Green Baron

I know. Just wanted to steer the attention to a possible problem that could arise with something seemingly happening (expansion of Schwarzschild radius) "before" the cause (additional mass of object inside of it). Because i expected that to be the next question ;-) The linked text explains that quite nicely.

Nevermind :-) It was a suggestion against avoidable dust and storage problems.

Dust paints funny patterns on images, it will attract moisture, dust contains pollen which contain humid acids which will damage the coating of lenses as well as the aluminium surface of mirrors. No worries, if the cell holding the mirror is constructed and adjusted correctly nothing will drop out. Schmidt or Maksutovs are closed, dust won't enter too easily, but an open newton tube is a dust catcher. If there are only clips then ok, we probably are not talking about too high a value then ... :-) Refractors depend, oil spaced objectives are very delicate when stored on the side. If the objective's fitting isn't constructed perfectly the oil films can have different thickness over the aperture which will cause a 20.000,- objective to have a strehl of a 200,- mirror (0.8 instead of advertised 0.98). I've seen such an objective from a very well known and high valued brand on the optical bench of an independent tester. The owner was crying, he had spent the price of a midsize car for the tube and waited a long time. Air spaced aren't that prone to storage but still i would not store them on the side for a long time. There are few kg of glass held by screws in hopefully temperature compensated and stable non deforming steel or aluminium fitting. Apart from that, keeping things dry and clean is a must. Of course, the VLT or the Keck telescopes aren't dismounted during daytime :-)

Please ! Highly interested :-)

This can't be understood intuitively (foul excuse :-)). What can be measured from outside is the radiation from such events but this does not come from the Schwarzschild radius but from the area above, accretion disc and so on and this is clearly within the observable universe. The Schwarzschild radius is not, just until short above. So, in principle, the description of what happens at the event horizon is what mathematics imply. The "freeze" is not observable from outside because no information of it can escape (gravitational mass goes to infinite) and so probably your questions cannot be answered in our reference frame (time goes to division by 0). See it like this: the object stops at the event horizon and does not pass though, instead, the event horizon expands (and that without hurting causality, wow :-)). Here is what i found about it. Astrophysics can tell whether an object that is drawn towards a huge gravity well hits an event horizon (no signal) or a solid surface (energy burst on impact). When two black holes collide they are assumed to merge and form a single larger one. To understand more of this experiments to research gravitational waves have been and are being built. Ligo and Virgo for example. Edit: that Kevin Brown guy i linked above is somewhat of a mystery. Apparently he hasn't published more under that name, but was linked in the physics forum as well as in a university course so if you manage to wrap your brain around it then have fun :-)

You don't want dust on your telescope *jedihandwave* :-). Dust will spoil everything, visual and especially photographic. You will have a hard time cleaning all the surfaces, corners, screws, focuser, eyepieces from dust. Store it upside down (main mirror facing down), close all openings with lids. Since lids cost money manufacturers save them frequently, maybe you'd have to fabricate your own ones. When it has completely dried after viewing, strip a large plastic bag over it but leave it open at the bottom to avoid mould and open it every few days or so ...

The ship. It can cross it if not destroyed by gravitational forces or radiation of the accretion disc. In its reference frame it is not even aware that it has crossed an event horizon. But it cannot return. As it reaches the horizon time outside reaches infinity. Much has been speculated about what is inside but as far as i know physics cannot tell yet. Great unified quantum field bla theory is missing. Btw. gravitational time dilation as well as that by speed (which is essentially the same) is as real as the mouse you are holding. It is responsible for the orbit changes of Mercury, it was measured by satellites, it must be taken into account by the GPS. It is not magic :-) Nobody can watch it because energy from the Schwarzschild radius does not go anywhere except towards the gravitational center. All lines lead inwards, sotosay. Yeah, what you say describes it pretty well i think. I tried to avoid wikipedia except for the links i posted above. I have my half baked knowledge from cosmology books. Nope. The ships clock ticks just normal inside the ship. See above. The standstill is relative to an observer at rest (in the flat universe around). Physics doesn't say what happens at the event horizon, only short before. Just take a look at the formula on time dilation, when reaching speed of light it collapses into a 0 denominator, but just before it climbs very fast. In this wikipedia and my cosmology book agree that the ship stand s still at the event horizon relative to an observer in the flat universe. So, on the other hand, as that happens, the time of the universe has passed when the ship tries to cross the horizon. Sounds logical to me ...

idk But the Schwarzschild radius is actually a radius. The sun's is 3km (or was that the diameter ?), mine is smaller :-) It can't be observed directly because it does not reflect or radiate anything except maybe the hypothetical hawking radiation, but this is so faint that it can't be measured. Radiation of surrounding stuff is what deceives it, or jets from active galaxy cores, and indirect hints like movement of surrounding objects (Sagitarius A*). Stellar black holes are mostly incidents to find. Edit: Another one is https://en.wikipedia.org/wiki/Cygnus_X-1. See mass and caclculated event horizon diameter. The "object" itself can be smaller than the horizon, if that answers your question. I read that with the new generation of telescopes it might be possible to actually get an images of the effects of black holes, accretion disc, gravity lens, these sort of things. Interferometry - EHT laid/lais the foundations -, is the key to new insights. Onsights. Whatever. Patience we must have :-)

Spaceballs's Mega Maid comes to my mind :-) Nope, needs a ludicrous long cable.

To be precise, from my lay understanding: nothing with a rest mass can reach the limiting speed because its relativistic mass would become infinite (good old Lorentz-factor applies) and its impossible to accelerate an infinite mass. I am ignoring causality between reference frames here. (On the other hand, everything without a restmass has to travel at the limiting speed but that's not important here). So, to develop @sevenperforce idea further, you can accelerate from an elliptical orbit to a hyperbolic and thus leave a body, or fly by on a hyberbolic orbit and use gravity for acceleration (or deceleration). That's Newton's mechanics modeled as conic sections. But at the Schwarzschild radius Newton gives up and relativity takes over. A ship has to accelerate to the speed of light to hold position (which is impossible if it has restmass). But relativity says: for the outside universe watching such a ship it stands still as it reaches the horizon and will never cross it (this answers part one of op's question, you cannot dip below in the reference frame of a distant observer). Passengers inside the ship will not be aware of the standstill, time outside just passes faster and faster until it literally runs out, and this should answer the second part, that there is no coming back from the event horizon. Valid until a physicist overlooks this :-)

Wouldn't that have a better place in the lounge ? Cause it seems to be about a movie. At least it's far from science ... Edit: just read a critique about the movie. Life on the iss evolves that played part in an extinction on mars and now threatens earth. Aha. I see. :-) Yet another "alien". Not science. We'd have to discuss evolution and origins of life and i think this is fruitless in connection with a movie meant to entertain.

A sandgrain (SiO2 silt) of 0.1mg (10^⁻7kg) hit at 0.8c (240,000,000m/s) (where relativity doesn't count that much yet) has a kinetic energy of 0.0000005 * 240,000,000² = 28800000000J or 28.8GJ (maybe someone check this). That is roughly 7 metric tons of TNT exploding on impact on the hull. We know what a few tens of grams of explosive do to an airliner hull. Yes, a star trek reflector shield and correctly calibrated dilicium crystals would solve the problem :-) Also, as you reach c, you literally run out of space (which is compressed in direction of travel) and time. You cannot look forward because there is no "in front of", and there is no reaction time. The dust particle on the other side literally has all the time of the universe. Until ~0.8c you might be fine with the classic "view of things", though no known energy source could accelerate a massive object like a ship to that speed. "Breakthrough Star Shot" is far from 0.8c yet their proposed laser parks are just dreams as are their "ships" of a few gram. EM-fields: does dust fly from a transmitting antenna ? Ok, alien ships explode if exposed to loud music :-) Search: kinetic energy, electromagnetism, this forum (!), general relativity, relativistic mass, time dilation. Many of your questions can be answered when browsing through physics forums ...

Where to begin discussing whether life is a movie, the universe pre-programmed and time a spreadsheet macro ? Edit: forget it ... if a mod feels urged to delete/edit this post then no problem, go ahead ... i am clueless.

I am already the one-eyed among the blind :-) If i want more i'd have to pay for a course. The book i mentioned (Inside PixInsight) is actually very good. It is absolutely feasible for a half-educated newcomer like me and explains processes and steps with the software very well. So, if people are willing to invest a little something in astroimage processing software this is the right way and it's, compared to Photoshop, inexpensive. Also, compared to the freeware Fitswork (which has a good reputation !), PixInsight is far more sophisticated. And (the reason why i will buy it as soon as the trial license has expired) it's available for Linux (also poorly programmed, needs root rights to install, but i have an installation for these unruly cases ;-)) and you can really download and install it and disconnect from the bloody internet while working ! Wow ! /sarcasm Yay ! Good weather, where are you ? :-)

Yeah. Thanks for the words. I had a few days in December and January, adjusting the equipment and one night for orion nebula. Yesterday for example i had a steel blue sky, but the wind was blowing too strong and gusty and it carried a spray over the ridge behind my place. PixInsight is indeed what i am trying to get into with the help of the book "Inside Pixinsight". Can recommend it. Btw. I remember the midnight dusk in june when i was on the baltic sea. Am at 28 north now; not that much difference in length of day night :-)

Relativity. For the outside observer your ship stands still as reaches the event horizon. For you in the ship time dilates so much that the universe will be gone in a blink. You.can.not.return. Apply the formula for time dilation. The moment just before v becomes c. Edit: well, "you" might leave it as part of the hypothetical hawking radiation over the course of the next fantastillion years.

This is getting ... difficult. You neglect basic physical principles. I quit.

Few things from my lay-understanding: The universe isn't perfect. It just is. And there are three spacial dimensions to freely move in locally back and forth. Time is not predefined, it is as relative as can be. It will show a different behaviour depending on relative speed and the presence of gravitational forces, but always one direction or it leaves our observation. We have already been through the "predefined" in the other thread. Question: do you accept Heisenberg's uncertainty relation ? If yes, then why do you insist ? If no, then there is no chance for us ... :-) I don't know if the concept of a primordial singularity is in unison with current cosmological models. I don't think so ... need more info :-) blabla :-)

I am not sure whether i understood it, but at least number 4.) makes a common mistake: it assumes that the universe exploded into something. That is not the case. As the universe expands it creates it's own space, not like new points in a fixed coordinate system but like a balloon that is being blown up, distances between existing points become greater. There is no "around" or "outside". Number 1.) is deprecated, as is 2.), 3.) was Einsteins favourite but Hubble's objection made the idea obsolete :-) Also i am missing the widely accepted concept of an ever-expanding universe that get's ever darker over time (!) without an end. Of course, views on this may change over time (!) as knowledge increases ... Again: Cosmologists (i mean real scientists :-)) have written books on the topic ... :-)

Well, science cannot and is not meant to compete with belief ... :-) Yep, that's why time has only one direction in the observable universe and wasn't that OP's question ? Highly theoretical models like string- or m-theory (which are far beyond my understanding) can in principle explain any sort of universe with any combination of laws and forces and whatever, but what is the relevance of such a theory ? Maybe i am a little too down-to-earth ... :-)

Second law of thermodynamics says: No. Edit: Puts on inquisitors hat, gets thumbscrews and iron maiden: "Are you questioning thermodynamics ?" :-)))

In that i differ, at least concerning complex life (multicellular, food chain, biocenosis, this sort of things). Probabilities need a data base and we only have one single sample. Also they need constraints to work with and we (at least i ... :-)) don't know about any constraints on distant planets except estimated temperature. And we call that "habitable zone". We see in our system how deceiving that can be: Venus is on the inner edge of the "habitable zone". Were it near Trappist or Proxima C. it would be crowded with aliens . But in reality it is not really known as a cozy place. But, really, i don't know.

One day soon(tm) ... In the same forum someone was ranting exactly over that learning curve and expressed his thoughts about vts with less reserve than i did :-) He said that he tried several hours and didn't even get behind a certain process in the workflow. Then he got an answer from someone who claimed to do astroimaging since years and just scrapped the work of 160 (sic!) hours on a single image just to start all over again. Conclusion: keep smiling , things could be worse .

Image processing is driving me nuts. Nobody writes a documentation any more these days. You need to watch video tutorials (vt). But they are like tv cooking shows with prepared prerequisites: they work. As soon as as you cook your own soup i mean use your own data nothing works as it did in the vt. Did they mention you had to check the "Lightness mask" box before applying the changes globally ? Or that you need linear data for the process to work correctly ? Or need the "StarAlign" process instead of "ChannelMatch" to match shifted colours in an rgb combination ? Or select three different previews to check the settings ? Frustrated after several days i visited a forum where the high and mighty discuss, managed to register after answering 20 silly question 4 times to get through the anti spam wall, browsed through all the spam to look if anyone else had the problem before, found nothing, posted my question and get a wavy answer like "did you check the "Lightness mask" box ?". *sigh* "Thanks for the reply, but, yes, i did ... ?" Vts are just a waste of time and bandwidth. I just read that someone has written a book about astro imaging software. I hope i find the answers that i am looking for there. /rant

Well, i never follow the link, so i don't know the content ...