Does the "gas" at the surface act like a hard solid? About 10 years ago that comet, Shoemaker-Levy 9, entered Jupiter's atmosphere, broke up, and caused explosions on the...

Why do planets rotate around the sun? due to the gravitational field of the sun, which is obvious, but why do they not gradually crash into the sun, due to their motion and the loss of energy after a while :confused: ?

Here is my problem that I have partly solved. An astronaut visits planet x. She takes out a 50 cm pendulum and records a period of oscillation of 2 seconds. Then the astronaut visits planet y, takes out the same pendulum and records a period of oscillation of 1.5 seconds. Which planet has the...

Are live plate tectonics unique?

I've often wondered what a Type 3 Civilization could do if they had the technology to convert gaseous planets such as: Jupiter, Saturn, Neptune, and Uranus into matter. If they harness such energy, what would they use it for? To power up their starships, or perhaps create a solid rock planet for...

maybe we can use a thread about exoplanets discovered in the primary's habitable zone the harvard catalog is basic, and gives bibliography to the technical literature. here is a sample from the harvard catalog http://cfa-www.harvard.edu/~planets/Gl876.html for something a bit different...

Is plausible to use the magnetic field of an exoplanet to detect it? Since the field extends much more over space than the body planet it could be much more easy to detect with a radiotelescope i ever wondered if astronomers have not tried it already

Howdy first post. Why is it said that life needs water to develop. Everybody says that life hear came from the sees but why could it come from a methane sea? or even beyond that on a gas planet? Thanks Ryan

Sticking to our own solar system for the moment, aside from Earth, where else could we reasonably expect to find diamonds? According the the Columbia encyclopedia: "Diamonds are found in alluvial (loose earthy material deposited by running water) formations and in volcanic pipes, filled...

http://space.com/scienceastronomy/050405_earth_like.html

We all know that moon is under the influence of Earth gravitational force and vice versa. This force causes the circular motion of Moon (and Earth as well). Earth pulls Moon with a force F and Moon pulls Earth with the same force. This has occupied me a long time: Will Moon eventually fall down...

AKA solar systems rare?

1. Is it true that when the orbital plane of planets about a star is perpendicular to our line of sight, that we will not detect the star wobble they may cause? 2. How many degrees from perpendicular is star wobble is detectible? For this question, I will accept an answer based on currently...

When it comes to producing life (as we know it), I know that currently we are the only planet that we know that has produced life and life flourished. But compared to Mars which they say had oxygen but lost it too quick, or Venus which is most likely dead, or Mercury which is burnt to a crisp...

Tb / Ta = ? i have a final question, which is how do i find this. i know what the question is askin i just don't understand how to get the answer Two planets A and B, where B has twice the mass of A, orbit the Sun in elliptical orbits. The semi-major axis of the elliptical orbit of planet...

I have deep fascination with precious and semi-precious stones, as I do a lot of natural stone beadwork jewelry. There are so many beautiful stones (not just diamonds, rubies and sapphires either) that are on our earth, but someday may be completely gone. My question is, has there ever been...

The planet Zond 4(made up) has a mass which is one third the mass of the earth, and a radius which is one quarter of the Earth's radius. What is the accelerationdue to gravityon the surface of Zond 4? Thanks

Ok, this extra credit assignment is driving crazy. I keep trying to put it away and work on something important, but it can't get it out of my mind. The full question is: On the agonic line between Earth and Mars lies the agravic point with respect to the gravitational fields of the two...

I was wondering if it is possible for all of the planets to line up in one line? The Bob (2004 ©)

Do planets have actual lumosity or are they just lit up by stars? Might be a stupid question but I am just wondering. Thnx

Hi, How is a space probe planned to be fail-proof? And how is the trajectory calculated?Is it easy to do or requires huge calculations?

Alright, well this problem was too hard to explain, so I just decided to scan it ;). Here's the problem: http://img108.exs.cx/img108/5815/approb.gif I'm pretty sure I'll be able to figure out everything else once I get part (a). But I don't know where to start with this. Thanks.

Our bodies may require a gravity that is equal to that of Earth. If so, then it may never be possible to live on other planets. The future of humanity may therefore be in outer space, for example in rotating space stations. http://www.faqs.org/docs/Newtonian/Newtonian_91.htm Does...

How does fly-by works? How is it possible that after fly-by I have more energy than before? Where do I take it?

It seems that planets can not exists around twin-stars or even triple-stars. I mean that the planet orbits both stars, and not just one of the two/three. Why is that? The planet can just circle around the centre of gravity, what is so special about a twin or triple-star system?

In another thread: "When is a planet a planet?" https://www.physicsforums.com/showthread.php?t=46968 Someone mentioned that normally the outer planets in a solar system are gas-gaints and the inner planets are big "rocks". Why is that? Why can the gas-gaints not be the inner planets?

why does the velocity of the comet increases as it comes near the planets

I thought I did this problem correctly but when I submit my answer it says other wise. Here is the problem: The mass of a robot is 5440kg. This robot weighs 3610N more on planet A than it does on planet B. Both planets have the same radius of 1.33 * 10^7m. What is the difference M_{A} - M_{B}...

Just thought of this, probably no validity to it, but just a thought. Most planets start with hot cores, they eventually cool, and shrink. Their cooling and shrinking results in more plate tension on the surface because of the shrinkage. This would create more mountain ranges on planets. So...

"What caused the planets to aggregate as they did? What are the dynamics of gravity, that caused the plantets to evolve, progressively larger from Mercury to Jupiter and then progressively smaller Jupiter to Pluto? :confused: What are the dynamics of gravity, that caused the inner plantets...

This has been bothering me for some time, no one has a good answer to it. I read a while ago some information about the meaning of "planet" and it said that Pluto isn't a planet, that there are just 8 planets in our solar system. Why? I read that the meaning of "planet" is: A solitary body, for...

If the black hole has infinite capacity to store mass,why,in a case of the sucking up of the sun,why would their(crudely described)sunny-side up expel huge jet streams of flames and heat? Cant they absorb heat energy and UV since they have capacity to collect mass? If it is possible the Black...

Th eother day while surfing I found a list of the 120 detected extra-solar planets. (Minus the 2 super giants) Just for the heck of it I decided to take this info and plot to a graph. I decided to plot planet mass against oribtal distance. The graph is attached. I also plotted the...

It is said that most mass in the universe consists of dark matters which don't emmit light. What is the difference between dark matters and planets? Thank u.

1. What is the smallest possible self-gravitating, gaseous astronomical object? 2. What is the largest possible terrestrial astronomical object? 3. Does there exist a star-free, orbiting system of planets?

Is all the planet and star are round? If so, why when we look at star the shape is not round. If anybody ever think the star are actually shine through in between 4 rounds.

Does anyone know if there is a (short) technical name for a "Lunar day-night cycle" (28 Earth days)? We're afraid that simply saying "Lunar Day" might be misconstrued as the 14 day period which a site would be in the sun, and typing "Lunar day-night cycle" is becoming rediculous when it needs...

I was hoping that someone might give an insight to this on another thread concerning the moon, but no luck there. Can anyone give me a plausible reason as to why the planets rotate at their particular velocities, e.g. why does the Earth spin ~365 times per orbital revolution, or why does...

This might seem like a silly question to most of you but I’m going to ask it anyway. Why do all the planets orbit the sun?

http://www.ucolick.org/general/pressrelease/99/99-11-29.html The orbits of the new planets, like those of most of the extrasolar planets discovered so far, tend to be quite eccentric, tracing paths that are oval rather than circular. One of the planets, around a star called HD 222582, has...

? (lol)

Hi guys, Just a question if anyone has any insight to offer in theh notion that the planets of our solar system are some how counter balanced by "Phantom" plane on their opposite side of the sun? I heard some where of this? but it was along time ago If you have what are your thoughts on...

How do we find out the gravity of planets