Dark Matter

[Royost]

DARK MATTTER

by

ROY PACKARD

I drove down to Seal Beach today. Got a cup of coffee at Bogart's and walked across the street to Eisenhower Park - a piddling little park of about a quarter of an acre in size - but nice. Got a bench overlooking the ocean and sat and did what old men do - supped my coffee, watched the pretty girls and dreamed of days gone by. There weren't any girls today. Just one old lady in a wheel chair being push by her husband who was also in a wheel chair. So I sat and dreamed of days gone by.

Beautiful day. Could not have been more so. The temperature was 71 degrees F. There was a gentle Santana wind wafting down from the mountains and out to sea. The water was calm. Three surfers hoping for some waves but not getting any.

All was quite.

So I sat and supped my coffee.

And thought again about this dark matter problem.

Theorists have been concerned, for some time now, because they can account for only 13% of the total mass of the Universe. That 13% includes everything we know - you, me, little babies, the Earth, the Sun, the Solar System, all the galaxies and all the stars and planets in the Universe. They know the other 87% is out there; they just don’t know where.

Before I proceed, a little refresher course in scientific notation may be in order. Very large numbers and very small number can take up a lot of space if written in the normal manner using decimal places as you were taught in high school.

For example, the number of atoms in the Universe is 10 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 plus or minus a few. Well, you don’t want to be trying to say that nor writing that down every time the subject comes up, so a short-hand scheme is available using exponents. The same number can be shown as 1e79. Isn’t that a lot easier? (Perhaps Obama ought to start using scientific notation. His 16,000,000,000,000 debt could be expressed as 16e12. Isn’t that so much more pleasing?)

Now, we get to the heart of the matter.

Since the Big Bang, light has been emitted into the Universe. Every visible object we see is emitting or reflecting light. Let us concentrate our attention on stars since those generate the most light. Planets, meteorites and asteroids give off reflected light. Standing here on Earth we see stars as a small dots or spheres. But those stars are emitting light out in all directions creating a light sphere. Standing anywhere else in the Universe we would see the same stars as small dots or spheres.

The fact is, we cannot see light. We can see the source of light and we can see the objects from which light is reflected. Otherwise, when we look out into the Universe, we would see nothing but light. (Try this. Don a space suit, grab a flashlight and step outside the ISS (International Space Station). Now, aim the flashlight away from you and turn it on. You see nothing. Put your hand in front of the flashlight and you see your hand. Aim the flashlight toward you and you see the source.)

All those stars pumping light out into space. Some since the beginning of time, as we know it. And that light is still out there. We just don’t see it.

And what if that light had mass?

In fact, it does. Not a lot, but it does.

The rest mass of a single photon of light at a wavelength of 500nm is 4.417e-36 kg. That's 4.417 with 35 0s to the left of the 4 - a very small number.

The volume of the Universe is 2.058e79 cubic meters. That's 2.058 with 76 0s to the right of the 8 - a very large number.

So, how many photons would be required per cubic meter of the Universe if all the dark matter is really light?

The mass density of the Universe is 6.000e-27 kg per cubic meter. By dividing the mass density of the Universe by the mass of a photon, we get 1.358e9 photons per cubic meter - a very plausible number when you figure the mass density of photons near the Earth is 4.217e13 photons per cubic meter.

So, I am going to go with that. Dark matter is really light. Now all I need to do is to convince a bunch of very bull headed and exclusive theorists of it. They don't like outsiders messing around in their area.

[Strange]

And what if that light had mass?

In fact, it does. Not a lot, but it does.

The rest mass of a single photon of light at a wavelength of 500nm is 4.417e-36 kg.

 

No it doesn't.

 

But apart from that, the energy of electromagnetic radiation is already taken into account in the known mass-energy of the universe.

 

As you seem reasonably numerate, why don't you take the next step and find figures for the photon flux in the universe and work out the total energy.

[Bignose]

Now all I need to do is to convince a bunch of very bull headed and exclusive theorists of it. They don't like outsiders messing around in their area.

Wow, confrontational much?

 

What scientists really like is predictions and agreement with measurements. If you can demonstrate that your idea makes better predictions than their models, you will get a bunch of attention. If you come in all angry about the 'bull headed' people, then your rudeness will be responded to in kind.

 

So, in short, I'd advise you to drop this confrontational attitude and focus instead of turning your idea into specific testable predictions and comparing them to known measurements. I'd also drop all the quips about politics in your delivery, too.

 

For example, if you can use your idea to recreate the map of where dark matter is concentrated, http://www.space.com/14176-dark-matter-biggest-map-unveiled.html, your idea would receive quite a lot of attention.

Edited September 26, 2014 by Bignose

[timo]

Makes me wonder why Royost thinks he doesn't have to convince the experimentalists. One would imagine that they are much more bull headed and exclusive that the theory guys. If I can vote for a prediction I'd prefer the calculation of the light density over the dark matter distribution one. Reason is that I feel that if you accept the dark matter distribution you could just as well accept that dark matter is not hot (i.e. the ratio of momentum to invariant mass is small) which would rule out photons in the first place. Light density sounds much more interesting, because one can have some fun thoughts about it (e.g. an upper level of possible wavelengths due to lack of detection), and because I have no feeling about what would come out of it.

[EdEarl]

IIRC the distribution of dark mater is densest in a somewhat spherical shape around the center of galaxies with strands stretching between galaxies. However, the flux density of EMF (light) in the Universe would resemble the cosmic microwave background radiation I think. Thus, the distribution of the two are different, which does not suggest they are one and the same.

[Janus]

 

DARK MATTTER

by

ROY PACKARD

 

 

Theorists have been concerned, for some time now, because they can account for only 13% of the total mass of the Universe. That 13% includes everything we know - you, me, little babies, the Earth, the Sun, the Solar System, all the galaxies and all the stars and planets in the Universe. They know the other 87% is out there; they just don’t know where.

 

except they have a good picture of where it is. It forms spherical halos around galaxies and structures between and around galaxy clusters. We just don't know what it is.

Before I proceed, a little refresher course in scientific notation may be in order. Very large numbers and very small number can take up a lot of space if written in the normal manner using decimal places as you were taught in high school.

 

For example, the number of atoms in the Universe is 10 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 plus or minus a few. Well, you don’t want to be trying to say that nor writing that down every time the subject comes up, so a short-hand scheme is available using exponents. The same number can be shown as 1e79. Isn’t that a lot easier? (Perhaps Obama ought to start using scientific notation. His 16,000,000,000,000 debt could be expressed as 16e12. Isn’t that so much more pleasing?)

 

Now, we get to the heart of the matter.

 

Since the Big Bang, light has been emitted into the Universe. Every visible object we see is emitting or reflecting light. Let us concentrate our attention on stars since those generate the most light. Planets, meteorites and asteroids give off reflected light. Standing here on Earth we see stars as a small dots or spheres. But those stars are emitting light out in all directions creating a light sphere. Standing anywhere else in the Universe we would see the same stars as small dots or spheres.

 

The fact is, we cannot see light. We can see the source of light and we can see the objects from which light is reflected. Otherwise, when we look out into the Universe, we would see nothing but light. (Try this. Don a space suit, grab a flashlight and step outside the ISS (International Space Station). Now, aim the flashlight away from you and turn it on. You see nothing. Put your hand in front of the flashlight and you see your hand. Aim the flashlight toward you and you see the source.)

 

All those stars pumping light out into space. Some since the beginning of time, as we know it. And that light is still out there. We just don’t see it.

 

And what if that light had mass?

 

In fact, it does. Not a lot, but it does.

 

The rest mass of a single photon of light at a wavelength of 500nm is 4.417e-36 kg. That's 4.417 with 35 0s to the left of the 4 - a very small number.

 

The volume of the Universe is 2.058e79 cubic meters. That's 2.058 with 76 0s to the right of the 8 - a very large number.

 

So, how many photons would be required per cubic meter of the Universe if all the dark matter is really light?

 

The mass density of the Universe is 6.000e-27 kg per cubic meter. By dividing the mass density of the Universe by the mass of a photon, we get 1.358e9 photons per cubic meter - a very plausible number when you figure the mass density of photons near the Earth is 4.217e13 photons per cubic meter.

except the photon density in the Region of the Earth is vastly unrepresentative of the average universe density. Photon density falls off by the square of the distance from the source. This means that you only have to move 176 Au from the Sun for the photon density to drop to that 1.358e9 Photons/m^3. That's less than 3/1000 of a light year So basically, So even if you just work out the average density in the volume 2 light yrs in radius (a little less than halfway to the nearest star) you would end up with a much much smaller average than the needed 1.358e9 photons/m^3.

 

Another thing to consider is that the sun, (an average star in luminosity)outputs ~ 4e26 joules of energy per sec, which works out to 4.3e9 kg of matter. Now, even if the Sun had been producing light at that rate for 20 billion years, the total mass equivalence works out to 2.7e27 kg. The sun mass is 2e30 kg. This means that the mass equivalence of all that light produced by the sun over the age of the universe only works out to be a bit more than 1/1000 of the Sun's present mass. But we are looking for something that has more mass than the stars we see, not a tiny fraction of it.

So, I am going to go with that. Dark matter is really light. Now all I need to do is to convince a bunch of very bull headed and exclusive theorists of it. They don't like outsiders messing around in their area.

[swansont]

!

Moderator Note

 

Sunshaker's hijack has been split into a new thread

http://www.scienceforums.net/topic/85780-dark-matter-sunshaker-discussion-split/

 

[hoola]

It seems that dark matter is probably not light, but it may degenerate into light. I see dark matter as the overall effect of living in a finite multiverse situation, with gravity being a commonality, and "spread out" with the other extant universes...which explains why gravity is weak overall. I don't presume that there is a fully formed universe or set of universes out there, only that there was some left over information from the original description of our universe, and that may simply be "junk dna" that simply sits there lifeless, with an incomplete data set for full expression...but enough data to proscribe gravity function...