Ask any question you want about Physics

Get off your high horse mate. When I need a lesson on posting, i'll ask for it. Verstanden!!
a reply to: ErosA433

originally posted by: Phantom423
Question: Does Einstein's equation e = mc2 apply to dark energy? If it does, can dark energy transform into mass? Are dark energy systems adiabatic i.e. they don't transfer or gain energy? If dark energy obeys the first law of thermodynamics, shouldn't there be some type of barrier between dark energy and rest of the universe?

I think I need to clarify something for you. Mass is just a form of energy. You don't change energy into mass it is already energy. Now to answer your question we don't know it's possible for dark matter to be a form of energy we haven't observed. The reason we use the term matter is because we see its effects on gravity. As far as dark energy forming into dark matter they could be one in the same if it was a scalar field for example. the reason it would be a field is it has magnitude, energy and pressure, but it is scalar so it has no direction.

Bottom line is we don't know we see its effects but as yet don't know what causes it. This will be a Nobel prize when someone figures it out. As far as the barrier between we don't see one and and its weak interaction with normal matter wouldn't need one.

originally posted by: dragonridr

originally posted by: Phantom423
Question: Does Einstein's equation e = mc2 apply to dark energy? If it does, can dark energy transform into mass? Are dark energy systems adiabatic i.e. they don't transfer or gain energy? If dark energy obeys the first law of thermodynamics, shouldn't there be some type of barrier between dark energy and rest of the universe?

I think I need to clarify something for you. Mass is just a form of energy. You don't change energy into mass it is already energy. Now to answer your question we don't know it's possible for dark matter to be a form of energy we haven't observed. The reason we use the term matter is because we see its effects on gravity. As far as dark energy forming into dark matter they could be one in the same if it was a scalar field for example. the reason it would be a field is it has magnitude, energy and pressure, but it is scalar so it has no direction.

Bottom line is we don't know we see its effects but as yet don't know what causes it. This will be a Nobel prize when someone figures it out. As far as the barrier between we don't see one and and its weak interaction with normal matter wouldn't need one.

Thanks for the reply. Why wouldn't dark energy be a vector? It pushes outward, creating space and expanding the universe. If it was scalar, it would only have magnitude. Why isn't the push outward considered direction? Isn't it like the arrow of time - moves only in one direction and isn't reversible?





My understanding of dark matter is that it is entirely different than dark energy i.e. it's the gravitational pressure that holds galaxies together and is probably a particle that hasn't been identified as yet.

One more thing - the latest figures from NASA show that the content of dark energy is 68.3% of the universe. That's exactly 1 standard deviation from the mean in a Gaussian distribution. Probably doesn't mean anything, but just noticed it when I read this article from NASA.

www.nasa.gov...

The nature of the gaussian gives a probability of 0.683 of being within one standard deviation of the mean.

originally posted by: dragonridr
a reply to: Arbitrageur
I was thinking about it off shore on beaches is a cross current shouldn't be much different than a stream.

I'm not sure what you mean by a cross current.

There are rip currents leading away from shore and there are small cross-currents feeding into the rip currents but both types are unstable and move around so wouldn't be suitable locations for such a pump.

There's undertow but that would pick up a lot of sand or sediment near the beach.

Maybe tidal currents would work but they reverse direction as the tide changes, though I suppose you could set up pumps in both directions so if one isn't working the other one is. The problem there is tidal currents are very strong in some places and almost non-existent in others.

The only consistent cross-currents I can think of are currents like the gulf stream, is that what you had in mind?

I'm a scuba diver and have been tossed around by many types of currents so I have some intimate knowlege of some of them from being at their mercy, including some amazingly strong tidal currents.

originally posted by: Phantom423
Why isn't the push outward considered direction?

If it's pushing outward in all directions that's no direction in particular, right?

originally posted by: Phantom423
One more thing - the latest figures from NASA show that the content of dark energy is 68.3% of the universe. That's exactly 1 standard deviation from the mean in a Gaussian distribution. Probably doesn't mean anything

Correct, it doesn't mean anything.

The moon is able to eclipse the sun since they subtend about the same angle in the sky, but that also doesn't mean anything except coincidences happen.

a reply to: Arbitrageur

If it's pushing outward in all directions that's no direction in particular, right?

If it's pushing in all directions equally why isn't the net effect zero? If dark energy creates space then wouldn't it have to occupy that space equally in all directions as the space is being created? If the amount of dark energy is fixed and it is scalar, why does it expand the universe?

a reply to: Phantom423
When you blow up a balloon, the balloon expands in all directions, right? The center of the balloon doesn't move much but the increased volume of air pushes the balloon out in all directions. There's no particular direction of the expansion, but the net effect is not zero. It takes up more space as you blow it up.

I don't think the amount of dark energy is fixed. We aren't sure but we think dark energy and vacuum energy might be related, and if that's true, as more space is created, so then is more dark energy if it's the vacuum energy of space in our universe as we suspect but haven't proven.

hubblesite.org...

We do know this: Since space is everywhere, this dark energy force is everywhere, and its effects increase as space expands.

originally posted by: Nochzwei
Lol, are you blind

No, I saw the washing machine with lights on it. And a bunch of objects that can be manipulated in any number of ways.
There was no anti-gravity. When someone cancels gravity "completely", like he states, then one should show a vacuum state where mass is free floating.


It's a silly video. If it makes you happy then run with it. Enlighten everyone. I'm ok with being in the dark on that one.

originally posted by: Nochzwei
for levitation, you will need to stop time completely and at this point the antigravity machine is no longer a part of this universe. so it will disappear and what happens to the space occupied by the machine? It may collapse in on itself and result will be goodbye planet earth and you and me oblivion.

What? Why would you need to stop time? What are you talking about?
He said he completely cancelled gravity. So in the area where it's cancelled things will float.

Photons experience zero time, space does not collapse?

If one were to Assign the earth 0 motion and spin could not the rest of physics be expressed as the universe revolving around the earth?

originally posted by: joelr

originally posted by: Nochzwei
for levitation, you will need to stop time completely and at this point the antigravity machine is no longer a part of this universe. so it will disappear and what happens to the space occupied by the machine? It may collapse in on itself and result will be goodbye planet earth and you and me oblivion.

What? Why would you need to stop time? What are you talking about?
He said he completely cancelled gravity. So in the area where it's cancelled things will float.

Photons experience zero time, space does not collapse?

You need to stop time to completely negate gravity. He does not say he completely cancelled it in the time machine has run. He is showing anti gravity signatures. Watch it again carefully'
Everything that is a part of this universe experiences time. Space can collapse but pray that it doesn't, so that earth and all on it goes into oblivion. Looks like you are still schooling.






h

originally posted by: dashen
If one were to Assign the earth 0 motion and spin could not the rest of physics be expressed as the universe revolving around the earth?

Thanks for the question. According to polls in the US and UK, from 18-25% of people think the sun revolves around the Earth, so this type of idea or belief is shockingly widespread. No matter how many times I hear that figure I can't get over it.

Because the belief is so widespread, I made a separate thread on this topic, please refer to that thread for the answer:

Does the Sun Revolve around the Earth, or does the Earth revolve around the sun?

a reply to: Nochzwei

No high horse at all, in my oppinion the high horsed poster here can be found by looking in the mirror. One who believes the Nobel prize committee need

drumming

Also who still speaks of a time machine and anti-gravity machine that has had a wealth of real science explanations basically ignored due to a need to maintain ones own confirmation bias...

Box with 80% closed sides makes a loud noise does not equal anti-gravity or time dilation because a dial deflects and a scales changes... The purple fringes are 100% caused by a well known CCD artefact... but... no wont be accepted... why exactly? please explain, since we have offered about 50x more detailed explainations of things than you have ever, yet you always just appear to make grand statements with little/no backup.

I received some questions from an anonymous source which I'll try to answer, feel free to add to the answers if I missed anything.

Q: Does the universe have an edge?

A: We don't know, it may or may not. The universe might be finite or infinite, and in the latter case it wouldn't have an edge.

Even if it's finite it still might not have an edge, if for example the geometry of the universe is curved a certain way. For example, you can fly in one direction around the earth and never find any edge of the Earth and you'll end up back where you started. One possible model of the universe similarly posits you could travel in one direction and you might end up back where you started, if space itself has a small curvature. So far we haven't measured such curvature and it seems flat but as Michio Kaku pointed out an ant walking on the surface of a hot air balloon thinks the balloon looks flat...the curvature is too big for the ant to see. By extension he implies maybe the curvature of the universe is too big for us to see.


Q: Is it possible the universe will collapse at some point?

A: Before 1998 this was considered entirely possible. Since 1998 when we discovered dark energy and the accelerating expansion of the universe, it seems unlikely, though there are a few ideas which might still permit it. The more prevalent thinking is that if the expansion continues to accelerate, it won't have a chance to collapse.

What is the Ultimate Fate of the Universe?

Prior to 1998 the orange line at the bottom of that graph which shows a collapsing universe (or some similar collapsing curve) was considered a very real possibility. But in 1998 new observations which showed expansion of the universe was accelerating suggest the expansion curve is more like the red line on the top, so now it doesn't seem very likely that we'll see any collapse.

Whether it collapses or not also depends on the "shape" of the universe so both these questions are related:

There is a growing consensus among cosmologists that the total density of matter is equal to the critical density, so that the universe is spatially flat. Approximately 24% of this is in the form of a low pressure matter, most of which is thought to be “non-baryonic” dark matter, while the remaining 71% is thought to be in the form of a negative pressure “dark energy”, like the cosmological constant. If this is true, then dark energy is the major driving force behind the fate of the universe and it will expand forever exponentially.

Measurements from WMAP

The WMAP satellite measures the basic parameters of the Big Bang theory including the fate of the universe. The results suggest the geometry of the universe is flat and will expand forever. Further study of the dark energy with future experiments and space missions is needed to understand its nature and effect on the rate of future expansion.

So there are some "ifs" and caveats in there, and I suppose we can't completely rule out a collapse based on new evidence, but based on presently available evidence and models, a collapse seems unlikely. We are probably on an expansion curve like the red curve, not the orange one.

Q: Have you got a good link about vacuum energy?

A: This is one of the best links I've found, though if anybody has better links I'd like to see them:

What's the Energy Density of the Vacuum?

Hi all,

Very relaxing Friday evening, by the way, happy Thank giving to all Canadian folks!!


May be on this day, you SR, GR, QM, BB nerds you would take a step away from your formulas to look at falling tree leaves, heavy beautiful clouds coming with north winds.
Your vibes will place you right where you belong. Your inner beast will crawl into comfort zone akin when you were a child wondering as to 'did I know this place before'.


cheers)

originally posted by: Arbitrageur

Even if it's finite it still might not have an edge, if for example the geometry of the universe is curved a certain way. For example, you can fly in one direction around the earth and never find any edge of the Earth and you'll end up back where you started.

Another fine example of 2d thinking blinding your comprehension.

In your example of the earth, never finding an edge...

You would always be on the edge, compared to the center of the earth.

The first and foremost way in which the universe would not have a hardcore defined edge, would be like if you had 10 bowling balls floating in 0 gravity space, and asked to define the edge of the collection.

If the universe is generally, a collection of galaxies, (bowling balls generally representing such), and 'nothing space' did exist between the galaxies or even if it does not, in this sense it may be difficult to find a hard defined edge.

However... if theory is that 'everywhere in the universe gravity is able to occur',

And gravity is able to occur be cause a substance/material exists everywhere in the universe which is able to be warped;

The edge of the universe would be the extent of that substance/material...but really just the extent of all substance and material;

You must in theory, be able to go beyond in any and every direction the totality of energy/matter...

We do not know the meaning of nothing...

But either way there must be 'a' beyond (beyond in terms of distance, in area) the totality of energy/matter.

originally posted by: Arbitrageur

Even if it's finite it still might not have an edge, if for example the geometry of the universe is curved a certain way. For example, you can fly in one direction around the earth and never find any edge of the Earth and you'll end up back where you started.

-------------------------

Hi,

Does it mean space expansion has no direction and no form?

Then why space assumed to expand spherically or any other shape?

Cosmos shape might be irrelevant if time somehow connected to space. I mean what if new (expanded) space is arbitrary? New volume is being created where it needs to, on demand, where physical events, like chemical bindings (event in time) needs it to?
Sort of 'for chemical reaction, it needs time "room' to execute. Pushing space of cosmos overall lager?


Not sure I put my thought comprehendible.


cheers)

to further explain my point

you move your elbow while reaching for a book on the shelf, you elbow creates new space for itself to move into.

chicken and egg solution LOL))

drumming = joke
e = mc2 gives sqrt m directly proportional to time t. hence time dilation = less mass /wt implies anti gravity
so dial deflects and scale changes = anti gravity
Purple band may not be entirely ccd artifact but something weird /radiation going on due to time dilation
a reply to: ErosA433

originally posted by: ImaFungi
Another fine example of 2d thinking blinding your comprehension.

In your example of the earth, never finding an edge...

You would always be on the edge, compared to the center of the earth.

The Earth's surface is a 2D analogy for 3D space. Do you deny that if you travel in one direction in a plane you can end up back where you started? Any analogy is imperfect and yes the Earth has a center but we don't think the universe does, but most people don't consider 3D curved space in their every day thought so the Earth surface analogy might help. Anyway since no curvature has been measured I wouldn't worry about the curvature too much though Dr. Kaku insists that failure to observe curvature doesn't rule out a curvature so small it's beyond observational limits and it's hard to argue with that.

originally posted by: greenreflections
Does it mean space expansion has no direction and no form?

Then why space assumed to expand spherically or any other shape?

The metric expansion of space is in all directions. The discussion about the shape was that the universe may have a particular type of geometry, not that expansion occurs in such geometry. In other words, whatever geometry the universe has, if it expands that geometry will get bigger unless the expansion or some other factor changes the geometry. Here are three possible shapes for the geometry of the universe, with our measurements pointing to the flat and possibly infinite universe geometry, though this is far from certain:

Shape of the universe

The local geometry of the universe is determined by whether the density parameter Ω is greater than, less than, or equal to 1.
From top to bottom: a spherical universe with Ω > 1, a hyperbolic universe with Ω < 1, and a flat universe with Ω = 1. Note that these depictions of two-dimensional surfaces are merely easily visualizable analogs to the 3-dimensional structure of (local) space.

An analogy often used is that galaxies are like the raisins in raisin bread that are separating as the dough expands. All the raisins are moving away from our raisin and the other raisins are also moving away from each other in this analogy. We can't see anything like an edge of the loaf so we aren't sure what the configuration of the universe is beyond our perception, so we can only make educated guesses about that.