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Black Holes: Incredibly Loud and Extremely Distant

The views expressed are those of the author and are not necessarily those of Scientific American.

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This post is the third in a series that accompanies the upcoming publication of my book ‘Gravity’s Engines: How Bubble-Blowing Black Holes Rule Galaxies, Stars, and Life in the Cosmos’ (Scientific American/FSG).

In space it’s a good thing that you can’t hear black holes scream.

Although some of the most incontrovertible evidence for the existence of supermassive black holes comes from observing their gravitational effect on neighboring stars, there are other even more spectacular clues. The clearest of these were unwittingly seen in extraterrestrial radio signals as far back as the late 1930′s, and then observed with increasing fidelity as better and better technology allowed astronomers to map out the cosmos.

Among the brightest of these astronomical radio wave sources are some extraordinary and very distant structures. Many of these puzzling forms not only span hundreds of thousands of light years but are strikingly asymmetrical, while others are ‘doubled’, like the two ends of a vast dumbbell. The image here is a modern radio map of one of the most famous such objects, known as Cygnus A.

Cygnus A mapped in microwaves (NRAO/VLA)








This beast is some 600 million light years from the Milky Way, and end-to-end it spans about 500,000 light years. The radiation we’re seeing comes from electrons that are moving at close to the speed of light and cooling themselves down by shedding microwave photons (among other frequencies) as they spiral around intergalactic magnetic fields. These fast-moving particles are transported in the thin beams, or ‘jets’, that appear to emerge from a point of brightness at the very center, before they splash into the great lobes of light to either side. But what powers such an enormous system of subatomic acceleration?

First let’s put it in perspective. Here is the galaxy at the very center of Cygnus A as seen by the Hubble Space Telescope.

The galaxy of Cygnus A in visible light (Hubble Space Telescope/NASA/ESA)

It’s a bit of a messy object. Lots of stars, lots of dust and gas. It carries the markings of interstellar turmoil, and hints at the presence of other intense sources of radiation.


But things get really interesting when we place this image to approximate scale on top of the radio map of Cygnus A.

The galaxy of Cygnus A to approximate scale superimposed on the radio map









See that? The visible galaxy is tiny compared to the rest of Cygnus A.

This is a terrific clue to the incredible amount of energy being pumped out to intergalactic space – from a very small point of origin. Back in the 1960′s and 70′s it was the sheer scale of the energy budget of objects like Cygnus A that challenged astronomers and physicists to come up with a sufficiently efficient power source. Nothing chemical or nuclear seemed to come close to meeting the requirements, and there was the striking morphology to explain as well – all that energy seemingly channeled into narrow beams of highly relativistic (near light speed) particles.

Representation of a gravity well, 3 dimensions collapsed to 2 (Credit: AllenMcC)

Although it was a contentious issue, it eventually became clear that there was in fact a natural power source of the required efficiency; gravity. As matter falls into a gravity well it is accelerated, and the further down the gravity well that matter can fall, the greater the velocity it can reach. The ultimate in gravity wells are those produced by black holes, which by definition are so compact and so ‘steep’ that light itself is unable to climb away again (at least not without giving up all its energy). Matter that becomes ensnared by a hole can accelerate to close to the speed of light, but before it disappears across the event horizon the friction and turbulence of its spiraling path can generate a phenomenal amount of energy that escapes and floods out. Add some other factors, like black hole spin and black hole electrical charge, and a supermassive hole can build you a machine that’s as much as fifty times more efficient than nuclear fusion at converting matter into energy – and it can also squirt that energy out in narrow particle beams.

So just how loud can an energy spewing supermassive black hole be? It depends a lot on the circumstances; the size of the hole, its rate of spin, and how much matter is feeding into it, but there are some examples that help give us an idea of what to expect.

An image in X-ray light of the Perseus galaxy cluster (NASA/CXC/IoA/A. Fabian et al.)

This is an image of X-ray light being emitted by million degree gas that sits inside a galaxy cluster called Perseus. Within the gas, at the center, is a galaxy called Perseus A that contains a supermassive black hole. Every few hundred thousand years that black holes goes on a feeding frenzy and ejects particles outwards. Except that deep inside the galaxy cluster those particles bump right into the material around them, and like a giant blowing air through a straw, the black hole inflates enormous bubbles inside the hot gas. These are the darker looking patches in the image.

Incredibly, the inflation of these bubbles is akin to firing up a colossal sub-woofer, setting sound waves in motion that flood outwards as ripples that are over a hundred thousand light years in width (you can see them in this picture). That’s a note played at a frequency a million, billion times lower than anything the human ear can detect. And the output is a whopping ten-to-the-power-of-thirty-seven watts, or about ten billion times the energy of our Sun. It is indeed fortunate that this primal scream is eventually lost to the vacuum of space.

Just as your annoying neighbor may keep you awake at night, what can a bellowing black hole like this do to the universe around it? It turns out that it may play an unexpectedly important role in creating the appearance of our cosmic surroundings.

…to be continued.

Caleb A. Scharf About the Author: Caleb Scharf is the director of Columbia University's multidisciplinary Astrobiology Center. He has worked in the fields of observational cosmology, X-ray astronomy, and more recently exoplanetary science. His books include Gravity's Engines (2012) and The Copernicus Complex (2014) (both from Scientific American / Farrar, Straus and Giroux.) Follow on Twitter @caleb_scharf.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. promytius 12:00 pm 07/16/2012

    I found the article very interesting and the title very confusing – black holes are everywhere, yes? We’ve got one in our own neighborhood, so I’m confused by the title.

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  2. 2. Caleb A. Scharf in reply to Caleb A. Scharf 12:22 pm 07/16/2012

    Mea culpa, I was trying to be clever by making reference to a certain book/film with the title. In my defense, the black holes that are producing the most energy and the kinds of phenomena we see around Cygnus A or in Perseus are relatively rare and therefore typically a long, long way from us. But you are correct that black holes are everywhere, it’s just that they’re mostly ‘hibernating’ for lack of food.

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  3. 3. juandegringo 2:46 pm 07/16/2012

    A big bang, eh?

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  4. 4. jack.123 6:43 pm 07/16/2012

    Are there not bubbles at our own galaxy’s center?

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  5. 5. Cramer 1:49 am 07/17/2012

    When a black hole is feeding, how much matter and energy is ejected versus the amount of matter and energy that is absorbed (i.e. crosses the event horizon)?

    Due to gravitational time dilation, matter will take an infinite amount of time to reach the event horizon as observed by a distant observer. How then can we ever witness a black hole feeding in such a way that matter is not ejected?

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  6. 6. vinodkumarsehgal 1:52 am 07/17/2012

    To Celeb A Scharf

    “This beast is some 600 million light years from the Milky Way, and end-to-end it spans about 500,000 light years.” Cygnus A

    What could be Cygnus A with such an enormous size of 500,000 light years? Have radio signals been detected from some few places of Cygnus A Or entire Cygnus A is the radio source?

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  7. 7. vinodkumarsehgal 2:04 am 07/17/2012

    To Cramer

    When matter will approach event horizon, due to very high gravitation, its speed shall also be high and may approximate speed of light. Due to time dilation, distant observer may not observe in-falling of matter within a BH but enormous speed due to gravitation shall push the matter in BH. Non-observance by any distant observer is not a priori for pushing of matter in a BH

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  8. 8. Knyaz 2:16 am 07/17/2012

    Возможно все миры других измерений мы видим как тёмную материю а чёрная дыра это способ перехода одного измерения в другое.Может материя при переходе из одного измерения в другое преобразуется в информационный поток состоящий из частиц Бозона -Хигса а выходит из чёрной дыры в виде света,но свет не такой который можно разложить как радугу.Возможно свет выходящий из чёрной дыры это информационная конструкция материи.Я правильно думаю или нет?

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  9. 9. Cramer 1:43 pm 07/18/2012


    Time dilation requires two inertial frames of reference (i.e. TD and relativity becomes meaningless if only one inertial frame is referenced — that’s why it’s called relativity). Not to mention that it would be impossible for us to be anything but a distant observer with respect to a black hole (all BH’s are too far away and any instrument we could send there would be ripped apart approaching the event horizon).

    Also, both a high gravitational field and high velocity slow clocks.

    Sorry that I really do not understand the relevance of your reply, but I am very open to modifying my thinking. Something seems wrong about my interpretation of time dilation, but I have not yet straightened it out in my mind. It also seems like I’ve been here before in the thirty years since I first learned about relativity and time dilation. I thought I was able to straighten it out before — so I am confident I will straighten it out again; and any help would be greatly appreciated.

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  10. 10. vinodkumarsehgal 2:33 am 07/19/2012

    To Cramer (5 and 9)

    “Due to gravitational time dilation, matter will take an infinite amount of time to reach the event horizon as observed by a distant observer” (5)

    In your above quote (5), you mentioned that with respect to a distant observer, matter shall take infinite time to reach the event horizon due to time dilation. So in a way you amounted to state that matter shall never reach event horizon.

    I was referring that due to high gravitational pull, matter shall also pick up speed and may approach speed of light. Additionally, mass of approaching matter shall also increase. So in away, following 3 changes shall take place in matter approaching event horizon of a BH :

    i) Time dilation approaching zero
    ii) Increase in mass approaching infinity
    iii) Increase in speed approaching speed of light

    You stated that TD and other changes shall take place w.r.t distant frame of reference from which distant observer is observing. If we take this interpretation than relativity is an illusion since no actual change will take place in frame of reference of BH and EH and distant observer will only observe above changes, which will be an illusion.
    My understanding states me that if relativity has to be a realistic phenomenon, all the above three changes should actually take place w.r.t frame of reference of BH and EH. Any how, I am not staking any claim for this interpretation. You may correct me if I am wrong, but then relativity will be an illusionory phenomenon.

    Nevertheless, I do not understand how to reconcile between high speed approaching speed of light and time dilation approaching zero. What will happen to matter sandwitched between these two contradictions?

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  11. 11. Cramer 1:11 pm 07/19/2012


    I did not suggest there was an illusion. If it was an illusion, General Relativity would not hold. “Magic tricks” can not be used to prove scientific theories.

    I also never said that matter does not reach or cross the event horizon. Let me explain the paradox from the BH reference frame (remember GR and SR takes two inertial frames of reference).

    From the reference frame of matter falling into a black hole, the distant world is speeding up in time. Before the matter reaches the event horizon it would observe the entire evolution of the universe (e.g. it would observe the Milky Way and Andromeda merging in 4 billion years). Yes, that matter still crosses the event horizon, but only in its own reference frame, BUT not in the reference frame of an outside observer. [Let's not get into survivability of the object/matter that would be observing the universe from the BH -- that's not relevant to the theory, but only to experiments that would send an object into a black hole -- which we can not do.]

    I have seen explanations of this paradox that the outside observer can only observe the photons given off by matter approaching the event horizon. In that case photons are will require an amount of time approaching infinity to reach the distant observer; therefore, the photon particles must be residing near the event horizon for an infinite amount of time. In either case, whether it’s matter or photons, something is remaining near the event horizon for a long, long time (possibly until well after the Milky Way and Andromeda merge — depending on how close to the event horizon that photon was emitted).

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  12. 12. Cramer 1:24 pm 07/19/2012


    I did not mean to imply that a matter is not ejected from a black hole (as in a relativistic jet or another process) when I said that matter or photons would remain near the event horizon (as observed by a distant observer).

    That’s why it’s a paradox. If any explanation of a paradox is completely acceptable, would it be a paradox?

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  13. 13. Cramer 1:45 pm 07/19/2012

    Have you spent much time thinking about the paradoxes that exist in relativity? Have you thought much about the Twin Paradox in Special Relativity?
    Asymmetrical acceleration does not seem to be a good explaination to me because SR applies to inertial frames which by definition are not accelerating. So we could just adapt the experiment to only consider the constant velocity portion of the traveling twin’s trip. I.e. we could have one twin travel at high speed past Earth at a constant velocity and send the EMR signal at two points in time (also far from Earth to negate gravitational TD). You could also make it that the twin in space is traveling counter to the rotation of the Milky Way (Our solar system is moving at 250 km/sec in orbit around the Milky Way). Then one could ask which twin is really moving? Remember, in the principle of relativity, a preferred or absolute inertial reference frame does not exist.
    Which twin’s clock would slow?

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  14. 14. vinodkumarsehgal 2:49 am 07/20/2012

    To Cramer
    Let me approach the issue afresh from a new angle in order to resolve one important aspect of relativity. Suppose X is the Frame of Reference (FR) of an observer at earth who is observing falling matter in a remote BH. Let Y be the FR of an observer who is residing near BH and observing the in-falling matter in BH. Obviously near the BH, in-falling matter shall experience high gravitation and consequently undergo TD, Length Contraction, Increase of Mass and increase in speed. If we say that SR is not applicable upon accelerating FRs, let us assume for the time being that Y is at a constant very speed w.r.t X.

    Matter in Y will experience all the relativistic changes viz increase of mass, TD, Length contraction and increase of speed. But these changes shall be w.r.t which observer. If we interpret that changes shall happen to matter in Y w.r.t an observer in X, this will imply to say that nothing has happened actually to matter in frame Y W.R.T AN OBSERVER IN Y. THIS WILL AMOUNT TO SAY THAT NO REALISTIC INTRINSIC CHANGE HAS HAPPENED TO MATTER IN FRAME Y AND ALL CHANGES ARE MERELY DUE TO FACT THAT SAME WERE BEING OBSERVED FROM X. This will lead to relativity being an observer centric phenomenon with no substance in the intrinsic mechanics of matter. This is what I term as illusion. what is an illusion? When in actuality, there is no intrinsic change but change arises due to mere fact THAT OBSERVATIONS ARE BEING MADE FROM A SPECIFIC FR.

    When matter shall return to X from Y, changes brought about due to increase of speed in Y should also vanish when observed from X since there was no intrinsic permanent changes in matter and changes APPEARED TO HAPPEN ( AN ILLUSION) SINCE OBSERVATIONS OF MATTER IN Y WERE BEING MADE FROM X. Now since that differences in frames (X and Y) is over, changes should also vanish. In my view, if relativity is a realistic phenomenon, a changes once brought out due to increase of speed should persist permanently even if FR of the observed object changes. Otherwise it will be an illusion due to fact that there were no actual changes but changes HAPPENED TO APPEAR TO MATTER IN Y DUE TO IT BEING OBSERVED IN X

    I Do not have any problem in accepting the interpretation that changes to matter in Y shall be w.r.t an observer in X and NO CHANGE SHALL TAKE PLACE W.R.T AN OBSERVER IN Y. BUT THEN LET US BE READY TO ACCEPT THE FACT THAT CHANGES WERE ILLUSION DUE TO OBSERVATION BEING MADE FROM X.

    Now let me speak of a conundrum which somehow I can not resolve my self. Matter shall experience high speed which will bring TD whether w.r.t an observer in X or Y. High speed will tend to take matter to within BH while TD will tend to oppose this. What will happen to matter within these two contradicting process of high speed and TD.

    Mr Cramer: I request you to please ponder over two issues

    I) Changes to matter in Y shall be w.r.t which observer — an observer in X or Y
    ii) what is the trade off between increasing speed and decreasing time (TD)

    My be your understanding or some insight may straighten my understanding

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  15. 15. Cramer 7:50 pm 07/20/2012


    Sorry, I can not call relativity an illusion. I do not want to get into another semantics debate.

    We do have the ability to interact with objects that are in another inertial frame of reference. This is why particle accelerators take so much energy. In our reference frame the particle actually does have very high momentum (resulting from relativistic mass) — it’s not an illusion.

    In time dilation a permanent change does occur. When the twin returns from his high-speed trip, he will find his brother dead of old age. Radioactive decay of muons have proven this.

    Thanks you for taking the time for your explanations.

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  16. 16. vinodkumarsehgal 12:52 am 07/21/2012


    I am not speaking of semantics. I made two very specific queries i) and ii) at my post 14. You did not respond against those queries. I also did raise the issue of relativistic changes from observational perspective or from intrinsic permanent perspective. A permanent change should persist in all frames and it should be independent of observational perspective.

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  17. 17. Cramer 1:03 pm 07/21/2012

    First, you asked me to “ponder over two issues.” I did not interpret your request as queries/questions that required an explicit reply since you presented them as if you already knew the answer — i.e. rhetorical questions. You did not even end your “issues” with question marks. Those “queries” also suggest that you did not read my comments too well.

    Second, I believe I did answer your questions. I said that “changes in matter” are not illusions. Both observers will notice changes, but the changes are relative, such as a twin returning to Earth to find his brother dead. [Was his clock slower or his brother's clock faster? To him, his brothers clock was faster. It does NOT work like Star Trek when they flew around the Sun and everyone on the space ship was distorted and floating around in slow motion.] I already answered your question about the “trade-off between increasing speed and decreasing time (TD).” I said “both a high gravitational field and high velocity slow clocks.” There is no trade-off. I said that “matter still crosses the event horizon, but only in its own reference frame.” An observer crossing the event horizon does not even notice the event horizon — everything is normal and it happens fast because he is traveling fast (not like Star Trek where he would be floating around distorted and in slow motion).

    Third, I explicitily asked you questions that you did not answer: “Have you spent much time thinking about the paradoxes that exist in relativity? Have you thought much about the Twin Paradox in Special Relativity?” From your replies, my guess would be no. You seem to lack a basic understanding of relativity. Young and Freedman’s University Physics gives an excellent introduction to SR.

    These paradoxes even bothered Einstein (and other physicists) well after he published his papers.

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  18. 18. vinodkumarsehgal 2:33 am 07/22/2012

    To cramer

    Kindly do not go into semantics whether I have put up question marks after my queries or not. Please see the intention due to which I raised the queries.

    Candidly speaking, I am not conceptually fully clear about some aspects of Relativity especially TD and length contraction. Reason? There is yet no consensual and clear understanding on the nature of composition of Time and Space — two major elements of universe with which relativity primarily deals with. if I may start discussing about various concepts of space and time, it may be too long and same is not possible under these columns.

    Cramer, see, there is no significance in indicating my agreement to any of your or for that sake any person’s idea or concept unless and until my inner self becomes a witness to same. After all, we are not in a primary school where teacher teaches A for apple and all pupils repeats A for apple.

    I have thought over twin paradox over some period. whether deeply or not. I do not know. My current understanding dictates me that speeding twin (away from earth) shall undergo all relativistic changes — TD, increase of mass and length reduction which shall result from high speed or gravitational effects BUT these changes shall persist as long as twin shall remain in the speeding frame ( away from the earth) and observer also remains in the speeding frame. Why this interpretation? I shall explain. These relativistic changes arise due to mainly two reasons : i) High speed w.r.t twin at earth ii) observer is also in the speeding frame

    Now when speeding twin has returned to earth in the normal original frame ( from which he had left), primary causes which brought out changes i.e. high speed/high gravitational effect and observational frame ( from which changes were being perceived) NO LONGER EXIST, THEREFORE, WHY SHOULD CHANGES PERSIST? I am not staking any claim for the correctness for this interpretation, however, if you state that I am wring in my interpretation, please provide appropriate argument.
    Scientific and rational approach demands that whenever we put up any interpretation, we may support the same with rational logic, understanding. If there is some observational evidence, it is necessary to understand inner mechanism behind that observation also

    A thing which I would like to repeat, since you have not given explicit and direct answer, is ( my post 14): Changes in mass, TD, length contraction to matter as speeding up in frame Y shall be w.r.t to which observer — an observer in frame X or frame Y.

    Regarding trade off query either I have not been able to put up my point of view properly or you have not understood in the spirit in which I raised the query. Against this query, you have responded that gravitation and velocity shall slow the clocks. This much, I understood before also. In the first place, this was not my queries. Secondly. Why it is not possible that slowing down of clocks may be due increase of mass of clocks?

    Now let me rephrase my query. High speed near BH shall tend to take matter to the center of BH while TD shall tend to oppose it ( since time is either flowing very slowly or not flowing). An analogy of tug of war in case of rope game. So what will happen to matter?

    Do you think still my queries do not make any sense to you? Or you do not want to face these issues?

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  19. 19. vinodkumarsehgal 3:28 am 07/22/2012

    To Cramer Further to 18

    Let me rephrase my interpretation of twin paradox from a new angle.

    Suppose a single person leaves earth on an outward journey in a high speed spaceship, stays around a BH or some high gravitational object for some period. I am not speaking of any left out twin at earth but discussing the case of only one single person on a spaceship. Before commencement of journey, he was having some mass, time, length in his normal frame X at earth. Now since he is is residing a new frame Y in speeding spaceship near a BH having high gravitation, he will feel all the relativistic changes in mass, time and length w.r.t values which he was having at earth in frame before commencement of outward journey. Up to point, I have no problem and my conceptual understanding supports me.

    Now let us move a bit ahead. After staying near BH, suppose person starts his inward journey to earth and suppose space ship assumes the same trajectory and speed as was in the inward journey. Now the person is also passing thro equivalent speed changes and gravitational changes W.R.T FRAME Y OF BH WHERE HE WAS STAYING BEFORE COMMENCEMENT OF INWARD JOURNEY. When the person will stay at earth for some time, he will experience all the relativistic changes viz TD, mass changes, length changes w.r.t the values of these elements in frame Y. These changes in inward journey should be opposite in sign to changes as brought out in outward journey since speed effect and gravitational effects are also opposite. Consequently, all the relativistic changes brought about in outward journey shall be cancelled by relativistic changes brought about in inward journey. So where will be NO permanent change on arrival back at earth. I am not touching the issue of symmetry of frame X or Y. I am simply saying that person starts a fresh journey from BH (frame Y ) to earth (frame X). Even if one may say that velocity in inward journey shall not be opposite to velocity in inward journey, ( though I say it will be opposite) BUT gravitation at earth shall definitely be opposite to that at earth.

    in view of above, my understanding does not support any permanent change in mass, time and length. You please ponder and explain, supported by reasoning why it should
    be a permanent changes.

    Mr Cramer, I am not adamant or fixed with any conception. I am ready to change my views instantly provided it is supported by some rational reasoning which goes down my mind and heart.

    Let us deal the issues from the front with an open mind

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  20. 20. Cramer 1:33 pm 07/22/2012

    Vinod (comment #18):


    Yes, time dilation, Lorentz contractions, etc no longer persist when two observers are in the same inertial frame of reference — clocks once again run at the same speed. I believe I made that clear — that’s RELATIVE-ity — it’s the basic core concept. However, the changes that did occur when the observers were in different reference frames were NOT an ILLUSION. For example, when a twin returns he may find himself (depending on velocity, etc) 1000s of years in the future — his twin brother is dead. It does NOT work like the Planet of the Apes films. They were able to return to the future Earth inhabited by apes (correct) as in the original 1968 film, but they could not return to the present day Earth as they did in the 1971 Escape from the Planet of the Apes (incorrect). Time dilation does not reverse itself. That’s all I was saying.

    You asked, “…frame Y shall be w.r.t to which observer — an observer in frame X or frame Y[?].”

    I have answer this question several times. It’s RELATIVE-ity. Changes in one frame are being observed in the other frame. I even gave you are Star Trek example about flying around the sun. Captain Kurt would NOT observe his fellow ship mates as moving in slow motion or contracting as was shown in the movie. Locally NO changes are observed, everything is normal (I said this about crossing the event horizon).

    You asked, “High speed near BH shall tend to take matter to the center of BH while TD shall tend to oppose it… So what will happen to matter?”

    Nothing can travel faster than the speed of light, but time dilation can go to infinity. TD wins. TD requires two reference frames. LOCALLY at the black hole, matter does cross the event horizon and collides with the “singularity.”

    You asked, “Why it is not possible that slowing down of clocks may be due increase of mass of clocks?”

    Gravitational time dilation requires a gravitational field. Locally, the mass of the clock traveling at high velocity (no BH) is not increased — there is no gravitational field. This should also NOT be confused with the Equivalence Principle between a gravitational force and the force from a non-inertial reference frame (i.e. an accelerating reference frame). SR applies to INERTIAL reference frames.

    You asked, “Do you think still my queries do not make any sense to you? Or you do not want to face these issues?”

    I have answered your questions several times. You seem not to be reading what I write. I would suggest you read a physics textbook that goes over all these examples. I continue to spend my time repeating myself, so suggesting that I might “not wanting to face these issues” is insulting to me. I could be doing other things with my time.

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  21. 21. Cramer 1:43 pm 07/22/2012

    Twin Paradox (comment 19):

    You said, “Now since he is is residing a new frame Y in speeding spaceship near a BH having high gravitation, he will feel all the relativistic changes…”

    No. He will not experience any relativistic changes locally. RELATIVE-ity requires two frames of reference. He will feel normal — no time dilation, no increase in mass. However, he will feel local forces such as the gravity of the BH just like we are now feeling the gravity of the Earth. And if he looks back at Earth (which is in another reference frame), he will see its clocks speeding up.

    You said, “Consequently, all the relativistic changes brought about in outward journey shall be cancelled by relativistic changes brought about in inward journey.”

    No. It does not work in reverse. Please see my previous comments. When the twin returns to Earth it will be 1000s of year into the future even though the twin only experience being away five years. It’s the 1968 Planet of the Apes film. They travel out and back to Earth at high velocities. They originally think they are on another planet, but they do know they are in the future because they talk about their family and friends on Earth being dead for thousands of years. The year is AD 3978. Charleton Heston later finds the Statue of Liberty. They can NEVER go back to 1960s Earth. The process is irreversible (therefore the 1971 sequel is impossible).

    The more I write, the more I repeat myself.

    You need to read a textbook to explain why. For me to explain why it would take too much writing and requires diagrams, math, etc. You must do the work.

    You should also start with Special Relativity, not General Relativity. Do not think about black holes and gravity until you have SR down. It only complicates things and makes it more difficult to understand.

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  22. 22. vinodkumarsehgal 1:54 am 07/23/2012


    Thanks a lot. This time, you have addressed all the issues directly, as such, many of your explanations have gone down my heart You have well illustrated thru the example many movies, but thing is that I don’t see movies. As such, these examples do not make any sense to me. During past 22 years, I have not seen even a single movie in a multiplex or theater, not even Hindi movie ( I reside in New Delhi, India). However, occasionally I see movies on TV. Nevertheless, your detailed elaborations have made sense to me.

    However, some more ideas still linger in my heart. I would like to share same with you.

    i) When speeding twin shall return to earth, he will have permanent relativistic changes w.r.t left over twin at earth. Since Time does not flow in the reverse direction, therefore, TD once gained will not be cancelled. I agree and understand this. However there should also be permanent relativistic change in mass. Whether Time is a dimension or some physical stuff has remained subject to discussions of philosphers and scientists since millennia, but there has been no such controversy over mass (matter). Matter (mass) has always been considered a hard physical stuff by physicists – a reality, no controversy over this.

    When speeding twin returns to earth, he will have changed mass w.r.t mass he was having before leaving earth. How do you view this permanent change of mass on physical paradigm in terms of atomic structure? What will happen to constituents atoms — will nos increase or mass of each atom increase or energy binding atoms shall increase? None of these explanation fits my mind.

    ii) I understand your elaboration that relativistic changes in frame Y (near BH) shall be relevant as long as they are being observed from another frame X i.e from earth. But an observer in frame Y shall not observe any change. Now I understand and agree with this view. Extending this logic a bit further, following issues can arise :

    a) In any frame of reference, an observer in THAT FRAME shall observe certain values of TIME, MASS, LENGTH which should be independent of speed of that reference or gravitational force acting on that reference. For relativistic changes to be relevance, observations should be made from some other reference. It means whatever values we observe of MASS, LENGTH, TIME at earth, we as observer shall observe SAME values near BH or in any speeding frame, provided we are a part of that frame.

    Above implies, Mass, length and time in ANY FRAME have some CONSTANT values, irrespective of the speed/acting gravitation force on THAT FRAME w.r.t any other frame.
    Does my this interpretation makes any sense to you? If yes, please try to think how those constant values are fixed and if some revelation comes across, please share with me.

    ii) Time Dilation (TD) of any speeding frame shall be observable from another frame w.r.t which speeding frame is speeding. Suppose at some observable speed, Time becomes zero, what will happen further ? Will observer cease to observer further increase of speed also since time reversal is prohibited.

    iii) There will or should be some frame in universe, WHEN OBSERVATIONS BEING MADE FROM THAT FRAME OF ANOTHER FRAME, time of observed frame may become zero. what will be then the meaning of observations of mass, length?
    In a way, universe of observed frame from observational frame should vanish.

    I know above issues are not the basic ideas of relativity. I am also not asking you to necessarily ponder over above issues and respond. However, you can continue to mull over above issues and share if some new revelation dawns over upon you.

    Thanks for your advice to me for reading some text books on relativity. But I am already 57, as such, it is not possible to enter any college or university or to have formal education from any teacher. It is only thru self pondering over or by discussions with people like you that some conceptual understanding emerges out

    Link to this
  23. 23. Cramer 4:20 pm 07/23/2012


    You said, “This time, you have addressed all the issues directly.”

    I simply repeated mostly what I had already said. “This time” I replied in question and answer format rather than paragraph format.

    I also do not go to the movies. The movies I referenced are very old. Here are the youtube clips of the scenes:

    Star Trek IV: The Voyage Home (1986) – Time Warp Back to 1986
    [Note: "slow motion" effects begin at time at 2:20.]

    Planet of the Apes (1968) – Opening Scene where Charleton Heston talks about time travel:

    Planet of the Apes (1968) – Final Scene

    Escape from the Planet of the Apes (1971) – Trailer

    Link to this
  24. 24. Cramer 4:43 pm 07/23/2012


    i) Time Dilation vs Relativistic Mass
    I don’t believe I can easily explain this in a few paragraphs. Time dilation is eliminated by the twin returning to the original reference frame (i.e. both clocks run at same speed) in the same way that relativistic mass returns to equaling rest mass. Time involves the past (can’t change the past). Even Einstein and other scientists have had difficult times thinking of relativistic mass because rest mass is invariant. See
    Note the quote by Einstein near end of article.

    iia) This is the first postulate of special relativity: The laws of physics are the same in all inertial frames of reference.

    iib) Time becoming zero is how many view photons. In our inertial frame it takes around 8 minutes for a photon to travel from the Sun to Earth. For the photon, it happens instantaneously (photons “observe” our inertial frame as happening instantly fast — so their trip is instant). Measuring time in another inertial frame can only happen by observing EM signals at periodic rates. The signals just stop being observed. This is the paradox (but in GR) that I suggested with matter falling into a BH. We never observe it happening due to time dilation, but BH’s do grow. [How, I believe, it is by black holes merging, not by matter falling in. Matter falling-in is most likely ejected as energy. But that's just my idea -- not science.]

    iii) Observed changes in time, length, mass in SR are all related by the Lorentz factor.

    Special relativity would not be a major undertaking. It is mainly conceptually and is explained easily in diagrams. The math is very, very simple. The math and concepts of SR are derived on two postulates: 1) laws of physics are the same in all inertial frames; and 2) Invariance of c – The speed of light in a vacuum is independent of the motion of the light source.

    You could learn it from wikipedia, but it not as well done as in a text book.

    The wikipedia article does not have very good diagrams (likely due to copyright issues). A textbook would give good diagrams.

    At least visit your bookstore or library and browse a chapter on SR in a general physics undergrad text; and you should see what I mean.

    Check out Chapter 37 in this book (look at the detailed table of contents on page xix):

    GR is a different beast — much, much, more difficult math.

    Link to this
  25. 25. vinodkumarsehgal 12:03 pm 07/25/2012

    To Cramer

    Thanks for providing many links of You tube and wikipedia and some books to enable me to have better conceptual understanding of relativity. But frankly speaking some of your quotes on TD in post 24 have added to my confusion.
    I shall explain why?

    In my post 19, I had indicated that when speeding twin shall come back to earth, he will not have any TD. My contention was that since TD was primarily due to speed and when he will return to earth, primary cause due to which TD had developed also being over, therefore TD should not persist.

    Against my above contention, you responded in your post 20 that it is true that primary cause of TD i.e. speed on returning of speeding twin to earth shall be over and again clocks of speeding twin shall run at the normal speed as on earth implying NO FURTHER TD SHALL BE ACCUMULATED IN CLOCK OF SPEEDING TWIN WHILE WHILE HE BEING ON EARTH. BUT TD WHICH HAD ALREADY ACCUMMULATED IN THE SPEEDING FRAME OF SPEEDING TWIN, WHILE HE BEING AWAY FROM EARTH, SHALL PERSIST. For the TD to be realistic phenomenon, TD accummulated in speeding frame should persist on returning to earth. SPEEDING TWIN SHALL LAND ON EARTH IN THE FUTURE TIME OF EARTH ONLY IF ACCUMMULATED TD, WHILE IN SPEEDING FRAME AWAY FROM EARTH, SHOULD PERSIST ON RETURN TO EARTH ALSO. OTHERWISE, HOW IT IS POSSIBLE THAT RETURNING TWIN MAY LAND IN THE FUTURE TIME OF EARTH? I am duplicating your quotes of post 20

    “Yes, time dilation, Lorentz contractions, etc no longer persist when two observers are in the same inertial frame of reference — clocks once again run at the same speed. I believe I made that clear — that’s RELATIVE-ity — it’s the basic core concept. However, the changes that did occur when the observers were in different reference frames were NOT an ILLUSION. For example, when a twin returns he may find himself (depending on velocity, etc) 1000s of years in the future — his twin brother is dead. It does NOT work like the Planet of the Apes films.”

    When speeding twin shall return to earth, though he will be in his present time, but his present time shall be future time of left over twin on earth and other people of the earth. Though this interpretation has many implications, which we may find difficult to explain but I agreed with this interpretation since TD to be realistic, once accummulated in a speeding frame away from earth, should not vanish even after return of speeding twin back to earth. You gave the contention that time can not flow in the reverse direction. I also agree with this, therefore, I finalized my view that speeding twin on return to earth shall land back on earth in the FUTURE TIME OF EARTH since TD earned during speeding frame away from earth should persist

    Now in your post 24, you are mentioning that TD shall be eliminated when speeding twin shall return to earth.

    “Time dilation is eliminated by the twin returning to the original reference frame (i.e. both clocks run at same speed) in the same way that relativistic mass returns to equaling rest mass. Time involves the past (can’t change the past).”

    Your interpretation of TD in post 20 and 24 appear mutually contradictory to me ( I AM NOT ASSERTING THAT THEY ARE CONTRADICTORY BUT THIS HAS APPEARED TO ME). I also agree that clocks shall again run at the same speed BUT WHAT ABOUT TD ACCUMMULATED IN THE SPEEDING FRAME WHEN TWIN WAS AWAY FROM EARTH? Speeding twin shall land at earth in the future time of earth only if TD earned during speeding frame also persist, while during the stay of speeding twin back on earth, and THIS PERSISTENCE ONLY SHALL TAKE RETURNING TWIN TO THE FUTURE TIME OF EARTH ( though he will be in his present time)

    I applied the above contention of persistence of accummulated TD to the phenomenon of relativistic mass change and relativistic length contraction and, therefore, in my post 23 I raised the issues of intrinsic change in the atomic structure of matter when it returns to original frame after spending some time in speeding frame. As advised by you, I went thru the wikilink on relativistic mass and the quotes of Einstein in his letter of June 1948 which he might have written to some of his friend. Einstein’s propounded SR in 1905 and it seems he revised his views regarding mass change in 1948 i.e. after a period of 43 years. When people of the genius and calibre of Einstein remained confused regarding the realism of mass change,it is natural that we people who are layman shall remain confused. Same view should remain applicable on length contraction also. Since if it is realistic, once accummulated during speeding frame, it should persist on returning to original frame also THOUGH FUTURE CHANGES SHOULD NOT TAKE PLACE SINCE PRIMARY CAUSE WHICH BROUGHT OUT LENGTH CONTRACTION SHALL NO LONGER EXIST ON RETURNING TO ORIGINAL FRAME AT EARTH. It is natural that further queries shall arise regarding the structure of object whose length has contracted. Suppose a ruler which was 12 inches, while in original frame at earth, remained in a speeding frame away from earth for one year and depending upon its speed suppose its length contracted to 8 inches. In the speeding frame, its length shall be visible as 12 inches to an observer in that speeding frame (local frame) but to a remote observer it will be visible as 8 inches. ( Am I right in this interpretation?)

    Now when rules shall return to its original frame on earth, for length contraction to be realistic length difference of 4 inches should become a permanent feature though no future length change shall take place since primary cause i.e relativistic speed which brought length change is over . But here we are faced with difficult issues regarding structure of the object whose length has really changed for which we no answer

    Mr Cramer, logic of realistic persistence of accummulated TD should apply to mass change and length change also, if persistence of TD on returning to earth is a realistic phenomenon.

    May be we can go away with the phenomenon of persistence
    of accummulated TD in speeding frame on return to earth ( than only returning speeding twin shall land in the future time of earth) SINCE TIME BEING AN ABSTRACT QUANTITY, THEREFORE, NO QUESTIONS CAN BE ASKED REGARDING CHANGE IN ITS STRUCTURE. But mass and length are not abstract quantities, these are some solid tangible objects, therefore, change in their structure can be examined.

    I do not what is the final truth since relativity is really mysterious, there, there have been discussions on this even after 100 years of propounding of SR and MYSTERY OF TIME IS EVEN MORE DIFFICULT TO UNDERSTAND.

    Link to this
  26. 26. Cramer 6:55 pm 07/25/2012

    Direction of traveler does not matter. It doesn’t matter if a traveler is speeding away from the Earth or speeding toward the Earth on the return trip. All that matters is that both people are not moving together in the same inertial frame [i.e. one would have to accelerate or decelerate to be in the same frame as the other.] I don’t know if that’s the source of your confusion. This topic is not easily explained by exchanging paragraphs. I suggest you read the SR chapter in a physics book.

    Link to this
  27. 27. vinodkumarsehgal 3:09 am 07/26/2012

    To Ceamer

    I have a very straight and simple query which is not very difficult for any person to comprehend :

    i) Suppose a person leaves New York city in 2012 on a speeding spaceship and he takes along with him a clock, a weight of 1 Kg and a ruler of 12 inch. Suppose he stays in speeding spaceship for 1 year and speed of ship is such that it provides a Lorentz factor of 100.

    Above implies that period of 1 year (as per the local time of spaceship) passed in spaceship shall be equivalent to 100 years of period as per the local clock of New York back on earth. Further, though there shall be mass increase and length contraction, say ruler length decreased to 8 inches and mass of 1 Kg may become 0.6 Kg, due to speed BUT same shall not be observable by the person in the spaceship but these shall be observable to a person left behind in New York. My main contention for this interpretation being that for relativistic changes being to be observable, prerequisite is that relativistic change in speed should be observable to the observer, And this shall be applicable upon remote observer back on earth and NOT upon the observer in space ship.


    ii) Now after spending 1 year in deep space, spaceship commences its return journey and lands back at earth. I agree that since relativistic speeds no longer exist, therefore, no further relativistic TD (clock of spaceship shall start running at usual speed), mass changes and length contraction shall take place. Up to this point it is OK.

    BUT THE MOST PERTINENT QUESTION WHICH ARISES : WHAT WOULD HAPPEN TO RELATIVISTIC CHANGES IN TIME, MASS AND LENGTH WHICH WERE GAINED DURING THE STAY IN SPEEDING FRAME FOR 1 YEAR. Initially, I had opined in my post 18 and 19 that accummulated relativistic changes should vanish during during the return journey provided return journey follows the same trajectory and speed as during the outward journey. However, in your post 20 you corrected me that relativistic changes once developed can not be reversed and you also gave the contention that TIME CAN NOT FOLLOW IN THE REVERSE DIRECTION. I agreed with your interpretation since this was based upon sound logic and rational approach.

    However, in your current post 26 you are mentioning of return journey.

    “Direction of traveler does not matter. It doesn’t matter if a traveler is speeding away from the Earth or speeding toward the Earth on the return trip. All that matters is that both people are not moving together in the same inertial frame [i.e. one would have to accelerate or decelerate to be in the same frame as the other.]”

    What is the relevance of above paras with the fact of persistence of accummulated TD, mass change and length contraction. I do not understand the relevance of your above quotes in the context of my query; whether accummulated relativistic changes in Time, Mass and length persisr while back on earth.

    iii) To summarize above, my specific, straight and direct queries are :

    a) After completion of 1 year in speeding space ship with Lorentz factor of 100, WILL THE PERSON LAND BACK IN NEW YORK CITY OF 2013 OR 2113?

    The interpretations which you have given so far makes me to change my view that PERSON SHALL LAND IN NEW YORK OF 2113. I have finalized this view due to contention that TD once arisen can not be erased back.

    Above interpretation shall amount to realistic changes in relativistic changes and bar on their reversal once gained.

    However, I wanted your specific and final confirmation for the above view

    ii) If above logic of TD is made applicable on mass changes and length change, back on earth , should not the following phenomena happen ( By mass, I mean rest mass before commencing of outward journey and NOT relativistic mass rest mass + mass due to kinetic energy):

    Ruler length of 12 inch should reduce to 8 inches and 1 Kg should become 0.6 Kg i.e same values as were within spaceship.

    If above interpretation is wrong, a question shall arise where and how relativistic changes gained during spaceship have vanished.

    I wanted your specific and final interpretation on above queries also

    Mr Cramer, Are my above queries yet not clear to you? I always want to have CLEAR UNDERSTANDING of issues by adressing from front. I do not insist upon your addressing all these issues. I ALSO DO NOT ASSUME THAT YOU MAY HAVE NECESSARILY COMPLETE INTRICATE UNDERSTANDING OF ALL THE ISSUES AS RAISED BY ME. But from your comments, it appears to me that you have fair amount of understanding relativity which definitely is higher than mine understanding.

    Text books are important, no doubt, but definitely they do not address such issues in such direct and straightforward manner as we have been discussing.

    Important thing is that if some issues are unresolved, we may admit our incapability to resolve rather than to resolve thru some forced and vague conventional interpretation.

    If you want, you can also send me your comments on my mail

    Link to this
  28. 28. vinodkumarsehgal 3:15 am 07/26/2012

    To Cramer

    Sorry,In my previous post 27,I inadvertently mentioned mass of 1 Kg to become mass of 0.6 Kg. Mass in speeding frame should increase and NOT decrease as I indicated due to mistake. Therefore let us presume mass becomes 1.4 Kg. Kindly do not go by verbatim meaning but see the spirit from which I raised the issue

    Link to this
  29. 29. Cramer 11:47 pm 07/26/2012

    100 years would pass on Earth.
    Ruler would be observed as 0.01 ft from Earth.
    Mass would be observed as 100 kg from Earth (mass would be measured by Newton’s 2nd law, F=d(mv)/dt).

    The rest sounds correct.

    ii. I made the comment about direction not mattering due to my interpretation of your comment. I thought you believed direction of traveler was relevant for time dilation. I guess I misinterpreted your comment.

    iii. a) arrive back on Earth in 2112 New York time. Spaceship time would be 2013. In the Planet of the Apes video (first scene of 1968 movie), they actually show the two clocks labeled “Earth Time” of 2673 and “Ship Time” of 1972 (their trip was not yet complete).

    iii. b) mass on spaceship would be measured on spaceship as 1 kg. Ruler as observed on spaceship would be 12 inches. [That is, one meter would be the distance traveled by light in 1⁄299,792,458 of a second.]

    Link to this
  30. 30. vinodkumarsehgal 12:33 am 07/27/2012


    Thanks for your comments

    Ref iii b) post 29

    I have well understood that in speeding spaceship mass and ruler shall be observed as I kg and 12 inches resp.
    ( due to nil relativistic speed change) But my query pertained to these values back on earth ( after gaining relativistic changes as observable from earth)

    But what would be the mass back on earth? Will it be 1 Kg Or 100 Kg as was in spaceship while in speeding frame?

    Similarly, back on earth, will ruler maintain its original length of 1 ft OR will it reduce to 0.01 ft as was within speeding framework

    Why I am asking the above questions? Primarily due to two reasons :
    a) If back on earth, mass and length becomes 1 Kg and 1 ft, this will amount to reversal of relativistic mass and length changes, as gained during ship which is not permissible as per relativity.

    b) If back on earth, ruler and mass maintains relativistic changes as gained during speeding spaceship i.e back on earth, ruler becomes 0.01 ft and mass becomes 100 kg, then how to explain this in terms of atomic structure. Mass is increasing and length is decreasing

    Both a) and b) lead to a situation of conundrum. If you have some solution, please suggest

    Link to this
  31. 31. vinodkumarsehgal 1:04 am 07/27/2012

    Mr Cramer

    Regarding TD, when I think more deeply it seems to lead to a very complex situation which is very difficult for us to comprehend.

    When speeding spaceship shall land back in New york, the person in that ship ( who had gone along with the ship) will observer the New York of 2112 while all the left behind inhabitants will see New york of 2013. The person, who had gone along with ship, will see new buildings, new roads, new people who as per local time of New York (2013) have yet not even taken birth, new gardens WHICH AS PER LOCAL TIME OF NEW YORK(2013) HAVE YEST TO COME INTO EXISTENCE. Will it not lead to violation of cause-effect relations? This will imply that all the events in future are predetermined but due to our inability to jump into future, we are unable to know those. If he describes all the situation of 2112 in a book, local people of New york will find all those detail after 99 years ( from 2013 to 2112).

    When I visualize above , a very weird and bizarre situation appears to emerge out

    Further, following question arises:

    a) Will the person who has landed back in New york of 2112 be in communication with the left over people of New York of 2013?

    b) Will the person have knowledge of New York for the period from 2013 to 2111? This is the period past to that person

    Mr Cramer, my endeavour is to understand the reality of relativity on physical paradigm. You may also agree with me that if we can not understand any reality on physical paradigm, any theory and mathematical formulations, however, elegant they may be are not of much significance.

    If some revelations comes across you, please suggest the same

    Link to this
  32. 32. vinodkumarsehgal 2:59 am 07/27/2012

    To Cramer

    You please ignore my interpretation in post 31. I pondered over again and it came to me that all the left over New york of 2012 will also move in future in 2113 along with the person landed back from speeding frame. As such, there is no question of any bazarre and weird situation.

    In my subconscious, I was having Time travel in future ( by the person returned from speeding ship) and left over people of New york in their present. If this situation may arise on earth, this will really lead to a bizarre situation as painted by me in my post 31. I actually mixed the phenomenon of TD with time travel in the same frame. TD is a also a sort of Time travel but in different frames. While remaining in New york ( year 2012)local frame, if a person reaches New york of 2112, then the situation can emerge as painted by me in 31. I think present theoretical and technological developments
    do not permit this scenario
    However, my conundrum as indicated in post 30 persist. Reason? TD as gained during speeding frame persists on returning back to original frame but mass gain and length contraction vanishes on returning. Real values of mass and length are the values which were before departure of spaceship. During speeding frame, addition of mass due to kinetic energy strictly speaking does not amount to addition of any mass. same thing remains applicable on length also

    Link to this
  33. 33. Cramer 1:37 pm 07/27/2012

    Vinod, the textbooks will give you good diagrams of measurements being made which should answer your questions. I am now on holiday/vacation and will not be available. I hope you will find answers for your questions.

    Link to this

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