Spyman

I agree. You should not provide a consensus--provide evidence or scholarly papers instead. /snip/ Oh no, you do not get to just brush this under the carpet and then request for new references. I did provide evidence on scientific consensus in the matter of black holes and at this point I think you really need to clarify your position about it much much better. Do you or do you not agree that the standard black hole model is a well established part of mainstream physics and that current scientific consensus holds black holes to be consistent with the theory of general relativity and current observations? And IF you don't agree that the current status of scientific consensus is as I have represented it, then you need to explain what's wrong with my references and provide evidence of the negative nature of scientific consensus regarding the standard black hole model and any falsifying observations that have been made.

Oh well that's also possible without drinks. And, I'm not claiming to have solved it, or that I can. I am sorry, that was meant to be a funny joke on the "Champagne" part and not intended to be personal nor aimed at you. For the rest of your posts, you seem to misinterpret both the metaphor of the bread & the balloon analogies and have some misconceptions about the Big Bang theory that clouds your judgement of modern cosmology. The Big Bang theory is not about an explosion in the center of space flinging objects apart, (like bubbles in champagne), instead it is about a change in the scale of our metric system. You should examine the implications of a metric expansion and how it would differentiate from objects physically moving outward from a center. "The metric expansion of space is the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion whereby the scale of space itself is changed. That is, a metric expansion is defined by an increase in distance between parts of the universe even without those parts being displaced from their initial locations. This is a different kind of motion than that usually described in kinematics and it also differs from other examples of expansions and explosions in that, as far as observations can ascertain, it is a property of the entirety of the universe rather than a phenomenon that can be contained and observed from the outside." http://en.wikipedia.org/wiki/Metric_expansion_of_space You might also want to take a closer look at the current observational evidence in favor for a metric expansion without a center, it appears to be much more robust than what your latest post indicate. "Observational evidence Theoretical cosmologists developing models of the universe have drawn upon a small number of reasonable assumptions in their work. These workings have led to models in which the metric expansion of space is a likely feature of the universe. Chief among the underlying principles that result in models including metric expansion as a feature are: the Cosmological Principle which demands that the universe looks the same way in all directions (isotropic) and has roughly the same smooth mixture of material (homogeneous). the Copernican Principle which demands that no place in the universe is preferred (that is, the universe has no "starting point"). Scientists have tested carefully whether these assumptions are valid and borne out by observation. Observational cosmologists have discovered evidence - very strong in some cases - that supports these assumptions, and as a result, metric expansion of space is considered by cosmologists to be an observed feature on the basis that although we cannot see it directly, scientists have tested the properties of the universe and observation provides compelling confirmation. Sources of this confidence and confirmation include:Hubble demonstrated that all galaxies and distant astronomical objects were moving away from us, as predicted by a universal expansion. Using the redshift of their electromagnetic spectra to determine the distance and speed of remote objects in space, he showed that all objects are moving away from us, and that their speed is proportional to their distance, a feature of metric expansion. Further studies have since shown the expansion to be extremely isotropic and homogeneous, that is, it does not seem to have a special point as a "center", but appears universal and independent of any fixed central point. In studies of large-scale structure of the cosmos taken from redshift surveys a so-called "End of Greatness" was discovered at the largest scales of the universe. Until these scales were surveyed, the universe appeared "lumpy" with clumps of galaxy clusters and superclusters and filaments which were anything but isotropic and homogeneous. This lumpiness disappears into a smooth distribution of galaxies at the largest scales. The isotropic distribution across the sky of distant gamma-ray bursts and supernovae is another confirmation of the Cosmological Principle. The Copernican Principle was not truly tested on a cosmological scale until measurements of the effects of the cosmic microwave background radiation on the dynamics of distant astrophysical systems were made. A group of astronomers at the European Southern Observatory noticed, by measuring the temperature of a distant intergalactic cloud in thermal equilibrium with the cosmic microwave background, that the radiation from the Big Bang was demonstrably warmer at earlier times. Uniform cooling of the cosmic microwave background over billions of years is strong and direct observational evidence for metric expansion. Taken together, these phenomena overwhelmingly support models that rely on space expanding through a change in metric. Interestingly, it was not until the discovery in the year 2000 of direct observational evidence for the changing temperature of the cosmic microwave background that more bizarre constructions could be ruled out. Until that time, it was based purely on an assumption that the universe did not behave as one with the Milky Way sitting at the middle of a fixed-metric with a universal explosion of galaxies in all directions (as seen in, for example, an early model proposed by Milne). Yet before this evidence, many rejected the Milne viewpoint based on the mediocrity principle. The spatial and temporal universality of physical laws was until very recently taken as a fundamental philosophical assumption that is now tested to the observational limits of time and space. " http://en.wikipedia.org/wiki/Metric_expansion_of_space#Observational_evidence

If you have had regular conversations with him for 6+ months, trust this person and value him as a friend, then I think sending him a facephoto is ok. If he has not sent you his photograph already then you should also request him for the same favor. Also your profile says that you are 14 years old, so even if he is only a friend, for a relation lasting so long I think your parents are entitled to get a little information about him and your relation, telling them is also a safeguard protecting your security just in case. [EDIT] However your profile also claims that you are male but the OP and following discussion suggests that you are the girl in question, making me slightly confused. Can you please clarify if you are the girl or the boy in the OP?

Champagne Cosmology -> after a few drinks you think you can solve the true reality of the universe. ( The only drawback is when the ideas really start to flow, it is nearly impossible to properly document the great discoveries you make.)

While the expansion of space is constant over distance it is not constant over time, in current models of big bang theory the Hubble constant has been changing over time. Shortly after the big bang event the expansion was very rapid but then gravity slowed it down until the universe became to large and dark energy started to speed up the expansion again. When the expansion is accelerating the radius to the sphere where space is expanding with the speed of light is decreasing, blocking out more and more of the universe outside but when the expansion is slowing down, as it did for billions of years after the BB event, the sphere was growing and light that was close outside, but unable to pass, got engulfed by its increasing radius. On the inside space is expanding slower than the speed of light so light that gets swallowed by a growing Hubble sphere can start to make progress and eventually reach us. There is currently a lot of very old photons inside our huge sphere moving towards us and event though the expansion of the universe is currently accelerating, they will keep coming for billions of years until the view from outside of Milky Way will go dark. "Since the Hubble "constant" is a constant only in space, not in time, the radius of the Hubble sphere may increase or decrease over various time intervals. The subscript '0' indicates the value of the Hubble constant today. Current evidence suggests the expansion of the universe is accelerating (see Accelerating universe), meaning that for any given galaxy, the recession velocity dD/dt is increasing over time as the galaxy moves to greater and greater distances; however, the Hubble parameter is actually thought to be decreasing with time, meaning that if we were to look at some fixed distance D and watch a series of different galaxies pass that distance, later galaxies would pass that distance at a smaller velocity than earlier ones." http://en.wikipedia.org/wiki/Hubble's_law

Reference, please, I shouldn't really have to provide a reference on scientific consensus in the matter of black holes, but here you go: "Objects whose gravity fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. The first modern solution of general relativity that would characterize a black hole was found by Karl Schwarzschild in 1916, although its interpretation as a region of space from which nothing can escape was first published by David Finkelstein in 1958. Long considered a mathematical curiosity, it was during the 1960s that theoretical work showed black holes were a generic prediction of general relativity. The discovery of neutron stars sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality. Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form. There is general consensus that supermassive black holes exist in the centers of most galaxies." http://en.wikipedia.org/wiki/Black_hole Or if you requested a reference that scientific work has been done to provide evidence of black holes: "High Proper Motion Stars in the Vicinity of Sgr A*: Evidence for a Supermassive Black Hole at the Center of Our Galaxy Over a two year period (1995-1997), we have conducted a diffraction-limited imaging study at 2.2 microns of the inner 6"x6" of the Galaxy's central stellar cluster using the Keck 10-m telescope. The K band images obtained reveal a large population of faint stars. We use an unbiased approach for identifying and selecting stars to be included in this proper motion study, which results in a sample of 90 stars with brightness ranging from K=9-17 and velocities as large as 1,400+-100 km/sec. Compared to earlier work (Eckart et al. 1997; Genzel et al. 1997), the source confusion is reduced by a factor of 9, the number of stars with proper motion measurement in the central 25 arcsec^2 of our galaxy is doubled, and the accuracy of the velocity measurements in the central 1 arcsec^2 is improved by a factor of 4. The peaks of both the stellar surface density and the velocity dispersion are consistent with the position of the unusual radio source and blackhole candidate, Sgr A*, suggesting that Sgr A* is coincident (+-0."1) with the dynamical center of the Galaxy. As a function of distance from Sgr A*, the velocity dispersion displays a falloff well fit by Keplerian motion about a central dark mass of 2.6(+-0.2)x10^6 Mo confined to a volume of at most 10^-6 pc^3, consistent with earlier results. Although uncertainties in the measurements mathematically allow for the matter to be distributed over this volume as a cluster, no realistic cluster is physically tenable. Thus, independent of the presence of Sgr A*, the large inferred central density of at least 10^12 Mo/pc^3, which exceeds the volume-averaged mass densities found at the center of any other galaxy, leads us to the conclusion that our Galaxy harbors a massive central black hole." http://arxiv.org/abs/astro-ph/9807210

No, I am not irritated, I simply question to your intent with this thread, because you ask for evidence of black holes, but when presented with such you react very negatively. This is again obvious in your reply to me, where you keep on questioning my skills and whether I follow authority without thinking for myself. If all you want is to vent off some steam and bash on the science channel, then I can understand that, but if you are trying to achieve something else, you should stop beat around the bush and come clear with a good explanation of what you really want. Claims that scientific consensus is "pseudo science" and that their "followers" are like religious belivers only damages your own credibility. So far I don't consider you to have gotten even close to shot down the scientific consensus in the matter of black holes. Further more I don't have to provide evidence for established mainstream physics, that has already been done by professional scientists in that area of research. If you on the other hand want to disprove their work, then you are the one in need of providing evidence, and so far your evidence is insufficient.

You can't count that we are 13.8 billion years old and then add the age of the light on top of that, this place where we are and the stuff that we are made of, are of equal age as the photons in the light we see from the edge of our view. The age of the Universe is assumed to be equal everywhere inside the Universe, there is no location that is older than anyone else. The entire Universe is thought to come from the same moment, making all places and original energy to be of equal age. However since light has a finite speed, photons emitted from distant places need more time to reach us and will therefore show us things that happened a long time ago when the Universe was younger. If it takes light 13.8 billion years to reach us from the edge of our visible universe then our visible universe needs to be around 13.8 billion years old, if the universe was younger then the distant light would not have enough time to reach us and if the universe was older then we should be able to see light from more distant parts further away. (Note: Not included in this simple explanation is the expansion of space, the cosmic microwave background radiation and other things complicating our view.)

Also in addition to what swansont and imatfaal have said, the event horizon is not at the centre or inside, it's considered to be the surface of the black hole. An observer in free fall can survive the gravitational field close to the event horizon of a supermassive black hole because the tidal forces at the more distant horizon weakens with increasing mass, such that very very massive black holes can have even smaller tidal forces than what Earth has on its surface.

Actually the Moon will never leave Earth, while it is true that the Moon recedes from Earth with almost 4 centimeters per year, it's not true that this will cause us to lose the Moon. The Moon is receding due to tidal interactions with Earth and if allowed to continue undisturbed it will cause the Moon and Earth to end up in tidal locking where both the Moon and the Earth will always have the same face against each other. When this happens the Moon will stop receding from Earth. However calculations suggests it will take about fifty billion more years before this happens and the Sun will become a red giant long before that, already in about 2.3 billion years from now it will be hot enough to vaporize Earth's oceans which will dramatically lessen tidal interactions. Tidal evolution The gravitational attraction that the Moon exerts on Earth is the major cause of tides in the sea; the Sun has a lesser tidal influence. If the Earth possessed a global ocean of uniform depth, the Moon would act to deform both the solid earth (by a small amount) and ocean in the shape of an ellipsoid with high points directly beneath the Moon and on the opposite side of the Earth. However, as a result of the irregular coastline and varying ocean depths, this idealization is only partially realized. While the tidal flow period is generally synchronized to the Moon's orbit around Earth, its phase can vary. In some places on Earth there is only one high tide per day, though this is somewhat rare. The tidal bulges on Earth are carried ahead of the Earth-Moon axis by a small amount as a result of the Earth's rotation. This is a direct consequence of friction and the dissipation of energy as water moves over the ocean bottom and into or out of bays and estuaries. Each bulge exerts a small amount of gravitational attraction on the Moon, with the bulge on the side of the Earth closest to the Moon pulling in a direction slightly forward along the Moon's orbit, because the Earth's rotation has carried the bulge forward. The bulge on the side furthest from the Moon has the opposite effect, but the closer bulge dominates due to its comparative closer distance to the Moon. As a result, some of the Earth's angular (or rotational) momentum is gradually being transferred to the Moon's orbital momentum, and this causes the Moon to slowly recede from Earth at the rate of approximately 38 millimetres per year. In keeping with the conservation of angular momentum, the Earth's rotation is gradually slowing, and the Earth's day thus lengthens by about 23 microseconds every year (excluding glacial rebound). Both figures are valid only for the current configuration of the continents. Tidal rhythmites from 620 million years ago show that over hundreds of millions of years the Moon receded at an average rate of 22 millimetres per year and the day lengthened at an average rate of 12 microseconds per year, both about half of their current values. See tidal acceleration for a more detailed description and references. The Moon is gradually receding from the Earth into a higher orbit, and calculations suggest that this would continue for about fifty billion years. By that time, the Earth and Moon would become caught up in what is called a "spin-orbit resonance" or "tidal locking" in which the Moon will circle the Earth in about 47 days (currently 27 days), and both Moon and Earth would rotate around their axes in the same time, always facing each other with the same side. (This has already happened to the Moon - the same side always faces Earth. This is slowly happening to the Earth as well.) However, the slowdown of the Earth's rotation is not occurring fast enough for the rotation to lengthen to a month before other effects change the situation: about 2.3 billion years from now, the increase of the Sun's radiation will have caused the Earth's oceans to vaporize, removing the bulk of the tidal friction and acceleration. http://en.wikipedia.org/wiki/Orbit_of_the_Moon#Tidal_evolution

Ohh - really? You don't seem to be very eager to find any such evidence or even be objective enough to listen to arguments in favor of black holes. IMHO your personal dislike for "black hole lovers" is a major obstacle IF your quest truly is to learn and understand. [EDIT] Double post removed.

While special relativity constrains objects in the universe from moving faster than the speed of light with respect to each other, it places no theoretical constraint on changes to the scale of space itself. It is thus possible for two objects to be stationary or moving at speeds below that of light, and yet to become separated in space by more than the distance light could have travelled, which can suggest the objects travelled faster than light. For example there are stars which may be expanding away from us (or each other) faster than the speed of light, and this is true for any object that is more than approximately 4.5 gigaparsecs away from us. We can still see such objects because the universe in the past was expanding more slowly than it is today, so the ancient light being received from these objects is still able to reach us, though if the expansion continues unabated there will come a time that we will never see the light from such objects being produced today (on a so-called "space-like slice of spacetime") because space itself is expanding between Earth and the source faster than their light can reach us. http://en.wikipedia.org/wiki/Metric_expansion_of_space

The collaboration between humans and our furry friends have very likely been to our advantage, otherwise we would hardly still continue to live together with them. This partnership must also have effected both sides over the ages. If there was a competition where we wiped out all others and we had already started to use animals so early, then our animals certainly was to our advantage. However we don't really know what happened to the other subspecies of humans and their relations with other animals.

Actually there was three tests of relativity: Albert Einstein proposed three tests of general relativity, subsequently called the classical tests of general relativity, in 1916 the perihelion precession of Mercury's orbit the deflection of light by the Sun the gravitational redshift of light http://en.wikipedia.org/wiki/Tests_of_general_relativity

"According to General Relativity, gravitational time dilation is copresent with the existence of an accelerated reference frame." http://en.wikipedia.org/wiki/Gravitational_time_dilation#Important_things_to_stress

I know this is a few years old, maybe outside the scope of this contest, but it still makes me smile. Also +1 to Moontanman for the great idea of this fun and friendly competition.

It is the half of your first sentence, quoting it in its whole doesn't make it look much better. Are not kristalris allowed to start his/her own threads? If he/she asked you to start this thread, then why didn't you say that instead of ranting about personal habits? Can't kristalris participate in other threads anymore, is he/she forced/locked to only this thread?

Independent of kristalris past behaviour, I strongly dislike threads with a purpose to single out a member and put him/her in the spotlight. It is even more disturbing when it is done by a member of the staff! If someone needs to be corrected it should be done in the thread where the misconduct has been made and if ydoaPs want to discuss Bayes' theorem this thread could have started without pointing fingers and a simple PM could have invited kristalris to the discussion instead. Therefore I will both report the OP and vote negative on it.

So do you consider everyone, who don't agree with you that mainstream science are making outlandish unsubstantial claims with the standard black hole model, to be faithful black hole lovers, unthinking followers of authority and without a piss ant's education in relativity beyond the special theory or was that rant aimed at me personally?

The scientific consensus don't agree with you, the standard black hole model is a well established part of mainstream physics. I consider the singularity to be a likely sign of breakdown in the standard model and think that a working theory of quantum gravity will change this, however it's very probable that the standard model will still be a good approximation, far down inside a remaining event horizon feature. Well, I am not a native english speaker so my grammar might be flawed, I am sorry if this is causing you trouble to understand me. I meant that alternative models are MORE speculative than the standard model. If you want to interpret that as I said the standard model is speculative, then feel free to go ahead and do so, they are all models and not the real thing, none of them are 100 percent certain to remain true forever. Which according to your own words in the OP are "insufficient", if you want to replace the standard model with something more complicated, it is not enough to bring the same evidence, (which on top of everything you yourself think is lacking), you need to bring better evidence or a repeatable test able to discern between them by ruling one model out. You have not put forward convincible arguments that the incipient black hole model is more than a viable but still only an alternative model.

Good for you! There is nothing wrong with a sceptical view - just don't forget that incipient black holes that takes an infinite time to form and other speculative non black hole models are more extraordinary and have even less evidence than the standard black hole model.

While we don't have direct evidence, the theory of relativity is well tested and from it and our current knowledge of nature we can infer that black holes are inevitable, we don't know of any reason at all for why they should not form. Our observations match predictions made by our models of black holes and we don't have any other explanation for the Sagittarius A* region in our Milky Way galaxy. "Currently, the best evidence for a supermassive black hole comes from studying the proper motion of stars near the center of our own Milky Way. Since 1995 astronomers have tracked the motion of 90 stars in a region called Sagittarius A*. By fitting their motion to Keplerian orbits they were able to infer in 1998 that 2.6 million solar masses must be contained in a volume with a radius of 0.02 lightyears. Since then one of the starscalled S2has completed a full orbit. From the orbital data they were able to place better constraints on the mass and size of the object causing the orbital motion of stars in the Sagittarius A* region, finding that there is a spherical mass of 4.3 million solar masses contained within a radius of less than 0.002 lightyears. While this is more than 3000 times the Schwarzschild radius corresponding to that mass, it is at least consistent with the central object being a supermassive black hole, and no "realistic cluster [of stars] is physically tenable"." http://en.wikipedia.org/wiki/Black_hole#Galactic_nuclei How would the material in such a highly collapsed object maintain its shape against the enormous internal pressure from its own gravity? "The TolmanOppenheimerVolkoff limit (or TOV limit) is an upper bound to the mass of stars composed of neutron-degenerate matter (i.e. neutron stars). The TOV limit is analogous to the Chandrasekhar limit for white dwarf stars. It is approximately 1.5 to 3.0 solar masses, corresponding to an original stellar mass of 15 to 20 solar masses. The limit was first computed by J. Robert Oppenheimer and George Volkoff in 1939, using the work of Richard Chace Tolman. Oppenheimer and Volkoff assumed that the neutrons in a neutron star formed a degenerate cold Fermi gas. This leads to a limiting mass of approximately 0.7 solar masses. Modern estimates range from approximately 1.5 to 3.0 solar masses. The uncertainty in the value reflects the fact that the equations of state for extremely dense matter are not well known. The mass of PSR J16142230, 1.97±0.04 solar masses puts a lower bound on TOV limit. In a neutron star less massive than the limit, the weight of the star is balanced by short-range repulsive neutron-neutron interactions mediated by the strong force and also by the quantum degeneracy pressure of neutrons, preventing collapse. If its mass is above the limit, the star will collapse to some denser form. It could form a black hole, or change composition and be supported in some other way (for example, by quark degeneracy pressure if it becomes a quark star). Because the properties of hypothetical more exotic forms of degenerate matter are even more poorly known than those of neutron-degenerate matter, most astrophysicists assume, in the absence of evidence to the contrary, that a neutron star above the limit collapses directly into a black hole." http://en.wikipedia.org/wiki/TolmanOppenheimerVolkoff_limit According to our understanding a black hole forms from a huge star collapsing under its own weight, which implies that the main source of gravity would lie in the center, inside an outward growing event horizon. "Gravitational collapse occurs when an object's internal pressure is insufficient to resist the object's own gravity. For stars this usually occurs either because a star has too little "fuel" left to maintain its temperature through stellar nucleosynthesis, or because a star that would have been stable receives extra matter in a way that does not raise its core temperature. In either case the star's temperature is no longer high enough to prevent it from collapsing under its own weight. The collapse may be stopped by the degeneracy pressure of the star's constituents, condensing the matter in an exotic denser state. The result is one of the various types of compact star. The type of compact star formed depends on the mass of the remnantthe matter left over after the outer layers have been blown away, such from a supernova explosion or by pulsations leading to a planetary nebula. Note that this mass can be substantially less than the original starremnants exceeding 5 solar masses are produced by stars that were over 20 solar masses before the collapse. If the mass of the remnant exceeds about 34 solar masses (the TolmanOppenheimerVolkoff limit)either because the original star was very heavy or because the remnant collected additional mass through accretion of mattereven the degeneracy pressure of neutrons is insufficient to stop the collapse. No known mechanism (except possibly quark degeneracy pressure, see quark star) is powerful enough to stop the implosion and the object will inevitably collapse to form a black hole." http://en.wikipedia.org/wiki/Black_hole#Gravitational_collapse From my simple understanding, Hawking radiation requires an event horizon with the ability for particles to fall through it. "A slightly more precise, but still much simplified, view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle. http://en.wikipedia.org/wiki/Hawking_radiation There are other solutions showing that the singularity for the Schwarzschild solution at the event horizon is an illusion. "In 1924 Arthur Eddington produced the first coordinate transformation (EddingtonFinkelstein coordinates) that showed that the singularity at r = rs was a coordinate artifact, although he seems to have been unaware of the significance of this discovery. Later, in 1932, Georges Lemaître gave a different coordinate transformation (Lemaître coordinates) to the same effect and was the first to recognize that this implied that the singularity at r = rs was not physical. In 1939 Howard Robertson showed that a free falling observer descending in the Schwarzschild metric would cross the r = rs singularity in a finite amount of proper time even though this would take an infinite amount of time in terms of coordinate time t." http://en.wikipedia.org/wiki/Schwarzschild_metric

No, 500 000 Volts are not to be toyed with! Different individuals react differently to electric shock and the current can go through your body in plenty of unpredictable ways, you can never be sure that it won't harm you if it is able to penetrate your skin. Also how do you know that the transformer suddenly don't malfunction and release deadly levels?

"In physics, the Jeans instability causes the collapse of interstellar gas clouds and subsequent star formation. It occurs when the internal gas pressure is not strong enough to prevent gravitational collapse of a region filled with matter. For stability, the cloud must be in hydrostatic equilibrium, which in case of a spherical cloud translates to: , where is the enclosed mass, is the pressure, is the density of the gas at , is the gravitational constant and is the radius. The equilibrium is stable if small perturbations are damped and unstable if they are amplified. In general, the cloud is unstable if it is either very massive at a given temperature or very cool at a given mass for gravity to overcome the gas pressure." http://en.wikipedia.org/wiki/Jeans_instability

Yes, I was joking. If there was any intelligent life on Mars close to our explorers and they wanted to give us "some indication" of themself, then I think it's more likely that they would come forward to make contact instead of hiding and building rock like structures on the horizon. Even less intelligent creatures should be curious and cautious approach our explorers to examine them to determine their threat or value.