Space time has mass? Spacetime and dark matter, one in the same?

a reply to: Arbitrageur

Again to my point; in order to understand this concept one would have to understand the differences between momentum and inertia. This is not addressed in the video. In the absence of this, one could conclude that momentum implies mass...which is not a correct assumption in this context.

And yes, a photon does have mass; it is not significant for most calculations, but it is not without mass...as in absolute zero.

originally posted by: chr0naut
Photons do have relativistic mass, expressed as momentum. They have zero rest mass.

Einstein says they don't have either type of mass. Richard Feynman made statements about relativistic mass, but Einstein said that's not a meaningful concept, and it's better to just refer to the momentum term in the correct equation if you're talking about momentum.

The problem was Feynman using E=mc² which is not the correct equation. I made a thread about this and provided Einstein's quote about using the correct equation instead here:

Science Quiz #2: Is E=mc² right or wrong?
Of course it's the wrong equation and it would have been better for Feynman to use the correct equation suggested by Einstein.

Mass in special relativity

originally posted by: Flyingclaydisk
And yes, a photon does have mass; it is not significant for most calculations, but it is not without mass...as in absolute zero.

Repeating that doesn't make it true, the mass according to the standard model is indeed zero so if a small photon mass is ever determined it will falsify the standard model, which will be kind of a big deal.

The Physics Hypertextbook

Photons are massless, uncharged, and have an unlimited range.

Not small, it's indeed zero according to the standard model. Now if you're arguing the standard model is wrong, you've got a huge uphill battle to prove that because it's supported by many observations.

a reply to: Arbitrageur

What time index does it say that? (Hint: it doesn't say that because that photons have gravitational attraction in spite of being massless was the whole point of the video, at least the part about gravity). The video specifically says photons have no mass at 30 seconds and he even writes down m=0 next to the light bulb, which means photon mass is zero. And at no point after that does he say photons have mass so I don't know how you can miss the major point of the video by so much.

Black holes gravity field is so dense light is held back, because of gravity. Okay, so theres that.

In the video at .48 seconds, a fraction of 1 with ten zeros in front of it.

a reply to: Flyingclaydisk

Sorry it devolved to that, the thread is about space time, not matter, or "matterless photons".

The argument boils down to the two camps, imo, the argument about wave vs. particle.
I see waves of particles in nature, I'd be a fool to think its any different with light.
Light is more energetic, less affected by gravity, but still affected in the presence of hi gravity sources.

Sorry about not agreeing with gravity not being generated by mass, thats just my own ignorant outlook, if that makes you happier.

originally posted by: Arbitrageur

originally posted by: chr0naut
Photons do have relativistic mass, expressed as momentum. They have zero rest mass.

Einstein says they don't have either type of mass. Richard Feynman made statements about relativistic mass, but Einstein said that's not a meaningful concept, and it's better to just refer to the momentum term in the correct equation if you're talking about momentum.

The problem was Feynman using E=mc² which is not the correct equation. I made a thread about this and provided Einstein's quote about using the correct equation instead here:

Science Quiz #2: Is E=mc² right or wrong?
Of course it's the wrong equation and it would have been better for Feynman to use the correct equation suggested by Einstein.

Mass in special relativity

originally posted by: Flyingclaydisk
And yes, a photon does have mass; it is not significant for most calculations, but it is not without mass...as in absolute zero.

Repeating that doesn't make it true, the mass according to the standard model is indeed zero so if a small photon mass is ever determined it will falsify the standard model, which will be kind of a big deal.

The Physics Hypertextbook

Photons are massless, uncharged, and have an unlimited range.

Not small, it's indeed zero according to the standard model. Now if you're arguing the standard model is wrong, you've got a huge uphill battle to prove that because it's supported by many observations.

The 'M' value in the equation you gave is the 'apparent' or 'relativistic' mass. The 'm' value being the rest mass.

I would agree with Einstein that the 'M' mass is only an apparent mass, a variable, and therefore not an 'actual' measure of 'real' mass.

That same equation (and E=mc^2) can also be rewritten as: E²=(mc²)²+(pc)²

The 'p' value being momentum.

This momentum appears to suggest a non zero mass but it isn't really an actual 'thing'.

So, I agree, but...

a reply to: chr0naut

Hence my earlier point, but whatever.

a reply to: DeadCat

Nice post and interesting questions you ask.
I'm just a layman who posts here occasionally with English my second language)). What a combination to post on physics threads, eh?

I think the answer to missing mass (hope that is what being discussed) is in our ability to detect celestial objects that are not easily 'visible', like brown dwarfs, for instance. There also could be a huge number of lone black holes wondering undetected. Who knows how much matter and when was consumed over 15 billion years into one of those?

I'd say huge number if you ask me. Black holes could have been a predominant event in early universe as newly formed matter (finite number) was more dense per cubic volume and more chaotic (hotter). Matter distribution was full of 'rejections' and 'collapses' (distributed unevenly). That would mean imo that in early universe large number of black holes were very probable. To detect and account for all of them now, since the telescope was invented is impossible. There must be pure luck to detect them via lensing effect or somehow else. And they merge too!







cheers)

isn't time non measurable in reality like the number 0? What does time have to do with anything?

a reply to: ssenerawa
Time is very important.
Without time everything would happen at once.

a reply to: Phage

Phage, I have to admit I choked on my coffee reading this one!!

Direct, yet profound!

Ensteins field equations show the curvature of space time (everything on the left) due mass (everything on the right.

Curvature of space time (precieved as gravity) is directly related (equal) to mass and energy.

Mass tells space time how to curve.
Curvature of space time tells the mass how to move.

Time is very important. Without time everything would happen at once.

a reply to: Phage

Or not at all, which sometimes happens....

Personally when we get to the heart of the matter (no pun intended)with the the big bang, and everything being born from nothing in the first place, well that I struggle with. I think Labtech might well be on to something with his blackhole/whitehole idea...
Who knows though eh? What is infinity anyway, if not something that is well and truly beyond our comprehension?

a reply to: DeadCat

Or to put it another way, space/time and mass both have an equal and opposite effect on each other.
Relatively speaking that is?

I don't know, but what I do know is you couldn't make this kinda stuff up, that which we call reality.

a reply to: surfer_soul

Could say that yes, but when you equate the "mass" of light, you will likly find that the gravitational affects of photonic mass are miniscule and irrelevant compared to that of the sun.

That is to say light doesn't curve space time significantly enough to precieve, only calculate.

If you use photonic mass 0 then you're saying light has no mass at all and is not bound to speace time by a pull. The reason it flows along space time is due to its miniscule mass. Otherwise light would travel straight, dispite space time curvature.

a reply to: DeadCat

But all particles are in fact wave, everything is oscillation that's where time comes in to play, without one, we wouldn't have the other.

a reply to: surfer_soul

If you think about it QM says that the particles move in waves.. until observed, in which case the waves turn to one particular position or state.

I don't think they literally move in waves.. the wave like behavior is in my opinion due to the infinite possibilities, until you measure it at a place and time from a relative perspective.

So that which is unmeasured, become only possibility.

originally posted by: surfer_soul
a reply to: DeadCat

Or to put it another way, space/time and mass both have an equal and opposite effect on each other.
Relatively speaking that is?

No, not equal and opposite, but of different nature.

Take the reduction of newton's Law: F=ma

The right hand side says how classical matter with mass moves (equivalent of left hand side in GR), and the left hand side is a placeholder "F" for other forces whose physics must be inserted. In General Relativity, the "F" term is made explicit.

originally posted by: DeadCat
a reply to: surfer_soul

Could say that yes, but when you equate the "mass" of light, you will likly find that the gravitational affects of photonic mass are miniscule and irrelevant compared to that of the sun.

That is to say light doesn't curve space time significantly enough to precieve, only calculate.

In general relativity, it is not necessary to have mass in order to be a source term (cause) of gravitation. The energy & momentum density of electromagnetic fields on their own can cause space-time curvature. However, experimentally, this effect is extraordinarily small, and I believe would have no observational consequences outside perhaps Big Bang cosmology calculations.

originally posted by: DeadCat
a reply to: surfer_soul

I don't think they literally move in waves.. the wave like behavior is in my opinion due to the infinite possibilities, until you measure it at a place and time from a relative perspective.
.

That's it, everything is relative to everything else, depending from what position you observe it, you will find different results due to space/time... As far as waves go, think of something spinning, oscillating, . it's not a literal wave, but is measured just the same. Everything, all matter is vibrating or oscillating to some degree or another in order to maintain it's own space, relative to everything else.

Thus we have "the harmony of the spheres"

a reply to: surfer_soul

That's it, everything is relative to everything else, depending from what position you observe it, you will find different results due to space/time

No. The speed of light is not relative. Something which makes electromagnetic radiation quite unique.