BusaDave9

My feel is that while all quasars are super massive black holes, the converse need not necessarily be true.

I agree. When a massive star becomes a black hole it will not become a quasar unless there is still a lot of matter nearby to fall into the hole and create the energy source for the quasar. A young galaxy could have that matter.

Our own galaxy would appear as a quasar viewed by anyone looking towards us from the "edge" of the universe. Does that make our galaxy the "edge" of the universe?

No our galaxy is not a quasar.

 

Are you sure about that? Not all galaxies would be seen as quasars from a distance - only those with a particularly voracious accreting super-massive blackhole at the centre. I don't know what the milky way was like 12-13 billion years ago - but I am not sure it was a quasar.

Imatfaal is correct. Quasars are massive black holes at the center of some galaxies. They are the brightest objects in the universe. Actually they don't seem to exist anymore. They were much more common early on in our universe. Most quasars are so distant they are almost moving away from us at the speed of light (red shift from the expanding universe).

 

IOW, Newton does not predict the effect accurately.

Newton did not, could not, predict the movement of the perihelion (even if he had the data collected in the 19 century) but his equations are still extremely accurate IF you consider the ellipse to be moving relative to universe and everything in it. Newton would never have said the orbital ellipse is moving BUT HIS EQUATIONS DO NOT DENY IT.

Good discussion

"Can't be explained" is an issue of accuracy. Newtonian gravity does not predict the right amount. It is not as accurate as GR.

Newton's equations are accurate. Here is an exaggerated view of precession of the perihelion of Mercury's orbit:

Before Einstein the scientist thought there must be another planet closer to the sun pulling on Mercury. They were so sure that they even named this planet Vulcan (trivia for Star Trek fans) before it was discovered.

For the classical physicists the only other explanation would be that the rest of the universe is rotating around the sun making it look like the perihelion is moving. If that were the case then Newton's equations would be extremely accurate. But of course that would mean distant galaxies would be moving faster than the speed of light. It would also defy the notion that the sun did not have a special place in the universe.

Then Einstein said this precession of the perihelion is relative. He didn't even have to use any math to show that you could consider the orbit to be perfect ellipse but the movement of the perihelion was relative.

 

No Einstein explained Gravity as space time curvature and in doing so removed the need to think of it as a force.

No need to think of it as a force? Just becouse Einstein says graity is a spacetime curvature doesn't mean it's not a force. This argument is like saying "a tiger isn't an animal, it's a mammal."

There are only four forces in the universe and gravity it one of them. For extra credit what are the other 3?

Newtonian gravity is remarkably accurate and hugely simpler - but in fairly simple equations and observations we can show that Newtonian gravity gets the incorrect answer and that GR is precise.

The equations for Newtonian grvity are correct. The issue is not accuracy. The issue is some experiments, such as the precession of the perihelion of Mercury's orbit, can't be explained by classical physics. Einstein says that precession is relative.

One reply; Einstein, General Relativity (or is that 2)

gravity is not a force but a space-time curvature.

Gravity is a force. Einstein explained this force as a space-time curvature but that doesn't mean he disproved classical physics as explaining gravity as a force. Newton and Kepler's equations are still accurate.

Being in free fall means there are no forces acting on you.

No forces??? How are you falling? In free fall here on Earth you will be accelerating 32 feet per second squared. Every second you will be going 32 feet per second faster than the second before. There must be a force. Gravity is accelerating you.

The only force is the earth pushing 'up' on your feet when you are NOT in free fall. That's why we measure weight in units of force and acceleration in units of gravity.

... and you pushing down with your weight. To every action there is an equal and opposite reaction. So when the earth is pushing up your weight is pushing down. When you are counteracting gravity this is the only time you notice it. Your earlier statement would be more accurate to say you never notice the gravitational force when you are in free fall. THAT's General Relativity. Accelerating motion is relative. Einstein showed gravity and inertia as being 2 manifestations of the same force. If you were in a spaceship accelerating 32 feet per second squared you would experience 1 G of force. You could walk around on the floor of your rocket and think you were on Earth. So as the accelerating rocket pushes against your feet you press back and once again you notice this "gravity" only because there is a force counteracting it. But is this really gravity or inertia? It's relative.

The higher elements are radioactively unstable. The heavier elements are so unstable they quickly decay. For that reason I don't think there is a definite maximum number of elements. These higher elements were created in laboratories and don't exist in nature.

No, its most accurate to say inertial mass and gravitational mass are the same.

If an object has 1 gram inertial mass it also has 1 gram gravitational mass.

So yes these values are always the same. Since they are the same everything falls at the same speed.

As for acceleration and gravity, if they produce the exact same effect, how are they not equivalent?

Is acceleration not measured in Gs?

How do acceleration and gravity produce the same effect? Yes they are both measured in Gs.

Gravity can cause acceleration.

If I am standing on a bathroom scale it says I weigh 170 pounds. I am not accelerating.

If I was in anything free-falling such as an elevator with broken cables or a free falling spaceship (disregard air and other friction) then I am accelerating but no longer pressing on the bathroom scale.

If I am standing on the earth I experience gravity because my legs are counteracting gravity (pressing against earth) But if I am free falling and not pressing with my legs then i don't notice gravity.

If I am in a spaceship drifting and suddenly press my legs on the side or floor as if jumping I can experience a g force AS I am accelerating.

If I turn on the spaceship engines I am pressed in the back of my seat as I am accelerating.

If I am not applying any force to counteract gravity or inertial I am floating. I would float in a free falling elevator (even if I was on a huge planet). I would be floating in a spaceship with engines off far from any star or planet.

We are moving at c/2 relative to light.

Please explain.

Actually I don't think you are speculating. I think you are misunderstanding physics.

In 1887 Mikchelson and Morley set out to find out the absolute speed of Earth. They knew light traveled at 186,000 miles per second so they performed experiments to see how fast light was traveling relative to Earth. (actually they were comparing the speed of light coming from different directions)

Their experiments showed that the Earth was not moving. They showed that light always passed by Earth exactly as if we were standing still. This was very confusing since they knew the Earth was spinning on its axis and the earth was in orbit around the sun and the sun was moving in the galaxy.

Then Einstein Showed that, although motion and speed is relative, the speed of light is always absolute. Light will always pass up the fastest spaceship as if it's standing still.

We are moving at c/2 relative to light.

If you are talking about E=MC²

This is not talking about our speed relative to light.

Energy = Mass X Speed of light squared

That means if mass is converted to energy (such as a nuclear explosion) that the energy resulting is equal to the mass times the speed of light squared.

In other words there is a LOT of energy in a little mass.

I made this thread a poll because I knew that, even if everyone was looking at the same data, some would say we're very overpopulated and some would say the Earth can sustain much more people.

When Mother Teresa was asked about overpopulation she said "how could there be too many people? That's like saying there are too many flowers."

 

I think, the science of Biology will have to clarify the term 'overpopulated'...

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From such definition it is not clear whether the environment is allowed to change substantially or not... Humans are, however, capable to change (to engineer) the environment substantially into a very different form that is capable to support them.

 

Because of this, there is now a communication problem between you and me. (Despite the fact the we both agree that the pressure from humans toward wilderness is much too high for wilderness to sustain.)

No the environment is not allowed to change at all. If the environment does change then it is overpopulation.

If the population of deer in a area becomes so high that they eat up most of the vegetation then that is overpopulation. In such areas you can see just how high the deer can reach because all the leaves below a certain height on the brush and trees are all eaten by the deer. Just because the deer can survive doesn't mean they are not overpopulated. By everyone's definition (except Danijel Gorupec's) once the environment is impacted then it is overpopulation. A species does not start to die off from lack of resources until the very late stages of overpopulation.

Speeds and motion are relative. Except for the speed of light. No matter how fast a spaceship is traveling light will always pass it up exactly as if it's standing still.

What, exactly, is wrong with a vegan diet? It's far less cruel than meat-eating (especially with our current factory farm system), and it is demonstrably better for the environment.

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Free them. Keeping animals for consumption is not only unethical, it is woefully inefficient and damaging to the environment. Predators would probably eat most of them, but some will survive and even thrive in the wild.

First off I love meat. A nice big steak is my favorite food.

Secondly we have canines for a reason, were are meant to eat meat. We're omnivores.

We need big factory farms because we are overpopulated. If a large percentage of the population were to become vegans we wouldn't release the cattle and pigs to roam the wild, we would simply produce less livestock. We have complete control over their population. Sure we raise the cows and pigs just long enough to be killed for food but I believe it's better for the animals to have a short life than to never have lived at all.

We are overpopulated and it's evident because of the degree that we disrupt the environment.

We have to all be ecological with our resources because of our overpopulation.

And if we have to become vegetarians then we are most certainly overpopulated. We are omnivores.

We have taken over most of the fertile land as farmland.

Environmental deterioration is part of the definition of overpopulation.

http://www.merriam-webster.com/dictionary/overpopulation

Straining available resources is also part of the definition

http://dictionary.reference.com/browse/overpopulation

 

I sure hope you aren't serious about this.

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we left the hunter/gatherer process quite some time ago

oh no I didn't mean we should all go back to hunters and gatherers. I only meant we could hunt if we want or kill livestock. I don't like the idea of our population being so high that we have to resort to raising meat in such tight confines as artificial meat factories.

Exactly. We can grow our food in labs and sustain our population - therefore we are not overpopulated.

 

I am afraid you asked the wrong question... you asked if we are overpopulated, but you realy wanted to hear how do we feel about exterminating other life.

So if wolfs grew in population that they were killing up all the deer, all the racoons, the beavers and otters. They would not be overpopulated? They would continue to exterminate other life forms but never be overpopulated until they kill off all their food. Once they start to die off because they killed off their food, only then, during their demise would you consider them overpopulated?

 

Conquest/colonization of galaxy is not a solution?

 

No, I don't think so there is too many people yet.

Food can be easily produced by changing DNA of bacterias to generate proteins, hydrocarbons, vitamins, fat etc.

Colonization of other planets is still very far off. I believe we are already very much over populated.

Did you guys vote?

from the looks of the responses everyone but kindheart seems to think we are not at all overpopulated. But the poll says everyone agrees with me that we are already over populated.

I'm not addressing any of your other points or suggestions or comments, but out of curiosity why do you think the above is a problem somehow? Specifically, the petri dish proteins? That confuses me how someone could see that as a bad thing, especially someone who cares about our planet and the life on it.

I would try it but petri dish meat, that's just not right. I care about the life on this planet but I also firmly believe in the natural food chain. Let's go out and kill our own meals. I am firmly against killing off wolfs and other animals that are a threat to our livestock, us and our safety. I live in the mountains of SW Colorado. We have wolfs, bear and mountain lions here. They may be scary but I eagerly hope to see these animals when I am out. They aren't too much of a threat since none of them consider us thier prey. but they are still far from being safe animals.

If i gave the impression that I care so much about animal life that I am a vegan that's far from the truth.

I came to conclusion that today people are happier (in average) than 100 years ago. Even more than 500 years ago... I know that many of you won't agree, but this is my view: we are happier than ever... I don't know if this is sustainable, but I think it is.

Yea, we are happier than ever. So what? So we are the most important animal? The heck with all other species? I'm looking over the members that have responded to this thread. I really don't know you guys but I'll go out on a limb and say most of you are humans. If I could get some more deer, bear and maybe even wolfs to chime in I bet we would get more responses saying humans are crowding out wildlife and animals the world over. The other animals need a chance. And they need us to give them a chance. We could kill off any animal that inconveniences us.

Now, what is "overpopulated"? Is this 'harming other living creatures' or is this 'being unable to sustain our own numbers'? I am with the second answer and, therefore, I think we are not overpopulated. Other creatures will be harmed, but this is what evolution is - they should adapt or die. Many adapted already - wheat, corn, dogs, pigs...

 

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If you, BusaDave9, try to reduce the population by 3 orders of magnitude, we won't be as happy any more.

The question is, are we overpopulated. As I understand, overpopulated means "being unable to sustain own number by any mean".

Wow, by that standard no other animal has overpopulated the world (maybe a local area).

By that standard humans could populate the whole world as one big city and grow our food in laboratories (such as the petri dish meat posted earlier) Like what was talked about in this thread: http://www.scienceforums.net/topic/57972-do-we-need-so-many-other-animals-on-earth/

isn't it impossible to distinguish any 2 = forces?

a iron robot would be unable to tell if he experiencing gravity or magnetism or acceleration.

 

Gravity can be shown to pull on anything with mass. Magnetism only affects some metals. Acceleration is not a force, it's the result when a force is applied. That was my point earlier. That I think it's more accurate to say inertia and gravity are the same (so says Einstien). Acceleration and gravity are not the same.

You can see where we are. If you have read my posts you can guess where I think our population should be.

This chart shows why I don't think there is a practical solution to our over population.

These gun laws are getting ridiculous. The last time I went to the sporting goods store and was ready to pay for my purchase of ammo the clerk told me "Strip down facing me".

Well, I did just as she instructed. As the screeching was dieing down i realized that she was talking about my credit card.

Is it just me or do they need to be more clear with those instructions?

I guess it hardly matters now. I was told I have to conduct my shopping elsewhere in the future.

Phi for All, what you are talking about is ZPG or decreasing the population a bit but since my opinion is the earth is over a thousand times overpopulated that's why I don't think there is a practical solution.

So, what do you advocate we do about it, then?

Overpopulation is a problem that has no practical solution.

I hate to complain about things without a solution but I'm afraid that's what I'm doing.

I do think it's overly simplistic to look solely at population numbers. More important than the overall number of humans alive is how we use resources

I think it is all about the numbers. You may think we can populate the Earth all we want as long as we use the resources wisely. I think that is managing an extremely overpopulated Earth. I think we are overpopulated by a factor of thousands or 10's of thousands. There is no other animal that has taken over the landscape as much as humans. Sure you can find local areas where deer are overpopulated but not over the whole world like the humans are.

The overpopulation that humans experience is not found with any other large animal. But it does happen with smaller organisms such as bacteria, algae and yeast. Long ago before people learned how to keep food sterile and fresh they could not enjoy grape juice unless it was freshly crushed from grapes that were just picked. Within a couple days natural yeast would infect the juice. The yeast would eat the sugars and produce alcohol. The alcohol is their waste. Grape juice would turn to wine within a couple weeks. Bacteria would also infect the juice so this uncared for wine would also be sour. Within a few weeks the yeast would eat up all their food (sugar) and be swimming in their own waste (alcohol). At that point the yeast would die by the millions. This is the point that I think we humans are at. We humans live in cities of hundreds of thousands or millions. We can not get food in those densities EXCEPT for bringing our technologies into the problem. We can truck and transport food from the farmlands to the cities. If we had zero technologies our cities would die up just like the overpopulated yeast. Even if we migrated to the farmland and distributed our population over the fertile land we would not be able to sustain our population without technology. If we had to have our food so close that each of us had to walk out to our field and pick our own food. Or if we had to go out and kill our own animals most of our population would die off. There are lots of fertile land that can support lots of people but there is also a lot of very dry lands. Earth could not support our population without our technologies.

Yes, Michell123456 you have it right, motion is relative and these distortions of spacial and temporal dimensions are relative to the viewer. So in your spaceship a clock seems to be running just fine. Why? Because it isn't moving relative to the viewer. Motion is relative. You could think of it as if your spaceship is still (from your point of view it is) Everything you are passing seems to be going by fast. Everything you pass seems to be distorted and time is running slow.

How could you check the speed of the spaceship? Lets say you set up two lasers 186,000 miles apart. You could then measure how long it takes for your spaceship to cross from one laser beam to the other. As you are traveling at an extreme speed you seem to to be crossing those laser beams in less than a second. THAT's how you would (at first) think that you are going faster than the speed of light.

As you are flying your spaceship across those 2 lasers you realize they can't really be 186,000 miles apart. You are right. You could take measurements from your spaceship and find out that they are much closer together. This is because the space between the lasers is compressed because of the your motion. From your point of view the lasers seem to be moving at an extreme speed. The distance between them is much less than the point of view of the people that set them up.
SPEED IS RELATIVE. THESE DISTORTIONS ARE RELATIVE TO THE VIEWER. If an object is not moving relative to the viewer it is not distorted.
The same is true of the clocks. A clock on the spaceship doesn't match up with a clock on Earth or any thing being passed up by the spaceship.

Because of these distortions you can always go faster. You could calculate your speed to be 99.99% of the speed of light and then accelerate so fast you are pressed back into your seat. A month later you are still not going the speed of light. It's because of these distortions. Motion is relative. These distortions are also relative.

So “Gravity IS acceleration”? Enthalpy, I would like you to explain this to me. In the mean time let me explain how I see them as being related.
First off, acceleration is an increase in speed. Gravity can cause acceleration if you are not applying a force to counteract that gravitational force. The gravitational force here on Earth is strong enough to accelerate you 32 feet per second squared. In other words gravity will accelerate you 32 feet per second faster than the second before.
For example, lets say you jump off a building. (lets ignore wind resistance and other forces). After one second you would be going 32 feet per second. After another second you would be going 64 feet per second. No matter what your speed is, gravity will accelerate you 32 feet per second faster than the second before. So far, with gravity, I have only been talking about classical physics.

Einstein's General Theory of Relativity talked about gravity. It said that gravity actually warps the space time continuum. For this reason light bends as it passes by large bodies with very strong gravitational fields. This is also the reason he said gravity affects time. He also said this gravitational force and it's acceleration are relative. What's that mean? Well, if I am standing on the ground I feel gravity because my legs are pushing on Earth with 170 pounds of force. I feel gravity. If you were to put a heavy backpack on me I wouldn't want to carry it very far. But if I were in a spaceship drifting in space (no thrust from engines) far from any star or planet, that backpack wouldn't be pulling on me. But Einstein said there is gravity everywhere. Earlier I said I feel gravity only because my legs are pushing against Earth. So lets take our spaceship back to Earth or better yet a bigger planet with a very strong gravitational pull. Our spaceship is now plummeting toward this planet. We are already near the surface so our spaceship is accelerating much faster than 32 feet per second squared (as it would on Earth). We'll say this planet doesn't have an atmosphere (I'm trying to keep out all other forces and friction). Inside this falling spaceship Einstein showed that there is no experiment that could prove we are falling (even acceleration is relative). There is no experiment that could prove we are in a strong gravitational field. Einstein said gravity can even affect time. But that too is relative. Even if we were falling into something as massive as a black hole we would still think our clock is accurate. It seems to be clicking away normally. XYZT pointed out one minor exception. Tidal forces can show that you are near a strong gravitational force. But in my example tidal forces would be immeasurable. The right side of the ship is falling toward the center of this big planet and the left side of the ship is also falling toward the center of the planet. Its true that these 2 paths are not parallel but in a spaceship they are so close to parallel you could never detect the difference. If it was one planet or moon near anther planet then yes tidal forces could prove the existence of the gravitational field. What I am saying is tidal forces can be neglected in this spaceship example.

If you were near the event horizon of a black hole the tidal forces would also be extremely high.

A tidal force is when gravitational forces are not parallel even though they are pulling toward the same object. A tidal force can also mean the closest part of a body to the planet experiences higher gravitational force. The nose of our spaceship isn't much closer to the planet than the rear of the spaceship. These are the reasons I don't think we need to take into account tidal forces when we are talking about something as small as a spaceship.