Expansion of the Universe, cop this

In summary: They would weigh you and find that you have, indeed, gained mass. Relative to them. The movement of things in the universe is relative to other things in the universe. The idea of absolute motion is no longer considered meaningful.In summary, during a conversation about an interesting theory regarding the accelerating expansion of the universe, it was brought up that an object traveling at near light speed would gain mass and thus have more gravity, potentially causing the expansion to slow down and reach a state of universal equilibrium. However, experts in the conversation explained that this is a common misconception and that the mass of an object does not change in its own reference frame, only in relation to an outside observer. Additionally, extreme densities are needed for an object to
  • #1
Ryan Lucas
14
0
Hi! I am doing year eleven physics and love it, I am a teachers pet and all. Anyway, I have this theroy with my physics teacher, we came up with it together its really cool. So anyway, the expansion of the universe is accelerating, "defying gravity". Anyway, let's assume that it keeps accellerating infinitely. Now eventually the expansion of the universe must reach near light speed right? now an object traveling at near light speed GAINS MASS, it weighs more. Now with a higher mass, it thus has more gravity, more gravity means that the accelerating expansion of the universe must slow, Ergo universal equilibrium!

Have you got any thoughts on my theory? Can you disprove it? Please do!
 
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  • #2
Ryan Lucas said:
Have you got any thoughts on my theory? Can you disprove it? Please do!
If I'm understanding it correctly, it would appear to be another case of misunderstanding the expansion of the universe. The things in the universe are not moving relative to the space they're in; the space itself is expanding. Therefore, no relativistic mass increase.
 
  • #3
Ryan Lucas said:
Hi! I am doing year eleven physics and love it, I am a teachers pet and all. Anyway, I have this theroy with my physics teacher, we came up with it together its really cool.
While your enthusiasm is admirable, perhaps it's a bit premature to be developing your own theory. :wink:

I'll move this to the General Astronomy and Cosmology section, where experts aplenty will inform and delight you!
 
  • #4
An accelerating body does not have more gravity or mass. What you are talking about is relativistic mass, and that does not add to the weight of an object. Consider an object falling to earth. As it gets closer there is acceleration due to gravity, so the object speeds up. It does not change its weight as it is falling. When it hits the ground it may leave a deep impression, deeper than it would have if it was dropped from less of a height. This is because of the objects inertia and not its weight which remains constant.
 
  • #5
Welcome to Physics Forums, Ryan_Lucas!

As Danger already mentioned, part of your idea is one of the most common misconceptions about cosmology (and GR). There's a recent issue of Scientific American with an article by Lineweaver (he of UNSW) on this (and other) misconceptions. IIRC, there's a link to an online version of this article in another thread here in GA&C. If not, I'm sure a quick google will find it. If you're interested, here's a more technical paper by Lineweaver and his colleague, Tamara Davis
 
  • #6
Mmmm, thanks for your responses, they really helped. By the way, am i right that when they reach NEAR LIGHT velocity, an object will gain mass? This is shown by Einstien's famous formula?
 
  • #7
Ryan Lucas said:
am i right that when they reach NEAR LIGHT velocity, an object will gain mass? This is shown by Einstien's famous formula?
An object gains relativistic mass with every increase of speed. (And keep in mind that velocity is a vector, as opposed to speed which is a scalar measurement. ie: velocity requires a direction as well as a speed. This is why something veering off on a tangent to its original course undergoes a change of velocity even if its speed remains constant.) You have the right basic idea, but serious refinement of it is necessary.
 
  • #8
If you were co-accelerating with the body in question, you would both swear neither of you gained a pound.
 
  • #9
Chronos said:
If you were co-accelerating with the body in question, you would both swear neither of you gained a pound.
I am so tempted to make a Jenny Craig joke here, that I think I shall head down to GD before I say something embarrassing.
 
  • #10
This is cool man

Ryan Lucas said:
Mmmm, thanks for your responses, they really helped. By the way, am i right that when they reach NEAR LIGHT velocity, an object will gain mass? This is shown by Einstien's famous formula?

If what U r saying is right then all the objects apporaching speed of light must collapse into BlackHoles, Wow I never thought of that before. All this is vrey enlightening.
 
  • #11
no, that is incorrect. the mass of the object in it's own reference frame does not change, hence it doesn't collapse into a black hole.
 
  • #12
O yaa

matt.o said:
no, that is incorrect. the mass of the object in it's own reference frame does not change, hence it doesn't collapse into a black hole.

Then where is the resistance to the acceleration comming form as we approach highere speeds ? Or is it an problem limited to the particle accelerators only.
 
  • #13
actually, I think relativistic mass may contribute to a gravitational field, I am no expert here! nevertheless, the mass has to be confined within a region such that the density must be high enough to form a black hole. mass alone does not cause a body to collapse into a black hole, extreme densities are needed.
 
  • #14
Anomalous said:
Then where is the resistance to the acceleration comming form as we approach highere speeds ?
That's where the 'relative' part of 'Relativity' comes in. To itself, the object undergoes no change. Relative to an outside observer, it gains mass, shortens, and has its time slowed. If, for instance, the Earth were to speed up in its orbit, taking you with it, you would still weigh the same on your bathroom scale even though you are moving faster. Someone on Mars would think, "Jeez, that guy's getting heavy!"
 

What is the "Expansion of the Universe"?

The expansion of the universe refers to the theory that the universe is continuously expanding in all directions. This means that the distance between galaxies, stars, and other celestial bodies is getting larger over time.

What evidence supports the expansion of the universe?

The expansion of the universe is supported by various pieces of evidence, including the observation of redshift in the light from distant galaxies, the cosmic microwave background radiation, and the abundance of light elements in the universe.

How does the expansion of the universe affect the motion of galaxies?

The expansion of the universe does not affect the motion of galaxies within their local clusters. However, on a larger scale, the expansion causes galaxies to move away from each other at an accelerating rate.

What is dark energy and how does it relate to the expansion of the universe?

Dark energy is a theoretical form of energy that is believed to be responsible for the acceleration of the expansion of the universe. It is thought to make up about 68% of the total energy in the universe.

Will the expansion of the universe ever stop or reverse?

Based on current evidence, it is believed that the expansion of the universe will continue indefinitely. However, there are some theories that suggest the expansion may slow down or reverse in the distant future due to the effects of dark energy. This is still a topic of ongoing research in the scientific community.

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