The Post Your Thoughts of the Moment Thread 2

[mikey]

So like, the current model of the big bang theory suggests an infinitesimal point containing all matter in the known universe.  We know from looking at the universe now that it's expanding, and thus at one point it must have been smaller.  But what exactly caused the singularity to expand?  And how can we be sure the universe is still expanding now?  Even though we can create an effect similar to that of a big bang, how would a particle accelerator occur naturally in a singularity?

[Clanker37]

^This is a most random thought of the moment.

So for my physics exam in a few weeks I have to explain some of these things (especially the second question), so here's my answers to my knowledge. This may not help and may be better suited for me improving my physics mark
1. We don't know. There is an unproved hypothesis that the Big Bang was the result of collision of two other universes in the multiverse, but this has many assumptions and consequential questions that it don't make sense right now.

O' MIGHTY WALL OF TEXT

2.The Universe is expanding because we can see it. This is known as Hubble's Law which, numerically is; velocitygalaxy = Hubble's Constant x Distance away (v = Ho.d for you algebraic peoples). We know this because of the Doppler effect. So you know how when a police car drives towards you it's tone goes up in pitch, while when it travels away it goes down in pitch? This is the Doppler effect in action.

So here's the tricky part; sound travels in a wave which has a wavelength which is measured as the distance between two places of equal displacement from the mean position of the wave (basically the distance between a wave's highest point and the next highest point is its wavelength). OK, so let's imagine you are standing at a point and a car is travelling towards you like so;


Car(1)                                              You

The car emits a sound wave which travels at a certain speed (x). Let's assume that this is the maximum displacement for the wave (it's highest point)


Car(1)  x(sound wave)                        You

The car will continue to emit the wave and eventually it will emit the highest point of the sound wave again, hence making the wavelength (point y).

Car(1)       y              x                       You

However, if the car is moving towards you, it will emit this second displacement closer to point x relative to you. So point y will move with the car before it's emitted since it hasn't been emitted yet. Where else can it be? However, point x will not move in this situation since it's already been emitted

      Car(1)       y        x                       You

So we can see that the distance between y and x has decreased, hence the wavelength has decreased. Given that a wave's wavelength must be inversely proportional to it's frequency (due to the wave speed equation), this means the frequency has increased. As musicians, we know that if the frequency increases, the tone must increase as it does. The opposite is true for if the car was moving away from you; the distance between two points of the same wave displacement will be greater since the car has moved away from its original point, so the wavelength must be longer hence the frequency must be lower.

This same affect happens in light, since light is a wave (sort of). This is what we see in space; the galaxies' light is being 'redshifted,' which means that their light has greater wavelengths and lower frequencies. Hubble found this and made his law accordingly. What the law also shows is that the further away a galaxy is, the greater speed it has, which suggests that the galaxies are accelerating away from us. This is because they are being carried by the expanding spacetime. So if the spacetime was not expanding or at least slowing down in its expandsion, we would expect this acceleration not to exist. However, it is there since we have been observing it for decades now and Hubble's Law remains true. When it is refuted by new, credible evidence then I'm sure you'll hear about it.

[close]

3. I'm confused by this question. How would a particle accelerator occur naturally in a singularity? It doesn't; we built it. Or do you mean "How would a singularity exist in a particle accelerator?" I don't know the answer to this question. I could bullshit some answer about E = mc^2 and the mass of particles, but I do not think that would be either correct or advantageous to this question.

[mikey]

I know about redshift but when we look at galaxies we're seeing them light years in the past.  Is there really a way for us to know whether galaxies are moving right now?

[Clanker37]

So the nearest object which we have seen redshift is the Virgo Supercluster;

Virgo  z=.0037      Distance = 52 Mly

Obviously, even though its red shifted the light will take 52 million years to reach us, so your question remains valid. To my knowledge, I can't answer this question, but it's a really excellent question. I'll ask my physics teacher and see what he thinks.

The only answer I can possibly give is that the objects closest to us are being blue shifted, since they are travelling towards us. If the Universe started contracting, one would assume it would do this all at once (can the contraction of space time have a speed over its distance across the universe??), so the galaxy's blueshift would be greater since not only gravity is affecting it but also the contraction of the Universe. But since (I assume) the speeds and blue shifts of our closest galaxies are congruent with out gravitational equations, then it mustn't be contracting, since we can see and explain its speed due to gravity. (I assume that physicists would take the expansion of the Universe into account when calculating these things)

I would say 'just trust physicists,' but this is so contradictory to my everything ever that I would literally explode.

[Zunawe]

There are more reddish things in the sky than bluish things. Enough that we can say that all space is expanding. We know whether a galaxy is blue shifted or red shifted by its spin. The Doppler effect applies to each half of a galaxy separately as it spins either away from us or toward us. If the red shift caused by the spin is more dramatic than the blue shift caused by the spin, the entire galaxy is moving away from us.

[braix]

Gosh I just slept in class for an hour and I'm so refreshed

[Oronoco]

I miss taking naps in High School.

Now they're not as cool because NOBODY CARES if you take a nap. (They're still very much appreciated, though.)

[Yugi]

So I learned today that being the only guy in the room when there's a discussion on domestic abuse is the most uncomfortable thing ever.

[Waddle Bro]

nsm bans politics but allows racist jokes i'm just saying

[braix]

sorry i might have started that

[Olimar12345]

nsm bans politics but allows racist jokes i'm just saying

That's because we can't have calm debates. At least racist jokes are at home in their designated topic.

[InsigTurtle]

Is racism, when used humorously and without the intent to offend, still okay when the forum rules explicitly state that there is to be "No racism, sexism, or any other form of discrimination"? Or is this a special exception because it is in its special topic?

I'm not asking for the topic to be taken down, I'm just wondering.

[Bespinben]

Perhaps it's practice for the inevitable NSM Cards Against Humanity tournament.

[InsigTurtle]

I'd be down for that, actually. Online, of course.

[FireArrow]

noooo, I suck at that CAH.:[[

Is racism, when used humorously and without the intent to offend, still okay when the forum rules explicitly state that there is to be "No racism, sexism, or any other form of discrimination"? Or is this a special exception because it is in its special topic?

I'm not asking for the topic to be taken down, I'm just wondering.

I think it depends on the joke.

Not ok:

Spoiler

What did God say when he made the first black man? "Damn, I burnt one."

[close]

Ok:

Spoiler

Q: Why can't atheists solve exponential equations? A: Because they don't believe in higher powers.

[close]