Gravitational Lensing and the Einstein Ring (Earth, stars, light, Sun)
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This particular star, informally known as Icarus, is behind a large cluster of galaxies called MACS J1149+2223, and while the mass of the cluster brightened the star a bit, it wasn’t enough to be easily seen by the Hubble Space Telescope. But then a star from the cluster happened to pass in front of the distant star. This created an effect known as an Einstein ring, where light from Icarus grazes the closer star and is focused in our direction. The result is a significant brightening of the star. The combination of gravitational lensing from the galaxy cluster and the Einstein ring made Icarus appear 2000 times brighter than it actually is, making it bright enough for Hubble to capture. It’s light traveled for 9 billion years to reach us, making it the most distant main sequence star we’ve ever observed.
So what exactly is it which is giving us this gravity lens and how does it manifest to us here on Earth? What does a gravity lens act apon? Is it the photons of energy passing through the lens?
We know that light bends around a body, but it also bends as it goes through a slit. There is no gravity in a slit so how do we know it is gravity which is doing the bending? What is gravity, does anyone know and has it been properly investigated since the time the apple fell from the tree?
Is there a science of gravity just like there is a nuclear science, or an optical science or an electrical science?
So what exactly is it which is giving us this gravity lens and how does it manifest to us here on Earth? What does a gravity lens act apon? Is it the photons of energy passing through the lens?
A gravitational lense is produced by the gravitational field of stars, galaxies, and dark matter. That gravity bends light thus making it possible to see stars that would otherwise be hidden behind stars the are in front of them. Gravitational lensing causes starlight to bend around massive objects and can cause multiple images of a single object.
We know that light bends around a body, but it also bends as it goes through a slit. There is no gravity in a slit so how do we know it is gravity which is doing the bending?
Because Light is a wave it spreads out when it passes through a narrow slit. This is called diffraction.
What is gravity, does anyone know and has it been properly investigated since the time the apple fell from the tree?
Is there a science of gravity just like there is a nuclear science, or an optical science or an electrical science?
One theory is that there are particles called 'gravitons' which mediate the force of gravity. On the other hand, according to Einstein, gravity is not a force but is the curvature of space and time caused by mass. But that always leaves me wondering what property of mass itself causes the curvature of space which is being called 'gravity?' It seems to me that the mass itself would have to exert some force which causes space to curve which in turn is being called 'gravity.'
Because Light is a wave it spreads out when it passes through a narrow slit. This is called diffraction.
As I understand it, it bends different amounts for the different wavelengths of light and so maybe it is the sharp edge which has the effect rather than the gap? If so, then the outside 'edge' of a distant planet is just an edge pulled into a circle making the lens by bending the light - just as it does with a slit/edge? Do we know it is NOT the edge which is doing the bending ?
Every kid has used a magnifying glass to burn a dry leaf: the glass in the lens captures all the lite hitting its, say, 4 inch surface and bends it (via diffraction) into a small dot at the focal point. Same number of photons, but concentrated into a smaller area.
Another allegory: Are you familiar with "Great Circle Routes" to fly from, say, NY to Rome? Both are about the same latitude, but you don't fly straight east . It's actually shorter to set a course NE. The curvature of the planet's surface makes that a shorter course.-->
Now suppose you were in a stationary orbit over the equator, looking down on two airplanes at an airport on the equator, about to fly to another airport also on the equator. One plane will fly a great circle course starting out to the NE, while the other sets its course to the SE....As the proceed, they will first look like they are being forced apart, then after the half-way pt, will look like they are being attracted together...Some mysterious "force?"...or just a product of geometry?
That's what gravity does to space: it warps it, so as Einstein said "There are no straight lines in Nature."
A magnifying glass bends light by diffraction. Gravity bends light by warping spacetime....Either way, you get a field of energy (light rays) concentrated into a smaller area (more photons/unit area).
This particular star, informally known as Icarus, is behind a large cluster of galaxies called MACS J1149+2223, and while the mass of the cluster brightened the star a bit, it wasn’t enough to be easily seen by the Hubble Space Telescope. But then a star from the cluster happened to pass in front of the distant star. This created an effect known as an Einstein ring
So what exactly is it which is giving us this gravity lens and how does it manifest to us here on Earth?
Getting back to this thread, it is the large cluster of galaxies that supplies the gravity for the lens. The quoted situation is quite odd because it's a double lens -- "then a star from the cluster happened to pass in front of the distant star." The gravity from that star added to the gravity from the cluster, significantly brightening the background object Icarus.
Quote:
Originally Posted by ocpaul20
What does a gravity lens act apon?
The gravity of the cluster curves the space around it. It's the space that's curved that makes the lens. Then the light from the background object travels through the curved space.
Quote:
Originally Posted by ocpaul20
What is gravity, does anyone know and has it been properly investigated since the time the apple fell from the tree?
Oh yes, it has certainly been "properly investigated." We know its effect to an extreme level of accuracy. Exactly HOW it operates, however, how the Sun's gravity can affect Earth through all that "empty" space between them, is still a mystery.
Quote:
Originally Posted by ocpaul20
Is there a science of gravity...
As mentioned, General Relativity. It took Newton's science of gravity, which was pretty darn accurate, and explained how gravity's effects in very extreme conditions were different from Newton's equations.
9 Billion years. 9 billion times the earth goes around the sun, that is the time period for which the light takes to reach earth. That is hotter than the sun. I can only guess.
9 Billion years. 9 billion times the earth goes around the sun, that is the time period for which the light takes to reach earth. That is hotter than the sun. I can only guess.
I'm not sure where you're getting 9 billion years from. The earth is estimated to be 4.54 billion years old +/- 50 million years. The average time it takes light to reach the earth from the sun is about 8 minutes and 20 seconds. The universe is estimated to be 13.8 billion years old.
I'm not sure where you're getting 9 billion years from. The earth is estimated to be 4.54 billion years old +/- 50 million years. The average time it takes light to reach the earth from the sun is about 8 minutes and 20 seconds. The universe is estimated to be 13.8 billion years old.
He’s talking about the star in the original link, which is 9 billion light years away, though as you correctly pointed out, the Earth is only about half that age, therefore it could not have orbited the sun 9 billion times in that timeframe.
He’s talking about the star in the original link, which is 9 billion light years away, though as you correctly pointed out, the Earth is only about half that age, therefore it could not have orbited the sun 9 billion times in that timeframe.
That will teach me to pay attention to the thread.
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