How do astronomers observing distant galaxies talk about looking backward in time?
The speed of light is not infinite. Light takes time to travel from distant galaxies to our eyes here on Earth. If a galaxy is 1 billion light years away, it has taken 1 billion years for the light emitted by said galaxy to reach us here, so (obviously) we are seeing the light emitted 1 billion years ago. In a sense, we are seeing 1 billion years into the past at the light emitted by that galaxy.
5 people found this useful
Because they are so far away that the light is too dim and diffuse to make out individual stars or groups of stars. With a high-powered telescope, you can distinguish other ga…laxies from the closer objects in our own Milky Way galaxy, whose stars are all around us.
They map the galaxy with radio waves
At the galaxy.
because they are trying to find possible life or inhabitable planets. There are also some that just love the sky
The light of those distant stars and galaxies took an appreciable period of time in getting here to be detected in our telescopes. So when we look at distant galaxies, we're s…eeing the light that those galaxies emitted thousands, millions or BILLIONS of years ago. So it almost is like looking back in time.
Millimeter wavelengths are short frequency radio waves astronomers use because they can see gases and other phenomena not visible in visible light. MM wavelengths are usually …used where the air is dry so water vapor can't scatter the waves.
There are many stars in each stage of development, so the obvious assumption is that they represent similar stars, with similar stages, except that they began their existence …at different times. Imagine you knew nothing of people. You were then given millions of pictures of people in varying states of aging. Different people, each one in a different stage of development. Would you be able to figure out that the tiny ones were young ones and that the wrinkly ones were old ones? Maybe. It is in that way that studying the pictures of the distant galaxies, and for that matter, stars, that human beings can guess at how these inter-stellar bodies age.
That the further a galaxy was from us, the faster it was moving away.
Picture this: You and your best friend are in constant communication, and your friend constantly informs you of every little thing that happens in her life. But the method o…f communication is "snail mail", which usually takes two or three days in transit. So, every time you read a line that says "my brother just walked in the door, and he's taking a beer out of the fridge", you know that it's not really happening right now, but it actually happened 2 or 3 days ago. That's the situation when you look into the sky, because light takes time to travel from place to place. Look at the moon, and you see light that left the moon 1.3 seconds ago. Look at the sun, and you see light that left the sun 8.3 minutes ago. Look at the nearest star outside the solar system, and you see light that left the star 4.4 years ago. And so it goes. You never see anything in the sky that's happening right now. It's always something that happened some time ago. And of you're looking at stars, you're seeing things that happened years ago.
Explain why looking at distant galaxies gives scientists an idea about how galaxies change over time?
Light from distant galaxies took billions of years to reach us. Therefore, we are looking at the far past of the Universe.
What can astronomers conclude based on the observed red shifts in the spectral lines of distant galaxies?
The strongest consensus (near unanimous of the astronomical community is that the redshifts of distant galaxies indicate that all distant galaxies are receding from us. This… recession is currently the only known mechanism for redshifting light. Take this inference, that all galaxies are receding and you are led to the idea that the universe is expanding, a phenomena described by Hubble's Law. This is a central tenet to the Big Bang Theory.. I will include the counterpoint originally described below, but I will point out that the papers cited are very old, and a huge number of corroborating observations and predictions of the big bang have occurred since then. The conclusion that the Universe is expanding is a wrong conclusion. Alan Sandage talks about Hubble's position at the related link below. To the very end of his writings he maintained this position, favouring (or at the very least keeping open) the model where no true expansion exists, and therefore that the redshift "represents a hitherto unrecognized principle of nature". This viewpoint is emphasized (a) in The Realm of the Nebulae , (b) in his reply (Hubble 1937a) to the criticisms of the 1936 papers by Eddington and by McVittie, and (c) in his 1937 Rhodes Lectures published as The Observational Approach to Cosmology (Hubble 1937b). It also persists in his last published scientific paper which is an account of his Darwin Lecture (Hubble 1953). .
When astronomers observe a supernova explosion in a distant galaxy they see a sudden simultaneous rise in visible light and other forms of electromagnetic radiation?
Actually before the rise of visible light there is a surge in neutrinos that can give a warning of a super-nova by as much as five days. Then comes the light flash in all for…ms of electromagnetic radiation (including visible light).
Because in the spring, the night sky is pointed out of the Milky Way and therefore it is easier to see distant galaxies.
In Waves Vibrations and Oscillations
When astronomers study distant galaxies they notice changes to the waves they observe describe the change to the waves they observe?
Because the universe as a whole is expanding, distant galaxies are moving away from us. As a result, electromagnetic waves emitted by those galaxies experience what is known a…s a red shift. Their wavelengths get longer.
In Red Shift
How did 1920's astronomer Edwin Hubble explain his observations that all light from distant galaxies exhibits the red-shift Doppler effect?
He concluded that all of space was expanding. Answer2: Hubble did not conclude that all space was expanding! Hubble concluded that he did not know what the redshift was.… 1. "Red shifts represent Doppler effects, physical recession of the nebulae, or the action of some hitherto unrecognized principle in nature." 2. If the nebulae are stationary, the law of red shifts is sensibly linear ; red shifts are a constant multiple of distances. In other words, each unit of light path contributes the same amount of red shift. 3. On the other hand, if the nebulae are receding, and the dimming factors are applied, the scale of distances is altered, and the law of red shifts is no longer linear. The rate of expansion increases more and more rapidly with distance. The significance of this result becomes clear when the picture is reversed. Light that reaches us today left the distant nebulae far back in the dim past - hundreds of millions of years ago. When we say that the rate of expansion increases with distance, we are saying that long ago, the universe was expanding much faster than it is today ; that, for the last several million years at least, the rate of expansion has been slowing down. Therefore, the so-called "age of the universe," the time interval since the expansion began, is much shorter than the 1800 million years suggested by a linear law of red shifts. If the measures are reliable, the interval would be less than 1000 million years - a fraction of the age of the earth and comparable with the history of life on the earth. The nature of the expansion is permissible and, in fact, specifies certain types of possible worlds. But the time scale is probably not acceptable. Either the measures are unreliable or red shifts do not represent expansion of the universe. Hubble admits to not knowing what the red shift is, he considers it a. Doppler effects, b. physical recession of the nebulae, or c. the action of some hitherto unrecognized principle in nature. The answer is c. the hitherto unrecognized principle in nature. The short answer is the red shift is the inverse of the refreaction coefficient, v/c= 1/n. The red shift is derived from the so-called "dark Energy", cP = cmV. Current Theories do not account for this because they do not recognize vector energy cP and Quaternion energy, W = -vh/l + cP = -vp + cP The red shift comes from the Continuity Condition where the centripetal force vp/r is balanced by the centrifugal force cDEL.P= -cp/r cos(P) thud vp/r=cp/r cos(P) gives v/c=cos(P) = 1/n This is the hitherto unrecognized prijnciple of nature, the Divergence of the vector energy produces the anti-gravity force (centrifugal ) that prevents the gravitational collapse, the earth from falling into the sun and the electrons from falling into the nucleus. Newton and Einstein did not consider the energy, cP, associated with momentum P, that is the "Dark Energy". This energy cP is the particel energy with different velocities v=(GM/r)^.5 for mass; v=Alpha Z c for electrons; and v=c for photons. Mass n= c/v; electrons n= alpha Z; and photons n=1.
Astronomers have difficulty looking at distant stars because theyare just so far away. They use special telescopes but they can'tsee everything.