1 the claim is that the universe is approx 14 billion years old. Why is this claimed as the age of the universe and not the minimum age of the universe? This number is used bc the farthest object we get light from is 14bil ly away. Why is it impossible the object traveled to get to it's position, how do we know it sits at the origin of the universe?
2 why there is a diffraction pattern for 1 slit? there is only one slit so the particles waves cannot go through 2 slits and cause diffraction
3 Why is the double slit equation from the 1930s still used today when the experiments have changed over time? When the equation was derived, an aperature was used, today we use lasers. The light of lasers is as intense in the center as around the edges, whereas in an aperature,the light is less intense around the edges. These are 2 different experiments.
4 Why is EM ignored during the double slit? It is assumed that a surface made of charged particles has no effect on incoming particles.
5 During the double slit experiment, when an electron is the projectile, it is assumed that the electron travels a straight path. But electrons are not spherical, they're lopsided. When you "shoot" an electron, it doesn't travel straight. Is there math for this?
6 it's claimed that because objects far away are red shifted, space is expanding. Why do we jump to space expansion rather than just say the objects are moving away from us in an already expanded space?
If you're running in a group, 1 in front of you 1 behind you and the guy in front starts running really fast, the guy behind you slows down a lot and you stay the same pace, both runners will appear red shifted to you but the space has not expanded, they've moved away from you within space. Why is this less reasonable than "space expands"?
Red shift really is a photon at a certain frequency. Its created by the source not the space around the source. Space doesn't alter the frequency of photons, but the source of photons can.
These are the sort of things that bother me as well, and are what a useful /sci/ would be discussing.
Unfortunately I'm worthless and can't add anything beyond that I share many of your doubts about this modern certainty we're fond of claiming.
2/3/4/5 please someone
>>7742127
>But electrons are not spherical, they're lopsided. When you "shoot" an electron, it doesn't travel straight. Is there math for this?
I though electrons had no shape or volume, were just point particles, and were accelerated by magnetic fields, they would travel in a circle until the magnetic field was shut off which would release them tangentially.
1. This isn't how that number was determined. The age of the universe is determined off the big bang model, in which the rate of expansion is extrapolated back to determine the age. We can't actually see that far back obviously, but we can see back about 13 billion years.
2. The slit is supposed to be smaller than the wavelength of light in these experiments. The basic model that explains essentially says that this "breaks up" the wavelength of light along the slit which then produces new light sources at every point in the slit. These new light sources are what interfere with each other.
6. We know that it's space expanding because a.) if it wasn't some of these objects would be violating special relativity (not likely), and
b.) The shift in wavelength due to space expansion can be accurately accounted for by general relativity. Note that this is not the only factor which contributes to redshift.
also,
5. Idk where you read that electrons are lopsided. Depending on the model, I've read they're either point particles or most likely perfectly spherical.
>>7742127
>2
Huygens principle, the slit acts as a source for secondary wavelets that cause interference.
>3
We get the same results if you use a laser over an aperture.
>4
Because it doesn't contribute. Think of it like friction in classical mechanics, ultimately the source of friction is electrodynamical, but you don't need to consider that when looking at a ball moving across a surface, just the bulk property.
>5
I really don't get what you mean by this. Electrons are structureless point particles.
>1/6
You've misunderstood some cosmology, unfortunately I don't know enough to set you right.
And 3. what's important is that the light is monochromatic. intensity doesn't matter, you'll get the same fringe pattern, it might just be dimmer.
1 idk, I haven't taken astrophysics
2 The pattern happens because the wave diffracted off the left edge of the slit interferes with the wave diffracted off the right edge of the slit.
3 Actually the double slit equation assumes a laser-like beam: same-direction same-intensity rays. The old experiments used a collimator in front of a light source to do this.
4 Good question. Idk.
5 What do you mean they're lopsided? They *can* travel straight. They're point particles; I don't know the math, but my professor explained that they need 0 radius because anything else will pose problems for electron spin.
6 I'm not sure. Like I said I don't know astrophysics too much, I'm still undergrad. But I do know that we can see the redshift anywhere we look, so either space is expanding or everything is just accelerating away from each other, at least.
>The Wilkinson Microwave Anisotropy Probe (WMAP), an orbiting observatory, spent a year making a detailed map of minute temperature variations in the CMB (cosmic microwave background - illustrated). Models of the universe's evolution make specific predictions of what such patterns in the CMB would look like. In 2003, WMAP scientists announced that they had compared their satellite's "baby picture" of the universe to various predictions -- and found a match for a specific set of characteristics. The WMAP data indicate our universe is 13.7 billion years old, and made up of only four percent ordinary atoms. Dark matter makes up about 23 percent. The remaining 73 percent is the enigmatic "dark energy."
3) The experiments are pretty similar. The only difference is that the lasers have a focused beam meaning the diffraction pattern is more readily seen. Using white light from a bulb just muddies up the experiment a bit and makes it harder to observe the 2nd and 3rd constructive waves.
4) To be able to understand most things meaningfully you need to simplify them. The effect of the walls charged particles is taken into account slightly by the fact that the waves cannot penetrate through the wall. However, trying to calculate the photons interaction with each individual electron and proton within the wall would just make the problem too complicated, without changing the result by much.
6) If all large objects are moving away from the earth and from each other, then it makes little sense to think that they all are traveling away from each other. Also them simply moving away from each other would not explain how there is an acceleration in the expansion.
Space does alter the the trajectory and frequency of photons providing it is expanding/contracting/bending in some way.
The source of the photons does matter, however spectral lines from the electron orbital energies in atoms are pretty static. Electrons in hydrogen atoms moving from a 2s orbital to a 1s orbital will emit the same wavelength photons anywhere.
5) Also electrons are not lopsided. They are point particles as far as we can tell. What made you think that?
>>7742399
Huygens principle is fucking bullshit though. Never accepted that shit brainfart of an idea in my Optics course.
>>7742127
>the farthest object we get light from is 14bil ly away
no
http://youtu.be/zO2vfYNaIbk?t=7m40s
>>7742620
>4% ordinary atoms
>23% dark matter
>73% dark energy
When will we finally fix this shit?
I really have no idea what you mean by 5. You must be thinking of the Stern-Gerlach experiment, or something.
>2
First, you seem to be confused about what diffraction is, the phenomena you seem to be referring to with the 2 slits example is interference not diffraction.
To explain diffraction what you need is the Huygens principle and this can be understood in the following way: the wave you have always has to satisfy the wave eq. with certain initial conditions, this means that we can predict the form of a wave at a time in the future if we know how it was a certain time in the past, in particular we can obtain the new wave in terms of the form it had an arbitrarily close moment in the past. So let's apply this, you have a single slit and a plane wave. In a small neighborhood around a point the problem hasn't changed, you still have a plane wave without any obstacle, this means that at each point of the slit our function still has to look like plane wave, so to get the result we just have to add up each wave at every point of the slit and, lo and behold, you get the Fourier transform of the slit, which gives you the diffraction pattern when you calculate the intensity.
>3
>The light of lasers is as intense in the center as around the edges, whereas in an aperature,the light is less intense around the edges
lol wut? For the experiment the intensity is pretty much the same over the slits/aperture.
>4
You're not that interested on the dynamics of the electron, just that there is an obstacle that the electron can't pass through and two little slits where it can.
>5
>it is assumed that the electron travels a straight path
Nope, you just assume that it's represented by a probability wave and then at the end you get an interference pattern
>But electrons are not spherical, they're lopsided
Nope, we treat electron as point particles with no structure
(1/2)
>>7744653
>1/6
I don't remember much from the little we covered of cosmology in my modern physics course and I don't really care much for the field, so don't take for grated my answers.
The age of the universe, if i remember correctly, is calculated from a formula that involves the hubble constant, in fact you can make a rough estimate simply by taking it's inverse.
We conclude that the universe is expanding simply because when we observe objects they're always getting away from us. They way they concluded that the rate of expansion is increasing is pretty cool you can check it out here https://www.youtube.com/watch?v=HppSNAPYvN8 they also have other videos covering topics in physics for laymen
>>7742620
>>7743556
I dont know, I am hoping the James Webb and eLISA telescopes will clarify things coz currently we are staring at a fucking huge hole in pretty well entrenched physics theories and laws.
Its driving me mental, an itch that cant be scratchedmand with differing research teams on different tracks.
