What is the horizon problem? 

So you made up a fictitious "rapid expansion" period to validate a problem with your theory. Great science.

Keep coming back to this video when I need to remind myself of the horizon problem. I think I first saw it as an undergrad. This time I'm preparing for a PhD viva... Great explanation!

Loving the effort on increasing the uni's exposure through media. Keep it up!

I like how you just say they effectively travelled faster than the speed of light like that's a easy way to solve it. lol.

Well thanks, very understandable comparing to other people's explanation.

I would love an explanation of what kind of thing is the Big Bang itself that without factoring in inflation is too big at the time 0 and has to have points of different temperature.

Wow that was so easily explained. Thank you!

wanted to say thank you this video helped me finish my assignment on horizon problem

I’m confused. At one point A and B were touching at the very beginning when the the universe was a tiny ball. Didn’t they have time to touch during then before being pushed away faster than the speed of light? This seems like common sense. Am I missing something?

Great explanation, thanks!

Great video. Concise and covers the key points really well! I would point out that at the surface of last scattering when the universe became transparent the EM radiation is actually in the infrared region (since z = 1100). Thus, it didn't go from orange > red > IR > microwave - it went from IR > microwave.

Do A and B really need to be touching at one point in time in order to explain this? What if they are the same temperature because they both obey the same laws of physics and the universe was created in the same way everywhere?

Perfect explained Thank you

This explanation represents a lapse in logic. Other than that, it's perfectly lucid and understandable, like the phrase, 'the moon is made of green cheese'.

What about the flatness problem and its relation to the horizon problem?

I have a question. Why does the furthest points have the same temperature but anywhere inside of the horizons has different temperatures? What properties of the furthest points (the horizons) is different from anything inside of the furthest points that is only causing the horizons to have the same temperature but nothing inside of it?

Honest question: how do you look in two directions at once? Professor said when we look back in time (and then drew an arrow) and then we look in this other direction (and drew a second line). So, how are they physically looking in these two planes?

Its a guess not a solution

I’m confused? I thought nothing moved faster than the speed of light, Yet it’s theorized our universe did for quite some time???🤯

hi my name is Haumea im 8 years old and love Physics Sience and chemistry and i lovs the video

thx for the video, i have a question: you say at the time of inflation the expansion was "effectively faster than light" how could that be? that breaks the fundamental law of physics about the velocity of light! also since the points A and B started from the same point in the beginning then it is not odd that they have the same initial conditions. I stilll dont see the problem thx Prof!

The age of the universe, and the speed of light, doesn't appear to match up with the observed size of the universe.

30 seconds into a 3 minute video and it gets to the point.

If it is impossible to accelerate something to the speed of light because it would require an infinite amount of energy, how were objects A and B accelerated beyond the speed of light?

That why I love physics,it give confidante meaning for living

How did the universe expand in the first place if the sum of all mass was concentrated in one area, or point? If light and matter cannot escape a black hole, how could anything escape gravity of the mass of all things in one place?

soooo, where did the fire come from ?

Hi Malcolm.. Nice Video.. very interesting indeed.. Let me ask you one thing and what you think.. What would happen to our Universe if a new Big Bang would take place in our already existing universe.. as we know it..? please try to answer me.. this question keeps me awake night after another... My Best regards / The Thinker

However, in opposition to the point A and B separation (the solution to cosmological expansion and the big bang), their seems to be an odd sense of milky-way centrism that contributes to the homogeneity problem (in reference to the "observable universe"). Also, structures are being analyzed that are too large and fully formed for a universe age of 14-ish billion years… which was a major dependent value of the big bang. Humans do seem to try and consider everything too often in a specific singularity. I'm not trying to negate what could be called "the big bang" so much as I am negating or arguing against "the" big bang. Aside from big bang(s), there still is dark energy, supernovas, quasars, other radiation sources (i.e. solar wind), centripetal force, Lorentz transformations (and by that I mean large scale, long distance accelerations coupled with dark energy… i.e. galaxy rotation mechanisms and galaxy acceleration), and gravitational slingshot effects which go against an otherwise inevitably highly concentrated source… from the effects of gravity.

Now I don't get why it was seen as impossible. Damn.

It's a proposed solution, no? Are you, sir, uncomfortable with uncertainty?

soo you say is not linear is just 2 points of the same expansion....well if that soo in the middle of it.... it will be more or less strong of B and A that is my thinking to prove that you are rigth

"Then there was a period called cosmological inflation when the universe expanded quickly, effectively faster than the speed of light, where A got zoomed out over there and B got zoomed out over there even though that appears to be impossible. And that's how we've got the solution to the horizon problem!" ... That's not a solution.

I like the usage of minkowski diagram.

My simple question is how did they determine the distance of the cosmic microwave background radiation from us?

As a Christian, speaking to the other Christians, please understand that "God created" is not unequivocally the best answer to the Horizon Problem. We Christians have the same exact problem, which is called the Starlight Problem. If, as a Christian, you believe in "young earth creationism" or "literal creation theory", then how did the light from a star reach earth from millions of lightyears away, if the earth is only 6,000 years old? This is not a stumbling block, and this is not a man who is attacking your faith. It is a man explaining how to think through solving this very real problem in our limited capacity. Also, if you base your views of science on a single 3-minute video, that might be another problem altogether. Give the thought credence, and evaluate our own Starlight Problem. By Faith you are saved, but that doesnt mean you cant evaluate and be in awe of what we have around us. It doesnt mean we arent allowed to ask questions....

Einstein said that matter cannot travel faster than light. Therefore, no solution and no cigar.

Why does it matter that they have the same temperature? "because they didn't have enough time to reach each other" Yeah I know that but I am saying why cant it just be a coincidence?

3 minutes - 30 seconds of intro - 10 seconds of outro

Another explanation: A and B are actually physically close to each other but light is bent.... which means... there's a blackhole between them and us... hmmm.... who's with me?

Elegant solution, but what evidence is there for it?

I do not understand the problem. We think that the universe started almost in one point. So it would not be suprising that all sufficiently large regions of the universe had basically the same starting conditions. Then they developed according to the same laws of nature. So why wouldn't they all look very similar now?

the person on the photo is my mumy

omg people! Expansion of space is _not_ a motion of space, it is a motion of separation of particles. The space does not actually move. The particles never move faster than light speed, nor does the distance between them "move", the distance between them can increase faster than light speed, but it does not "move" anywhere. Separation between particles is not a particle, it is a quantity that depends on observing two separate particles, not observing anything in-between them. So nothing in-between needs to be moving at all. Same, or similar, to how you can make a shadow move as fast as you like, faster than light if you can project it far enough away and still see it. When a shadow moves nothing _in the shadow_ is moving (you cannot get knocked over by bumping into someone's shadow, except psychologically). So... the lecturer misspoke. Space never has expanded "faster than light", space does not expand. Distance between particles does expand, but that is not itself a physical particle --- not a physical mass --- separation between masses is a correlation function, not itself an object. So when someone says "expansion of space" always think of it as shorthand laziness for "separations between past event world-lines increasing." Always there must be a reference to two or more objects to measure the gap between. A relational quantity, not an absolute quantity.

spherical horizon explained on my channel, lemme know what you think.

well that is not a problem to begin with that actually is quite obvious ... i didn't think that was even a problem

The problem is it either makes the hypothsis wrong or it says that period of time science does not apply rendering it a bad hypothsis not a Science Theory .... My more sensible solution would be that rather than adding an inflation period , realise that because of the massive gravity and speed of expansion that TIME moves so much more slowly that the universe expanded much more than people realised then .... what is my proof of the inacurate calculation ? Well obviously if time runs more slowly but light moves at the same speed from the observers point of view inside the universe ,,,,, light move move further at the beginning of time because it moves the same distance but time is essentialy slower allowing for that to happen ..... So my proof is that Planck says that light in 10X-43 sec moves 1.06x10-73 Meters ,,,,, So if light moves that far in that time TODAY it would have moved MUCH further when time ran MUCH slower back then making the inflationairy problem not a problem .... Their is a calculation obviously that takes some of my theroy into account because the hubble consant would put the universe at 60 billion years not 13.7 , it's my contention that the "inflationairy period" would not be necesary if you calculate the speeding up of time as the gravatational pull , less mass, and slowing velocoty correctly , because you would have your basic expodential curve of time ..... speeding up VERY slowly in the beginning and then accelerating very quckly later an the stabalising .... the same essential outcome but using actual SCIENCE not making a period of time outside of science and calling it a scientific answer ..... which it's NOT .... it's a hypothsis at best .... one I claim to be unnecessary and absurd as well.

If we're seeing the same thing,(red shift, background radiation, etc), in every direction then we would have to be at the exact center of the universe. ...And the chances of that not being the case is quite literally astonomical.

This doesn't make sense to me. Imagine a meteorite hitting the ocean, the shock-wave moves at the same speed in all directions, right? Same thing with the universe, you have uniformity because the result is more like a big wave than a big bang. There is no point A and point B. IMHO the horizon problem doesn't exist. There is no spoon!

gee whiz! you got any evidence of that

fairytale!!!!

The real solution is found in the Bible. Isaiah 45:12 "I am the one who made the earth and created people to live on it. With my hands I STRETCHED out the heavens. All the stars are at my command."

Liar, Liar, pants on fire. Universe is NOT expanding

This sucks

see the big bang never happened( youtube)

LOL he so out-updated .. I hope this guy isn't teaching you physics

...faster than the speed of light? Sounds like a bullshit wrapping up to some failed theory