warping of spacetime

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this seems to be a widely accepted concept but it does not make sense to me. i want to understand all the information regarding it so that i can understand it better to make a judgement.

this is the only evidence i am aware of:

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Since light has no mass, it is not subject to Newton's law of gravity, and hence, in Newtonian physics gravity has no effect on light. If space is curved, however, it follows that a ray of light seemingly moving in a straight line, really travels in a curved line following the curvature of space. This is comparable, in some way, to the itinerary of a plane. Because the earth is a sphere, the shortest path between two points on earth is described by a geodesic, a curved line. While moving along the geodesic it would appear to the passengers of the plane that they are moving in a straight line, although they are not. Similarly, the light of distant stars travels through the curved geometry of space before it reaches Earth. This thesis is supported by observation.

When the light of a star passes close to the Sun, it is deflected by the Sun's gravitational field, which causes it to appear slightly displaced. The star appears to be farther from the Sun than it ought to be. The displacement has been measured by photographing the apparent position of stars during a solar eclipse and comparing these positions with those observed in the night some time later. Apparent shifts of less than 2 seconds per arc have been measured this way, in close agreement with the theoretical predictions of General Relativity. Likewise, the mentioned deviation in the orbit of Mercury when the planet reaches its perihelion (=closest position to the Sun), which is in contradiction with the laws of Newton, can be explained with Einstein's model of curved space.

now, assuming that photons have no mass...i do not see how it can be assumed that just because space warps, time also warps.

but on a more basic level, how can we say photons have no mass?

it seems that anything with energy must also have mass. it also seems that we have evidence of photons mass...we know white reflects light and black absorbs it, and if we put this on a spinner it will spin when the light shines on it.

i found this article explaining why photons do not have mass:

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http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html

but i do not understand the rationale behind the new equation...i was certainly taught the "outdated" one...

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If photons had any rest mass then when they hit you going at the speed of light they would appear to have infinite energy and mass from your point of view. That would hurt. Very Happy

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stuh

High Energy Colliders like CERN show time warps very, very clearly! Many collisions create very specific ultra short lived particles (e.g. muons or pions http://www.physlink.com/Education/AskExperts/ae611.cfm ). Some can only exist for millionths of a second at rest before they decay to more stable particles. But accelerate them close to the speed of light (99.999954% of the speed of light at 980 GeV http://www.fnal.gov/pub/inquiring/questions/speedopart.html) and time slows for them - allowing them to exist in our frame of reference for alot longer and therefore travel alot longer before they decay. All very precisely in agreement with the exact results Einstein and relativity predicts.

From the above link

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Pion experiments at CERN have measured time dilation effects. Pions are produced in high energy collisions of nucleons. They are unstable and decay into a muon and a neutrino.

Not taking into account time dilation pions would travel about 7.6 meters before decaying.

Taking into account time dilation a pion of energy 4.5 GeV would travel about 250 meters before decaying.

CERN has measured a mean distance of 250 meters before the pions decay

Photons may have no rest mass because they don't react to gauge bosons / Higgs bosons / gravitions. http://www.fnal.gov/pub/inquiring/questions/higgs_boson.html

Photons do have momentum.

E = mc^2 is the dumbed down approximation of Einstein's true law:

E^2 = p^2c^2 + (m0c^2)^2 where p is momentum, from http://physics.berea.edu/~king/Teaching/ModPhys/Relativity/relativity2.htm

Space tells energy and matter how to move and matter or energy tells space how to warp!

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High Energy Colliders like CERN show time warps very, very clearly! Many collisions create very specific ultra short lived particles (e.g. muons or pions http://www.physlink.com/Education/AskExperts/ae611.cfm ). Some can only exist for millionths of a second at rest before they decay to more stable particles. But accelerate them close to the speed of light (99.999954% of the speed of light at 980 GeV http://www.fnal.gov/pub/inquiring/questions/speedopart.html) and time slows for them - allowing them to exist in our frame of reference for alot longer and therefore travel alot longer before they decay. All very precisely in agreement with the exact results Einstein and relativity predicts.

hey you're talking about relativity which I am not debating, im talking about the warping of spacetime around supermassive objects thats another thing entirely

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Photons do have momentum.

but p=mv! so if they have momentum their m != 0...?

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If photons had any rest mass then when they hit you going at the speed of light they would appear to have infinite energy and mass from your point of view. That would hurt.

how do you figure? if I assume that photons have a mass of 1x10^(-20) kg, then a photon would have 4.5x10^(-4) J of KE. this is not infinite in fact its very small....

I dont understand why if photons seem to have all the characteristics of something with mass (1. energy, 2. affected by gravity, 3. can do work) then how come we are tryingto make up complicated exceptions to describe all these reasons instead of just saying, "ok yeah they havea tiny bit of mass" ?

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Perhaps if you studied the physics that mankind has painstakingly spent centuries developing, the reasons for these things would become clearer. You are commenting on General Relativity and Quantum Electrodynamics. Do you have the necessary background to know why the theories say what they do?

There is a difference between reading popular science descriptions and actually studying the physics. Having personally never studies much biology or chemistry, and no medicine at all beyone what one reads in the papers, I would not attempt to critique techniques of brain surgery.

For what it's worth, the formula p = mv does not apply to photons.

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because nothing with mass can travel the speed of light. As one gets closer and closer to that speed, .... you know the drill. So we need an explination that allows us to draw a line between what can and cannot travel at these speeds. If we admit that photons do have mass then the equation no longer works. But maybe the equation never worked to begin with? Stephen Hawkins takes an interesting approach to this subject in his book A Brief History of Time.

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This message is for Brandon 9000.
I find you all over this site critiquing people about thier questions and quite frankly it is making me sick. No we do not all have a masters degrees in Physics, but that does not stop us from thinking about it. This man has a question, and a very good one at that. If you think his question is out of his rhelm of thinking, then why do you not just proclaim that the world is flat and kill anyone that thinks otherwise. To assume that everything that we have discovered thus far about physics is absolutely correct will only prevent us from developing further in this field. So I beg you to please stop discouraging us from what we love. If you come across a question that just makes you want to flex your brain in front of everyone so that you can reassure yourself that you are the one and only physicist with superior knowledge on all subjects, why don't you try explaining these concepts that we have studied for hundreds of years. Don't be a person that slows progress, we get places faster by a free exchange of ideas.
By the way your brain surgery analogy was lame when you used it on me, and guess what, its still lame. COME UP WITH SOME NEW MATERIAL.

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As an object with mass gets closer to the speed of light it appears to outside observers to increase in mass and needs more energy to increase its velocity.

To an outside observers point of view something with mass travelling at the speed of light would appear to have infinite mass and would need infinite energy to get to that velocity. From its own point of view though nothing would've changed.

Now because turning on a light bulb doesn't smash you flat against the floor and have the power company charge you infinite dollars for your power bill photons have no rest mass. Very Happy

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Stuh505 said "hey you're talking about relativity which I am not debating, im talking about the warping of spacetime around supermassive objects thats another thing entirely "

E = mc^2, so supermassive things and super energetic things are the same and produce equivalent effects. A supercollider clearly shows the warping of time around super energetic which is equivalent to super massive things. The warping of time and space IS relativity - so yes you are talking about it!

Your general formulea for momentum only holds true for particles with genuine rest mass (leptons and quarks) not bosons (force carriers).

* * *

Think of things this way. Everything exists in a media of very small things. Once you get down to the size of these very small things strange effects can happen at a small localised level. Concerntrate enough of these important small things into very small area and very, very strange happenings occur, like curving spacetime and dilating time flow.

Think of force carriers like a vibration in the media itself - not an extra part of the media. So it can do some special things - like travel fast and appear to be either a wave or a particle, do have momentum but not rest mass, to be bent with gravity because gravity curves the media itself. But it does not have all the characteristics of the media, it is a wave travelling through the media.

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As an object with mass gets closer to the speed of light it appears to outside observers to increase in mass and needs more energy to increase its velocity.

what equation shows that mass is a function of velocity?

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E = mc^2, so supermassive things and super energetic things are the same and produce equivalent effects.

but you're trying to convince me that mass and energy are not interchangeable, how can you use the counter to your proof as evidence for it!

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A supercollider clearly shows the warping of time around super energetic which is equivalent to super massive things. The warping of time and space IS relativity - so yes you are talking about it!

please, i am trying to understand what evidence we have for spacetime bending....i dont want to hear someone elses results, i want to hear what data led them to those results so that i can understand why they think those are the results...

anyway, the whole explanation of spacetime warping around supermassive objects to describe why light bends around them doesn't seem to work...because if spacetime were bent, causing light and matter to bend with it, then all our means to detect the bending light would bend with it and it would appear to be moving straight. you see the dilemma?

also will you please address the last question in my previous post?

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Stuh505

what equation shows that mass is a function of velocity? From relativity

Mass in motion = rest mass / sqrt( 1 - v^2 / c^2)

you're trying to convince me that mass and energy are not interchangeable...

But you're confusing rest mass with mass in motion. From relativity - mass in motion at super high speeds creates the same effects as super heavy rest mass or energy. And remember I am talking about super colliders firing super fast charged particles (not massless photons) generally into gold atoms. The link below gives an excellent explanation and JAVA spreadsheet to see relativity in action.

If you want "the data" look up Einstein's thought experiments about relativity - they are pretty well documented.

"if spacetime were bent, causing light and matter to bend with it, then all our means to detect the bending light would bend with it and it would appear to be moving straight"...

Only in a local, static environment. Stand on Earth and study the position of a far star whose direct line of sight is approaching the Sun. This is easiest to do during a total eclipse. As the Star gets close to the edge of our Sun its position suddenly shifts as its light experiences the Sun's curving spacetime in its vicinity. This is pretty clear proof of supermassive objects curving spacetime.

"I dont understand why if photons seem to have all the characteristics of something with mass (1. energy, 2. affected by gravity, 3. can do work) then how come we are trying to make up complicated exceptions to describe all these reasons instead of just saying, "ok yeah they have a tiny bit of mass""

Because they don't! They can be made to exhibit surface level tendencies of other particles, but they can change their characteristics based on the frame of reference or the experiment. This shows they are more complex so have to be something that is a superset of other things.

Suggested readings for you:

Elementary particles http://particleadventure.org/particleadventure/frameless/chart_print.html

especially http://particleadventure.org/particleadventure/frameless/chart_cutouts/particle_chart.jpg

and Relativistic energy and rest mass

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/releng.html

Particle Physics in the 21st Century

http://www.sciencemaster.com/jump/physical/fermi_04.php

and The fireworks of elementary particles

http://pdg.lbl.gov/fireworks/intro_eng.swf

Other excellent sources

http://www.google.com.au/search?q=cache:NcEVx4WQYdAJ:www-atlas.lbl.gov/QuarkNet/Workshop2002/Standard_Model_Ian.ppt+do+quarks+exert+gravity&hl=en&ie=UTF-8

http://www.astronomycafe.net/qadir/acosmbb.html

http://online.itp.ucsb.edu/online/colloq/

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Stuh

In the words of Albert himself ...

"Reality is merely an illusion, albeit a very persistent one."

The answer to your question is that "warping" simply makes for a "more elegant explanatory model" just like a heliocentic system is "more elegant" than a geocentric one... and for most of the world where "meaning" still lies in "sunrise" and "sunset" they can rightly say "so what !" to heliocentism.

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Hopefully he's off reading those links - they are quite good and informative on his subject matter.

With luck the next post will be by someone who took the effort and now understands the framework better than most.

BTW - if able2know can't help you - in really high end maths, science etc - try the advanced physics forums at:

http://www.advancedphysics.org/index.php

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mmattin1 wrote:

This message is for Brandon 9000.
I find you all over this site critiquing people about thier questions and quite frankly it is making me sick. No we do not all have a masters degrees in Physics, but that does not stop us from thinking about it. This man has a question, and a very good one at that. If you think his question is out of his rhelm of thinking, then why do you not just proclaim that the world is flat and kill anyone that thinks otherwise. To assume that everything that we have discovered thus far about physics is absolutely correct will only prevent us from developing further in this field. So I beg you to please stop discouraging us from what we love. If you come across a question that just makes you want to flex your brain in front of everyone so that you can reassure yourself that you are the one and only physicist with superior knowledge on all subjects, why don't you try explaining these concepts that we have studied for hundreds of years. Don't be a person that slows progress, we get places faster by a free exchange of ideas.
By the way your brain surgery analogy was lame when you used it on me, and guess what, its still lame. COME UP WITH SOME NEW MATERIAL.

Anyone has the right to post anything here that he wants, but that includes me. I don't object to people wanting to learn about various fields of study, since I myself want to learn many things that I don't now know. However, I would not be likely to challenge the experts in a given field without first studying it.

There appears sometimes to be no understanding here that deriding the opinions of scientists is not very reasonable without first studying the topic in question, especially in areas with a long history of development by a large number of scientists. Contrary to what you have said, most progress in the various scientific disciplines has not come from people who have no knowledge of them.

I sometimes challenge the content of what people say in these threads, but I do not often reduce the level of the discussions by making negative references to them personally, as you have done. You may turn this entire thread into a harangue about me, if you like, but I will not reply on this matter further, nor will I change my habits one iota.

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Brandon

If you look at the philosophy threads you will find that words like "progress" "experts" and "knowledge" are up for grabs. Okay this question is not in that section but that does not detract from the validity of philosophical issues surrounding this question, some of which issue from the so called "experts" themselves.

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fresco wrote:

Brandon

If you look at the philosophy threads you will find that words like "progress" "experts" and "knowledge" are up for grabs. Okay this question is not in that section but that does not detract from the validity of philosophical issues surrounding this question, some of which issue from the so called "experts" themselves.

Hello. The problem is, though, that this is not philosophy. Nor is it art criticism.

In the hard sciences, like chemistry, physics, etc., it really doesn't make a lot of sense to say that the accepted theory is wrong without first learning some of it, and why it says what it does.

I have no problem with posts which say, "Why do the experts say this? It doesn't seem to make sense to me. Please explain." On the other hand, posts which seem to actually deride areas of scientific theory of which the author clearly has no comprehension, are kind of annoying. It is not the challenging of the theory which I question, but the challenging of the theory without first learning the basics of the topic. If a poster wants to positively declare that accepted scientific theory is wrong, I do not ask that he be a professional in the field or have any formal qualifications, only that he seem to have some familiarity with the theory he is declaring wrong. Just as the person who started this thread had a perfect right to do so, I have a perfect right to weigh in with my ideas.

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I always enjoy it when someone does the hard yards to improve their understanding of science, ask good questions, find good resources and be willing to learn.

Time dilation isn't really easy to comprehend deeply. It really calls on a detailed understanding of frames of reference, and how our universe affects differing frames of reference relatative to one another.

Understanding time slows at high speed or near a massive body - from the relative perspective of a external observer who is stationary and removed from major gravity sources is challenging. There are many hard parts to understanding relativity, none the least:

1) Time almost stops near the event horizon of a black hole

2) Inside a black hole space and time almost take on each other's characteristics according to some theoretical models that go beyond relativity

3) Relativity can't handle circumstances of ultra high gravity (inside the event horizons of black holes or cosmic strings) or faster than light speeds (e.g. tachyons)

4) Time in relativity is never an absolute - to anyone - ever! Its always relative meaning its different across any different frames of reference - not because we can't measure it accurately - but because time itself is relative!

Having spent many an evening browsing the web on google searching about high energy physics, sub atomic particles, quantum gravity and astronomy - let me simply say there are alot of great website out there and its fun to learn.

I just wish they taught me in high school more about the structure of the atom. Back then it stoped at electron, proton and neutron. It my mother's day it was taught it was impossible to split an atom because you couldn't manufacture a knife sharp enough Smile

I used to play frisbee at Uni with the guys who pioneered discovery of Quarks - and more than half the team thought the idea was daft at the time.

Ideas change over time and generally get more detailed. We now have many hundreds of sub atomic particles, excellent measurement of the physical constants
http://newton.ex.ac.uk/research/semiconductors/theory/collabs/constants.html

and the tools to do really cutting edge high energy research. Added to this alot of theoretical physics is on teh web - easy to get too, sometimes surreal to comprehend. But Hawking's "The Universe in a Nutshell" is a great starting place. Added to this we have string and m-theories (described as 22nd century physics that fell into the 21st century).

Go forth and learn with humility and an avid thirst for knowledge is my encouragement to you!

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They proved time dilation on a plane using atmoic clocks.

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Hopefully he's off reading those links - they are quite good and informative on his subject matter.

yup...wish i could say i had read them already, but kind of busy lately..will get around to it, though. usually i come to this forum for only a few minutes at a time so its hard when i have to do a lot of research between posts!

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1) Time almost stops near the event horizon of a black hole

general relativity just because its movign fast time slows down right or is there another concept here

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2) Inside a black hole space and time almost take on each other's characteristics according to some theoretical models that go beyond relativity

no mental image of this one...i gotta say thuogh, just because some model predicts it isnt enough to prove it...a lot of times we think we have something modelled accurately but at high orders of magnitude gigantic errors become evident which is why i am skeptical of certain claims like this

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3) Relativity can't handle circumstances of ultra high gravity (inside the event horizons of black holes or cosmic strings) or faster than light speeds (e.g. tachyons)

what do you mean by 'cant handle'?

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4) Time in relativity is never an absolute - to anyone - ever! Its always relative meaning its different across any different frames of reference - not because we can't measure it accurately - but because time itself is relative!

eh...but the unrelative "overrall" time we humans usually think of could be said to just be time relative to a stationary point in space. this is how i think of it at least. relative to a stationary object, everythign else moves at various speeds through time...but they could still all be put on a chronological stack of what happened in what order from this perspective.

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Hawking's "The Universe in a Nutshell" is a great starting place.

yup, but it tells the theories but doesnt say why the theories exist...which IMO is more useful than the actual theories which are subject to change as more information is learned. this book is the reason why im posting here...trying to get at the WHY of the theories not jsut the WHAT.

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