Which Of The Following Is A Consequence Of Hubble’S Law?
- Marvin Harvey
Which of the following types of galaxies are reddest in color? Which types of galaxies have a clearly defined spheroidal component? Which types of galaxies have a clearly defined disk component? Compared to Spiral galaxies, elliptical galaxies are: How does a lenticular galaxy differ from a normal spiral galaxy? What is the major difference between an elliptical galaxy and a spiral galaxy? An elliptical galaxy lacks a disk component.
Most large galaxies in the Universe are: Which of the following types of galaxies are most commonly found in large clusters? Why are Cepheid variables important? Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as “standard candles” for distance measurements.
What is a standard candle? An object for which we are likely to know the true luminosity. Why is the Hyades cluster important for building up a catalog of the true luminosities of main-sequence stars? It is close enough to us that the distance to the cluster stars can be found by stellar parallax.
- How did Edwin Hubble measure the distance to the Andromeda Galaxy? He applied the period-luminosity relation to Cepheid variables.
- What two quantities did Edwin Hubble plot against each other to discover the expansion of the Universe? The recession velocity of a galaxy is directly proportional to its distance from us.
Which of the following is a consequence of Hubble’s law? The more distant a galaxy is from us, the faster it moves away from us. What makes white-dwarf supernovae good standard candles? They are very bright so they can be used to determine the distances to galaxies billions of light-years away, and they should all have approximately the same luminosity.
What is the Tully-Fisher relation? The faster a spiral galaxy’s rotation speed, the more luminous it is. Which of the following sequences lists the methods for determining distance in the correct order from nearest to farthest? Parallax, main-sequence fitting, Cepheid variables, Tully-Fisher relation, Hubble’s law.
Based on current estimates of the value of Hubble’s constant, how old is the Universe? Between 12 and 16 billion years old. Why can’t we see past the cosmological horizon? Beyond the cosmological horizon, we are looking back to a time before the Universe had formed.
Although it is difficult to tell from our vantage point inside the galaxy, astronomers suspect that the Milky Way is a barred spiral. Spiral galaxies have more gas, dust, and younger stars that elliptical galaxies do. Stars are continually forming in the halo of our galaxy today. Elliptical galaxies are more likely to be found in clusters than are spiral galaxies.
Our Sun belongs to the _ of the milky way Galaxy. The Globular cluster M13 belongs to the _ of the Milky Way Galaxy. A _ contains hot, ionized gas but very little cool gas or dust. The Milky Way is a _. The type of galaxy known as a _ was more common in the Universe 10 Billion years ago.
- Scientist investigating _ Study how the distribution of galaxies changes with time.
- Which kind of object is the best standard candle for measuring distances to extremely distant galaxies? Which types of galaxies have a clearly defined disk component? How does a Lenticular galaxy differ from a normal spiral galaxy? What is the major difference between an elliptical galaxy and a spiral galaxy? An elliptical galaxy lacks a disk component.
Most large galaxies in the Universe are:
What does Hubble’s law do?
Interpreting these diagrams – On the y-axis, you plot the velocity of the galaxy obtained from the spectrum. On the x-axis, you plot the distance to that galaxy, in this case obtained from Cepheids. If these two quantities (distance and velocity) had nothing to do with each other, then the diagram would look like what we call a “scatter plot.” That is, it would appear as a bunch of points randomly placed in different locations.
However, it is somewhat apparent in this case that you can draw a straight line through the points. What this means is that as the distance gets bigger, so does the velocity. In algebra class, you learned that the equation for a line that passes through the point (0,0) is: y = m x where y = the quantity plotted on the y-axis (velocity), x = the quantity plotted on the x-axis (distance), and m is the slope of the line.
For the specific case of this relationship, we usually write the equation this way: v = H 0 d H 0 is called the Hubble constant, It is the slope of the line that relates the distance of a galaxy to its velocity. If you know H 0 and if you can calculate the velocity, v, from the spectrum, then you can use this equation to calculate the distance, d, to that galaxy.
Let’s quickly review how we measure velocities for objects that are receding from us. The equation that you saw in Lesson 4 for the Doppler shift was: Δ λ / λ 0 = v r / c Where Δλ is the difference between the measured wavelength for a line in the spectrum of an object and the wavelength for that same line observed in the spectrum of an object at rest.
The other term on the left hand side, λ 0, is the wavelength of that line in the spectrum of an object at rest. For objects at large distances from Earth where the distance is determined using Hubble’s Law, we do not often refer to their recession velocities (e.g., “that galaxy has a velocity of 14,000 km/sec away from us”) or their distances in Mpc (e.g., “that galaxy is 247 Mpc from us”), instead, we simply refer to the object’s redshift, z,
The definition of z is that it is the left hand side of the Doppler shift equation: z = Δ λ / λ 0 For example, if you observe a galaxy with an H-alpha line at 680 nm, and you know the rest wavelength for that line is 656.3 nm, then its redshift is: z = ( 680 n m − 656.3 n m ) / 656.3 n m = 0.036 Hubble’s law, which says simply that a galaxy’s velocity (or as is sometimes plotted, its redshift) is directly proportional to its distance, also tells us something important about the state of the universe.
If the universe is static and unchanging, there should be no correlation between distance and velocity. However, if the universe is expanding, we expect a correlation between distance and velocity. The usual analogy used here is that of an explosion – the fragments of shrapnel produced are moving with a range of velocities, and the most distant objects from the source of the explosion have the largest velocities.
- Hubble’s Law only works for distant galaxies. For nearby galaxies (in the Local Group), stars inside the Milky Way, and for objects in our Solar System, the relationship between distance and velocity does not hold. The reason for the discrepancy for nearby galaxies is the “peculiar velocity” of the galaxy, that is, its real velocity through space that is unrelated to the expansion. For distant galaxies, their peculiar velocities are small enough that they still lie on or near the line for Hubble’s Law. For nearby galaxies, though, their peculiar velocity is larger than their velocity from the expansion, so their peculiar velocity dominates their total velocity, causing them to lie far from the line relating velocity to distance. For example, the galaxy M31 does not even show a redshift; it is blueshifted, showing that its peculiar velocity is pointed towards us, rather than away from us.
- Recall the concept of the “lookback time” for an object. For objects at very large distances from us, it is very common to see their distances referred to not in units like parsecs or light years, but in units of time. For example, astronomers will say, “The light from this galaxy was emitted when the universe was 10% of its present age, over 12 billion years ago.” We base these descriptions on the redshift of the galaxy and the lookback time.
You can consider Hubble’s Law to be the final rung in the distance ladder. If you know Hubble’s constant accurately, then you can calculate the distance to any galaxy in the Universe simply by measuring its velocity (which is reasonably easy to do for any galaxy for which you can observe its spectrum).
To calibrate Hubble’s constant, though, you need to be able to plot the distances for a number of galaxies as obtained using other methods. While that may seem like an easy statement to make, it was an incredibly difficult task to accomplish. For decades, astronomers have argued over the precise value of Hubble’s constant.
This measurement was, in fact, one of the major reasons for building and launching the Hubble Space Telescope. It spent years observing Cepheid variables in distant galaxies in order to measure Hubble’s constant as precisely as possible. The results were reported in 1999.
Is Hubble’s law a consequence of the expansion of the universe?
Hubble’s Exciting Universe: Measuring the Universe’s Expansion Rate Before the Hubble telescope was launched, there was a huge uncertainty over the expansion rate of the universe. This value is needed to calculate the age of the universe, estimate its evolution over billions of years, and understand the forces driving it.
At first, astronomers were delighted to narrow the expansion estimate to 10 percent accuracy. Now, with a lot of perseverance and precise observations, they are approaching one percent accuracy. In 1929, Edwin Hubble provided the first observational evidence for the universe having a finite age. Using the largest telescope of the time, he discovered that the more distant a galaxy is from us, the faster it appears to be receding into space.
This means that the universe is expanding uniformly in all directions. Hubble noted that light from faraway galaxies appeared to be stretched to longer wavelengths, or reddened, a phenomenon called redshift. By precisely determining the expansion rate, called the Hubble constant, the cosmic clock can be rewound and the age of the universe calculated.
- However, Edwin Hubble’s estimates of the expansion implied that the universe was younger than the age of the Earth and the Sun.
- Hubble, therefore, concluded that the redshift phenomenon was an unknown property of space and not a measurement of true space velocity.
- Astronomers later realized that redshift was a consequence of the expansion of space itself, as predicted in Einstein’s theory of special relativity.
However, the age estimate is only as reliable as the accuracy of the distance measurements. A precise value for the Hubble constant is a critical anchor point for calibrating other fundamental cosmological parameters for the universe. When the Hubble Space Telescope was launched, the uncertainly over the universe’s expansion rate was off by a factor of two. Early Hubble observations looked for cosmic milepost markers, the Cepheid variable stars, in ever-farther galaxies. The galaxy M100, located 56 million light-years away, is shown here. These data refined estimates for the expansion rate of the universe.
In 1994, astronomers began refining the Hubble constant by making precise distance measurements out to the Virgo cluster of galaxies, located 56 million light-years away. This allowed astronomers to begin refining distance measurements that are needed to calculate a more precise value for the Hubble constant.
They made observations of a class of star called Cepheid Variables. These stars go through rhythmic pulsations where they slightly rise and fall in brightness. The period of this oscillation is directly linked to the Cepheid’s intrinsic brightness. Once the star’s true brightness is known, astronomers can calculate a precise distance to it. This illustration shows the three steps astronomers used to measure the universe’s expansion rate to an unprecedented accuracy, reducing the total uncertainty to 2.3 percent. Astronomers made the measurements by streamlining and strengthening the construction of the cosmic distance ladder, which is used to measure accurate distances to galaxies near to and far from Earth.
A variety of other observing strategies have been applied to look at other milepost markers such as red giants star. A novel technique uses Hubble to look at where the gravity of a foreground galaxy acts like a giant magnifying lens, amplifying and distorting light from background objects such as quasars.
Astronomers next reliably deduce the distances from the galaxy to the quasar, and from Earth to the galaxy and to the background quasar. By comparing these distance values, the researchers measured the universe’s expansion rate that is completely independent of the “distance ladder” techniques.
- However, there is a troubling disagreement between the collective programs arriving at values for the Hubble constant in the nearby universe as compared with those of the early universe.
- The present rate of the universe’s expansion can be predicted from the cosmological model using measurements of the early universe, as encoded in the cosmic microwave background (CMB).
The CMB is a snapshot of the cosmos as it looked only 360,000 years after the big bang (as made by the Planck space observatory). The value from the Planck data is in disagreement with more direct measurements of the nearby universe made with Hubble and other observatories.
According to standard cosmological models, the values from the early and local universe should be the same. Because they are not, it presents a major challenge to theorists by implying that there is an incomplete understanding of the physical underpinnings of the universe. A century after the discovery of the expanding universe, the Hubble Space Telescope has allowed astronomers to enter the realm of precision astronomy, nailing down the expansion rate to extraordinary precision through several complementary observing strategies.
Future Hubble telescope observations may help settle the discrepancy between two independent approaches that measure the early universe versus the late universe’s expansion. This may open up a whole new frontier in our understanding of the evolving universe.
What is the implication of Hubble’s Law in astronomy?
Hubble’s law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther they are, the faster they are moving away from Earth.
The velocity of the galaxies has been determined by their redshift, a shift of the light they emit toward the red end of the visible spectrum, Hubble’s law is considered the first observational basis for the expansion of the universe, and today it serves as one of the pieces of evidence most often cited in support of the Big Bang model.
The motion of astronomical objects due solely to this expansion is known as the Hubble flow, It is described by the equation v = H 0 D, with H 0 the constant of proportionality—the Hubble constant —between the “proper distance” D to a galaxy, which can change over time, unlike the comoving distance, and its speed of separation v, i.e.
- The derivative of proper distance with respect to the cosmological time coordinate.
- See Comoving and proper distances § Uses of the proper distance for some discussion of the subtleties of this definition of “velocity”.) The Hubble constant is most frequently quoted in ( km / s )/ Mpc, thus giving the speed in km/s of a galaxy 1 megaparsec (3.09 × 10 19 km) away, and its value is about 70 (km/s)/Mpc,
However, the SI unit of H 0 is simply s −1, and the SI unit for the reciprocal of H 0 is simply the second. The reciprocal of H 0 is known as the Hubble time, The Hubble constant can also be interpreted as the relative rate of expansion. In this form H 0 = 7%/Gyr, meaning that at the current rate of expansion it takes a billion years for an unbound structure to grow by 7%.
Although widely attributed to Edwin Hubble, the notion of the universe expanding at a calculable rate was first derived from general relativity equations in 1922 by Alexander Friedmann, Friedmann published a set of equations, now known as the Friedmann equations, showing that the universe might be expanding, and presenting the expansion speed if that were the case.
Then Georges Lemaître, in a 1927 article, independently derived that the universe might be expanding, observed the proportionality between recessional velocity of, and distance to, distant bodies, and suggested an estimated value for the proportionality constant; this constant, when Edwin Hubble confirmed the existence of cosmic expansion and determined a more accurate value for it two years later, came to be known by his name as the Hubble constant.
What is Hubble’s law quizlet?
What does Hubble’s Law mean? A law of cosmology stating that the rate at which astronomical objects in the universe move apart from each other is proportional to their distance from each other.
What are two consequences of the universe’s expansion?
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Universe is Uniform on Large Scales: No Center to the Expansion in 3D Space
Like Kepler’s Laws, Hubble’s Law is an empirical law. Hubble discovered a relationship between two measurable properties of galaxies: their velocities and their distances. Given this relationship, though, it naturally leads to several questions. These questions are:
- What is the cause of this relationship?
- Why should more distant galaxies have larger velocities?
On the previous page, we attributed the velocities of galaxies and the relationship between their velocities and distances to an explosion. Because all of the pieces of debris from an explosion originated at the same spot, the more distant ones must be moving faster to have traveled the farthest in the same amount of time.
This is an acceptable analogy, but it is not perfect. It does, however, help us understand that the universe must be expanding. Our best interpretation of the relationship discovered by Hubble is that it implies that the space between galaxies is expanding. Let’s study this idea of an expanding Universe in a bit more detail.
If all objects are moving outward at a constant speed, the boundaries defined by the outermost objects must be continuously growing. To be more precise about the expansion of the universe, we again resort to analogies. The first is this: picture dots on a very long rubber band.
The dots are supposed to represent galaxies. If you pull on the rubber band, the distance between the dots will grow. If the initial distance between each dot is 1 cm (Dot B is 1 cm away from Dot A, Dot C is 2 cm away, and Dot D is 3 cm away) and you pull on the rubber band so that the dots are now 2 cm apart, then from Dot A, Dot B will be 2 cm away, Dot C will be 4 cm away, and Dot D will be 6 cm away.
Dot C will have moved twice as far from Dot A in the same amount of time as Dot B did, and Dot D will have moved three times as far from Dot A in the same amount of time as Dot B did. Therefore, from Dot A’s point of view, the more distant dots will appear to have moved faster than the closer dots (remember, the velocity of an object is the distance traveled divided by the time it takes to go that distance). Rubber band / dot analogy of the expanding universe. In an example initial state, galaxies appear as dots along a rubber band. The blue and yellow dots are equidistant from the point of origin, as are the white and pink dots, albeit in opposite directions. Rubber band / dot analogy of the expanding universe. The universe’s expansion, when doubled in size, causes all th dots to appear twice as far as they once were, from the perspective of the point of origin. This means that the white and pink dots have appeared to move much farther from the point of origin compared to the blue and yellow dots, in opposite directions from the point of origin.
- The galaxies are not really moving through space away from each other. Instead, what is happening is the space between them is expanding (just like the rubber band expanded, separating the dots fixed to it from each other). As the universe expands, the galaxies get farther from each other, and the apparent velocity will appear to be larger for the more distant galaxies.
- The Earth and the Milky Way are not special in seeing that all galaxies appear to be moving away from us. If we were on a different galaxy, we would also see all the other galaxies appear to be moving away from us because of this expansion.
The next two analogies are similar to the rubber band / dot analogy, but we are going to think in more dimensions, since we know that the galaxies are not restricted to be found along a one dimensional line. Instead of a line, picture the dough for raisin bread.
Inside the dough, all of the raisins are separated from each other. As the dough rises during baking, all of the raisins will move farther away from each other. Let’s say that the size of the dough doubles. The distance between all of the raisins will double, and just like the dots on the rubber band, the more distant raisins will appear to have moved faster.
This is represented well in the animated image from the NASA WMAP mission included below. Figure 10.6: Animated image showing the rising of a loaf of raisin bread dough. This animation contains the same idea as in Figure 10.5, but expanded to three spatial dimensions instead of one. The raisins in the dough are like the dots on the rubber band or galaxies in the Universe.
As the dough expands, the separation between the raisins increases, just like the separation between galaxies in our Universe. Both of the two analogies (rubber band and raisin bread) should allow you to picture that every galaxy (or dot or raisin) will see all other galaxies moving away if the space between them is expanding.
We use one more analogy to try to explain the mathematics of the expansion of the universe and to answer another common question that arises in cosmology:
Why can’t we observe the center of the expansion?
Picture a universe that consists only of the surface of a balloon. All of the galaxies and the stars in the galaxies are fixed onto the surface of the balloon. There is no way for the observers to perceive the region inside the balloon or the region outside the balloon, they are (and light is) constrained to travel only along the surface.
In this analogy, as the balloon inflates, the galaxies on the surface of the balloon will move farther away from each other. Just like with the rubber band and raisin analogies, if you measure the distance between the galaxies before and after the inflation of the balloon, you will be able to show that the more distant galaxies will appear to move faster, just like Hubble’s Law in our universe (and like the rubber band and raisin loaf experiments).
Again, every galaxy will observe the same effect, and no one galaxy is in a special location. If you ask where the center of the expansion is, it is inside the balloon. This means that no location on the surface of the balloon (the universe according to the residents on the surface of the balloon) can be identified as the “center” of the universe.
Where is the center of our universe?
The idea is that we live in a universe with three spatial dimensions that we can perceive, but that there exist “extra” dimensions (maybe one, maybe more than one) that contain the center of the expansion. Just like the two-dimensional beings that inhabit the surface of the balloon universe, we cannot observe the center of our universe.
We can tell that it is expanding, but we cannot identify a location in our 3D space that is the center of the expansion. Until this point, we have been describing the redshift of light as a Doppler shift. However, now that we understand the Universe to be expanding, we need to revise this description.
The way we understand the cosmological redshift of galaxies is as follows. Picture a photon emitted by a distant galaxy towards the Earth. That photon has a specific wavelength. However, during the trip between the distant galaxy and Earth, the space between that galaxy and Earth has expanded.
The expansion of space causes the wavelength of the photon to stretch, so when it arrives at Earth, it has a longer wavelength than when it left. Mathematically, this behaves exactly as if the photon was Doppler shifted. So, we interpret the galaxies as moving through space away from us. However, the proper interpretation is that the galaxies are at specific positions in space, and the space between them is expanding.
An animation illustrating the cosmological redshift using the balloon analogy for the expansion of space is below. Illustration of cosmological redshift using balloon analogy. In this animation, the wave drawn on the balloon represents the a wave of light with a specific wavelength.
- As the balloon expands, the wavelength increases.
- We believe this is how light behaves in the Universe.
- As the Universe expands, the distance between crests of the wave of light also expand, causing the wavelength to increase.
- Light with a longer wavelength is redder, so light appears redshifted because of the expansion.
Credit: Penn State Department of Astronomy & Astrophysics Does this mean that the Solar System is expanding? What about the Milky Way? Will Pluto get farther and farther from the Sun as the Universe expands? The answer is no, and it is a bit difficult to understand exactly why.
Consider again a stable Main Sequence star. We discussed how in order for a star to avoid collapse, the outward force of the radiation pressure created by the nuclear fusion in the core balanced the inward pull of gravity. We can consider all objects and systems of objects in the universe subject to the same kind of balance of forces.
The expansion of the universe can be thought of as a global force that is pulling on all objects. However, it is only strong on very large scales. At the scale of a galaxy, the gravitational force binding a galaxy together is much stronger than the “expansion force,” so the galaxy does not expand.
What was the impact of the Hubble telescope?
Hubble has helped scientists learn about our solar system. The telescope observes comets and planets. Hubble even discovered moons around Pluto that had not been seen before. The telescope has helped scientists understand how planets and galaxies form.
What conclusion can be made from Hubble’s data?
The Milky Way In 1912, made the remarkable discovery that the spectral lines of most galaxies are shifted to the red away from their rest wavelengths, implying that they are moving away from the Milky Way., working with the new 100-inch telescope on Mt.
- Wilson ten years later, made an even more stunning discovery.
- He plotted the recession velocities, V (determined from redshifted spectral lines), of galaxies against their estimated distances, D (determined by estimating the distance to Cepheid variable stars within each galaxy), and found a tight linear relationship.
The recession velocity of the galaxies tended to increase with their distance away from us (all galaxies were moving away from us, and the more distant ones were moving away more rapidly than those nearby)!
The constant of proportionality, H o, is now called the Hubble constant. The speed of a galaxy is typically measured in kilometers per second (km/sec), while the most common unit of for measuring the distance to nearby galaxies is the megaparsec (Mpc, one Mpc = 3.26 million light years).
There exist many galaxies beyond the Milky Way. They are receding, moving away from us. Their velocity of recession is proportional to their distance.
The correlation between velocity (redshift) and distance was fairly clear even in Hubble’s initial data (left), and modern observations (right) extend far further and have strengthened the conclusion.
|Hubble’s data, drawn from the nearby Universe||Modern data, covering a much larger region|
Hubble’s data indicated that galaxies which were located farther away from Earth were receding from Earth more quickly than those nearby. Because all galaxies are receding away from the Milky Way, it is tempting to assume that we occupy a preferred position at the center of the Universe.
A simple thought experiment will show us that this need not be the case. Let us imagine the Universe expanding in size, uniformly,; every part of the Universe expands in the same way. The fabric of space itself is expanding, and the galaxies are carried along like dandelions in the wind. What will this look like from Earth? We will pretend that the Universe is a straight line, with a galaxies spread out all along the line.
If the Universe were to expand uniformly, then the space between each pair of galaxies would eventually double. What would this look like?
|The distance between each galaxy increases, while the Milky Way appears to stay in one place. We see nearby galaxies moving only a little way (at a slower velocity), while more distant galaxies appear to travel a great distance (at a higher velocity).|
: The Milky Way
Which of the following is the best description for Hubble’s law?
Answer and Explanation: 1 – Hubble’s law states that the further away a galaxy is from planet Earth, the faster it moves away from us, and vice versa. The consequence of this. See full answer below.
What does Hubble’s law tell us about how galaxies are moving quizlet?
Hubble’s law (the straight-line fit to the data) predicts that a galaxy’s recession velocity is proportional to its distance from Earth. Hubble’s law therefore predicts that a galaxy twice as far away moves at twice the speed, a galaxy three times as far away moves at three times the speed, and so on.
What are the 3 outcomes of the universe?
There are 3 possible outcomes for the universe: (1) an open universe, in which expansion will never stop; (2) a closed universe, in which the expansion will stop and turn into contraction; and (3) a flat universe, in which the expansion will slow to a halt in an infinite amount of time.
What is the result of expansion of universe?
Effects of expansion on small scales – The expansion of space is sometimes described as a force that acts to push objects apart. Though this is an accurate description of the effect of the cosmological constant, it is not an accurate picture of the phenomenon of expansion in general. Animation of an expanding raisin bread model. As the bread doubles in width (depth and length), the distances between raisins also double. In addition to slowing the overall expansion, gravity causes local clumping of matter into stars and galaxies. Once objects are formed and bound by gravity, they “drop out” of the expansion and do not subsequently expand under the influence of the cosmological metric, there being no force compelling them to do so.
There is no difference between the inertial expansion of the universe and the inertial separation of nearby objects in a vacuum; the former is simply a large-scale extrapolation of the latter. Once objects are bound by gravity, they no longer recede from each other. Thus, the Andromeda galaxy, which is bound to the Milky Way galaxy, is actually falling towards us and is not expanding away.
Within the Local Group, the gravitational interactions have changed the inertial patterns of objects such that there is no cosmological expansion taking place. Once one goes beyond the Local Group, the inertial expansion is measurable, though systematic gravitational effects imply that larger and larger parts of space will eventually fall out of the ” Hubble Flow ” and end up as bound, non-expanding objects up to the scales of superclusters of galaxies.
- We can predict such future events by knowing the precise way the Hubble Flow is changing as well as the masses of the objects to which we are being gravitationally pulled.
- Currently, the Local Group is being gravitationally pulled towards either the Shapley Supercluster or the ” Great Attractor ” with which, if dark energy were not acting, we would eventually merge and no longer see expand away from us after such a time.
A consequence of metric expansion being due to inertial motion is that a uniform local “explosion” of matter into a vacuum can be locally described by the FLRW geometry, the same geometry that describes the expansion of the universe as a whole and was also the basis for the simpler Milne universe, which ignores the effects of gravity.
- In particular, general relativity predicts that light will move at the speed c with respect to the local motion of the exploding matter, a phenomenon analogous to frame dragging,
- The situation changes somewhat with the introduction of dark energy or a cosmological constant.
- A cosmological constant due to a vacuum energy density has the effect of adding a repulsive force between objects that is proportional (not inversely proportional) to distance.
Unlike inertia it actively “pulls” on objects that have clumped together under the influence of gravity, and even on individual atoms. However, this does not cause the objects to grow steadily or to disintegrate; unless they are very weakly bound, they will simply settle into an equilibrium state that is slightly (undetectably) larger than it would otherwise have been.
As the universe expands and the matter in it thins, the gravitational attraction decreases (since it is proportional to the density), while the cosmological repulsion increases; thus the ultimate fate of the ΛCDM universe is a near vacuum expanding at an ever-increasing rate under the influence of the cosmological constant.
However, the only locally visible effect of the accelerating expansion is the disappearance (by runaway redshift ) of distant galaxies; gravitationally bound objects like the Milky Way do not expand and the Andromeda galaxy is moving fast enough towards us that it will still merge with the Milky Way in 3 billion years time, and it is also likely that the merged supergalaxy that forms will eventually fall in and merge with the nearby Virgo Cluster,
Why is the Hubble constant important?
Learn more about breakthroughs pioneered at the University of Chicago The Hubble constant is one of the most important numbers in cosmology because it tells us how fast the universe is expanding, which can be used to determine the age of the universe and its history. It gets its name from UChicago alum Edwin Hubble, who was first to calculate the constant from his measurements of stars in 1929.
What was the problem with the Hubble Space Telescope and how is it solved?
The result was a mirror with an aberration one-50th the thickness of a human hair, in the grinding of the mirror. Replacing the mirror was not practical, so the best solution was to build replacement instruments that fixed the flaw much the same way a pair of glasses correct the vision of a near-sighted person.
What are the disadvantages of Hubble?
Disadvantages – There are some limitations with the Hubble Space Telescope when imaging the Moon due to its sensitivity to light and it cannot image areas in the direction of the Sun. They are exceptionally expensive to build and position in place. Maintenance is difficult.
Which main problem is being solved by the Hubble Space Telescope?
Hubble Space Telescope – The Hubble Space Telescope (HST) heads back toward its normal routine, after a week of servicing and upgrading by the STS-109 astronaut crew on board the Space Shuttle Columbia in March 2002. Credit: NASA The Hubble Space Telescope was launched in 1990, taken to space in the cargo bay of the space shuttle Discovery.
- Its main purpose was to figure out a distance scale of the Universe (how big it is) and where the elements present in space came from.
- That is what interests scientists.
- But the pictures it takes! That’s what intrigues most of humanity,
- But the HST did not just happen.
- Centuries of work by curious astronomers led to its conception.
As Isaac Newton said, “If I can see farther, it is because I am standing on the shoulders of giants.” The Hubble Space Telescope can make the same claim. Here is a short history of events and inventors that led to its development,
How does an expanding universe explain the Hubble law?
It indicates a constant expansion of the cosmos where, like in an expanding raisin cake that swells in size, galaxies, like the raisins, recede from each other at a constant speed per unit distance; thus, more distant objects move faster than nearby ones.
What causes Hubble’s law?
2. Describe the principle of Hubble law redshift. – Ans. Hubble law redshift is a phrase used to describe the phenomenon whereby electromagnetic radiation causes the wavelength of an object to increase. Blueshift is also the opposite of redshift when energy levels rise due to shorter wavelengths and is referred to as negative redshift.
- The Doppler effect is the motion of objects in space, either towards or apart from one another.
- The powerful gravitational field present in the universe is responsible for gravitational redshift.
- Cosmological redshift is an increase in space that causes objects to separate from one another without changing their positions.
How did Hubble prove the universe was expanding?
Hubble finds proof that the universe is expanding 1929 The two keys to Edwin Hubble ‘s breakthrough discovery were forged by others in the 1910s. The first key, the period-luminosity scale discovered by Henrietta Leavitt, allowed astronomers to calculate the distance to variable stars from Earth.
- Hubble had already used this knowledge in his 1924 discovery that the Andromeda nebula, containing a variable star, was more than 900,000 light years from Earth – way beyond our own galaxy – a surprise to everyone at the time.
- With this scale and other tools, Hubble had found and measured 23 other galaxies out to a distance of about 20 million light years.
The second key was the work of Vesto Slipher, who had investigated the spiral nebulae, before Hubble’s Andromeda discovery. These bodies emit light which can be split into its component colors on a spectrum. Lines then appear in this spectrum in particular patterns depending on the elements in the light source.
Yet if the light source is moving away, the lines are shifted into the red part of the spectrum. Analyzing the light from the nebulae, Slipher found that nearly all of them appeared to be moving away from Earth. Slipher knew that a shift toward red suggested the body was moving rapidly away from the observer.
But he had no way to measure the distances to these reddish bodies. Hubble’s brilliant observation was that the red shift of galaxies was directly proportional to the distance of the galaxy from earth. That meant that things farther away from Earth were moving away faster.
- In other words, the universe must be expanding.
- He announced his finding in 1929.
- The ratio of distance to redshift was 170 kilometers/second per light year of distance, now called Hubble’s constant.
- The numbers were not exactly right, and refinements in measuring techniques and technology have changed all of Hubble’s early figures.
But not the basic principle. He himself kept working on the problem and collecting data throughout his career. Some view Hubble’s discovery as the most important event in astronomy in the century. It made the most basic change in our view of the world since Copernicus 400 years ago.