Is Redshift different on Hubble than on ground?

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UncertainH

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Does anyone know if the amount of measured redshift of a particular star is different when measured from hubble compared to the same star measured from earth?
 
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MeteorWayne

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Does anyone know if the amount of measured redshift of a particular star is different when measured from hubble compared to the same star measured from earth? <br />Posted by UncertainH</DIV><br /><br />Not to any significant amount. It is in orbit around the earth so that will cause a minescule difference (immeseasuarbly small), but then again observatories on earth are on a rotating surface as well. <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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derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Does anyone know if the amount of measured redshift of a particular star is different when measured from hubble compared to the same star measured from earth? <br /> Posted by UncertainH</DIV></p><p>Interesting question.&nbsp; I've read about and discussed redshift quite extensively and have never heard about it being a factor.&nbsp; Considering the <strong>Pound-Rebka Experiment</strong> can detect gravitational redshift over such small distances, I can only assume light will be slightly more blue shifted (or less redshifted depending on perspective) due to the photons falling deeper into a gravity well versus the Hubble.</p><p>Like MW mentioned, I can't see how this effect would have any statistical significance, but no doubt it does exist.&nbsp; I'm sure that when measuring recessional velocity due to the metric expansion of space, this effect can be completely ignored if it could be measured at all.&nbsp; I doubt it could be detected at all simply using observatories. </p><p>As for the doppler shift of stars in our local neighborhood, I also doubt any significant gravitational redshift could be detected between an observatory on the ground and Hubble.&nbsp; I simply doubt the Earth's graviational well is enough to make enough of a difference.&nbsp; This is likely ignored as well. </p> <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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UncertainH

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Interesting question.&nbsp; I've read about and discussed redshift quite extensively and have never heard about it being a factor.&nbsp; Considering the Pound-Rebka Experiment can detect gravitational redshift over such small distances, I can only assume light will be slightly more blue shifted (or less redshifted depending on perspective) due to the photons falling deeper into a gravity well versus the Hubble.Like MW mentioned, I can't see how this effect would have any statistical significance, but no doubt it does exist.&nbsp; I'm sure that when measuring recessional velocity due to the metric expansion of space, this effect can be completely ignored if it could be measured at all.&nbsp; I doubt it could be detected at all simply using observatories. As for the doppler shift of stars in our local neighborhood, I also doubt any significant gravitational redshift could be detected between an observatory on the ground and Hubble.&nbsp; I simply doubt the Earth's graviational well is enough to make enough of a difference.&nbsp; This is likely ignored as well. <br />Posted by derekmcd</DIV>.</p><p>So It sounds like the answer is 'maybe a little bit' but that the differnece between the earth and hubble would be negligable. However what of the difference between earth and a point outside of the gravity well of our galaxy. That may not be negligible anymore especially if dark matter theories are correct, our galaxy is far more massive than we thought it to be. If this is true and we could somehow move the hubble outside of our galaxy would we not find that the observed redshifts are even greater than what we observe on earth and that therefore the universe appears to be expanding faster than what we thought ?<br /></p>
 
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KickLaBuka

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>.So It sounds like the answer is 'maybe a little bit' but that the differnece between the earth and hubble would be negligable. However what of the difference between earth and a point outside of the gravity well of our galaxy. That may not be negligible anymore especially if dark matter theories are correct, our galaxy is far more massive than we thought it to be. If this is true and we could somehow move the hubble outside of our galaxy would we not find that the observed redshifts are even greater than what we observe on earth and that therefore the universe appears to be expanding faster than what we thought ? <br />Posted by UncertainH</DIV><br /><br /><span style="font-size:7.5pt;font-family:Verdana">Pal,</span> <p><span style="font-size:7.5pt;font-family:Verdana">They ignore a great question.&nbsp; But answering it means that they will have to agree that redshift does not ALWAYS mean recessional velocities and distance, and then they would have to tell you that something else is causing the redshifts.&nbsp; But since that would go against their only guess, "this is likely ignored as well."&nbsp; Try reading Donald E. Scott.&nbsp; </span></p>&nbsp; <div class="Discussion_UserSignature"> <p>-KickLaBuka</p> </div>
 
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derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Pal, They ignore a great question.&nbsp; But answering it means that they will have to agree that redshift does not ALWAYS mean recessional velocities and distance, and then they would have to tell you that something else is causing the redshifts.&nbsp; But since that would go against their only guess, "this is likely ignored as well."&nbsp; Try reading Donald E. Scott.&nbsp; &nbsp; <br /> Posted by KickLaBuka</DIV></p><p>The only redshift theories that are ignored are ones that have been thoroughly examined and found to be flawed when it comes to explaining what it observed.&nbsp;</p><p>Setting up strawman arguments, false dichotomies, or any other logical fallacy and telling folks to read Scott or Arp or Brynjolfsson is not enough to convince anyone. </p> <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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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>.So It sounds like the answer is 'maybe a little bit' but that the differnece between the earth and hubble would be negligable. However what of the difference between earth and a point outside of the gravity well of our galaxy. That may not be negligible anymore especially if dark matter theories are correct, our galaxy is far more massive than we thought it to be. If this is true and we could somehow move the hubble outside of our galaxy would we not find that the observed redshifts are even greater than what we observe on earth and that therefore the universe appears to be expanding faster than what we thought ? <br />Posted by UncertainH</DIV></p><p>That depends on how massive you thought the galaxy was.&nbsp; You can infer a mass from the rotational rates, and dark matter is the amount that is inferred to exist because the observed mattere is not enough to account for the rotational rates.</p><p>Your good question does raise another question, one to which I do not know the anwer.&nbsp; That question would be, "Is absolute redshift value are corrected for the gravity well in which the earth is located?".&nbsp; This should not affect the conclusions of expansion much since it would simply be a question of an additive constant being applied to the data -- red shift would still be essentially proportional to distance.&nbsp; In fact that ought to be a means of applying a correction, simply by shifting the experimental curve by an additive factor so that it&nbsp;shows zero redshift at zero distance.&nbsp; If you applied that method in preferred directions, say towards or away from the center of the galaxy and normal to the galactic plane you might even use that technique to estimate the mass and perhaps mass distribution of the galaxy.&nbsp;&nbsp; I don't know if this is actually done. <br /></p> <div class="Discussion_UserSignature"> </div>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The only redshift theories that are ignored are ones that have been thoroughly examined and found to be flawed when it comes to explaining what it observed.&nbsp;Setting up strawman arguments, false dichotomies, or any other logical fallacy and telling folks to read Scott or Arp or Brynjolfsson is not enough to convince anyone. <br />Posted by derekmcd</DIV></p><p>On the contrary, since I have&nbsp;read Scott, Arp, and Brynjolfsson,&nbsp;reference to those works&nbsp;would be quite enough to convince me.&nbsp; It would convince me that the poster has no idea what he is talking about.</p> <div class="Discussion_UserSignature"> </div>
 
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