What is Lensing: Definition and 87 Discussions

Lensing is a surname. Notable people with the surname include:

Kees Lensing (born 1978), Namibian rugby union player
Vicki Lensing (born 1957), American politician
Wilhelmina Elisabeth Lensing (1847–1925), Dutch feminist, politician and writer

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  1. M

    B Gravitational Lensing: Magnification of Galaxies

    How many time does a galaxy (same size as our milkyway) magnified the background ?
  2. Paige_Turner

    B Gravitational Lensing: Refraction or Something Else?

    It seems like a strong gravitational field acts like spacetime is denser in some sense. Light passing through a gravitational lens is delayed, just like in a glass lens (which refracts because it's denser than air).
  3. A

    I Gravitational lensing: deriving magnification of lensed image

    In gravitational lensing, the image magnification is defined as the image area over the source area. But many texts also give it as the inverse of the determinant of the jacobian, A, of the of the lens equation. My question is how these are equivalent. The lens equation is...
  4. ohwilleke

    I New Hubble Paper On Lensing In Galactic Clusters

    A new report based on Hubble Space Telescope observations is a big deal because it presents a new and independent apparent disparity between the lambdaCDM predictions for dark matter phenomena in galactic clusters and what is observed via gravitational lensing. The paper and its summary and...
  5. Helena Wells

    I Mass of the Moon and Gravitational Lensing

    During an eclipse the Moon covers the Sun.However this shouldn't be happening due to gravitational lensing we should be able to see some light? Is the mass of the Moon not big enough or photons do reach us but they are so little our eyes can't detect them?
  6. E

    B Gravitational Lensing & MOND: Does DM Explain Observations?

    Do gravitational lensing observations support the need for huge amounts of DM? If so, what do the MOND proponents say about that?
  7. sbrothy

    B Lensing Gravitational Waves Like Light?

    I was reading (or at least skimming) this paper: https://arxiv.org/abs/2005.10702 in which they seem to be discussing gravitational wave lensing. Is this an analogue of light lensing or is it another subject entirely? I mean, as I understand it, light is bend using gravity (as for...
  8. pinball1970

    I Gravitational lensing used to observe a distant galaxy

    The alert is here, https://www.sciencealert.com/supermassive-black-hole-jets-have-been-seen-slamming-into-gas-in-the-early-universe The abstract from the paper here, https://iopscience.iop.org/article/10.3847/2041-8213/ab7b7e The effects of jets from a black hole within the galaxy including...
  9. F

    Stargazing Is a star's size changed due to gravitational deflection (lensing)?

    Using the Sun as example, we know from the Eddington experiment that the Sun deflects light. Does light from other stars get deflected towards or away from the centre of mass, or is it a mix? Does light coming from the Sun get deflected towards or away from the centre of mass? Would this make an...
  10. R

    B Visual simulation of gravitational lensing

    Is there a way to generate an accurate visual computer simulation of gravitational lensing?
  11. DariusP

    Why is there a temperature gradient in lasers causing thermal lensing?

    Hello, I wanted to ask about thermal lensing. Thermal lensing is when a temperature gradient from the center of the medium to the outermost part of the medium is created. This causes a varying refractive index throughout the medium. What I want to ask is: Why is the core of the rod(or any other...
  12. B

    I Continuous Lensing Models: Discrete Data

    Hello, I am not sure if this question is better suited to the mathematics section, but I thought it would be easier to explain the problem here. In Schneider, Kochanek and Wambsganss's "Gravitational Lensing: Strong Weak and Micro" pages 279-280, they derive a relation for determining the...
  13. H

    I Deflection of Starlight by Newtonian Gravity - Example Calculation

    So, I have heard that the deflection of starlight using Newtonian gravity is only half of the deflection predicted by Einstein. NE1 know where I can find an example of the former calculation? thanks
  14. Rigel84

    B Gravitational Lensing: Gravity's Effect on Light

    This is my first (well second if we exclude introduction forums) topic here. I just want to make clear that I am not professional nor involved in field in any way. I am just regular Joe who wants to know more about nature. I could say that I understand fact that mass distorts space but there is...
  15. D

    Diffraction and gravitational lensing

    Hello. And i have a dumb question about light. When the diffraction is studied, we look at where the light is coming. But not where the light comes from. When the gravitational deviation is studied, we look at where the light comes from, but not where the light comes. What do you think...
  16. X

    High School video project: What is Gravitational Lensing?

    I want to pursue the sciences but I got no green. So I joined the BreakthroughJuniorChallenge in the hopes of winning! I would appreciate it if someone as knowledgeable as the people on this forum could comment and share my video submission. This is the link: It's also fine if you guys just...
  17. Dr Wu

    Need help with gravitational lensing issue

    I'm afraid I've come to a problem which I cannot solve. It concerns using gravitational lensing as a means of transmitting signals over interstellar distances. The real issue is finding the correct focal distance to make this possible. Now the only information I've been able to glean from the...
  18. S

    Stargazing What is Gravitational lensing?

    I have just glanced this magazine and got curious about what is gravitational lensing http://blogs.discovermagazine.com/d-brief/2017/06/07/19964/#.WYibwxWGO00 I am quite less knowledged in Astronomy, so explain me clearly!.:smile:
  19. K

    I Gravitational lensing - latest

    Hello, I'm fascinated by gravitational lensing and would like to know what is the latest in this area - I mean the latest interesting research that lensing is used for, to help understand something or suchlike. Thanks.
  20. wolram

    B Exploring the Evidence for Dark Matter: Weak Gravitational Lensing

    Do we need more proof of dark matter than this?: https://en.wikipedia.org/wiki/Weak_gravitational_lensing
  21. S

    B Gravitational lensing thought experiment

    Hello all, I'm starting to learn the math in physics and have the following thought experiment I want to use to work through something I own. The setup: There is a wall 10m from the center of a 1m diameter sphere. There is a 1m diameter light source casting a 1m diameter shadow on the wall...
  22. E

    B How to measure the amount of gravitational lensing?

    I am reading papers about dark matter and MOND. As they often mention this effect, I wonder how they know / measure / quantify how much gravitational lensing a particular galaxy causes? Thanks.
  23. maxhersch

    Gravitational Lensing and Angular Diameter Distances

    Homework Statement Given this diagram, the problem is to find an expression for β/ΘE in terms of X/ΘE and Y/ΘE. Homework Equations β = Θ – α(Θ) Dsβ = DsΘ – Dlsα'(Θ) The Attempt at a Solution I really only need help starting this problem. In my textbook and every document I can find online...
  24. O

    A Gravitational Lensing: Einstein's Blue Run Mystery

    Hi there. Have been doing some informant l independent research on gravitational lensing. It turns out that all einstein runs are blue. Why Is this?
  25. directbydirecct

    A Deriving Amplification of Images in Schwartzschild Metric

    In the paper Strong field limit of black hole gravitational lensing, the amplification of images in the Schwartzschild metric was given by $$ \frac{1}{\beta}\sqrt{\frac{2\,D_{LS}}{D_{OL}D_{OS}}} $$However the authors did not derive this expression or explain its origin. Does anyone know how to...
  26. O

    Gravitational lensing question

    Hi I am new to the forums. Only undertaken basic physics. Had a thought the other day and wanted to share it. Is lensing of starlight such as einstein rings ever caused by refraction? Could a matter density gradient theoretically cause the same effect? Thanks guys Sorry if its a repost...
  27. D

    Hasn't Gravitational Lensing Already Proved Einstein? (LIGO)

    The news out of LIGO is being heralded as one of the most important experimental verifications of physics in decades, as it provides experimental support to the General Theory. The news makes it seem as though it were like the Higgs Boson was; theoretically concrete, but up in the air until...
  28. Einstein's Cat

    Gravitational Lensing of Fast Receding Galaxies: Does Speed of Light Matter?

    I am aware that the greater a body's velocity the greater its relativistic mass. As a result, I assume that the faster a galaxy is receeding from us, the greater its gravitational lensing affect is. My question is this: does the extent of a galaxies gravitational lensing continue to increase at...
  29. Benwade

    Is photon gravity lensing affected by frequency (energy)?

    Homework Statement I am NOT a student. Please forgive my asking here, but if you do choose to answer, I would appreciate it. Obviously any or all of the statements below may be incorrect... As I understand it: The more energy a photon has (I know it's also a wave) the greater the frequency...
  30. SheriffPeabody

    Gravitational lensing as a way of observing Milky Way?

    Hi Everyone, first post here, another enthusiastic amateur I'm afraid so please excuse my general ignorance! I struck me the other day that it should be possible to find an arrangement of large galaxies that would allow light emitting from our galaxy to be bent back towards us. This would give...
  31. V

    Gravitational Lensing: Wave or Particle Nature?

    Is the phenomenon of gravitational lensing caused due to the particle nature of light or due to its wave nature? If not so, what is the correct explanation?
  32. A

    Gravitational lensing and Dark Energy

    Hi everyone I have been told that gravitational lensing affects CMB power spectra (TT, TE, EE) for high values of l (i.e. the least, low peaks on the right, say l>1000). But how? Isn't the effect of the varying gravitational potential along the line of sight the cause of Integrated Sachs-Wolfe...
  33. A

    The Future of Gravitational Lensing: What Physicists Expect in 15 Years

    What do physicists expect to do or find with lensing in the next fifteen years? Is there some specific object(s) they are looking for, or a concept?
  34. T

    Does Gravitational Lensing Cause Red Shift in Light?

    Does light get red shifted during lensing, when it passes by an object with great mass such as a galaxy or cluster? If so then what are the effects on measurements of the CMBR and most distant red shifted galaxies? If true then presumably some light would be red shifted more than others...
  35. PWiz

    Difference between images produced by gravitational lensing

    Around massive bodies, light bends so that we can see multiple images of the same object, such as multiple images of the same galaxy behind the massive body. I know this seems kind of a dim question, but how can we know that the similar images we pick up are light rays from the same object that...
  36. T

    Galaxy lensing and dark matter

    When we observe galaxy lensing of background objects taking place, is it possible to estimate the total mass of the galaxy carrying out the lensing and from that confirm that dark matter is needed to be present to provide sufficient mass to bend the light by the amount observed? Is there...
  37. ChrisVer

    Gravitational Lensing Derivations - Is There Another Way?

    Hey, I just had the chance to extract the gravitational lensing caused by a massive point using Fermat's principle. I was wondering though, is there any other way to do that? Also is the light's time delation induced by the "refraction index" n (Saphiro delay) connected to "gravitational time...
  38. M

    Solving Gravitational Lensing Homework for Hubble Constant

    Homework Statement A quasar at redshift 0.3 is gravitationally lensed into two images by an elliptical galaxy at redshift 0.18. The two images of the quasar are separated from the center of the galaxy by 1.1 and 1.6 arcseconds, on opposite sides. One of the quasar images flares up in intensity...
  39. S

    Gravitational Lensing: No Distortion of Sun Images Around Black Hole

    The dozen or so suns observed orbiting the black hole at the center of the Milky Way have exhibited classical continuous elliptical orbits about the black hole. How come there is no gravitational lens distortion of the suns image observed when the suns pass behind the black hole?
  40. W

    Gravitational Lensing: Is He Right or Wrong?

    I recently engaged in a argument with a fellow that tried telling me that gravitational lensing was not because of the warping of space due to mass but instead he told me this " On a cosmic scale , the mowing energy is in the form of angular momentum, quantum mechanically , the creation of...
  41. T

    Could gravitational lensing prove the universe to be older?

    This is only my second post and I am a novice. So please excuse me if this is a naive post. Gravitational lensing around galaxies shows more distant galaxies hidden behind them. We estimate the universe is 13.8billion years old because that's the limit we can observe into 'the past'. My...
  42. J

    Looking for some help with gravitational lensing and dark matter

    Greetings to all, A little information yo provide context to my question. I'm 16, and a junior in high school and I'm attending an astronomy camp on kitts peak doing research projects with the large telescopes. While researching possible projects on that particularly interested me was...
  43. S

    Gravitational Lensing vs Gravitational Microlensing

    Just a matter of terminology, are gravitational lensing and gravitational microlensing the same phenomenon? I have always been under the impression that they were. Any help? Thanks!
  44. E

    Gravitational Lensing: Solving Equation 2.1

    Homework Statement I'm studying about gravitational lensing and got stuck on an article: http://arxiv.org/pdf/0708.2684v1.pdf where the equation 2.1 is abit strange to me. The authour uses the reference http://arxiv.org/pdf/astro-ph/9703103v1.pdf for deriving the equation. According to me...
  45. S

    Interpreting Gravitational Lensing Images?

    I recently stumbled on the topic of gravitational lensing (GL) via an article in the Nov. 2001 issue of Sci Am magazine. I've since Googled the topic, and slightly enhanced my understanding of it. So far none of what I've read seems to interpret the resulting images. That is, they briefly...
  46. M

    Gravitational Lensing Q: Angle Deflection Sun/Earth?

    I have a simple question about gravitational lensing around our sun: is the angle of deflection 1.75" arcseconds the angle of deflection as the light goes past the sun, or the angle of deflection when it is received here on earth?
  47. S

    Gravitational Lensing: Exploring Light in Space

    Hi Everyone, This is my very first post here.. :) My question is regarding the gravitational lensing.. i understand that any object with mass in space causes the space to bend more like in the image here.. so imaginig a star behind the planet how would the light of it form gravitational...
  48. S

    Gravitational Lensing and Redshift

    hi there, I was just at a seminar in which the speaker was talking about using gravitational lensing to investigate galaxy clusters my question is pretty simple: is there any effect on the redshift of the image of an object which is "lensed" by the gravitational lensing phenomenon? I would...
  49. R

    Astrophysics Problem (gravitational lensing)

    Homework Statement I need some help with the following problem: http://img543.imageshack.us/img543/9630/lensq.jpg The Attempt at a Solution First I have tried to work out the radius of the Einstein ring: r_E = \sqrt{\frac{4GM}{c^2}}.\sqrt{\frac{D_1D_{1s}}{D_s}} =...
  50. S

    Gravitational lensing due to earth

    It is known that light from stars bend near surface of sun due to its mass. Similarly light will bend near Earth's surface (may be insignificant due to less mass). My question is that sunlight that strikes Earth's surface travels a straight path from sun or a curves near Earth's surface ?