Ask any question you want about Physics

a reply to: ErosA433I have posted it a couple of pages back.

Arbitrageur

I think you misunderstand the question I was asking;

My contemplation doesn’t come from the “If a tree falls in the woods and no one is around to hear it …” stand point.

It is not a matter of perception creating realty.

It’s a question of whether our perception of realty is extremely limited and our interpretations flawed.


In my questioning, the cosmos exists whether or not there are any humans around to observe it. The question is does TIME as we know it exist or is TIME just a human construct?

Is TIME something we evolved into perceiving to make sense of an otherwise highly complex set of inputs. Just like most of our other senses/awareness there’s a lot more going on out there that we filter out than we let in, and we do a lot of internal shaping of what we do let in.


So on your picture there is a liner existence between Birth and White Dwarf. The Sun will exist in all 13 states depicted; we know this to be true and it would still be true if humans where not around to observer them.

And that’s fine; humans aren’t required.

What I am suggesting is that perhaps the Sun always exists in all 13 states across a cosmos that is laid out in a very different manner than what we normally perceive it to be.

If we had the means we could move between BIRTH and any of the other states just as readily as if we move from birth to state 1.

Somewhere, for some reason, humans (and other earthly creatures) have adapted to move (or perceive) in the direction that takes us from BIRTH to 1 more easily than in other directions; but that doesn’t mean the other directions don’t exist or that we aren’t interacting in those other directions while not knowing it.

a reply to: DanDanDat
Thanks for the clarification of your question. I'm always open to the idea that our knowledge might improve in the future, and I've argued that relativity is probably only correct in the limited case of some future broader theory the way Newtonian mechanics is correct in the limiting case of relativity, however I think general relativity is the best model of time we have at the moment.

One of the heretical notions of relativity (not heretical now, but when it was introduced) is the idea that time is not absolute, but rather the relative sequence of things depends on where an observer is located, or more specifically in which reference frame.

So in a narrower sense of your broad question, relativity does allow some of what you suggest on certain scales of time and space defined by the theory of general relativity. One of the interesting parts of general relativity is the prediction that if you could travel to just outside a black hole's event horizon and survive (the radiation would probably kill you if there was any matter falling in), you could conceivably watch the birth, life and death of a star like our sun, which for us takes billions of years, but for an observer orbiting just outside the event horizon might take only a few minutes or hours to observe.

So our understanding allows for great distortions of time, but I don't know of any model supported by evidence that would suggest "the Sun always exists in all 13 states across a cosmos that is laid out in a very different manner than what we normally perceive it to be." While I don't think relativity is the "ultimate model" and I'm not sure exactly what that ultimate model will look like, it's not my expectation that it will predict what you suggest with the sun existing in all 13 states, but I guess we won't know until we come up with a better model.

a reply to: Arbitrageur

Barbour's model of timelessness is supported by evidence. It is alternate cosmological theory but not on the crazy side of alternate.

In a profile in The Sunday Times (October, 1998), Steve Farrar wrote: "Barbour argues that we live in a universe which has neither past nor future. A strange new world in which we are alive and dead in the same instant. In this eternal present, our sense of the passage of time is nothing more than a giant cosmic illusion. 'There is nothing modest about my aspirations,' he said. 'This could herald a revolution in the way we perceive the world.'" Cosmologist Lee Smolin notes thatBarbour has presented "the most interesting and provocative new idea about time to be proposed in many years. If true, it will change the way we see reality. Barbour is one of the few people who is truly both a scientist and a philosopher."

edge.org...

originally posted by: DanDanDat
a reply to: Arbitrageur

Barbour's model of timelessness is supported by evidence. ...
edge.org...

It's interesting that you make that claim and then post a source which apparently contradicts it:

JB: Is there any way of testing your idea observationally?

BARBOUR: I cannot as yet see any direct experimental way of testing this particular idea.

At least I interpret that as a falsification of your claim. If I'm missing something here please let me know what. I tried to word my reply carefully such that I didn't reject Barbour's model nor some other alternate ideas about time. Saying that there's no direct experimental evidence to support it doesn't mean it's wrong. I would also say that about string theory...there's no direct evidence for it that I know of, but I can't say it's wrong, and it could have some validity.

Until such hypotheses have supporting experimental evidence, I try to remain somewhat open-minded and look for any experimental evidence which might either support, or falsify such ideas.

There's a thread on physicsforums about both Barbour's and Rovelli's alternate ideas about time if you're interested:

Julian Barbour on does time exist

a reply to: Arbitrageur

Time is difficult to discuss for one we know we need frames of reference. Even Einstein realized that past present and future have occured depending on your frame of refrence. Throw on many worlds interpretation and somewhere in the vast universe everything and anything has already occured. But I think the truly amazing thing people don't understand about space time is inertial frames. Depending on your perspective the universe can be moving or static. If you were outside the universe you would see no changes at all. The earth is spinning as we speak do we feel it? Of course not it spins around the sun again we have no frame of reference to compare it to. This is the argument for flat earthers. Or sun is is spinning around a galaxy that spins around a local cluster. The only true reference frame we have is distant galaxies from our view point they don't move. This is the only way we can detect all this movement. Since time is linked with space and velocity the bigger our frame of reference the less we see the effects of time.

If a God existed outside our universe he would not see any changes he wouldn't see anything but a static universe that never changes. There would be no past present of future because he would have nothing to compare it to. Without a frame of reference time doesn't exist. For example I have a ball in the middle of the universe it's the only thing in our universe. It's always been there and will always be there time is irrelevant because I can't even measure it. Add a second ball into our universe so now there is two but I still can't tell passage of time or even distance. Add a third ball now I can figure out distance of our balls but still unable to measure time. Time can only be calculated when I have a solid frame of reference to compare it to. In our universe it is those distant galaxies. Without them we have no spin we have no time. This is machs principle you only feel inertia and spin in reference to a larger initial frame. So yes I guess you could argue time is an illusion and indeed may have been created as a filtering mechanism for biological life. Could you imagine if we could sense everything in the universe at once?

Hi.

I own a 2004 Pontiac Aztek and it's front, driver's side door panel has been removed.

The problem is both the window guides have been broken so the window constantly falls all the way down whenever I drive over a bump.

What would be a creative and cheap idea to hold this window up until I can afford to have it fixed?

Thank you kindly in advance.

originally posted by: Steffer
Hi.

I own a 2004 Pontiac Aztek and it's front, driver's side door panel has been removed.

The problem is both the window guides have been broken so the window constantly falls all the way down whenever I drive over a bump.

What would be a creative and cheap idea to hold this window up until I can afford to have it fixed?

Thank you kindly in advance.

Duct tape I've seen entire cars made from the stuff. 😨

originally posted by: dragonridr

If a God existed outside our universe he would not see any changes he wouldn't see anything but a static universe that never changes. There would be no past present of future because he would have nothing to compare it to.

In that example it appears it would be true, solely due to the nature of light; for if light were to exit the universe and enter Gods eye, then he would see change. Because what you are really saying is 'when observing darkness, change cannot be observed'... or in other words; light is evidence of change.

Of course a blind man can experience proof that change occurs beyond his body, if for example a bird were to fly into him. But that is an example of 'object 'hitting into' detection apparatus', which is what the example of light represents as well.

So you are saying the obvious; 'without observing, no observation can be made'; 'while observing, there must be some physical interaction with our apparatus of observation, in order to declare that we have observed change, or anything'.

Without a frame of reference time doesn't exist.

I believe your statement would approach being the correct meaning you likely had intended, if you were to finish it by saying 'Without a frame of reference time cannot be measured well'.

When you say 'time doesnt exist' you are attempting to make an objective declaration of a statement. But just because you do not or cannot observe 'something' does not mean that something does not exist. (this gets back to the, is the moon there when I close my eyes... or when you play peek a boo with a baby and it closes its eyes do you seek to objectively exist.).

Because if an alarm clock exists in space and it is proven to be ticking away and it is known to have enough battery power to continue ticking and withstand space, and then everyone goes away from it, and then you in a sound proof space suit go towards it, until it is just you at a steady distance from the clock, and there is no other frame of reference in sight, and you cannot read or see the ticking of the clock (lets say you only have sight of its back end), just because you dont have a reference frame, would not make it proper to say 'time does not exist'.

originally posted by: dragonridr
The only true reference frame we have is distant galaxies from our view point they don't move. This is the only way we can detect all this movement.

What about the cosmic microwave background as a reference frame? Since galaxies mostly (all?) have redshift z under 10 and the CMB has redshift over 1000 it's observationally difficult to make precise measurements relative to the CMB but it's possible to do so in rough terms.

If a God existed outside our universe he would not see any changes he wouldn't see anything but a static universe that never changes. There would be no past present of future because he would have nothing to compare it to. Without a frame of reference time doesn't exist.

It's hard for me to say what god would observe, because presumably he operates outside natural laws and our models of reality depend on observations following natural laws. So I'm not sure what he would see, but I think the idea you're expressing is somewhat along the lines of Barbour's idea which as I said has neither been confirmed nor directly falsified as far as I know.

However, I'm not really fond of debating ideas which can never be resolved by experiment or observation because what's the point? To me it seems like spinning the tires on a car whose wheels are stuck in the mud. You see a lot of spinning going on, but you never go anywhere. See "Newton's flaming laser sword", alleged to be even more powerful than "Occam's razor".

Could you imagine if we could sense everything in the universe at once?

It's hard to imagine because of the bias we have from seeing time flow our entire lives. As far as "out of the box" thinking goes it seems pretty far outside the box, but relativity has already taught us that the notion that the sequence of events we observe is not necessarily the same sequence another observer will see, an idea which was also somewhat "outside the box" when it was introduced.

originally posted by: ImaFungi
In that example it appears it would be true, solely due to the nature of light; for if light were to exit the universe and enter Gods eye, then he would see change.

Without a model for saying what would happen outside our universe, we can't make predictions about what would happen to the light leaving the universe. This is why we refrain from trying to speculate about such an "edge" of the universe because even if such a thing exists, we really can't say anything useful about it with no model for what happens at or beyond the edge.

I have a question about Einsteins relativity:
Why do a bowling ball and feathers fall with the same speed in a vacuum on earth? And what has1,4 to do with it?
Does it mean the gravity is a myth?

originally posted by: Peeple
I have a question about Einsteins relativity:
Why do a bowling ball and feathers fall with the same speed in a vacuum on earth? And what has1,4 to do with it?
Does it mean the gravity is a myth?

Can you give an example with the 1,4? I do not recognize that figure in connection with freefall right away.

Can you give some context on how this is about Einsteinian relativity and not simple Newtonian mechanics?

a reply to: Pirvonen

Because this is apparently how he came to the conclusion of the space time curvature?
As i unterstand it with the gravity constant the heavier mass still should fall faster?
Forget 1,4 i was just hearing that during the experiment.
I found this
but it doesn't really explain where the gravity goes in the free fall in a vacuum on earth?

a reply to: Arbitrageur

Arbitrageur you are correct; I chose my words incorrectly and/or misunderstood your point. Like string theory; there are a lot of interesting thoughts but no concrete proof that this model is the correct one. Like string theory the theory does explain enough of the observerable world to make it worth thinking about.

a reply to: Steffer

Us a 2x4 cut to proper length; stick it into the holes used to remove the window guides and moter and prop up the window

originally posted by: Peeple
As i unterstand it with the gravity constant the heavier mass still should fall faster?

According to Newtonian mechanics, the "heavier" mass gets more force applied, but it takes more force to accelerate the heavier mass, which is why they end up accelerating at the same rate.

Newton's universal gravitation is in the form F=G*m1*m2/r^2
In that form m1 can be the Earth and m2 can be either the feather, bowling ball or whatever. So if m2 feather is replaced with m2 bowling ball 1000 times more massive, there's 1000 times more force. But the 1000 times more massive bowling ball takes 1000 times as much force to accelerate at the same rate.

Relativity calculations are more complex and not really needed to answer your question where relativistic effects are negligible, and I think you have some misunderstanding of the origin of Einstein's theory. In any case Einstein made sure his theory simplified to Newtonian mechanics in the limiting case because he knew Newton's model worked in most cases where relativistic effects were negligible as they are in the case of your question.

a reply to: DanDanDat
Thanks for the clarification.

a reply to: Arbitrageur

Thanks now that solved the knot in my brain!
🌻

a reply to: Peeple
You're welcome, glad it helped. Once upon a time I had the same mental knot, but sometimes those are good as we often remember what we learned to untie them.

a reply to: Peeple

Arbitrageur already got it But basically with a little bit of maths you can prove it, or at least predict it... then to see if it works you can measure it.

Newtons formulation comes to the Force between two objects due to gravity is
F=G m1m2/ r^2
Also from Newtonian Mechanics, we also can show that
F=ma

So all we do is set them equivalent
m2a = G m1m2/r^2

the mass term for m2 (the smaller object) is cancelled out leaving us with

a = Gm1/r^2

So this basically says regardless of the mass of the object in free fall (on the earth), it will accelerate at the same rate as defined by the Gravitational constant G, the mass of the Earth and the distance above the earth

Any difference in observed acceleration is thus supposed to be due to air resistance. The vacuum test, and performing this test on the moon, prove this prediction to be sound

Very simple but also counter intuitive until you try and add these different things together.

Another great one which is counter intuative is the following


A small car collides with a large truck... which has the higher force?

Hello =)


Could you explain this to me as if i were a retard?

phys.org...

www.abovetopsecret.com...

=)