ISF Logo   IS Forum
Forum Index Register Members List Events Mark Forums Read Help

Go Back   International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology
 


Welcome to the International Skeptics Forum, where we discuss skepticism, critical thinking, the paranormal and science in a friendly but lively way. You are currently viewing the forum as a guest, which means you are missing out on discussing matters that are of interest to you. Please consider registering so you can gain full use of the forum features and interact with other Members. Registration is simple, fast and free! Click here to register today.
Reply
Old 21st February 2016, 04:30 AM   #281
Craig B
Penultimate Amazing
 
Join Date: May 2011
Posts: 22,538
Originally Posted by macdoc View Post
I think there is a conceptal issue here....you don't "notice" curved space you notice the change in gravity that causes the change to the curve in space which a gravitational wave engenders.

Collapsing orbiting black holes managed to dispose of 3 solar masses in a very short time with an incredible amount of accompanying sturm und drang as Einsteins equation of mass and energy was demonstrated.....the result of that was a sudden change in gravity.....if you were outside the blast and radiation zone ....I doubt very much you would "notice" a gravitational wave of exceedingly short duration moving at the speed of light.
I accept your last sentence. However, I have been finding difficulty in constructing any kind of intellectual representation of this event.

Consider: the arms of LIGO were squeezed by a length equivalent to a fraction of the diameter of a proton. We didn't notice this (by normal unaided sense organs). Was that simply because the effect was so small on account of the great distance from the event? If so, what would be the case if we were so close that the LIGO arms were squeezed by a hundred metres? If a pulse of energy were to squeeze the Channel Tunnel by a similar fraction of its length, that would be very ńoticeable, even if it happened in a tiny instant of time. If we were closer, would such catastrophic disruption be caused, or would the wave pass through us leaving us unscathed?
Craig B is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 08:04 AM   #282
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,016
Originally Posted by Craig B View Post
Yes, I was wondering what would have happened if we had been much closer to the event, so that let's say the arms of the LIGO momentarily changed length by a hundred metres. Would that have caused utter disruption of all material structures, including the planet, or would it just have rippled past leaving things as unaffected as is a cork floating on a pond agitated by a breeze?
Originally Posted by Craig B View Post
Originally Posted by carlosy
So, how close would a human had to be to notice the gravitational wave itself (not the energy blast / em-waves) on his own body? Would that even be possible?
I already asked that, more or less, at #108.
I was wondering what would have happened if we had been much closer to the event, so that let's say the arms of the LIGO momentarily changed length by a hundred metres. Would that have caused utter disruption of all material structures, including the planet, or would it just have rippled past leaving things as unaffected as is a cork floating on a pond agitated by a breeze?
The responses I received haven't really enlightened me, I must admit.
I think that if you were close enough to the BBH (binary black hole) merger for the arm lengths to have changed by that much due to GW, the tidal effects of the BBH merger would have been far more severe!

The BOTE calculation I did in #262 in this thread should provide a sufficient basis for estimating how close you'd to be for a stretching and squeezing of the 4 km arms of 100m. You could also estimate the tidal force across a 4 km arm at that distance from a 60 sol mass BH (say). Of course, that close the 'linear approximations' would likely be invalid; you'd need to do a full, strong-field set of calculations, but as I think you'd be ripped to shreds by the tidal forces anyway, such a more accurate calculation seems an overkill.
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 08:14 AM   #283
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 7,883
Originally Posted by macdoc View Post
This is incorrect...

What do thing the big flash was? .....the gravitational wave was a RESULT of the ginormous conversion of mass to energy....we didn't see the flash...anything within a solar system distance was blasted to whatever raw bits apply by that 50 x output of all the stars in the universe flash.

The gravitational wave occurred because of the abrupt change in mass that occurred as a result of the conversion of mass to energy.
That change in mass generated the gravitational wave,.
Don't think so. The gravitational wave is result of the two black holes orbiting each other, not any unrelated abrupt change in mass. Orbiting bodies radiate gravitational waves which requires energy.
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 08:17 AM   #284
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,016
~

Originally Posted by smartcooky View Post
I don't think you even need the math actually, I think all you have to do is look at what the two theories propose

If gravity were a force as Newton suggested, but travelling at c then the lag of one object orbiting the other would exist.... the forces would not "point" directly at each other
Right. But I was trying to explain how an EU fan would view this. I think that they'd likely conclude that 'gravity' must have an ~infinite speed, because otherwise there'd be this lag, and because Newton's law is close enough.

Quote:
However, gravity is not a force, its a three dimensional distortion of the fabric of spacetime. That distortion "exists where it exists" regardless of the relative speeds of the two objects.

<snip>
That's where the EU acolytes, well most of them, will object. They have no time for all this math-based nonsense! It's obvious that gravity is a force, and if the math of GR produces black holes - which they see, mathematically, as pure nonsense ("can't divide by zero! weren't we taught that in school!") - that only further proves that "the mainstream" has completely lost touch with reality.

Do I think any of this makes sense? No. But I do think it's not far from what EU supporters believe.
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 08:19 AM   #285
Craig B
Penultimate Amazing
 
Join Date: May 2011
Posts: 22,538
Originally Posted by JeanTate View Post
I think that if you were close enough to the BBH (binary black hole) merger for the arm lengths to have changed by that much due to GW, the tidal effects of the BBH merger would have been far more severe!

The BOTE calculation I did in #262 in this thread should provide a sufficient basis for estimating how close you'd to be for a stretching and squeezing of the 4 km arms of 100m. You could also estimate the tidal force across a 4 km arm at that distance from a 60 sol mass BH (say). Of course, that close the 'linear approximations' would likely be invalid; you'd need to do a full, strong-field set of calculations, but as I think you'd be ripped to shreds by the tidal forces anyway, such a more accurate calculation seems an overkill.
To the lay reader, wishing to see the results of the calculations performed by more scientific minds, you are saying this: the only disruptive physical effect which might result from the merging of the black holes would result from tidal forces. If that is so, I understand it, and it aids my comprehension of the event.
Craig B is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 11:24 AM   #286
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
Ummm it's not only tidal effects...tidal affects were a constant as the black holes orbited - when they merged tho, 3 solar masses turned to energy.
Tidal effects of that collapse are the least of your worries in that cosmic neighborhood.

That event created both a huge energy release AND a sudden change in gravity which produced the wave we recorded.

Ongoing tidal effects of the single remaining larger black hole would be different than the orbiting pair was.
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 12:12 PM   #287
smartcooky
Philosopher
 
smartcooky's Avatar
 
Join Date: Oct 2012
Location: Nelson, New Zealand
Posts: 9,702
Originally Posted by Craig B View Post
Consider: the arms of LIGO were squeezed by a length equivalent to a fraction of the diameter of a proton. We didn't notice this (by normal unaided sense organs). Was that simply because the effect was so small on account of the great distance from the event? If so, what would be the case if we were so close that the LIGO arms were squeezed by a hundred metres? If a pulse of energy were to squeeze the Channel Tunnel by a similar fraction of its length, that would be very ńoticeable, even if it happened in a tiny instant of time. If we were closer, would such catastrophic disruption be caused, or would the wave pass through us leaving us unscathed?
I have NO evidence for this, its just speculation, but possibly, it could go unnoticed because the whole of local spacetime, and everything in it is distorted too.

If a passing GW makes you 10% shorter for an instant, would you notice if every molecule, every atom, every subatomic particle in you and surrounding you, was also made shorter by 10%. In other words, if your surrounding environment changes and you change with it, would you sense the change?
__________________
As democracy is perfected, the office represents, more and more closely, the inner soul of the people. We move toward a lofty ideal. On some great and glorious day the plain folks of the land will reach their heart's desire at last, and the White House will be adorned by a downright moron.
- Henry Louis Mencken - Baltimore Evening Sun, July 26, 1920
smartcooky is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 12:13 PM   #288
Mikemcc
Graduate Poster
 
Join Date: Dec 2009
Location: UK
Posts: 1,748
While the tidal effects were (almost) constant in intensity, the freqency of the tides would have changed as the two bodies approached each other. The normal tides would be pretty horrific because of the mass differences between each of the black holes. Not a pleasent environment at all, even without the collapse. The crazy thing is that, after the merger the tides should decrease!

Would have been interesting to see if hypothetical close by instrumentation could continue to detect orbital tidal effects AFTER the merger. Could the bodies still exist and orbit each other inside the event horizon? Would the event horizon then be distorted by them in that case (forming a spinning oblate). My un-informed guess is that they wouldn't, otherwise we would still see gravitational waves from them.

Sent from my GT-N5110 using Tapatalk
Mikemcc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 12:33 PM   #289
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 7,883
Originally Posted by macdoc View Post
Ummm it's not only tidal effects...tidal affects were a constant as the black holes orbited - when they merged tho, 3 solar masses turned to energy.
You mean prior to the merger, right?
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 08:58 PM   #290
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
there are always tidal affects near any large orbiting masses....we see them every day on earth.
I think the questioner means ripples as the gravity changed due to the conversion... the ripples we see in the gravitational wave record. But as those are moving at the speed of light ....kinda hard to imagine there would be any "feel".



If you were near enough to "feel" those ripples.....I think there were other things to worry about going on.
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 09:02 PM   #291
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
Quote:
To the lay reader, wishing to see the results of the calculations performed by more scientific minds, you are saying this: the only disruptive physical effect which might result from the merging of the black holes would result from tidal forces. If that is so, I understand it, and it aids my comprehension of the event.
since 3 solar masses were turned to energy in an instant....a change in tidal forces would be the least of your concerns.
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 10:53 PM   #292
rjh01
Gentleman of leisure
Tagger
 
rjh01's Avatar
 
Join Date: May 2005
Location: Flying around in the sky
Posts: 24,118
I wonder if there are any tidal effects of a planet being in orbit around two orbiting black holes? It would orbiting the common centre of gravity and it should make little difference if it was one black hole of the same mass instead.

Though when the two black holes merged and lose mass the orbit would be slightly higher.
__________________
This signature is for rent.
rjh01 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 21st February 2016, 11:07 PM   #293
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
except there would be nothing left to of the planet to orbit.
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 12:03 AM   #294
smartcooky
Philosopher
 
smartcooky's Avatar
 
Join Date: Oct 2012
Location: Nelson, New Zealand
Posts: 9,702
Originally Posted by rjh01 View Post
I wonder if there are any tidal effects of a planet being in orbit around two orbiting black holes? It would orbiting the common centre of gravity and it should make little difference if it was one black hole of the same mass instead.

Though when the two black holes merged and lose mass the orbit would be slightly higher.
A pair of BHs with a combined 65 solar masses revolving around each other are doing so in a very, very deep gravitational well, so I think a planet would have to be orbiting a BLOODY long way away from the centre of mass in order to even survive intact without being ripped apart by tidal forces.

Even if it was far enough away, it would have to be even further (in the order of many light years) to survive the sudden release of three solar masses in energy when the two merged.

Put it this way. AIUI. the merger released more energy that a typical Type II Supernova, and if one of those happens within 20 LY of us, we're toast! (don't worry, the nearest candidate star for a Supernova is α Vir a.k.a. Spica and its 260 LY away)
__________________
As democracy is perfected, the office represents, more and more closely, the inner soul of the people. We move toward a lofty ideal. On some great and glorious day the plain folks of the land will reach their heart's desire at last, and the White House will be adorned by a downright moron.
- Henry Louis Mencken - Baltimore Evening Sun, July 26, 1920
smartcooky is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 01:08 AM   #295
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
Good post.
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 01:43 AM   #296
Craig B
Penultimate Amazing
 
Join Date: May 2011
Posts: 22,538
Originally Posted by smartcooky View Post
A pair of BHs with a combined 65 solar masses revolving around each other are doing so in a very, very deep gravitational well, so I think a planet would have to be orbiting a BLOODY long way away from the centre of mass in order to even survive intact without being ripped apart by tidal forces.

Even if it was far enough away, it would have to be even further (in the order of many light years) to survive the sudden release of three solar masses in energy when the two merged.

Put it this way. AIUI. the merger released more energy that a typical Type II Supernova, and if one of those happens within 20 LY of us, we're toast! (don't worry, the nearest candidate star for a Supernova is α Vir a.k.a. Spica and its 260 LY away)
The issue is whether such an amount of energy emitted as gravitational waves would have a different effect from an equivalent amount of electromagnetic radiation. It is reasonably clear that three solar masses of gamma rays would be very destructive. But three solar masses of energy in the form of gravitational waves? What does that do to objects it encounters?
Craig B is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 04:01 AM   #297
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
What any sudden change in gravity would do to a nearby mass

Here is a good explanation exactly on your question

Quote:
Gravitational Waves: A Black Hole Is Trying to Slap You — Can You Feel It?
By Paul Sutter, Astrophysicist | February 10, 2016 06:40pm ET
- See more at: http://www.space.com/31896-gravitati....bwGPXLEC.dpuf
http://www.space.com/31896-gravitati...ter-op-ed.html
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 04:20 AM   #298
Craig B
Penultimate Amazing
 
Join Date: May 2011
Posts: 22,538
Originally Posted by macdoc View Post
What any sudden change in gravity would do to a nearby mass

Here is a good explanation exactly on your question



http://www.space.com/31896-gravitati...ter-op-ed.html
Thank you.
Craig B is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 05:40 PM   #299
Elind
Philosopher
 
Elind's Avatar
 
Join Date: Aug 2001
Location: S.E. USA. Sometimes bible country
Posts: 7,779
Originally Posted by macdoc View Post
What any sudden change in gravity would do to a nearby mass

Here is a good explanation exactly on your question



http://www.space.com/31896-gravitati...ter-op-ed.html
Yes, but I don't think it really answers the question. It implies that you could but it is so feeble that you wouldn't, which of course we know. But would you if you were closer?

I suspect you wouldn't even if you were very close (aside from EM issues). The reason is that your size and maybe even planets are very small compared to the wavelength of the gravity wave.

To use the water analogy, a wave peaking near a beach could pull your pants off depending on orientation because the wavelength is comparable to your body size and has different effects on different parts of your body in the same instant.

Now think of swimming in a tsunami in the open ocean with a wavelength that can be miles long.

How long are these gravity waves?

Last edited by Elind; 22nd February 2016 at 05:41 PM.
Elind is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 07:20 PM   #300
GodMark2
Master Poster
 
GodMark2's Avatar
 
Join Date: Oct 2005
Location: Oregon, USA
Posts: 2,055
Originally Posted by Elind View Post
How long are these gravity waves?
No less than 180km (the radius of the resultant black hold post-merger).
__________________
Knowing that we do not know, it does not necessarily follow that we can not know.
GodMark2 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 09:25 PM   #301
Elind
Philosopher
 
Elind's Avatar
 
Join Date: Aug 2001
Location: S.E. USA. Sometimes bible country
Posts: 7,779
Originally Posted by GodMark2 View Post
No less than 180km (the radius of the resultant black hold post-merger).
I finally found this that explains in more detail than most searches.

http://www.tapir.caltech.edu/~teviet..._spectrum.html

I note that LIGO has a detection range around (+ and -) 10^6 meters, although I also note that the wavelength is greater than the causing object, but 180 km is within that lower range.

However since gravity waves do not actually interact with mass or transfer energy to it, it is hard to see how it can actually cause damage to a mass. After all it simply changes, briefly, the space time nature of any mass it passes and we no doubt have those passing through even as we have this discussion.

The only way I can imagine a destructive effect is if the wavelength and amplitude were such that it pulled atoms apart so much that the nuclear forces holding them in their configurations and interactions were disrupted and they turned into some kind of plasma to recombine in unknown ways; but I have no idea if that is even theoretically possible given that the nuclear forces are many many magnitudes stronger than gravity.
Elind is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 09:47 PM   #302
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
Quote:
Yes, but I don't think it really answers the question. It implies that you could but it is so feeble that you wouldn't, which of course we know. But would you if you were closer?
You cannot be at the same time close enough to feel any tidal forces without being reduced to plasma.
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 22nd February 2016, 10:05 PM   #303
Craig B
Penultimate Amazing
 
Join Date: May 2011
Posts: 22,538
Originally Posted by macdoc View Post
You cannot be at the same time close enough to feel any tidal forces without being reduced to plasma.
Are tidal forces not capable of operating at various levels of intensity, such that one might feel a slight effect, without being thereby reduced to plasma? Or an event that would reduce a nearby mass to plasma, might have a smaller, but still detectable, effect on a somewhat more distant object?

Last edited by Craig B; 22nd February 2016 at 10:07 PM.
Craig B is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 23rd February 2016, 03:24 AM   #304
asydhouse
Master Poster
 
asydhouse's Avatar
 
Join Date: Feb 2012
Location: Swansea in the UK
Posts: 2,368
Originally Posted by Maartenn100 View Post
"ripples in the fabric of space and time." Nice words, but no human being can really grasp what it means. No scientist can grasp: a big bang, spacetime, quantumphysics, singularities etc. You think you understand these things because you gave it a fancy name. It is beyond our human capacity to actually understand what's going on in this world on these levels.


It's spacetime, not two separate things added. The fact that you have made this ugly false picture of what General Relativity is about is evidence that you really are ignorant.

Your assertion that all GR does is name things is another indicator that you are blowing raspberries out your arse.

If you had ever bothered to actually take a science course, you would have more respect for the maths. And our limited human conceptual tools are not sufficient to "understand" with a simple image or analogy to things we do understand, that much is true. But the maths is a different story, which can indeed be fully understood.

Edited by Agatha:  Edited to remove breach of rule 0 and rule 12
__________________
asydhouse art website http://www.asydhouse.co.uk/asydhouse...Syd_house.html

Last edited by Agatha; 23rd February 2016 at 07:12 AM.
asydhouse is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 23rd February 2016, 04:12 AM   #305
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
Quote:
might have a smaller, but still detectable, effect on a somewhat more distant object?
This is what we do withi LIGO.. can we "feel it"...under any circumstance where we are not in the volume of space blasted by the energy release - very very unlikely in my view.
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 23rd February 2016, 04:00 PM   #306
Elind
Philosopher
 
Elind's Avatar
 
Join Date: Aug 2001
Location: S.E. USA. Sometimes bible country
Posts: 7,779
Originally Posted by macdoc View Post
You cannot be at the same time close enough to feel any tidal forces without being reduced to plasma.
I guess we agree.
Elind is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 23rd February 2016, 05:49 PM   #307
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
yup
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 23rd February 2016, 07:08 PM   #308
joelr315
New Blood
 
Join Date: Feb 2016
Posts: 3
Originally Posted by Craig B View Post
Are tidal forces not capable of operating at various levels of intensity, such that one might feel a slight effect, without being thereby reduced to plasma? Or an event that would reduce a nearby mass to plasma, might have a smaller, but still detectable, effect on a somewhat more distant object?
In a link on this page it noted that being near 2 colliding, 10 solar mass black holes moving at light speed would produce a gravity wave around 1% the size of an atom. Which would obviously be impossible to feel but the tidal forces would be huge.

So to produce a macroscopic gravity wave there would need to be around 10^15 more colliding black holes. So I guess tidal forces and other problems always get in the way.
joelr315 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 29th February 2016, 04:12 PM   #309
Mikemcc
Graduate Poster
 
Join Date: Dec 2009
Location: UK
Posts: 1,748
Tests beginning soon on The LISA Pathfinder mission. It's a technology demonstrator for a proposed (but as yet unfunded...) mission to scale up the LIGO measurements. So it's measuring the distance between two free-floating blocks only 38cm apart, but with incredible levels of accuracy.

http://www.bbc.com/news/science-environment-35689814
Mikemcc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 29th February 2016, 05:20 PM   #310
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
Quote:
Originally Posted by Craig B View Post
Are tidal forces not capable of operating at various levels of intensity, such that one might feel a slight effect, without being thereby reduced to plasma?
careful...it's not the gravity wave reducing you to plasma if nearby...it's what caused the gravity wave.....the gravity wave is a consequence of the event.....as is your plasma make over.
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 29th February 2016, 07:13 PM   #311
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 7,883
Originally Posted by macdoc View Post
careful...it's not the gravity wave reducing you to plasma if nearby...it's what caused the gravity wave.....the gravity wave is a consequence of the event.....as is your plasma make over.
Why would two orbiting black holes reduce you to plasma?
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 29th February 2016, 11:31 PM   #312
GodMark2
Master Poster
 
GodMark2's Avatar
 
Join Date: Oct 2005
Location: Oregon, USA
Posts: 2,055
Originally Posted by RecoveringYuppy View Post
Why would two orbiting black holes reduce you to plasma?
Two Words:

Accretion diskWP
__________________
Knowing that we do not know, it does not necessarily follow that we can not know.
GodMark2 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st March 2016, 12:02 AM   #313
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 7,883
Originally Posted by GodMark2 View Post
Two Words:

Accretion diskWP
Do we have reason to think there was an accretion disk?

ETA: And why would the accretion disk cause gravitational waves? (see the post I was replying to if that question doesn't make sense to you).
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.

Last edited by RecoveringYuppy; 1st March 2016 at 12:05 AM.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st March 2016, 02:49 AM   #314
rjh01
Gentleman of leisure
Tagger
 
rjh01's Avatar
 
Join Date: May 2005
Location: Flying around in the sky
Posts: 24,118
Originally Posted by RecoveringYuppy View Post
Do we have reason to think there was an accretion disk?

ETA: And why would the accretion disk cause gravitational waves? (see the post I was replying to if that question doesn't make sense to you).
There is no evidence one way or other on the accretion disk. And accretion disk would not have any influence on the gravitational waves. The later was caused by the two black holes orbiting very close to each other.
__________________
This signature is for rent.
rjh01 is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st March 2016, 04:55 AM   #315
smartcooky
Philosopher
 
smartcooky's Avatar
 
Join Date: Oct 2012
Location: Nelson, New Zealand
Posts: 9,702
Originally Posted by macdoc View Post
careful...it's not the gravity wave reducing you to plasma if nearby...it's what caused the gravity wave.....the gravity wave is a consequence of the event.....as is your plasma make over.
Nitpicking technicality

gravity waves and gravitational waves are not the same thing, and for the avoidance of doubt, you should try not to get those terms mixed up...

http://www.livescience.com/53683-gra...ifference.html

just sayin'
__________________
As democracy is perfected, the office represents, more and more closely, the inner soul of the people. We move toward a lofty ideal. On some great and glorious day the plain folks of the land will reach their heart's desire at last, and the White House will be adorned by a downright moron.
- Henry Louis Mencken - Baltimore Evening Sun, July 26, 1920
smartcooky is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st March 2016, 06:08 AM   #316
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 7,883
Originally Posted by rjh01 View Post
There is no evidence one way or other on the accretion disk. And accretion disk would not have any influence on the gravitational waves. The later was caused by the two black holes orbiting very close to each other.
Yes, I agree.
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st March 2016, 08:49 AM   #317
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,016
Originally Posted by RecoveringYuppy View Post
Do we have reason to think there was an accretion disk?

<snip>
We don't.

However, if you were close to the two black holes, you'd be converted to a plasma very quickly indeed, and that plasma would form into a (very thin!) accretion disk (albeit not so quickly).

There may not have been much plasma near the two black holes, in the days leading up to the merger, but what little there was (and there certainly was at least some) would have made your life close to the BHs very uncomfortable indeed. Not to mention getting spaghettified ...
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st March 2016, 09:56 AM   #318
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 7,883
Originally Posted by JeanTate View Post
We don't.

However, if you were close to the two black holes, you'd be converted to a plasma very quickly indeed, and that plasma would form into a (very thin!) accretion disk (albeit not so quickly).

There may not have been much plasma near the two black holes, in the days leading up to the merger, but what little there was (and there certainly was at least some) would have made your life close to the BHs very uncomfortable indeed. Not to mention getting spaghettified ...
Yeah, I get that. My post was questioning macdocs scenario. He said the even that causes the gravity (think he meant gravitational) waves would also turn you to plasma. I don't know why that would be.

The phenomena you're talking about doesn't require orbiting black holes and happens even in the absence of gravitational waves.

So I'm not sure what connection macdoc is referring to.
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st March 2016, 05:59 PM   #319
macdoc
Philosopher
 
macdoc's Avatar
 
Join Date: Dec 2008
Location: Planet earth on slow boil
Posts: 7,927
Quote:
He said the even that causes the gravity (think he meant gravitational) waves would also turn you to plasma
RY...I don't think you understand what the process is.

Very close to two back holes you are going to be plasma but for a different reason....near vicinity is very violent space.

Further out you could in theory orbit the two but a long ways out

In neither case are there gravitational waves produced that we could detect.

When the two black holes merged however...3 solar masses were turned from mass to energy in an instant.

That event produced the gravitational wave we detected .....

That event would ALSO turn your distant orbiting space ship to plasma

.....but it's not the GW turning you stardust ....it's the energy release....equivalent to 50 x the output of all the stars in the universe for a very brief moment. That's the point at which you join the stardust contingent ......but it's not the gravity wave dismembering you .....it's the energy release.

The GW is a result of the change in gravity caused by converting mass to energy on an enormous scale.....3 solar masses worth..
Your dismemberment is a result of the energy release not of effects of the gravity wave on you.

Last edited by macdoc; 1st March 2016 at 06:03 PM.
macdoc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st March 2016, 07:25 PM   #320
Dribble Error
New Blood
 
Join Date: Oct 2011
Posts: 12
According to these guys at 1AU it would feel more like standing next to a loudspeaker, which if true is pretty awesome (if you're at a concert that is, pretty underwhelming if you're 1AU from a collapsing black hole)
https ://www .reddit.com/r/askscience/comments/45n0sz/how_close_to_gw150914_the_black_hole_merger_would/

(I've broken the link as I'm not allowed to post them yet)
Dribble Error is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Reply

International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -7. The time now is 05:43 AM.
Powered by vBulletin. Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.

This forum began as part of the James Randi Education Foundation (JREF). However, the forum now exists as
an independent entity with no affiliation with or endorsement by the JREF, including the section in reference to "JREF" topics.

Disclaimer: Messages posted in the Forum are solely the opinion of their authors.