size of the universe at the big bang

How Big Was The Universe At The Moment Of Its Creation?

Mar 24, 2017 · The diameter of the Milky Way is 100,000 light years; the observable Universe had this as its radius when it was approximately 3 years old. When the Universe was one year old, it was much hotter and denser than it is now. The mean temperature of the Universe was more than 2 million Kelvin.

Author: Ethan Siegel

Our Expanding Universe: Age, History & Other Facts

During the first three minutes of the universe, the light elements were born during a process known as Big Bang nucleosynthesis. Temperatures cooled from 100 nonillion (1032) Kelvin to 1 billion (109) Kelvin, and protons and neutrons collided to make deuterium, an isotope of hydrogen.

What was the size of the universe at the time of the big bang?

No conclusion can be made about the size of our Universe based on the fact of the Big Bang.

How big was the Universe at the moment of its creation?

But if we’re talking about the observable Universe, and we know we’re only able to access somewhere between the last 10^–30 and 10^–35 seconds of inflation before the Big Bang happens

Size Of Universe At Big Bang | Sciforums

Jan 30, 2009 · We can now solve for the thickness of our universe at big bang. The total radius of the universe will be: The thickness of our universe is: The universe at big bang is a layer 74 miles thick upon a radius of 284 miles from the common center.

Initial Size of Big Bang | Physics Forums

Mar 29, 2011 · A somewhat different question is the initial size of the *observable* universe. The current radius of the observable universe (i.e., the region of space from which light has had time to reach us since the Big Bang) is about 46 billion light years.

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cosmology – Size of universe after inflation? – Physics

5 Answers. That happened 379,000 years after the big bang at a redshift of 1098 which means the universe was about 84.6 million light years in diameter which, per WolframAlpha, is about half the diameter of the local super cluster of galaxies or about 840 times the diameter of our galaxy.

With the proper definition of the “size” of the universe, this question does make sense. The standard model of cosmology would say that the universe is infinite which therefore does not have a “size”. However, if we take into account that the big bang occurred $13.7 \pm 0.17$ billion years ago we can define a meaningful size for the observable universe. You might, for example, define the size of the observable universe as the distance a photon could have traveled since the big bang. Consider, for example, a cosmic microwave background (CMB) photon that was emitted as visible light about 379,000 years after the big bang and is just now hitting our microwave detectors (the redshift is z=1089): that photon has been traveling for 13.7 billion years so it has traveled a distance of 13.7 billion light years. So you might imagine that the current radius of the observable universe is 13.7 billion light years. However, during this time the universe has been expanding, so the current position of the matter that emitted that photon will now be 46.5 billion light years away. (By now, the little $10^{-5}$ bumps on the CMB will have condensed into galaxies and stars at that distance.) This gives a diameter of the current observable universe of 93 billion light years . Note that as time passes, the size of the observable universe will increase. In fact it will increase by significantly more than two (to convert radius to diameter) light years per year because of the continued (accelerating) expansion of the universe. Also note that we will not be able to use photons (light) to explore the universe earlier than 379,000 years after the big bang since the universe was opaque to photons at that time. However, in the future we could conceivably use neutrinos or gravitational wave telescopes to explore the earlier universe. So given a size of the current observable universe, we can ask how big was that volume at any particular time in the past. According to this paper at the end of inflation the universe’s scale factor was about $10^{-30}$ smaller than it is today, so that would give a diameter for the currently observable universe at the end of inflation of 0.88 millimeters which is approximately the size of a grain of sand (See calculation at WolframAlpha ). It is believed that inflation needed to expand the universe by at least a factor of 60 e-foldings (which is a factor of $e^{60}$). So using WolframAlpha again we find that the diameter of the universe before inflation would have been $7.7 \times 10^{-30}$ meters which is only about 480,000 Planck lengths . Perhaps Brian Greene was talking about the size of the observable universe at the time when the CMB photons started traveling towards us. That happened 379,000 years after the big bang at a redshift of 1098 which means the universe was about 84.6 million light years in diameter which, per WolframAlpha , is about half the diameter of the local super cluster of galaxies or about 840 times the diameter of our galaxy.24In the simplest model of the universe, the FLRW metric, the universe is infinite and has always been infinite right back to the Big Bang. Inflation doesn’t change this assumption. So it makes sense to ask, for example, how big a Planck volume became during inflation, but it doesn’t make sense to ask how big the whole universe is. (Depending on what you take as the inflation scale factor a Planck volume ended up about $10^{-27}m^3$ and this is a lot smaller than a basketball.) Having said this, Don Page has suggested a lower bound for the size of the whole universe at the end of inflation, and his answer is $10^{10^{10^{122}}}$ cubic megaparsecs. However I think you should regard this as extremely speculative.2Of the order 10 meter. The size of the Universe can be calculated by integrating the Friedman equation , which is a function of the densities of the components of the Universe (radiation, matter, dark energy, curvature, as well as more exotic components), as well as their equations of state. In general, there is no analytical result, but in certain epochs the history of the Universe, its dynamics are completely dominated by one or two of these components. The early Universe was dominated by relativistic matter, i.e. radiation and neutrinos (early matter was also relativistic, but didn’t contribute significantly to the energy density). In this case, integration yields the following relation between the scale factor $a$ (i.e. ratio between lengths at that time and today) and time $t$:
$$
a(t) \simeq \left( 2 \sqrt{\Omega_\mathrm{r,0}} H_0 t \right)^{1/2},
$$
where $\Omega_\mathrm{r,0}$ is today’s value of the energy density of radiation relative to the critical density, and $H_0$ is the Hubble constant. For a Planck Collaboration et al. (2016) cosmology, at $t\sim10^{-32}\,\mathrm{s}$, this yields $2\times10^{-26}$. That is, if inflation ended after $10^{-32}\,\mathrm{s}$, everything was $5\times10^{25}$ times closer to each other, or roughyl 60 e-folding$^\dagger$. The total Universe may or may not be infinite, but what we usually refer to when talking about the Universe, is the observable Universe , which is the part of the Universe from which light has had the time to reach us since Big Bang. The Universe is 13.8 Gyr old, but because it has expanded in the meantime, the observable Universe is more than 13.8 Glyr in radius — in fact $R_0 = 46.3\,\mathrm{Glyr}$. Hence, the radius of what comprises “our” Universe today , was at time $t$ only $R(t) = a(t) R_0$, so at the end of inflation
$$
\begin{array}{rcl}
r(10^{-32}\,\mathrm{s}) & = & a(10^{-32}\,\mathrm{s}) \, R_0 \\
& = & 2\times10^{-26} \, \times \, 46.3\,\mathrm{Glyr} \\
& = & 9\,\mathrm{m}.
\end{array}
$$ If you think that inflation ended already after $10^{-33}\,\mathrm{s}$, you’ll get $r=3\,\mathrm{m}$ instead. $^\dagger$ Coincidentally (I think) roughly the same number of e-foldings as inflation itself.2
I’m just a lowly aerospace engineer. But when I think of inflation to a certain volume, my Euclidean me says that it had to be at least large enough at the end of inflation for the 13.7 billion light year distance from our present position to the opposite end of universe since that is the farthest light we have detected. If this is the case can’t we just back calculate to the radius given the accelerated expansion (assuming constant acceleration rate) since the end of inflation? In my thinking if the universe was millimeters in size at the end of expansion, then the photons emitted from the “other side” of the universe would have passed us already. So even with an accelerating expansion from that time to today at velocities much less than the speed of light means that we cannot possibly be seeing the start of the universe after cooling.Answer to the inflation riddle is simple, it is staring everyone in the face. You can not explain the early universe in classical terms, the size/volume whatever you want to think of before and after the inflationary period is irrelevant.
The before and after were completely different to each other, why? Because in the beginning there was nothing, then there was something, this something did not come fully formed as we see the universe now with it’s multiple dimensions, at that beginning point there was only one dimension, what happen after in the inflationary period was the expanding or addition of the extra dimensions, two then three, and so on, that is why the expansion seems so incomprehensibly large and seems to move at impossible speeds far beyond what the speed of light would allow. The number of dimensions is infinite on a scale of infinities beyond reasonable comprehension, of which the observable universe is only three and was fully formed at the end of the inflationary period, these infinite dimensions never stop growing exponentially. BUT Time it’s self is the first dimension, a framework of sorts, in which all the other dimensions rest, it is the container, not a point, like the exponentially dividing cell when human life begins. Time is nothing more than exponential dimension addition/growth.

How large was the universe at the moment of recombination

The “average density at the time” — assuming a constant Universe energy of ≈ 8.7×10^52 kg — comes out to ≈ 4.5×10^–13 kg m^–3 (≈ 2.7×10^14 particles (“hydrogen atoms”) per cubic meter). The blue line shows the impact of “inflation,” using Alan Guth’s suggested

What Was Our Universe Like Before the Big Bang?

A Hibernating Universe. Maybe before the Big Bang, the universe was a small, slowly evolving fixed space, as theorized by physicists like Kurt Hinterbichler, Austin Joyce and Justin Khoury and

The Big Bang: What Really Happened at Our Universe’s Birth?

Big Bang theory holds that our universe began 13.7 billion years ago, in a massive expansion that blew space up like a balloon. It doubled in size perhaps 100 times or more, all within the

Universe – Wikipedia

Comparison of the contents of the Universe today to 380,000 years after the Big Bang as measured with 5 year WMAP data (from 2008). (Due to rounding errors, the sum of these numbers is not 100%). This reflects the 2008 limits of WMAP’s ability to define dark matter and dark energy.

Diameter: Unknown. Diameter of the observable universe: 8.8×10²⁶ m (28.5 Gpc or 93 Gly)

The Temperature of the Universe During the Big Bang

The big bang theory of the origin of the universe is a logical result of the discovery by astronomer Edwin Hubble that the universe is expanding. If the expansion could be reversed, the entire universe would, at some point in time, contract into a single point in space.

Big Bang – Wikipedia

The Big Bang was “small”: It is misleading to visualize the Big Bang by comparing its size to everyday objects. When the size of the universe at Big Bang is described, it refers to the size of the observable universe, and not the entire universe.

Overview ·

What was the size of the universe 380,000 years after the

What was the size of the universe one second after the Big Bang? Was our universe still a black hole 380,000 years after the Big Bang? How big was the universe in the first few moments after the Big Bang?

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