Articles

How far is the edge of the universe?


Asking how big the universe is seems like
a silly question. I mean- like- it’s big. Really big. How big, you might ask? Oh, I dunno, there’s probably a ‘your momma’
joke in there somewhere, but suffice it to say that it’s ginormous. But ginormous isn’t really a scientific
term- although it should be. So, seriously now, how big is the universe? Well the first thing you need realize is that
many people misunderstand exactly what that question is asking. We first need to distinguish between the entire
universe and the universe visible from Earth. Those are different things. So how much of the universe can we see from
our vantage point here on Earth? Well light has a finite speed, specifically
about 300,000 kilometers per second, or about 186,000 miles per second, which means that
when you see an astronomical object, you’re seeing it like it was in the past. For instance, it takes light from the Sun
eight minutes to get to the Earth. You probably knew that. But that has bigger implications. For instance, that means that there is a sphere
around the Earth with the radius of the Earth/Sun distance where light takes eight minutes to
travel to us. And that sphere idea is true in general. There is a sphere around the Earth with a
radius of a light year. If we could somehow send lots of super bright
lights a light year away to surround the Earth and briefly blinked them, what would happen
is that the light pulse would take a year to get to Earth and they’d arrive at the
same time. When we saw them, we’d be seeing a blink
that was a year old from objects located a lightyear away. We can take this idea to the extreme and ask
what is the oldest thing in the universe, and that is, by definition, the moment the
universe began. That happened 13.8 billion years ago. If the universe wasn’t expanding, the farthest
thing we could see would be a sphere, centered on the Earth, with a radius of 13.8 billion
light years. This is what we call the visible universe. Inside that sphere, light has had time to
get to us. Outside that sphere, it hasn’t. We can’t see anything outside that sphere. Now I should caution you and point out that
the numbers I quoted for the visible universe are true only if the universe isn’t expanding. Of course, it is expanding, so the situation
is a little more complicated. I made a video about how that changes things
and you might even want to take a look at it. But the bottom line is that there is a sphere
centered on the Earth that is the extent of the visible universe. Is that how big the entire universe is? The answer to that is almost certainly no. The universe is bigger than we can currently
see right now. And you already kind of knew that. For instance, as we look out and see the light
from the beginning of the universe today, we can see out to some distance. If we look again tomorrow, we will be able
to see out to that distance, plus an additional light day. That’s because light traveling over the
course of those 24 hours will just be getting to us tomorrow. And, inexorably, day after day, we will be
able to see a larger and larger sphere of the universe. There are locations that we cannot see today
because the light simply hasn’t had time to get to us, that we will be able to see
tomorrow. Again, this ignores the complications due
to the expansion of the universe. We’ll get to that in a minute. So if the entire universe is larger than the
portion we can see, how big is it? Well, to answer that question, we need to
back up and be a bit more careful. Let’s start with talking about the oldest
and most distant thing we can see. As it happens, we can’t see the moment the
universe began. That’s because the early universe was so
hot that light couldn’t pass through it. You can sort of think of it like a fog. However, there was a moment about 380,000
years after the Big Bang when the universe cooled enough to become clear. The temperature at which that happened is
about 3,000 degrees centigrade or about 5,400 degrees Fahrenheit. Everywhere in the universe the temperature
was identical. And, at 3,000 degrees, it was glowing hot. So you’d think that when we looked out with
our telescopes, we’d see a glow about like what you’d see in a steel mill. But this is where the expansion of space comes
in. Since that moment, the universe has been expanding
and cooling and even stretching space. The upshot of that is that what once would
have been viewed by the human eye as white, is now no longer visible and can only be seen
by radio antennas capable of detecting microwaves. For that reason, this oldest thing that we
can actually see is called the cosmic microwave background, or CMB, and the temperature of
the universe in the current day is now 2.7 kelvin, or -270 degrees centigrade, or -455
degrees Fahrenheit. Pick your favorite units. So that’s the first big thing. This microwave radiation that measures that
the current temperature universe as 2.7 kelvin is a fossil remnant of light emitted when
the universe was about 3,000 degrees. This temperature is almost the same everywhere,
but we’ve learned that there are very small variations in the universe’s temperature. These variations really are incredibly tiny. The hottest and coldest spots are only a hundredth
of a percent different from the average. Our current best measurement of these variations
comes from a telescope in space called Planck. Astronomers using the Planck observatory have
measured the entire sky and their map of these temperature variations is what we see here. The blue spots are colder than average and
the red ones are hotter. So those temperature differences are pretty
and all, but what do they have to do with the size of the universe? It turns out that these variations were caused
by sound waves in the hot universe just before it became transparent. And because we know the temperature the universe
was at the time, and we have measured the total amount of matter we can see in the universe,
we can calculate the wavelength of those sound waves. It’s a complicated calculation, but a straightforward
one. And I want to emphasize that there is no guesswork
on this. We have heated matter to these temperatures
and we’ve measured the matter we see in the visible universe. We know a great deal about the wavelengths
of sound that were present. Sound in the early universe is pretty much
the same as the sound you use to hear me. Sound is transmitted through variations in
the density of air and you can hear a variety of frequencies. In the early universe, the regions of higher
and lower density due to the sound waves result in hotter and colder spots in the cosmic microwave
background. And, given that we know the wavelength of
the loudest sound in the universe before it became transparent, we can calculate the angular
size of the most common sizes of hot and cold spots in the microwave background. Further, we can calculate what size is the
most likely and it should be one degree as viewed from Earth. Okay- so now we’re getting somewhere. We have a firm prediction of the size of the
hot and cold spots. This brings us closer to our question, which
I remind you is the size of the universe. Now that prediction of one degree depends
on the shape of the universe. Remember that Einstein’s theory of relativity
says that space and time can bend and morph. Space could be one of a variety of different
shapes. It’s hard to imagine this in the three dimensions
that we know space really is, so we have to substitute a two dimensional analogy. Bear with me. A flat two-dimensional space is like the surface
of a table. Flat means flat. But a two-dimensional space could be like
the surface of a globe, where, if you kept on walking you could, in principle, end up
back where you started. This is called a closed space. Another possibility is space could be shaped
like a saddle. This is an example of what is called an open
space. So those are the three basic possibilities
of the shape of space. How does that fit into our question? It comes down to the fact that light travels
in a straight line in space. But, if space is curved, then we can get fooled. Let’s use the hot and cold spots in the
microwave background to see what I mean. If space is flat and a distant spot in the
microwave background is one degree wide, then we will measure its size as one degree. This is the simple mathematics of triangles
that you learned in geometry class, where straight lines travel in – well straight
lines. But that behavior doesn’t have to apply. Let’s see why. For instance, if two ants were in flat space
and they were separated by a certain distance and started walking parallel to one another
in a straight line in that flat space, they will always stay the same distance apart. If you do the same thing on a closed or spherical
space, the two ants will eventually run into one another because straight lines in curved
space are curved. This is like lines of longitude on a globe,
where they are parallel at the equator, but intersect at the pole. And the opposite is true in an open space
like the saddle space. There, the two ants, initially a fixed distance
apart from one another and walking in straight lines, will eventually diverge and get farther
apart. That’s just curved space for you. So this has consequences when measuring the
apparent size of these distant spots of the microwave background. If space is flat, the line that crosses the
spot you’re looking at and the two lines that go from the edges of the spot to your
telescope form a common triangle. But in an open or closed curved space, the
triangles are distorted. Let me be more specific, because this is super
important. In a closed, or spherical, space, what one
would expect to be a straight line is curved in a specific way. The crucial effect is that the angle of the
triangle near your eye is>>bigger

100
Comments
  • I have always believed that when you travel in a true > straight < line in three dimensional space, no matter where you stop, you can always travel along that line one inch more, but some more educated than I say that's wrong. Please do a video explaining this before I go crazy thinking about it…

  • So a closed spherical universe would be 250 times bigger than the visible universe. But what if the universe is not closed/spherical? How big might it be then? Another video (www.youtube.com/watch?v=Iy7NzjCmUf0) says the universe might be at least 150 sextillion times bigger than the visible universe (at 7:50 in the video). Mind is blown.

  • Spolier alert, visible universe is 92 billion light years and entire universe beyond that is 250 times larger. If flat, it is infinite. Like this. @15:00

  • Ok doc. So what is on the other side of the end of the universe? And what space was the universe occupying before the big bang and where did that space come from? Can't create something from nothing!

  • But that would mean the earth is at the center of the universe, and were not even close so the visible universe in one direction will be vastly different.

  • The entire Universe and the visible Universe are different things? Why would we make that kind of a statement or assumption for any reason? Visible to whom and with what equipment?

  • I'm no scientist so I don't know all these math things, I just look at it from a logical perspective. If the universe is flat how come every direction we look at seems infinite? If it's flat wouldn't that mean up and down has a limit? If it's a sphere, which I think it is, because almost everything in space looks like a sphere. And in my head if big bang started the expansion of the universe wouldn't it expand equally in every direction and make big bang the center of our universe? I like astrology but I might have no clue what I'm talking about. It just seems right in ky head.

  • I’ve watched maybe 6-7 videos of this person. So far this is the best one, because it’s the most comprehensible one, the others not so much.

  • You don’t know that no one does if you know that you must know god .you don’t know god you don’t know the size of the universe 🇬🇧

  • Hearing the part where sound waves influenced the cosmic background radiation,makes me wonder if experiments have been done to see if sound effects quantum fields. And what sound does the super collider at Cern make when quarks smash together.

  • 😥 thought he was on point till he mentioned microwaves. I got hungry & used the microwave to warm my food.

  • Sorry, 5 minutes in he went in a direction i didn't like, so I skipped to the end. Spoiler: 92 billion light years x 250 (maybe)

  • seems like a lot of wasted space if its to big to explore, compared to the size of the universe, we are smaller than the atoms our matter is made of. makes ya wonder, why are we here if all that is unavailable to us.

  • Declassofied CIA doc depicts the universe as a torrordial donut.
    That compresses and retracts.

    What if in 100,000 years, we look and notice the universe "shrinking" (as you would, in that model, minus a time given)

    Does anyone else feel like we're locked in a cage when looking out at how sheerly massive the universe is?

  • according to our logic, everything must have a start and end point. Therefore, what is beyond the end point? what holds the 'universe' in place? Simple answer – we don't know.

  • Have never ran into this channel, and just saw this in my feed, so I thought I’d give it a go. Was beyond fascinated with the science taught. You got a new sub out of me! Tyvm! Looking forward to binge watching your channel now 👍

  • naw pal more like it's too complex for you to think there's a creator rather than a fairytail big bang

  • I’m getting fucking sick of these Bloomberg ads every time I want to watch something on YouTube dammit!

  • I have your answer that’s on your chalkboard behind you! I have studied for hours & hours with my many scientific leather bound books. I have a precise answer for you. The answer is 7.

  • The science fields keeps on exploring and studying how big is the universe but still they can't reach it's outermost part. The reason is that GOD is INFINITE before time and manner GOD ALMIGHTY already existed.

  • You can try all the mathematics but you will not be able to fathom an iota of God's secret of the unpenetrable creation of endless dimensions. Science is just a tiny window to the vast creation. You will not even understand time and space of this physical universe, let alone the other universes. However, you can go on creating your favorite hollywood productions.

  • 13.8 billion years ago was the universe began? Really? Because we can see that far then the universe is that old?

  • I dare you to come up with a different “theory “ and you will lose your job, keep repeating the same lie.

  • Our Creation has 7 universes with 7 dimensions above 7 below and 7 within. There are ten to power 49 different Creation forms within the Absolute-Absolutim.

  • The edge of the universe is only 8,000 miles away. Nothing can go further than 8,000 miles away. Sure, we have devices and space tools and eggheaded morons making things up…but what's above us can't be seen truly…space is not vast…space doesn't exist either. There's a window, then a room, then another small portion of a window we try to see everything through…we aren't allowed to look beyond the glass…our round eyes can't even focus on that granduer. Earth, and all that we can see is just the garden…the Kingdom encircles the garden, completely…you can't see what's on the other side of the window within the windows to the Kingdom

  • Yea this guy knows the answer hahah seems legit, notice the Einstein tshirt, tongue hanging out is homage to the serpent!!! This absurdity is for the simple minded!!

  • This is of course not true because it is impossible to calculate the one way speed of light. They assume that light takes this long to get here when in fact they don't know., it could be instantaneous. As for light taking 8 minutes to reach earth from the Sun that isn't true as again it is based on their assumptions on the speed of light. If you sent a beam of light to the Sun you couldn't measure it's return because it wouldn't happen the light would not be reflected back. Hence there is no way of measuring it. The one way speed of light is an unknowable speed. And there is no way of traveling with the beam of light to measure its speed.

  • There will be a sign posted near the edge of the universe. It will tell everyone "No more space. You must turn around." If there's no sign than there will definitely be a brick wall.

  • If the universe is expanding then it cannot be infinite. Another effect of expansion: The further you get from the central point the faster you're "moving" away from it. (So to speak.) Therefore, there is a boundary beyond which we can NEVER see because light cannot go fast enough to get to us. We can't see it. They can't see us. It's impossible to travel there, or to come back. And it would be a shockingly huge amount of a finite, spherical universe. We're stuck in a relatively small little bubble. (If billions of light years is small.)

  • How is it that we live on a spec of dust and now we think we know so much about outer space? Truth is, we really know under five percent at best. Man and yes, females also, haven’t roam earth that long but darn, we are experts! Wow! 👽🛸

  • Question
    Since the Universe is expanding, it must be expanding into something, so what do we call that into which the known Universe is expanding? Does it actually have a name?

  • I was expecting him at the start to go all Hitchhiker's Guide on us.

    "Space is big, really big. You won't believe how enormously big it is. You may think it's a long walk down the street to the chemist. But that's just peanuts compared to space. Listen…"

  • We can see the Visible Universe by looking
    at the sky at night.When we talk about the
    Universe in it’s Totality,there is no edge or
    boundary to it.I believe the Universe was
    created through the Big Bang at a Point
    of Singularity.The Universe is expanding.
    There will be a time in the future when the
    Universe will collapse into another Point
    of Singularity.(Big Crunch).
    I am a Roman Catholic,Engineer/Scientist
    and I believe that God created the Universe
    through the Big Bang

Leave a Reply

Your email address will not be published. Required fields are marked *