Question(s): I have three related questions:
- The redshift of objects indicates that the farther away they are, the faster they’re moving, but wasn’t the observed light emitted millions of years ago, when the object wasn’t so far away? How do we know what velocity it’s moving at now, or if it’s even there? Have we measured the velocities of known objects over ‘long’ periods of time to see if their velocities are changing, either speeding up or slowing down?
- Rather than a ‘big bang’ with the Universe being created and expanding into nothing, isn’t it possible that it was a ‘big bubble’ similar to nucleate boiling, and that we are surrounded by ‘stuff’ into which we’re expanding?
- If we are expanding into stuff, couldn’t the cosmic background radiation be coming at us from outside the boundaries of our Universe? Could ‘dark’ energy and matter be external also? — Larry
- You are correct in that the light emitted from distant objects that we observe today was emitted from the distant object in the past, its speed in getting to us limited by the speed of light. We do not have a way to measure an object’s velocity “now”, but we can measure the velocities of objects at a range of distances from us. This allows us to sample the expansion rate of the universe at a range of distances, and therefore measure the speed-up or slow-down of the universe’s expansion.
- The suggestion that the universe is expanding into other “stuff”, like any alternate theory of the expansion of the universe, requires a way to test its observables. This is the problem with most alternate theories. How would you measure the “stuff” into which our universe is expanding? I don’t believe that it is possible to measure the material into which we might be expanding, so this alternate theory really is not viable.
- I am not aware of any observations which would allow for the cosmic microwave background and dark energy to be derived from an external body of matter. At this point, this would be a theory which lacks observations to support it.
Question: Hi, my name is Kemp and I just finished watching a program from the Discovery Channel entitled “Understanding the Universe”. The program triggered an odd question, do blackholes create dark energy and/or dark matter relative to their size? — Kemp
Answer: No. The only connection between black holes and dark energy is the “darkness” of their names. Black holes are sources of intense gravity from which even light cannot escape. Dark energy is the theoretical entity that accounts for the majority of the energy content of the universe and is responsible for the overall acceleration of the expansion of the universe.
Question #1: Hello there! Sorry for the previous thing I had sent, it was merely a comment. I am a 16 year old high school student who is interested in the study of the stars and our universe itself. And I also have a theory to which, I would highly appreciate if you took the time to read it. You know the candle light variable used to measure the distance of us from a certain star? With that being said, there is also the situation of our universe expanding farther away, and the theory of how it will stop and come back to it’s center of where it began, which is where the Big Bang theory comes from. Now, I know this sounds a bit crazy. But hear me out. Since our entire universe is made up of dark matter, also a compound in the creation of our universe with the gas and dust that creates stars, the universe coming back together, crunching into one could cause another Big Bang. In which case, would be the same illusion as a star pulsating it’s light. What if we are only specs of particles and molecules created to make one big star? What if our whole universe if just one star as we know it, and there are billions upon billions of stars, that make up universes? — Rachel
Answer #1: All theories, whether they be to explain the evolution of the universe or the properties of a star, require measurements to support them. What measurements support your theory? This is the key to any scientific investigation that involves theory which must ultimately be supported by observations.
Question #2: Also, I’d like to mention that I have an idea for a device that could be placed a certain distance away from Earth, enough not to mess with the gravitational pull, and take the near earth objects that could be potentially dangerous by coming to close and crashing in Earth. What if they made a device to take these potentially dangerous items and drag them away from Earths surface, and had a inside that could destroy the items inside? This device could also be used for meteorites, to pull them away from the Earth’s gravitational pull. Also, with delittering the area, you could catch more light in telescopes and would be allowed to possibly see things even farther than we ever have. Please message me back, telling me what you think!
Answer #2: How would this device collect meteoroids and potentially dangerous asteroids? Note that the sheer number of meteoroids and asteroids that this device would need to collect would make any “scooping” device not practical.
Question: My understanding is that the COBE experiments back in the late 80s/early 90s were successful in detecting what we generally believe to be the CMB leftover from the big bang.
In reading about the experiment I haven’t had much luck finding an answer about if COBE (or some other experiment) has been able to estimate a vector, or general location, for the big bang itself. Do we have any data that allows us to extrapolate where, geographically in the universe, the big bang might have been? Would this be a safe/fair location to consider the “center of the universe” if it were known? — Tim
Answer: In fact, there is no “center” to the Big Bang. The Big Bang was not an explosion which radiated from a point but rather an expansion of all points from all other points in the Universe. One of the best pictorial descriptions of this fact can be found on Ed Wright’s Big Bang “nocenter” page. This is part of the “cosmological principle, which states that all positions in the universe are equivalent, and that the universe is homogeneous.
Question: There is a lot of acceptance that when the gases of the universe began to join and spin because of the impact of those collisions. That would mean that all particles hit in the same direction, like using your hand to spin a basketball on your finger. When one questions this I just get blank stares as if I’m suggesting some sort of heresy. But, apart from the difficulty I have with the Big Bang being possible on it’s own (Quantum Physics suggests you need an outside force) the answers I read about the formation of planets and gravity seems absurd yet I can’t find anyone to explain it without theory and conjecture. Can someone help me. Just to make it clear what I’m asking, please help me understand how gas particles flying in every possible direction as can form into a rotating ball that turns into rock because physics itself suggests that is impossible. I use the theory that is used for the formation of planets as….
“…there was a massive cloud of hydrogen gas left over from the Big Bang. Some event, like a nearby supernova explosion triggered a gravitational collapse of the cloud, causing the hydrogen atoms to attach to one another through mutual gravity. Each individual hydrogen atom had its own momentum, and so when the atoms collected together into larger and larger clumps of gas, the conservation of momentum across all the particles set these clumps of gas spinning.”
Now that is a lot of conjecture – considering collisions from every possible direction…let alone how those hydrogen gas particles, once collected together formed everything we have on and in the planet.
Answer: I think that the slight misunderstanding in your logic is the equate “sticking” with the gravitational attraction between particles such as atoms, molecules, and dust particles, which ultimately results in the formation of more massive objects like asteroids, comets, planets, and stars. It is not necessary for objects to collide and “stick” to each other immediately. A stable cloud of massive particles that is affected by a nearby event that “pushes” on it, such as a nearby supernova, will potentially be pushed in such a way that gravity causes objects to slowly move closer to each other and ultimately coalesce. This slow collapse of massive objects toward other massive objects ultimately builds on itself, collecting larger and larger massive objects. This ultimately is a mechanism for forming objects like planets, stars, and galaxies.
Question: Do dimensions really exists? [Also,] are the black holes really or possibly portals leading to different dimensions (like a whole new universe or a totally different universe)? [Also,] right now I read in the blog about like the diameter of universe being 96 billion light years (in other sense the universe being confined within these 96 billion light years diameter) so what lies beyond that diameter? — Pravesh
Answer: One can speculate or theorize as to what exists beyond that which we can measure, but that is, strictly speaking, not science. What scientists do is make observations of the universe and apply the laws of physics to those observations to interpret what they observe. As there are no actual observations which can tell us what lies beyond a black hole or the edge of the universe, we can only speculate or theorize as to what might lie beyond what we observe. To my knowledge there are no theoretical predictions which are based on physics which predict what lies beyond black holes or the edge of the universe, which leaves us only speculation, which is not science. So, a scientist would answer that there is no information to tell us what lies beyond a black hole or the edge of the universe.
Question: Can a black hole become unstable and cause a “small bang”? Creating parallel universes? — Raoule
Answer: I don’t believe that there are any reliable theoretical calculations that produce this series of events. In fact, I don’t believe that “unstable” black holes lead to explosions of any kind.
Question: I have read that the diameter of the universe is 96 billion light years. How can that be if the universe is a mere 14 billion years old? Am I to conclude that the 96 billion figure is some extrapolation based on rapid inflation? — Carlton
Answer: One of my physicist colleagues, Frank Heile from Stanford University, has provided an excellent answer to this question. First of all, the 13.8 billion light years is derived from the radius of a sphere of the Cosmic Microwave Background (CMB) radiation that is being observed by the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck satellites. These satellites have mapped the structures which are precursors to galaxies and clusters of galaxies. Now, the radiation from the CMB measured by the WMAP and Planck satellites has, in the meantime, continued to expand so that the structures measured in the CMB signal would be 46.5 billion light years from us at this time. Second, the 93 billion light year diameter estimate refers to the “observable” universe.
Now, if we waited another 46.5 – 13.8 = 32.7 billion years, we should actually be able to see the light emitted right now from those superclusters of galaxies which formed from the CMB structures. The light is already on its way towards us but it will take a while to reach us since it will have to come from a sphere with a diameter of 93 billion light years. This is the explanation for the difference; the “observable” universe is larger than we can see it today.
This is only, at best, a theoretical estimate of the diameter of the universe, though. We now know that due to dark energy the expansion of the universe is accelerating. This acceleration will not allow us to see those superclusters which are now 46.5 billion light years from us. In fact, if we wait the requisite 32.7 billion years those superclusters will be receding from us at a rate that is greater than the speed of light. We just will not be able to observe those galaxies and clusters of galaxies which have formed at the edge of the universe.
Question: What does the structure of the universe look like at the largest scales?
- Galaxy cluster are distributed evenly throughout space with no large gaps
- There are many more galaxies and clusters in some directions (up and down the milky way’s disk) and very few galaxies in other direction
- Linear or wall like distributions of galaxies, clusters, and superclusters surrounding relatively empty regions- like soap bubbles
- Galaxies and cluster are very thiny spread out in the near distance, and are more closely packed at greater distances from the milky way
Answer: I think that option 3 comes closest to the actual distribution of galaxies in the universe. The large-scale structure of the Universe is made up of filaments and voids. When we look closely at the filaments, we find that they can be broken down into superclusters, clusters, galaxy groups, and finally into galaxies.
Question: Is it possible that the big bang occurred in a pre-existing universe? if not, how do we know? — Gary
Answer: I think that the best evidence to support the fact that the Big Bang happened in this universe is the fact that we see evidence for its existence in our universe. There really isn’t any reason to invoke the existence of another universe to explain the Big Bang.