Are the Planets moving away from the Sun?

eagledare · Sep 21, 2006

I saw on a web site that Earth's orbit is getting longer with almost 50 meters every year. Is it true? If you move Mercury closer to the Sun will it orbital rotation be the same as it's axial rotation?

nexium · Sep 21, 2006

There are several mechanisms that may cause the length of Earth's orbit to get longer or shorter. Most measuring methods are plus or minus a kilometer or so, so my guess is we do not have confirmation for a net increase or decrease. Likely Mercury has had a constant ratio of day to year, for thousads of years and the ratio has low probability to change in the next 1000 years. Neil

vogon13 · Sep 21, 2006

There would be a few factors to consider. The sun converts (IIRC)~4 million tons of mass per second to energy, as it dissipates into the void, the earth would experience less attraction to a now less massive sun. The sun is also still accreting the occaisional comet (check the SOHO coronograph pics for some interesting views of this). I wouldn't be surprised if the sun snarfs an asteroid once in a while too. Both these mechanisms, as long as they are consuming materials that originated outside earth's orbit would increase the sun's mass and gravity and contract earth's orbit a bit. The sun is also radiating an additional 400 watts per second (IIRC) over and above the amount released by fusion reactions due to (theoretical) proton decay. For the short time scales experienced so far (<5,000,000,000 years) this is a tiny mass loss, but over longish spans of time (~~10^50 years) the effect could greatly enlarge earth's orbit. The earth as it moves around the sun is also generating gravitational radiation. This is a weak and slow process, but again, over longish time scales (yeah, ~~10^50 years) it will tend to contract earth's orbit about the sun. The sun is also intercepting intergalactic dust and gas. This will increase the mass of the sun a bit. The sun also produces a steady stream of gaseous efflux (the solar wind) which tends to decrease the mass of the sun. How does all this add up? I dunno. <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

search · Sep 22, 2006

1,5cm per year (just one of many calculations) http://curious.astro.cornell.edu/question.php?number=317 http://en.wikipedia.org/wiki/Orbit#Orbital_decay http://www.supermemo.com/articles/users/earth_files/index.htm http://solar-center.stanford.edu/FAQ/Qsunendstate.html

billslugg · Sep 22, 2006

vogon13 I'm interested in your comment about anomalous radiation due to proton decay. This 400 watts (not watts per second) is based on theoretical considerations. Has proton decay ever been observed, or is it too theoretical? <div class="Discussion_UserSignature"> </div>

vogon13 · Sep 22, 2006

All of my protons are fine. <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Sep 22, 2006

A little more seriously, IIRC, protons are demonstrated stable out to 10^30 years or so. Beyond that ? ? ? ? ? ? <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Sep 23, 2006

I mentioned time scales of 10^30 to 10^50 years. Blow it out your asparagus. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

spookikiwi · Sep 3, 2007

my g/f told me the same thing, some cr*p she saw on tv about the earth moving away from the sun, i laughed so hard i fell off my chair & nearly wet my pants! i can understand where someone would imagine this theory, after all, the universe is apparently still expanding, a by product of the bigbang balhblahblah,, but if the earth was slowly drifting away, (even at the smallest increments), the earth has supposedly been evolving for something like 4 billion years, now add all those little numbers up.. suddenly the earth was too close to the sun to do any evolving & now we would be too far away to survive(& eventually we would be traveling so fast we would become a meteor, or comet or something), after all, the further we get from the sun, the less the suns gravity has an effect on us also, allowing us to start moving away more rapidly, increasing that annual distance bit by bit each year, (i.e it might have started at 0.005mm/year, but 4 billion years later, with less effect from the suns mass it could increase to 0.5mm/year [hypothetical figures for sake of discussion]) there is the possibility that our surfaces are getting further apart, due to the suns apparent shrinking, but the center to center distance, i would be willing to gamble is the same. i think somehow we have managed to stay suspended at this perfect distance by some magically wonderful chance of fortunate luck, or design, ...depending on what you believe.

willpittenger · Sep 3, 2007

<blockquote>In reply to:<hr />There would be a few factors to consider.<hr /></blockquote> One more. You forgot the Roche Limit. I don't happen to know what that is for the Sun. However, I would have to believe that it is closer to the Sun than Mercury. So all planets would be pushed away from the Sun by its gravitational tidal forces. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

datalor · Sep 3, 2007

If your girlfriend asked you a question and you "laughed so hard you fell off your chair and nearly wet your pants" you are lucky to be alive to post. People tend to not take it kindly when they ask a question and get ridiculed for it. For one it makes them feel stupid, and probably wont want to ask anymore questions. Real nice. Hope if you have kids you dont laugh at them if they question things. <div class="Discussion_UserSignature"> </div>

nexium · Sep 3, 2007

I agree: Be smart and tactful when you hear a dumb question as you may be the one poorly informed. The mainsteam opinion is the Universe is expanding between the clusters of galaxies, but we cannot measure the picometers that a meter stick might be increasing in length. One micrometer per year for 4 billion years is only 4 kllometers closer to the sun, so Earth would not have been hotter then, as we think the sun produced less energy 4 billion years ago than now. Neil

brellis · Sep 3, 2007

hi D'lor Ten years ago, I committed the Cardinal sin of laughing at an innocent, naive question my g/f asked. I was really into her, but she dumped me, in part because she felt insecure about her intelligence *-she was blonde, after all <img src="/images/icons/wink.gif" />-* Losing her remains one of the most painful things I've ever experienced. So, spookiwi, heed the advice of the sage, *~blonde!~ Datalor! <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

CalliArcale · Sep 4, 2007

I had to bite my tongue last week when my mother (who was two courses away from a master's degree in physiognomy when she left school to become a stay-at-home mom) asked me whether dogs have bellybuttons, and where they are. <img src="/images/icons/tongue.gif" /> I just barely managed to say "Yes, on their bellies," without laughing. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

yevaud · Sep 4, 2007

I have a lady friend from High School who once asked me - dead serious - who this guy "ibid" was, and boy he sure seemed to write a lot! <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

MeteorWayne · Sep 4, 2007

Well, I can't pass this up <img src="/images/icons/smile.gif" /> ibid 200 quatloos!! <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

spookikiwi · Sep 5, 2007

ok, to make it clear, i may have exaggerated slightly on my response to my g.f question. as it has been pointed out, i would be lucky to be alive if that was my response, (she woulda fair smacked me right in the nose, & probably a few other places too, & set me moving at high speeds away from the sun)

spookikiwi · Sep 5, 2007

sure, one micrometer only equates to 4Km in 4By, but 4Km is a lot, whats the distance difference from sun:equator & sun:london(for example) & theres a Huge temp difference. not to forget, (& feel free to correct this if its wrong, i think i've read it correctly) F=Gmm'/rÂ² or basically, the further away from the gravitational field, the weaker the gravity becomes, so it would actually be much further than 4Km. p.s i was lucky stumbling across that equation, & found it by chance, dont expect me to be able to pull those out all the time

Saiph · Sep 5, 2007

Actually the habitable zone around a star isn't nearly that small, or sensitive. For instance, the earth's orbit is slightly eccentric, at ~2% variance. At closest approach (perihelion) the earth is at ~147 million km from the sun. At the furthest approach (apahelion) it's at ~152 million km. So a 5 million km variance. Overall surface temperature between these two points varies by about 5% IIRC. Though due to reflectivity and the heat capacity of land masses vs water, the earth is actually warmer during apahelion, not perihelion. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

spookikiwi · Sep 6, 2007

soo, if the earth rotates around the earth eccentrically, & it takes a year to do so, then, roughly a 3 month cycle the earth get closer to the sun until it reaches its closets point of 147mil Km, but colder. (& then 3 months going further away) and if the earth has a tilted axis, which hemisphere is closest to the sun during each of these cylces..? (serious question) i would imagine that would create one hemisphere to have significantly colder winter & hotter summers than the other hemisphere, although that idea is probably useless if the earth is infact colder when its closer

MeteorWayne · Sep 6, 2007

The northern hemisphere is colder when the earth is closet to the sun, because the axis of rotation of the earth points away from the sun (at the north pole) The point where the sun is overhead has a much larger effect than the small changes that occur due to the eccentricity of the earth's orbit. It has much larger effects as far as enrgy input to the surface. Remember, south of the equator, it is warmer when the earth is closest to the sun <img src="/images/icons/smile.gif" /> The reason still remains the tilt of the earth's axis, but I'm just pointing out that those down under see January, when we are closest to the sun, as the hottest time of the year. The difference in energy between the closest and furthest seasons is very small. And since the southern hemisphere has a much smaller percentage of land than the northern hemisphere, the effects are very smoothed out. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

wurf · Sep 6, 2007

Does the expansion of space take place uniformally throughout all space, including within our solar system? If so wouldn't it have the effect of making the planets' orbits longer?

SpeedFreek · Sep 6, 2007

The theory goes that the expansion of space only happens outside of gravity-bound systems, i.e. in the large gaps between galactic clusters that aren't bound by gravity. It seems that where any gravity (or other attractive force at smaller scales) is at work between multiple objects, that force stops the distances between those objects increasing. <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

Mee_n_Mac · Sep 6, 2007

The theory goes that the expansion of space only happens outside of gravity-bound systems... Is it that the "force" isn't present or that it is present but in such a minute quantity that gravity overwhelms it ? <div class="Discussion_UserSignature"> -----------------------------------------------------Ask not what your Forum Software can do do on you,Ask it to, please for the love of all that's Holy, STOP ! </div>

SpeedFreek · Sep 6, 2007

Well that's the question I cannot get a decent answer to, which is why I worded my reply that way! I asked the same question, and even proposed a model where the expansion happens everywhere and any local forces override it, but on the microscopic scales, atoms might settle to an ever so slightly different size depending on the rate of expansion. I asked on an alternative site that is quite strict about models that stand against the mainstream, but nobody had a definitive answer either way, as my model is strictly unfalsifiable due to our rulers also being affected! <img src="/images/icons/wink.gif" /> All we can say is that distances seem to be increasing at the largest scales, as the objects all seem to be moving away from us, but locally, galaxies closer to us can be moving towards us. <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

Are the Planets moving away from the Sun?

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