38

The universe is expanding on a large scale. But locally things are always messy. Locally, galaxies are not set in stone, they move relative to each other, and the directions are random. If they're moving towards each other fast enough, then they will collide. Also, there's gravity. Some galaxies are bound to each other by gravity, and that will tend to ...


37

I think that your thought process is flawed in that you assume that by drastically increasing the temperature you are guaranteed to get heavy elements. As odd as this may sound, this isn't the case (especially during the Big Bang Nucleosynthesis (BBN)) for a few reasons. In fact, if you took a hydrogen-only star and made it go supernova, you wouldn't get ...


36

I think your question is on topic, but @RhysW has linked a very helpful post in understanding why your question is a common misconception about the Big Bang. No Center There is no 'center' to the universe. At any point, a local observer will claim that they are at the center of the universe by the way galaxies move away from them. How can we possibly know ...


20

You're envisioning the Big Bang as a cosmological "explosion" in space where the universe is the resulting material expanding in outward all directions. The problem is, the universe doesn't work like that. The universe isn't a region of space that is expanding outward into another thing where you can (even hypothetically) fly out to the border and say, "...


20

Your problem essentially arises from trying to apply Schwarzchild black hole logic, the assumptions of which are pretty much maximally violated at the big bang. The following were true at the big bang, and violate the usual black hole formation logic. The event occurred everywhere in space, not actually a point. In particular, the energy was uniformly ...


19

Yes, here. As has already been mentioned, the big bang happened everywhere due to the fact that all of time and space was in the same spot at the point of the Big Bang. And so the big bang happened here, there and everywhere. This is also similar to saying that the universe has no centre. I have seen this phenomenon explained using two pieces of clear ...


18

Your are misunderstanding the expansion of the Universe. The Big-Bang is not an explosion: this is the moment in time when the Universe had an (near) infinite density. So there is no center in the Universe as there is no center of the SURFACE of the earth (this is the most popular 2-dimensional analog). Since this primordial ultra-high density state, the ...


17

Currently, there's no single explanation for this. The simplest explanation is that there isn't any imbalance — there are large antimatter bodies in the universe; just separated from us. However, these would have to be pretty far away (otherwise the boundary annihilation would be detectable). Theoretically, this requires antimatter to have clumped ...


12

In one sense any point you choose is at "the centre" of the universe and at any point in the universe, at a large scale, the universe looks the same as at any other point. This is not the same as saying the universe is infinite, though (but it could be). The analogy with an explosion is a poor one, as explosions expand into existing space. With the Big Bang ...


11

No. The furthest we can see is the cosmic microwave background radiation (CMB). Early on (after the big bang), matter was fully ionised and the electrons frequently interacted with the photons. That has two consequences. First, the radition was that of a blackbody at the same temperature as the matter. Second, the universe was opaque, i.e. photons couldn't ...


10

What I mean is, even if it is capable of expanding, if everything originated at the big bang how can that space turn to be infinite in a finite time - the age of the universe. In the standard ΛCDM model of the Big Bang, the universe is infinite and has always been such. The Big Bang singularity happened everywhere, in the sense that far back enough in time, ...


10

Okay, I think I know what Max Tegmark is talking about in the video. He is referring to the fact that, when you observe the cosmic microwave background radiation (CMB) — i.e. the radiation that was "released" when the Universe had expanded and cooled sufficiently to allow protons and electron to combine into neutral hydrogen without immediately being ionized ...


10

By observing the observable universe we can gather a lot of data about the constituents of the universe now and in previous epochs, right back to the cosmic microwave background. This data places quite narrow constraints on viable models of the Big Bang. This is why cosmologists are confident about the details of the Big Bang, certainly from electroweak ...


9

I think the source of confusion between the two concepts - the Big Bang singularity and an infinite universe - is the misconception that the universe began as a finite expanse originally. This misconception easily arises from analogies using present-day logic and numbers that were not applicable in the early universe. For example, I've heard it said that ...


9

In the standard models of the Big Bang, there is no such thing as the "edge of the expansion front". The universe, as far as we can see and as far as standard cosmology assumes, is homogeneous and isotropic on the large scale, so there is no edge or anything analogous to an the shock front of an explosion. According to the seven-year WMAP results [pdf], the ...


9

A black hole is a region of spacetime separated by an event horizon, which means no signals from the interior can propagate outward, no matter how long one waits. Locally, there is nothing special about the event horizon; if you fall in a black hole, there is nothing marking that you've crossed and no local experiment (short in space and duration) that will ...


9

The Big-Bang was not an explosion in empty space. Inter-galactic space is not empty, there is an inter-galactic medium, gas clouds and material ejected from galaxies, including stars and possibly globular clusters, by various mechanisms...


9

No. There is no consensus. The discrepancy between the predicted big bang nucleosynthetic abundance of Lithium 7 and the measured value can be summarised as follows. If we take what we know about the the baryonic mass density of the universe and the Hubble constant, we get a self-consistent picture between the cosmic microwave background, observations of ...


9

The temperature of a gas is a measure of the kinetic energy of the particles. For molecules you can have rotational and vibrational energy, while for single atoms you just have translational energy, or "thermal motion". At a given temperature, the particles don't have exactly the same energy, but a distribution of energies, and hence velocities. Most (>90%) ...


9

The galaxies don't really get "off track" - it's not impossible, but that kind of thing probably doesn't happen anymore (as space continues to expand). What actually happens is that galaxies form gravitationally bound clusters - within the cluster, the acceleration due to gravity is larger than the equivalent expansion of space between the galaxies, so ...


9

I'm not sure that anyone has answered the question asked. The root cause is indeed that gravitationally bound structures with freefall timescales that are much shorter than the age of the universe are not greatly affected by the general expansion of the universe (NB: Structures with freefall timescales longer than this are not going to be the source of many ...


9

There are several processes at work: Fission (of unstable elements) increases the number of atoms. Fusion (occurs in stars and supernovae) decreases the number of atoms. you could claim the formation of neutron stars decreases the number of atoms: it reduces atoms to just neutrons you could claim the formation of black holes decreases the number of atoms: ...


8

It's all around us. The way I explain it is that we are in the centre of the universe (I don't mean in the geocentric way as thought back in the middle ages where all is moving around us). Everywhere we look we see the past: our Sun how it was 8 minutes ago; the closer star, Alpha Centauri, as it was 4.2 years ago, the Andromeda galaxy's light took 2.5 ...


8

Those galaxies were 10 billion light years away from Earth. So light would take much more time to reach here and that light which is now 10 billion years older can be seen now. Even light from the Sun takes 8 minutes to reach to us. So if somehow sun disappears suddenly(very unlikely) we wouldn't know for 8 minutes.


8

You assumption is wrong. Universe can( and is ) expand faster than the speed of light. The photon emitted towards our planet in the early universe, had to traverse a universe that is expanding. That photon experienced redshift, that means his wavelenght increased and frequency decreased. We measure that photon's wavelength, compare it to a photon that was ...


8

You are making the mistake of thinking that there was a single spot in space that everything expanded from. Rather, the expansion was not of things in space, it was space that expanded. It was an expansion OF space, not IN space. There wasn't "space" around the singularity.


7

Quick answer: Because they didn't entered our event horizon. Some never will. And some will move out of our event horizon - their last photons that'll be received here being sent right now. Let's do some fact checks first: [...]the galaxies that are now at the 'edge' (not visible theoretically) must have been (at some point in time) at place around ...


7

Gravitational waves from the big bang may be "heard" but not by LIGO. The waves emitted at or around the inflationary epoch of the big bang are expected to be at much lower frequencies (milli-Hz or lower) than those announced today by LIGO. There are various sources of noise that make LIGO insensitive to GWs at frequencies below about 10 Hz. It will take ...


7

The expansion of space is something that happens on the largest scales. At small scales, such as distances between nearby galaxies, other forces, such as gravity, dominate. Galaxy clusters are held together by the attractive force of gravity between these galaxies. Space in these regions is still expanding, but the gravity pulls on these galaxies much ...


7

Hydrogen was not "created at the moment of the big bang". Particles (leptons and quarks) can attain mass via the Higgs field after the epoch of electroweak symmetry breaking, that occurred about a picosecond $(10^{-12}$s) after the big bang. Only after this was it possible to form the building blocks of hydrogen. In fact the formation of stable protons ...


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