This gives some perspective to our lives :o
Start this NASA demo and move the bottom horizontal slider.
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Well, it answers the question of: "how long is a piece of string". Apparently: 10-35.0 meters!
This would be a great demo for children in science class.
we may be mediocre in (logarithmic) size but our minds can oversee the whole range
(at least we want to think so)
pYro_65:
Well, it answers the question of: "how long is a piece of string". Apparently: 10-35.0 meters!
But only in theory. 
So a string is 10-35
The universe is 1027
So the universe is 1066 bigger than a string.
100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000
I wonder how many strings are in the universe. Or is that "Strings" PalulS?
:o
I seem to recall a short film (Canadian I believe) with a similar theme years ago. It started off with the image of an insect biting someone, zoomed in down to atomic level then zoomed out to show the universe.
LarryD:
So a string is 10-35
The universe is 1027So the universe is 1066 bigger than a string.
100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000
I wonder how many strings are in the universe. Or is that "Strings" PalulS?
:o
The universe is that bigger in all 3(or more) dimensions so in fact the universe is at least 10200 times bigger than a string. So that would be my 1st order estimate.
As we recently know the universe is expanding it could just be that the number of strings is increasing(?).
How long is a string from a photon's pov? hehehe
robtillaart:
The universe is that bigger in all 3(or more) dimensions so in fact the universe is at least 10200 times bigger than a string. So that would be my 1st order estimate.As we recently know the universe is expanding it could just be that the number of strings is increasing(?).
I have a theory. It's probably all wrong due to the fact that I'm an EE and not a physicist, but here goes:
Edwin Hubble saw and measured the red shift in the well known spectrum of hydrogen (i.e. fusion in stars) and found that no matter which direction he looked, ALL the radiation was red shifted, and the further away the source, the more red shifted the light was, implying that everything is moving AWAY from the viewer, implying that the universe is expanding.
But, even the "empty" vacuum of space contains hydrogen atoms, elements from super novas, dust from planet and asteroid collisions, etc...
In their travels, can't individual photons collide with interstellar "junk" and lose some energy? And, what happens when electromagnetic particles lose energy? Their wavelength gets longer (i.e. light is red-shifter).
And of course, the further away a star or galaxy is, the more chances and the more times a photon is likely to lose energy, so the further away the source, the more red-shifted the photons become.
Am I right - that this could be possible and Hubble was wrong, or is there something fundamental about electromagnetic energy and photons that I just don't know?
@Krupski
(no physicist by profession either but sort of autodidakt)
You are very right that photons loose energy as they bump on matter. The chances are however still very very small and the photons that collide would go in another direction -> therefor not reaching Earth. Most of the photons will come to Earth without collision. If they did the pictures could not be as sharp as Hubble makes them.
Note that a flashlight going though air meeting many many more molecules than there are in the vacuum of space can still give a bundle up to 1KM or more. Even under clear water, which is more compact, light travels dozens of meters.
What does happen is that light can be bend by gravity, causing a star or galaxy to appear on a slightly different place. This can even cause gravitational lensing (google for a picture) in which we see a star brighter than in reality (bit like a magnifying glass). As not all gravitational lenses are perfect the paths of light from a galaxy to Earth can differ slightly so light that left at t=0 arrives at Earth at different moments. This helped astronomers this month to predict the appearance of a supernova for the first time!
See - http://www.skyandtelescope.com/astronomy-news/astronomers-predict-a-supernova-12222015/
I believe that if individual photons are absorbed or scattered you would not see a red shift. You would see a reduction in the number of photons which translates to a reduction of light intensity, not wavelength. If individual photons lost some of their energy in collisions it would be a quantum change in energy and would show up as dark spots in the spectrum. I believe what is observed is a continuous shift depending on distance, not quantum shifts like you would get with photon collisions.
Hi,
Now explain that using wave not particle theory of light/energy?
I was taught that light behaves with wave and particle characteristics.
The red shift can be explained by Doppler shift in wave theory.
Tom......
The red shift can be explained by Doppler shift in particle theory too.
If the space is expanding while the particle travels it will look less energetic.
TomGeorge:
Hi,
Now explain that using wave not particle theory of light/energy?I was taught that light behaves with wave and particle characteristics.
The waves are affected by the gravity just like the particles are. They choose the shortest path and when space itself is bend the wave will bend with it.
Good explanation here.
"First, let's put aside the idea of the photon losing energy in transit, as an explanation for redshift. A photon doesn't lose energy unless it collides with a particle. Photons can scatter off interstellar electrons, for example. (Perhaps you were thinking about particles, like electrons, losing energy "in transit" in a vacuum. That can happen if they change direction. Electrons radiate and lose energy if they travel on a curved path around a magnetic field line.) Photons carry energy, but they don't lose energy just because they travel.
The key to understanding the dilemma of a red-shifted photon is that not all observers will measure the same energy of the photon. Let's say an observer is traveling with the star or galaxy and sees a photon in the yellow portion of the spectrum. An observer who is moving with respect to the star (it doesn't matter if it's the star or the observer moving away) sees the same photon in the red part of the spectrum. That's OK--it doesn't violate the principle of conservation of energy--because they make their measurements in different reference frames. Similarly if you roll a marble while you are riding on a train, you will find that the marble has a certain velocity and kinetic energy as seen from your seat in the train, but an observer in the train station, who (somehow) sees the marble as it goes whipping by on the train, measures a different velocity and hence a different kinetic energy. The energy of a photon comes from its frequency, and that is different for different observers."