Scale of Universe Tool

[dogjones]

This is a very cool interactive scale tool.

http://primaxstudio.com/stuff/scale_of_universe/

Which has generated two questions. First, where would photons be? I know they are point particles and have no size; what does this mean in relation to the Planck length? Are photons smaller, the same, or just different? (I actually thought they were similar to electrons but according to this electrons are high-ish up in the quantum scale, higher even than neutrinos)

Second at very highest of the scale, it says the universe is estimated to be 93 billion light-years across. Where does that estimate come from?

 

[DrDave]

Second at very highest of the scale, it says the universe is estimated to be 93 billion light-years across. Where does that estimate come from?

Katie Melua

 

[Wowbagger]

Ah, the music of Spore.

 

[dasmiller]

First, where would photons be? I know they are point particles and have no size; what does this mean in relation to the Planck length? Are photons smaller, the same, or just different?

I really wouldn't describe photons as point particles. True, their 'size' isn't quite as neatly defined as, say, that pencil on my desk, but photons definitely have a wavelength (that is very clearly defined) and they interact with other objects in a manner that relates to the wavelength.

And you'll find a number of wavelengths on that site as you zoom in. You can think of those wavelengths as being the 'size' of the associated photons.

 

[dogjones]

Well sure, but there is also a picture of an electron as a particle. Don't electrons have wavelengths also? (ETA: yes, their wavelength is in the model) Also I thought that the waveform "describes" the probability of a particle being in a particular place?

 

[dasmiller]

Well sure, but there is also a picture of an electron as a particle. Don't electrons have wavelengths also? (ETA: yes, their wavelength is in the model) Also I thought that the waveform "describes" the probability of a particle being in a particular place?

You'll need better minds than mine to explain the whole wave-particle duality thing.

 

[Wowbagger]

You'll need better minds than mine to explain the whole wave-particle duality thing.

The "duality" is probably only an apparent one, due to limitations in how we are capable of measuring these things. In reality photons only behave one way: Like photons.

 

[portlandatheist]

At the end it says "we're probably not at the center of the universe" which I think is an odd think to say as it suggests that there is a center of the universe. Nevertheless, its a cool use of flash.

 

[Dr. Keith]

Neat tool.

What I like is how clear it is that the range of things we are comfortable with is so limited. The orders of magnitude between, say the size of the US and a quail egg are very small on that scale. Very cool.

 

[Monketi Ghost]

Fascinating. Thanks!

 

[dasmiller]

At the end it says "we're probably not at the center of the universe" which I think is an odd think to say as it suggests that there is a center of the universe.

Yeah, I wasn't wild about that line either. There are contexts in which it might be sort of true (offhand: a non-infinite universe, non-uniform at the largest scale but with more-or-less homogeneous regions, and we're not at the center of a homogeneous region) but even so, I think the wording is misleading. Better, but wordier, would have been something like "The universe probably doesn't have a 'center,' and even if it does, we're probably not there."

Nevertheless, its a cool use of flash.

Absolutely!

 

[dogjones]

Yeah, I wasn't wild about that line either. There are contexts in which it might be sort of true (offhand: a non-infinite universe, non-uniform at the largest scale but with more-or-less homogeneous regions, and we're not at the center of a homogeneous region) but even so, I think the wording is misleading. Better, but wordier, would have been something like "The universe probably doesn't have a 'center,' and even if it does, we're probably not there."

Yeah. Perhaps they are just trying to say "we ain't special" to all the Ptolemaians out there?

ETA: Actually just looked at it again. Although it says "we're probably not in the centre", the picture seems to depict it as such. They were probably just trying to say "don't visualise the universe like the picture". Actually this goes back to your comment. Ohhhhhhhh man.

And per my OP, where does their 93b ly figure come from?

 

[NoahFence]

I like the size comparison between an unsolved and a solved Rubix cube....

 

[Corsair 115]

At the end it says "we're probably not at the center of the universe" which I think is an odd think to say as it suggests that there is a center of the universe.

I think that's just a reference to the fact that the zooming out process is centered around our planet, then our solar system, then our galaxy.

 

[sol invictus]

Well sure, but there is also a picture of an electron as a particle. Don't electrons have wavelengths also? (ETA: yes, their wavelength is in the model) Also I thought that the waveform "describes" the probability of a particle being in a particular place?

The "wavelength" of an electron at rest or slowly moving is h/(mc), where m is the mass of the electron, h is Planck's constant, and c is the speed of light in vacuum. That's more or less its size - it's the approximate radius of the region where you might find the electron if you look.

If the electron is moving very fast, so its kinetic energy is larger than its rest mass energy mc², then its wavelength is h/p, where p=γmv is its momentum. If you like, you can think of the difference when γ is big and v~c as due to Lorentz contraction (that's why there's a γ factor).

Photons are always moving very fast, and their wavelength is therefore always just h/p, where p is the photon's momentum.

 

[quarky]

I didn't realize that a human egg was visible to the naked eye.
I'll be looking more closely from now on.

 

[Tubbythin]

And per my OP, where does their 93b ly figure come from?

See here.

 

[mike3]

The "duality" is probably only an apparent one, due to limitations in how we are capable of measuring these things. In reality photons only behave one way: Like photons.

Does this mean there could exist a vast layer of reality which we may never be able to explore?

 

[Furcifer]

I don't know if you've seen this reconstruction but it's pretty cool as well. It'll make you feel the size of a photon.

 

[Aepervius]

I didn't realize that a human egg was visible to the naked eye.
I'll be looking more closely from now on.

They have an error inside, they cite 2.5 mm for human egg, it is actually 0.25 mm (2.5*10^-4 m). You can compare with the other items around it.

IMO 1/4 of a millimeter is not exactly viewable with naked eye, unless you count a dot as "viewable".