# If the Sun disappeared (?) Imagination exercise.

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#### ace5

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How long until we notice the effects os its 'absence'?<br /><br />Its light would dim after 8 minutes, but what about its gravitational pull? Also 8 minutes?<br /><br />

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#### derekmcd

##### Guest
We really don't know much about gravitational waves and how they propogate or the existence of the graviton. The current thought is they propogate at the speed of light.<br /><br />LIGO is currenty testing these theories.<br /><br />So, if they do travel at the speed of light, then, yes... the effects would not be noticed for 8 minutes.<br /><br />The real answer is, though, nobody knows. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

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#### billslugg

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Even if the mass of the sun disappeared instantly, it could only be converted into energy. The equivalent energy would have the same gravitational force as the mass did. No? <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

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#### MeteorWayne

##### Guest
If it was converted to energy, we'd be such toast, it would be a moot point <img src="/images/icons/smile.gif" /><br /><br />If I understand things correctly (not guaranteed) since gravity is a property of space/time the effect should propogate at c.<br /><br />However, to my knowledge this has never been measured, only theorized.<br /><br />When we detect some gravity waves (or if) maybe we can verify that. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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#### newtonian

##### Guest
ace5 - Since this is an imagination exercise, we can imagine the sun could simply disappear - but as the above posters correctly noted - this cannot actually happen.<br /><br />I suspect that if the speed of gravity is not exactly the same as the speed of light, that it is very close - so close we would probably not notice it.<br /><br />Even a very slight difference in speed, however, would have profound effects on the acceleration rate of the expansion of our universe.<br /><br />And that would also be true if the speed of light is almost constant while the speed of gravity is exactly constant - or vice versa.<br /><br />Another interesting imagination exercise in harmony with your thread theme would be: how fast would earth cool if the sun disappeared?<br /><br />This could have real applications in future trillions of years as earth's sun cools during white dwarf to [black?] dwarf stage.<br /><br />And could we insulate earth so that we could survive near the core - utilizing geothermal heat, tidal effect energy and radioactive decay energy for a googolplex years?????<br /><br />I have in mind planet Altaire 7 in the Sci. Fi classic "Forbidden planet" whereby the superior intelligence civilization produced by the Krell harnessed the core energy of the planet.<br /><br />Just an additional imagination exercise.

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#### MeteorWayne

##### Guest
Two tweaks again <img src="/images/icons/smile.gif" /><br /><br /><font color="yellow"> "This could have real applications in future trillions of years as earth's sun cools during white dwarf to [black?] dwarf stage. " [</font><br /><br />Remember we will be well incinerated before then, since as the sun expands to red giant stage, we will be inside the "surface"<br /><br /><br /><font color="yellow"> "I have in mind planet Altaire 7 in the Sci. Fi classic "Forbidden planet" whereby the superior intelligence civilization produced by the Krell harnessed the core energy of the planet. " </font><br /><br />It was Altair 4.<br />It's one of my top 5 favorite movies. <img src="/images/icons/smile.gif" /><br /><br />MW<br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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#### qso1

##### Guest
The sunlight would dissapear in 8 minutes. We would not notice this simply because to us, it would occur real time from our perspective. But we would know the event had begun 8 minutes prior to our becoming aware of it. Especially interesting would be people on the night side of earth looking at a full moon and watching it dissapear. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

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#### derekmcd

##### Guest
<i>"But we would know the event had begun 8 minutes prior to our becoming aware of it."</i><br /><br />How so? I imagine SOHO might begin recording the events prior to our awareness, but SOHO could only transmit the info to us as fast as the event itself would travel towards us. I think unless gravitational waves propogate instanteously, there would be no physical way of knowing faster than the speed of light.<br /><br /><i>"Especially interesting would be people on the night side of earth looking at a full moon and watching it dissapear."</i><br /><br />Indeed. Truely an oddity that would be. There one second and in a blink of an eye... <br /><br /><br />gone. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

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#### qso1

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The general public at large I would bet you is completely unaware of SOHO. Sure they may have seen it on CNN once in their life but as with most things space, they are not automatically going to know anything happened until they see it because of their lack of awarness about spaceflight in general. If SOHO were named after an entertainer or athlete, more would probably know.<br /><br />I didn't factor gravity in but I would say earth would still have gravity since it has mass and it would simply no longer be gravitationally bound to the sun but we'd still feel earths gravity. There again, we wouldn't know that instantly until we knew the sun had disappeared in which case the astronomical community would be able to sort of predict what will happen next and advise of possible gravitational anomalies. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

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#### derekmcd

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Certainly, Earth would still have gravity. We would still be bound to the earth. I would definitely be interested in seeing some mathematical models of what would happen in a situation like this. <br /><br />Not counting the the lack of light/heat and the detrimental effect that would have on our ecosystem... we humans would likely not even notice much, if any, gravitational effects (or lack there of) other than minor changes in the tides.<br /><br />It would be interesting to see how long the Earth/Moon system would remain stable.<br /><br />No doubt the earth and moon would be flung out of the solar system (i guess after the sun is gone it would be renamed the Jovian System). What would happen to the symbiotic relationship between the Earth and the Moon?<br /><br />Is Jupiter massive enough to keep the system from being flung apart in different directions? Or, would Jupiter just pull together the relatively close objects and build its own system? Habitable?<br /><br />How quickly would the greenhouse effect on Venus be reversed? How long after cooling could life be supported (if at all).<br /><br />Would it end the debate on referring to Pluto as a planet? (pathetic attempt at a joke)...<br /><br />Anyway... some questions to ponder. <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

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#### MeteorWayne

##### Guest
I don't think Jove would save us, since it's only 0.13% of the solar system mass, and is much further away than the sun. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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#### dragon04

##### Guest
IIRC, conventional thought is that gravity is propogated at <i>c,</i> in which case, it would take 8 minutes and 30 some odd seconds for Earth to fling itself off on a more or less straight trajectory towards the Great Beyond.<br /><br />It brings up interesting questions about the fabric of 4 dimensional space-time. If I take a thin sheet of rubber, and put a bowling ball in the center of it, it creates a depression much like a gravity well.<br /><br />Now. Given that the depression is more or less constant and unchanging, I can take a golf ball, and determine how fast it has to go round inside that depression for it to find it's "orbit" where it will not fall into the bowling ball or fling itself out of the depression entirely, although friction between the rubber surface and the golf ball has to be taken into consideration.<br /><br />In my model, the bowling ball stretches the rubber sheet which means that due to its elasticity, the rubber sheet is storing increasing amounts of kinetic energy as we get closer to the bowling ball in our "well".<br /><br />In other words, if we have say three objects at varying distances relative to the bowling ball "orbiting" around the interior of the depression, if we had Scotty beam the bowling ball out, the rubber sheet would impart differing energies on the orbiting balls as it moved to assume its normally flat nature.<br /><br />So balls closer would be moving faster, and would be flung at a higher velocity than the balls farther out.<br /><br />In 3 physical dimensions, space doesn't appear to have the same qualities; otherwise, the planets would not so uniformly orbit on or close to the Ecliptic, I wouldn't think.<br /><br />To me, this infers that the "gravity well" of a body is expressed "outside" of the three physical dimensions. I know I'm digressing, and also am speaking from a laypersons POV, but if that's the case, I can's be sure that gravity is propogated at <i>c</i>.<br /><br />A wormhole would be an example of the difficulty I <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

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#### newtonian

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Dragon04 - I'm not so good at that space/time fabric, gravity wells and all.<br /><br />A bounce effect sounds like what you are saying.<br /><br />I am not aware of any mass disappearing through a wormhole - excvepting worms and soil in my garden - that is.<br /><br />I do agree our velocity will propel us out into space and I do not know if we will end up gravitationally bound to Jupiter - it would depend on the relative positions in the orbit at the time of disappearance and the resulting trajectories of earth and Jupiter.<br /><br />Obviously it would be unlikely.<br /><br />

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#### newtonian

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MeteorWayne - May I tweak one of your tweaks?<br /><br />Earth may not be within our sun's red giant surface - see my thread on surviving red giant phase.<br /><br />There are very variant models. It depends not only on the actual predicted size of our sun in red giant phase but also the future orbital position of earth.<br /><br />Some reasons for the variance:<br /><br />Our sun will lose mass as it progresses to red giant phase, which will, in turn, cause planetary orbits to recede. How much depends on how much mass is lost.<br /><br />One reason the mass loss is uncertain is that the standard model of stellar evolution indicates zero mixing from core to surface in our sun - but that ignores the causes of the magnetic dynamoes floating possibly from core to surface and then causing the extreme heat of our sun's corona. It is not known how different our sun's corona is from the average main sequence star of our sun's mass.<br /><br />Obviously, any mixing will delay our sun's entry into red giant phase and will also cause our sun to lose more mass which will put earth in a more distant orbit at red giant phase.`<br /><br />I will try to bump my threads on this.

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#### qso1

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derekmcd:<br />How quickly would the greenhouse effect on Venus be reversed? How long after cooling could life be supported (if at all).<br /><br />Me:<br />Good questions. I picked this one because I suspect Venus would cool down to be sure, but it would never have the chance to develop life because it would cool down like us and the rest of the solar system to well below freezing. This isn't a problem for Jupiter and beyond. Or mercury, but for Venus, Earth, and Mars, the effects would be the most noticeable.<br /><br />Venus would probably take the most time to drop in temperature but doubtful it would be long enough to allow life to take hold. The CO2 atmosphere would be something like dry ice.<br /><br />But then again...I can't know how these effects would actually play out for sure. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

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