Thread: Dumb Questions VII

Sorry about my lack of knowledge here and thanks to the membership for at least being tolerant of it.

This one has always bothered me. If a galaxy is constantly gaining mass then could it also constantly affect the Doppler effect? Would not a larger mass have more of an effect on light waves then one of lesser mass? I'm thinking that an ever increasing mass would constantly stretch light waves. If this is so then is the expansion of the universe, the stretching of space, merely a result of mass increases of the heavenly bodies? Is there an actual increase in the distance between these objects?

Part II: As an object accelerates it gains mass. Would the same Doppler Effect be noticed between stars for instance, if you were travelling in a spaceship towards one? In other words would it appear as if space is being stretched even if you are accelerating towards an object in space?

Ummmm, why would a galaxy constantly be gaining mass? I mean, I guess its possible it its gravity were taking in particles from outside of it, but I think there is just a void in that area of space.

I personally have not seen enough evidence to convince me that matter gains mass as it approaches the speed of light; maybe it does, but until we have done objective experiments, no level of math can convince me. :?

Originally Posted by Cold Fusion

I personally have not seen enough evidence to convince me that matter gains mass as it approaches the speed of light; maybe it does, but until we have done objective experiments, no level of math can convince me. :?

As a particle's speed increases, it's kinetic energy (KE=.5mv²) increases. According to E=mc², mass is equivalent to energy, and as KE increases, mass increases.

Yes, but have you considered the possibility that a physicist hasn't proven parts of that equation wrong yet?

Einstein disproved many of Newtons equations; what if some time in the future the same thing will happen to Einstein?

To me, it just doesn't seem logical, so regardless of his credibility I will not adhere to every theory that he has created.

Originally Posted by Cold Fusion

I personally have not seen enough evidence to convince me that matter gains mass as it approaches the speed of light; maybe it does, but until we have done objective experiments, no level of math can convince me. :?

Simple Sophomore Physics Lab. Accelerate electrons in a fairly simple CRT and then try to deflect the electrons with magnetic fields. Start at low accelerator voltages (accelerator voltage is proportional to final speed) and strong magnetic fields. You will see that you can deflect the electrons by 180°. The radius of said (half) circle can be determined. Going to higher accelerator voltages will increase the radius up to a point where the behaviour is no longer linear as you start seeing the relativistic effects like e.g. mass gain at relativistic speed. And the people at New Haven National Lab (SUNY Synchrotron Light Source) also have to deal with this effect, just go ask them

Lets just say Einstein is correct; where would the particles gain their mass from?

you are using the wrong term, it is not mass that is gained;

to demonstrate:

at a speed of 0 space isn't bent,

at a speed of 10 space is bent,

at a speed of 100 space is bent even more,

weight is based on the bending of space (gravity).

Originally Posted by zinjanthropos

Sorry about my lack of knowledge here and thanks to the membership for at least being tolerant of it.

This one has always bothered me. If a galaxy is constantly gaining mass then could it also constantly affect the Doppler effect? Would not a larger mass have more of an effect on light waves then one of lesser mass? I'm thinking that an ever increasing mass would constantly stretch light waves. If this is so then is the expansion of the universe, the stretching of space, merely a result of mass increases of the heavenly bodies? Is there an actual increase in the distance between these objects?

Part II: As an object accelerates it gains mass. Would the same Doppler Effect be noticed between stars for instance, if you were travelling in a spaceship towards one? In other words would it appear as if space is being stretched even if you are accelerating towards an object in space?

Right...

Zinj,

I've attempted a response three times already and given up. Here's my fourth attempt.

1. I presume you mean that galaxies are gaining mass as a result of their gravity that pulls other interstellar material towards them?

2. I believe you are correct to assume that gravity will have an effect upon light waves that is, in many cases, akin to the Red Shift.

3. I'm therefore assuming that your main question is this: how can we tell that the red shift is a result of space expanding (and the distances between galaxies growing) as opposed to simply the enervating effects of massive objects upon the light they emit.

If this is the case, then one answer suggests itself in principle: gravity (or the distortions in space due to massive bodies that we conveniently call gravity) acts as though from specific points. Expansion, on the other hand, affects all points equally. We would, therefore, expect to see a different spatial distribution of the red shifts depending upon which way the light is being affected.

For instance, I hypothesize that, for a galaxy that we can resolve into its basic shape (not necessarily all the way to its individual component stars), then we should see a red shift effect mainly in the light that is emitted by those parts of the galaxy that are directly between us and its centre of gravity. Light from sources (still in the galaxy but further out) will show gravitational lensing, but not necessarily a red shift itself. We might almost say that the distortions should give the effect of a halo - outer galactic emissions being focused together with little or no red shift, but a darker central portion with less energetic light.

As it happens, what we tend to see in galaxies is primarily in accordance with the idea of movement -towards or away from us. Thus in general there will be an overall red shift in all the light from the galaxy but... it might be less for sources from the 'leading edge' of the galaxy (the arm that is rotating and approaching us) and greater for the trailing arm that is leaving us. Thus the red shift effect, for a galaxy edge on to us, should show a grading from left to right (or vice versa), which would be distinct from the centre-biased red shift that gravitation would cause.

Of course, I have no science credentials whatsoever so this is just armchair theorising and I'd love it if someone who her/his stuff could put us right! (Unless this explanation makes sense, of course.)

With regard to your Part II - I don't believe that the general increase in mass due to acceleration would normally play a part. If you were moving towards a star more swiftly than that star is moving away (due to the expansion of the universe) then you will see a blue shift in the light from that star.

Now if a truly massive body, like a black hole, could be accelerated to a large proportion of the speed of light, I have no idea what might happen... :?

cheer

shanks

Originally Posted by miomaz

you are using the wrong term, it is not mass that is gained;

Natürlich ist das Massenzuwachs, denn das ist einer der Hauptgründe warum massebehaftete Teilchen niemals (Vakuum)Lichtgeschwindigkeit erreichen können, denn dann wird deren Masse unendlich groß. Die Krümmung des Raums ist nur die umittelbare Folge.

MÖÖÖÖP

Originally Posted by sunshinewarrio

Right...

Zinj,

I've attempted a response three times already and given up. Here's my fourth attempt.

1. I presume you mean that galaxies are gaining mass as a result of their gravity that pulls other interstellar material towards them?

2. I believe you are correct to assume that gravity will have an effect upon light waves that is, in many cases, akin to the Red Shift.

3. I'm therefore assuming that your main question is this: how can we tell that the red shift is a result of space expanding (and the distances between galaxies growing) as opposed to simply the enervating effects of massive objects upon the light they emit.

You got it, sounds pretty close. If the galaxies are steadily gaining mass then do they stretch space between them even if they approach each other? If I was to gain mass by increasing my speed would the effect be the same, would I notice a lot of red shift in any direction I look?

Originally Posted by zinjanthropos

You got it, sounds pretty close. If the galaxies are steadily gaining mass then do they stretch space between them even if they approach each other? If I was to gain mass by increasing my speed would the effect be the same, would I notice a lot of red shift in any direction I look?

Short answer: nope.

The only stretching of space I know of is the Big Bang itself - not caused by gravity.

The gravity 'wells' created by massive objects distort space in their vicinity (as the inverse of the square of the distance from the centre of gravity!) not the entire space between them.

Finally, the relativistic distortions of space and time produced by travelling close to the speed of light (objects appearing shorter, time appearing dilated etc) will far outweigh the effects of the mass increase upon these bodies, I believe. Again, happy to be corrected by someone who really knows.

cheer

shanks

Has anybody considered that there is no limit to the size of universe, and that its only the matter that is expanding to farther reaches, and not the actual boundary itself? I mean, there could very well be a boundary, but I feel as if people sometimes talk about certain things as if they are facts, rather then educated theories.