# If you couldn't see planets or stars...

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#### Leovinus

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<p>If you couldn't see planets or stars and you had only the Moon and the Sun, how much longer would it take humanity to figure out that the Earth revolved around the Sun?</p><p>Same question, but now assume that the Earth has no Moon and the only thing in the sky is the Sun.&nbsp; From our point of view, it would just look like the Sun was suspended out there like a big light bulb.&nbsp; How long would it have taken for someone to figure out that the Earth revolved around the Sun?&nbsp; And I also wonder how much ridicule the first guy to suggest it would receive? </p> <div class="Discussion_UserSignature"> </div>

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#### cosmictraveler

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<font size="4">" <p>If you couldn't see planets or stars and you had only the Moon and the Sun, how much longer would it take humanity to figure out that the Earth revolved around the Sun?"</p><p>&nbsp;</p><p>This is a HYPOTHETICAL question and trying to "solve" this is only wasting time in my opinion. <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-tongue-out.gif" border="0" alt="Tongue out" title="Tongue out" /></p><p>&nbsp;</p><p>&nbsp;</p></font> <div class="Discussion_UserSignature"> <p>It does not require many words to speak the truth. Chief Joseph</p> </div>

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#### Leovinus

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>" If you couldn't see planets or stars and you had only the Moon and the Sun, how much longer would it take humanity to figure out that the Earth revolved around the Sun?"&nbsp;This is a HYPOTHETICAL question and trying to "solve" this is only wasting time in my opinion. &nbsp;&nbsp; <br /> Posted by cosmictraveler</DIV></p><p>So your answer is that you could never figure it out.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

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#### CalliArcale

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>So your answer is that you could never figure it out.&nbsp; <br /> Posted by Leovinus</DIV></p><p>Well, if your only clue was the Sun itself (no stars, no moon, no planets), you probably <strong>couldn't</strong> figure it out until you developed some alternate means of detecting stars and other planets, like radio astronomy, which is kind of cheating based on your original premise.</p><p>The clues for determining that the Earth goes around the Sun are all down to understanding the relative movements of Sun, stars, planets, and moon.&nbsp; Strip that away, and the model works just as well heliocentric as geocentric.&nbsp;</p> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"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."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

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#### Leovinus

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, if your only clue was the Sun itself (no stars, no moon, no planets), you probably couldn't figure it out until you developed some alternate means of detecting stars and other planets, like radio astronomy, which is kind of cheating based on your original premise.The clues for determining that the Earth goes around the Sun are all down to understanding the relative movements of Sun, stars, planets, and moon.&nbsp; Strip that away, and the model works just as well heliocentric as geocentric.&nbsp; <br /> Posted by CalliArcale</DIV></p><p>That was what I was thinking.&nbsp; And if the Earth wasn't tilted and you had no seasons, you'd have no clue how long a year was.&nbsp; Time would just be one day after another.&nbsp; No years.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

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#### l3p3r

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<p>Perhaps after curiosity takes hold mankind sends a probe off into space and observes it to fall in to the sun. Then we'd sure know about it </p><p>Also the mapping in 3D of CMEs or somesuch would allude the nature of the system. Processes such as gravity will still be well understood, and with the moon we have a local obvious example of the two body problem... Perhaps this happens to some civilizations stuck in deep, thick nebulae.... &nbsp;</p><p>&nbsp;</p><p>I for one am very happy with the selection of easy observations we can make that tell us about the universe! We are in a way very fortunate, however I would very much like there to be another (obviously) inhabited planet in our system.... maybe even with another sentient species ! ! </p><p>&nbsp;</p><p>But to answer your questions; I would say maybe 500 years or so... military development will most likely have necessitated going to space anyway, and then it's just a case of playing around until something goes askew! &nbsp;</p><p>&nbsp;</p><p>edit: actually - after thinking about that a bit more... I think it would be possible to determine the nature of the system just by observing the sun and moon for long enough.. eclipses tell you that the sun is behind... then just extrapolate until you find a model that fits</p><p>&nbsp;</p><p>so I would say now: about the period that we live in now, give or take 150 years &nbsp;</p> <div class="Discussion_UserSignature"> </div>

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#### bobw

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<p>I think the advent of the space age would be the clincher.&nbsp; <br /><br />If you put a satellite in orbit you would find out that the earth is spinning, especially polar orbit.&nbsp; It would put a kink in any idea about how often the sun orbits the earth.<br /><br />If you launch due north at noon on the first day of spring you will go through Earth's shadow every orbit.&nbsp; When summer comes you'll just be passing over the terminator all the time with the Sun on the right.&nbsp; Winter will have the Sun on the other side of the satellite.&nbsp; Now you know how long a year is.<br /><br />Knowing the length of the year would give you the mass of the Sun.&nbsp; When you achieve solar orbit it would be conclusive evidence for the heliocentric theory.<br /><br />I agree with l3p3r, we would know by now.</p> <div class="Discussion_UserSignature"> </div>

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#### Leovinus

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I think the advent of the space age would be the clincher.&nbsp; If you put a satellite in orbit you would find out that the earth is spinning, especially polar orbit.&nbsp; It would put a kink in any idea about how often the sun orbits the earth.If you launch due north at noon on the first day of spring you will go through Earth's shadow every orbit.&nbsp; When summer comes you'll just be passing over the terminator all the time with the Sun on the right.&nbsp; Winter will have the Sun on the other side of the satellite.&nbsp; Now you know how long a year is.Knowing the length of the year would give you the mass of the Sun.&nbsp; When you achieve solar orbit it would be conclusive evidence for the heliocentric theory.I agree with l3p3r, we would know by now. <br /> Posted by bobw</DIV></p><p>I'm thinking that without stars and planets, there would be a whole different set of religions and Gods and civilization would have evolved very differently.&nbsp; Also, I'm not sure that we'd even think to put a satellite into orbit if you didn't even know that there were such things as orbits. &nbsp; And how do we know that there are such things as orbits?&nbsp; We looked up and saw other planets going around the Sun and moons going around those other planets.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

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#### Saiph

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<p>Hmm...earth's rotation would crop up later, but it would still crop up.</p><p>At the very least engineers would note deviations in long range artillery strikes due to coriolis effects.&nbsp; No need to wait until we launch something into orbit.</p><p>We'd know the earth was round, as the greeks figured it out a long time ago (lunar eclipses).&nbsp; Even without the moon, the shadow shift vs longitude relationship would likely be noticed at some point.&nbsp;</p><p>Even without seasons, we'd know the length of the year, merely by watching the sun..wait, no stars.&nbsp; Hmmm... nevermind on that count &nbsp; Actually, it that case you may end up with a static universe, not even geocentric.&nbsp; The sun won't appear to move at all, so the immediate conclusion would be a stationary sun, and a rotating earth (also stationary). </p><p>Even if we get things into orbit, there's no real reason to say the universe isn't earth centered if we can't see anything but the sun and the moon.&nbsp; Such a simple system is easily encompassed in a geocentric system.&nbsp; Without other bodies and stars, there's no real conclusive evidence for the heliocentric model, and no real need either.</p><p>At that point, it's completely up for grabs when someone would propose a heliocentric model and if it gets adopted at all.&nbsp; Even the Copernican model, with Kepler's observations, and Newtons laws to back it up took a couple hundred years to make it to the mainstream. It was really only the stellar parralax effect that really nailed it home.</p> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"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" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

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#### bobw

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> I'm not sure that we'd even think to put a satellite into orbit if you didn't even know that there were such things as orbits. &nbsp; And how do we know that there are such things as orbits? <br /> Posted by Leovinus</DIV></p><p>Like Saiph said, some kid would plot a graph in physics class about how far a cannonball would go at 17,500 mph.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

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#### qso1

##### Guest
<p><font color="#800080">If you couldn't see planets or stars and you had only the Moon and the Sun, how much longer would it take humanity to figure out that the Earth revolved around the Sun?Same question, but now assume that the Earth has no Moon and the only thing in the sky is the Sun.&nbsp; From our point of view, it would just look like the Sun was suspended out there like a big light bulb.&nbsp; How long would it have taken for someone to figure out that the Earth revolved around the Sun?&nbsp; And I also wonder how much ridicule the first guy to suggest it would receive? Posted by Leovinus</font></p><p>It could be done. Given astronomers were able to determine the sun rotates every 25 days IIRC. One would have to closely monitor sunspots which gave the rotational data. Monitor them during the 365 day year to account for sunspot changes during that time. The suns apparent diameter (Angular resolution) at 180 or 90 day intervals would provide orbital data.&nbsp;</p> <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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#### Saiph

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<p>They could observe the sun rotating, sure...but how does that help provide orbital data?&nbsp; Ahh, you're saying they'd measure the sun's angular diamater vs time, finding the perihelion and apaheilion positions.</p><p>First, I'm trying to figure out how they'd know the length of a year (especially given the more strict stipulations of no seasons).&nbsp; If there was axial tilt, they could figure out the 365 days by plotting the solar position by shadows (that funny figure eight...name escapes me bah!)</p><p>Still, I'm not seeing any evidence that says "heliocentric" here.&nbsp; Just that bodies rotate in place, and can move about the earth (or stay stationary).&nbsp; Nothing makes more sense by saying the earth orbits the sun than vice versa. Granted, nothing rules it out, other than the fact that we're on earth, and we don't feel like we're moving.&nbsp; Can't say that for the other two objects. </p> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"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" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

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#### qso1

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<p><font color="#800080">They could observe the sun rotating, sure...but how does that help provide orbital data?&nbsp; Ahh, you're saying they'd measure the sun's angular diamater vs time,</font></p><p>Correct.&nbsp;</p><p><font color="#800080">finding the perihelion and apaheilion positions.First, I'm trying to figure out how they'd know the length of a year (especially given the more strict stipulations of no seasons).</font></p><p>The angular diameter again. Watching for it to repeat cyclically.&nbsp;</p><p><font color="#800080">If there was axial tilt, they could figure out the 365 days by plotting the solar position by shadows (that funny figure eight...name escapes me bah!)Still, I'm not seeing any evidence that says "heliocentric" here.</font></p><p>That part of it I didn't address because I was trying to figure out how to determine earth centric or heliocentric data.</p> <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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#### MeteorWayne

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>If there was axial tilt, they could figure out the 365 days by plotting the solar position by shadows (that funny figure eight...name escapes me bah!)Posted by Saiph</DIV><br /><br />Analemma <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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#### bearack

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That was what I was thinking.&nbsp; And if the Earth wasn't tilted and you had no seasons, you'd have no clue how long a year was.&nbsp; Time would just be one day after another.&nbsp; No years.&nbsp; <br />Posted by Leovinus</DIV><br /><br />Actually, years were determined well before astrology using stone rings and sun dials. <div class="Discussion_UserSignature"> <p><br /><img id="06322a8d-f18d-4ab1-8ea7-150275a4cb53" src="http://sitelife.space.com/ver1.0/Content/images/store/6/14/06322a8d-f18d-4ab1-8ea7-150275a4cb53.Large.jpg" alt="blog post photo" /></p> </div>

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#### Leovinus

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<p>Now that we have the easier question out of the way:</p><p>&nbsp;</p><p>How can you tell if the universe is spinning?&nbsp; There is nothing you can see outside of it.&nbsp; There is no reason to think that if everything inside the universe spins (galaxies, solar systems, planets, moons, stars) that the universe itself isn't spinning.&nbsp; So if it is spinning, could the expansion of the universe be attributed to not only the blast of the big bang but also the centrifugal force of the rotation of the universe?&nbsp;&nbsp; And if the universe is spinning, how can you tell how fast it is spinning if you can't see anything outside of it.&nbsp; And how could you tell if our universe is in orbit around another bigger universe?</p><p>Imagine the objects in the universe being grains of sand on a phonograph turntable.&nbsp; As the turntable spins, the grains are flung out.&nbsp; Maybe this centrifugal force is this "Dark Energy" they're looking for.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

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#### qso1

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<p>This ones actually easier to me. We do not know if the Universe spins. All data gathered to date has yet to even pinpoint an axis for the Universe to spin on. In fact, the term Universe is often debatable considering some cosmologists postulate multiple Universe. If the Universe were rotating, it would probably be doing so far too slowly for humanity to detect.&nbsp;</p> <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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#### qso1

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<p><font color="#800080">Actually, years were determined well before astrology using stone rings and sun dials. <br /> Posted by bearack</font></p><p>I may be wrong here but part of the reason this could be done was due to the earths axial tilt. Without that tilt, there would be no reference point to start from and return to.</p> <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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#### Leovinus

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Actually, years were determined well before astrology using stone rings and sun dials. Posted by bearackI may be wrong here but part of the reason this could be done was due to the earths axial tilt. Without that tilt, there would be no reference point to start from and return to. <br /> Posted by qso1</DIV></p><p>That sounds correct to me.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

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#### CalliArcale

##### Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That sounds correct to me.&nbsp; <br /> Posted by Leovinus</DIV></p><p>Yep.&nbsp; In fact, what the stone rings mark is exactly the passage of the seasons -- in particular, they usually mark things like solstices and equinoxes.&nbsp;</p> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"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."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

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#### Leovinus

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Yep.&nbsp; In fact, what the stone rings mark is exactly the passage of the seasons -- in particular, they usually mark things like solstices and equinoxes.&nbsp; <br /> Posted by CalliArcale</DIV></p><p>I should have my kids create a stonehenge in our backyard as a science project.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

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#### Saiph

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<p>hmm..realized that using sunspots and solar observations they could tell that a) the sun precesses or b) the earth is in an inclined orbit.</p><p>That could be enough to foster geocentric debate, if not conclusive proof. </p> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"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" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

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#### MeteorWayne

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Actually, years were determined well before astrology using stone rings and sun dials. Posted by bearackI may be wrong here but part of the reason this could be done was due to the earths axial tilt. Without that tilt, there would be no reference point to start from and return to. <br />Posted by qso1</DIV></p><p>With no stars, the term "Universe" would have no meaning until the CMB was discovered, if it ever was.</p> <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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#### MeteorWayne

##### Guest
<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I should have my kids create a stonehenge in our backyard as a science project.&nbsp; <br />Posted by Leovinus</DIV><br /><br />If your back yard is big enough, that sounds like a great project.</p><p>I might suggest that you use something lighter than multi ton bluestone slabs, though...</p><p><img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-smile.gif" border="0" alt="Smile" title="Smile" /></p> <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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#### Saiph

##### Guest
a bit less ambitious than a stonehenge is mapping out the analema (thanks for the word!&nbsp; I was stuck on amalgam...not the same thing ). <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"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" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

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