Redshift and brightness may be less intuitive than speed and distance, but at least they’re precisely defined. And they’re also very useful. Just like an amateur cook might be able to figure out a restaurant's raisin-bread recipe by baking his own bread over and over again and tasting the final results, astronomers can figure out the expansion of the "raisin bread" universe by generating theoretical models for the relationship between redshift and brightness under different scenarios (in particular, by allowing the Hubble constant to evolve with time in different ways) and throwing away the models that don’t fit the observed data. The results obtained over the past decade very clearly favor models in which the individual galaxies are speeding up—in other words, an accelerating universe.
Subscription Center
See what we're tweeting about
16 Comments
Add CommentI have a different conceptual principle to offer. One that contradicts the very idea of there being a Hubble constant. It explains why the measure changes with different sample groups and why when later revisiting sample groups the measure modestly changes. It also makes a modification to the principle factors governing Hubble law.
Reply | Report Abuse | Link to thisWhy can we not see beyond those last galaxies? Is light speed too slow or is expansion to great? hdc
Reply | Report Abuse | Link to thisDear Sirs:In the search for the stars mathematical constants bother me as much as constant or dogmatic and rigid thoughts or ways of thinking or the stretching of the imagination with mathematical possibilities and probalities.. We all each have our peculiar ways of thinking that are never exactly the same between any two humans. Whether distant, far, invisible, a universal truth does not have a number attached to it..the distance to a point from the back of ones head is not the same as the distance from the front of the head where the eyes can see. No living thing can see, and hence consider for his immediate living tasks, a whole 360 degrees. To do so could have no more a meaning than to assign a fixed age, or size to all humans. The lending of constant mathematical values in physics in correspondence assigns to space a description other than what ones knows-and has no meaning, less to also add in definition that incoherencies without a knowable definition can exist and also co- exist with normal two dimensional space that is perceived. This might be acceptable as experiment of the intellect, but is not suited as a tool to create heating furnaces, or stock kitchen cupboards, or nuture public perspective/the young, anymore than one would elect one single politician to sire all the newborn on the earth. Getting down to earth in such a case one not know one person from the other, and less than the actual projected remains of the low and lecherous battle for the earths resources. Mutual anonominity, in large scale group activities is universally a prerequisite for a victimization of the foreign. The teaching of the existence of such physcial constants, especially in the education of the young, in the absence of an understanding of the actual meaning as no more than pen and paper experiment; the pursuit of anonymous physical constants has no exact corresponding difference in meaning/in psycho lingual meaning, consequential action, than as a victimization of our own living spaces. Some politicians might not balk to be the stant fathers of tomorrow, but with an added enlightenment, might object to be the con-stant fathers of all tomorrow. http://www.marvinekirsh.com http://www.authorsden.com/marvinelikirsh
Reply | Report Abuse | Link to thisEvery good answer raises new questions. The energy of a photon is given by it's frequency multiplied by Planck's constant. If the light is being "red shifted" the energy in each photon must be reduced. What happens to this energy?
Reply | Report Abuse | Link to thisWhile I might be wrong, the answer is in the blog I put up today.
Reply | Report Abuse | Link to thisIt explained the nature of red-shift without spacial Expansion theory.
The energy is lost to to spacial gravities.
Please let me know if the blogged idea is in agreement with you.
w
Reply | Report Abuse | Link to thisWhich type would be least harmful to an organism why?
Reply | Report Abuse | Link to thisa) substitution versus inversion?
b) deletion vs. substitution?
What if the shape of the universe was an expanding sphere similar to a planetary nebula created from the big bang? All of the galaxies we see are contained along the thick surface of the sphere. As the sphere grows the surface expands exponentially making it appear to be accelerating.
Reply | Report Abuse | Link to thisWhat if the light from type Ia supernovae are being obsured to different degrees by dust and other space debris? What if what we think we observe is actually a mirage like the shimmer of hot asphalt in the distance?What if the laws of physics have changed over the course of time. A very simple example: I cannot swim through solid ice but I can swim through liquid water. The substance is the same, but it has changed due to time and temperature. The medium through which the light travels must remain the same over billions of light years. And we need to be sure that what we observe is reality and not illusion. There are so many variables to take into account that any theory or conclusion whether through observation or modeling is as good as anyone elses guess.
Reply | Report Abuse | Link to thisMost distant visible quasars are said to have an age of less than 1Gy compared to age of Universe of 14Gy. So how is it that if these quasars emitted light when they were at a distance of less than 1GLY it has taken this light about 13Gy to reach us?
Reply | Report Abuse | Link to thisBecause of the expanding universe, the Super clusters are moving away from other Super clusters, and Super clusters are composed of galaxies with super massive black holes at their cores, my question is about the mass of the super massive black holes at the cores, does their relativistic mass increase relative to each other or remain the same, because they are regressing relative to each other?
Reply | Report Abuse | Link to thisI DON'T THINK HE ANSWERED THE QUESTION YOU WERE LOOKING FOR.ASK THE QUESTION THIS WAY.
Reply | Report Abuse | Link to thisTHE LIGHT FROM THE ANDROMEDA GALAXY IS 200 MILLION LIGHT YEARS OLD ,WHEN WE LOOK AT THAT GALAXY. THAT GALAXY IS MOVING DIRECTLY TOWARDS ARE GALAXY. SO ANDROMEDA HAS HAD 200 MILLION YEARS TO MOVE CLOSER TO US FROM WHAT WE ARE OBSERVEING. FOR ALL WE KNOW ANDROMEDA COULD BE CRASHING INTO ARE GALAXY RIGHT NOW, AND WE COULD NOT SEE IT. IS THIS OBSERVATION TRUE OR NOT?
IF THE ANDROMEDA GALAXY IS SAID TO BE 200 MILLION LIGHT YEARS FROM US AS WE OBSERVE IT, AND THE GALAXY IS MOVING TOWARDS ARE GALAXY. DOES THAT MEAN THAT ANDROMEDA HAS HAD 200 MILLION YEARS TO MOVE CLOSER TO US AND WE CAN'T SEE IT BECAUSE WERE SEEING THE LIGHT FROM IT , FROM 200 MILLION YEARS AGO. FOR ALL WE KNOW ANDROMEDA COULD BE CRASHING INTO ARE GALAXY RIGHT NOW?
Reply | Report Abuse | Link to this"Imagine a gigantic blob of dough with a bunch of raisins embedded throughout; the dough represents space, and the raisins represent the galaxies. Now, if someone puts the dough in the oven, it will expand or, more accurately, stretch, keeping the same proportions as it had before, but with all the distances between raisins getting bigger as time goes on.
Reply | Report Abuse | Link to this"
Are the raisins expanding also?
Space expands between galaxies.
What within galaxies? Between planets? Between electron and proton in hydrogen atom? I guess the answer is no, but is this consistent? How can space expand on large scale but not on small scale?
The Andromeda galaxy is estimated to be at 772 +/- 44 kpc
Reply | Report Abuse | Link to this1 kpc = 1 kiloParsec = 3262 ly (light-year)
772 kpc = 2518264 ly = 2.5 Million ly
" ... the Andromeda Galaxy and the Milky Way are approaching one another at a speed of 100 to 140 kilometers per second (62–87 miles/sec.).[18] The impact is predicted to occur in about 2.5 billion years."
http://en.wikipedia.org/wiki/Andromeda_galaxy#cite_note-Ribas2005-3
http://www.journals.uchicago.edu/doi/abs/10.1086/499161
Now, surely it will happen before that since as Amdromeda gets closer it gets "sooner".
Reply | Report Abuse | Link to this