14 ms·
Shouldn't distant objects appear magnified?
- PokedBear 3y agoThis is kind of mind blowing to me. The linked xkcd is a fantastic (if exaggerated?) illustration of this effect. Objects in mirror may be further then they appear.
- Etrnl_President 3y agohttps://xkcd.com/2622 https://xkcd.com/2622 Turn up brightness, and zoom in…
- soligern 3y agoWhat am I looking for?
- miquong 3y agoThe dimmest phones are larger than any others
- accrual 3y agoThe included explanation is mind boggling to me: > Things that are far away look smaller, but things that are REALLY far away look bigger, because when their light was emitted, the universe was small and they were close to us.
- baq 3y agospoiler alert: The oldest phone doesn't fit the comic strip...
- usrusr 3y agoClearly because Munroe hasn't adjusted for screen size inflation. If we extrapolate based on whatever Samsung or Apple are selling these days and the 8210, will we even see meaningful redshift before the Planck constant chimes in?
- xnx 3y agoThis would be a fantastic little toy/demo in VR.
- SquareWheel 3y agoLarger version for others who are visually challenged. https://imgs.xkcd.com/comics/angular_diameter_turnaround_2x.png https://imgs.xkcd.com/comics/angular_diameter_turnaround_2x....
- kortex 3y agoI love that the battery depletes slowly over time. Though it's a bit ominous that the most recent one shows battery in the red...
- deleted 3y ago[deleted]
- psychphysic 3y agoLove this, there are a few topics you hear about in class and you don't realise how mind boggling they are until someone less says hold up... The interpretation of the Poynting vector is another.
- ww520 3y agoAnd based on the size of the magnification of the galaxies throughout time, we can tell whether the universe is expanding at a constant rate or accelerated or decelerated at certain point.
- xen0 3y agoIs it reasonable to view the Cosmic Microwave Background Radiation as being the limit of this? The remains of the big bang, maximally scaled up and red shifted as far as things can be today?
- drorco 3y agoSo essentially one giant blob of cosmic background radiation was at the time its light was emitted, the size of an atom or so?
- ben_w 3y agoKinda but different scale, the CMB era universe was about 1100 times smaller than that now, so still huge. There may be a neutrino background behind the CMB, where the universe was even smaller, and the gravitational wave background behind that with even more of a size difference.
- bozhark 3y agoPlays right into the white hole theory, interesting
- bloopernova 3y agoAs in a white hole is the big bang? That has a kind of poetic symmetry to it, with black holes (big crunches?) being the end, and white holes being the beginning of our particular universe. But our universe has black holes in it. Forgive the layman thinking, but does that mean we're just one of an infinite series of "nested" universes?
- pelorat 3y agoThe energy in our universe is not unlimited, so perhaps each black hole spawns a new universe, and each has less and less energy in it. Think about, WHY is there a certain amount of energy in the universe? Why not more or less. Maybe it's just universes all the way down.
- dav_Oz 3y agoThis educational paper [0] titled "Expanding Confusion" (2003) is a classic on the general topic and well worth the read. Holding the two concepts of an accelerated (!) (in terms of objects [1]) expanding universe and the fixed finite speed of light simultaneously in one's Euclidean head can be dizzying, so be prepare to draw and enjoy the hard earned manual labor of counterintuitive conclusions. [0]https://arxiv.org/pdf/astro-ph/0310808.pdf https://arxiv.org/pdf/astro-ph/0310808.pdf [1]https://bigthink.com/starts-with-a-bang/universe-expansion-not-accelerating/ https://bigthink.com/starts-with-a-bang/universe-expansion-n...
- dmbche 3y agoMakes me think of this : https://en.m.wikipedia.org/wiki/Terrell_rotation https://en.m.wikipedia.org/wiki/Terrell_rotation How when going at relativistic speeds, you start to appear to rotate to obervers even if you are going straight - you can even see behind the object!
- brabel 3y agoThat's amazing. I've watched lots of videos about length contraction and I don't think any of them ever mentioned this (the shape of an object moving a near light speed won't change to an observer, it will just appear as if it had rotated instead of being "squeezed" as every video about this seems to imply)!
- rand0mx1 3y agoThis video might change your perceptive. https://youtu.be/watch?v=uTyAI1LbdgA https://youtu.be/watch?v=uTyAI1LbdgA
- MayeulC 3y agoYou rather showed the opposite. While interesting, this video only explains length contraction, not the Terrell–Penrose effect. In this video, the passing spaceship would appear to be rotated to the observer, not just contracted, as, to quote Penrose via Wikipedia, the light from the trailing part reaches the observer from behind the [spaceship], which it can do since the [spaceship] is continuously moving out of its way"
- ricksunny 3y agoThis nascent series on YouTube , Hypercubist Math, sets out to make four dimensions intuitive to our three-dimensions-accustomed brains. Baseline is just basic calculus, which the inaugural video provides in context: https://youtu.be/XfWgfZ5V2qI https://youtu.be/XfWgfZ5V2qI
- someplaceguy 3y ago
- thayne 3y agoHuh. That would make such objects even harder to detect, since the light is spread out over a larger area, so the amount of light hitting each pixel of the detector is less than if it wasn't magnified. On the other hand, it means you can see details you might not be able to otherwise.
- _dain_ 3y agoman that's fucked up. i dont want to look at the sky anymore.
- sulam 3y agoIs there an xkcd for _everything_?!?
- oneshtein 3y ago> xkcd for _everything_ https://xkcd.com/968/ https://xkcd.com/968/
- dentemple 3y agoBetter question: If there's no XKCD of it, does it really exist?
- FreshStart 3y agoLet us make a xkcd diagonal setup? https://en.m.wikipedia.org/wiki/Cantor%27s_diagonal_argument https://en.m.wikipedia.org/wiki/Cantor%27s_diagonal_argument to proof that there are xkcds not yet drawn?
- waynecochran 3y agoFascinating. A related question: When we look at Andromeda, which has a diameter of 220,000 light years, we are looking at it slightly edge on. Shouldn't the stars on the back edge be in a relatively different place in the sky than the stars on the front edge since the galaxy has moved relative to us over that 220K light years?
- Filligree 3y agoYes. And, of course, they are.
- waynecochran 3y agoThey appear as if I am looking at the front and back edge at the same point in time -- i.e. not 220K years apart.
- hughes 3y agoHow would you expect it to look that is different from its current appearance?
- tekla 3y ago/gif head exploding meme
- waynecochran 3y agoI would expect something kind of stretched out and warped like taffy. i.e. the front edge of the galaxy would be stretch out ahead of the back edge of the galaxy since the back edge is running behind time-wise.
- ahazred8ta 3y ago> stretched out ahead You have apparently not figured out (1) by how much? and (2) in which direction? - Andromeda rotates so slowly that after 220K years the far side has made only 1/1000th of a rotation. Please draw on a picture of Andromeda how far the far side moves after 1/1000th of a rotation. That's how small the image warping is.
- baq 3y ago[flagged]
- tomjakubowski 3y agoI've heard of "adjusting for inflation" but this is ridiculous!
- NHQ 3y ago"Give us one free miracle and we can explain anything!" - Terrance McKenna on modern science.
- cvoss 3y agoTake this a further step. Assuming we had telescopes big enough and sensors sensitive enough, what does the structure of the deepest parts of space look like? Are there pre-galaxy-formation structures which are smaller than galaxies and yet take up huge swaths of sky? Are there structures from some point in the past that take up so much space on the sky that not very many of them can "fit", and, if so, do the calculations work out so that an equivalent explanation for having not very many of them is that the [region of the] universe [which is observable to us] was just that much smaller back then?
- MaxikCZ 3y agoThe furthest we can see is the physical limit of universe: we can literaly see thefirst photons after universe became transparent. That is the CMB (cosmic microwave background, and you can easily google a real picture). The problem is, while these are the oldest photons we will ever be able to see, they still are from when universe was cca 400 000 years old, and by that time it was 100 million lightyears wide. That picture tells us that the universe was extremely homogenous (altho not perfectly), and basically no such structures you talk about. If we would like to see even further, we must give up on photons completely, and probably probe the ultra deep space gravitation waves. Those should give us picture even of completely opaque universe, as it was before then. So far we can only "see/hear" the brightest/loudest events in the universe with our gravitational waves observatories, but the fact we can even do that is astounding nontheless: we built a new sense for humanity, that no other known creature in the universe posses. LISA project should hear more.
- beltsazar 3y agoSpeaking of the expansion of the universe, in a very distant future when the expansion speed is so high that most of the galaxies won't be visible from earth, their astronomers will be thinking the whole universe contains only a few galaxies. But wait, what if the universe we observe today also misses some parts that can't be observed anymore? Neil deGrasse Tyson explained it more clearly: https://www.youtube.com/watch?t=436&v=TgA2y-Bgi3c https://www.youtube.com/watch?t=436&v=TgA2y-Bgi3c That's probably why it's called the observable universe.
- vl 3y agoThis XKCD strip would be genius if he used actual different historical cell phones - for awhile they were getting smaller, and then they started to get larger again! https://xkcd.com/2622/ https://xkcd.com/2622/
- _8j50 3y agoOne thing that always bothers me is time dilation when it comes to observing distant objects like this. If it takes 4 light years for the light to travel one way (and the one way speed of light still hasn't been measured!), that is for the observer at the origin, the photons we observe, for them it is much less than 4 years, is it even in years? So if I look at alpha centauri with a telescope, it isn't really aloha centauri 4 years ago that I am observing right? It's much more recent than that? Otherwise, if a 30yo person travels at the speed of light from alpha centauri to earth, when the person arrives will they be a 31yo(~) person who arrived 4 year later, effectively time traveling to the future? And if they return right away, will folks at alpha centauri meet a 32yo(~) person who came back 8 years later? If so, then maybe superman had the right idea about flying really fast around earth to travel in time, just not to the past. Perhaps some billionaire will decide to spin around the solar system really fast for a few decades and skip a century or so? Haha!
- brooksyd2 3y agoCaveat, I'm by no means an expert. A photon travelling between Alpha Centauri and Earth does not experience time it effectively arrives instantly. We as observers however will see that it took 4 years to make its journey. The idea of whether it's recent or not is irrelevant, it is all relative (to the photon it's recent, to us the light is 4 years old).